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Discussion Starter #1
Ok guys,
Here is the problem. I get lots of knock in the upper rpm range usually 5000 rpms or more. Im running like 20psi of boost my duty cycle is at 105% so I try to turn down my boost all the way down and Im still hitting almost 20 pounds.
Set the boost back up like stock and Im still hitting 20psi. I tried increasing my fpr to 45psi and the car stutters and blows black smoke like mad.
Turned that back down to 38psi does not stutter as bad but I still have really high duty cycle.
I have done boost test after boost test. I found that one of the bolts on my throttlebody is stripped and is slightly leaking.
When I do a leak test should the boost gauge in the car increase? It does not move, is this normal?
I think I just need some bigger inj but Im not sure way the boost wont turn down. I hooked my brother mbc up and it was the same.

What do you all think? Please give me some input.
Thanks
Jon
 

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What are you tuning with?
Figure out your boost issues first. Then turn down the boost until you can afford the appropriate injectors for you setup.

Any boost leak can contribute to over working the turbo and causing knock due to the high intake temps.
 

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Discussion Starter #5
Ok I got my boost down to about 16psi. I have tried to test for boost leaks but Im not sure Im doing it right! When I do a leak test should the boost gauge in the car increase? It does not move, is this normal? Can a boost leak make my duty cycle too high?
I may have a leak on the tb because one of the bolts is stripped.
Im using maft 2.xx right now to tune with and a logger.
Is it possible to have a boost leak AND need new injectors?
Thanks for the help!!
 

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Ok check for boost leaks again, yes it should go up, if not it sounds like you have a LARGE leak somewhere...what are you using to pressure up the system? you need to use a air tank already filled, not a litte air pump for tires, or the electric crap. if you fix and determain and KNOW there are no boost leaks, i have heard in many times while getting no knock but in upper rpms 3+ gears you get knock is a sign of overran injectors. just my .02
 

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AWD_4g63 said:
...what are you using to pressure up the system? you need to use a air tank already filled, not a litte air pump for tires, or the electric crap.
I agree, i have tried using a electric compressor and/or bike pump for years, it never works well.
 

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Discussion Starter #10
I use a electric pump to test for leaks and I never find any.
I would I know if my afpr is bad and how could that make my injectors over run?
I heard if you increase fuel pressue it makes your injectors bigger. Well, when I do that the car bucks really bad under any boost?
 

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jr91gsx said:
I use a electric pump to test for leaks and I never find any.
I bet you will find some if you get a better source of compressed air. BTW your boost gauge should go up in teh car while doing a boost test.

jr91gsx said:
I heard if you increase fuel pressue it makes your injectors bigger. Well, when I do that the car bucks really bad under any boost?
That's probably from that car being crazy rich. boost leaks+too high fuel pressure =way too much fuel: which leads to bucking.
 

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yeah the reason you dont have "boost leaks" is because your using a walmart electric pump! and the air is making its way out faster than you can add and you can never hear becasue of the stupid sputtering noise the pump makes. Get a reliable source and know!
 

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not trying to change subject but you guys seem to know the stuff on leak tests. If you use an air tank and not a cheep electric pump, can that much compressed air damage anything internally? if so how do you control that?

thanks!
 

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Dont let as much in, or just keep the tank pressure to a minimum or around what you are going to run, to equalize the pressures... shouldnt hurt anything? :rolleyes: :confused:
 

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Discussion Starter #15
Im using a really good air compressor not something from walmart.
I even spray soapy water on all my pipes and on the the vac lines.
Still nothing and the boost gauge does not move.
My boost gauge does not have a vac reading on could that have something to do with it?
 

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no shouldnt, wouldnt make sense, but i dont know ive never ran anything but a 30/30 gauge. :D
 
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