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rattle of doom detnotation
#1

OK maby I can't spell it but I may have it.
85 svo stock block and head,T3O4 turbo,ported upper and lower,35# injectors,gillis valve,afpr,ported E6,2/5 exhaust with hiflo cat only,LA3 and stock TB.
Fuel pressure is at 40 without vaccum,about 32 with.Boost is at 20 psi.
Now understand I have a hearing loss and cannot hear the noise described to me by my son as sounding like a baby rattle when under full boost.(Knosk sensor is unpluged)
If indeed I am detonating,how could I be shure without hearing it myself?
How can I stop it without turning down the boost?
Maby more fuel pressure?
THanks,
Don
One other concern I forgot to mention is this.
The computer is still laying in the floor of the car.After the test drive it felt warm to the touch,more so than usual.
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#2

back your base timing back to about 10-12 deg
"there is no such thing as a stupid question, just stupid people"
PICS OF MY XR, FOLVO STUFF, AND...
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#3

Things that will help stop detonation.
Retard timing, reduce boost, bigger/better intercooler, more fuel, higher octane fuel, water injection.

Retarding timing and reducing boost will likly reduce performance, but could save your engine.

Another thing to consider is having your injectors cleaned, and flow balanced. If one of them gets dirty and flows less fuel than the others, the cylinder it is in will likly detonate.

I don't know how to tell if you have detonation if you can't hear it. But your sons discription seems pretty accurate. It's like a metalic baby rattle with a couple of ball bearings in it, that some adult has gotten a hold of and is shaking really hard under your hood.

my $.02

Dan
86 SVO
Sand Rail w/79 long block, 85 T/C injecton and EEC-IV, IHI turbo
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#4

I am running 12* before tdc now and running premium fuel which I believe to be 92%octain rating.
I have but have not installed the volvo IC,maby next weekend.
I guess For now I will replug the knock sensor to be safe.I shure like the way it runs as is.
I wonder if a can of octain booster would help?
Does anyone have any thoughts on the computer gettin warm?
Don
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#5

I've had the computer on my sandrail out in the open when i've been test driving it, and after driving it for a while it gets warmer than I expected. Never so hot that it is uncomfortable to keep my hand on it, but pretty warm.

I'd bet that the computer is no warmer than usual, but that you've just never noticed it before. Smile
86 SVO
Sand Rail w/79 long block, 85 T/C injecton and EEC-IV, IHI turbo
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#6

Probably right on with the computer answer Dan.
I have never touched it before after driving the car untill today.
I think I will back the timing down to 10*,add a can of octain booster to it and drive it again to see what will hapens.
Don
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#7

OK went back a rechecked timing it is at 12*
boost was above 22 hard to get good reading and watch traffic,it is now at 20 added octain booster no more detonation.I believe turning down the boost solved the problem,the octain boost will be a plus.
Thanks for the help.
Don
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#8

Well now that you got it running, you'll have tige me a ride in it this weekend
Lon
1985.5 SVO
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