Boosting in Neutral

[SilversunMSP]

I haven't driven the MSP in about two weeks and went to start it up today. I revved the engine a few times while in neutral and the boost gauge read 7 psi each time. I revved a little harder and the all the way to redline and hit fuel cut while in neutral the whole time.

So then I shut the engine off, checked all the vacuum lines and even the boost gauge line. I couldn't find anything. So maybe a 30 min later I fired up the car again and revved it hard. This time the boost gauge read normal. The engine made vacuum but no boost while in idle.

Anyone care to explain what just happened?

 

[XoX1de]

What the ****?

 

[pavone]

i would just pretend nothing happend.... that is ******. maybe the boost gauge was messed up, im assuming mechanical boost gauge?

 

[SilversunMSP]

Yes, it a cheapo ProSport boost gauge. I was thinking maybe the stock BPV was stuck for a lil bit. It's been really unusually cold here in Florida for month or so and the car has been parked for most of that time.

I haven't driven the car yet, maybe I'll take it out tonight. We'll see what happens.

 

[pavone]

well if with the bpv stuck closed it shouldnt boost anything in neutral cuz there is no load on the motor, when you let off did you here any compressor surge? (or turkey as people like to call it round these parts lol) part of me wants to say the boost gauge was just set inaccurately because the car was sitting and by some chance or even it stuck and did it twice until you turned the car off and it reset itself but i would not be able to explain a single portion of that

 

[JCell]

sounds like the boost gauge got stuck in the wrong setting

 

[PointFive]

Since you were hitting fuel cut, that tells me your boost gauge was most likely accurate. I would say your wastegate door was stuck closed. You shouldn't be able to boost much if at all in neutral because there's no load on the engine.

 

[Wagonbacker9]

I'm going to give a far simpler solution.


DON'T DO THAT!

lol

for the record my money is on the gauge misreading as well.

 

[Outlawstar98]

Just keep a eye for it to happen, but don't rev in neutral, that's soooo a river thing to do. Lol.

 

[Wagonbacker9]

river? wtf... lol....

he means ricer.

 

[XxaltezzaxX]

my prosport acts up a lot too. wouldn't explain the fuel cut though.

i've seen my prosport spike to 25psi will i wasn't even on the gas. great boost gauge

 

[KrayzieFox]

river? wtf... lol....

he means ricer.

BWAHAHA!!

+1 on the Prosport acting up. Mine would read positive pressure under vacuum until I calibrated it properly.. they look so nice, but they are garbage quality. You sure you felt fuel cut? Cuz that makes no sense. As mentioned previously, there is no load on the engine in Neutral.. so boost should not be possible.

 

[thepope540]

Maybe you revved it to the limiter... I can't think of any possible way to hit fuel cut in neutral.

 

[MSP2003.5_Nick]

The stock turbo is so small that you actually can get it to hit quite a bit of boost in neutral. I used to do it with the stocker no problem The only thing is if you're running the stock by-pass-valve then it will let the pressure out before it gets a chance to build in neutral. But with an aftermarket BOV it will build no problem........ not so much with a gt3076r lol

Also if you hit rev limit or fuel cut that actually puts load on the engine and can spool your turbo.

If you've ever heard of two-step launch control they basically do the same thing, except usually with ignition cut for safety but same thing.

Altogether your poopy boost gauge probably messed up. I'd forget anything ever happened.

And now I can go back to creepin the forums without posting and the big write up at the top telling me to post something will be gone

 

[Wagonbacker9]

the stock turbo is so small that you actually can get it to hit quite a bit of boost in neutral. I used to do it with the stocker no problem.

Also if you hit rev limit or fuel cut that actually puts load on the engine and can spool your turbo.

If you've ever heard of two-step launch control they basically do the same thing, except usually with ignition cut for safety but same thing. I'd say it's fine, mechanical boost gauges are the most accurate and have no lag in the reading. I'd trust them any day.

the rev limiter or 2 step cuts fuel/ignition... quite the opposite of load... it just gets you out of vac, not into boost.

 

[mp3-79bronco]

i can hit 4lbs of boost in neutral with a small t3 turbo which is bigger than stock by alot. also with the 2step i can hit 7lbs

 

[Wagonbacker9]

sorry poor choice of words... you're not fully spooling the turbo.

 

[Rush]

My advice? Next time, beat on the gauge a few times before doing anything.

 

[cougar10agREDUX]

the only reason for a 2-step is consistancy, already being full throttle on a launch at te same rpm every time. decreasing lag and getting the turbo to spool is a bonus.

with my 2-step set at 4600rpm i get like 3psi within a second, and if i hold it for a little bit i can get 5psi. but i still got a cat so i don't hold it too long.