How fast is too fast

[Jeff23spl]

Originally Posted by MS3Shadow I'm going the cooling benefit when using the WMI injection with using less than <50% meth. sent from my Nexus 6P

What size is your jet ? I was asking myself how much water could be too much for good combustion.
I have tried the 330cc with 100% water, it was still droping bats without slowing down the car. i was using higher octane mix in the tank to be sure so this test may not be very accurate but i know 330cc won't flood the engine.

At the end of the day, there is more than 1 road to higher horsepower. I like my injection kit but it could be better/safer and other may preffer it in the tank but it can be limited also...

[BMC]

In doing the WOT runs for the new tune, if the road is clear I just keep sailing through the gears. I'm noticing that the on board tach is way off. The difference between the AP (log) and tach readings seems to get wider at the top end of the higher gears ... by at least a few hundred points ... maybe more. Again, I'm just glancing at the tach at those speeds (and I certainly caught a load of crap for doing that with my initial post) but the on board tach looks like it's reading high by hundreds of RPMS.

[MD1032]

Yeah on my 2012 I don't hit the rev limiter (6700) until the needle is past 7000. I've been in other 2012+ Pu's that are the same way

Sent from my A0001 using Tapatalk

[Jeff23spl]

Originally Posted by BMC The difference between the AP (log) and tach readings seems to get wider at the top end of the higher gears ...

It shouldn't because rpm has nothing related to gear or speed. It is usually a voltmeter scaled in rpm driven by a pcm voltage but when accelerating, you have more time to compare both in higher gear.

Start looking at obd2 rpm first and then at the gage, the difference will be larger VS if you look at gage and then at the rpm...

[mituc]

Originally Posted by BMC BTW, to those who have responded with calls of BS, not much I can say to that. I was of the impression that stock topped out at 158 mph. Despite my mods, I was suprised to see it pulling higher than that. I appreciate that without video to back me up I'm a sitting duck for the BS calls. That said, I'm hoping to try another few runs before it goes away for the winter and will attempt to catch some footage. I don't have any real camera gear that I can set up to capture it and have noticed that a second body in the car (potential camera holder/operator) really slows things down. I'll try just hanging a cell phone at an appropriate angle and hope for the best. I've only got about 12500 miles on the vehicle and it still seems to be getting quicker. Oh, and for questions about the very specific "263kph", it was above 260 but only by a little. I guessed 263.

My car did 260Kmph (tacho) bone stock as well. I did that several times, for several kilometers (or miles, whatever), as the German autobahn allows this.
With the factory programmed error in the tacho, and the factory 215/45/r18 tires for a gen1, 265Kmph on the tacho are about 250Kmph GPS speed which on normal tires it's basically the same as the OBD speed (tacho shows more for very specific reasons). And 250Kmph is 155mph.

Once you start modding the top speed has two enemies:
1. heat. More power means more heat. In its factory form, a vehicle can go to its top speed (software limited like in our case, or not) slower therefore needing less power and thus generating less heat;
2. gearbox and the rev limit you can run. At 6700rpm in 6th the speed is about 280-283Kmph with the factory tires. If you increase the rev limit and remove both speed limiters you can go as fast as you can, assuming you're not running into cooling issues.

[BMC]

Originally Posted by Jeff23spl It shouldn't because rpm has nothing related to gear or speed. It is usually a voltmeter scaled in rpm driven by a pcm voltage but when accelerating, you have more time to compare both in higher gear. Start looking at obd2 rpm first and then at the gage, the difference will be larger VS if you look at gage and then at the rpm...

I thought that RPM had everything to do with gear and speed. Although the numbers are now generated electronically rather than mechanically, they continue to indicate motor RPMs at a particular speed, in a particular gear. Sorry to be thick about this but I don't follow.

"Start looking at obd2 rpm first and then at the gage, the difference will be larger VS if you look at gage and then at the rpm..."

I also don't get how the order of viewing the two readouts will affect the spread. Feel free to explain. I'm here to learn. Thanks.

[BMC]

Originally Posted by mituc My car did 260Kmph (tacho) bone stock as well. I did that several times, for several kilometers (or miles, whatever), as the German autobahn allows this. With the factory programmed error in the tacho, and the factory 215/45/r18 tires for a gen1, 265Kmph on the tacho are about 250Kmph GPS speed which on normal tires it's basically the same as the OBD speed (tacho shows more for very specific reasons). And 250Kmph is 155mph. Once you start modding the top speed has two enemies: 1. heat. More power means more heat. In its factory form, a vehicle can go to its top speed (software limited like in our case, or not) slower therefore needing less power and thus generating less heat; 2. gearbox and the rev limit you can run. At 6700rpm in 6th the speed is about 280-283Kmph with the factory tires. If you increase the rev limit and remove both speed limiters you can go as fast as you can, assuming you're not running into cooling issues.

Thanks for the supportive post. When I did the run mentioned at the top of this post, my car was modded as per my signature but without the in-tank-meth. I'm guessing my attempt to duplicate what I saw (with data log and video) was a result of different ambient conditions and a stretch of road that went into a slight uphill at the end of my run.

[Jeff23spl]

not sure if you were talking only about RPM error between cluster tach and OBD RPM or RPM vs the car speed.
In the first place, the RPM error from cluster to obd will always remain the same regardless of the gear because it read the engine crank speed before the transmission gears. OBD2 reading will be accurate and then transformed to an analog signal for the cluster gage needle. This is where the error comes from. Converter error + needle error.

Then, if you use RPM to calculate a theoric car max speed, yes the error will be amplified by the gears ratio as the equation for speed is engine RPM x gear ratio x diff ratio x tires circonfférence. This is why you need to use the real 6700 rpm cut off from obd rpm not the cluster redline.

Then i think the car speed display either from OBD or speed cluster is not using the RPM but ABS sensors. So it really read the wheel rotation speed meaning the only thing that could change the obd speed VS the real car speed is the tire size. But again the cluster needle is using a converter with some error margin to display the data from the obd system.

For the part about comparing both RPM, it is just that during an high speed driving, you probably look at both rpm separately and everythinh happend fast. The small amount of time you switch your eyes between one display to the other is enough to minimise or amplify the error because the real rpm is shifting up or down...

You may compare rpm, in lower gears, at fixed speed, so this will allow more time to look at everything while keeping an eyes on the road ahead. So if that test returns you a 400 rpm error between cluster and cobb AP, the same 400 rpm error will exist in 6th gear at full speed.

[mituc]

Originally Posted by Jeff23spl not sure if you were talking only about RPM error between cluster tach and OBD RPM or RPM vs the car speed.

Both have programmed errors. The RPM gauge displays the RPM witha linear variation. At 6700rpm real the gauge will indicate 7000. At 3350 it will show 3500. And so on. the OBD rpm is accurate.

Same for the speed, even though the actual car speed has one more variable that alters it, the tire size (including wear, keep in mind that a tire can loose 4-5mm from its radius and it's still usable. However, with new OEM tires inflated to spec (I'm saying OEM tires not OEM size tires, not all tires of the same size are equal at the spec inflation) the OBD speed will be the same as the GPS speed and it's calculated based on some sensor in the gearbox that always looks at the rotation speed of the final drive

Originally Posted by Jeff23spl Then, if you use RPM to calculate a theoric car max speed, yes the error will be amplified by the gears ratio as the equation for speed is engine RPM x gear ratio x diff ratio x tires circonfférence. This is why you need to use the real 6700 rpm cut off from obd rpm not the cluster redline.

These errors (due to tire size variation or due to the actual error programming) don't change the fact that the car in discussion reached that tacho speed.

Originally Posted by Jeff23spl Then i think the car speed display either from OBD or speed cluster is not using the RPM but ABS sensors.

No, it uses a sensor in the gearbox, but whatever sensor it would use the calculated wheel rotation speed will be the same. That's why we can talk OBD speed instead of GPS speed, to exclude the tire size from this equation. the tacho speed will also have a specific/calculated/programmed variation from the OBD speed, not from the GPS speed.

On a gen1 at 155mph/250Kmph OBD speed the engine RPM is 5950 or so in 6th. If the speed limits are removed then at 6700rpm the OBD speed would be 281.5kmph or 176mph.
If you have the right mods and the engine car cool properly to do a full pull in 6th then with a rev limit of 7000rpm the OBD speed would be 294kmph or 183mph. 300kmph/187mph at 7150rpm and the holy graal of 320kmph/200mph can be reached with these gear boxes at 7600rpm, but at this speed if the engine is still in one piece the gearbox may start shitting metal bits.

[BMC]

Originally Posted by Jeff23spl not sure if you were talking only about RPM error between cluster tach and OBD RPM or RPM vs the car speed. In the first place, the RPM error from cluster to obd will always remain the same regardless of the gear because it read the engine crank speed before the transmission gears. OBD2 reading will be accurate and then transformed to an analog signal for the cluster gage needle. This is where the error comes from. Converter error + needle error. Then, if you use RPM to calculate a theoric car max speed, yes the error will be amplified by the gears ratio as the equation for speed is engine RPM x gear ratio x diff ratio x tires circonfférence. This is why you need to use the real 6700 rpm cut off from obd rpm not the cluster redline. Then i think the car speed display either from OBD or speed cluster is not using the RPM but ABS sensors. So it really read the wheel rotation speed meaning the only thing that could change the obd speed VS the real car speed is the tire size. But again the cluster needle is using a converter with some error margin to display the data from the obd system. For the part about comparing both RPM, it is just that during an high speed driving, you probably look at both rpm separately and everythinh happend fast. The small amount of time you switch your eyes between one display to the other is enough to minimise or amplify the error because the real rpm is shifting up or down... You may compare rpm, in lower gears, at fixed speed, so this will allow more time to look at everything while keeping an eyes on the road ahead. So if that test returns you a 400 rpm error between cluster and cobb AP, the same 400 rpm error will exist in 6th gear at full speed.

I was referring to the difference between what I saw on the cluster tach during my run and the AP log data after my run. During my run I note my RPM shift points on my cluster tach. I do appreciate the explanation you provided. Thanks.

[Jeff23spl]

Originally Posted by mituc No, it uses a sensor in the gearbox, but whatever sensor it would use the calculated wheel rotation speed will be the same. That's why we can talk OBD speed instead of GPS speed, to exclude the tire size from this equation. the tacho speed will also have a specific/calculated/programmed variation from the OBD speed, not from the GPS speed. On a gen1 at 155mph/250Kmph OBD speed the engine RPM is 5950 or so in 6th. If the speed limits are removed then at 6700rpm the OBD speed would be 281.5kmph or 176mph. If you have the right mods and the engine car cool properly to do a full pull in 6th then with a rev limit of 7000rpm the OBD speed would be 294kmph or 183mph. 300kmph/187mph at 7150rpm and the holy graal of 320kmph/200mph can be reached with these gear boxes at 7600rpm, but at this speed if the engine is still in one piece the gearbox may start shitting metal bits.

Ok thanks i though it could have used ABS sensor but i remeber now that i did see a pickup coil in the rear of the trans when rebuilding it....Like you said, it doesn't matter, abs and diff would run at the same rpm as long as the stering isn't turned. But in both case the VSS data would be proportional of wheel speed regardless of the gear used...So only tires difference remain.

It is picky, but at the end of wear, pressure and tires brand, you can also add the fact that the tire would expand a little bit at very high speed and raise it's circonference ...a little...

For 200mph, even 176, in my mind, it would need more than 275-300whp to reach it with the actual CX of the car.
We should keep in mind the availaible torque, to spin the wheels, drop very quickly at higher rpm, especially with the stock and tiny k04...

Using a GPS to double check the speed may not be a bad idea.

I am curious to hear more story about max speed but i won't drive it at these speed in my area.

[BMC]

Originally Posted by mituc Both have programmed errors. The RPM gauge displays the RPM witha linear variation. At 6700rpm real the gauge will indicate 7000. At 3350 it will show 3500. And so on. the OBD rpm is accurate. Same for the speed, even though the actual car speed has one more variable that alters it, the tire size (including wear, keep in mind that a tire can loose 4-5mm from its radius and it's still usable. However, with new OEM tires inflated to spec (I'm saying OEM tires not OEM size tires, not all tires of the same size are equal at the spec inflation) the OBD speed will be the same as the GPS speed and it's calculated based on some sensor in the gearbox that always looks at the rotation speed of the final drive These errors (due to tire size variation or due to the actual error programming) don't change the fact that the car in discussion reached that tacho speed. No, it uses a sensor in the gearbox, but whatever sensor it would use the calculated wheel rotation speed will be the same. That's why we can talk OBD speed instead of GPS speed, to exclude the tire size from this equation. the tacho speed will also have a specific/calculated/programmed variation from the OBD speed, not from the GPS speed. On a gen1 at 155mph/250Kmph OBD speed the engine RPM is 5950 or so in 6th. If the speed limits are removed then at 6700rpm the OBD speed would be 281.5kmph or 176mph. If you have the right mods and the engine car cool properly to do a full pull in 6th then with a rev limit of 7000rpm the OBD speed would be 294kmph or 183mph. 300kmph/187mph at 7150rpm and the holy graal of 320kmph/200mph can be reached with these gear boxes at 7600rpm, but at this speed if the engine is still in one piece the gearbox may start shitting metal bits.

Large thanks. Between you and Jeff23spl, I now have a much better idea of how this aspect of my vehicle functions. Hats off to you for taking the time. Roll safely.

B