Cat By Pass

[Loteuk]

Just about to buy the pipe but wondered what the characteristics are with the sports exhaust.

The Exige just popped and banged on decelleration but not much louder.

Does the car run better?

[Vulcan Grey]

Just about to buy the pipe but wondered what the characteristics are with the sports exhaust.

The Exige just popped and banged on decelleration but not much louder.

Does the car run better?

Yes much. Very loud and can shoot flames (depending on tune and ECU).

Another good option is to use the straight tube, but have a small BORLA muffler where the CAT normally goes. SOunds great. Runs much better, no lag, no bogging.

[karmavore]

With out proof I

[rens914]

I just emptyed my cat and put it back in position

runs better, sounds better, looks better (flames till 1 meter on the circuit)

the only problem is the annual emission test

but

my son is a mecanic certified to test

NO PROBLEMS

[TSD]

my g car now has a straight through and seems to have much less lag than compared with the OE cat

[Vulcan Grey]

With out proof I

[karmavore]

My point was only that you can have the best of both worlds with a proper cat.

[Mysterae]

I've decatted my Esprit and have a ss sports exhaust from SJ's fitted. Certainly increased the amount of pops and bangs, all good fun. I've just recently done the ram-air mod and the noise is erm, unique with it all combined. The engine definetely inhales and exhales a lot more easily imo.

And it just passed a legitimate MOT test no problems.

[CarlC]

Same here - Decat with SJ Super Sports. The exhaust is much louder and shoots flames. Very few pops and bangs If done with air filter upgrade RAM Air mod and uprated exhaust its worth doing and you will notice a positive improvement in the cars running.

Alan,

WOW! this setup passed genuine MOT. Excellent Ill get my machanic to see if mine will pass too! Fingers crossed and thanks for the info.

Edited August 10, 2006 by CarlC

[Mysterae]

Carl, it passed because of the lower requirements for the year of the car, plus some good quality fuel imo.

- First used before 1/8/1975 - Visual test only. Failure for excess idle speed, dense blue or black smoke for 5 seconds at idle or during acceleration up to 2500rpm or half engine max speed whichever lowest.

- First used between 1/8/75 and 31/7/86 - meter test CO <=4.5%, HC<=1200ppm.

- First used between 1/8/86 and 31/7/92 - meter test CO<=3.5%, HC<=1200ppm.

- First used between 1/8/92 and 31/7/94 - advanced emission test (CAT) if its running on petrol when presented, to the vehicle specific limits usually around CO<=0.3%, HC<=200ppm and Lambda 0.97 - 1.03.

"The MOT is testing emissions, so if the emissions from the tailpipe meet the requirements the vehicle passes. Whether a CAT is fitted is irrelevant. The deciding factor is the vehicles date of first registration. A "Cat" may be fitted to a vehicle which only needs to meet the two gas test and if the emissions are satisfactory, it passes. A "Cat" may have been removed and the vehicle is required to meet the "Cat" test standard by virtue of its first registration date. If the emissions meet the standard then it passes."

Plus I had my fingers crossed

[Loteuk]

Thanks chaps,

the sj exhaust is on already so the cat will follow.

The replacing of the cat isn t an issue for the test once a year -easy off ramps.

I was just concearned the thing would sound like a stock car.

Its fairly noisy in the cab anyway so might leave the ram mod.

[superdavelotus]

Hi Tony, I was at PNM yesterday. They have just taken delviery of 100 cell race cats. Pete plans to fit one to a decat pipe to give owners the option of having a race CAt but pass MOT emissions. I never really thought that there would much demand for 4 pot owners but we'll have to wait and see.

He's also doing a set for my V8 in the next few weeks.

[russellbosier]

Hi Dave,

Do you know what the likely price would be for a 4pot race cat pipe?

[superdavelotus]

Hi there,

I guessing about

[superdavelotus]

Price firmed up at

[carl12359]

Lucas, I have proof the straight pipe exhaust results in huge gains in power,

torque and driveability. My car with just a K & N air filter, #1 chip and the

straight pipe exhaust resulted in 294 rwhp and 333 lb ft TQ on the Dyno.

I would recommend this exhaust to everyone interested in making more

power (almost everyone). I was very impressed with the power and increased

driveability after fitting my car with the straight pipe. Everyone I know that has

the straight pipe is extremely pleased with the results.

Carl

Red 89SE

[karmavore]

1) Argh... not my point. I'm sure it did. Now compare that versus a hiflow cat and you'll make or break my point.

2) Let's see the chart.

Edited August 13, 2006 by karmavore

[carl12359]

I would be interested in seeing the net gains in power

with the cat-back vs cat bypass. I will be putting my

stock exhaust on this fall to pass emissions, but before

I put the straight pipe on I'm going to have it dynoed

again to get some baseline numbers.

I can fax you a copy if you wish.

Carl

Red 89SE

[karmavore]

Wouldn't you much rather have a system that is both efficient and optimized that ALSO passes emissions, reduces emissions, and reduces the hassle of having to swap exhausts back and forth???

Check out Random @ http://www.randomtechnology.com/

PS: Not to doubt you...but what happened to the 294/333 chart?

[carl12359]

I can fax the 294/333 chart to you.

Interesting website.

I can swap out exhaust very easily, probably in an hours time. Well worth the effort given the results.

And yes in a perfect world I would like to have an exhaust with reduced emmissions, and no loss in power.

Do you have any dyno numbers? I am really interested in seeing what the net gains are in the cat-back vs

cat-delete systems.

Cheers,

Carl

Red 89SE

[karmavore]

Sure mate, lots of dynos on my site:

Here's the direct link: http://retrophit.com/janedyno.html

I'd love to see yours, but fax isn't an option at the moment...

[carl12359]

Hi Lucas,

Seems like your new exhaust made big HP gains even with the OEM chip, if I'm reading it correctly.

Very impressive gains with the cat-back system.

BTW: Nice ride

Cheers,

Carl

[Jussi]

Just throwed the cat away (I mean the cat in the car not in the house )

There's now straight pipe where used to be cat There's much less lag now than with cat. And car is running better at lower rpms. Sound is not so loud, I was hoping it to be louder But it makes now nice pops when engine braking

I'm happy with it now...hmm. just wondering how it will sound without muffler