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Old 05-16-2000, 11:19 AM   #1
Tim Prudence
Scooby Specialist
 
Member#: 216
Join Date: Aug 1999
Location: san diego, ca USA
Post Help Stage I turbo folks (ie non-intercooled)

Did you guys without intercoolers have to pull back timing a lot to stop detonation from occurring? I have found that even with a good A/F ratio (o2 voltage reads consistently over .85), I still have to pull back timing 3 degrees at 2400 rpms, 9 degrees at 4000 rpms, 8 degrees at 5600 rpms, and 7 degrees at 7200 rpms. This seems like a lot of timing for only 5.5 pounds of boost. I'm running 92 octane gas with a small subaru IHI turbo. Backpressure shouldn't be too bad, I have 2.5" piping from the turbo back (with a 2.5" cat).
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Old 05-16-2000, 10:35 PM   #2
Imprezer
Dynamic Uno
 
Member#: 1
Join Date: Jun 1999
Chapter/Region: BAIC
Location: Alameda, CA
Vehicle:
2011 Impreza WRX STi
Black

Post

How do you know it's detonation? How does it sound like?
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Old 05-17-2000, 10:30 AM   #3
Tim Prudence
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Join Date: Aug 1999
Location: san diego, ca USA
Post

It's a crackling sound that sounds like it's coming from under the car. It goes away when I lift the throttle and it goes away when I turn back timing. It sounds very loud and scary.
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Old 05-17-2000, 10:38 AM   #4
Imprezer
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Join Date: Jun 1999
Chapter/Region: BAIC
Location: Alameda, CA
Vehicle:
2011 Impreza WRX STi
Black

Post

Could that be all the excess gas burning in the exhaust system? Do you see fireball coming from the exhaust pipe? With you setup and OVER tunning, you should not see any detonation, I think.
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Old 05-17-2000, 02:56 PM   #5
SKiDaZZLe
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Member#: 19
Join Date: Jun 1999
Location: Dallas, TX
Post

tim:

i will take pictures of the sway bar. i do not knwo what to say, except it fits like a charm.

it is not the radiator hose i am worrying about...

here is a pic of it (not where the arrow is pointing to, but rather the bulge on the bottom middle with the 2 bolts).



my header almost touches the lowest part of that buldge... i am not worried about the hose itself.

michael
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Old 05-18-2000, 12:06 AM   #6
SKiDaZZLe
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Member#: 19
Join Date: Jun 1999
Location: Dallas, TX
Post

tim,

i was too lazy to find the original post about the RS sway bar and turbo legacy crossmember...

BUT

The shop got mine on fine. i saw them install it. it looked like a simple bolt up like the rear. they did not have to re-shape it or anything.

i do not know why you are getting det. i have the same setup except mine is I/C'd. I run 5 and 8 lbs with no det. i will be posting pics on i-club soon...

i did have some questions on your install...
with the headers off the legacy, the distance b/w the ports (lh/rh) is almost .75" shorter than on the 2.5 engine. my shop took off the heatshield and added some pipe right next to the flex section. this fixed that. next, they needed to add a 3/8" spacer on the driver side exhaust port so the header would clear the water outlet.
the driver side header is within like .25" of that water pipe, and i am afraid it might melt it (although nothing so far after 200miles). did you rotate this around or replace it with an aluminum piece? the latter is my hope, as the piece is like ABS plastic, and would be impossible to mold. do the turbo cars have a different water outlet?

did you take any pictures yet? i would love to see the underside and the engine bay layout! mine is really nice and looks great. i should snap some quick ones tonight...

oh yeah, do you have a safegaurd? this is invaluable in tuning.

good luck,

Michael

EDIT: forgot to mention i am running 2.5 mandrel from the turbo to the mid-pipe only (dont ask... miscommunicaiton with the shop) then it is the 1.75" subaru crap to the 2.5" STi. I disconnected it at the midpipe last night for kicks... it rose boost 2lbs and added a huge amount of top end.

[This message has been edited by SKiDaZZLe (edited May 17, 2000).]
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Old 05-18-2000, 12:23 AM   #7
Tim Prudence
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Member#: 216
Join Date: Aug 1999
Location: san diego, ca USA
Post

Wait, you got the front sway bar on? How?

Turbo cars have a different water pipe, so that it isn't so close the driver's side header... I don't know how different it is, but a WRX radiator would be expenisive to say the least. I just heat wrapped mine.

I have no pictures, haven't gotten around to taking any...

I have no safeguard, seems like a lot of money for what it is. I just wish there was a way to monitor the stock sensor.
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Old 05-18-2000, 12:36 AM   #8
Tim Prudence
Scooby Specialist
 
Member#: 216
Join Date: Aug 1999
Location: san diego, ca USA
Angry

I don't think that I'm overtuning that much, my o2 readings are a little rich, but it seems to be the same as what everyone else is shooting for with a turbo.

I don't know what my tailpipe looks like because I can't see it while I'm driving, but I've had people follow me and nobody's said, "Dude, you've got fireballs coming out of your tailpipe!"

I guess I could reset the AFC and just use stock fuel w/ rising rate fpr. It should still be adequate, but if it was unburnt gas in the exhaust would cutting back timing really help the problem.

I think that I'm going to try to find my knock threshold (by ear turning up timing with the ITC), and then add a can off octane boost to see if it still occurs. That should tell me if it's really detonation. Though if I buy the wrong can of octane boost it might not do anything whatsoever.
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