Anyone running one? I had a chance to hear it yesterday on a 5 speed GTS.

Sounds awesome. In fact sounded killer! No time to drive the car but reliable sources give two thumbs up.

 

I know a few people up here in the PacNW 928 group that are running them, and all owners give a very enthusiastic yes! to glad they bought it. Seems like a great way to go for power vs. dollar. I'll be putting one on my S4 eventually, and trying to get the old man to put one on his GTS as well. They do sound gnarly and add something like 25+ hp and torque? My S4 still passes with "clean cats" so I'm ok with running one without cats entirely. Anyone else have input?

 

I'm curious what benefits are achieved with the crossover pipes. With American V-8s, it tends to increase torque. If that is true with our engines as well, it would be a good mod. I'm just curious about seeing a dyno run with the same exhaust, headers, etc. But just have a run with a crossover, and one without... I'd like to know *exactly* what benefit those pipes have on our cars...

 

I'm planning on getting a cross-over fabricated for me this summer.

Does anyone know how much I should expect to spend? I was quoted $350 from a local shop that has done them before, but I've been told that the actual price should be about 1/2 that.

I've been too lazy to try to negotiate with the same shop yet, but I've got my tax refund now, so it's time to start thinking about how to spend some $$$.

 

Allow me to answer my own question:
(I did some research)

What's a "Balance Tube? Do I want one? -

IF YOU HAVE DUAL EXHAUST, AN "H" PIPE, OR BALANCE TUBE, can aid in reducing that resonance, or "drone", which plagues most short wheelbase vehicles. One about 1 1/4" in diameter is suitable for this application, and should be placed as far forward as possible, according to the literature. Within the past six months Hot Rod Magazine and Car Craft Magazine have done articles on exhaust systems, and addressed the issue of balance tubes. The consensus is that they 1) reduce noise and 2) improve low-end torque. Most people don't realize that dual exhaust with no downstream connection actually makes the V-8 function as two separate, slightly unbalanced, four-cylinder engines. A common misconception is that exhaust gases freely pass back and forth between the two exhaust systems if a balance tube is employed. This is not so. In operation, this short pipe serves mainly as a plenum, or type of resonance chamber. This compliments the plenum found in the intake manifold where both cylinder banks are already "connected". The resulting dynamic feedback balances the sound waves which pulse throughout the intake and exhaust tracts when the intake and exhaust valves open and close. This improves scavenging, and results in a smoother running, and quieter engine. The underlying physics and dynamics of the relationships between intake runner length, exhaust tube diameter, and length, are deep, but in a nutshell, it works for you in good ways.

------------------------------------------------------------------

6 to 10 H.P.'s for under a hundred bucks.

Yup that's right, all I installed was a pipe connecting both exhaust pipes together right before the catalytic converters. I would have never thought this would work. Steve Merenkov (my new friend) asked me to try this. That he had heard it would give a 6 horsepower increase. This did not sound possible because of the way exhaust flows. I would have never thought that exhaust would flow at a 90 degree angle. So I went to my local muffler shop and had them install an h-pipe. Even the muffler shop predicted a no horsepower gain because they felt that the exhaust was regulated enough due to the new fuel injected engines. They felt that this type of application would work for a carburated car but not for a fuel injected car. Well folks, me being very curious I thought what the hell, lets do it! Installed the h-pipe went down to the Dyno shop and had a 9.2 horsepower increase and a 7.9 torque increase from stock baseline.

 

Hey Brian,

Check out this link.
<a href="http://www.seanet.com/~midlman/vandyno.html" target="_blank">http://www.seanet.com/~midlman/vandyno.html</a>

I put an Ott crossover on my 87 S4 and did before after testing.

The car (87AT) at the time had autothority chips, adj. FPR, and the injectors had been cleaned. Put out 275hp and 293Ft-lbs . Swapped out the cats for the X-crossover and ran again. Got 284hp and 302ft-lbs. Almost 10hp and 10ft-lbs...definitely gave a nice sound too....

Later I swapped out the S4 mid resonators for the GT resonators......it sounded like Nascar when I floored it...

Probably more to gain by going with 2.5 inch pipes all the way back....

Well worth it IMHO..

later,
Tom
midlman@seanet.com
87S4 AT
89GT

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by bcdavis:
<strong>I'm curious what benefits are achieved with the crossover pipes. With American V-8s, it tends to increase torque. If that is true with our engines as well, it would be a good mod. I'm just curious about seeing a dyno run with the same exhaust, headers, etc. But just have a run with a crossover, and one without... I'd like to know *exactly* what benefit those pipes have on our cars...</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">

 

One more note, I believe Louie did some testing with the H pipe vs the X crossover,and found that the H pipe would have more of an uneven sound (Harley like)and produced less power.

Also, the S4 cats have a sort of merge collector right at the front where the O2 sensor sits, so the system is balanced there. Not sure if the 85/86 cats are the same....

In reality, Porsche did a pretty good job with the S4 exhaust system (manifolds and all) so gains are minimal at best...but every little bit helps...

later,
Tom

 

It's true the Ott sound is really sweet.

Some other considerations - pollution - increase in NOx I believe, and obviously unburned fuel or hydrocarbons.

On the positive side, heat damage from the cat on the torque tube bearing, foam insulation is removed.

 

AWESOME!

Something to look into...

Exhaust mods are pretty cheap...

 

Do you know if Louis Ott is making a cat bypass for an 85? How do I get in touch with him?
TIA
Glen

 

n/t

 

BTW, I will be picking up my X-over from Louis hopefully sometime next week. Can't wait to see how it sounds and performs!!

Everyone I've heard from who has this mod seems to like the way it sounds and feels on response. With proven dyno results of +10HP/Torque.

I posted on our web board here at Pac928NW and got his e-mail. So who ever is interested or want to purchase it's louisott@cs.com

-Andrew
'87 S4 (soon to have an X-over)
'84 S

 

Anyone know if there is a differance between the L.O. X and the DR. gas X?

Does Mr. O. have a website?

<img src="http://www.drgas.com/photos/gfx/tandems.jpg" alt=" - " />

<a href="http://www.drgas.com/index.html" target="_blank">Dr. Gas</a>

 

What's the cost on Ott X-over?

 

Note that the $180 Dr. Gas is of aluminized coated (steel) construction.