Big Dave

For those of you who have gotten the Ott cat bypass, how difficult was it to install?

I'm curious whether it's a quick job or something that requires removal of other items to make the removal of the cats and the installation of the bypass possible.

Thanks in advance for any information. <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />

DoubleNutz

VERY SIMPLE! Changing Spark plugs is harder.

Big Dave

Thanks Pat!

<img border="0" alt="[thumbsup]" title="" src="graemlins/bigok.gif" />

Mark

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Carerra4_PRDATR:
<strong>VERY SIMPLE! Changing Spark plugs is harder.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Well....it was a little tougher on my car, as it is a EURO...during the 'federalization'....everything past the flange connection was welded!! But - if yours is not this way - it is pretty dang easy!

BIGGEST HINT&gt;&gt;&gt;The flanges will not line up EXACTLY...get a bolt in each side loosely. Use a philips screwdriver as close to the size of the flange bolts on one side and stick it in the holes to be able to manipulate the other bolt hole in line. Tighten up those 2 bolts, install the 3rd...repeat on the other side.

Because of my 'weld' issue, I had to take the whole exhaust off (from the flanges back) and take it to a muffler shop to weld it all up for my "track car" $40.
I found it easiest to support the 'loose-yet-assembled' rest of the exhaust system with blocks/boxes/etc to bolt up the x-over to the manifold flanges, and then re-attach the rest of the exhaust.

Dave - you gonna love the sound...and the 'assometer' will notice and record the performance improvements!

goodspeed928

BIG DAVE,
How much?

Big Dave

Does the whole exhaust from the cat back need to be removed and then reinstalled?

Big Dave

$350 for the bypass, including shipping.

928 Forum subscribers get a $25 discount.

A local muffler shop was offering to fabricate and install the bypass for $325, but I'd rather "bypass" the sales tax, install it myself, learn something, give back to a true 928 guru, and benefit from some superior craftsmanship.

Dave

Z

There was also a fair bit of time put into reasearching and testing to find the best size of the area of merging, and best angle of intersection, between the two pipes of the "X" with the Ott piece. You aren't going to get that with the muffler shop piece.

DoubleNutz

Dave you can correspond directly with Louis in "Ott's Garage" at <a href="http://www.pacificNW928.com" target="_blank">www.pacificNW928.com</a>

Big Dave

Thanks, Pat.

I've already exchanged a few emails with him. I was asking this question here to avoid bugging him too much.

Dave

Normy

I want someone to take a fairly stock Euro/ROW/S2 and dyno their car before and after removing the cat/ adding Louis "X". Preferably this would be done after dynoing the car before and after adding headers...

And of course- a Borla dual exhaust or equivalent would be mounted...

Since just adding an "X" does nothing more for performance than painting a giant "X" on your hood~



N-
'85 S2 5 Speed

LT Texan

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Normy:
...painting a giant "X" on your hood~



N-
'85 S2 5 Speed[/QB]</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Normy,

What kind of paint for the most HP increase?

Z

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Normy:
<strong>I want someone to take a fairly stock Euro/ROW/S2 and dyno their car before and after removing the cat/ adding Louis "X". Preferably this would be done after dynoing the car before and after adding headers...

And of course- a Borla dual exhaust or equivalent would be mounted...

Since just adding an "X" does nothing more for performance than painting a giant "X" on your hood~</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Here's a copy of a post detailing some dyno tests of various exhaust configurations on a GT. It was originally posted by Tom Cloutier. Hopefully the tables will like up correctly. To summarize the stock cats vs "X" pipe comparison, replacing the cats with the "X" pipe resulted in a gain of 19 hp and 23 ft/lbs at the wheels.
----------------------------------

Louie Ott and I have been working together recently to test several
different exhaust configurations. Louie did the dyno testing with his 1990
GT on a Dyno Jet in accord with the DEVEK protocol. I have done the data
compilation using Excel. This is an excellent way to compare the averages
of three dyno runs for multiple configurations. The data used came
directly from the raw data print out for each dyno test. I calculated the
areas under the curves in order to quantify the performance of the car
over the entire speed range of the test, not merely peak values. We
compared total (average) torque and power as well as the time required to
accelerate to a particular rpm.

Louie put forth a Herculean effort to conduct most of the tests on a
single day. A basic question we wanted to answer was how much
performance loss is associated with the stock exhaust system, including
catalytic converters. And how much loss is attributable to the mufflers
and pipes, and to the cats? To answer these questions, Louie established
a stock baseline. Then, on another day, he ran tests with no plumbing
connected after the cats and then with 2.25" pipes replacing the cats.
Finally, on a third day he conducted the major portion of the tests.

We also wanted to know how Louie's X crossover and my venturi merge
collector systems compared to the cat bypass systems. We didn't have a
cat bypass, so we substituted the stock head pipes with the H crossover
and 2.25" pipes in place of the cats. We're both of the opinion that the
stock H crossover is more efficient than that in the commercially
available cat bypass systems. We also wanted to know if there was any
performance gain after installing a K&N air filter. The tests were done
without a tailpipe or muffler to eliminate the effects they might have.
Appropriate length and diameter pipes were added as necessary to maintain
approximately equal lengths for each configuration.

Among the configurations tested were:

1. Stock (baseline)
2. Stock cats without muffler or tailpipe
3. Stock head pipes with H crossover with 2.25" pipes replacing cats
4. Dual 2.5" head pipes, 4" X crossover, dual 2.5" pipes out, no muffler
or tailpipe
5. Burns Stainless type venturi merge collector with two 2.5" head pipes,
3" venturi, 3.5" single pipe out without muffler or tailpipe
6. 4" X with full exhaust and K&N air filter
7. 4" X crossover with Louie's full dual Bullet muffler exhaust system
8. 3" venturi with straight 3.5" tailpipe and Magnaflow muffler at end

Louie utilizes the X-type crossovers in his dual exhaust systems while I
use the Burns Stainless venturi merge collectors in my Avenger and
Scavenger systems.

Results

Stock Exhaust System (Complete):
Maximum loss of 32 lb-ft and 28 hp. Average loss of 20 lb-ft and 18 hp
compared to stock H. This compares the dead stock configuration to the
stock H with no cats or mufflers.

Stock muffler & pipes:
Average loss of 11 lb-ft and 10 hp. This is the contribution by tailpipes
and mufflers to total loss.

Stock dual cats:
Average loss of 9 lb-ft and 8 hp. Cat contribution to total loss.

K&N air filter:
Loss of 3 lb-ft of torque and 3 hp compared to stock filter.

Cat bypass vs 4" X:
The X crossover gains 14 lb-ft of torque and 11 hp more than stock H.

Cat bypass vs 3" venturi:
The venturi gains 19 lb-ft and 16 hp more than the stock H.

Using the stock baseline as a basis, the average performance gain for each
configuration is tabulated below.

________________Average___Average____Average__%Gain Over__%Gain Over
__________________TQ_____%Gain______HP______Baseline_____Stock H

Baseline___________266______Basis______227______Basis__________
Stock Cats, Open___277______4.0%______237______3.9%___________
Stock H, Open_____286______7.1%______245______7.2%________2.9%
4" X, Open________295______9.7%______252______9.9%________3.2%
3" Venturi, Open____296_____10.1%______255_____10.7%________4.2%
4" X, Full_________299______11.0%_____255______10.9%_______3.5%
3" Venturi, Full_____297______10.3%_____254______10.4%___________
Stock Air Filter____293_______9.2%______250______9.2%___________
K&N Air Filter____290_______8.1%______247______8.1%___________

Time to reach given RPM for the various configurations tested.

________________Average Time per_______Elapsed Time
_________________100 RPM (sec)_____2700 to 6400 RPM (sec)

Stock Cats___________0.216______________8.01
Stock H, Open________0.199______________7.54
4" X, Open___________0.187______________6.94
3" Venturi, Open_______0.186______________6.89
4" X, Full____________0.185______________6.85
3" Venturi, Full________0.187______________6.90
Stock Air Filter________0.188______________6.94
K&N Air Filter________0.190______________7.03

Even though a muffler may be a non-restrictive type, it and the
associated plumbing often increase the back pressure in the system. We
found that the addition of after-market tailpipes and mufflers increased
performance. You may have noticed that the venturi gave slightly more
performance than the X crossover in the tests with open exhaust systems,
but slightly less with tailpipes and mufflers attached. The test tailpipe
and muffler used with the venturi was simply a straight piece of 3.5" pipe
with a straight-through Magnaflow muffler attached to the end. We both
feel this configuration was freer flowing than the dual pipes and mufflers
used with the X crossover and, with a little more back pressure, would
have given better results. Although back pressure increases pumping
losses, and eliminating it should increase performance, this can also,
alter the flow characteristics of the whole system so that the
all-important port pressure at exhaust TDC is increased; as the power loss
from the impeded scavenge was greater than the gain from the open exhaust,
the result was less power. (Scientific Design of Exhaust & Intake
Systems; Phillip H. Smith and John C. Morrison). I know this statement
will be met with some objections and if there is a better explanation than
Smith and Morrison's, please let us know.

Louie and I have invested quite a bit of time and money in these tests and
hope the results are as illuminating for you as they have been for us.
There are about 7000 data and calculated values in this study! I'll post
the dyno charts on my website some time this week
(www.thepowerbroker.net). I can email the spreadsheet to anyone who wants
it. We'd welcome your input, questions, comments, etc.

Tom Cloutier & Louie Ott

Ell

Tom,
I am really surprised that K&N talks about how thier filter increases HP, and you found that there was a loss of HP.
So by the looks of this, you just dont want to run their filter. I wounder what K&N would have to say about this.

Ell

Mark

I was advised to stay away from the K&N for another reason...The oil on the filter can get on the heated titanium wire in the airflow sensor just below the air box...causing it to, literally, burn in two.