Growlss

I’ve been having been experiencing audible detonation under WOT near the top end. I just purchased Autotap with EFIlive and have been doing some logging. What things should I be looking at? I had did a run at the dyno shop, which confirmed that it was detonation, and they suggested I put in a low temp thermostat and do an 3-stage induction cleaning. I live in southern California, so the highest octane gas I can buy is 91. I’ve tried some octane boost, with no luck. Any ideas or suggestions?


Here are my dyno results:
Dyno Results1
Dyno Results2
Dyno Results3

chpmnsws6

check injector duty, put a fuel pressure guage on it and see if it is dropping fuel pressure that much.

if its not dropping much FP and your injector duty is hig, you might need new injectors. atleast thats how it is in the dsm world that i've carried over

ChickenScreamer94

Replaced the fuel filter lately? Just a thought. BTW, if read on the fuel octance booster, it says points, and in the crude oil world that mean .1 NOT 1 point. So if it says ten point that is .1 x 10 or 1 point

Other than replacing the filter, maybe you have massive carbon build up? Try some kind professional intake cleaning, like the one you mentioned.

JimMueller

Things you could try:

- One range colder on the spark plugs
- Cooler thermostat and matched PCM reprogramming
- Replace knock sensors
- Install the LS6 PCV system, and/or a catch can & inline filter
- Flush the intake system with SeaFoam or GM Top End Cleaner, then perform an oil change
- Replace the fuel filter

Growlss

Thanks for your suggestions, i've got a friend at a dealship who said he can do the induction cleaning. I just bought a low temp thermostat that I'm going to put in this week. I will change the fuel filter as well, it can't hurt anything. I'll let you know how it turns out.

Thanks for you help, Will

Flat_Tire_

I think I may be experiencing the same problem .. only happens every once in a while though .. sorry to be an idiot in the matter .. but does detonation sound similar to gravel getting sucked through a vacuum cleaner?

JimMueller

Yes, that is a good analogy.

Flat_Tire_

Roughly, what does it cost to get an intake cleaning? .. What problems can be caused by detonation, other than a bad dyno curve?

Growlss

That is a good analogy, gravel through a vacuum cleaner. That’s exactly what I am experiencing; I have noticed it doesn’t seem to do it as much when it’s a very cool night. This leads me to think it’s got to be a combination of temperature and octane. Once I put in the low temp thermostat, and get some good octane boost, hopefully it will cure it.

MY91Y84

even though i have a LT1 motor, its all the same..

when my motor is operating temp i get no spark knock...when it gets hot shell ping a little...10.5 C/R and i use nothing but sunoco ultra 94

its actually kinda funny...ill sit and idle for a few and she start getting warm...then i get on it or w/e and itll knock for a few seconds and once the air starts going into the engine bay itll stop knocking and instantly pick up 30-40 hp lol...


it kinda sucks you live in cali..(gas wise)...im sure with with some 93 or 94 you wouldnt have any problem...and in MHO a lower thermo temp is more of a bandaid....since your into tuning as is..why dont u just pull out a little timing on top?