3800 Custom Downpipe Q's

[jk99gtp]

Hey,

I want to get a downpipe sometime in the next few weeks. I'll probably hit Jim's new exhaust shop (Since he did my U-bend delete awhile back and he's close to me ), but I have a few questions before I go ahead with it.

1) What size you guys think would be suitable for me, 2.5 or 3"? Mods are 3.4" pulley, DHP, Thrasher CAI, 180 thermo and U-bend delete..

2) Would Jim be able to make me a custom downpipe w/cat? If not, how does the downpipe w/o cat go well with the Emissions Team? Getting a downpipe would pretty much get rid of my U-bend correct?

3) I'd like to get Ported Manifolds in the future (Cause I'd like to drop to a 3.25" pulley in a year or two). Would I be able to re-use my downpipe? Or would I hafta purchase a new one when I eventually purchase the manifolds...

Thanks for your responses, hope everyone had a Merry X-mas

Joel
'99 GTP

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[BumpinGTP]

1)3 inch
2)not a clue
3)you would keep the same d/p i believe

 

[dole21]

Originally posted by BumpinGTP@Dec 25 2003, 11:18 PM
1)3 inch
2)not a clue
3)you would keep the same d/p i believe

agreed.

on #3, Jim, used the stock flange I BELIEVE, and cut it off and welded it to my new downpipe, again,

I haven't looked under the car in forever and this may not actually be the case. But if he did, your rear manifold would bolt right back up to it.


Someone else here will either confirm or correct me on this...

 

[mybluegtp]

#2= Jim will not touch the cat at all, as for emissions they will be doing OBDII scanning now for 96 and up if you dont have an SES code you will pass. But they will scan you pcm for any code that has to do with emissions.

as for #1,3 I agree with everyone who posted.

 

[iliveonnitro]

What if you delete the SES warning code that goes off with removing the cat or any emissions things?

 

[jk99gtp]

Thanks all for the replies,

Obviously my biggest worry when getting this downpipe w/o a cat is failing emissions. I do know that they just plug into your PCM (At least for OBDII) to check for SES codes (Just recently took the car in about a month ago) and am not really worried about that. What I am worried about tho is when they look under your car with that mirror, not sure what they are looking for with that...

If I do go with the custom downpipe , what would work better? Get an O2 Sim and have Jim install it? Or just get the code removed from my DHP..

I really would like to do this to take some pressure off the blower, as it currently runs around 11.5 psi of boost. Anyone know how much boost I would lose with the downpipe? This would be with Stock Manifolds and Exhaust (For now at least)...

Thanks!

Joel
'99 GTP

 

[sweetness]

If you had the code deleted then it couldn't throw a light, or register in the PCM, so it would effectively prevent you from getting busted by emissions. I have a "cat" on my exhaust, but after 256 (i believe) key cycles I got the dreaded SES light. had it deleted and no problems since.

BC

 

[jk99gtp]

Guys,

What do you think of the Random Tech downpipe w/cat?

I might want to get the ZZP coated ported manis next week, and I'd like to buy a downpipe with it...

So I'd like to know if a custom or the Random Tech downpipe w/cat would be a better match?

Later,

Joel
'99 GTP

 

[J.E.T.]

You dont need custom work dp with the ZZP ported manifolds. The appropriate R/T downpipe will fit perfect. Remember, the ZZP manifolds are just modified stock pieces.

J.E.T.
'97 Red GTP

 

[imported_Ron Vogel]

Is J/O still got a hookup with the ported manifolds? I've heard the ZZP ported manifolds weren't really worth the money. I'm not saying they are overcharging; I ported my own manifolds and it's a bitch to do them right. I just remember J/O's guy did them for like $50 per side with exchange, and for a modest gain that is a much better value.

 

[Royalgtp]

I have a complete set of stock manifolds(front, rear, crossover) that I might be instrested in selling.

This way, yould be able to get them ported and shipped off to JET HOT to be coated with out much down time.

If your intrested, I might sell them.

 

[rob]

My name is Rob. I was introduced to ILGPC by Alfredo or My blue GTP. You can catch my story at ANYTHING GOES. Title is introduction.

Im currently planning to probably produce my own downpipe and possibly a 3" exhaust system later. The downpipe Im planning will be like no other one on the market alowing tuners to run much pressure with less KR.

Im also working on a propane and water methenol injection kits that will allow all you guys to run 3" pulleys on a daily basis with no KR. Best of all My stuff may not glitter but it will be affordable and gains fully tested before I release anything!

Your questions:
1) I recomend 3" ID tubing. The less restrictive you are CLOSER to the engine reduces backpressure and in a supercharged application-boost stacking.

2)Yes, 3" cats are availible and can be welded in. The are expensive though. Cats are not as restrictive as everyone thinks-as long as their fuctioning properly. Im probably going to set up a dummy cat with an 02 simulater. It will pass EPA tests as long as the dont check for a cat-if the do you have to temp in your stock pipe and retest. You can gut it if you have a simulater.(caspers)or PCM overwrite.

Yes, most of the aftermarket pipes Ive seen eliminate the RESTRICTIVE U-bend. If they dont-well dont buy it.

3)You can run a 3.25 pulley now with a couple mods. I dont recomend ported manifolds for two reasons : If your changing them put on TOGS(unless warrenty)
and your gains will be much better-there worth the money. I recomend that this should be the first mod anyone does and thermo wrap them to reduce heat.
If your car is under warrenty-check before R&Ring your exhaust manifolds.

I ran a 3.25 pulley daily with staight 100 octane,drilled 160 stat,fan relays(the stat and fans work in conjuction)wrapped exhaust manifolds,u-bend removed,hood insulation removed,and borla catback. I STRONGLY advise a knock guage,autotap
to monitor KR. Thats it the fuel is expensive but a must. Once your PCM changes your spark tables you'll have a shit grin. NO OCTANE BOOSTERS(they dont work) OR leaded. 100-106 octane unleaded!
Have fun and run a cool engine. You'll eat mustangs for breakfest.........ROB

 

[sweetness]

With ported manifolds and a DHP you should be able to run a 3.25" pulley with no knock.

BC

 

[Royalgtp]

rear manifolds are a bitch.....do it once, do it right......get togs.....

 

[sweetness]

if you are going to go with ZZP mani's then you should just save up $200 more and get S&S headers. You will need to have the cat worked with (the S&S dp doesn't reach the cat.), but you will be paying about $200 more for everything. A HELL of a lot better than ported mani's.