I have a question that relates to the tune of my car. (I just got cams a couple weeks ago, we tuned for it, but then I found out I had 4 boost leaks. After I fixed all of those, we began re-tuning and are just now beginning to re-dial it in.)

If I floor my car at 3000rpm, ill start knocking & the knock carries through the entire rpm range, seen below.



Now, when I floor my car at 3500rpms, I get nice & smooth power. It really puts you back in the seat! Below is a picture.



Now I asked my tuner what the deal was? He mentioned it was because of my bigger intake 280 cam. Why does it matter what rpm I get on it at? I hate it when I floor my car at 3000 (I usually get on it around 2750ish whenever I do get on it) and I HATE seeing my KnockLight light up every time I do & carry on throughout the powerband... but when I go at 3500, everything is so much faster because its not pulling that timing & power is very smooth. Someone please explain to me why this happens? I am really interested in learning how the car works like this.

 

pulling timing? it looks like you have no timing at all to begin with...

your only at 2deg advanced at 4000 rpm...

if you are knocking with 0 deg of timing, then you need to turn the boost down.

 

I getting -1 and -2 degree timing at max knock on the first log.

 

Your problem is in the 3500 RPM high-load range. When you go WOT at 3500 RPM, you don't hit the high load cells at 3500 RPM. When you go WOT at 3000 RPM you hit 280 load at 3500 RPM. The reason your knock carries through is that the knocksum doesn't go away as soon as knock stops. Instead, it tapers off slowly. You may be a little lean during low RPM spool, or you may have a little too much timing right at peak boost. If you can get rid of that 9 knocksum you won't have any problems through the rest of your pull. I can tell you that if I were tuning my car and saw knock like that I would consider the tune bad and start making adjustments. It should not be something you just live with.

-Paul

 

you probably weren't tuned from 2500 + . Most do the standard 3000,3500rpm+ tuning. Usually, on boost is when one steps on it. 2500/3000rpm+100% TPS = dyno pulls.

 

Hmm, I see. Ill talk to my tuner & tell him I want that area tuned.

 

You won't know anything until a WB is used and what boost is that at anyway?

Knocking like that above is not good at all so don't drive it hard until you find and fix the problem or else you will be making one huge upgrade.

But anyhow, pulls starting at lower RPM can cause knock more and knock causes heat which may explain why it didn't occur at normal pulls at higher rpm

 

What RPM do ya'll recommend starting at?

We tell our customers to start at 2500 RPM to avoid this very issue.

 

Another vote to get a wideband in to your log to see what the AFR's are during your pulls. This will also give you piece of mind and help get you closer to finding the real issue.

 

I tune:
2500rpm
3000rpm
3500rpm
4000rpm

To pretty much touch all bases. I spend the majority of the time between 3000/3500rpm when tuning my car.

 

I typically start with a pull at 2000 RPM to get the initial tune set up, then start pulls at every 500 RPM from 2000 RPM all the way to ~6500 RPM just to make sure the intermediate load cells are ok all the way up. I've had tunes that were great starting at lower RPMs, but logging a highway merge saw knock while going WOT at 5500 RPM.

-Paul

 

I have the same cam combo that you have. Are your cams set at 0/0? The only time that I have experienced knock at 3000 RPM during throttle tip-in, is if my intake cam is advanced to either +2, or, +1. I don´t know how your tuner can categorically state that the knock is due to the HKS intake cam.

Melon has experience tuning Evos fitted with HKS 280 cams. I´m almost sure that he has these cams installed in his personal Evo. You may want to consult with him.

 

Sorry, I double posted once again..Nyuck, Nyuck.

 

his cams are sitting on stock gears so 0/0.

 

Yeah, my cams are set 0,0.