Catted vs Catless Headers Power Gains differences

[vagthomas]

Tried to look it up within the forum as much as possible, but couldn't find
something that specific. In case it does, re-direction would be most
welcome .

Well the title is pretty much self-explanatory. Basically, I have stock
exhaust with TRD Quad tip exhaust muffler and I am thinking of installing
headers with respective ECUTEK Tuning.

The question is whether the catted header power gains worth the value for
money. Compared to the catless ones, where the gains are pretty much
known, how much less gains are there with catted headers, for the exact
same set up?

And when I am talking abt headers, I mean both EL and UEL Question
applies to both of them.

Many thanks to all guys!

[StraightOuttaCanadaEh]

I asked this question once, and while every header is different, the average difference was about 10-15 hp. Doesn't really matter if EL or UEL, that just decides where in the rpm band the bulk of the power will be.

[vagthomas]

By this do you mean that with catted header you make 15 ps less than catless?
After searching in the forum I have concluded that catless with tuning may give arnd 20 whp.
Is this correct?

[22R]

Sub'd good post


22R

[StraightOuttaCanadaEh]

Originally Posted by vagthomas

By this do you mean that with catted header you make 15 ps less than catless?
After searching in the forum I have concluded that catless with tuning may give arnd 20 whp.
Is this correct?

I read that a header, tune dependent, will net you about 20-30 hp. That's catless. So a catted one will probably get you about 10-15?

[gtengr]

I would expect very little. The stock header is a 4-2-1 and doesn't look like it's robbing much power except for the cat.

[churchx]

StraightOuttaCanadaEh: but most of those 10-15 will come from tune. And catted aftermarket headers are not guaranteed to not get CEL with stock tune, just lessened chances, and also not exactly legal if anything done to stock cats including relocation/replacement with non-stock (which is the case) too. And it costs more then catless. That all makes catted aftermarket headers way less desirable, more expensive, less gains, and not legal too if inspection checks.
Imho better install aftermarket air filter + ecu tune OR go for catless header + ecu tune (with which disable cat readiness checks too for no CELs) leaving 2ndary cat in frontpipe stock. Cheaper/more power/as "legal" as catted aftermarket header. And you get also gains that aftermarket catted one brings, like change to sound (if UEL) with catted one too. About the only thing one has to remember with catless, that it's one of things that rise exhaust loudness, so some louder catbacks may result in too loud result if combined with catless header.

[StraightOuttaCanadaEh]

Originally Posted by churchx

StraightOuttaCanadaEh: but most of those 10-15 will come from tune. And catted aftermarket headers are not guaranteed to not get CEL with stock tune, just lessened chances, and also not exactly legal if anything done to stock cats including relocation/replacement with non-stock (which is the case) too. And it costs more then catless. That all makes catted aftermarket headers way less desirable, more expensive, less gains, and not legal too if inspection checks.
Imho better install aftermarket air filter + ecu tune OR go for catless header + ecu tune (with which disable cat readiness checks too for no CELs) leaving 2ndary cat in frontpipe stock. Cheaper/more power/as "legal" as catted aftermarket header. And you get also gains that aftermarket catted one brings, like change to sound (if UEL) with catted one too. About the only thing one has to remember with catless, that it's one of things that rise exhaust loudness, so some louder catbacks may result in too loud result if combined with catless header.

That last point is one of the concerns. I'm going for the catted header and front pipe to control sound and smell, but still have some performance following a tune. I wouldn't change anything on my car without getting a tune. In fact, I was planning to get a tune while the car is stock just to optimize it for the fuel that I use daily, but it is expensive so it's kind of on the backburner. But yeah, smell is a huge concern. I find driving behind catless cars extremely unpleasant so I wouldn't want to put anyone else on the road through that.

[nikitopo]

The difference is not that big. Do you have a difference of 10-15hp just because of the cat? Really? A correctly designed catted header can be quite efficient. An example is the redesigned '17 factory header which provides very good results. A user swapped this header with an aftermarket catless one and a better exhaust and the difference in peak power was just 3 hp! Torque dip and gains in this area is another story as it was designed on purpose to pass emission standards and give a better fuel economy.

[vagthomas]

Id like to thank everybody for all this valuable information. Except the TRD Muffler, my rest exhaust is stock. Within the month i am going for ECUTEK tuning, basically with stock exhaust set up and I was just thinking whether worths it to also go for cutted headers.
I am expecting +10 with tuning and based on what ive read +5 to +10 additional if cutted headers.
Does this sound reasonable?

[gtengr]

Originally Posted by nikitopo

The difference is not that big. Do you have a difference of 10-15hp just because of the cat? Really? A correctly designed catted header can be quite efficient.

A correctly designed cat is positioned as close to the head port as reasonably possible, which is detrimental to exhaust flow. A correctly designed cat that is efficient would also have lower cpi/higher flow capabilities than a stock cat. I wouldn't put much faith in the 3 hp over stock test you referenced.

[nikitopo]

Originally Posted by vagthomas

Id like to thank everybody for all this valuable information. Except the TRD Muffler, my rest exhaust is stock. Within the month i am going for ECUTEK tuning, basically with stock exhaust set up and I was just thinking whether worths it to also go for cutted headers.
I am expecting +10 with tuning and based on what ive read +5 to +10 additional if cutted headers.
Does this sound reasonable?

Yes. This is pretty much what you can expect. You should also use a better air filter. The factory one is pretty restrictive.

Originally Posted by gtengr

I wouldn't put much faith in the 3 hp over stock test you referenced.

It is fine, not many put much faith on the new exhaust manifold because "older is better..." :b

Here is the reference: http://www.ft86club.com/forums/showp...65&postcount=1

[Jyn]

I do not recommend an aftermarket header with a catalytic converter. Besides the power issues, the increased flow (and heat) will wear the converter away much faster. Not sure about the high flow cats manufacturers are using for their parts on the 86 platform, but I've seen them wear away in as little as 2 years on another platform.

I recommend a high flow catalytic converter in the front pipe instead. Minimal power difference but a significant portion of the benefits of having a cat. converter.

[churchx]

High flow cars are called "high flow" only due marketing reasons. They are normal cats just less dense / lesser cell count / less effective to actually clean up exhaust gases. But of course they are freer flowing, and "high flow" sounds much better then "less effective". There are no "magic cats" that are both less pressure drop and as effective as stock, no free candy, at least at similar part cost budget.
So those aftermarket headers with high flow cats are somewhere inbetween stock and catless. One can choose his own poison, but i'm still thinking that it's worth to not touch stock cats at all or go catless header & leaving frontpipe's stock cat, not something in-between, due bad price-performancy. Catless + 1stock cat should be similar to complete cylinder back exhaust set with both cats changed to "high-flow" aftermarket ones .. but not suggesting that due that being even worse priced bang for buck wise.
As many succeeded passing MOT tests (where they don't check visual, but analyze actual exhaust gases) with one stock cat, imho it should be reasonably efficient, if anything should suffer, then cat's efficiency during cold starts, when cat is not yet upto working temps (reason why header's cat is in such hurting flow position close to cylinders is for it to heat up sooner for tests of gases from cold start by newest standards (hmm, was it euro4 or euro5?)).