Faster on low boost then on higher boost
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Teching In
Joined: Mar 2010
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Faster on low boost then on higher boost ok this is what I have its a ext cab 99 Sonoma with a built 5.3 running stock computer, has 243 heads lil johns custom piston and one of his cams. I have a s480 running a frozen boost water to air type 15 on pump 93 and snow performance stage 2 with dual nozzles, all going through a th400.
Here is my question on 15lbs of boost truck went 6.60 at 104mph turn it up to 22lbs of boost and truck went 6.84 at 100mph. What could be causing truck to go slow I would thing it would pick something up by turning the boost up but this is my first boosted vehicle so I am a little green when it comes to boost.
Thanks in advance for any help anyone can give
Here is my question on 15lbs of boost truck went 6.60 at 104mph turn it up to 22lbs of boost and truck went 6.84 at 100mph. What could be causing truck to go slow I would thing it would pick something up by turning the boost up but this is my first boosted vehicle so I am a little green when it comes to boost.
Thanks in advance for any help anyone can give
Thread Starter
Teching In
Joined: Mar 2010
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AFR was 11.50 at 15lbs there is 15* of timing and at 22lbs there is 13* of timing AFR was 11.30, AIT start at 65 and at end of run was around 80 I have a 7 gallon ice box with a rule 2000 and 1in water lines. I am also running straight meth in meth kit and it sprays on the intake temp sensor
Without an actual log of the run, anything said here is wild speculation. What you have as commanded timing and AFR may not be anywhere near what is really happening. That is without even delving into the realm of pressure leaks, slippage, and other possible issues.
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Thread Starter
Teching In
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i spent all day yesterday testing for leaks because that was my first thought. I don't have access to logs now but can post when I get home I am a truck driver so problly will be next weekend. AFR and timing was what I was commanding.
Let me ask this if I was blowing through the converter or had trans slippage is there something to look for in logs seeing its th400 no trans info in logs.
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Thread Starter
Teching In
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i figured out the problem back pressure is part of the problem around 3 to 1 but also took turbo apart and took some measurements and found out I don't have a s480 have s475 with the 83mm exhaust wheel. I also believe I out of turbo
thanks for everyone's input
thanks for everyone's input
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Joined: Oct 2016
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From: PDX-OR-USA
Maybe the extra power was slipping the tires? Maybe your at the edge of what your suspension and tire combo can handle? Tires would not have to full on break loose they may have just been slipping a small amount. I've had tires do this when they got too old road racing so I'd imagine drag situation could be similar,, rubber hardens with cycles and age..
I think stock48 on here went faster mph in a full size 4wd truck (heavier than yours by 500 lbs at least right?) with the same turbo so you might look into that. Have you checked valve springs aren't floating and spark is still good, maybe a bad coil or two or plug gap too wide.
I had an LQ4 in a 3300# car go 115 1/8th and 145 1/4 with the same turbo. I had a tiny cam though 216/216 and pac 1218 springs. I think that is somewhere on here too from a few years ago.
I had an LQ4 in a 3300# car go 115 1/8th and 145 1/4 with the same turbo. I had a tiny cam though 216/216 and pac 1218 springs. I think that is somewhere on here too from a few years ago.
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You're not out of turbo on a 5.3. If you have 3:1 backpressure, you have a major issue somewhere.