Today, I went to get tuned for 15 psi(using an MBC) and I have a major problem. I hit peak boost at about 6000 rpm and then the boost just falls on it's face. I just installed the new Lovefab Cast Sidewinder, t3/t04e .63ar .57 trim, 81mm 9:8.1 CP pistons and Eagle rods. checked for boost leaks but can't find any. Could it be my wastegate spring for my 38mm Tial is too weak? It's a .5 or .3 bar one. It's not the MBC because I switched it and it does the same thing... WHat do you guys think?

 

help...

 

Johnny, I had the same problem with a MBC that I bought from Titan Motorsports. It's a good unit, but it was acting up on me on the dyno.

I had originally turned it counter clockwise (to increase boost) and the car was making 5.5 psi (stock GReddy internal gate setting). I turned it another full rotation for boost pulls, and got it to make 8psi, but then, like yours, the boost would reach 8 and sharply fall off all the way to redline.

We checked for boost leaks, and found nothing. I thought it may have been injector seals leaking out boost, so we tightened my fuel rail down very snugly, still had the same problem.

My goal was to tune at 10psi, so I cranked it open a bit more. We eventually hit the 10psi, and the MBC held perfectly. I think that those things can be tempermental (MBC's) and adjusting it slightly may solve your problem. Try turning it slightly up, or down... if that doesn't work, shell out the $ for an electronic controller.

- Louis

 

Another theory I have is that with the design of the sidewinder, since the turbo is pulling out the exhaust and it flows straight out to the tial, it forces the tial open on it's own causing it to not be able to hold the boost. Hard to explain, but I think that's what it may be. I think a stiffer spring may remedy this but I have to find one first.

 

bumpy for other opinions...

 

Or could it be my BOV leaking? It's a DSM uncrushed...

 

It shouldn't be that the BOV is uncrushed, because DSM's run more than 8psi stock.

 

but i'm running 1.2 bar...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jonnybravo &raquo;</TD></TR><TR><TD CLASS="quote">but i'm running 1.2 bar...</TD></TR></TABLE> I would think it would be the BOV I had a similar problem when the dyno operater hooked up the boost plot line to my BOV line he just took it of the BOV line and plugged in his boost plot line. Once it hit higher boost it opened and dropped off as the rev's came up. Get a real BOV you cheap skate.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turbozxi &raquo;</TD></TR><TR><TD CLASS="quote"> Get a real BOV you cheap skate.</TD></TR></TABLE>

LOL... I might just have to.

 

damn. it seems like i have the same problem. hell, i have lots of problems as we speak. i could have the boost at set at 7 psi and it would creep to 12 and fall down, like the wastegate is opening too much, and bleeding boost.

 

If you have the .3 bar spring that could very well be the problem.

On another note, it's 9.8:1, not 9:8.1.