boost just dropping off why?

[123lilc]

ok so i have been experiencing boost drop off ever since i bought the car. and could not figure it out. Its not a boost leak, but i could be wrong. So when i set my REVO SPS+ to stock mode it peaks at 15 PSI and Holds at 15PSI until i let off, and that's what it supposed to do. Now when i turn up the boost on the SPS+ (6) i get peak of around 28PSI (depending on weather) and then it drops down to 25 then keeps dropping until it holds around 22PSI. and once you get past 5500 RPM it just drops to 5PSI. Im at such a loss i have no idea. so ideally what i want is to peak at 28 and hold 25 all the way to redline or untill i let off. if anyone has any clue please help me out as this is quite annoying.

So this may be have been pointless and stupid but i removed the line that goes to the wastegate from the N75 just to see if the N75 was being stupid. what i got from this was the gauge shot up and hit 30PSI for a split second then with my foot still to the floor it quickly dropped to around like 11PSI. I don't understand how it would just drop boost without the wastegate opening. Ugh all i want is for my car to hold 25 PSI thats all i ask

Car is 02 5MT quattro with GTX2863R with all supporting mods and REVO stage 3+ tune

Any help at all is appreciated!

[NickN]

Kind of sounds to me like the diverter valve is leaking internally. How's the DV?


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[fyremanpat]

boost leak

[customa4]

For starters take some logs of requested vs actual boost. Do a WOT(wide open throttle) pull in 3rd gear.

[123lilc]

boost leak

If its a boost leak how come it holds 15 PSI ??? is it possible?

[123lilc]

Kind of sounds to me like the diverter valve is leaking internally. How's the DV?


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Its a FORGE 007, wouldn't it make a woosh sound if it was opening up and leaking?

[redline380]

My money is on N75. It is giving pressure to the line to pen up the gate.

However, this does not necessarily mean the N75 is bad. If the ECU is giving it the signal to open, then it is obliging.

What is wastegate pressure on the turbo? Anything above 5psi and you have other issues as well

[NickN]

I don't think so. A forge 007 is a pretty standard aftermarket DV and I think 28 psi might just be a bit much for it with the original spring. My guess is that you're hitting 28psi and the DV is letting go because it can't hold the pressure and doesn't reseal until you get down to 15psi. That wouldn't cause any whooshing sounds because it's only opening and closing once. You might hear something initially when it opens at 28psi.

Does it consistently stay around 15psi after it falls off from 28?

How old is the DV btw?


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[123lilc]

For starters take some logs of requested vs actual boost. Do a WOT(wide open throttle) pull in 3rd gear.

Question. could this be from the compressor housing leaking?? whenever i do a boost leak test at the TIP i hear oil bubbling (i read that is normal) but i just keep pumping air into the system and it just bubbles and looses all air no pressure will build up. i thought nothing of it and just tested the lower intercooler pipeing and that had no leaks. So i might have just answered my own question but do you think that the comp. housing would cause this??

[123lilc]

I don't think so. A forge 007 is a pretty standard aftermarket DV and I think 28 psi might just be a bit much for it with the original spring. My guess is that you're hitting 28psi and the DV is letting go because it can't hold the pressure and doesn't reseal until you get down to 15psi. That wouldn't cause any whooshing sounds because it's only opening and closing once. You might hear something initially when it opens at 28psi.

Does it consistently stay around 15psi after it falls off from 28?

How old is the DV btw?


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Hmm i have not thought of that i will check into that
also im not sure how old the DV is

[NickN]

Did you buy the car with it installed?

Also, try smoke testing to find leaks instead of pressure testing. It helped me find my boost leaks much quicker.


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[123lilc]

Did you buy the car with it installed?

Also, try smoke testing to find leaks instead of pressure testing. It helped me find my boost leaks much quicker.


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yes i bought it with the car

this is probably a stupid question but how do you do a smoke test??
i googled it and i dont understand

[customa4]

Pretty much fill the system with smoke and then add air pressure. The smoke will exit the boost lines wherever there's a leak.

[redline380]

this is probably a stupid question but how do you do a smoke test??
i googled it and i dont understand

Grab a box of stogies, I like Arturo Fuente Churchills. Maybe grab a buddy to double the amount of smoke. Start puffing into the turbo inlet and see where the smoke comes out.

A decent whiskey is not necessary but a highly recommended accompaniment. I prefer something like a Crown Royal XO.

[123lilc]

Grab a box of stogies, I like Arturo Fuente Churchills. Maybe grab a buddy to double the amount of smoke. Start puffing into the turbo inlet and see where the smoke comes out.

A decent whiskey is not necessary but a highly recommended accompaniment. I prefer something like a Crown Royal XO.

Yea thats not going to work out to well with my parents considering im 16
dad will be more than happy to help me out with this haha

[redline380]

Yea thats not going to work out to well with my parents considering im 16

My bad. Looks like it is going to be bubble gum cigarettes and grape soda for you.

But ya know, I did lots of naughty things when I was 16 and have hardly spent any time in jail.

Just noticed something- it is 1:17pm and you are on AZ. Get back to your class work young man. (I say that and I am in class too!)

[123lilc]

My bad. Looks like it is going to be bubble gum cigarettes and grape soda for you.

But ya know, I did lots of naughty things when I was 16 and have hardly spent any time in jail.

lol thanks for the help

[123lilc]

Just noticed something- it is 1:17pm and you are on AZ. Get back to your class work young man. (I say that and I am in class too!)

haha! you caught me!