404ci with 76mm and .81 a/r ???
Thread Starter
Joined: Jun 2006
Posts: 1,460
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From: Orange County, CA
404ci with 76mm and .81 a/r ??? Hey I have a 404ci LQ motor with WCCH CNC'd edelbrock pro-port heads (215cc runner), edelbrock vic jr manifold, and a 231/227 .614 116 cam.
im currently running on an ebay kit with my original 76mm with .81 a/r housing. it seems to run awesome on the top end, but at part-throttle, the engine goes super lean and feels like its going to explode!
im wondering if i have "part throttle over-boost" where there is too much air coming into the engine at part throttle for the computer to understand. my tuner tried to fix this but there is something else going on besides the tune..... any ideas????
is my turbo just too small??? (this is a 100% street car btw) i like my instant spooling
here is a vid: http://www.youtube.com/watch?v=GGvHxObI5lg
im currently running on an ebay kit with my original 76mm with .81 a/r housing. it seems to run awesome on the top end, but at part-throttle, the engine goes super lean and feels like its going to explode!
im wondering if i have "part throttle over-boost" where there is too much air coming into the engine at part throttle for the computer to understand. my tuner tried to fix this but there is something else going on besides the tune..... any ideas????
is my turbo just too small??? (this is a 100% street car btw) i like my instant spooling
here is a vid: http://www.youtube.com/watch?v=GGvHxObI5lg
Last edited by KILLER-LS1; Feb 23, 2010 at 04:42 PM.
Thread Starter
Joined: Jun 2006
Posts: 1,460
Likes: 7
From: Orange County, CA
and no offense guys, i know it is "small" compared to most, but im looking for an informed answer from someone who has tried it. it might be wayyy too small for your goals, but im wondering if it is mechanically too small to function properly.
i just want my car running properly again :-/
I think anyone on here would tell you that it's too small. Talk to a someone like forced inductions and they will tell you their "informed opinion" which will be that it's too small and creates too much backpressure. What size is the downpipe? 3"?
Thread Starter
Joined: Jun 2006
Posts: 1,460
Likes: 7
From: Orange County, CA
i was at the sema show and spoke to the guys at the turbonetics booth and precision turbo and they all told me, "yeah its small, but it should work ok"
but now im starting to think its not ok, event though it runs great at WOT. im just getting this strange lean condition at 1/4 throttle while cruising
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Verdad Gallardo Thread Starter
Joined: Jun 2006
Posts: 1,460
Likes: 7
From: Orange County, CA
the tuner had it on the dyno for over 4 hours and couldnt get rid of the problem....
could any sensors be causing this??
i have the chevy colbalt 2 bar map sensor, 50# injectors, walbro 255 pump, and stock fuel lines.
im only looking for around 600rwhp on this system right now.
the motor does have my old (90k miles) crank and cam sensors, but ive never had a problem with them before...
**UPDATE**
i just drove around with my wastegate COMPLETELY OFF, and the problem is still there. so i know its not a huge backpressure issue, and i know its not boost related (since the motor wasnt getting any boost)
10 Second Club
Joined: Dec 2008
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I don't do part throttle 1/4 throttle sprints like you speak of, why? cause mine will stay in 13s while building boost. But under full throttle it is at 10.5 to 11.5 depending on the temps out. So why play with the 1/4 spurts?
Thread Starter
Joined: Jun 2006
Posts: 1,460
Likes: 7
From: Orange County, CA
Thread Starter
Joined: Jun 2006
Posts: 1,460
Likes: 7
From: Orange County, CA
It could be your wastegate is too small or inefficient causing an undesired 'closed loop' situation. What size and brand wastegate do you use?
And what psi are you hitting in part throttle?
And what psi are you hitting in part throttle?
Thread Starter
Joined: Jun 2006
Posts: 1,460
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From: Orange County, CA
im only running 7-8 psi right now
On The Tree
Joined: Sep 2007
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It is not too small.... If you think it is getting "too much boost" at part throttle... what do you think supercharged cars do when they have tons and tons of boost at part throttle, at any rpm?
The simple answer is, your tuner sucks or there is a mechanical issue, such as a intake leak, boost leak, bad maf sensor.
Would be best to post some logs/scans, or at least tell us what the wideband does when it 'goes lean'.
You couldnt pay me to let ANYONE tune my boosted car....
The simple answer is, your tuner sucks or there is a mechanical issue, such as a intake leak, boost leak, bad maf sensor.
Would be best to post some logs/scans, or at least tell us what the wideband does when it 'goes lean'.
You couldnt pay me to let ANYONE tune my boosted car....
Thread Starter
Joined: Jun 2006
Posts: 1,460
Likes: 7
From: Orange County, CA
It is not too small.... If you think it is getting "too much boost" at part throttle... what do you think supercharged cars do when they have tons and tons of boost at part throttle, at any rpm?
The simple answer is, your tuner sucks or there is a mechanical issue, such as a intake leak, boost leak, bad maf sensor.
Would be best to post some logs/scans, or at least tell us what the wideband does when it 'goes lean'.
You couldnt pay me to let ANYONE tune my boosted car....
The simple answer is, your tuner sucks or there is a mechanical issue, such as a intake leak, boost leak, bad maf sensor.
Would be best to post some logs/scans, or at least tell us what the wideband does when it 'goes lean'.
You couldnt pay me to let ANYONE tune my boosted car....
at 1/4 throttle, you can hear the engine starting to stumble as afr goes over 15:1, and if you stay at 1/4 throttle or even a little more, the afr pegs out at 20:1 and the engine stumbles and sounds like its knocking.
but all you have to do is step on the gas and it all goes away and drives great with tons of power.
soooo weird. btw im running a SD tune with no MAF.