It only happens when I get on it at 1500-2000 rpm, or if I rev the motor with no load on it. My timing is actually retarded at the moment. It just started to do this about a week ago! I'm using 94 octane fuel. And its not a bad tank of gas cuz I have filled up since! Any ideas?

 

change your plugs, check your wires. Run octane booster to get rid of it for now. Detonation, I'm sure I don't have to tell you, is some nasty ****.... I had nightmares about it. And I'm not kidding.

 

I havent changed my plugs yet!! Thanks for the reply, JG. Any ideas why the car is doing this if it is not the plugs and wires?!?!

 

Distributor might be slipping, or a fuel injector might be sticking closed and/or injecting fuel in a less-than-optimal fashion (ie., not spraying but squirting or dribbling)... less likely, I know, but worth a shot...

 

This might be a very very stupid question , but i am new to the FI thing kinda,.. How do you know when your motor has a Detonation prob?

 

is your egr system hooked up? what ecu are you using?

 

Detonation problems can be found in a lot of ways. The best way to tell is to pull your sparkplugs and look for the signs (melted bits and/or spotting on the plugs, mainly; I'm sure there's other signs but I'm no expert so I wouldn't know ). Without pulling your plugs or checking anything you can usually feel detonation as a pinging or rattling in your engine when it's under load. However, this isn't always the case... in my case detonation felt like a surging, then a loss of lots of HP, then a surging... VERY annoying.

P.S. Retarding your timing too much can also cause detonation. Please check that you're running factory specs on your ignition timing... 15 +/- 2 degrees BTDC...


[Modified by raeneshadow, 5:59 PM 7/18/2001]

 

note: advancing ignition timing increases the chance of detonation.

 

I was wondering.....
Is there anyway to monitor how close your are to detonation? perhasp a combination of watching the a/f,egt,timing,octane,intake temp,octane, CR? Since detonation is bad, how would one tune his car to the pt where hes getting it as far as possible witout detonating, is it by trial and error? Like do somthing and go for it and see if it pings? if it does, check stuff and fix it? Or can you look at the gauges and systems i mentioned above and tell from those numbers how close you are to detonation?

Hypothetically lets say one was a turboed integra, and he tuned his car to run 9psi at 93octane, when he goes to the track and uses racegas, how does he know how much boost he can run? is it just a guess? or is there some calculation he can make to home in on the appropriate number.

Intake charge temp too high can cause det. so an intercooler is useful, lowering the temp. lowering it enough to allow increase in boost pressure for more power gain, but only increasing it to the pt where detonation is not present.....

does this question even make sense? ....how can one know what his set up's threshold for detonation is, or is the only way to find the limit is to go past it?

 

The easiest way to tell if you're detonating is to have a knock sensor, like the J&S Safeguard system. Another good way is to use the combination of an air/fuel gauge and an exhaust gas temperature gauge. Detonation severely raises exhaust gas temperature, hence the gauge, and your air/fuel will be showing lean (even on a narrowband stock O2 sensor) so it should be easy to detect in those circumstances. But the best way is still to use a knock sensor, since the results take time to show up on the EGT and A/F, and that's time you don't want to spend detonating.

 

if your always running rich, does this mean your not detonating? like after a set up....and your af always shows stoichiometric/rich, so it's safe? Basically what im asking is.... detonation will always occur when your lean, but does that mean detonation wont occur when your rich? .......

 

No, you can detonate if you're running rich - like if you're running too much boost, or if your timing's retarded waaay too much. Or having too high of a compression ratio will cause detonation also.

 

thats what i thought just making sure.

 

well? any other insight, like octane boosters, higher ocatne gas, gauges, how would one know the threshold for detonation , or does one have to pass the limit inorder to know what he or she can get away with?

Kinda like falling off a roof, how high can the roof be before you die.....is there a way to calculate this or is it trial and error?


[Modified by Ricehornet, 5:07 PM 7/22/2001]

 

Detonation won't immediately kill your motor, so it's more like 'how high of a roof can I fall off before it starts to hurt more than I think I can stand'. And yeah, it's pretty much trial and error, but if you're that close to the limits on detonation I would imagine power would begin to fall off. Obviously you don't try running 13:1 street compression, don't go crazy advancing your timing, etc... just common-sense stuff. It's also good to prevent detonation by polishing sharp edges and burrs on your pistons and cylinder walls.

Detonation isn't also an on/off thing. You can have varying degrees of detonation, from a small rattle to a big-*** explosion. That's why the J&S Safeguard is so good; it listens for detonation in varying degrees.