The real reason people are breaking rods

[LizardKing]

Originally Posted by ptperformance Because we have tested results, we are working on a fix. The other guy, well he has questions and answers with nothing to provide to the community for a fix or solution to the problem. We on the other had are trying for you, the community to find a fix. They know more than me but have yet to confrim how many motors they have torn down or how many motors they have personally blown. They will not commit to any first hand experience, yet they have all the answers. Does that about clear it up? We have the experience, we have blown motors, we are working on a fix. This means we have more first hand knowledge about the issue at hand. Not only this but as Lex stated, there are no other cars that make the amount of TQ (like the SRT, LOL) at the lower RPM bands like the Mazda, yet Lex clearly stated that the rods were just as strong as the SRT's. I proved that point "WRONG" and they are simply ignoring that I made that obvious to them. They choose to avoid the challenges and cover it up with "I did this and it worked on my car". Well congrats to it working on one fucking car, here is your cookie. Now go out and prove that it works on 100's of these cars and people might believe what you have to say, vs blowing smoke to all the members of this site that are taking what they are saying as truth.

Do you treat all your customers like they are dumb?

Dude, really? I don't care if your catch can gives me a BJ and washes my dishes. You sir are an ignorant bastard.

There is some great logical information in this thread. If you actually read it an understood it, you might even be scratching your head and adding it to your information to help create this goddess like catch can. But no. The only way you even recognize the thoughts of another human being is if they stroke your sack and lick your balls before they open their mouth. Lex refuses to do that and I applaud him. Get real. Grow up.

And WTF? It takes 12 months to test a catch can? Until you decided that you would start making money on MS3s again we haven't heard a peep. Well, unless you count your girlfriend trying to sell us BC coils. Oh wait I forgot the "tested" fuel pump internals putting out 50psi. Oh.. no no.. I mean the injector seals that don't seal. Those were some mighty fine fixes.

Shit. I don't know Lex but he is one smart MFer that has pretty good frigging "theories." Anyone that has spent any time reading his posts could tell you that. By tearing him down you just prove how ignorant you are.

I used to think you were smart but the more I read your crap the more I realize that you must have one tiny pecker. Your BJ giving, dish washing, vapor ware catch can suck my left nut. Just on principle alone it won't end up in my vehicle.


I am real fucking sorry I pointed this thread out. Go back to your thread and sell shit over there.

[ptperformance]

Originally Posted by djuosnteisn lulz at blowing alot of motors being a sign of skill. Wow John, just wow. Good luck in life hombre. Thanks for showing us all the light, and how a motor works. I believe anything you say. Also, john. If the pooling oil was such a commonality, why the hell did you design a freeze plug water injection?

As far as blowing motor being a skill, at least I have the first hand experience with blown motors... do you?

See how acting childish gets us nowhere. So are we going to answer the questions or keep justifiying and avoiding.

250 psi and 1/4 of oil, you tell me who is going to win that battle, LOL.

guys, WTF breaks my dam rods

[ptperformance]

Originally Posted by LizardKing Do you treat all your customers like they are dumb? Dude, really? I don't care if your catch can gives me a BJ and washes my dishes. You sir are an ignorant bastard. There is some great logical information in this thread. If you actually read it an understood it you might even been scratching your head and adding it to your information to help create this goddess like catch can. But no. The only way you even recognize the thoughts of another human being is if they stroke your sack and lick your balls before they open their mouth. Lex refuses to do that and I applaud him. Get real. Grow up. And WTF? It takes 12 months to test a catch can? Until you decided that you would start making money on MS3s again we haven't heard a peep. Well, unless you count your girlfriend trying to sell us BC coils. Oh wait I forgot the "tested" fuel pump internals putting out 50psi. Oh.. no no.. I mean the injector seals that don't seal. Those were some mighty fine fixes. Shit. I don't know Lex but he is one smart MFer that has pretty good frigging "theories." Anyone that has spent any time reading his posts could tell you that. By tearing him down you just prove how ignorant you are. I used to think you were smart but the more I read your crap the more I realize that you must have one tiny pecker. Your BJ giving, dish washing, vapor ware catch can suck my left nut. Just on principle alone it won't end up in my vehicle. I am real fucking sorry I pointed this thread out. Go back to your thread and sell shit over there.

There is no such think as a dumb question/customer, only a dumb answer.

I am ignorant, please tell me why. I came in here with a legitimate claim/proof to debate the findings of Lex (see about 30 posts back). I posted my results and what I found, and those posts have went un-answered with zero to challenge what I said. And I am the ignorant one out of all this?

I need to grow up, I am not the one who is refusing to answer questions, I am not the one taking other platforms and making them fit my needs for this therory, I am not the one that keeps on changing the topic and moving over to the failed parts that are sold by me. At what point did you miss all of that? I came in here to show that Lex was in fact wrong, he has yet to admit that he might have made a mistake or that his original post may not be correct. At the bare minumum he didn't take the time to even look and see if a SRT4 could make more TQ down low than the DISI motor. So I need to grow up, because I came in here showing where the thread poster was wrong? How does this help the community? How is it OK by your standards to have a person stating incorrect information and when someone challenges it (poliet at first, then finally getting nasty because they have avoided it) the challenger becomes the ass? What?

Hey, if you guys want therories, I have a bunch that I can offer up. Last time I checked you guys wanted solutions. Please tell me what one you want and I will get started or continue working on either one.

Last, you tell me that I need to grow up yet make a verbal attack against me... seriously . Kind of calling the kettle black, hey.

Originally Posted by 18psiWhiteMS3 guys, WTF breaks my dam rods

The TQ from my little pecker .

Originally Posted by ptperformance The TQ from my little pecker .

Does your pecker resemble this?

[LizardKing]

Originally Posted by ptperformance There is no such think as a dumb question/customer, only a dumb answer. I am ignorant, please tell me why. I came in here with a legitimate claim/proof to debate the findings of Lex (see about 30 posts back). I posted my results and what I found, and those posts have went un-answered with zero to challenge what I said. And I am the ignorant one out of all this? I need to grow up, I am not the one who is refusing to answer questions, I am not the one taking other platforms and making them fit my needs for this therory, I am not the one that keeps on changing the topic and moving over to the failed parts that are sold by me. At what point did you miss all of that? I came in here to show that Lex was in fact wrong, he has yet to admit that he might have made a mistake or that his original post may not be correct. At the bare minumum he didn't take the time to even look and see if a SRT4 could make more TQ down low than the DISI motor. So I need to grow up, because I came in here showing where the thread poster was wrong? How does this help the community? How is it OK by your standards to have a person stating incorrect information and when someone challenges it (poliet at first, then finally getting nasty because they have avoided it) the challenger becomes the ass? What? Hey, if you guys want therories, I have a bunch that I can offer up. Last time I checked you guys wanted solutions. Please tell me what one you want and I will get started or continue working on either one. Last, you tell me that I need to grow up yet make a verbal attack against me... seriously . Kind of calling the kettle black, hey. The TQ from my little pecker .

Huh?? What?? I can't hear you.

[ptperformance]

Originally Posted by 18psiWhiteMS3 Does your pecker resemble this?

Only when hard

Originally Posted by LizardKing Huh?? What?? I can't hear you.

Whoosh, is this you?

[Speedie6]

[djuosnteisn]

Originally Posted by ptperformance As far as blowing motor being a skill, at least I have the first hand experience with blown motors... do you? And that's why i'd never let you lay a hand on my motor See how acting childish gets us nowhere. So are we going to answer the questions or keep justifiying and avoiding. I think the real answer is plenty justified, now most of this thread has been dedicated to showing the world your true colors. Your really surprising the hell out of me hahaha. Remind me of Randy a lil bit. 250 psi and 1/4 of oil, you tell me who is going to win that battle, LOL. wtf? 250psi vs 1/4 of oil? Um, i have no clue who would win.

answered your questions again.

fucking eh, i'm getting tired of this. Alcohol helps, but not enough i don't think...

[SSinstaller]

Originally Posted by ptperformance 250 psi and 1/4 of oil, you tell me who is going to win that battle, LOL.

Netflix...

That just popped into my head.

[ptperformance]

Originally Posted by djuosnteisn answered your questions again. fucking eh, i'm getting tired of this. Alcohol helps, but not enough i don't think...

Your getting tired of it, when the hell are you or Lex going to address the SRT4 motor and dyno that I posted up? Keep avoiding it, but eventually someone is going to catch on and realize that someone made the wrong assumption or didn't take the time to research what the other motor can or cannot do.

With that said:

And that's why i'd never let you lay a hand on my motor

So your saying that blowing motors is a bad think, you want some race shop or builder with a 100% success rate to build yours? Good luck with that. You learn by your mistakes, you learn by pushing the limits of the stock parts, then moving up to forged.

I think the real answer is plenty justified, now most of this thread has been dedicated to showing the world your true colors. Your really surprising the hell out of me hahaha. Remind me of Randy a lil bit.

My true colors? I am the only one that has the balls to speak up and post where wrong information has been stated, and you still refuse to reply to that SRT4 dyno/motor information. I am surprising you, but I am starting to think that people may, just may start to realize that you guys have not been doing proper testing, but hey, I am the guy that blows up motors, and has a list of parts a mile long that fail all the time LOL!

Um, i have no clue who would win.

If you have no idea as to who would win, then why ask the question about our WI nozzle location. I am sure that you have a point you wanted to make, not sure if you did, but... the 250 psi of water pressure is going to win vs a 1/4 thick layer of oil in the bottom of your intake manifold (yes we tested this).

After its all done and said, I hope that you guys keep telling people that a "tune" will keep a motor from blowing. I know of several tuned cars with no knock that have blown after a long road trip. You only have to look into the blown motor resource thread to figure that one out.

[Lex]

What about the SRT4 dyno? What do you want to know about it? Made some big power on stock internals?? OK. So what? Perhaps the lower compression allows for a higher detonation threshold. Perhaps it made a couple of pulls and blew. Perhaps it didn't have a failing fuel pump. Perhaps the internals are strong. Perhaps it was built on the 3rd Monday of the month. What does that have to do with the DISI?

The beginning of this thread gets at the fact that high torque, low rpm, detonation, contribute to the fatigue of the DISI rods.

Simple as that. Hard to get?

[bf360]

Originally Posted by Lex What about the SRT4 dyno? What do you want to know about it? Made some big power on stock internals?? OK. So what? Perhaps the lower compression allows for a higher detonation threshold. Perhaps it made a couple of pulls and blew. Perhaps it didn't have a failing fuel pump. Perhaps the internals are strong. Perhaps it was built on the 3rd Monday of the month. What does that have to do with the DISI? The beginning of this thread gets at the fact that high torque, low rpm, detonation, contribute to the fatigue of the DISI rods. Simple as that. Hard to get?

The point that he is showing you is that you constantly said how no motor made the tq the ms motor does at such low rpms, but when in reality there are plenty of examples of other cars.

Personally theres things i like about both Lex and John, and things i really dont like. You both have some decent points, but few points id like to make.

John the idea of seeing oil in a cylinder after a motor is blown does not hold ground, once a rod is bent the pistons rings are most likely compromised and oil could be entering from there, and it may appear to be hydrolock but the oil entered after the bent rod not before.

Lex, we have seen these motors take a lot of abuse and some cars have gotten close to 400wtq out of it, i do not think the motors are inherently weak, but constant knock is definitely a major problem.

One thing we have known for a very long time, the car runs a shit load of timing at p-t and runs lean for gas mileage, it runs very close to the edge.

[starscream]

Guy 1: My penis is bigger then your penis
Guy 2: But we both have penises
Guy 1: oh...my penis is bigger then your penis still
Guy 2: /facepalm...

Air out your laundry in another thread, this thread had some good information and is starting to go downhill with all this argumenting. Some of your are reasoning by analogy which really doesnt work all that well, when we more need impirical information.

Fuck IT! Bitch slap the car, drive it like you stole it, fuck the girl next door and call it a day ...and sing kum-bye-ya...

[ptperformance]

Originally Posted by bf360 The point that he is showing you is that you constantly said how no motor made the tq the ms motor does at such low rpms, but when in reality there are plenty of examples of other cars. Personally theres things i like about both Lex and John, and things i really dont like. You both have some decent points, but few points id like to make. John the idea of seeing oil in a cylinder after a motor is blown does not hold ground, once a rod is bent the pistons rings are most likely compromised and oil could be entering from there, and it may appear to be hydrolock but the oil entered after the bent rod not before. Lex, we have seen these motors take a lot of abuse and some cars have gotten close to 400wtq out of it, i do not think the motors are inherently weak, but constant knock is definitely a major problem. One thing we have known for a very long time, the car runs a shit load of timing at p-t and runs lean for gas mileage, it runs very close to the edge.

Thanks and on this note I will leave the thread.

I think that its safe to say that the oiling system is part of the problem and when we have a working solution for the car with proven results we will post them.

DI motors can run lean and they can get away with very high timing at p-t, however if the get to out of hand and boost starts to show up I can see this being a problem. Anyone would have to admit that the blown motor resource thread does show a lot of motors blowing after a long drive, could it be a problem, I don't know but I can only talk from my first hand experiences and the motors we have personally blown or torn down form a blow. They all look to have some sort of oiling issues that contributed to the motor when it let go. I have seen my fair share of other motors that have blown and none of them have the oil build up in the exhaust, intake and cyl head like the DISI motors.

I will applogize for shitting on the thread, but all I wanted was a simple answer to my question 2 pages ago, that is all.

[darth vader]

I don't usually get involved in threads like this since, who gives a fuck what I have to say, anyway?

I'll say, I have PtP internals on my car. I bought them because I liked the design that retained the stock button. I've had 0 issues with them and they cured my high rev missing and added 1000 psi to my working DI pressure over 5000 rpm.

I have the pill too. I didn't smoke before catless and I don't smoke now. I've had no dipstick or PCV issues with my car. I can't directly credit the pill but it certainly didn't harm anything. I did it because it was cheap and because I believe prevention is the best cure. Once oil gets past the shaft seal and cokes hard, it's gonna leak like a lady of the evening with a yeast infection.

I am glad this stuff worked on MY car, because that's the one I care about and am paying for.

On the other hand, disputes like this inevitably reflect badly on the participants but, particularly so on someone with a vested financial interest in the outcome.

[Ziggo]

Forgive the "noob" question, but where\when\why was the decision made that high torque at low RPM was worse than the same torque at high RPM from a force standpoint? I am thinking through my dynamics and I cannot come up with a good explanation for this.

High torque at low RPM is murder for our fuel pump, and there might be other reasons why, but I am inclined to believe the the high torque\low RPM failure is more of a symptom than a cause. Torque is a force, and independent of speed. 315ft-lbs at 2000RPM puts the same force on the rod as 315ft-lbs at 5000RPM.

[darth vader]

Easy-peasy explanation, dude: It's all a function of time under load. At low rpm, the torque stress is spread over a much longer span of time thus, the load on the components is way higher.

It's what people mean when they say, don't "lug the motor". There's a bit more to it than I've outlined above but, that's the main bit.

[Click Here]

Originally Posted by Ziggo High torque at low RPM is murder for our fuel pump, and there might be other reasons why, but I am inclined to believe the the high torque\low RPM failure is more of a symptom than a cause. Torque is a force, and independent of speed. 315ft-lbs at 2000RPM puts the same force on the rod as 315ft-lbs at 5000RPM.

Torque, as measured at the wheels, tells you very little about what's going on inside the cylinder. Torque has nothing to do with the rods, since torque is (r x F). There is virtually no r on a connecting rod since the force is along the centerline. All that the rods care about (when in compression) is buckling under the pressure in the cylinder, which is much higher at lower rpm's because the pistons move so much slower than the flame front. So you can back timing off when the engine speed is low, but the flame speed still develops so fast that much of the pressure in the cylinder isn't translated into a moment, and is instead wasted energy transferred into the rods, which makes them buckle.

*Disclaimer - I don't have any idea why the rods break, and don't adhere to either of the explanations. I was just answering the question as to why "torque" is harder on rods at low rpm.

[Lex]

Essentially the flame front moves at essentially the same speed regardless of engine speed. However the speed of the piston is directly proportional to engine speed.

The relationship to torque is that a a high torque reading is attributed to a high cylinder pressure.

[darth vader]

Because of the relatively massive amount of grunt this engine has, people tend to forget it's still a 4 banger as well. That means all engine stress is spread over only 4 rods & pistons, not 6 or 8, with lots more main bearings to help out, too. This places proportionately higher load on each banger, as opposed to an 8 cylinder engine making the same power and torque. You can see why our little engine that could, sometimes couldn't.

[Ziggo]

The flame front explaination makes sense, but the "time under load" is pure bs. That would mean that even at high rpm the power would eventually blow the engine, and with all the people running around with fully bolted engines and many miles it doesn't make any sense.

Cylinder pressure and torque are directly related, if you want to make power you have to have higher cylinder pressures. If the true problem is agressive timing at low rpm it should be a pretty simple fix. Is that what I should take away from this?

[Click Here]

Originally Posted by Ziggo Cylinder pressure and torque are directly related, if you want to make power you have to have higher cylinder pressures.

I don't think anyone was implying that you can make power without cylinder pressure. My point is to illustrate that torque isn't what kills rods (speaking in general), cylinder pressure does. If your engine knocks and cylinder pressure goes through the roof, does your torque increase by any great margin?

Originally Posted by Ziggo If the true problem is agressive timing at low rpm it should be a pretty simple fix. Is that what I should take away from this?

No, the answer to your torque question doesn't have to do with ignition timing. If all things are held equal and you just decrease timing, are you still making 315lbft?

Go run a datalog sometime and look at your ignition timing relative to engine speed. You'll see the computer starts the burn later at lower rpm's (partially) because the engine is rotating slower. It has to or else cylinder pressure gets too high. This has nothing to do with the amount of torque you're making, these are independent issues. The pistons don't move down quickly enough at low engine speeds to convert the available energy into motion, which drives cylinder pressure up, and puts a higher load on the rod. In other words, at lower engine speeds the pistons don't convert heat energy into motion as well as it does at higher speeds.

[Ziggo]

There is a soft spot in timing if it is too far advanced. You will add more timing but see little to no power gains. If the timing is agressive enough to cause the issues you are talking about there would be high cylinder pressures too early, gaining you nothing and you could retard the timing and not see a huge power drop while gaining alot of "safety"

[06Speed6]

You can make power without torque and and massive cylinder pressure with enough rpm. Its all a matter of what kind of power you are looking for.

I used to think it was time under load, but I have come to find that it is not. Ive been putting alot of research into diesels and here is a corrected method to calculate torque.

315ftlb @ 2000rpm is not at all the same stress on the rods as 315ftlb @ 5000rpm. Its all about where on the stroke the peek cyl pressure is achieved. At low rpm our peak cyl pressure comes in very close to tdc so there is very little leverage on the crank and the cyl pressure required to hit 315ftlb is very high. As the rpm goes up, peak cyl pressure is reached further past tdc when the piston has more leverage due to the increased rod angle and as a result less cyl pressure is required to hit 315ftlb. However, on paper, if peak cyl pressure is achieved at the same point on the stroke, then the cyl pressure required to hit 315ftlb is the same regardless of rpm since torque is basically just a calculation of cylinder pressure and rod angle.

[Click Here]

Originally Posted by Ziggo There is a soft spot in timing if it is too far advanced. You will add more timing but see little to no power gains.

lol, yes, that's called finding the minimum best timing. Again, we're not talking about that here. The answer to your question has nothing to do with ignition timing. It has to do with the relationship between the speed of the expanding fuel mixture, and the speed of the piston. Igniting the mixture earlier only reduces cylinder pressure. That's all.

Originally Posted by Ziggo If the timing is agressive enough to cause the issues you are talking about there would be high cylinder pressures too early, gaining you nothing and you could retard the timing and not see a huge power drop while gaining alot of "safety"

Like you suggested in your last post, all you're suggesting is simply one of many ways to reduce cylinder pressure. Following your logic we could just turn the boost down to reduce the cylinder pressure too. You're not grasping the point here.

You specifically asked why torque is harder on rods at lower rpm than at higher rpm. If you retard timing then you're not comparing apples to apples anymore. You're no longer making 315lbft. I'm not sure how else to illustrate this. Several people have told you that the answer to your question is the pistons don't convert all the available heat energy into mechanical motion at low rpm's. This fact is totally irrespective of when the mixture is ignited.

If you're simply looking to reduce cylinder pressure, sure, retarding the timing will do this. But this doesn't make torque any easier on rods at low rpm. I think you need to disassociate torque, from cylinder pressure.

[darth vader]

So...let's say I want to accelerate on the highway between 60 and 120 mph. Let's say I choose to start that run in 4th gear. Let's do the same run in 6th. Now I'm eyeballing my absolute load and what do think I'm going to see? Same load values or higher for the 6th gear run? I'm thinking higher and, thus, greater stress on the rotating assembly. One thing's for sure, too, it's gonna take alot more time to do it in 6th.

Highlight my errors in reasoning, please.

[Ziggo]

I think you need to disassociate torque, from cylinder pressure.

Thats what I am trying to explain, that the only way cylinder pressures end up out of whack with the measurable torque is if the timing is too advanced and if adjusting timing doesn't fix it you are getting pre-detonation. (not spark knock)

My point was that torque is torque, no matter the speed of the engine. If the real "low-rpm" problem was cylinder pressure that was not being translated to torque then retarded timing would be the fix. I understand that you may be reducing the available torque slightly doing this, but it wouldn't be much, because if peak cylinder pressures were spiking high enough to cause this issue, without showing massive torque numbers, then the timing would be too advanced. I think you understand this since you mentioned the moment arm earlier. Cylinder pressure doesn't equal torque when the moment arm is small, but with proper timing you reduce "peak" cylinder pressure while still capturing most of the energy available.

Several people have told you that the answer to your question is the pistons don't convert all the available heat energy into mechanical motion at low rpm's. This fact is totally irrespective of when the mixture is ignited.

Then where does that energy go? And why is it not dependent on when the mixture is ignited? I don't want people to tell me, I want people to tell me why. Unless it is causing plastic deformation of the rod (which I know it can, but it certainly doesn't do that every stroke) until the exhaust valve opens the energy from combustion either gets carried away as waste heat, or becomes kinetic energy. It can only be one of the two. Generally at low rpms, slightly more of the energy gets carried away as waste heat, but that would only reduce the available kinetic energy, and thus reduce cylinder pressure/torque/rod force.

I am not trying to be an ass, I am just trying to get what I know about engines from both the classroom and the garage to mesh with what is said about these cars so that when I install the parts sitting in my garage I know how to end up in the "i've been bolted for 50k miles" club. I would rather know the problem, rather than ways to drive around it so that when my wife, who no matter how many times I tell not to load up the engine down low still does it, drives the car it doesn't blow up.

[Ziggo]

Originally Posted by darth vader So...let's say I want to accelerate on the highway between 60 and 120 mph. Let's say I choose to start that run in 4th gear. Let's do the same run in 6th. Now I'm eyeballing my absolute load and what do think I'm going to see? Same load values or higher for the 6th gear run? I'm thinking higher and, thus, greater stress on the rotating assembly. One thing's for sure, too, it's gonna take alot more time to do it in 6th. Highlight my errors in reasoning, please.

The time to accelerate between 60 and 120 is dependent on power not purely torque. That is why you see a quicker time in 4th than 6th. The stress on the components would be higher in 6th than in 4th, if 6th was planting you at the torque peak and 4th was not. But I am sure you already know all of that.

My issue with the "time under stress" argument was that it doesn't mesh with the way metals behave. Fatigue failures are a result of load cycles, not of time.

It could be the failures were the result of the torque putting the components above the fatigue limit, but that wouldn't be dependent on RPM. Unless your timing was bad as discussed above, it wouldn't matter what rpm you made the torque, it would still eventually pop the engine, and we could just say simply "the stock internals cannot reliably handle torque levels above xxxft-lbs" The failures observed don't seem to be a result of simple fatigue, otherwise there wouldn't be such a random spread of when people are popping their engines. I haven't looked at a snapped rod either, but from what has been said, there doesn't seem to be evidence of crack propagation which would be evident with a fatigue failure.

[06Speed6]

I think you guys completely missed my post, its number 306.

Torque is a direct result of cylinder pressure and rod angle.

Torque is not a result of time.
Torque is not a direct result of ign timing.
Torque is not a direct result of charge heat.
Torque is not a direct result of flame front expansion velocity.
Torque is not a result of piston speed.

Cylinder pressure is a direct result of ign timing.
Cylinder pressure is a direct result of charge heat.
Cylinder pressure is a direct result of the flame front expansion velocity.
Cylinder pressure is a direct result of the air/fuel ratio.
Cylinder pressure is a direct result of the dynamic compression ratio.
Cylinder pressure is a direct result of the chamber shape and quench area.
Cylinder pressure is a direct result of volumetric efficiency.
Cylinder pressure is a direct result of boost psi.
Cylinder pressure is a direct result of intake charge temp.
Cylinder pressure is a direct result of fuel atomization.
Cylinder pressure is a direct result of cam phase timing.
Cylinder pressure is a direct result of cam duration.
Cylinder pressure is a direct result of cam lift.
Cylinder pressure is a direct result of the chamber's seal.
Cylinder pressure is a direct result of the crankshaft's stroke vs the cyl bore dia.
Cylinder pressure is a direct result of probably other things.

[Ziggo]

I did miss your post, but you seem to understand clearly the issue. I will try to sum up the why later when I am not on my iPhone, but if peak cylinder pressure timing is the issue then you would retard timing at low rpm, which would slightly affect the torque but would reduce peak cylinder pressure, and thus the stress on the rod. If peak cylinder pressures are already properly timed then you are at the strength limit of the stock rods and you need to try to tune and mod to move the torque peak to higher in the rpm, which usually means reduced torque but higher power.

[darth vader]

Originally Posted by Ziggo The time to accelerate between 60 and 120 is dependent on power not purely torque. That is why you see a quicker time in 4th than 6th. The stress on the components would be higher in 6th than in 4th, if 6th was planting you at the torque peak and 4th was not. But I am sure you already know all of that. My issue with the "time under stress" argument was that it doesn't mesh with the way metals behave. Fatigue failures are a result of load cycles, not of time. It could be the failures were the result of the torque putting the components above the fatigue limit, but that wouldn't be dependent on RPM. Unless your timing was bad as discussed above, it wouldn't matter what rpm you made the torque, it would still eventually pop the engine, and we could just say simply "the stock internals cannot reliably handle torque levels above xxxft-lbs" The failures observed don't seem to be a result of simple fatigue, otherwise there wouldn't be such a random spread of when people are popping their engines. I haven't looked at a snapped rod either, but from what has been said, there doesn't seem to be evidence of crack propagation which would be evident with a fatigue failure.

Gotcha, yer right in para 1, I do know that.

I wasn't referring to the torque-production issue, which seems different. I was merely referring to the real-world LOAD situation that puts maximum stress on any IC engine. Perhaps people keep doing things that stress the motor in ways it isn't designed/tuned for, i.e low-rpm, high load lugging on fully bolted cars = Popcorn.

I think CX7s don't blow, despite being theoretically loaded harder than a Speed, being heavier, saddled with 4 wheel drive/automatics and driven by an "older crowd", because people generally don't modify them, increasing the specific output of the engine and closing in the safety margins on stock parts.

There has to be a connection between the modifying and the blowing, since there seems to be so few stock Speeds popping.

[Click Here]

Originally Posted by Ziggo Thats what I am trying to explain, that the only way cylinder pressures end up out of whack with the measurable torque is if the timing is too advanced and if adjusting timing doesn't fix it you are getting pre-detonation. (not spark knock)

You could argue that but you'd be wrong. 06Speed6 gave you many examples of why your statement is false.

Originally Posted by Ziggo My point was that torque is torque, no matter the speed of the engine. If the real "low-rpm" problem was cylinder pressure that was not being translated to torque then retarded timing would be the fix. I understand that you may be reducing the available torque slightly doing this, but it wouldn't be much, because if peak cylinder pressures were spiking high enough to cause this issue, without showing massive torque numbers, then the timing would be too advanced. I think you understand this since you mentioned the moment arm earlier. Cylinder pressure doesn't equal torque when the moment arm is small, but with proper timing you reduce "peak" cylinder pressure while still capturing most of the energy available.

Again, if you're in the game of reducing cylinder pressure than retarding timing is a fine solution.

Originally Posted by Ziggo Then where does that energy go? And why is it not dependent on when the mixture is ignited? I don't want people to tell me, I want people to tell me why. Unless it is causing plastic deformation of the rod (which I know it can, but it certainly doesn't do that every stroke) until the exhaust valve opens the energy from combustion either gets carried away as waste heat, or becomes kinetic energy. It can only be one of the two. Generally at low rpms, slightly more of the energy gets carried away as waste heat, but that would only reduce the available kinetic energy, and thus reduce cylinder pressure/torque/rod force. I am not trying to be an ass, I am just trying to get what I know about engines from both the classroom and the garage to mesh with what is said about these cars so that when I install the parts sitting in my garage I know how to end up in the "i've been bolted for 50k miles" club. I would rather know the problem, rather than ways to drive around it so that when my wife, who no matter how many times I tell not to load up the engine down low still does it, drives the car it doesn't blow up.

I know you're not being an ass, you're just not grasping the point

[FORZDA 1]

Here's a quote from Corky Bell () Bell Experimental Group - BEGi , the forced induction expert of Bell Engineering Group Inc., for you guys to chew over:

"1. The highest compressive load in the conrod occurs at bottom dead
center at redline, until boost pressure exceeds approximately 13/14
psi. Above 13/14 psi boost pressure, the maximum load point shifts to
around 50/70 degrees after TDC."


IMO, the point to ponder is that the "tune" as in boost @ rpm directly affects the forces/angle on the con rod. The maximum "normal" forces are felt at redline, nowhere else, regardless of boost/Load. It seems the DISI rods are quite strong under all these "normal" ranges and will hold up to quite a lot of boost/rpms UNLESS you screw around with the TUNE and get significant detonation at high rpm WOT. I'm going on rough memory here, but I'm pretty sure that most, if not all of the bent/broken rod engines did indeed see "some" event that resulted in one of these severe overloads.

The reason, IMO, that the rods don't snap at high rpms is that they are forged steel which will bend and endure many stress overloads into elastic before failing to plastic and breaking.

Once the rod load angle is compromised, the off-plane loads result in greatly accelerated stress cycles and bending until the piston begins to contact the crank counterweight which allows the wrist pin to "escape" and the complete failure of the rod..., etc. THIS is why (IMO) John is seeing rods that are tweaked in 2 or more planes rather than a single-event staight to failure.

Corky also says that:

" 2. The most destructive load of all is the tension in the
rod/pin/piston assembly at top dead center on the exhaust stroke when
the intake and exhaust valves are open."

Just more to ponder.....

[06Speed6]

Originally Posted by Ziggo I did miss your post, but you seem to understand clearly the issue. I will try to sum up the why later when I am not on my iPhone, but if peak cylinder pressure timing is the issue then you would retard timing at low rpm, which would slightly affect the torque but would reduce peak cylinder pressure, and thus the stress on the rod. If peak cylinder pressures are already properly timed then you are at the strength limit of the stock rods and you need to try to tune and mod to move the torque peak to higher in the rpm, which usually means reduced torque but higher power.

Ign timing, as it pertains to cyl pressure is, I think, at the root of the problem. Now I will say that there is no way to determine or model peak cyl pressures short of a cnc head with a port machined into the chamber.

It is interesting to note that on this engine the ign timing is nearly always advanced, and it is almost never at TDC or ATDC. Most gasoline engines can be retarded to ATDC up to ~10* at very low rpms when they experience high loading

Gasoline engines typically shoot for horsepower at higher rpm and have to advance the timing into the compression stroke in order for the flame front to have enough time to develop and build cyl pressure for the down stroke. Typically in a gasoline engine, peak cyl pressure is achieved within the first 15* after TDC, this is very good for horsepower which is calculated as torque over time. The longer you can maintain high cylinder pressures on the down stroke, the higher the horsepower will be.

Diesel engines typically shoot for torque at low rpm and do not have an ignition system to advance. The mix in a diesel engine is ignited by heat and pressure at or close to TDC and due to the slower burn of diesel fuel, the piston is down in the bore before peak cyl pressure is reached. This results in a tremendous amount of torque due to their very large stoke to bore ratios, but it is fairly easy on the piston, pin, and rods because of the multiplication of the leverage. Additionally on a diesel engine, the injectors can be spraying fuel into the cyl from the start of the intake stroke to well into the power stroke past the point of peak cyl pressure, this additional fueling can lead to the black smoke that diesels are known for because of incomplete burn of the final bit of fuel that gets injected.

EDITING NOTE: In regards to Forzda's post, compressive load is not the same as peak cyl pressure loading. Compressive load is peak cyl pressure + rotating assembly g forces.

[darth vader]

Looks like my initial instincts with this motor were on the right track, if we accept the above Forzda posts:

Don't WOT boot it under 3k (good practise with any automotive gas engine) and shift below 6. This has been said before no doubt but, any noobs still reading this should heed the advice.

I set my light to trigger at 5400, giving me room for flare on a flat shift.

Using a similar idea, namely, shifting under 6K, I kept a boosted and nitroused 5.0 alive for 10 seasons of drag racing and sold it still running as good as ever. All my friends who got greedy ended up picking up pieces.

What I can't seem to totally control, given my state of mods (all in and out on stock tune, bar aftermarket IC) is staying under the load cap. My car, I think, is at close to max for what the stock tune can support and I'm tweaking the MBC to just hold it under the load cap. There's more power to be made (afrs good, no knock, etc.), I know but, that cap prevents progress from this point. However, that is fine. Getting greedier than this may not be wise in a car I'm still paying for and need every day.

[FORZDA 1]

Originally Posted by 06Speed6 ......EDITING NOTE: In regards to Forzda's post, compressive load is not the same as peak cyl pressure loading. Compressive load is peak cyl pressure + rotating assembly g forces.

Correctamundo! I thought the ultimate compressive load was the real issue we're concerned about. Otherwise it's just a debate over definitions.....

[06Speed6]

Well it is a problem, but since we kinda have to rev the engine to have any fun with it, I think that controlling cyl pressure is where it is at.

[FORZDA 1]

Originally Posted by 06Speed6 Well it is a problem, but since we kinda have to rev the engine to have any fun with it, I think that controlling cyl pressure is where it is at.

True, so I'm not saying we should limit rpms. We control cyl pressure with timing and Load/boost control via accurate tuning as we rev the engine higher. We just need to know the effects on the engine components.

I rev mine well past 6k and usually shift ~65-6700. Stay away from KR @ WOT/high revs and all "should" be fine. As the weather hits 90+ deg ambient I occasionally get up to 2.5KR under heavy loads at ~5.5K rpm. I will likely pull a degree or 2 of timing at >5k rpm or try a different brand of fuel to help correct it. I never had ANY KR until the local Exxon station sold out to 7-11 and changed fuel suppliers...

And the fuel quaility is a variable that never seems to get mentioned in these threads. If we're ruinning very high cyl pressures in trying to extract the big numbers for the dyno or track, the fuel quality becomes a VERY important variable. We must consider the chance that we'll get a "less-than-optimum" tank now and again, so the STREET tune MUST allow some wiggle room for the fuel...

[Lex]

Also note that KR goes to 0 abruptly at 5700 RPM while a sweet knock point for the car is 5500 RPM.

The fuel quality comment is very important - I have very shitty fuel here on the west coast even though it's labeled as 94 Octane and priced at over $5 a gallon. I have to account for that more so than east coast people that enjoy better blends.