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Discussion Starter · #1 ·
I've encountered a knock just a couple of times when under heavy acceleration. I have an SBC-id set to 53 and 13 gain, and during 4th gear load testing, it has usually maxed at about 15.6 lbs of boost, with a small spike up to 15.8 here and there (not often). However, I live in Texas and its getting hotter... so on comes the AC which may produce more load on the engine (even if it is supposed to cut of during WOT).

Anyway, I heard detonation today in 2nd gear for the second time in about a week, so I backed the EBC down to 50 and 11 gain, which seems to max out at about 14.5 lbs of boost (per a 4th gear pull). Now, I feel much safer at this level but it seems that I should be able to get a bit more out of the stock system after reading that most of the people seem to be able to run 15.5lbs or more without a problem. Has anyone else seen detonation at this boost level? Mods are just the SBC-id and Godspeed uppipe at this point. Thanks,
 

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Hmm something doesn't seem right about that at all. I run 51 and get 15.8psi easily. I wish I could offer more advice than to double-check the connections. Also, do you have a mechanical boost gauge in addition to verify 14.x is all you're hitting?
 

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how many days have you left the SBC settings the same?

how long since an ECU reset?

i have found that you have to dial it in (im using 57 and 13 gain, 15.6 psi in 4th) and keep it there. if you continue to monkey with the settings, i think the ECU keeps readjusting and it will pull timing on you if it has to

also it takes about 10 days of driving after a reset for the ECU to get it right...the longer you go with your SBC set at the same numbers...the faster and smoother the car will get...my personal observations

if youve reset recently, it wont be smooth for a while
 

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It's all in your gas. Try getting gas from a different place and get the highest octane you can if not try NOS octane boost.
or what i do is put a bottle of 2 stroke oil in every time i fill up. but i'm running way more boost than you maybe you only want to put in like 1/4 of a bottle.
 

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Ok, sorry for the stupid ?, but what does detonation sound like? How do you know?
 

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I don't think its your EBC. I just started noticing the same problem in my mostly stock WRX. I've been running nothing but Chevron (for whatever reason I get about 25 more miles to a tank with Chevron and its 91 octane (stupid California emissions crap....). My girlfriend's out of town for a few more days so I can't take my car in for sercive unless I want to take a day off and spend all day there, so I'm going to have it looked at as soon as she gets back, but like I said...I don't think its your EBC. mine does it when I acelerate on on-ramps (about 3/4 throttle) and sometimes after I get on the freeway if I'm in slightly too low a gear for the speed (like granny driving). It knocks for about 5-6 seconds and as soon as I ease off the gas it goes away and doesn't come back, but on 200 miles (that's about what I drive on a daily basis), this happens probably 5 times. There's an ECU problem on some cars that was just discovered, I wonder if this has anything to do with it. My performance is also inconsistent...sometimesthe car goes like a maniac, sometimes it a slug...and it doesn't seem to depend on temperature, or anything else.
 

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hokieitr said:
2 stroke motor oil. You've got to be kidding me!
I hope he's kidding. 2-stroke motor oil may increase the likelyhood of detonation because there will be less actual gasoline per injector cycle, and therefore the car will run lean.

This is common with dirtbikes: People think that if they run more premix oil than is recommended they are being 'safe'. Quite the contrary actually.

He's right about the gasoline likely being your problem though, so try a different brand.

-Pace
 

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Discussion Starter · #9 ·
I've pretty much stuck with Chevron gas, but here in Texas we are lucky and can get 93 octane. Occasionally I will get Texaco which is normally 93 as well.

It had probably been about 5 days since a reset, as a re-did some of the wiring on the inside to make the SBC install cleaner. I'm running at 51 set and 11 gain right now and it seems to be better. I read a post by God that the engine should be able to take whatever boost the stock turbo can give, so hopefully everything is fine now.

I only heard it for a few seconds and I think the ECU pulled the timing a bit. For now, I think if I'm accelerating hard I'll turn off the AC, and see about getting colder spark plugs.

edit: It definitely could have been the gas as well -- sometimes you just get a bad tank.
 
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