Exhaust. How short is too short?

[v8s_are_slow]

My buddy has a 1g Talon that's fwd I'm trying to buy. He has no exhaust on it other than an O2 housing and running it with the stock turbo. He's complaining of boost creep and I'm sure that no exhaust isn't helpng. I have an ATR catback I'd like to throw on the car but it's for awd. Not exactly sure why the downpipes are different between the awd and fwd but I'd like to buy the awd downpipe until the conversion is done and just run it open downpipe for the time being until I get get the catback installed with the rear diff on the car. But if the awd downpipe won't fit on an fwd car, I'd just run a fabbed up downpipe for the time being. Or a very cheap/stock downpipe anyway.

If I have to fab up a pipe, how short is too short? Anything that could go wrong from having it too short aside from boost creep? Anyone know why an awd downpipe won't fit on a fwd car? Thanks.

 

[1gcrazy]

My buddy has a 1g Talon that's fwd I'm trying to buy. He has no exhaust on it other than an O2 housing and running it with the stock turbo. He's complaining of boost creep and I'm sure that no exhaust isn't helpng. I have an ATR catback I'd like to throw on the car but it's for awd. Not exactly sure why the downpipes are different between the awd and fwd but I'd like to buy the awd downpipe until the conversion is done and just run it open downpipe for the time being until I get get the catback installed with the rear diff on the car. But if the awd downpipe won't fit on an fwd car, I'd just run a fabbed up downpipe for the time being. Or a very cheap/stock downpipe anyway.

If I have to fab up a pipe, how short is too short? Anything that could go wrong from having it too short aside from boost creep? Anyone know why an awd downpipe won't fit on a fwd car? Thanks.

An awd catback will fit on a FWD but not the other way around.

 

[spoonman]

My friend is running an exhaust with a stock down pipe and 2.5 inch exhaust tubing with no muffler or a converter that ends in front of the rear left tire. His car is a 91 fwd, he has no boost creep or back pressure problems, but it is just really loud.

 

[v8s_are_slow]

An awd catback will fit on a FWD but not the other way around.

Sweet, so I could get an awd downpipe as well and throw it on a fwd??? That's the real answer I need to know.

 

[thekellbeast]

What sort of O2 housing is he using? Stock 1g? If he really doesn't want to run an exhaust system, he should port the hell out his turbo (wastegate inlet) and O2 housing - or get a tubular housing. As long as it's ported correctly, there really shouldn't be a problem with creep. I suppose the last resort would be to get a 38mm flapper.

BTW, is he running the 14b? And is he running no exhaust system because he thinks he'll get better performance, or because he's too cheap to get one? I do agree that he should get an exhaust system, but maybe for different reasons than some people.

1. Turbos are most efficient when they have a large pressure differential across the turbine. What this means, is the most efficient exhaust manifold possible, and the least restrictive exhaust system possible. However, on a turbo as small as the 14b, it's really a point of diminishing returns. You're not close to enough exhaust flow to make a 2.5" system restrictive, and maxing out a 3" drainpipe with a 14b is just a joke. On the flipside of this - don't put words in my mouth, especially not the B-word. I didn't say a damn thing about backpressure, because that's a hillbilly myth.

2. Imports have a bad enough name as it is with fartcannon exhausts, and running around all the time with an exhaust 'system' that dumps at the turbo, pointed straight at the ground, is not going to help the image at all.

3. Short exhaust systems are cool as shit, on track cars that dump right out in front of the driver's side wheel. Especially on cars with full T4 setups. NOT 14B's.

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[v8s_are_slow]

He's running a tubular O2 housing with an external dump at the O2 housing. Sure porting the wastegate of course would help though but that just seems a lil too short to me. Would almost be like running a V8 with no headers or anything of the head. I dunno.

Yes he's running the 14b. Not sure why he has no exhaust on it but I plan on putting one on there. Just wanna make sure an awd downpipe will work on a fwd though.

I love the look of a car that has the exhaust dumping in front of the tire but not sure if cops would pull me or not. I'm in Florida and they're pretty lax on most stuff but dunno about that though.

 

[fwdeclipse]

I am not sure on a 1g but I know on a 2g the awd and fwd dp are very different.

 

[absolute_DSM]

I didn't say a damn thing about backpressure, because that's a hillbilly myth.

Not a myth, just not important to turbo vehicles.

 

[v8s_are_slow]

I am not sure on a 1g but I know on a 2g the awd and fwd dp are very different.

That's what I have to know for sure of...on a 1g though. Surely someone knows this answer. If they're different, why?

 

[Mr Peepers]

Not a myth, just not important to turbo vehicles.

While it's not a myth, it's "benefits" are. It is confused with velocity, which often has the side effect of backpressure. You are right though, velocity post turbine is not as important on turbo vehicles since the effects of scavenging are nearly non existent after the turbine housing.


Too short for a daily driver would be dumping the exhaust gases in the engine bay or under the car. First off it's incredibly loud(but sounds like a jet ) for everyday driving and you'll have all that exhaust in your engine bay and/or getting into the cabin. At least get a DP on there and the rest ASAP.

 

[90laserRSfwd]

An awd catback will fit on a FWD but not the other way around.

Since when?

 

[absolute_DSM]

While it's not a myth, it's "benefits" are. It is confused with velocity, which often has the side effect of backpressure. You are right though, velocity post turbine is not as important on turbo vehicles since the effects of scavenging are nearly non existent after the turbine housing.

Exactly

 

[v8s_are_slow]

Since when?

Well, someone post pictures or explain why it won't fit or what's different, etc. Downpipe AND catback.

 

[thekellbeast]

There's probably more room on a FWD since it doesn't have a transfer case or driveshaft, and the exhaust takes turns and stuff. I'm betting that the AWD downpipe is straight, like it is on my 2g AWD.

 

[Mr Peepers]

The downpipe may connect to the catback in a different spot comparing fwd to awd, but I don't see any reason why an AWD DP alone won't fit.

 

[fallenauthority]

And AWD exhaust will fit a FWD with no problems. The reason you can fit an AWD exhaust on a FWD but not a FWD exhaust on an AWD is because the AWD exhaust is built to avoid all the AWD components such as x-fer, driveshaft and rear diff. The AWD exhaust does this by routing along the bottom of the car outside of the driveshaft tunnel. A FWD exhaust routes right through the "driveshaft tunnel" in the middle of the car. An awd exhaust will fit a fwd car it will just look stupid from underneath the car because you will have this exhaust routing beside the empty driveshaft tunnel under the car instead of inside it.

And to the OP, you say that you want to put the downpipe on the car and run it open DP until the "conversion" is complete and you can route the catback around the diff. Are you planning an awd swap for this 1g? If so, dont even try it, wait it out for an awd car or shell and just use that and swap a motor into it or whatever. An awd swap on a 2g is involved enough, on a 1g it is almost impossible and it is definitely not cost effective at all.

 

[dsmsucks]

Since when?

Yes I would love to see an awd exhaust on a fwd

 

[DarthBulk]

I didn't think an AWD exhaust would fit a FWD car right at the rear axle, because of that side to side cross bar that the FWD exhaust has to jump over. Won't the AWD exhaust run right into that bar? The FWD exhaust has a nice little hump bent into it, to jump over that bar.

 

[fallenauthority]

I didn't think an AWD exhaust would fit a FWD car right at the rear axle, because of that side to side cross bar that the FWD exhaust has to jump over. Won't the AWD exhaust run right into that bar? The FWD exhaust has a nice little hump bent into it, to jump over that bar.

Most AWD 3" exhausts are meant to route under the rear axles, which line up where that little bar on a FWD is. The AWD exhaust will go right under that bar. at least it should.

 

[DarthBulk]

I have never seen it done, but I would think that exhaust would almost be scraping the ground if it routed under that bar. Does it also route under the rear "axle" too? I will have to go check my car again, to see if it would work, but it just seems like going under that bar, and then under the axle, and leaving room for suspension travel, would leave the exhaust very close to the ground.

 

[1gcrazy]

Most AWD 3" exhausts are meant to route under the rear axles, which line up where that little bar on a FWD is. The AWD exhaust will go right under that bar. at least it should.

He's right. In theory it should work.

 

[DarthBulk]

The problem I see with it is when the car is jacked up, or the suspension is at the limit of its extension. There are actually two bars at the back of a FWD. The first is the cross bar that is connected to a drop-down bracket at the passenger side frame at the wheel well, and the control arm on the drivers side. The bar is fixed on the passenger side, but moves up and down with suspension travel at the driver's side. The second bar is the axle that connects straight across between the two wheel hubs in the back. I seriously don't see how you could route an exhaust pipe under that second bar. If you could route it low enough that it doesn't contact that bar when the suspension is at its maximum extension, your exhaust would be laying on the road. That is why the FWD exhaust jumps over the top of it.