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This is from the 997 forum but I think it's worth mentioning here. Not much difference between an M96 and M97. Engine dyno pulls for a Slakker/Hartech 4.1L. The torque curve might look odd because of the type of dyno and how the engine is run up; it sits at 2K RPMs at full throttle until they are ready to let it rip. I suspect that lets the torque curve look flatter at lower RPMs than it might otherwise. Happy to hear from experts on that, I'm certainly not one of them!
The engine dyno, or a variable load chassis dyno has a lot of benefits over an inertia type rolling road for development and calibration. Being able to hold the engine RPM steady at variable loads or vary the rate with which the engine speed increases allows a lot of granularity you can't get when the engine is just spinning up a drum of a known weight.
That all said, doesn't tell me a lot about what the output will look like at the wheels which, since I am not developing or calibrating anything, is all I really care about..
The conversation is pretty interesting though and for those that don't click the link you posted (I suggest you do), here's my response, I'll definitely be following along that thread.
I find it very interesting that even with the high octane the ECU is pulling timing. It would seem kind of amazing to me the engine at the type of normal octane limited compression ratios and cylinder pressures I would assume this engine is running is actually getting into any knock activity worthy of timing degradation unless the timing upper target is something bordering on unreasonable. I guess I need to do some research on combustion analyzers to conceptualize the 1 Bar/1K RPM you reference.
I wonder if the knock sensing strategy is an area worth seeking improvement.
They were probably using semi-solid engine mounts, thus causing the knock sensors to kick in.
The data from Brandon is from his engine dyno. I guess my position is if the knock is being observed from either engine mounts or dyno mounting, reducing timing as a result is needlessly degrading performance.
Here’s some good context on knock control strategy using an aftermarket ECU.
Inherent harmonic imbalance of the m96 engine needs soft compliant mounts to help quell its built in harmonic vibrations. Thats probably part of the reason for DMF and extra soft engine tranny mounts.
And some m96 engine builders recommend and use an added harmonic type front pulley to help quell damaging m96 vibration.
Thats probably why we hear so many stories of changing engine/tranny mounts to anything but oem and now new harshness/vibrations are present. Wouldn't be surprised if those create a timing/HP pull also....
Peak 305.52 horsepower and 296.98 wheel torque. If someone knows what the typical drivetrain loss is, please let me know. I figure somewhere between 10-20%.
More concerned with AFR and drivability around town so didn't go hard core on the tune.
I am really pleased with how the car drives now. Power delivery is so much smoother than it was before the tune. Engine had been running lean, hence the early shutdown. So yeah, I'm glad I got it sorted. Peace of mind for sure
We discussed headers to get a bit more power out of it but doubt I'll do anything else outside of enjoy it. I just know power and torque went up.....and it won't blow up!
First aborted run showing AFR. Just seeing this made me glad I was getting it tuned properly!
Peak 305.52 horsepower and 296.98 wheel torque. If someone knows what the typical drivetrain loss is, please let me know. I figure somewhere between 10-20%.
More concerned with AFR and drivability around town so didn't go hard core on the tune.
I am really pleased with how the car drives now. Power delivery is so much smoother than it was before the tune. Engine had been running lean, hence the early shutdown. So yeah, I'm glad I got it sorted. Peace of mind for sure
We discussed headers to get a bit more power out of it but doubt I'll do anything else outside of enjoy it. I just know power and torque went up.....and it won't blow up!
First aborted run showing AFR. Just seeing this made me glad I was getting it tuned properly!
Awesome to see another home built engine ! Really enjoy following your thread and am happy you're pleased with the results.
Also, really cool you sharing some of the progression from pre to post tune, agreed looks like it was well worth it if not required (I'd say both).
04-23-2024, 11:32 AM
