building boost in nuetral???

[starr]

i have a 98 gst 5 speed. i can sat in nuetral and rev my engine up a lot and build my boost all the way up to 12-15 psi, and my blow off valve pops off super loud. my freinds say this is really weird, and abnormal. but they have other turbo cars, not dsm's. anybody know whats' up here?

 

[paranoidTSi]

Interesting, I own a 95 Eagle Talon TSi AWD, when I rev it in Neutral I'll get about 5PSI, you'll push some boost in neutral no doubt, but I don't think its normal to reach full boost in neutral...but it might not be a bad thing either.

 

[herovueboi]

i have a vid that shows another talon building boost, i've heard it's really not good and you shouldn't rev it while in N. just my .02

 

[DSMSpyder99]

i also can only get 3-5 psi. I thought only Automatics build boost up in Nuetral

 

[FourG63 97GST]

I can build about about 10-15 in nuetral also if i rev to 6 grand

boost had nothin to do with what gear its in, if there's load on the engine, it will build boost

 

[kpt4321]

There's nothing wrong with building boost in neutral.

However, building 10+ psi indicates that something might be wrong. Is your base timing set right?

 

[JoeWagon]

Originally posted by kpt4321
There's nothing wrong with building boost in neutral.

You're right, it's just not good to rev to 6 grand in neutral.

 

[CowPimp]

I have heard that it is bad to build boost in neutral as well. I would like to hear an explanation as to why...

 

[Defiant]

It's bad because the engine has no load on it, which in essence is the same as having a load on it all the time in all directions. When you're pushing the car through the air, the crank, rods, timing belt and exhaust are fighting to spin. They're under stress as they push, and vibration and torsional flex are countered. Under free-revs, nothing stabilizes the secondary and tertiary deformations and unloadings. So instead of flexing things in one direction (or, the other under decelleration), you're flexing it back-and-forth. Metals don't like that sort of thing. It is bad.

 

[CowPimp]

Originally posted by Defiant
It's bad because the engine has no load on it, which in essence is the same as having a load on it all the time in all directions. When you're pushing the car through the air, the crank, rods, timing belt and exhaust are fighting to spin. They're under stress as they push, and vibration and torsional flex are countered. Under free-revs, nothing stabilizes the secondary and tertiary deformations and unloadings. So instead of flexing things in one direction (or, the other under decelleration), you're flexing it back-and-forth. Metals don't like that sort of thing. It is bad.

Ah, I had to reread that an extra time, but I understand now. A much better explanation than "it's bad."

This made me rethink the proper way to launch an AWD car. I understand the launch is very stressful, and I like to minimize the potential stress and damage the occasional time I feel like trying to launch. Instead of revving the car high in neutral and bouncing the throttle to create a little extra boost in neutral, one could just use method of launching:

Hold the tach at about 4-4.5K and quickly slip the clutch at the same time as bringing the throttle to the floor. This way, the boost doesn't come on until the drivetrain starts to put up some resistance. Granted, the clutch takes some abuse, but this is better than the transmission taking the abuse in addition to the various engine parts being jerked all around as a result of neutral boost building.

 

[Diceman19]

i believe that is the way buschur says you should do it that way. i dont remember where i read that though. i got a hard launch when i did it.

 

[Enigma_Man]

Originally posted by Defiant
It's bad because the engine has no load on it, which in essence is the same as having a load on it all the time in all directions. When you're pushing the car through the air, the crank, rods, timing belt and exhaust are fighting to spin. They're under stress as they push, and vibration and torsional flex are countered. Under free-revs, nothing stabilizes the secondary and tertiary deformations and unloadings. So instead of flexing things in one direction (or, the other under decelleration), you're flexing it back-and-forth. Metals don't like that sort of thing. It is bad.

Are you sure about that? An engine connected to the drivetrain (through the clutch) wouldn't really have any different loads on it than when just free revving (though it just can't rev as quickly).

The crank, pistons, and what have you are all doing the exact same things whether they're trying to spin a flywheel or the actual wheels, I'd think.

-Jesse

 

[Gabe92RTTT]

Originally posted by starr
i have a 98 gst 5 speed. i can sat in nuetral and rev my engine up a lot and build my boost all the way up to 12-15 psi, and my blow off valve pops off super loud. my freinds say this is really weird, and abnormal. but they have other turbo cars, not dsm's. anybody know whats' up here?

Do you have an aftermarket ignition? Chipped ECU?

 

[CowPimp]

Originally posted by Enigma_Man
Are you sure about that? An engine connected to the drivetrain (through the clutch) wouldn't really have any different loads on it than when just free revving (though it just can't rev as quickly).

The crank, pistons, and what have you are all doing the exact same things whether they're trying to spin a flywheel or the actual wheels, I'd think.

-Jesse

He's saying that they are doing the same thing, but there is nothing stabilizing them as they do the same thing. This causes the excess vibration and flexing.

 

[Defiant]

Originally posted by Enigma_Man
Are you sure about that? An engine connected to the drivetrain (through the clutch) wouldn't really have any different loads on it than when just free revving (though it just can't rev as quickly).

The crank, pistons, and what have you are all doing the exact same things whether they're trying to spin a flywheel or the actual wheels, I'd think.

-Jesse

There's just not enough load in a flywheel, and once it's "flying", there's very, very little load. It's not fighting wind and road resistance like the whole car is.

 

[noz]

woooh...thats a lot of boost in neutral...something i dont' get...