Lost boost after exhaust Mod.

[R31/4 GTT/S]

Lost boost after exhaust Mod.

Hi guys,

something Wierd happened to my r34 GTT like the title says I've lost boost after installing a just jap bell mouth dump to cat. 

Nowmy previous setup was just a blitz cat back and I saw 9psi. 

Now ive installed the turbo back jjr bell mouth and gutted my cat I'm only getting 7psi. 

I would of thought freeing up the exhaust would give me more boost or the same. 

Can someone tell me where I've gone wrong ? Is it cause I gutted the cat?

any help would b much appreciated 

thanks. 

[Jonic]

Have you tried resetting the ECU, by taking your battery out and let it reset ?

[KiwiRS4T]

Any difference in performance? Boost pressure is just resistance to flow - better exhaust may be giving you better flow.

[Dose Pipe Sutututu]

56 minutes ago, Jonic said:

Have you tried resetting the ECU, by taking your battery out and let it reset ?

that's not going to do much, all you're resetting are the long term fuel trims

[GeeDog]

Wastegate flapper catching on new dump pipe, and not closing fully?

[R31/4 GTT/S]

CAr still pulls hard, it's just that I've lost a couple of psi.  

Same boost gauge nothing's changed besides the dump to cat pipe. Ohh and gutting the cat. 

If I flaw it in 4th it hits 8psi but Sits on 7psi for the most part. 

I always thought freeing up the exhaust would increase boost not decrease it. 

Anyways I'll look else where but any ideas are very much welcome!!

cheers 

Ash

[GH05T]

what is controlling your boost? standard solenoid?

[mr_rbman]

Just gutted cat....or put a pipe through it?!

Just gutting can cause turbulence which could be causing your boost issue....

[KiwiRS4T]

3 hours ago, R31/4 GTT/S said:

 

I always thought freeing up the exhaust would increase boost not decrease it. 

 

As I said before it will increase flow and therefore may increase power. Pity you didn't do an 80 to 120 time before so you could measure it after and see if your car is actually going faster.

Get a simple boost T or something and see if you can raise your boost again - it should make more power at the same boost level or you could go to 10 or so.

[Dose Pipe Sutututu]

6 hours ago, GeeDog said:

Wastegate flapper catching on new dump pipe, and not closing fully?

more likely this

[89CAL]

I would expect reducing restriction post turbo should help increase boost not decrease it.

As above, I know here have been some issues with JJR Dumps in the past so it could be that. I wouldn't stress too much about it. As above, car is probably just as fast/faster and you can easily bump it back up to 9psi if you want to with a manual boost controller

[R31/4 GTT/S]

Cars using standard solenoid. With earth mod.   And I just gutted it didn't put a pipe through it. 

Ill check the waste gate to see if it's sticking. 

Im thinking turbulence in the cat

[GTSBoy]

Simples.  Drop cat + back half of exhaust, go for quick drive.

[R31/4 GTT/S]

Did this no difference. Also Had the boys in blue make a showing. f*k wit neighbors. 

Looking at the standard dump pipe the wares gate opens and the gasses hit the cast iron almost straight away.  (Hope yous know wat I mean)

with the bell mouth the gasses flow more with the flow coming from the exh wheel. 

Me thinking old dump was restrictive giving 9psi now more flow I'm seeing 7psi 

but this all contradicts what I originally thought. 

[KiwiRS4T]

Hopefully you are now making a little more power. To maximise your gains get a boost T or EBC and wind your boost up to 10 psi.

[R31/4 GTT/S]

Cheers guys.