would running the wastegate line from the UIM do anything to reduce boost creep? reason being....

my brother has a ca18det 240sx and he is running a line from the uim that is T'd into the line that comes off the turbo and then they both go to the wastegate line. he only gets boost creep on cold cold nights, whereas i'll get 'random boost'. im running an mbc and he's running an apex avcr...i know there is a huge difference.

 

Nothing at all. Boost creep is caused by the wastegate not flowing enough, i.e. not big enough. It has nothing to do with the actuation of the wastegate. He also has a completely different turbo! It's got nothing to do with the lines. No difference at all. Boost controllers, whether pneumatic or electronic, can do nothing for boost creep, for the reasons explained above.

 

so basically i gotta find the 'sweet spot' of the MBC to where it doesnt spike it too high.

reason being:

Last night i was driving hard and the wastegate line popped off. I was from then on out getting 1 bar on WOT at 5krpm (stomped it on the highway). The car (amazingly) pulled like it never has before. This also applied to first, second, and third.


One out of every 4 pushes it would go above 1 bar.


Thanks NZ for chiming in. Your knowledge is far greater and i trust your opinion

 

BDC has recommended running the wastegate line off the UIM to me for another reason. He claims it can diminish between shift lag as the off throttle vacuum will assist the spring in slamming the WG shut.

Just incase someone is wondering "who the hell would run the WG off the UIM?"

 

I run mine off the UIM for convenience and it works dandy.

 

Which nipple on the UIM?

 

I run my GReddy boost gauge, BOV and stock boost sensor off a nipple on my UIM. Its on the passenger side behind and above where the ACV was.

 

It's make it worse.


-Ted

 

Ted is right... When you run the source after the intercooler, you actually get more boost... you loose boost through your intercooler and therefore if you put the source after, your wastegate will not open until it sees what boost it was seeing from the turbo... anywhere from 1-4psi more!

 

Wouldn't that be a "good" thing?
I mean, if you want to more accurately control what amount of boost is going to the engine, wouldn't that be better?

For example, if you want 8psi boost in the motor and you have the wastegate before the IC, you would actually want to "hedge" in a 9-10psi boost on your wastegate, right?

But if you have it after the IC, you set it at 8psi and that's what you get to the motor (theoretically of course). Yeah, you may be running 9-10 through the IC, but it seems like this would give you more (more accurate) control of what you're wanting.

Am I simplifying this too much? Please tell me if I'm way off base here.

 

As the wastegate vacuum source gets farther away from the turbo itself, the more aggressive the initial boost will hit (i.e. boost spike).&nbsp Having the WG vacuum source at the intake manifold puts it the farthest away from the turbo, so this will give it the most aggressive boost ramp.&nbsp The original poster was worried about boost creep; this is not a good away to minimize boost creep.


-Ted

 

I actually don't think you are way off base here

To me it seems that you would want the wastegate to release based on how much pressure is going into the engine. The closest place to read that would be on the intake manifolds somewhere, after it dropped off through the I/C. Cause if its before the I/C, then you are venting 10 psi or whatever there, which only ends up being 8 psi or so in the engine.

But then maybe I'm totally wrong too.

 

so you'd get higher boost by putting the wastegate actuator line after the IC, but it'd be safer to put it near the turbo to make the wastegate open sooner and whatnot?

hmmm...
this just gave me a thought. for a boost gauge, would you want to put it close to the turbo, or far away? it seems like farther away, so that you would know what's actually going into your engine, rather than what your turbo is producing.

kind of off topic, but what is the best vac line to splice te boost gauge line into?

 

Good, well at least I'm not the only one thinking this way. My thought is that as long as I've got an IC that will handle a little more than what I want to run into the engine, this seems like the ideal setup. And I would have to agree with bigretardhead then also that a boost guage at a similar location would give the most accurate picture...

If I'm wrong, someone please tell me -- I'm kind of just thinking out loud here, but I'm also gathering all of these facts in prep for my own turbo setup... Would like to do it right the first time.

 

Not necessarily higher boost, but more aggressive boost ramp...&nbsp The wastegate stays closed longer since the pressure takes time to travel from the turbo through the pipes, IC, TB and then the intake manifold (where you've got the vacuum fitting for the WG).&nbsp It's safer to keep it at the turbo...


That is correct.


"Best" is relative.&nbsp Best would be some kinda solid hard line that can handle the heat.&nbsp Most people use thick-walled silicone hose that is more heat resistant than most rubber compounds.


-Ted

 

I think he meant which line on the engine; not what type of line.

The pressure sensor line or the BOV line are both easily accessed, and will work fine. The BOV line is probably better, becuase it doesn't have a pill in it like the pressure sensor line, which will slow the gauge's response slightly.