JKelly

First of all, thanks for the air pump tip SHRKBIT. I used a stainless machine screw (fine thread) to plug the vacuum line. Seems to work fine. So finally, I got to go for an extended spin around town....and the surrounding towns too
For awhile, I couldn't quite pinpoint all of the changes the x-pipe made (with new 02 sensor). I began by critiquing the sound from the drivers seat. At first, I wasn't too impressed. I felt like I was riding around in a ricer 4 cylinder with a coffee can muffler. At cruising speed, there wasn't too much of a difference in noise level over stock, but when I punched the throttle it made "the can" sound. Forgive me, but the words "cheap", "kidlike", and "unrefined" came to mind. I guess I prefer a more compressed sound......loud, but compressed; like a muffled roar instead of a whiney scream. I thought about how it would sound if I removed the intermediate muffler. I also thought I had better let the engine get nice and hot; maybe the computer has to remap itself also (?). I stopped focusing on the sound and started "feeling" the car. It definitely breathes easier. It revs noticeably quicker and actually feels like the car has lost a couple hundred pounds (feels lighter, zippier)....not because the cats weighed a ton, but because of the increased air flow and quicker revs; it hits redline fast in 1st gear. 2nd gear has lost some of its rocket takeoff torque. The torque boost is still there, but maybe a little higher up in the rpms and not quite as strong. At first, I thought maybe I actually lost some power, but after a bit of driving around and experimenting, I figured out that I just needed to relearn where the power shift points were. After that, I was saying "YES!!!!"; much quicker. I really like the 1st to 2nd gear transition now. Just because I didn't "feel" the 2nd gear boost, didn't mean I wasn't actually going faster. Also, I have to be more careful in 1st because it will spin the tires much easier.
After getting used to the new shifting experience, I started listening to the sound again. By now I had driven probably 40 or 50 miles, the exhaust was still a tad raspy sounding, but it had taken on more of a "ripping" instead of a "rapping". I thought that was cool. It sounded a little more "high performance". Part of it could be that I'm shifting at better points, part of it could be that the engine was completely warmed up, part of it could be that the computer adjusted itself (?). I think I'll unhook the battery ground and wipe the memory to see if that makes a difference somehow. (I also have Autothority chips installed) For now, I am pleased with the purchase and the changes it made, but what it really did was make me think more about what it would be like with a complete exhaust system.......beginning with headers

enjoy

JKelly

I just reused the old ones and then felt around them with the car on after I installed the X. They looked to be in really good condition.

pappy92651

Hello Thaddeus. You might get a set of the original gaskets for the flange, 928 111 127 02. The old ones will probably hold for a while but should be replaced.

Hello John. You will see some HP gains with the stock computer and stock exhaust. To see larger gains you need to lose the stock exhaust and run 2.5" pipes to the rear. You will also need to add more fuel if you do this.

Stage 1 = X pipe
Stage 2 = 2.5" pipes and rising rate fuel pressure regulator or piggyback computer
Stage 3 = Computer programmed with new fuel and timing maps

And so on. The Autothority chips might give you more low RPM response since they lean your mixture and advance your timing. Once larger pipes are installed this may also reduce your mid to high RPM power since you will probably be running leaner. Examples are given here;
http://www.performance928.com/cgi-bi...ss_parent=1125

Gains with stock pipes and without new fuel / timing maps are ~ 10 rwhp. Gains with 2.5" pipes and new fuel / timing maps are 20 ~ 30 rwhp.

Jim_H

I had the X Pipe with the stock rear muffler, no cats on my 90 GT, it was the coolest sounding car I have ever heard. I now have 2 1/2" pipes all the way back with Bullets, no cats. It doesn't sound 'quite' as nice as the old set up... till 4000 R's, then it roars. I don't know how you can get better HP gain for the $ than the X Pipe.

stuartph

Guys


I've got the bullet mufflers too, just got to wait to have a system built for me, was gonna have it done in stainless steel.


Stuart

GT UK

Jim_H

Mines in stainless, I love it.

drnick

i found this web site, might be usefull/of interest

www.exhaustsoundclips.com/

gm.htmlwww.exhaustsoundclips.com/gm.html

Abby Normal

Mine is getting headers, no cats with stock mufflers and RMB with stainless tips done right now. I'm using Jet Hot coated MSDS headers. What would be the advantage of the x-pipe to this system?

Louie928

You use the existing manifold/cat gaskets if they are in decent shape.
Louie

Louie928

The usual cat replacement X pipe won't be a direct fit to your MSDS headers. With any exhaust system on a 90 deg crank V8, you should use some sort of crossover between the two exhaust pipes. You could use a direct connecting piece of pipe (an H crossover), or a more efficient X crossover. The key thing on the X pipe is that the converging & diverging angles on the inlet & outlet pipe pairs should have an included angle of between 15 and 20 degrees and the center should be about 1.4 to 1.5 times the diameter of a single pipe. It's the same thing as two merge collectors connected end to end.

Jim_H

I figured the Professor could answer your question better than I.

Thaddeus

I like your new avatar, Jim. That's a bad-*** ride.

Lagavulin

Hey Abby,

That setup will be WAY too loud, and will sound like crap too; a worse-case-scenario!

I would recommend replacing the 'stock mufflers' (..they're just resonators) with a real muffler. If you're considering an x-pipe (..best bang for the buck out there by far), then buy absorption-type mufflers such as MagnaFlow or DynoMax which are a straight through design which doesn't rob power.

FlowMasters (..baffled-type) sound good when not using an x-pipe, but they are no good when max horsepower is desired; absorption-types all the way for max horsepower.

Jim_H

Thanks Thaddeus

Lag, Abby's is an 86.5, I thought those were 'real' mufflers. I thought 89 was the first year they went to the oversized muffler/resonator?

hacker-pschorr

Has anyone ever modified an X-pipe to fit up to a set of headers?