[KERR]

A doctor here in just ask me what kind of flow and hp diff. there is in a off road down pipe with a car and a off road Down pipe with out a cat?

I told him i have no idea.

Any of you know?

 

[Ming]

first, are you asking the stock twin's DP or after maket's turbo's DP. anyway, i donot think there is any differences on hp, there is something different flow contol, i think. because straight pipe(DP) without cat, the turbo breaths directly to the exhaust.

but that's a very good, i will look forward the correct answer to this.

 

[Ming]

first, are you asking the stock twin's DP or after maket's turbo's DP. anyway, i donot think there is any differences on hp, there is something different flow contol, i think. because straight pipe(DP) without cat, the turbo breaths directly to the exhaust.

but that's a very good answer, i will look forward the correct answer to this.

 

[BLITZSUPRA]

I think even hi-flo cats have been proven to rob about 10-15 HP. Maybe the newest Random Technology hi-flo is less restrictive.

 

[MustangGT]

A doctor here in just ask me what kind of flow and hp diff. there is in a off road down pipe with a car and a off road Down pipe with out a cat?

I told him i have no idea.

Any of you know?

An off-road downpipe has no catalytic converter. There's no such thing as an off-road DP with a cat because if it had a cat it wouldn't be for off-road purposes. A catalytic converter converts carbon monoxide and hydrocarbons to carbon dioxide using a catalyst plane inside the cat's housing. It adds oxygen to the pollutants so that they will be more receptive to ultraviolet rays so that they will be broken down into O3 (ozone). Most states require a cat. In states that require one it is illegal to drive around without one, hence the name "off road" pipes because they are not supposed to be on a car on the street. You can get high flowing catalytic converters that flow better then stock but still are legal for the street and will pass emissions inspection but I am unsure what exactly is available for the Supra. I'm also unaware of the HP differences between a cat-equipped and an off-road DP for the Supra. Different cars respond in different ways. I know the '99+ Mustang GTs are really choked by the pipes. They have 6 cats for the factory and an off road H-pipe (they are called H-pipes or X-pipes for the Mustangs) with a cat back exhaust can equal about 8 or so HP on those cars. Most cars will see less andbecause they are not as restricted to begin with. Off road pipes can cause you to lose some power down low on a stock engine because you decrease the effective backpreasure. I hope this helps..

 

[Dj*BaM|BaM]

Well i was hoping would've said the answer already so I'l the honors I guess. With jsut the DP and no cats, you will gain approximately 30 hp. Iono if it's at the crack of wheels, but hell it's enough to even make a grown man cry...:tongue:

 

[SpdRcr0]

Blitz is coming out with a DP .. and there NUR spec doesnt seem to have a cat built except for a silencer... do you guys think that silener would fool cops??

 

[BLKMGK]

Confused...

I'm used to cars having a downpipe, midpipe, and then catback to the muffler. Those setups usually hav a precat in the downpipe, then a main cat in the midpipe, and then straight pipe back to the muffler. This is how the RX7 and others I've looked at function.

Stock, how many cats does a Supra have? I thought 2. If so, can you simply remove the precat with a downpipe and run a highflow cat at the midpipe position? I've looked on MKIV.com and their pics of the exaust seem to jive with what I've seen on other cars but this thread makes it sound as if replacing the downpipe replaces ALL of the cats, yes? If there really are two cats on the Supra I'd remove the precat in the downpipe and put a highflow in the middle if roadside inspection is a concern.

My RX7 has a pile of bolt-ons and with just a midpipe cat passed a rolling road emissions test with flying colors - no AIR hose connected to the cat either! I almost passed out when I saw the numbers they were so low. Anyone who looks under the car see the midpipe cat and it blows clean so no worries, flows well too. The exhaust tone completely changed with the new midpipe and the way it crackles occasionally it may even be blowing flame

Do the Supra have trouble maintaining boost without spiking when the exhaust is freed from cats and replaced with better pipe? RX7 have trouble with this but I've not noticed any comments about this problem with the Supra. Is it not an issue?