Need Some Advice

[R31Nismoid]

You will never get 400rwkws with a GT3582 on a stock Rb25det on 98 fuel. maybe E85 with 500Hp Shot Nos if engine doesn't fly in pieces.

Edit: Never mind. Its probably Nismoid's typo.

ye, was meant to be 300rwkw - totally missed it

i've altered it

[l0WRB]

so what should i do lol

adjustable cam gear?

[GTScotT]

change the cat, you wouldnt believe the shit ive seen mates go thru trying to tune well built cars with a cheap cat that had a 3mm smaller ID than the rest of the exhaust.... 2-400 bucks on a proper cat and birth to the monster within

[l0WRB]

you really think my gutted stock cat would be holding it back from flowing as well?

[TiTAN]

stock cat is what 2.5" tops? yes it will be a restriction. drop the cat back on the dyno do a run.

[R31Nismoid]

you really think my gutted stock cat would be holding it back from flowing as well?

drop the exhaust from the dump pipe.

I think you'll be surprised @ the outcome.

[l0WRB]

Im sure the neighbours wouldnt mind if i went around the block with just a dumpipe on hahahaha

[R31Nismoid]

on the dyno i mean.

[l0WRB]

yeah i know nismoid

im goin to make a video today inside the car showing revs + boost gauge

[GTScotT]

drop the exhaust before the cat and go for a drive, other than noise i dont see it being a problem.. not like theres a cat in there anyway lol

[Adriano]

Unitl it leans out and pops the motor, do it on the dyno

[l0WRB]

its running safe enough afr's it wont lean out lol

[GTScotT]

what makes you think it will lean out by unbolting the exhaust from before the cat? id love to know

[Mr. Untouchable]

the stock cat is 2.5".

and remember, the smallest point in the exhaust basically determines the size of the exhaust. Doesn't matter if you have a 4" dump and cat back, if you have a factory gutted 2.5" cat, that is the size of the exhaust.

You can un-bolt the cat and bore/grind the stock flanges out to 3" (there is enough meat there) and put a straight through 3" pipe in the stock flanges. Then weld the original cat body back on for a stock look (a good idea if transport/police are hard in your state).

the cat may be gutted but its still necked down = turbulance and poor flow.

Edited February 9, 2010 by Mr. Untouchable

[l0WRB]

hmm last i checked the stock cat flanges are 3" cause it bolts up to my 3" dump and cat back exhaust.. but it could be an option..

would running my external gate to atmosphere help at all?

i made a video going from 20-160 but my net is capped so i cant upload its way 2 slow

Edited February 9, 2010 by l0WRB

[Mr. Untouchable]

the flanges have the same shape size etc as aftermarket 3" gear but the actual inner diameter is like 63mm for memory which is basically 2.5" bore the suckers out to 3" and put a piece of 3" pipe in there or buy a pre-made decat.

and dumping the gate to atmo wouldn't hurt. less gasses trying to escape out the exhaust pipe.

mate id be trying the cat, maybe a exhaust cam gear.

after that, garrett .82 rear and a nice highmount manifold.

Edited February 9, 2010 by Mr. Untouchable

[GTScotT]

venting the gate to atmo wont help, but try unbolting from before the cat... it really could be the answer.

as stated they have a 2.5" internal diameter, the car i mentioned earlier was only out by a few mm not half an inch lol

[Mr. Untouchable]

venting the gate to atmo wont help, but try unbolting from before the cat... it really could be the answer.

depends where the gate is plumbed back in. If it plumbs back into the dump not far from the turbo I disagree.

if it plumbs back in further down the exhaust near the cat I cant see it being a huge restriction but if you merge it back say 30cm from the turbo I reckon it will upset the flow a bit. Not trying to say its the main problem but all these little things add up.

the cat is a cheap fix and there IS gains to be had there.

Edited February 9, 2010 by Mr. Untouchable

[Adriano]

what makes you think it will lean out by unbolting the exhaust from before the cat? id love to know

High backpressure increases reversion, which decreases fuel requirement for a certain load, reduce the backpressure and the fuelling requirement increases.

With an AFM car this increased airflow is compensated, wheras with a map sensored car it isnt.

[GTScotT]

in theory, yes. but we arent talking half the map worth of load dropping off, if the tune is good it would be lucky to lean out anywhere near whats called dangerous.

plus its only for a squirt, ud want to re dyno it after u fix the problem anyhow.