bump... If you are tuning cars, read this
bump... If you are tuning cars, read this
Parting 6 speed
Pampena 3.5 Stroker, GTX 2867 Gen IIs, AEM Series2, oohnoo SMIC, DN Hardpipes, FIC 1650s, Walbro 525, aermotive fpr, Dejon intake pipes, Tial Q, Koyo Rad, Samco Hoses, Stoptech 332mm fronts, HKS GT4 Coilovers, Spec 4+ LW, JDM 6 Speed, Billet shift forks, Pampena brace
The next version of Chrome will have two ways to calculate knock sum. The stock setup and an AEM style setup.
Last edited by Greg E; 08-15-2014 at 10:58 AM.
2014 Exomotive Exocet - #101 "shocker yellow" - 1.8L 5-speed 3.9 torsen FMII powered
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99 Solano Black VR4 - #16 of 287 - ground up restoration - sold
98 Pearl White VR4 #54 of 231 - 12.84@105mph - 93 Octane 12.50@107mph - 100 Octane with Chromed ECU - sold
99 Pearl White VR4 #108 of 287 - 3RD place stock car class ECG 11 - Sold
98 Black VR4: 100% stock - totalled by an Illegal 2-12-08
95 White Stealth TT - 11.852 @ 118.25 - sold
95 SSG Stealth TT - 11.981 @ 115.81mph - sold
"I don't actually work on cars, I just talk about them on the internet."
Can someone detail the difference between the two?
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Why would you want the AEM-style knock sensing/mitigation instead of the stock setup? The AEM method of just watching straight raw voltage without the high-pass filter in place at high RPM doesn't seem as "tuned" to the application as the stock ECU is. At the higher RPMs, I'd often see a lot more knock raw which seemed to be various resonances from the engine, valve train, exhaust, etc. which were difficult to tune out. Basically you would just end up cranking up the threshold for knock control, which seems like the wrong approach. The high-pass filter in the stock ECU seems like the correct solution there, and should not be removed from the knock strategy (IMO). We want the ECU to be listening for real knock, not "everything".
-Matt
'15 Corvette Stingray Z51
'95 3000GT Spyder VR4 (11.838@117.5)
Because when a car starts making serious HP (or is just noisy like a stroker) that hardware filtering doesn't work anymore. You get random resonance blips passing thru which spike the raw signal and create false knock sums.
Oh sure, we could just install a different capacitor to do the filtering but that would mean recalling every single ECU sold AND would make the stock 98/99 VR4s obsolete. I doubt Brett and Adam would care to experiment with various caps to find out which ones would work vs which ones would tune out the noises we want.
Its better to let the software do its job.
Maybe I don't understand what you mean by "AEM-style" knock detection.
There's no need to change the capacitor - I'm just saying continue using it because that's what filters out the "background noise" so the ECU hears more clearly the correct range of frequencies to see the knock. AEM doesn't have that, and it kind of sucks. So don't make it work more like AEM in that respect (removing the capacitor circuit (high-pass filter)).
The high pass filter works perfect on cars that are quiet and don't make power. Once you get past a certain point, this setup flat out doesn't work anymore. Since we don't have the technology to monitor individual cylinder pressure with our current ECUs, its back to doing it "the old school" way. Sorry man.
Can you explain more what the alternative strategy is? ie: What are you changing about knock detection in the alternate approach? I only ask because I can tell you that not filtering at all also does not work ideally (on an AEM 3/S car running 10.1s), yet somehow Matt M. managed to go 8's on a stock ECU and piggybacks. Just trying to understand what the proposed change is here, because the stock approach filters out the lower frequencies so there's less background noise in the signal. If that's what is being eliminated, I don't think you are improving the knock detection - you are just going to end up raising the threshold and knock is going to sneak through (and hammer the bearings). Been there, seen that.
"Hey look, zero knocksums and it is pulling like beast... Cool!"
>boom<
Just saying...
If some of the bigger setups are seeing what is determined to be false knock, just raise the knock detection threshold in the areas needed. That's better than removing the filtering AND raising the threshold even higher because now you are hearing even more engine noise (and lower frequencies will be seen as more voltage at the ECU, so will raise the background noise).
If you are adding code to only look for knock on the compression stroke a bit before ignition and a short period after in an attempt to do per-cylinder knock control, then that's probably a good idea (and AEM does do this to an extent). But that's still different than removing the filter.
So back to the original question: What is different about this alternative strategy, specifically?
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