Benefits of 2.5" diff back - Page 6 - Perth-WRX.com

slugwrx · #51 21-09-2007, 07:11 PM

dude maybe its more along the lines of

a - maybe some people dont give a shit about gaining an additional 2 nm of torque due to a 2.5" catback and have better things to do than fuck arse around with tryin to gain that bees dick more low down power from what may seem a pointless mod to some...

b - they dont care what other know it alls think & are maybe sick of hearing people who claim to know what theyre talkin about, when it seems they just know how to use google & ctrl c & ctrl v...

c - they're more than happy with the 3" they already have, whether it be a cheap china system or a bloody titanium system that has double overhead foxtails & chrome grease nipples, they're happy havin that smidgin of a disadvantage...

and your right, maybe some here should sell there wrx's & buy 6L holdens if theyre that set in there ways & are chasin that extra torque...

tuna · #52 21-09-2007, 07:32 PM

Quote:

Originally Posted by maddog

^ exactly, no one has lost an eye yet.

Kato, go look at a MMS system. The bends are not perfect and act as a restriction...

Phizzle, cost is no extra to order a 2.5" rear when you first do an aftermarket exhaust...

If you think a 5% gain across the bulk of the RPM range is not worth it wake up. Power and torque gained in the low RPM range is logarithmically more valuable than the top end for track use. Exit speed, exit speed, exit speed.

And did I mention I just hate those straight through china spec exhausts...

yet you didnt think avcs wasnt a worthwhile mod? strange...

Intra · #53 21-09-2007, 08:30 PM

2.5in might be great for a td04 running 1.1 bar.

Application people.. application.

Who here runs 1.1 bar these days?

tuna · #54 21-09-2007, 08:41 PM

boost = torque.

WRXTASY · #55 21-09-2007, 08:51 PM

Straight from MS himself just to add more fuel to the fire....

Quote:

If you logged the air flow Grms you would see how much better it flows more air at low speed, I had a play with both on an 06 2.5 sti, the 2.5" diff back made around 20% more air flow below 4k, made max boost sooner and was better to drive around town at 2-2.5k, top end flow was so close it was hard to call, heat soak run would see more difference from the two, also the 2.5' set up took more timing all over as well....

Yes as Intra said..APPLICATION....
There is no mention of boost max levels nor the Turbo used either...

But Boost sooner = torque sooner

Enjoying this thread immensely just like the old Perth-WRX we luv

RichX · #56 21-09-2007, 09:05 PM

I don't reckon going a 2.5 diff back would make a noticeable difference.

If you are talking qtr mile times, it might shave off 0.2 of a sec if that ..

NIX WRX · #57 21-09-2007, 09:23 PM

Hang on for a sec guys, I just gotta make some more popcorn...

tuna · #58 21-09-2007, 09:23 PM

maybe 0.002, 0.2 and we would see it on v8 super cars.

Hurtenstein · #59 21-09-2007, 09:24 PM

0.2 is massive in 1/4 mile times.
I'd be stoked if a tiny mod like that gave me 0.2 sec

EDIT: beaten by 0.2 of a second by tuna.

msgofast · #60 22-09-2007, 06:13 AM

Quote:

Originally Posted by WRXTASY

Straight from MS himself just to add more fuel to the fire....

Yes as Intra said..APPLICATION....
There is no mention of boost max levels nor the Turbo used either...

But Boost sooner = torque sooner

Enjoying this thread immensely just like the old Perth-WRX we luv

Max boost was 18psi low end, off to 1 bar up top,tune was 11:1 mid to top, it was a std 06 sti turbo, silicon intake, std air box and CAI system was also std.

This is the said car with the 2.5" diff back and his graph was done week after my road tune, I have since done some more tuning with cams and got 5kw more from start to almost finish, top end was 2-3kw better and holds peak power within 2 kw to redline.
http://www.rexnet.com.au/forum/index...howtopic=72126

There is no doubt one size does not fit all, it's all about match mods to your set up, you don't fit 272 cams with a VF34 and think you will make big gains, anyone care to "guess" why you would loose power all over on that? Small clue is cam over lap and cylinder pressure / fresh charge ratio, which is also why different exhaust sizes for different HP rates will help when you select exhaust size / power output.

Don't take my word on anything, go and get all the bits make your own stuff and up and go to the dyno and test, test, test.

BTW as you straighten out the 90deg bends at the rear, you move peak torque up the rpm band, so in affect of that you start to loose power under peak torque, and yes you do gain some up top, going from 3" with 2 x 90 deg bends to straight pipe lost 10kw at 3500, but gained 3kw at 6500, if you drag race this might be what you need, but if it is a street car you want power soon as you can, you will feel 10kw more low end than 3 up top.