I'm posting this question for a friend of mine. He has a 69 camaro that we put an LT1 in. The motor has afr heads along with completely forged bottom end. It has a hot cam and a ati procharger making 5#. Here is the problem. The motor is 10.8-1 compression. I know this is too high for a blown motor. He has water injection on the car which is actually lowering his intake temp about 40 degrees from the outside air when under full boost. If he runs the car without the msd ignition hooked up, the cars pulls and then misses at the high rpm. Feels like its blowing the spark out. We have a scanner hooked up and its showing no detonation. If he hooks up the ignition, the car pulls all the way to redline, but starts to ping. On the scanner it is showing knock and is pulling out 8-10 degrees of timing. Any thoughts on why the ignition is causing detonation? The plugs are autolite 104. Any help would be gratly appreciated.

 

Try Autolite 103's and gap them to 0.035 (what gap are you running now?)

What kind of fuel are you running? Hopefully at least 93, get some 100 or 104 unleaded from a race track (or www.racegas.com also VP fuels sells a 97 or 99 octane unleaded) and see how it responds.

I take it you wired in a stock PCM from either an F-body or Vette? What kind of timing are you running? Does the MSD ignition you are talking about have boost retard **** to pull timing or is it just a MSD 6AL?

Marc

 

last night he stuck in some plugs that are colder than the 104's. He said it pulled hard and he didnt here any detonation. The scanner is still retarding the timing. He is running 94 octane. The computer is a 93 camaro speed density. The computer is programmed by pcmforless. He has 42lb injectors. The msd does not have a boost retard, but its something I told him he should do. The crazy thing is how the water injection is taking all the heat out of the air and it was still pinging. Hopefully the plugs will take care of this.

 

Have you guys verified that the water injection is actually spraying (working correctly). If it is, sounds like the timing is to high. If switching to a 1 step colder plug solves the problem, then I imagine you're running to close to the edge. I'd call Alvin and see what he thinks about the timing.

 

Maybe the timing is too high on the pcm and without the msd, you don't have enough spark to fully ignite the mix(lower pressure). Hook up the box and you've got plenty of spark which apparently is enough for detonation.

Pull some timing. Or at least verify what you have.

 

I told scott that if he heard it pinging let me know asap. That motor was built for NA but was supercharged instead and I didn't have a file for boost and that type of compression.

Hopefully he can make it to the dyno with us next month.

Pass on the word though that he needs to send it back for me to take timeing out asap.

 

Thanks for the help. I know scott said he was trying to get a hold of you for a little while. I'll pass on the message. If you need his number then pm me. To answer the question on the water injection, it is definetly working. The temp goes down 40 degrees below the outside temp. Plus it is using water out of the bottle. Thanks again and
i'll pass on the message.

 

first an foremost.. water injection on a high compression motor is a NO NO.. water does not burn and steams creating higher cylinder pressures as it does not react beyond that.. so yes it is cooling the charge air temps, but is likely what is causing the spark to be put out.. I would strongly suggest using a 50/50 water alcohol mix, or even better.. go to methanol. that will kill your knock issue, cool even better then water, and can be run richer for safety factor.

hell with the price of gas.. I am considering switchin to methanol completely..lol

give that a try1

Chris

 

I emailed him tonight. He said he left a message on my phone, when I got it I thought that it was left over from the previous week when I talked to him.


I really hope he makes it to the dyno day up there, Haveing a FI car on the dyno for tuning is a very good idea, especially when he is running that much compression.

 

You are using the wrong plugs for AFR heads. The Autolite 103s are a tapered seat for stock heads.

Jeff
96 SS Blown
96 TA 396 D1

 

He is not running the autolite. That was my mistake.

 

I'm using Autolite 3923's. Is this the correct cold plug for afr cylinder heads.I am the guy with the problem.