Can too much timing cause knock?

[RoasT BeeF]

Read this written by another member on a different forum and tell me if you think he is full of BS or if this is really true. Its the first time I have heard such a thing but I am kinda believing it and wondering if its my problem. My timing advances like up to 45 on 3rd gear pulls and I get about 30 counts of knock no matter what I do.


"The ECU will pull timing when there is knock. If you are tuned, this will not happen.
But here is the catch... Too much timing will make you knock, and then the timing is pulled back further than it should be for the best power. Too little timing and you aren't making as much power as you could be.

It's a big balancing act with the SAFC because when you remove fuel, you get more timing (due to the altered airflow signal).
As you lean it out you may not only knock because of less fuel, but because of more timing.
For instance - In a case where the timing is causing the knock: Lower the base fuel pressure a bit, add more fuel on the SAFC, and you end up with the same amount of fuel -- but less timing!
In case you're wondering why -- it's because the timing curve is a slope from high to low when plotted against airflow. If you increase the airflow signal to add more fuel, you are lower on the timing map."

 

[Sk8er07999]

Yes I could see how that could be true but something I would think about is this. Think of a hose with a small nozzle on the end (450cc stock fp). Injectors work perfectly and mist good optimising a/f ratio (max efficiency, max power). Now tak the same hose but put on a bigger nozzle (bigger injectors). Now at the same fuel pressure the injectors may not mist properly. So inorder to get the injectors to function properly you would need to raise fuel pressure. This is just what someone told me. My car seems to run great with a walbro 255, pte 780s, and aeromotive fpr set at 45psi at idle with vac line off. But I have the same problem. Tons of knock (up to 30 counts) in boost but I still have lots of timing and lots of power. Keep in mind I still have the 14b and its running at 16-17 psi o2's are reading extra rich. .91-.93. To me the next thing I will do is get a wide band. It's the only way to know exactly what is going on. Or take the car to the dyno and have them use theres! Thats the other option. I believe that this is what the guy is describing in your post that no we are not knocking because of detonation, we are knocking because we are getting too much timing. I don't know but I hope to find out soon.

 

[Kevin Jewer]

Everything in the quoted text is correct. These days the ticket is to get a chip with "injector compensation." This allows you to keep the AFC near 0, so timing isnt thrown out of whack. If you want more timing than the ECU is giving you (on high load timing maps its pretty low, 17 on a 2g) you can add it in with the cas (1g only, or 2g with 1g cas).

And to answer the subject line, yes too much timing will cause knock, and it can easily ruin motors. How much is too much? Thats the tricky question, for each setup.

 

[Sk8er07999]

hmm intresting. too bad I don't have an eprom...

 

[RoasT BeeF]

Thanks for the info 95GSXracer. Looks like its time for that chip indeed. Man I swear just when I think I have it all figured out...........well I just dont.

 

[Kevin Jewer]

Same here! No one has it all figured out The important thing is to be able to swallow your pride and learn what needs to be learned, which you seem to be doing already.

 

[TurboDSM90]

Same here! No one has it all figured out The important thing is to be able to swallow your pride and learn what needs to be learned, which you seem to be doing already.

AMEN!