Detonation

OK, here is my problem. After talking with a mechanic I found out that the noise I was hearing at WOT is detonation, not good. I pull anywhere from 10-15 psi of boost and have seen 17 (aftermarket boost gauge installed). The mech. I talked to said that is way to much boost for the type of supercharger I have and only running 91 octane fuel. I do have a od pulley on the sc, I was told by the guy I bought the car from that it was 10%, but it looks identical to the 89-93 style pulley. Anyway, the mech. said to get the boost back down to 8-10 at WOT and that should solve the problem. Also, at 4k-5k rpm I feel the car start to hesitate, like it loses power.
Has anyone had to deal with detonation, and if so, what advice do you have. My list of mods is as follows
85mm TB, 76mm MAFS, SCP 3.5" induction, MP inlet plenum, 3/4 raised top, kooks headers and big dog exhaust, cam regrind, ported and polished heads, OD pulley(now I am unsure of what size)
The car pulled 256 RWHP and 360 lb/ft torque SAE corrected. This seams low to me.
Please help me with this problem.

that RWHP is pretty good considering frictional losses and whatnot in the drivetrain. Most camaros dont make more than 275 at the rear D: Anyway, if its really bad dont drive it you can ruin your engine completely. Detonation is pre-ignition, your engine is trying to run backwards. You can imagine what this is like at 4 grand and the piston is being shoved reverse of the direction its rotating. Even if you cant hear it doesnt mean its not happening. Id underdrive the supercharger OR add some octane boost, 110+.

injectors

It may be time for larger injectors,something to think about.

The loss of power could also be bad plugs and wires , make sure you use Motercraft double platinums and some bosch junk. and find a sunoco and fill up with some 93, only costs a couple bucks more. try it and see what happens then. For that Charger to pull that much boost (ie. back pressure) with that big of an exhaust is pretty wild. You might want to see if the cats are clogged or something, it just seems high to me.

I have the exact same problem as you, and mine's a '94 also. I can peg my boost gauge and at about 14-15 PSI, it starts to detonate.

Have you upgraded your fuel pump or are you still stock? I've tried ALL KINDS of stuff to try to figure mine out and my next plan of attack is to replace my fuel pump.

Let us know if you ever get it figured out.

Dale

P.S. Oh, and find a new mechanic. 8-10 PSI???? He does realize that these cars run about 13 PSI or so STOCK!!!

It needs more fuel....if your not going to do it right (increase the injectors 42#, pump 255 lph FI, recalibrate MAF and dyno tune with wide band o2) you should at least put a larger fuel pump in and an adjustable fuel pressure regulator and raise the static pressure to around 45 or 50 psi.

David

You've got a lot of air coming into that engine but so far you have stock fuel pressure and injectors. Now the 36lb injectors in your 94 may be good enough still, but you will want to get a larger volume pump, and either an afpr or have it tuned and have your fuel map refigured.

To be on the safe side, 38, 42, or 50 lb/hr. injectors should be used. I haven't heard of a good AFPR yet either. The Kirban's are junk, and I have heard so/so reviews of the aeromotive ones. I think to do it right, you should tune the computer and upgrade your fuel system.

Dale, is it you that has the pics of the SC engine with the hole in the piston. Talk about detonation... If you got 'em post 'em.

The guy I bought the car from said he put in a 255 fuel pump, wether or not this was done I couldn't say. He gave me a list of things he did to the car but I can only verify what I can see.
What is a AFPR? Never heard of that. Also, what does a dyno with a wide band O2 do for me. I am new to these cars and would like to get my car running great. Any more help or any more questions please feel free to ask. Thank's for the help.

Scott, no that wasn't me.

94scnflt - An AFPR is an adjustable fuel pressure regulator. It allows you to adjust the pressure levels.

A wideband O2 allows you to see EXACTLY what air/fuel ratio you are running all the way through your power band, to tell you if and when you are running lean, etc.

Dale

sounds like its running out of fuel.

The hesitation you feel is probably caused by the knock sensor coming on.

Try a tps sensor let me know what happens

detonation

I am having similar problems. My car is a 1990 SC and is still mostly stock. The only mods I have so far are: Trans-GO shift kit with raised shift points, B&M QuickSilver shifter, and a K&N 9" cone filter. Previously I was having to use a 5+ point octane booster with 93 or 94 octane gas to keep it from knocking. A little while later, the engine died. The crankshaft snapped at the first journal. I had a complete long block installed. The speed shop that did the work told me that it looked like the broken crank was over ground. The new engine has almost 8,000 miles on it and I'm starting to have to use an octane booster again to keep it from knocking. I would appreciate any suggestions as to what I can check.

George, what is a TPS??

I ran some octane booster last night and filled it up with 91 octane from chevron. The engine sounds better, but heard a little detonation. I am putting two and two together and this problem came up after I went from a stock MAFS to a 76mm and from a 70mm TB to a 85MM TB. I am going to drop back down and see what that does.

Also, I was reading the post on cam regrind and I think that might be another problem I am having. See the guy I bought the car from said he had a cam regrind done, but he didn't know the specs. He also said the heads were ported and polished with a 3 angle valve job and bigger rocker pins? And one more thing, he also said he did something with the spark plugs to have them set where they all faced the same direction, somehing with tapping the holes to make that happen.

So here is my plan, I am going to get new wires and plugs. I am going to drop down to a 70mm TB and stock MAFS. Then I am going to find some used heads, and have them built with new rockers, valves, and ported and polished. I am going to get a new cam for it, make sure there is a upgraded fuel pump and go from there. Hopefully the pistons aren't F*&*$d and the crank isn't bent.

If this helps anyone please let me know. I am to the point of finding a used engine from a junk yard and building it up from scratch.

One last thing, what is the recommended spark plug to put in the car?

I had that same problem some years ago on my 93 - 5 speed, with a 10% pulley & 190 lph pump. However, after connecting a fuel pressure gauge to the fuel rail & running an extended hose attached to the wiper arm I was able to observe the pressure at WOT. Mine would struggle & hesitate at about 52 psi (if I recall correctly). After talking with Lee Bender at C&L (I'd just installed their MAF) he recommended changing the fuel filter (and every 15,000m thereafter v. the recommended 30,000m interval). That did the trick !!! & I very occationally get some mild pinging if I don't use 93 octane. Most premiums these days are 92/93; but there are some brands still using 91 like Getty. So be observant at the pump.
Give it a try - it may be a cheap fix,
Jim.

I have and only running 91 octane fuel. I do have a od pulley on the sc, I was told by the guy I bought the car from that it was 10%, but it looks identical to the 89-93 style pulley.

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There are lots of things for you to consider:
That pulley: Just because it looks stock dosn't mean it is.
Measure it with a micrometer. ,...My CMRE will ping like crazy where others don't with 92 octane and an O/D pulley....
.... change it out '... this may be the answer!
I for one do not believe more boost is always a good thing, unless you can control heating with an effecient heat exchanger (double IC or Front mount IC)..your creating more heat for the engine to deal with.
You can always run the other pulley at the track with a few gallons of race fuel added to the tank.

FUEL: Our fuel these days sucks...specifically the winer mixes we get . the octane rating is low at best. I've seen lots of problems on stock engines with detonation....Add some octane booster, or get some high octane race fuel and keep it on hand. I get a barrel of race fuel every year and mix it with regular fuel in a separate barrel. Allitle goes along way but its a PIA mixing fuel all the time! Thers alot of racers that do this to save money and don't need 104 or 110, just something close to 95

Larger injectors may be the next thing to look at.

If the pulley is stock your answer may lie in an expensive front mount IC., or at the very least; a double IC!
A good tuning session on a dyno would be in order to check Air fuel ratios!

And your power is not too bad but there should be more if the cam is not stock and any head work has been done.
Before we put the CMRE in, we had all the bolt ons you speak of with 38lb injectors and mild head porting and and pulled 258 RWHP and 325 RWTQ ...this with bad HG and broken ring, oil being pushed up the dip stick from too much crank case pressure.

I could have smacked myself yesterday for not thinking of the fuel filter earlier, thanks Joisey Jim. I am in Cali. so the highest octane I can get is 91, but the octane booster helped. I am going to drop back down to the 70mm TB and stock MAFS until I can fix this the right way with the right parts. Besides, the 76mm MAFS and the 85mm TB gave me all about 4 RWHP and 5 lb/ft of torque and no detonation. When I get the money and the time I am getting a new cam and heads and rebuild the bottom end. Then upgrade the fuel system. Thank you all for the help.

There have been other threads talking about problems with the 10% pulley. Basically what they said is that the air gets hot enough with a stock intercooler to cause destination, which causes the knock senor to pullout timing around 3K. I think it would be a good idea to see if you have a stock pulley or not. Just my .02

It is a throttle position sensor . It werked for me just like hooked phonics let me know if it works for you.

Ok George, Just to find out, I'm gonna put my 2.95 ESM pulley on and change out the TPS, If the detonation is gone , I'm gonna bow down to ya! Just kidding...
On another note do you still have the IC reseal tape and how do I reach you? I tried your old e-mail about 2 weeks ago and it got returned.

Man I hate posting this again but before you go and start tearing your car apart change the pully to a 89-93 or the stock one.
My 94 did this untill I took off that dam pully. I put it back on and same problem. I sold it and no more problems. It just seems to be a problem with 94-95 cars. I do beleve the a larger intercooler would help but what do I know.