knock at higher rpm

[RauPower]

Hi!
I am from Germany and we tune a lot of European vehicles. Since about 1 year I use HPT and it works great! There is only one problem I have and I can't figure out what's wrong.
The first 2 cars I did were Corvette C6 2008 with LS3. One without cats the other one stock. The third one I am working on right now is a Covette 2002 C5 with LS1, 10mm bigger throttle, headers, sport cats and complete exhaust, ram air filter box.
I can increase timing between 10 and 18 (!) degrees around 1500 - 3500rpm - no knocking and runs great. lots of tourqe gain of course. BUT, from 4000 - max rpm there is even 1 degrees too much!!!??? Of course no more power gain and stock hp!! Even when I play with the AFR up or down - there is always the same power and same knock situation!! And I can read that mixture really changes at the wideband reading!
Weather is cool, oil temperature 110 Celsius.
ALL THREE CARS AND BOTH ENGINE TYPES REAKT THE SAME WAY?
Any idea from a pro??
I add the maximum tune (LS1) I can use with best pump gas it get's for street use.

Thanks a bunch!!
Tom

[WS6FirebirdTA00]

Mid range timing is REALLY high. What octane fuel are you running?

What is your fueling doing? Incorrect fueling can also cause this, not just timing.

It could also be false knock

[RauPower]

100 (German) oktan!
Midrange is OK, till about 4000rpm nice torque - no knock at all!
4000rpm dead on you can add what you want and even 1 degrees will show knock! Even stock is knocking 2 degrees already! I saw that on all 3 Corvettes so far. LS3 and LS1!
Fuel map is stock and even if I go richer it just runs not as good and knock stays the same!

Thanks
Tom

[motorheadmike]

*Note I am at the office and can't view your files.

Okay so what you are really working with here is 95 octane in North America (baseline reference point for most members here). http://www.audizine.com/forum/showth...ngs-in-Germany

That said you are seeing knock as the engine(s) reach Maximum Brake Torque (MBT) where an engine needs the least amount of timing to produce power; and given that you have added significant timing below this point it is safe to assume that there is some carry over into MBT and beyond to the redline. When you are experiencing your Knock Retard (KR) event there is a strong likelihood that the decay rate of the timing retard is slow in putting the timing back in as you move to the redline.

I have noticed in our vehicles that less timing is preferred at both MBT and in some cases redline, and we have picked up power over the stock tune based on this alone.

I would suggest that you do the following:

1. Confirm your octane, or boost octane to ensure that it isn't a bad batch of gas or a false reading;
2. Put the timing back to stock and add moderate amounts incrementally until you see KR;
3. Ensure that both your MAF and VE tables are correct by tuning them.

Remember that richer AFRs and additional timing don't always mean more power. You may very well find that small adjustments from the stock tune is going to gain you the most return, and that in some cases more power just isn't available due to other outside variables.

[RauPower]

Well, fuel quality is OK, tried couple different gas stations and I found the same problem on C6 2007, C6 2008 and C5 2003!
On my first C6 LS3 I had up to 18° advanced between 2500 to 4000 (went back to 16° though). The second LS3 took 15° and this older LS1 with headers and 10mm bigger throttle body takes 12°. All at exactelly same rpm range!
All of them show the same issue, starting at 3600rpm till about 4800rpm. There is not even 1° possible, sometimes it was knocking already 1 - 2° with stock mapping! At this range it perfektly normal because it's where the highest tourqe is - I know that. But even higher, there was not even 1° possible. At redline I never add anything at all, since a advanced ignition works against the upmoving piston and slows down the crank.

Why is it that so many guys have between 4500 and all the way up to redline about 10°?? On some I understand it if you have a really big cam in it - but stock engines?

I also noticed that NO MATTER if I go slightly richer or leaner - there is NO power gain, even if I tune just different rpm ranges!

Now I found some thread somewhere at the net (not here) that I have to play with some knock retard rettings and ... I can go about 5 - 6° up without knock. Can't hear a pinging sound either. Fuel adjustments still suck.

BTW, after my tune on my first C6 LS3 with 16° and stock ignition from 4000rpm onwards, the car runs great and uses 3/4 galone less fuel!! And that guy floors it all the time!

Tom

[superwagon]

why do you have your low octane table set to 24* across the board?

[RauPower]

:-)
Sorry, I just sent the file without double checking it. I usually set the low octane table across the board to -5° to the values in high octane.

What are you guys thinking of this mod??
With this I was able to get a more advanced spark at high rpm!!

http://forums.corvetteforum.com/c6-t...er-rpms-2.html

[RauPower]

Here is my latest tune...

What would you usually change when you upgrade to a 10mm bigger throttle??

Tom

[motorheadmike]

What are you guys thinking of this mod??
With this I was able to get a more advanced spark at high rpm!!

http://forums.corvetteforum.com/c6-t...er-rpms-2.html

Like I stated: decay rate was factory slow. I confirmed this when I got home last night and saw that this and your VE table were stock.

I would really stop playing with the timing and start looking at the fundamentals; tune your MAF and VE tables before continuing.