[Fast_Freddy]

Originally Posted by Td-d

I'm going to tactfully avoid any potential landmines in this thread, but I have to ask some questions:

I'm not sure what exactly you mean by this? The OEM knock control strategy is well understood: http://www.romraider.com/forum/viewt...hp?f=25&t=1840 - but I'm not sure what the statement above means?


I'm not a tuner nor an expert on tuning. What I think I understand about general Denso ignition timing advance strategy was learned from Toyota and Toyota tuners. AFAIK the ECU pretty much advances timing until knock is detected at which point timing is retarded until knocking stops at which point timing is advanced again until knock is detected and so on. How else could they achieve optimal spark timing across the wide range of fuel grades, altitude and weather variations the car will be subjected to?

Thanks for the Romraider link. Great info that I had not seen before.

And I think people forget that we drive non-luxury vehicles (I hate the term econo-box) where costs and functionality are always a trade-off. Knock sensors are far from infallible - that's why any tuner worth his salt will use Det cans and not just rely on the ECU knock parameters. There is a complex set of logic around noise filtering that make the knock sensor work to the best of its ability - but always keep in mind that once you tune a vehicle, you are stepping outside of the margins of safety that the OEM put in place, and potentially the specifications of any piece of hardware on the vehicle.


You're not suggesting that our knock sensors or ECUs are cheaper versions than those found in Outbacks and Solaras? I don't agree with that. I do agree with your other points but would like to add that this is true for any tune, not just JV. Speaking of which, aren't there literally hundreds of people running JV tunes out there? Any reports of tune-related engine damage?


Should be interesting - would not surprise me if there is knock, on poorer grade gasoline. Some JDM subarus that landed up in the Australian market were notorious for severe knock, from the factory - since they were set up for higher octane fuel.

Bottom line is that knock control is a safe-guard - but a relatively knock free tune to start with is preferable. Prevention is better than cure - and if you're logging knock, especially in higher load areas, it will eventually catch up with your engine.

I may be wrong but what I learned in the 2AZFE tuning world was that the biggest problem with high KC was that the ECU pulled too much timing before adding it back which lost some power. It was best to minimize the amount of KC but not to eliminate it. The only case I know of where a N/A 2AZFE was destroyed by knock was when the knock sensor came loose on a bone stock engine and it self destructed due to the OEM timing strategy. My own turbo experiment yielded gains of 125whp/125ft lbs at 6psi with nothing but 20% larger fuel injectors and 93 fuel for tuning. No piggyhack, no ECU flash, nothing but a AFR sensor signal modifier for AFR enrichment while in closed loop. I raced that engine many times and daily drove it for over 40k miles without any issues.

Originally Posted by vgi

I recon just leave the guy alone with his awesome +17WHP, +10lbs TQ and no TQ dip tune, it's his car and he knows better anyway.

Don't be an ass. If you're so sure that I'm wrong, please explain why.

Originally Posted by brn12345

Yes I have logged on the following:
-Stock tune on pump gas (95 RON but I have my doubts)
-Generic tune on pump gas (95 RON but I have my doubts)
-Generic tune on VP Motorsport 103

I can tell you that on both the stock tune and the generic tune on pump gas that the car does exhibit knock. The IAM in both cases moves to 0.2-0.3 in about a day. I have extensively logged this and can say that there is no knock on high load / full throttle runs. All the knock logged is in the part throttle normal cruise area and throttle tip in which results in overall timing being retarded. Fine Learning Knock Correction (as a table) is also being populated which says that the car is actively pulling timing.

On the Motorsport 103 IAM is rock steady at 1 and does not change. There is no knock what so ever and the FLKC table is all 0's. The car is noticeably quicker, smoother, and more crisp. Exhaust tone is sharper and the motor screams in the top end. If I could I would run this fuel everyday as this is how the car is supposed to run.

From this I will make an assumption that the stock tune is aggressive in low and part throttle (maybe for emissions?) and does knock when we have bad or low octane fuel. This results in the global timing to be retarded (due to IAM). As a compromise, I have adjusted the Advance tables lower and increased the Base timing tables in the 6000-7700rpm range. What this allows for is maximum power at full throttle even when IAM is very low.

If anyone wants to see these logs kindly PM me.

Great info. Thank you.