Performance of twin 2.5” system vs single 4”?

[karlp2]

Hi, have G6ET with 355rwkw, currently have a full xforce system with the twin 2.5” pipes.  Other mods include a Walbro 400, PW stage 1 intercooler, 1000cc injectors,  GTX3582 gen 2 with flapper mod and porting etc.  Had hoped for more kw from the recent tune, a couple people have suggested that single exhaust 4” system would help, thoughts?  Reluctant to change the exhaust unless it’ll make a difference, wasn’t cheap to buy being a full stainless one.  Thanks

[MBAF]

instead of me writing a big spill, click here instead. There is some good information and will get you in the right direction. You also have to take other things into account, that affect power, like temps on the day, dyno etc.

 

There are gains to be had by going to a 4" of course and many equations to play with to calculate, as well as pros/cons of going bigger like, it will be louder, likely hang lower etc etc

Edited 16/04/19 02:26 AM by MBAF

[Puffwagon]

That link reckons a twin 2.5 system only supports 463hp at the crank. On this forum we've seen a twin 2.5 system support more than 670hp at the wheels.

 

Op, post your dyno sheet so we've got more of an idea what's going on.

[MBAF]

yeah that's not taking into account variables or forced induction. VE on a 2.5" twin setup has flow similar to a single 3.5" (again depending on the setup in question) for all we know currently this could be a sub frame back 2.5" and not full system, plenty of variables here

[Puffwagon]

3 minutes ago, MBAF said:

for all we know currently this could be a sub frame back 2.5" and not full system

54 minutes ago, karlp2 said:

currently have a full xforce system with the twin 2.5” pipes

[MBAF]

but "full" doesn't necessarily mean full

[Puffwagon]

Lol perhaps not. I'm sure we'll get to the bottom of it.

[camo86T]

403rwkw 98 / 438rwkw e85 with twin 2.5" xforce here, same injectors, pump and intercooler. 

Fuel setup (no surge) and gt3540 were the next limitation not exhaust

Unless a sedan version doesn't flow as well as a ute but doubt it

@karlp2 was there some query about your tuner....jet had a few comments iirc lol

4" dump and cat to clarify

Edited 16/04/19 03:19 AM by camo86T

[karlp2]

Appreciate your feedback.  Yes I’m looking at other tuner options, nothing really jumping out at me with the rep of tuners here

[karlp2]

2 hours ago, MBAF said:

but "full" doesn't necessarily mean full

By full exhaust I’m talking about from, and including the dump pipe back