I now think I am getting detonation under load in hot weather. Happend to me twice doing 80. I supsect it might be the K/N cone, as it was superheated. Under hood temps were around 160 to 180.

Will added heat through the K/N cause detionation or should I be looking at somthing else?

 

Detonation is usually caused by:
a. timing too far advanced
b. Fuel octane too low
c. Running lean

 

It could contribute to it but I would look other places. Is your timing set right? Any ignition mods? what kinda fuel are you using maybe it is bad gasoline.

 

Ouch! Get a heat shield and cold air duct in there ASAP. Hell yes!

 

d. High intake temps

 

The tank was filled with mobil 93 yesterday, I usually run 89, switched to 93 a week ago.

 

Maybe you should switch back?

e. Bad gas

 

It could be bad gas, but I’d still stick with the higher octane. Run the tank as low as possible (no full-load runs in the mean time) than refill from a different place. If the problem persists, it probably not the gas.

(And get that heat shield.)

 

US 93 octane is equivalent to 97 octane in NZ. If a stock engine is detonating on that, then there is something very wrong. I have driven stock-engine S4 TII's with underhood intakes at well over 100mph with 87 octane in ambient temperatures over 100 F, and never had any detonation problems.

 

True, I don't think it's an octane realated problem, but I think it should have been on the 93 anyway. We have 91 and 96 (plus a bit of 98), and I'd never run 91. At 100mph, you've got no chance of hearing detonation...
The fact that high intake temps increases the likelyhood of detonation is well proven. Why take the risk?

 

I disagree. I should be able to hear detonation at 100mph just as well as he could hear it at 80mph. Besides, the reduced timing from the knock sensors should cause a noticeable decrease in power.

If the engine is running well, then the 93 is a waste of money, as the S4 is rated for 87 octane (91 octane in NZ lingo). Granted, his engine may need the 93 though, LOL.

BTW, there is no way that the under hood temps were 160-180 F at 80mph unless the car was being driven over the top of an erupting volcano.

 

...were you looking at your water temp gauge when you summarized this? Or do you actually have an ambient air temp gauge underneath your hood?

 

Yeah, that does seem a bit dodgy. Maybe it was water temp like Jspec suggested! I have a digital temp display with its sensor on the nose of my pod filter. Without a heatshield, I’ve seen it get over 60ºC (140ºF), but not much more.

 

The ambient outside temps were in the 70's. The car had been run for about a good 15 minutes before entering the hwy. Mind you the detonation happend when going up an incline doing 80. And once on a level ground.

Upon getting home and popping the hood I noticed the radiator hose was shaking from boiling coolant. I also could not keep my hand on the intake, 140-160 is my best guess at how hot it was compared to the outside temps.

This car also has 160k on the clock, 30k jspec turbo. Radiator had been fixed with stop leak. Could my radiator be clogged somehow?

Thanks

 

I found that Citgo and Kwik Fill gas gave me the least detonation. I tend to stay away from Mobil (not that bad) and Sunoco (very bad) as often as possible. What kind of exhaust do you have on the car? If your exhaust has been upgraded, you should upgrade your fuel pump to compensate, and possibly add a fuel controller.