not boosting properly

[mozzandherb]

I just finished upgrading my exhaust from 2.25" to 3" and now my car is not boosting at 8lbs which it is tuned to, it stops boosting at around 5-6lbs. Now I'm wondering if it could be the spring in the w/g or is it possible that with the bigger exhaust this could happen? I'm having the car tuned again on Monday, so I'm not really concerned, but it just seems strange..any ideas?

[WiKKeDV16]

that's kinda odd but not really..

Think of it this way

Dsm setups usually have boost spike because the wastegate port isn't large enough to expell the exhaust gas fast enough I.E(Slow the speed of the turbine shaft/maintain X psi)

In upgrading to 3" exhaust you now have a lot more flow capabilities
I don't remember your setup..is ur wg dumped back into the exhaust? Recirculated? If so..now with 3" exhaust.. the wastegate can effectively control boost via not having a restriction

In short..your wastegate NOW is at its proper psi VS before it was spiking a few lbs. Due to not being able to eliviate the pressure accordingly..make sense?


Edit: just to clarify..I know your setup isn't dsm...lol..that was soley my example

[mozzandherb]

makes perfect sense, thanks for the explanation.
Oh and my w/g is dumped back into the exhaust

[MRX]

makes perfect sense, thanks for the explanation.
Oh and my w/g is dumped back into the exhaust

exiting it back into the exhaust tends to make it boost higher as well

[h22sparkle]

whens the last time you boostleak tested the car? boostleaks can occur at anytime. As far a lower boost lower because of the exhaust highly doubt it.

[mozzandherb]

yeah I'm thinking a boost leak or possibly the spring

[MRX]

does it take a really long time to get to the 5-6psi as opposed to before?

[WiKKeDV16]

simple test..unbolt wg dump from wg..urs is welded so u can't remove..but unbolt it so there's a leak..see if ur boost returns back to how it was..

[WiKKeDV16]

whens the last time you boostleak tested the car? boostleaks can occur at anytime. As far a lower boost lower because of the exhaust highly doubt it.

Not true sparky..

Think about it..yeah he upgrade to 3" exhaust.. ud think the boost would rise right? But his wastegate can now properly ]leed off excess exhaust gas(it's a job). Were as before it had a bigger restriction (the smaller exhaust size)

Why do you think the dsm guys do the flapper mod for their internal wastegates? To eliviate boost creep

What causes boost creep? Inabilitiy to properly vent.


.02

[chessboxer]

The los is correct, as it is all a simple matter of the air getting out where it can get out. before, it had an issue with extra backpressure in the smaller tube letting less air out of the wastegate. Now that the flow is not as restricted, the wg flows better and boost does not go as high.

[mozzandherb]

OK I have had a difference of opinions on this one, but I re-routed a hose from the wastegate to the intake (as pictured below). This is how my set-up is now and this is where I believe I lost some boost.



The second pic is how my set-up was. As you can see the hose from the wastegate was routed to the right hand corner of the head of the motor and then to the IM


My question is, which way is the right way? I don't have a boost controller and the way it is routed now (first pic) would seem like I have lost some boost. The second way it was routed I had full boost. Anyone have any ideas?

[WiKKeDV16]

If you run the wastegate source to the intake manifold you will produce higher boost levels, because the intake manifold is seeing a lower positive pressure vs the charge pipe directly after the compressor outlet.. all forced induction setups have pressure drop..some more than others..usually its 2-3 psi. So you could intiailly be building 10psi..but by the time you get to your intake manifold its now at 7psi...

This is why you see a higher boost reading. Because your wastegate is being feed less boost(via your intake manifold) less psi means it'll take more load(more psi) for the wastegate to open.

Were as hooked up via your charge pipe..the 10psi(just using a common number) is being feed to your wastegate allowing to to open at a sooner time(meaning your actual Positive pressure going into the motor is lower.


how I would set it up

Tee your boost gauge into the same line as your wastegate going to the intake manifold. Charge pipe psi isn't important(genernally) because its not what were actually introudcting into the motor. Its only relevant when you want to figure out how close you are to your efficiency island or things of that nature.

[mozzandherb]

When I had it tuned the software said it was running at 7.4psi. In your opinion do you think it is better to run it the way it is now, or the way it was?

[WiKKeDV16]

I edited my own post..as I felt I was confusing..and needed to correct a few things..and in doing so answered your question ironically..lol

[mozzandherb]

well explained, thanks.