so I've been having bad boost creep recently...
 

on my t04E setup with HKS 40mm WG. Despite the WG testing good and opening at 8psi every time during testing (cold and hot) I started getting creep as high as 18psi. I assumed that the combo of the ported engine and the smaller turbine housing I'm running was just too much for the standard WG, and bought a 50mm to replace it.

Today I removed the DP in order to get at the WG, which had the WG dump plumbed back into it, and a flex section in the WG dump. In fact, I was removing it because I already had my old WG sold, and my new WG in hand.

Low and behold I found the reason for my creep. The flex section in the WG dump tube had eaten itself up, apparently melted inside. Instead of being 1-3/4" ID, the flex weave had shrunken down to about 3/8" ID. The outside of it still looked perfect.

So, there's a lesson learned, always check the dump tube for restrictions when having boost creep on an external WG. IF not, you'll feel like an idiot, about like I do right now :dunce:

inside of the flex...

https://www.rx7club.com/attachment.p...hmentid=129397

:eek:

The only thing is, now I'm paranoid about putting a new flex section in my new dump tube. It's said the dump will crack if no flex is used, plus it helps a LOT in removal and installation later on. But, I sure as hell dont want this to happen again, and I dont know of any flex sections that are specifically made for a turbo rotary's extreme heat.

Try contacting A-spec, and see if they've had these issues. I know they usually include flex sections in their downpipes. If they arn't having these same issues, then i'd purchase one through him.

As far as cracking without a flex section, I don't think Damian is running a flex section on his track car, and he doesn't seem to have any issues. There's also quite a few others running a downpipe without a flex section. Might be worth searching around about the topic. From what I understand, cracking is usually caused by FWD/transverse engine layouts. (I'm sure you already know all this though, so maybe it'll atleast help someone else! :) )

If you can find a flex section that can hold up, then there's no reason not to play it safe, and get it!

-Alex

why don't u just vent the WG to the atm and be done with it?

Maybe because some people don't like the noise, and don't like getting pulled over everytime they go out. :rolleyes:

-Alex

Yeah, I HATE super loud exhausts. I bought a $250 Rb presilencer to weld into my midpipe to get the thing quiet like I like...it gets compliments all the time.

Venting to atmosphere is not an option for my tastes.

It is said that the WG dump tube expands and contracts much more rapidly because of the WG opening and closing all the time, which leads to cracking much faster than a regular exhaust that heats up all of the time.

I've worked with DP dumps that had no flex in them, and it is a BITCH to remove and reinstall.

sounds like a catch 22...

if u want it quiet.. u gotta keep changing flex tubes every so often...
or use a solid piece and hope u never have to take it off for a long time :P

How in the hell did you keep the engine from blowing with so much creep? That's 10psi creep :eek:

why don't you replace the flex w a slip fit. they are easy to make. cut the pipe in the middle, slice off another piece of similar dia pipe. wrap it around one of the pipes and weld it.

i run my twin TO4 setup w 2 3 inch downpipes to the midpipe and one of the DPs is a slip fit i made. no leaks, no sweat.

good luck,

howard coleman