External Gate. To Plumb, Or Not To Plumb

[Wheezy]

HRMMMMM Interesting views....Im in the same boat. Ext. gate to atmosphere, but what to run from the turbo back, Im probably not going to use a cat, so either 3.5" from turbo back or 3" turbo to "where the cat should be" then 3.5" "cat back" so to say.......Opnions?

This is for 260 (street) and possiably 300rwkw later on.....

Remember Roy Atmo Gate = Love

[Guilt-Toy]

I want to make my car legal and pass the epa tests etc. So because the flex pipe they used on my external gate plumb back is leaking i might remove it and run a whole exaust to the back of the car and use a small cat so the epa cant whinge about it.

Not saying it wont make the power, i did

The 3" system i had on my car, definately was a problem as the gate had to stay external

Then, my exhaust goes up and over the diff, where most R33's seem to be pretty straight and go under it.

Seen a couple of cars go from 3" to 3.5" and pickup some excellent results.

Nothing beats a flowing exhaust.

[saliya]

I have been warned though that this year i may be getting pinged at track days as the EPA are enforcing db requirements at the track. Now i dont care about losing the cool noise at WOT, my concern is will the increased gas flow in the exhaust cause back pressure problems...loss of power/boost problems etc?

Anyone had a plumbed back vs atmo experience on the same car, setup and tune? I know of two cars that lost power when they were plumbed back. Is that the norm?

I am running a high flow cat and HKS Hyper exhaust, which has two mufflers. Will it handle all those by-passed gases?

Hey,

I have only anecdotal evidence from a friend (seat-of-pants) that says yes, performance will drop.

When you plumb it back you're attempting to stuff extra gas through the system - more backpressure, less performance.

So the same car, same tune is almost guaranteed to lose performance from changing VTA to plumb-back and nothing else.

"How much" performance drop really depends on how much your exhaust 'can' flow vs how much it 'is' flowing right

now, and how much gas is chucked out the gate that needs to be accounted for. I'm not familiar with that HKS exhaust

nor the internal design of its mufflers, but if it's 3.5" or bigger I'd say it will probably be OK.

You could always knock something up and see If there's a big difference you'll probably hate it and take it back off;

but then at least you can take it to the track ready for fitting if you do get pinged...

Regards,

Saliya

[someonestolecc]

Just something about extra exhaust setups... I'd be wary of the weight, an extra cat and a muffler with some pipe sound like a few kgs.

[sh@un]

When you plumb it back you're attempting to stuff extra gas through the system - more backpressure, less performance.

'zackly- you can't beat physics

even the Ferrari F40 runs a screamer from factory!

turbo cars will always make the most power with as little back pressure after the turbine as possible....shame though that the RTA/EPA aren't concerned with your rwkW figure

[T04GTR]

I want to make my car legal and pass the epa tests etc. So because the flex pipe they used on my external gate plumb back is leaking i might remove it and run a whole exaust to the back of the car and use a small cat so the epa cant whinge about it.

i used a slip joint. no clamps and it doesnt leak and is nice and compact

[T04GTR]

hrmm. with fulll noise i have 1psi pressure at the cat.

[BHDave]

Mine's plumbed in. 3 inch off turbo to cat. 2 inch off 38mm gate to cat. 5 inch metal cat. 3.5 inch cat back. good for 288rwkw so far.

I can't give a true back to back plumbed vs atmo vented as i had the metal cat installed at the same time i had it all plumbed up. I also had it all done pre tune and pre cams when the car was making a touch over 200rwkw on 1 bar.

[Ronin 09]

harden the fcuk up, Roy.

lol

keep the screamer

[GeeTR]

harden the fcuk up, Roy.

lol

keep the screamer

HAHA agreed >>

[Busky2k]

If you want to be a bit more scientific about it, plumb a pressure sensor where the O2 sensor is temporarily and check the backpressure on full tilt. I guess if its more than a few psi then there may be some perfomance loss.

[Roy]

If you want to be a bit more scientific about it, plumb a pressure sensor where the O2 sensor is temporarily and check the backpressure on full tilt. I guess if its more than a few psi then there may be some perfomance loss.

I have already checked the exhaust pressure when i changed from 10cm housing to 8cm housing. Wasnt overly different which told me that the 8cm is right and the 10cm was jsut too big for the flow of the lil RB20.

I dont want to spend the money on labour por waste my own weekend trying this if i can reasonably identify it being a problem. I have a feeling i will need to go to a bigger exhaust which sux cause odds are it will be louder then what i currently have, only the gate will be silenced. At the moment off boost my car is nice and quiet .

Its a race track for gods sake...if residents dont like the noise dont farking move there,

[Busky2k]

I have already checked the exhaust pressure when i changed from 10cm housing to 8cm housing. Wasnt overly different which told me that the 8cm is right and the 10cm was jsut too big for the flow of the lil RB20.

If you checked the exhaust backpressure post turbo ie dump pipe, the turbine housing won't affect it much........unless you are saying you measured the backpressure in the exhaust manifold itself?

[Roy]

Well the wheel has turned and i got done for noise. So need to do it. My dump pipe is pretty shitty and have never been happy with it.

So im thinking i may do a 4" dump pipe and tee the wastegate in just before i reduce down to the cat and HKS Hyper exhaust.

Do you think runn the larger diam dump will help with dropping gas velocity so a branched joint for the wastegate gasses wont hurt power as much? Can anyone confirm where the HKS Hyper exhaust sits with regards to performance and noise?

Is it a performance exhaust, street eshaust etc? Would it be the same diam with same mufflers as the Hyper exhaust on the GTR? Can i run a GTR exhaust on an GTSt?

[Ronin 09]

GTR exhausts bolt up fine, old son

[sinistaGTR]

I got mine as a screamer wouldnt have it any other way, nothin beats the sound of an external gate goin nuts

[tridentt150v]

Do you think runn the larger diam dump will help with dropping gas velocity so a branched joint for the wastegate gasses wont hurt power as much? Can anyone confirm where the HKS Hyper exhaust sits with regards to performance and noise?

Is it a performance exhaust, street eshaust etc? Would it be the same diam with same mufflers as the Hyper exhaust on the GTR? Can i run a GTR exhaust on an GTSt?

I've got a HKS Hyper but with a single 5" cannon tip. Mine has an adaptor that you can put in the cannon tip to 'choke' it. I've never used it, but it would be good to go if I was ever done for noise.

HKS Hyper exhausts I thought were 90mm outside dia. so yeah, 80-85mm ID. Cos it's a straight through pipe from the cat, and given the diameter etc I'd have thought it was a pretty good performance pipe, I've never had any issues yet but I was only running with 240, now I'm aiming for sub 300 and I guess I'll be testing the bounds [3076, hks cast low mount, hks std wg, custom dump front plump back and custom s/s intake eventually].

BTW the exhaust has a good deep note, but is pretty quite really, I don't get headaches on long trips .

[MattSR]

Well the wheel has turned and i got done for noise. So need to do it.

NNNOOOOO!!!!!!!!

Keep teh atmo WG Roy! U know u want to!

[2rismo]

Rip the line off the gate so it doesn't open

[Roy]

I got mine as a screamer wouldnt have it any other way, nothin beats the sound of an external gate goin nuts

Its not the point. Keep it off boost and there is no problem driving it on the street. But when at the track you want to be able to give it some stick without fear of being kicked off the race track. Thats is the real concern, owning a club car that is fun on te race track, that you pay lots of money maintaning and entering in events only to be kicked off the track