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turbo timing question


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7 replies to this topic

#1 mitch184

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Posted 19 January 2004 - 09:34 PM

I just advanced my timing to around 23 degrees BTDC and am running 9 psi boost. I get no knock whatsoever on 89 octane. I was wondering if this is normal? I have the optical style disty and was wondering if the disty automatically retards the timing if it knocks. If is does this, would i even feel the knock?

#2 GLCraig

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Posted 19 January 2004 - 09:42 PM

The EA82T dose have a knock sensor that would tell the ECU to retard the timing if it begins to knock.

#3 mitch184

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Posted 19 January 2004 - 09:45 PM

what i'm asking i guess is if i were to crank the boost up to say 13 psi and advance the timing all the way. would the car run, but just retard the hell out of the timing automatically? Would i hear the pinging?

#4 josh long

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Posted 19 January 2004 - 10:07 PM

We were just talking about this here>

http://www.ultimates...25&pagenumber=1

Excerpt from above thread.......


"from what I know of our systems, it does the same thing...but there is a limit on how much the ECU can retard the disty. If its already retarded all the way, and its still detonating, there is nothing it can do about it. Down low, i think the engine can do 30 deg, and put out a ton of power, but up high, its gets tricky and wants 25...then 20. Then its not putting any power due to the speed of things, and the lack of an IC, lots of compression, and crappy crossover pipe....that and cams and other things that need sorting before we can make power up high like the EJs can.
Oh, the knock sensor puts out AC voltage according to knock. more AC, more knock, and vice versa."

Josh

I can testify if you run too much boost and you get "BAD" knock like say running up a long hill with 10 psi........... The knock sensor can't hang.

#5 Nug

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Posted 19 January 2004 - 10:20 PM

You'll blow it up. Turbo and too much timing = ventilated pistons.
Cranking the timing way up is, in my book, on the same level as those electric turbochargers.

If I was playing around with boost, i would follow this rule of thumb: for every psi you go up, back the timing off 2 degrees TOTAL timing. It helps to have a timing light that has a timing scale on it. Armed with this knowledge, you could theoretically mess with the timing advance in your distributor, Limiting the total timing so you could set it normal-like at idle, but cut out the total timing on top, so when you go to full advance, it isn't too much and the added boost doesn't scatter parts.
Sorry for the rant.

Is there a centrifugal advance in subie disty's? Or vacuum advance (at least on the car we're talking about)? If there is, then these mods are possible. If not, then I guess it's all in the computer, unless you want to go to something like a MSD timing controller, which on some models will lower total timing as boost goes up. This would help a high boost engine last a LONG time, as detonation in ANY turbo engine is very, very bad.

#6 mitch184

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Posted 20 January 2004 - 01:20 AM

I guess i was just wondering how i figure out if the disty is retarding to compensake for knock if is does it so quick that i cant hear the knock? Trial and error with seat of the pants or what?

#7 Nug

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Posted 20 January 2004 - 07:52 AM

The easiest way to do it wold have the Select Monitor (or whatever hooks up to older soobs) connected, you could see it happening. No one has a select monitor, so that makes it tougher. I don't know how much voltage the knock sensor makes (it's a piezoelectric cystal deal, right?) but maybe you could plumb a voltmeter in there and monitor what comes out.

I'm sure this helped immensly.

#8 MilesFox

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Posted 20 January 2004 - 12:14 PM

so far the rx with ported heads and carbbed short block does not ping, with the timing set at a hair above 25deg, and using 87 pump gas




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