DETONATION ?
- Thread starter J DAWG
- Start date
HP
Enthusiast
It is a factor of a one or a combination of things,
1. timing too advanced
2. A/F mixture too lean
3. too high compression
4. hot spots on the head chamber or pistons - like carbon or metal peaks(including plugs) that
glow.
5. cylinder pressure
6. heat
7. low octane gas or contaminants like oil lowering the octane
1. timing too advanced
2. A/F mixture too lean
3. too high compression
4. hot spots on the head chamber or pistons - like carbon or metal peaks(including plugs) that
glow.
5. cylinder pressure
6. heat
7. low octane gas or contaminants like oil lowering the octane
I have the problem with my '94 RT/10. Not real severe, but noticeable on hard acceleration, especially when it's warm. The 'Wizard' said to try disconnecting the computer for a few minutes and let it re-learn. No help. I blame it on 91 octane gas here in So. Calif. I torqued down the intake manifold, hearing that a leaking gasket could cause denotation. Maybe it helped? Racing gas/mixture definitely helps, but it's a pain and not a cure.
Larry Macedo
Enthusiast
With the aid of the DRBII and III, the dealer can go into your computer and pull a few degrees of timing out. I believe up to 6 degrees of retard if memory serves me correctly on the Gen 1. What is the mileage on your Viper, Greg, and was it purchased new or used?
Viper Wizard
Enthusiast
ceieio
Enthusiast
My GTS will rattle occasionally on hot days with the A/C on if I punch it low in the RPM band. I run Chevron Supreme. Seems like it happens more when I am being lazy by not downshifting while coming up to a light that has just changed and the cars are staring to roll as I arrive.
In answer to Larry's question about my '94 RT/10. Bought 21/2 years ago as the 2nd owner. 17K miles. No denotation the first year. Can the timing be tweaked/******** alittle to help with the denotation problem? I've gotten some mixed answers. The Wizard's idea of octane booster is probably the simplest short term answer.
HP
Enthusiast
Greg, if your car ran ok last year, but this year you have pinging -
maybe slightly colder plugs would help, along with the octane improvers mentioned. Because you have a GEN-I and there is the looming head gasket issues, inspect your plugs closely - also check for signs of head gasket leakage. Make sure your coolant system has not degraded, or you might even
consider the 99 fan upgrade. Beyond that, if all else fails, do what Larry
suggests about pulling some of the ignition advance. Pinging can be a symptom
of other motor problems, and if left untreated, can destroy your motor.
maybe slightly colder plugs would help, along with the octane improvers mentioned. Because you have a GEN-I and there is the looming head gasket issues, inspect your plugs closely - also check for signs of head gasket leakage. Make sure your coolant system has not degraded, or you might even
consider the 99 fan upgrade. Beyond that, if all else fails, do what Larry
suggests about pulling some of the ignition advance. Pinging can be a symptom
of other motor problems, and if left untreated, can destroy your motor.
Marc wrote me this response, which is probably very good info. I should try the colder plugs also, especially if the below fix is inadequate:
"Greg,
I would bet anything that your detonation is caused by carbon buildup on your pistons. This carbon buildup causes hot spots that glow red and ignite fuel at the wrong time. I have a 94 and a 2000 that had the exact same problem. The car would detonate (sometimes pretty loud) under heavy load and at higher rpm's. GM makes something called top engine cleaner. You just spray a bunch of it in your throttle bodies. They say to do it until your car dies, but I could never get enough in at one time to stall it out. So do it in the garage, spray both sides at the same time (2 cans of spray) and immediately shut it down. Leave it in there to work overnight. The next day start it up and let it idle until it's hot. Do this outside the garage, because it will smoke like crazy. You are basically burning up the carbon after the spray has had a chance to break it down. I can almost guarantee that is your problem. Please try this first! You don't want to take timing out because there is no reason why you should have to. In 17k miles, you wouldn't have stretch the timing chain. Also, I found that the octane boost didn't even help the detonation out.
Marc
Ps don't drive the car hard before you get the detonation issue straightened out. It is extremely ******* you motor. I had rebuilt the motor on my 94 and the rod bearings were all hammered out from the detonation"
"Greg,
I would bet anything that your detonation is caused by carbon buildup on your pistons. This carbon buildup causes hot spots that glow red and ignite fuel at the wrong time. I have a 94 and a 2000 that had the exact same problem. The car would detonate (sometimes pretty loud) under heavy load and at higher rpm's. GM makes something called top engine cleaner. You just spray a bunch of it in your throttle bodies. They say to do it until your car dies, but I could never get enough in at one time to stall it out. So do it in the garage, spray both sides at the same time (2 cans of spray) and immediately shut it down. Leave it in there to work overnight. The next day start it up and let it idle until it's hot. Do this outside the garage, because it will smoke like crazy. You are basically burning up the carbon after the spray has had a chance to break it down. I can almost guarantee that is your problem. Please try this first! You don't want to take timing out because there is no reason why you should have to. In 17k miles, you wouldn't have stretch the timing chain. Also, I found that the octane boost didn't even help the detonation out.
Marc
Ps don't drive the car hard before you get the detonation issue straightened out. It is extremely ******* you motor. I had rebuilt the motor on my 94 and the rod bearings were all hammered out from the detonation"
grayman
Enthusiast
Im not sure what detonation even sounds like? Only under hard load? My GTS had check engine light on for a while and I think computer reverted to safe mode. This is a rich condition, correct? I have no cats so dont think there would be any harm in it.
Both Stacks Blowin'
Viper Owner
Hi Grayman, detonation sounds like dry peas being dropped onto a drum.
I have a 97 GTS that I imported into the UK from California ( 14,000 miles in a year, mostly high speed in Europe) and up to recently had the same problems, until I discovered Shell Optimax petrol. This is a new product in the Uk and for once the advertising blurb is right, the stuff really works. Our car now ticks along at 40 mph in 6th and then pulls cleanly up to a good speed. When one slips to 5th and floors the throttle, it goes, I mean goes!!!
My suggestion to J. Smith is to go for the cleaner (we call it RedX in the UK) and then use the best quality petrol (gas to you) that is available in his area. Then, try and give the car a good long run (at least 100 miles every other week) to get everything nice and hot.
Hope this helps, Pete.
I have a 97 GTS that I imported into the UK from California ( 14,000 miles in a year, mostly high speed in Europe) and up to recently had the same problems, until I discovered Shell Optimax petrol. This is a new product in the Uk and for once the advertising blurb is right, the stuff really works. Our car now ticks along at 40 mph in 6th and then pulls cleanly up to a good speed. When one slips to 5th and floors the throttle, it goes, I mean goes!!!
My suggestion to J. Smith is to go for the cleaner (we call it RedX in the UK) and then use the best quality petrol (gas to you) that is available in his area. Then, try and give the car a good long run (at least 100 miles every other week) to get everything nice and hot.
Hope this helps, Pete.
As far as detonation with s/c's is concerned. Is the "main" way to combat this done by adding extra fuel?
I know intercooling and timing play a role, but am wondering if fuel is primary in resolving this or are they all equal in importance.
I know intercooling and timing play a role, but am wondering if fuel is primary in resolving this or are they all equal in importance.
Paolo Castellano
Enthusiast
John, detonation happens when the air and fuel mixture explodes before it is supposed to.
1. It can happen from a combination of hot spots in the combustion chambers and/or piston tops.
2. It can happen from too much cylinder pressure.
3. It can happen from the incorrect timing as well and fuel management in relation to the timing.
I would say these things are the biggest factors in tuning the fuel management to a tee. ==> If you just add fuel, you can cool down the temperature in the cylinder which will cool the hot spots but fuel only is not the complete solution. It takes a skilled tuner to monitor this whole equation properly. I believe the V-10 fires in an odd 90 and 54 degree wasted spark(two at a time{one intake/one on exhaust stroke} manner with cylinders 1 and 2 firing individually. Nothing else fires like this and therefore there is very little electronic CPU software to manage the fuel like you can go out and buy like for a V-8 or like my friend's Miata. We just drive along and tune his car on the fly. Nothing like that for the Viper.
