Ok I can take the boost up to 10 pounds at about half throttle, just kind of easing it up to 10 lbs, Then floor it and it get audible detonation even though the boost stays at a steady 10 psi. I am running plenty rich, good egt's. I know that some of you have been having problems with detonation at partial throttle, but I am having the opposite problem. I also have the timeing retarded 10 degrees starting at 4000 rpms on my dis 2. Not the programable type. I have about 77-80 psi of fuel press. at 10 psi of boost with 370 cc injectors. I dont have the colder plugs in yet Cause I had to order them but even when I did I had the same problem. I am kind of clueless. I need a datalogger. I have also recently replaced the tps, and put in a crank pos. in from another motor I had. should I replace any other sensors. Like air intake temp, cam angle. I do beleive that It may be timing related, But I just am so tired of have to turn everything off and listen for detonation everytime I get on it.

do you have a SAFC? you can also detonate by running TOO rich and taking out TOO much timing. with 370cc injectors there is noway you should be detonating at 10psi unless your plugs are a real hot range or gapped wrong.

Ya man, if you have an afc be carful...I'm blew my first engine due to mistuneing of the afc. It was the timing that got me not the boost/fuel.

taking out too much timing can also melt exhaust valves, because you're basically spitting the flame of combustion out because it is firing so late in the stroke. You need a datalogger to verify your timing advance.

Also, i for one have never heard any detonation from under my hood, ever. I do hear rattles that could be confused for detonation, but if it were, i would have ruined this bottom end a long time ago. Maybe you are not hearing what you think you ae hearing..

Star or Hahn kit?

This is slightly off topic, but I have noticed that 95's seem to have less problems with detonation than the 96+ cars. On my car, the week before my new block arrived, I turned up the boost to 12 pounds of boost and I never heard any detonation at all. It still read rich and let out black smoke. This was all on stock injectors and 115 psi of fuel pressure. On XtremeRS's car (97) he was having trouble with detonation, especially before he put in the missing link. I really wonder what the differences are between obd1 (95) and obd2 (96+) cars are as far as how the ecu/pcm controls timing/fuel delivery etc... If anyone has any insight on this, please enlighten me :)

basically, the OBD1 ECU's can recognize a problem or "difference"(like seeing boost) and throw a CEL, but it really cant do anything about it on its own. a OBD2 ECU sees the problem, and can take measures to try and "fix" it...thats where we get screwed. id like to swap in a 95 ECU,harness, and fuel system if i ever came across one in a junkyard or something, long as it wouldnt be too big of a headache to swap in.

I am very happy with the way my 95 system performs under modification. It is far and above better (IMO) than the 96+ systems. The thing i like the most is that the ECU will actually seem to "learn" when a problem happens and work around it, and will lose the CEL when it has found a stable way to do what it needs to do around what it determines is wrong. As a side note, i have no EGR system and no EGR CEL, i have no cat and no cat failure CEL. If that isn't reason enough to appreciate the 95 control system, i don't know what is :-)

I also don't get crazy timing advance due to my AFC, which is leaned out to -50% at idle and slowly works up from there. I also never need a FCD, missing link, or vc1, a return system (it's already there), or a vaccuum line to the back of my car. They seem, in my experience, much more forgiving to heavy mods than the 96+ systems are.

Thats part of the reason I am selling my car. I cant seem to run over 9 psi without detonating. If I keep the car I am getting a msd and seeing if I can raise the boost over 9 psi. I cant stand only running 9 psi. It sucks!!!

Have you tried running w/ out the AFC Dave? Maybe you should just try it and see what happens. I can run 15psi and never get over 19 degrees advance.

With 440's and the s-afc the engine should be flooded with fuel. I have no idea how your car can run with out it. I might give it a try this weekend though and see what happens.

I used to think that it couldn't run either but it actually runs good. I have my idle set to 13psi and static to 24psi. I"m using a 4.4:1 rise rate which gives me 90psi at WOT. At idle I get -25% LTFT and like -20% STFT. Partial throttle it goes between -20 and -5% and hits closer to 0% in closed loop boost. So the fuel trims aren't completely maxxed out ever.

What exactly are your egt numbers and your A/F numbers under WOT boost? You say you have enough fuel, but i will agree that the SAFC can be advancing the timing too much under WOT. At 10 psi, you should be seeing around .95-.96 o2's in 3rd or 4th gear. Once we hit 10 psi, we need lots of fuel to not detonate. The standard of .93 o2's for tuning wont be right. Try and zero out the SAFC if you have one, and try adjusting fuel pressures to help controll your fuel trims.

so... do you guys think it would be possible to swap a 95ECU and harness to a 97 car, or would it be more of a pain in the ass than it is worth? reason i ask is i have access to one from a wrecked car.

Matt. When I datalogged my car way back when I was runnign 15 psi I was getting .94-.96. It was plenty rich. My timing was actually OK in third gear. It was way high in second gear though. I am going to try the no s-afc method and seee how the car likes it. Should be interesting. I hope it likes it and runs good. I really cant take running 9 psi for much longer. If my tires dont break loose at the top of second I am not happy.

hey dave, you still got the hrc fpr right? do you have your gauge mounted outside to check up on it?. or do you got a electrical fpg?
i doubt anyone will buy a car thats mod like your, if someone does cool. but start thinking about getting a ignition to retard timing, and dang it get rid of that hrc fpr. your car will be very good, with of course tuning.


Michael 99gs
HRC Stage 2
Stage 3 process begins anyone got a 420a block thats not spun/head for sale?

http://www.dreamwater.net/purplebeast

Yeah looks like I am going to keep her after all. I went to go look at the GSX I wanted and it was auto!! So i am not buying it. I am going to get the sfmu and the ignition within a couple months and see how it goes. I am also going to do all my lines with SS braided ones. For the time being I am running 9 psi just to be safe.

yah, i would not want a gsx auto. well yah, with the s-fmu, and ignition with of course dyno/tuning you should be pretty tuned for street. you went this far, why lose all you have done.
well good luck


Michael 99gs
HRC Stage 2
Stage 3 process begins anyone got a 420a block thats not spun/head for sale?

http://www.dreamwater.net/purplebeast

Well I zero'd out the AFC and then backed off the ignition retard to 2 degrees and I am not hearing that rattling sound. So I am very convinced that the AFC is causing the problems. So I am thinking of just taking it out. I really do need a datalogger though. Some of you guys have been getting yours from pocketlogger.com right. Is there anyone else's that you guys have found to work well. Thanks for your info. By the way it is a hahn kit. Sorry it took me a while to post.

well u need to datalog it too see how much timing its advancing.. it really comes in handy really. i got a pocketlogger, and ob2 program for my labtop. both are great dude.



Michael 99gs
HRC Stage 2
Stage 3 process begins anyone got a 420a block thats not spun/head for sale?

http://www.dreamwater.net/purplebeast