Why am i knocking? and how to fix it

[j5819n]

Ok i have a 1990 talon with evo 560cc injectors, walbro 190, and afc and 2g maf and i am only set at 13 pounds right now and i am still hitting like 18-20 counts of knock at about 5000rpm's to redline. I have enough fuel to run 13 pounds and it is not high intake temps and i am running 92 octane fuel. I have talked to a few people that said to retard the timing how does that stop knock and any other ideas?

 

[qiklitltsi]

Well its kind of hard to tell but if you had some sort of log to show us it might help us figure it out. One thing im woundering is what you have your fuel trims at.

 

[j5819n]

they are at 0 all the way around if i did it right because the 560 are 18% bigger and the 2g maf flows 20% better and i didn't want to lean it all the way so i thought zero would be pretty good is that right?

 

[kiddsm95]

Your knocking because your car is running too rich. Take the stock injector size and divide by the 560's (ie. stock 2g's: 450/560 = -20% on the SAFC for a 2G car). I agree with QLT though, you need a logger to determine what's going on in your engine before you think about touching the fuel trims.

 

[allwheelTSI]

Your knocking because your car is running too rich. Take the stock injector size and divide by the 560's (ie. stock 2g's: 450/560 = -20% on the SAFC for a 2G car). I agree with QLT though, you need a logger to determine what's going on in your engine before you think about touching the fuel trims.

Running too rich does not cause knock.

 

[spoonman]

+1

How do you know it is hitting that much knock?

 

[j5819n]

i have a pocket logger i forgot to say that i can run logs but i can't get the numbers onto my computer. And it shouldn't be -20% i have a 2g maf on a 1g car.

 

[rb25det510]

Running too rich does not cause knock.

ther is a point to where you start knocking if your to rich but were talkin like reallly rich in order to reach it.

 

[Jetrosr]

Your knocking because your car is running too rich.

I am assuming were talking about preignition/spark knock. Nobody ever knocked from being too rich, but lean will knock all day long.

 

[2gGSX]

I am assuming were talking about preignition/spark knock. Nobody ever knocked from being too rich, but lean will knock all day long.

Incorrect. I've witnessed it myself.

ther is a point to where you start knocking if your to rich but were talkin like reallly rich in order to reach it.

A friend of mine ran 550's with 0 compensation without knowing what he was doing (albeit on a 1g MAS) and knocked to hell.

 

[kiddsm95]

Yes preignition, sorry didn't mean to confuse the two. My car had a bad case of preignition with the safc set at zero across the board.

OP: The -20% was just an example of what the fuel trims would be like on a 2g car. This will differ on your setup since you have a 1g with a 2g maf. Take a log of what's going on then do a search for how to get your info onto your pc and post the results.

 

[j5819n]

i will post a log after work tonight if i can get it on my computer and does anyone know about retarding timing to fix knock? i have searched and i don't really understand it?

 

[TSiAWDRatlemstr]

I believe that the guy saying that you need to go negative on the AFC is correct. The 20% more efficient 2g MAF and the 20% more fuel do not cancel each other out. You need to compensate for the extra fuel going in by leaning it out. -20 on the AFC (or whatever it comes out to) should be a similar setting to the stock injectors. You can only adjust base timing on your 1g and you never want to move that from stock. Once you stop all of that excessive fuel dumping, your timing will be good. The ECU does all of your timing adjustments for you unless you have other tuning options such as DSMLink that allow you to mess with timing and fuel control independently. Try it out and I bet you will be suprised. Just my two cents...

 

[90tsiPA]

If the head was ever rebuilt or even been off the car the ignition timing might need to be reset to stock.
This site shows you how.. make sure you unplug your datalogger when doing this
Engine Timing

 

[j5819n]

alright so what do you guys think my afc settings should be?

 

[kiddsm95]

First determine what your stock injector size is for a 1G, then follow this guide.

http://www.dsmtuners.com/forums/articles-tuning-ecu/58403-definitive-piggyback-tuning-guide.html

 

[j5819n]

i already know the stock injector size it is the same for all dsm's besides the automatics. They are 450cc and i have evo 560's so that means they are between 18-20% bigger any more help?

 

[spyderturbo007]

I'll post this up one more time just in case you missed it.....

Post a log!

 

[64_Frankenstein]

Your knocking because your car is running too rich. Take the stock injector size and divide by the 560's (ie. stock 2g's: 450/560 = -20% on the SAFC for a 2G car). I agree with QLT though, you need a logger to determine what's going on in your engine before you think about touching the fuel trims.

I have the same problem. Its very rich when the car get up and go and 20 to 43 counts of knock below 3500 RPM. Im going to get that fix before I trouble shoot the knock sensor.

 

[Kaedo]

A lot of people seem to be confused as to what knock is. Pre-ignition and knock, or detonation, are two totally different things. One is the combustion of the charge before the spark plug fires (pre-ignition) and one is a spontaneous combustion of the charge after the spark plug has fired (detonation/knock.)

I highly doubt you are suffering from pre-ignition, as if you were you wouldn't really be worrying about your fuel trims right now (you would more likely be worrying about an engine rebuild.) As to your knock problem it makes sense that you running too rich can be causing it, as there is a lot of unburnt fuel left in the combustion chamber that has a chance to detonate after the initial combustion process. So fix your fuel trims (sorry I can't help you with a the AFC, I've never owned one) and if that doesn't help check to make sure your timing is correct. You should actually check your timing anyways, it can only help.

For good info on what knock is and the difference between it and pre-ignition, I highly recommend this