detonation hell

[boostin'03]

Well i ran my car at the track last friday and on the right side of the motor the last 2 cylinder spark plug insulators where chipped off and broke and the little prong was melted off, same thing for the left side rear. Anyways hope i didnt mess it up to much. What heat range do you guys recommend for my car i am making 586rwhp thanks

btw it was a cold day and my tune in the upper rpms was 10.6 so I am still confused on how it detonated so damn bad

My old plugs were denso it22s

 

[hj16]

Originally posted by boostin'03
btw it was a cold day and my tune in the upper rpms was 10.6 so I am still confused on how it detonated so damn bad

Bad gas???

 

[Twinturbo Ranger]

timing??

 

[boostin'03]

could be, you guys think i should stick with the same plugs is the heat range good or should i go with something else, ill be going to stricktly pro to check out the tune.

 

[NightEnforcer]

I f you can get you hands on a bore scope, use it to check out the cylinder walls and the top of the piston. Most high end shops have such a tool. I use one that actually bends back so that I can see the valves too. You may have damaged either the piston or scarred the cylinder walls. The valves could also be damaged. Keep your fingers crossed. Some guys have had detonation and have lucked out, others have had serious damage. I would also recommend you have a mechanic do a leak down test.

Are you running a racing fuel mix? If not you ought to be. The pump gas could have been bad, had H2O in it or was a poor blend of oxygenated fuel. What was your fuel pressure? What is the timing curve dialed into your chip? All of these items impact what happened.

Denso's are a good but fragile plug. They do not tolerate detonation anywhere as well as NGK copper core plugs or Autolite copper cores. That is why most big time racers pushing the limit of their cars use copper core plugs. Even the new NGK Iridiums run a larger diameter core than the Denso's. You may have to change a copper core plug more often, but they tolerate adverse conditions a lot better. I would suggest you go with the NGK racing plug one to two heat ranges colder than the 22,s. For example NGK Racing V groove plug R-5724-9. I run those in mine with the KB, 55lb injectors and 573 RWHP. The only real issue with a colder plug is that it might carbon up in high traffic stop and go driving. Check them after a week. If it does, go one step hotter and try that.

Good luck

 

[boostin'03]

thanks alot nightenforcer I will check with them and ask them to do what you listed, I had no idea there even was such a tool where you could check out the piston and stuff without actually taking off the head. Thanks

 

[boostin'03]

BTW is a leak down test the same as like a pressure test? I have a pressure tester where I screw the thing in the spark plug hole and crank over the engine to see the PSI.

 

[racerat]

Originally posted by boostin'03
BTW is a leak down test the same as like a pressure test? I have a pressure tester where I screw the thing in the spark plug hole and crank over the engine to see the PSI.

They aren't the same, but a compression test is a good place to start.
Hope everything is ok.

 

[PhillyCobra]

boostin'

That's a real drag. Sorry to hear.

Did you look at your other plugs? If they don't have evidence of detonation or leaness, it makes me wonder if you might have an isolated problem, such as poor flowing injectors, in the specific cylinders that went down.


We always hear about detonation occuring on the back cylinders, particularly on the driver's side, on high pressure engines. This has been attributed to less coolant flow in the back of the head, particularly on the driver's side where there's no coolant outlet to the heater core. Your main problem is on the other side, which seems unusual.

This makes me wonder if high boost engines might pump more air into the rear cylinders than the front because of supercharger flow dynamics. This would result in leaner A/F in the rear. Certainly we know that old carburetor manifolds often didn't provide equal flow to all cylinders. I don't know if anyone has ever looked at this. Might be easiest to tell indirectly with exhaust pyrometer on each cylinder, like some racers are doing.

Anyone have any ideas here?

 

[cobrapete03']

Well you said it was cold, so denser air can do that (lean the mixture)...Plus if the gas was oxygenated then that doesnt help too...I've been running a mix of Cool Blue 76 100 Octane in mine right now to help with this shitty oxygenated Cali. gas and these 30 degree nights...I hope everything turns out Ok. Good luck man.


-pete :coolman:

 

[trey193]

I run a mix of 93 and 100 with my tune and I make about 100less HP than you, with the power you are making I would always mix in good gas with your supposed safe A/F I am thinking you got ahold of bad gas or your tuner has to much timing in the car up top. I run the mix of race gas because my tune has a little more timing than others! hopefully you didnt tear up anything!