3800 How loud with no cat back

[98 TGP TOY]

Hey guys, I've come up with a new theory on my kr. I tend to see about 12 psi with my 3.4 pulley and headers. So I am thinking I could have some stacking going on because I still have the stock cat-back. Seem unreasonable? Well I am thinking about dropping the cat-back and going out for a couple of scans to see what happens. Exactly how loud is this going to be, and will this set off some false knock? Or is the catback far enough away from the sensors, that it wont effect it?

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[sweetness]

it will be loud. I don't know about setting of the knock sensors, but it will be loud. You will also notice that you have lost a lot of low end acceleration. Hence the "good" backpressure, if such a thing existed.

BC

 

[1BADGTP]

yeah it will be so loud i took my cat back off after the ubend to see how loud it would be and i did not like it one bit. It pops to much.. it might not be bad if you run pipes out from under the car that way you dont get as much drone.....

 

[imported_Ron Vogel]

You're prolly going to get some false knock. I am really anal about wrapping my exhaust, it really does fight kr; especially the DP. I got 5 KR with my new exhaust, wrapped it and saw 0 kr. Some of that is due to keeping the exhaust gas hot. I wouldn't drop the exhaust, but look into better intake, decarbonizing the motor, spark plug selection, and loose or hitting parts. My heads/cam are stock, and have ported mani's, but normally see 12psi/14psi when cold. You're right in the ballpark, I used to see 10.5 to 11psi with my 3.4.

 

[98 TGP TOY]

Well I built my CAI and it sucks in air that is only like 5-10 above ambient. So I think its pretty good. I'll have to try some more top end cleaner. Did it last fall, but maybe two bottles would work better. Also, I have played with three different ranges of plugs. Race gas kills the kr so I dont think I need to worry about it being false. I figured it would cause false knock. I will have to try something else then..

 

[imported_Ron Vogel]

Ahh, more details...Make sure the CAI has at least 3.5" tube. This is a fueling issue if race gas kills it. A very small change in fueling can go a long way. Keep a plug that is only about a range colder than stock. I'm assuming you do not have a mini-afc. If you don't pick one up; even a 1.0 will help you out here. With the 3.4 my motor was real happy with 103%.

 

[98 TGP TOY]

Well I have the 3.5" PVC from lowes. I think that may be OD though. Woud you recommend getting a 4 inch and then a reducer coupler to attach to the TB? Will those rubber couplers do fine on a hot TB?

 

[imported_Ron Vogel]

Yeah, that's a little small. The pipe thickness is almost 1/4", leaving you a 3" id. The rubber couplers work fine, but don't look all that pretty. Try to get a straight shot of 4-6" before the TB; especially if you aren't running a screen. If you want, I can get 3.5" steel tubing. Just tell me next time you're in town and I'll pick one up. I get them from 15-20 bucks.

 

[98 TGP TOY]

Ok, well Im going to try some metal piping then. I can get some cheap also. I am running a screen, because my 98 gets lonely without it and starts sending ses signals for a lean condition. So I put it back in. Thanx for the advice. So would you recommend 3.5 inch tubing. Or what would be optimum for a stock TB.

 

[imported_Ron Vogel]

I've tried a ton of different CAI/FWI's, my car has alway's been happiest with 3.5". If you are in the area, go to Boyce industries in Franklin Park. Talk to Tom 708-345-0455. He can madrel bend up to 4" if you want it. They keep 30-45-90 bends in stock, but he can do anything you want also. Sometimes they have scraps of bends he will sell for 5-10 bucks cash. The only other place I go for the mandrel bent tube is McMaster-carr.

 

[98 TGP TOY]

Ok, thanx. Ill have to see what I can do next week.

 

[Mikes1998GTP]

If I go and have the U-Bend fix replaced and still have my stock mufflers and tips, will i notice much of a difference with that fix?

ThePizzaAvenger suggested having his friend install some nice Flowmaster mufflers, fix the U-Bend and add dual tips for just under $300, so now I'm unsure of what to do...

 

[98 TGP TOY]

There is probably a 3-5 hp increase when getting the ubend replaced. The flowmasters would be for a better sound. You wont gain hp off replacing those on a stock gtp. If you want the best bang for the buck then get a 3"dp/hi flow cat/ ubend replaced setup. Here is a recent talk about the same subject

http://www.ilgpc.com/forum2/index.php?showtopic=2634


Good luck.