2.5 vs 3inch DP

[V8SpankR]

I have a friend that is returning his car back to early stock since he's gonna sell it and wants to trade me straight up for his full 3 inch turbo back for my 2.5in DP and my HKS twin tipped stock appearing exhaust.
My question is should I go with the 3 inch downpipe or stick with my 2.5 inch? I'm planning on running my 18g not much more than 22psi and I want to know how much lag I will gain from the 3 inch DP and is it worth it at the strip?

[ryanman]

Hey dood, lemme know if you go with the 3" or whatever goes on and I'll swap him my complete stock exhaust and some cash for whatever he ends up with if he's wanting to return it to stock.

[v413nc3]

How much lag you will GAIN? This doesn't make much sense to me. The larger the exhaust the FASTER the turbo will spool, and the easier it will control boost creep. You'll benefit from going larger, not the other way around. As you help the exhaust leave faster that means that there is less pressure and the blades spin more freely as more exhaust gas can move over them.

[Van]

Originally posted by v413nc3
The larger the exhaust the FASTER the turbo will spool, and the easier it will control boost creep.

A larger dp will always worsen the likelihood of boost creep.

It will definitely be a worthwhile mod at the strip up top, but for your stated goals there is no real good reason to do it. Is his exhaust SS?
Lots of 11 sec dsm's running 2.5 inch exhausts, especially 2.5" dp's and 3" cat-backs.

My 2.5" dp has served it's purpose well, mated to the 3" catback. Swap him the catback part, hehe. ;)

[-EpicEVO-]

I would say go with the entire 3 " turbo back..

It's more power..

I have a 2.5 right now, i am planning on upgrading after i run a few times this season..

MARK

[v413nc3]

I agree Vern to a point. With a 3" DP you can control boost creep better after you've taken the proper steps with wastegate control. If you have a nice sizeable wastegate a 3" DP helps control boost creep if you recirc it back into the exhaust track.

[V8SpankR]

I thought a bigger DP would increase lag a bit sincer it is flowing so well. It is a full SS system my friend has but I may just keep the 2.5inch DP and swap out the catback as I don't need boost creep issues if they are likely to pop up.

[V8SpankR]

Well,I'm going to do the swap of the SS turbo back for my 6 year old HKS 2 3/8 system w/2.5 DP tomorrow (I can't believe I'm getting this deal) and see if I get any gains at 17psi since this week was hectic and I never got a chance to do the 550s and tune it.

I'm running on Sunday and i didn't want any tuning issues with it being bracket racing,hopefully I can improve on my 13.38 with the same 17psi and some better tuning of the stock injectors.

[test]

Yeah you'll like that. In fact just yesterday I did a turbo back 3" from Extreme Motorsports and I'm running a Frankenstein Junior 19C (ported) which is like a 18G Hybrid. I also have a Ported O2 housing and I'm running about 14 psi around town and I have no problems with boost creep. I would definitley recomend porting your turbo and your O2 housing. Money well spent.

[Hal]

Just as a data point, Buschur now sells a 3.5" system :)

Hal

[v413nc3]

They have for a while for the 1G are they now carrying it for the 2G?

[XakEp]

3 inch is so worth it.

Blooooog

[V8SpankR]

I did the swap just before the Street Machine showdown and ran 17psi with no problems and the turbo does seem to spool a bit quicker with the full 3inch and better than I thought.

I did have a little knock problem but by eliminations the car ran too good and with a dial in of 13.59 I ran a 13.51@92mph,that was getting off the throttle at the 1000' mark. I compared my other numbers to last years 13.38 run and if I could have stayed in it I was heading for a possible 13.2 with just the exhaust change.

We'll never know tho' as the next time at the strip I'll have the 550s in and some more boost and I'll be trying out the MAF bypass on the Dejon Intake.

[v413nc3]

I'm just curious where you heard that a larger exhaust would make it spool slower... that's actually the first I've heard that.

[V8SpankR]

Originally posted by v413nc3
I'm just curious where you heard that a larger exhaust would make it spool slower... that's actually the first I've heard that.

I guess I meant that it would have a little more lag than in the higher gears with it flowing so well. It does seem at 40mph in 4th it is a bit more laggier and sometimes needs a 3rd gear downshift where with the smaller DP it got going a little better.

[v413nc3]

Ooooh, yeah a larger DP tends to not scaveng as well I suppose...