Detonation
Thread Starter
Instructor
Joined: Jul 2005
Posts: 124
Likes: 0
Detonation
My car is detonating under certain conditions, and I'm trying to figure out the reason.
I have it set up for 36 degrees total advance, all in by 3000 rpm. Vacuum canister adds 16 degrees, for 52 total. I only have access to 91 octane fuel here, so that does not help.
So, the car has a 2004R transmission. It will detonate sometimes when in overdrive. Like the other day I was going up an on-ramp, and it shifted into overdrive, and started detonating.
I read the sticky on timing. It says to check for detonation by putting the transmission in high gear and then accelerating from low rpm. But I have an auto tranny, and this the transmission would just simply downshift.
So, how can I tell if I have too much timing from the vacuum can or just too much timing from the mechanical advance?
I have it set up for 36 degrees total advance, all in by 3000 rpm. Vacuum canister adds 16 degrees, for 52 total. I only have access to 91 octane fuel here, so that does not help.
So, the car has a 2004R transmission. It will detonate sometimes when in overdrive. Like the other day I was going up an on-ramp, and it shifted into overdrive, and started detonating.
I read the sticky on timing. It says to check for detonation by putting the transmission in high gear and then accelerating from low rpm. But I have an auto tranny, and this the transmission would just simply downshift.
So, how can I tell if I have too much timing from the vacuum can or just too much timing from the mechanical advance?
Cruising
Joined: Oct 2010
Posts: 14
Likes: 0
My car is detonating under certain conditions, and I'm trying to figure out the reason.
I have it set up for 36 degrees total advance, all in by 3000 rpm. Vacuum canister adds 16 degrees, for 52 total. I only have access to 91 octane fuel here, so that does not help.
So, the car has a 2004R transmission. It will detonate sometimes when in overdrive. Like the other day I was going up an on-ramp, and it shifted into overdrive, and started detonating.
I read the sticky on timing. It says to check for detonation by putting the transmission in high gear and then accelerating from low rpm. But I have an auto tranny, and this the transmission would just simply downshift.
So, how can I tell if I have too much timing from the vacuum can or just too much timing from the mechanical advance?
I have it set up for 36 degrees total advance, all in by 3000 rpm. Vacuum canister adds 16 degrees, for 52 total. I only have access to 91 octane fuel here, so that does not help.
So, the car has a 2004R transmission. It will detonate sometimes when in overdrive. Like the other day I was going up an on-ramp, and it shifted into overdrive, and started detonating.
I read the sticky on timing. It says to check for detonation by putting the transmission in high gear and then accelerating from low rpm. But I have an auto tranny, and this the transmission would just simply downshift.
So, how can I tell if I have too much timing from the vacuum can or just too much timing from the mechanical advance?
Cruising
Joined: Oct 2010
Posts: 14
Likes: 0
My car is detonating under certain conditions, and I'm trying to figure out the reason.
I have it set up for 36 degrees total advance, all in by 3000 rpm. Vacuum canister adds 16 degrees, for 52 total. I only have access to 91 octane fuel here, so that does not help.
So, the car has a 2004R transmission. It will detonate sometimes when in overdrive. Like the other day I was going up an on-ramp, and it shifted into overdrive, and started detonating.
I read the sticky on timing. It says to check for detonation by putting the transmission in high gear and then accelerating from low rpm. But I have an auto tranny, and this the transmission would just simply downshift.
So, how can I tell if I have too much timing from the vacuum can or just too much timing from the mechanical advance?
I have it set up for 36 degrees total advance, all in by 3000 rpm. Vacuum canister adds 16 degrees, for 52 total. I only have access to 91 octane fuel here, so that does not help.
So, the car has a 2004R transmission. It will detonate sometimes when in overdrive. Like the other day I was going up an on-ramp, and it shifted into overdrive, and started detonating.
I read the sticky on timing. It says to check for detonation by putting the transmission in high gear and then accelerating from low rpm. But I have an auto tranny, and this the transmission would just simply downshift.
So, how can I tell if I have too much timing from the vacuum can or just too much timing from the mechanical advance?
Race Director
Joined: Dec 2005
Posts: 13,515
Likes: 12
From: Fisher, IL
Sorry to bust in here but I also set my timing to 36 and the car hesitates every once in a while. Usually when just cruising not under WOT.
Is it easy to tell if it's detonation or could it also be a carb issue?
I guess I could retard mine as well and see if it gets better?
Is it easy to tell if it's detonation or could it also be a carb issue?
I guess I could retard mine as well and see if it gets better?
Last edited by PUNISHER VETTE; Oct 20, 2010 at 06:51 AM.
Drifting
Joined: Apr 2006
Posts: 1,911
Likes: 2
From: gold coast queensland
almost any performance orientated engine if lagging in overdrive and floored will detonate....you might not hear it but doesnt mean its not happening.
Its a little unclear if you said you were in a healthy part of the powerband or if you were just cruising. if you combine a on-ramp (especially up-ramp) with overdrive and you dont drop a gear to something suitable then its going to get angry with you.
so i might be jumping to conclusions but is your trans shifting down as it should?
Its a little unclear if you said you were in a healthy part of the powerband or if you were just cruising. if you combine a on-ramp (especially up-ramp) with overdrive and you dont drop a gear to something suitable then its going to get angry with you.
so i might be jumping to conclusions but is your trans shifting down as it should?
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
almost any performance orientated engine if lagging in overdrive and floored will detonate....you might not hear it but doesnt mean its not happening.
Its a little unclear if you said you were in a healthy part of the powerband or if you were just cruising. if you combine a on-ramp (especially up-ramp) with overdrive and you dont drop a gear to something suitable then its going to get angry with you.
so i might be jumping to conclusions but is your trans shifting down as it should?
Its a little unclear if you said you were in a healthy part of the powerband or if you were just cruising. if you combine a on-ramp (especially up-ramp) with overdrive and you dont drop a gear to something suitable then its going to get angry with you.
so i might be jumping to conclusions but is your trans shifting down as it should?
If it only happens in situations like you described, just adjust your kick down so it down shifts sooner.
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Burning Brakes
Joined: Feb 2009
Posts: 780
Likes: 1
From: Shelby NC
almost any performance orientated engine if lagging in overdrive and floored will detonate....you might not hear it but doesnt mean its not happening.
Its a little unclear if you said you were in a healthy part of the powerband or if you were just cruising. if you combine a on-ramp (especially up-ramp) with overdrive and you dont drop a gear to something suitable then its going to get angry with you.
so i might be jumping to conclusions but is your trans shifting down as it should?
Its a little unclear if you said you were in a healthy part of the powerband or if you were just cruising. if you combine a on-ramp (especially up-ramp) with overdrive and you dont drop a gear to something suitable then its going to get angry with you.
so i might be jumping to conclusions but is your trans shifting down as it should?
If you hear it best fix it!
