2.5" or 3" exhaust system

[Scutch]

Which is the best to go for when considering a remap with all those other bits and pieces I've mentioned in 483 other threads?

I have a 2.5" Afterburner Vortex and Magnex centre section at the moment, and was considering a 2.5" or 3" Blitz NUR Spec. Will it make that much of a different to power output and noise?

Danke once again ;)

[benm]

I'd go for a bit of a longer one myself. Its a fair distance from the engine to the back of the car and I don't reckon 3" will be enough.

[stealth]

lmfao! 3" all the way matey, Blitz is super loud but is NOT a true 3" system, the Blitz tappers in to 2.5" at the connecting end of the pipes.

[Scutch]

PMSL Ben :lol:

Stealth, Scoobyworld website offers a Blitz 2.5" system and a 3" system. So both are 2.5" connections?

Is the 3" system a LOT louder than a 2.5" system? My afterburner is pretty loud, especially with the Magnex de-silencer through pipe, but not overly.

[Dave]

The Blitz Nur Spec R is a 3" system but tappers off at the centre section so it can connect to the OE downpipe.
I "expect" the 2.5" system is just a Blitz back box.

[marky mark]

If you are not planning on upgrading from the VF28 Scutch, just keep your current exhaust.

The 2 1/2" bottle neck is not going to be restrictive until you get to the kind of BHP that a VF28 is not capable off.

BUT, if you have further plans then get a 3" downpipe and centre.

[Scutch]

I dont have any further plans at present Mark, just thought a 3" system would give impressive gains over a 2.5" system. Keeping the original turbo for the time being.
Got quoted around 3 hours for FMIC fitting by a local specialist, and around 4 hours for clutch. He has an Evo 6 and has worked on these aftermarket parts before. Mark, the FMIC I've bought is a pace jobbie I take it? He said some of them are a great fit, but others a pain in the ar$e. Hopefully this one is a great fit :)

Also, what is the best downpipe?

The Afterburner de-cat downpipe @ £175 or the Ninja downpipe with fast flow cat @ £300?

[Dave]

Could always get a scoobysport downpipe. The pipe I have is 3" and tappers off to 2.5".

[Scutch]

Could always get a scoobysport downpipe. The pipe I have is 3" and tappers off to 2.5".

The plan is to stick with the Afterburner Vortex 2.5" and Magnex 2.5" and get either the Scoobyworld Ninja downpipe with sports cat or the de-cat Afterburner downpipe. Dont know which one though :?

[Money]

I have a 2.5" Afterburner Vortex and Magnex centre section at the moment, and was considering a 2.5" or 3" Blitz NUR Spec. Will it make that much of a different to power output and noise?

Danke once again ;)

Been tested on rollers and 2.5 and 3" was jack sh*t difference. Same car just exhausts swapped over.

Think it only matters when doing say 500bhp and then you notice the odd 1-2 bhp

[benm]

I have a 2.5" Afterburner Vortex and Magnex centre section at the moment, and was considering a 2.5" or 3" Blitz NUR Spec. Will it make that much of a different to power output and noise?

Danke once again ;)

Been tested on rollers and 2.5 and 3" was jack sh*t difference. Same car just exhausts swapped over.

Think it only matters when doing say 500bhp and then you notice the odd 1-2 bhp

**Mappers fall over** **Oh my god, you've ruined an industry**

Bad boy Frank :P :lol:

[Scutch]

lol Ben. Thanks for that info Frank. Good stuff :)

[benm]

Looks like some "mappers" justification of the money may be required sometime....

So far, exhausts don't make sh!te difference and cluthes let go if mods go beyond the capabilities of the standard clutch.......

Surely this should be advised, as they have experience to know, before their mapping service starts. Rather than half way through when they can "abort" and make you pay again.

:?

Just a thought guys :wink:

[marky mark]

I would ask Pickle how much he gained from a 2 1/2" to a 3" Frank :lol:

Ben - More torque (maybe 20% more from a decat and remap) will give your clutch a 20% harder time.

If its not new or in spanking condition, its easy to see why they fail - often during a mapping session.

[Money]

Lol at benm.

Would be interested in Pickles results and if anything else was done. Info i had was from a dyno, and now tuner doesnt really bother with 3" unless customer really wants to spend extra money then he is happy to take.

I remember back in the day when everyone was determined on the 3" and Andy F wasnt convinced. Had a 2.5" on and still smashed up the 1/4 miles :o) This was before he went for stupid power to

[PICKLE]

Hi Frank, this is not a completely 'bible' judge of gain etc. but..........

Story is as this: Car was in a quite serious spec (pretty much as it stands now)
Visited WRC Technologies in Silverstone as part of a RR day. The exhaust system was then :

Gruppe-S Headers
Scoobysport (original) 3" tapering to 2.5" Decat Downpipe
HKS 3" Hiper system

Car made something like 349bhp on that day. 1.23bar peak (Dyno Dynamics Rollers)

Then later without ANY changes I went to Power Engineering

Car made 355bhp that day. 1.3ish bar peak IIRC (Sun/MAHA Rollers I believe??)

I then bought a 2nd hand Haywood and Scott 3" all the way through De-cat Downpipe. This then gave the car a full 3" system from the turbo back. NO mapping changes were done.

Went to G-Force with the P1 guys, and the car made 396bhp. 1.45bar Peak (Dyno Dynamics Rollers)

So if you compare the results from WRC Tech and G-Force (same roller type) then even though the peak boost figures were different, the car somehow gained 45+bhp :mrgreen:

I don't expect that was a result of the change to a full on 3" system for a minute, BUT I did feel that this was restrictive to the car somewhat, so thats why it was swapped out. The results then showed the car performed better on the rollers as I suspected. Alot is down to the operator of the RR etc, and I fully believe the car wasn't run correctly @ WRC Tech, as the peak boost was way down on what its mapped for (1.5bar peak)

The only way to tell for sure it to run the car on the same rollers on the same day etc, but with just swapping out the 2x Systems to compare!!.

I would (on the back of my personal experience) recommend changing to a full 3" system if aiming for 350+bhp on a GC8 with a standard location turbo.

[Scutch]

45bhp difference?! Holy smoke!!

So do you recommend just the 3" into 2.5" downpipe for mine Pickle? I'm using standard turbo with FMIC and Induction kit, and I have a 2.5" back and centre at the moment.

[marky mark]

Read it a bit more carefully Scutch, 0.2 bar difference is going to be worth 25 BHP of that figure - The rest has either come from calibration diferences between Dyno's or the exhaust. I suspect its both.

[Scutch]

Sod it, I'm sticking with 2.5"

It'll make a hell of a difference no matter what :D

[Money]

Interesting stuff Pickle.

Shame it wasnt done on same day as would have been interesting. WOuld have been a bit more interesting if done on same rollers.

Stories of certain people going to rollers making 350bhp and then going to Well Lane (on same day with nothing else done) making 380-390bhp. LMFAO

Shows how different rollers were.

The tuner that I spoke to, did on same day and swapped over exhausts straight away and no tinkering done.

It is odd 1.23 bar at 2.5" at WRC and then made 1.45 at 3" at G Force

[burble]

Only thing i can add to this being: after my engine rebuild [spec for 400+ BHP] Full steel bottom end etc, the car was again mapped [Pat Hurborn] on Dyno Dynamics rollers, points he made at the time were; to increase Zorst to 3" straight through, i was then running H&S Down & Centre with Vortex Back Box this also reduced from 3" to 2 1/2" at the start of the centre, interestingly the other point was to get rid of the two bends just before the back box, i point out this was only if i intended on going above 350 BHP. it now transpires after talking to Richard Bulmer that increasing to 3" will in fact lose some torque although will gain BHP ?? Wonder if that's why WRC cars seem to run 2 1/2" straight through??? Confusing or what!!