DISI Compression Results

[ms3blackmica]

Originally Posted by boost_addict Have your head or block ever been machined? We ran a compression test on a friends miata after it was rebuilt and our #'s were 10PSI higher than the max spec. It was because the head was decked a few thousandths.

No I bought the car new in 09 and have never removed the head.

[phate]

Does Mazda actually allow engines to be rebuilt? AFAIK, they will replace the engine, but not allow a rebuild. Ford is the same way, and it is due to the "new age" machining required.

If his head or block were milled, it probably wasn't through Mazda

[sidekick]

Originally Posted by ms3blackmica No I bought the car new in 09 and have never removed the head.

Maybe your high compression #'s have something to do with you making more power than most? Maybe you don't have a magical K04 after all

[ms3blackmica]

Why I have such high compr. #'s I am not sure. Tight engine is tight? I don't really know.

I checked compr. again 2 nights ago and it was still 200~205 in all 4. On a warm day I'll see up to 210. TBH, I don't even care that they are strong #'s, I am just glad they are all the same @ 63,000 miles !

[Lex]

The Skyactiv motors are not rebuildable period.

[sidekick]

Originally Posted by ms3blackmica Why I have such high compr. #'s I am not sure. Tight engine is tight? I don't really know. I checked compr. again 2 nights ago and it was still 200~205 in all 4. On a warm day I'll see up to 210. TBH, I don't even care that they are strong #'s, I am just glad they are all the same @ 63,000 miles !

It just means all of your rings and valves seal well, Your engine is pretty much as healthy as it gets.

Originally Posted by Lex The Skyactiv motors are not rebuildable period.

Why is that?

[supertubesocks]

Originally Posted by boost_addict It just means all of your rings and valves seal well, Your engine is pretty much as healthy as it gets. Why is that?

Machining operations require purified unicorn semen.

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[Dano]

Sprayed on steel cylinder walls IIRC


Tappin

[sidekick]

Originally Posted by Dano Sprayed on steel cylinder walls IIRC Tappin

mind blown... lol steel in a can? So basically it's not possible to hone/bore them?

[Lex]

Originally Posted by boost_addict mind blown... lol steel in a can? So basically it's not possible to hone/bore them?

You got it

[Dano]

disposable blocks. but then again Mazda will not rebuild a motor, ever. they put new ones in so to them there is no reason to build a block that can be resurfaced. I suspect that saves them money and with uber thin cylinder walls, heat transfer to the coolant has got to be much improved.

[Lex]

Originally Posted by Dano disposable blocks. but then again Mazda will not rebuild a motor, ever. they put new ones in so to them there is no reason to build a block that can be resurfaced. I suspect that saves them money and with uber thin cylinder walls, heat transfer to the coolant has got to be much improved.

A good 5-6 years ago one of my friends was working in a machine shop where they rebuilt motors. He was going through his apprenticeship. We were building one of my motors at the time and now he is an HVAC service tech for Honeywell. He said there is no future in the engine rebuilding business and that shops are losing more clientele each year. No one fixes TVs anymore either.

It is part of evolution. The processes employed by the factories have such tight tolerances and are increasingly less expensive that it is very difficult to achieve the same for a small shop/business. The shops that remain in business will only be dealing with older engines and cars ... but the good thing for us, the consumer, is that new factory engines are better and better off the shelf.

[fredricktsang]

so making monster power on future cars is gonna be insanely expensive because you would need to start with a new block? sigh... or drop in a different engine completely

[timjs]

Mazda does rebuild the rotaries, but as far as I know the piston engines are all new.

[btstarcher]

Figured I would post my results here as well; 182, 180, 120, 195. After pouring a little oil in the results were 185, 182, 121, 200. This is a built motor with about 1500 miles at the time of the test. I'll be doing a leakdown test as soon as possible.

[ms3blackmica]

Originally Posted by btstarcher Figured I would post my results here as well; 182, 180, 120, 195. After pouring a little oil in the results were 185, 182, 121, 200. This is a built motor with about 1500 miles at the time of the test. I'll be doing a leakdown test as soon as possible.

Ben, I hope it is related to a valve!

[btstarcher]

I'm thinking it is. Unfortunately that would mean tearing into the engine again possibly. I kinda hope he just didn't quite get the measurements right when he checked the clearances; I think that would be an easier fix. I don't think it's the injector seals; for one thing, we were very careful about putting the injectors back in. Also I'm not seeing much KR at all on any of my logs.

[ms3blackmica]

Originally Posted by btstarcher I'm thinking it is. Unfortunately that would mean tearing into the engine again possibly. I kinda hope he just didn't quite get the measurements right when he checked the clearances; I think that would be an easier fix. I don't think it's the injector seals; for one thing, we were very careful about putting the injectors back in. Also I'm not seeing much KR at all on any of my logs.

I don't think its the injector seal.

I had a completely leaking toyota seal once on cyl #2 and my compression was no where near that low.

It never hurts to check these things, however.

[btstarcher]

I thought the funniest part of the conversation was when he suggested that the rings were still seating, that the motor isn't fully broken in. Probably not, but damn, why would 1 cylinder be that much lower? I hated to hear that, because I liked this guy. He seemed like someone I could trust.

[Nliiitend1]

Good luck.

[Lex]

A leakdown test will show you where the leak is coming from with such a large compression difference.

[daafisch]

Did a compression test today. Rented the gauge from a newly opened Autozone.

From left to right: 190/165/190/195. Wet test of the low one brought compression up to 190.

Main reason I tested the compression is because I'm getting some oil out of my valve cover vent.

[802MS3]

have you been watching your oil temps at the track? what oil have you been using?

[daafisch]

I have not been watching my oil temps at the track as I have no way of doing so yet. I've been running Rotella since about 40k.

[Lex]

Originally Posted by daafisch I have not been watching my oil temps at the track as I have no way of doing so yet. I've been running Rotella since about 40k.

Did this start happening after a track event? It may be the ringlands. If you watch the hot idle vacuum readings you should be getting less vacuum at idle with lower compression. Any other drive ability issues aside from the oil in the intake?

[daafisch]

Originally Posted by Lex Did this start happening after a track event? It may be the ringlands. If you watch the hot idle vacuum readings you should be getting less vacuum at idle with lower compression. Any other drive ability issues aside from the oil in the intake?

I'm not sure when it started. I track/autox through out the entire summer, the car is and has been running fine so I never had a real reason to remove the intake. Only noticed it when I took out my maf to clean it. Right now I have a small catch can in between the vent and my intake.

I'll make note of my idle vacuum when I leave work and when I get home.

[Dano]

Exactly the symptoms I went through when I broke my ringland in #3 .

First started to "oil" my maf and intake so I put an OCC vta on the VC vent. Fast forward a few months and the failure was confirmed

Seems this has now become a mainstream failure mode. The uber tight OEM ring gaps coupled with high oil/coolant and cylinder temps overall is taking its toll and the rings butt.

Sorry to hear it.


Tappin

[daafisch]

I thought I noted my mileage but apparently I didn't. Engine has 117k on it.

[Lex]

Originally Posted by Dano Exactly the symptoms I went through when I broke my ringland in #3 . First started to "oil" my maf and intake so I put an OCC vta on the VC vent. Fast forward a few months and the failure was confirmed Seems this has now become a mainstream failure mode. The uber tight OEM ring gaps coupled with high oil/coolant and cylinder temps overall is taking its toll and the rings butt. Sorry to hear it. Tappin

I think we have to start thinking about removing more heat from the motor on high power or tracked cars in hot weather or at least monitoring temperatures. This is something I am looking into.

Originally Posted by daafisch I'm not sure when it started. I track/autox through out the entire summer, the car is and has been running fine so I never had a real reason to remove the intake. Only noticed it when I took out my maf to clean it. Right now I have a small catch can in between the vent and my intake. I'll make note of my idle vacuum when I leave work and when I get home.

Thanks for the insight. Please do post the warm vacuum readings.

[Dano]

Originally Posted by Lex I think we have to start thinking about removing more heat from the motor on high power or tracked cars in hot weather or at least monitoring temperatures. This is something I am looking into. Thanks for the insight. Please do post the warm vacuum readings.

I posted this in another thread but:

is it time to go to cooler thermostats or get better fan control, oil coolers? What would be the least troublesome approach that would yield the best results?

I personally don't like seeing my car run at 217-220ish all summer long. The fan will not even come on until it is 217 or the motor is shut off which ever comes first.

I have no idea what the thermostats are rated at and if cooler models are available, and if that would make a difference in a DD situation. on an open course with a ton of airflow maybe that is all that is needed but in city traffic it may make little difference.
@Ziggo; has replaced his I think and wonder what it is rated at and if he knows of the availability of others and what difference it made in his ECT...is does live in Texas for god sake.

this may not be necessary for a forged motor, yet, but better heat management for the OEM ring gaps is def necessary.

[Nliiitend1]

Originally Posted by Lex I think we have to start thinking about removing more heat from the motor on high power or tracked cars in hot weather or at least monitoring temperatures. This is something I am looking into.

Agreed.

I only did one trackday last year (on one of the hottest days of the year in the Midwest) after you tuned my car, and had to end my day early (before the end of the 5th of 6 sessions) due to heat-related issues (slipping clutch primarily).

I'm not a "high-horsepower guy" by any means, but I do tend to drive the proverbial piss out of my car and am still at the very least going to be running one of the map iterations you sent me that has less timing advance in it the next time I go to the track because of this (at least until I get a "fresh" clutch and perhaps upgrade to a Koyo radiator).

I'd also like to get an oil temp gauge (and maybe even transmission fluid temp guage, a la @Tomas;'s setup) as well...

[Lex]

Originally Posted by Dano I posted this in another thread but: is it time to go to cooler thermostats or get better fan control, oil coolers? What would be the least troublesome approach that would yield the best results? I personally don't like seeing my car run at 217-220ish all summer long. The fan will not even come on until it is 217 or the motor is shut off which ever comes first. I have no idea what the thermostats are rated at and if cooler models are available, and if that would make a difference in a DD situation. on an open course with a ton of airflow maybe that is all that is needed but in city traffic it may make little difference. @Ziggo; has replaced his I think and wonder what it is rated at and if he knows of the availability of others and what difference it made in his ECT...is does live in Texas for god sake. this may not be necessary for a forged motor, yet, but better heat management for the OEM ring gaps is def necessary.

It depends really. A tstat that opens earlier may lower your cruising temps but it may do very little once you exceed the cooling capacity of the system at WOT. Perhaps delay things a bit at most.

The car was designed to reject 270hp worth of heat and 400whp cars are at 450+crank. That's 50% more heat the must be rejected. Perhaps starting another thread about this is best.

[phate]

Agreed, a dedicated thread to get some ideas out there would be good.

[Dano]

Originally Posted by Lex It depends really. A tstat that opens earlier may lower your cruising temps but it may do very little once you exceed the cooling capacity of the system at WOT. Perhaps delay things a bit at most. The car was designed to reject 270hp worth of heat and 400whp cars are at 450+crank. That's 50% more heat the must be rejected. Perhaps starting another thread about this is best.

good idea..I'll put one together with liniks to some of the pertinent information...if somebody gets to it first feel free and link it here.

[Dano]

MZR DISI Heat Management

[daafisch]

Originally Posted by Lex Thanks for the insight. Please do post the warm vacuum readings.

Just got home from work (50 mile commute 80% highway)

Vacuum at idle was 21.56 and when I got home it was the same. The pic with the red screen is the hot idle. Both were with ac off.



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[daafisch]

So @Lex; what would it mean if I'm not getting any lower vacuum at idle?

[atvfreek]

Originally Posted by daafisch So @Lex; what would it mean if I'm not getting any lower vacuum at idle?

Vacuum looks good to me. Usually with a cold motor I see about 19" vacuum and hot motor 21-22.

Sent from your couch

[daafisch]

Originally Posted by atvfreek Vacuum looks good to me. Usually with a cold motor I see about 19" vacuum and hot motor 21-22. Sent from your couch

So if vacuum usually drops with lower compression what does it mean that its staying the same?

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[Nliiitend1]

Does your vacuum fluctuate at all while the car is running, or does it stay pretty steady (at idle or under steady load)?