So I've been tuning my mates car for him here and there for about a year now as he's worked his way through various mods. This car has always had very inconsistent knock, usually around the 3000-5000rpm mark. No matter how much I've messed with fuel/timing it just pops up from time to time. E.g. one log clean, another full of 1-3 counts of knock around that area or sometimes even up top. This is tuning on Aussie pump 98 (similar to your 93).

We've recently started tuning it on Ethanol (~E70), which I thought would be a great test with the higher octane to see if the knock was fuel/tune related. We've done quite a few logs now dialling in the tune and the random knock is still there.

So I'm wondering if it's time to mess with the knock tables? I've never done this before on the handful of cars I've tuned, so thought I'd ask here for opinions.

Here's a couple of examples of the knock I am seeing (and not seeing) on pump fuel and ethanol. As you can see, timing is nothing crazy and AFR's are about where they should be for the fuel (I think!).

Pump 93 knocking:


E70 knocking:


E70 clean - this was back to back with the above run.


Car details:
2001 Evo 7
Evo 9 turbo
Invidia 02 + full exhaust
Intake + pod filter
TurboXS BOV
Grimmspeed 3port
Tomei PonR 270 cams
FIC 1050s

 

I would say its not really based on your timing numbers. Valvetrain noise (lifter), rattles from exhaust touching the tie bars, leaks, etc. can cause phantom knock. Voltage looks clean and the timing is low enough for a stock turbo combo that it should be fine on E70.

 

If the balance shaft is out of phase or deleted you can get noise as well. A little compressor surge or BOV noise will get picked up in some cases.

 

Aaron, can you elaborate on what you mean by "voltage looks clean" please?

 

2v and lower, the areas where it had interpreted knock before actually had lower voltage, no large voltage spikes near the area that had "knocked" before. 3187rpm in the second log did have a 2.3v spike where the run before was 1.7 but it also had pulled timing or was about to in the prior run.

 

Thanks as always, trying to learn as much as possible!

 

Thanks very much for the response! So based on what I've read on here, all I should need to do is up the 'Knock Multiplier' tables by a couple of points and see if the phantom knock goes. Is that correct?

My settings are currently as follows: Low=13, Mid=18 and High=20, which I assume is stock.

Should I up all 3 or just the low and mid for now? It does occasionally throw random knock up top, but nowhere near as much as the 3-5K mark.

Is it worth messing with the 'Knock Load' table too?

 

That was an interesting comment for me to read, that I don't think anyone made on any of my threads about knock. I deleted the balance shafts, and once the build was done I essentially have the kind of knock the OP is referring to. Sometimes clean, and then sometimes 3's and then sometimes weird jumps from 0 to 25 and then back down, and finally smooth up to 8s and back down. I have tried everything and nothing I seem to do turning wise seems to get rid of it entirely. Reducing timing does sometimes seem to manage some of it, and then richening up the AFR helps too, and right when you think you are on the right track, there will be one pull or track session with massive numbers, so you can just back out all those adjustments and call them a waste of time.

If the BS delete is causing this, that would be awesome, as its another self induced craptacularness.

A follow up question to that, if on E85, which I hope to eventually be, do you tune by the knock sensor at all anymore, or just by max best torque production/measure?

 

No, you definitely don't tune by the knock sensor on E85. You can push well past MBT and cause serious damage before you will see knock. It's a great fuel though - I only just made the jump myself and wish I'd done it ages ago

Sounds like with your BS delete, you could do with some adjustment to the knock tables to see if it helps.

 

I did mess with them a while back. I had a thread where I was getting help on that, and I started reducing the sensitivity and I didn't get the kind of clean pulls I was hoping, and I was getting nervous I was masking the problem. I didn't consider the BS delete being the root cause though.

On the E85, from a timing perspective you know the timing is maxed, or efficient if you set it and don't get more torque from the same rpm and load value. So that if you increase timing and the values on the dyno, or your virtual dyno software flat line, then you should go back a couple degrees and call it a day, or call it max best torque at that value. Correct?

Propel, get it together, and get a station near my damn city!

 

OK no worries. Sounds like you've been wrestling with the issue for a while then. It's annoying when you can't get a consistent clean set of logs for sure

And yep, thats pretty well the E85 tuning process in a nutshell from what I've seen. There's a couple of good threads on here which cover the tuning process pretty well.

 

I have found that 20/21/22 on the multiplier and then watch the knock voltage close is more than safe enough when done properly. The main thing to keep in mind is timing sweeps (pull -2 and see where the car loses and where it doesnt) to determine if you are too aggressive. I leave timing down low nearly pumpgas level and then really only start to ramp it up at 5500 and above, not exceeding 18* out the top.

 

That's great info. I really appreciate it thanks. I gave him one to test (before you responded) with 15, 21, 22, so will see how that goes. Sounds like I will need to bump up the low a bit more though. I'll keep a good eye on voltage and watch for bigger spikes.

Good tip on the timing sweep too This car is currently running very tame timing to about 5K where I've started to ramp it up. Currently we're at 7* at 5K, 11* at 6K, 15* at 7K and 17* out the top. This is at about 25psi tapering to 22 at redline. We're seeing noticeable gains with each incremental update, so looking good so far.

Interesting you mention not exceeding 18* out the top... My own car is running 19* at 7K and 20* out the top Mods and results in my sig. Perhaps I should go back and have a better look. Could be on the limit?

 

is this method good for 93 octane tuning or you guys are talking about E85 only ?