Hi guys I am trying to figure out the cause of my detonation. The truck was dyno tuned and the timing is set to a VERY conservative 12 degrees and the A/F is between 11.6-12.0 throught the RPM range and actually goes to mid 11's in the upper RPM range close to redline. After the dyno tune we road tested it only to discover it was detonating at the top of second gear and into third gear under wide open throttle. It does not always detonate in second but when the truck shifts into third it detonates badly. The detonation is very noticable and like I said maily happens in higher gears. (I dont notice any detonation in 1st gear) It actually damaged one of theplugs so we swappedout the Denso IT 22's for NGK BR7's but it made no difference. Also the timing was originaly 14 degrees so we backed it down to 12 in hpes of curing the detonation but it is still there although it may be a bit better as a result of this.

We are running 93 octane and I just cant understand what is ggoing on. The MAF is an SCT and is not even close to pegging, the injectord are 60 pounders and the pumps are the correct 255lph pumps. The truck basically has a built motor and a KB running a 6 pound lower and a 3 inch upper and saw about 19 to 20 psi on the dyno. The boost climbed to 21 psi or so at redline just before shifting.

Any thoughts or input would be GREATLY appreciated!

,Jason

 

HEAT!

 

Maybe a bad batch of fuel. Try some 100 octane fuel and see if that stops it. I know it isn't realistic to run 100 octane fuel daily, at least in my part of the country but if it stops, it may be a fuel quality problem.

Maybe double check the gap on your spark plugs and like l-menace stated heat.

Don't know if this will help but you can check out the info in this thread. Maybe it will shed some light on your issue.

https://www.f150online.com/forums/sh...ght=detonation

 

The first thing I am going to do is richen up the A/F a bit and see if that helps. If not then I will put it back the way it was and run some 104 octane and see if that helps. If so then I may just be running too much boost for 94 octane gas and will run a Alcohol Injection system.

The weather was very cool at between 50 and 60 degrees. The plugs are gapped at .032 and new.

 

Jason -

Something is not right...I have no audible detonation and my plugs look great, we have similar setups but I am on the stock longblock.

My basic setup is as follows:

93 octane
20-21psi of boost
15deg timing
60lb inj
SCT maf
A/F in the 11.0 range
TR6's @ .035
255LPH walbros
EGR delete

Maybe you have bad tank of gas? Try another station? There are some other things that could be causing it but lets hope it none of those (damaged heads / pistons). Is the truck running HOT also?

Bob

 

Bob there have been 3 tanks of 93 octane in it since the tune. (9 hour drive to the tuner). I have not yet put in any 94 since that is what I use around here. I will try that.

The truck runs great and does not run hot at all.

I am going to run some race gas when I get a chance and see if the detonation goes away and work from there. I cant think of anything else.

 

Send me an email :

bob-tompkins@***.net

I have some possible advice for you with regards to your setup.

Bob

 

Y not share?

 

Bob what data logger do you have is it the FJO?

 

I "may" have found the cause of the detonation. I got a SES light and checked it and it was P0171 (Lean bank one) I did a search on here and found that most times this code is related to loose vaccum line somewhere in the EGR system. I did a once over and found nothing. So I decided to look again. Well I found that one of the hoses on the DPFE was not on all the way. I dont know if it was enough to cause a leak or not. It was barley on though. I cleared the code and will drive the truck tomorrow if weather permits and see if the SES light stays away. I will also see if it cured the detonation (Fingures crossed).

I did a lot of reading about the DPFE and read in several places that a bad DPFE can cause detonation so I am hoping the SES light and the detonation where cause by this vaccum line that was only barely connected.

I will keep you guys posted.

,Jason

 

I am sad to say that I took it for a spin just now and the detonation is still there when it shifts into 3rd at wide open throttle. So the DPFE was not the problem.

 

I figured it was not Jason, Im lost at this point.

Keep looking you will figure it out!!!

Bob

 

Thanks Bob. Its hard not to get frustrated but I am trying to keep my cool and figure out what’s going on. Thanks for the encouragement.

 

http://www.factorypipe.com/Technical...Deto/deto.html more fuel less boost, is your exaust stock? less back presure=less heat. is the maf clean dosent take much. i had a bug leg mess one up. cold air is more dence,can cause deto. check
the fuel presure at the rails, fuel filter? good luck!

 

Maybe the cats are plugged.

Do you use leaded fuel?