Knock

[iwantatta]

I am trying to get rid of engine knock that is showing on my scanmaster. I've tried adding 6 gallons of 91 with 2 gallons of xylene and i'm still getting knock. My car is running on the stock chip and i'm getting anywhere from 5-10* of knock on the highway runs at WOT.

Still have the stock boost gauge and its showing about 16-17 psi. Its hard to tell exactly though.

The car has recently passed california smog so its running okay.

Somethings i'm considering doing are:

Using a thrasher chip that i have to see if it has any effect. I'm currently running the stock thermostat 190. Should i replace with a 160 before adding the thrasher?

My throttle position senser may be a little low for WOT. Currently set up at 4.3v. My idle is okay at .42. The problem i have at WOT is that i can't position the sensor anymore to get more voltage at WOT. According to gnntype it may need to be filed down to allow for more movement. Could this be an issue?

Or find a place that sells VP racing fuel and just fill up the whole tank to see if it has any effect?

 

[MaxVO2]

Originally posted by iwantatta
I am trying to get rid of engine knock that is showing on my scanmaster. I've tried adding 6 gallons of 91 with 2 gallons of xylene and i'm still getting knock. My car is running on the stock chip and i'm getting anywhere from 5-10* of knock on the highway runs at WOT.

****The stock chip is too aggressive for todays gasoline. Turn down the boost, or get a more modern chip burned for your combination.

Still have the stock boost gauge and its showing about 16-17 psi. Its hard to tell exactly though.

****Get a better boost gauge. 16-17psi with 91 octane gas is too much boost for most cars. The 2 gallons of xylene certainly help, but who knows if you really are running 16-17psi, and not something much higher.


The car has recently passed california smog so its running okay.


*****It passed a smog test, and that certainly is important, but this may not translate to running ok at WOT.

Somethings i'm considering doing are:

Using a thrasher chip that i have to see if it has any effect. I'm currently running the stock thermostat 190. Should i replace with a 160 before adding the thrasher?

*****Putting in a 160 thermostat is a popular upgrade on these cars, and can help reduce knock somewhat. It will probably not eliminate 5-10* knock by itself. The Thrasher chip may also be too aggressive for your car if it was made more than a few years ago. You can try it, but for reasonable cost, there are several chip makers that can make you something that will be spot on to your combination and needs. No guesswork.


My throttle position senser may be a little low for WOT. Currently set up at 4.3v. My idle is okay at .42. The problem i have at WOT is that i can't position the sensor anymore to get more voltage at WOT. According to gnntype it may need to be filed down to allow for more movement. Could this be an issue?


*****Things have come a long way from the days when people were filing TPS sensors for more clearance. TPS with respect to power enrichment is based on % reference of TPS at startup as well as other things like LV8, airflow, etc.. These other values contribute and act as checks to insure proper fueling. As long as the throttle blade is fully open (check if not sure), and TPS is over 4 volts, you should be fine.



Or find a place that sells VP racing fuel and just fill up the whole tank to see if it has any effect?

*****It's great that you have a Scanmaster to give you valuable information, but a good boost gauge is also a must. The VP fuel will probably completely eliminate the knock, but it would probably be cheaper for you to just get a better chip.

Hope this helps

Billy
Montgomery Village, MD

 

[iwantatta]

I have a 92 thrasher chip that i have not installed yet. Is this good enough to try even though i have the stock thermostat in there?

 

[MaxVO2]

You can try it. I would turn the boost down just to be safe, but it's your car.

If and when you see knock retard, let off the gas. The 190 thermostat isn't helping you, but even if you change it out, it probably won't fix things enough for your knock to go away. Just get a better chip, or get used to fixing whatever breaks.

Billy

 

[72firebird]

From what it sounds like your car is completely stock. Do you have ANYTHING done to it? This include subframe connectors or a downpipe. It might be possible that you're getting false knock. Also if everything is stock try just using 93 octane and see what it does. Pressure check all your cylinders and if one is more than like 10psi off form all the other then I would check the injector. How many miles are on the car? There are many thigns that can play a factor into knock including just a bad tank of gas.

 

[Swede2]

When I was completely stock I had knock to... The stock chip is very bad, it was designed for the old gas we had back in 89... The gas has now been "worser" than before and that does all the knocks.

The Trasher 92 is no problem to run on a stock thermostat, I did it. If the problem is chip related you will see a decrease in knock retard if you change. With 160 thermostat and Thrasher 92 I was able to run about 18 psi with less than 2.0 knock retard.

Daniel

 

[iwantatta]

From what i know the car is completely stock. I just bought the car a few months ago from chicago. It only has 28000 miles on it.

I always let off the gas when i see the retard shown and it falls back down to zero. Don't drive the car very much because its my second car and i don't plan to put many miles on it. At the same time it gives me a chance to fix problems like this without being in a hurry.

Wish i could just pump in 93 but all we get here is 91. I have found a place that sells VP 99 octane at a i little over 7$/ gallon. I may try this also.

 

[iwantatta]

Should i check the fuel pressure before putting in the Thrasher 92? What should it be?

 

[TT/Ameasap]

Xylene will put you around 100 octane. The thrasher chip is fine for a 190 thermostat. Turn your boost down and pull some fuel out....o2's should be .750-.820's @ WOT. Your TPS set to 4.6 @ WOT or real close. Check BL's and make sure you are at 128 +- 10 or so.

If KR goes away while you are flooring it, then it most likely is false.

If you floor it and it stays for the whole time, you have the real KR.

HTH
Bo

 

[trading t/a]

Where is the knock occuring? If it's afalse knock some chips have false knock ignore for the first part of a wot run.....
HTH!

 

[iwantatta]

The knock occurs at full throttle. At times it seems that i can get away with no knock and a good amount of boost (enough to pin me back in the seat but not WOT). It seems to fluctuate with how hard i step on the gas. Haven't quite narrowed everything down as i don't want to experiment too much with the knocking.

 

[MaxVO2]

If you plan on keeping the car for a while, preferably running... Rather than trying to make the Thrasher 92 chip work with 91 octane gas and some xylene - get yourself an accurate boost gauge, and a more modern chip designed for todays gas, and live happily every after.

Experimenting without having basic tools like an accurate boost gauge is risky. It's your car, and do with it as you please, but keep in mind plenty of folks have blown their engine up overboosting it on a nice, crisp and cold day.., and it would be a shame for you to end up having a very bad day on your 28000 mile car because you were trying to save a few $$ on a chip better suited to your driving needs, and to the lower octane fuels in your area, that are probably oxygenated as well.

Good luck

Billy
Montgomery Village, MD