Cat delete - exhaust.

[Directedby]

I am still undecided on exhaust mod.

I am having Flowmaster 50's (want a small rumble with quite int - no drone) with x-pipe installed on Sat, however am still unsure about headers or Cobra Manifolds.

My exhaust tech told me tht if I delete (remove) the cats it would increase my performance by aprox 25 HP.

He would make a bolt in pipe for each side.

Any thoughts on Cat delete would be appreciates.

[rumble]

Uh, you DO live in California right? How you gonna pass them emmissions
problems?

[cyclone03]

I am still undecided on exhaust mod.

I am having Flowmaster 50's (want a small rumble with quite int - no drone) with x-pipe installed on Sat, however am still unsure about headers or Cobra Manifolds.

My exhaust tech told me tht if I delete (remove) the cats it would increase my performance by aprox 25 HP.

He would make a bolt in pipe for each side.

Any thoughts on Cat delete would be appreciates.

Holy Smokes, and your in California!
Nice guy willing to take a $10,000 risk for a couple $100?
Personally I cant see 25hp over doing it legally with New Hi Flow Cats and a 2 1/2" "x" or "h" pipe,maybe 5-10 if your lucky.Don't forget your retune to have the now constant check engine light turned off...

IMHO,not worth it.

[BUCKWHEAT]

I did the 50's first thing and the car had a nice burble, quiet inside and no drone. Then I added the Dennis cobra manifolds and X-pipe, keeping the 50's. The noise level changed dramatically. I like it, but it is definitely louder and you can hear the pipes inside while going down the super-slab. Can't say if the difference was the X-pipe, manifolds or both. Enjoy.


I am still undecided on exhaust mod.

I am having Flowmaster 50's (want a small rumble with quite int - no drone) with x-pipe installed on Sat, however am still unsure about headers or Cobra Manifolds.

My exhaust tech told me tht if I delete (remove) the cats it would increase my performance by aprox 25 HP.

He would make a bolt in pipe for each side.

Any thoughts on Cat delete would be appreciates.

[Directedby]

Uh, you DO live in California right? How you gonna pass them emmissions
problems?

emissions are tested every 5 years, factory cats will bolt right in.

[Directedby]

Holy Smokes, and your in California!
Nice guy willing to take a $10,000 risk for a couple $100?
Personally I cant see 25hp over doing it legally with New Hi Flow Cats and a 2 1/2" "x" or "h" pipe,maybe 5-10 if your lucky.Don't forget your retune to have the now constant check engine light turned off...

IMHO,not worth it.

Thanks, and I am a nice guy, too.

problem with hi-po cats is that they are as illegal asno cats. they are not certified for california.

is it really a $10,000 fine? also, how would they know to fine if i replace the factory cats when tested every 5 years?

[cyclone03]

Thanks, and I am a nice guy, too.

problem with hi-po cats is that they are as illegal asno cats. they are not certified for california.

is it really a $10,000 fine? also, how would they know to fine if i replace the factory cats when tested every 5 years?

Well Ten years ago it was,can't see it going down.
True they only Know when they catch the shop removing them.
I cant believe none of the hipo cats are EO certified.

Don't forget about the constant check engine light.

[FordNut]

Well Ten years ago it was,can't see it going down.
True they only Know when they catch the shop removing them.
I cant believe none of the hipo cats are EO certified.

Don't forget about the constant check engine light.
The high flow cats I installed had CARB EO numbers.

[Directedby]

The high flow cats I installed had CARB EO numbers.

please get me part number and make thanks

[FordNut]

please get me part number and make thanks
I'll check the boxes when I get home tomorrow.

[jobrien8]

In modifing this exhaust system that has HEGO's after the catalyst you will be changing the Air/Fuel ratios. The HEGO's that are before the converters measure the exhaust so that when you are in a "closed loop" mode your ratio is 14.6:1 (approxmatly). The downstream HEGO's are a monitor to make sure that all is well. If you don't get this, you will be in an "open loop" mode. Which is similar to running max rich, you will be running as a cold engine all of the time. There are many sensors checking the engine condition (ACT, ECT, TPS, MAF, etc.) of which the HEGO measures the O2 level
You would be better off using low restriction catalyst that has a CARB number.

[Directedby]

I'll check the boxes when I get home tomorrow.

thanks a lot. i spoke to dennis r. about CA cats and he said no hi-flo avail for CA yet. 3 speed shops in LA told me the same thing.

[GordonB]

Directedby,
Whatever you do, be sure to get your exhaust tips to stick out (like stock)a little bit or better if a little bit more than stock. My readings from all posts here strongly suggests this tip.
GordonB

[NAVCHAP]

DB: There is a vendor in San Diego that has a CARB Legal exhaust for the Panther Platform cars. I will PM the info to you. They are not a sponsor of the site, but several members from the LA area are familiar with them since the vendor sponsors dyno tunes with Jerry W. every few months or so. -kjs-

[Marauder8]

I am still undecided on exhaust mod.

I am having Flowmaster 50's (want a small rumble with quite int - no drone) with x-pipe installed on Sat, however am still unsure about headers or Cobra Manifolds.

My exhaust tech told me tht if I delete (remove) the cats it would increase my performance by aprox 25 HP.

He would make a bolt in pipe for each side.

Any thoughts on Cat delete would be appreciates.
Illeagle...................

[Lidio]

In modifing this exhaust system that has HEGO's after the catalyst you will be changing the Air/Fuel ratios. The HEGO's that are before the converters measure the exhaust so that when you are in a "closed loop" mode your ratio is 14.6:1 (approxmatly). The downstream HEGO's are a monitor to make sure that all is well. If you don't get this, you will be in an "open loop" mode. Which is similar to running max rich, you will be running as a cold engine all of the time. There are many sensors checking the engine condition (ACT, ECT, TPS, MAF, etc.) of which the HEGO measures the O2 level
You would be better off using low restriction catalyst that has a CARB number.


I just want to mention that removing the cats (which I’m not condoning) Does not make a modern EFI Ford vehicle run in “open loop” or any “limp mode”. It will simply eventually turn the “Check engine” light on after a few driving cycles. That’s all the rear O2’s do, they simply watch to make sure the cats are doing their job. If their not doing their job or missing… this is not enough of a fault to make the EFI go “open loop” all the time. And also removing the cats and going to a completely different, larger exhaust on the MM doesn’t adversely affect the A/F very much at all, they continue to stay at about 13:1 at WOT and no problem at normal every day driving.

Today’s factory exhaust systems are not that bad for having up to four cats and mufflers etc. Even on the ’03 Supercharged Cobra’s we found a muffler change only to be worth about 5-8 RWHP and then switching to a high-flo H-pipe with two cats only to be worth about another 15 RWHP. An entire 2.5” package on the Cobra’s though is worth more as you step up the boost.
Long tubes on the new Cobra believe it or not are only worth about 2-8 RWHP once you already have a complete 2.5” exhaust system from the manifolds back on one of the ’03-04 Cobra’s. We don’t even recommend long tubes any longer on the 03 Cobras because of the dollar to HP ratio. Maybe only if the guy has upgraded to a replacement blower like a Kenne Bell or Whipple.

I personally like to keep stock cats on most of the modern performance Ford’s we work on or go to after market cats as opposed to none at all. Especially on large vehicles like trucks and MM’s. Typically when you remove all the cats and go to a larger diameter pipe like 2.5” There is a gain in high RPM horsepower, no doubt… but down low, like below 2500-3000rpm they definitely become more sour feeling. This isn’t usually talked about much because it doesn’t show on a chassis dyno and you cant sell exhaust parts if theirs any talk of some sort of a performance loss any where. When you’ve got blowers, especially roots type and/or big rear gears… this loss in low end isn’t felt as much or at all.

I believe the reason MMs come with 2” exhaust in certain parts of it is to “tune in” some low and mid range torque. Back pressure is not your enemy in a heavy car with a small motor. These days even on my mid range street/race cars like my Mach-1 which has a Kenne Bell making about 19psi of boost, I run high flow cats and 100 unleaded fuel. Cats seem to straighten out exhaust noise and get rid of a lot of crackle and poppyness in the exhaust. Plus cats help to cut down on the drone that most people complain about when louder after market mufflers and catless pipes are used. Plus I simply like starting my cars in the garage and warming them up and not hear the wife complain about the exhaust odors. Even with the garage door wide open.

All the performance, racing and bragging I've done with my own MM is with the entire exhaust system totaly stone stock. Most probably still don’t believe this is possible. I know how much is left in it with a Kooks header and 2.5" every where else, but I just cant being my self to make my MM any louder then stock at this time.

[SergntMac]

Thank you Lidio, for another great discussion.

When Lidio points out the loss of power in lower RPMs from opening up the exhaust system, he is right. We knew this a very long time ago, when Hooker fabricated headers for my #1x Kenny Brown car. They tried three designs, all provided improved numbers in the higher RPMs, but stole that power from the lower end, under 3000 RPM. This shift in power and the cost of the headers back then (mid '02, and over 1500 bucks for headers alone) made it all an unworthy prospect, based on what was known at the time, and consumer interest of the day. When Kenny Brown released his Marauder S for production, it came with the OEM exhaust in place. Only recently, do they offer a Kook's/Magnaflow option.

Sean Hyland tried too, working with Kooks, and the customer demand wasn't there. To my knowledge Sean Hyland didn't sell one set, at least not to anyone talking about it here, and I think it was because the end cost. After all the necessary add-ons, cost jumped to over 2K, without install and for what? To lose low end power?

The power trade is still true today, and you can see it in the dyno reports when you pay more attention to what's going on in the pull, rather than the RW end result. But, "we've come a long way, baby," and today there are new tuning theories and talent, as well as a plethoria other mods that help work out this shift of power, such as UD pulleys, the lighter Stallion TC, the electric water pump and so on. The end result seems satisfactory to most of us, but this doesn't mean the trade doesn't take place. It does, because that's what happens when you increase exhaust system OD.

When enthuiasts demand a specific product and believe so strongly in the good of it all, a smart businessman meets that demand. The products seem to sell themselves by popularity. If you look at the top ten performers in the timeslip database, you'll see that more have exhaust mods than not, and with some whopping kickazz 0-60 times to boot. So, while the power trade is true, it's impact on total performance is minimal. But, it's still there. Should you be the one MM owner who buys an exhaust kit and just an exhaust kit, you won't like the end result, period, and there's no escaping that.

The question y'all need to answer before buying any mod, is how do you want to enjoy your MM. If you're getting into (or returning to) the seasonal weekend racing circut, seems to me that low end/high end power trade is amusingly irrelevant. The goal is to win the race, and headers, high flow cats, X pipe and increased OD will help you win, as long as you consider other mods that help. If you just want some improved sound, start at the back with resonator delete tips, and work forward until you like what you hear. If you're a highway driver, or towing a light trailer through some rolling hills on a regular basis, think about it all one more time?

BTW, it's never good to mess with Uncle Sam's rulebook, he seems to get the last word every time.

[Directedby]

Thanks Lidio - great stuff.

Thanks Mac - great stuff.

[cyclone03]

Backing up Mac...
I have the complete Kooks set up and the first time I drove my car after the install I noticed the loss of low end torque.Thank goodness I installed a PI converter 2 weeks later or I would have had a Kooks set up for sale.Yes It's that bad.

[Smokie]

I had installed in my car not long ago a complete exhaust system: SVO shorties, HI-Flow cats, X-pipe all 2 1/2" to 18" magnaflow mufflers to stock tips. I posted on it with graphs and numbers, so I rather not repeat the entire story; but I can summarize the results for you.

I gained about 15hp/15tq, the car sounds better in my opinion, my 60' times dropped from an average of 2.3 to 2.1.
I don't have gears or converter, just what came with the car. Don't know if I lost low end torque, it feels quite the opposite. At the track the car performed very strong and consistent in bad track conditions.

In conclussion I am very pleased with the results of the exhaust swap.

[crowdog]

In modifing this exhaust system that has HEGO's after the catalyst you will be changing the Air/Fuel ratios. The HEGO's that are before the converters measure the exhaust so that when you are in a "closed loop" mode your ratio is 14.6:1 (approxmatly). The downstream HEGO's are a monitor to make sure that all is well. If you don't get this, you will be in an "open loop" mode. Which is similar to running max rich, you will be running as a cold engine all of the time. There are many sensors checking the engine condition (ACT, ECT, TPS, MAF, etc.) of which the HEGO measures the O2 level
You would be better off using low restriction catalyst that has a CARB number.
I believe BBK offers some plug in devices that replace the rear sensors and eliminate the check engine light problem. I don't know the part # but I think they call them MIL eliminators. Is anyone familiar with these?

[RF Overlord]

I don't know the part # but I think they call them MIL eliminators. Is anyone familiar with these?Yes, and that is exactly what they're called.

Anyone with the SCT tuning software can shut off the rear O2 sensors, so there's no need to buy MIL eliminators...

[FordNut]

Sean Hyland tried too, working with Kooks, and the customer demand wasn't there. To my knowledge Sean Hyland didn't sell one set, at least not to anyone talking about it here, and I think it was because the end cost. After all the necessary add-ons, cost jumped to over 2K, without install and for what? To lose low end power?

Jim (jspradii) got a set of these from Sean Hyland. The difference between them and the current Kooks is they had larger diameter primaries and collectors. So the effect (losing low end torque) was even worse with them than with other options.

[FordNut]

please get me part number and make thanks

OK, I have used two different model numbers from Magnaflow, both are stainless and have polished exterior heat shields. They are models 54306 and 94306. They do have CARB EO numbers but are not certified as OBD-II compliant. However, Magnaflow does have universal replacement high flow cats that are CARB OBD-II compliant, check for model numbers here:

http://www.car-sound.com/universal/430.htm

[Directedby]

OK, I have used two different model numbers from Magnaflow, both are stainless and have polished exterior heat shields. They are models 54306 and 94306. They do have CARB EO numbers but are not certified as OBD-II compliant. However, Magnaflow does have universal replacement high flow cats that are CARB OBD-II compliant, check for model numbers here:

http://www.car-sound.com/universal/430.htm

these look great, but what about the sensors/check engine light problem?

[FordNut]

these look great, but what about the sensors/check engine light problem?
If you use 4 high flow cats in place of the 4 OEM cats and keep the O2 sensors connected just like they are, there should be no problems.

PS. I got stainless steel O2 sensor bungs for my system from Pro-M, check their website and online store.

[Glenn]

There are many, many opinions on exhaust systems and what to install, etc. I had always thought that the Kook's was the top setup and for most it probably still is or is it? Many MM owners are not really looking at keeping the stock mufflers, tail pipes and tips. I now believe the Cobra shorty headers and hi-flow Cobra X-pipe with CATS is an under appreciated power producer for many owners with very little cabin drone but a nice low growl from the exhaust. My dyno tests indicate it was worth a good 15 hp for a total of 281 hp. My MM feels very strong with this set-up, even in the low rpm range and ran a best of 14.00 at SSHS4 (the car won 4 rounds in A class). A good driver should have been able to do at least a 13.9 sec 1/4 mile. A set of drag Nittos could have even reduced it to a 13.7. The BFGs kept going up in smoke.

What I am saying is that in the 1/4 mile the above exhaust set-up may well deserve another look by some owners even if it does not carry the bigger hp numbers.

[studio460]

Uhhhh . . . I LIKE cabin drone.

I am REPLACING my Flowmaster Deltaflow 40s for Flowmaster "Original" flow 40s, which is their loudest muffler (louder=gooder). I'm also replacing my Megs delete tips with SLP 3" tips like the ones on the Trilogy car that I ordered like five months ago.

Thanks to everyone for telling the truth about the low end stuff. I always thought I would lose some power down low with a more free-flowing exhaust. Now I can finally rest happy with my muffler & tips-only exhaust mod, 'cause I've been delaying that install for months now, since I've been so hung up on deciding which header solution to choose. I think I'll finally do some gears instead. Yup, 4.30s are next for me (actually, 4.10s, because with my lower-series tires, my final ratio will work out to be about equal to 4.30s with the 4.10s installed). Then I'll install my P.I. torque converter that's been sitting under the bed for the last six months. Then in January . . . I'll be ready for that ProCharger!

[RF Overlord]

what about the sensors/check engine light problem?

Paul, see my response (#22) above ^^^...

[FordNut]

I believe BBK offers some plug in devices that replace the rear sensors and eliminate the check engine light problem. I don't know the part # but I think they call them MIL eliminators. Is anyone familiar with these?
They are visible and you won't pass the inspection with them installed.

[281MERC]

the need for back pressure is complete bull*****, except on my dirtbike BRAAAAAAAAAAAAAAAAAP!!!

[Black_Out]

25hp from removing the cats? :lol:

I wish!

[rocko112869]

I have an 03' GM (aeroturbines,Xcal2,3:55)think in about getting rid of the rear cats...in reading this post will my Xcal 2 be able to put out the check engine light if it comes on? other than that it should have any ill effects correct

[rocko112869]

I have an 03' GM (aeroturbines,Xcal2,3:55)think in about getting rid of the rear cats...in reading this post will my Xcal 2 be able to put out the check engine light if it comes on? other than that it shouldnt have any ill effects correct

[musclemerc]

Way to go..... Reviving ancient old threads! Your name would be Aren by any chance?

[justbob]

the need for back pressure is complete bull*****, except on my dirtbike BRAAAAAAAAAAAAAAAAAP!!!
Your wrong.

25hp from removing the cats? :lol:

I wish!
Your right.

I have an 03' GM (aeroturbines,Xcal2,3:55)think in about getting rid of the rear cats...in reading this post will my Xcal 2 be able to put out the check engine light if it comes on? other than that it should have any ill effects correct
Do you have a tune? If so, contact you tuner and simply ask if the rear o2's are turned off in the tune that you have. If not, then no, you can't do it by yourself.

[Adam12]

the rear cats are NOT monitored cut them out you dont need them there just a secondary scrubber cat. i deleted mine and have an x-pipe with 40s and resonated delete tips. it sounds incredible

[Drewstang]

Holy old thread, Batman.