Highflow catalytic conv. HP Gains?

[jibbby]

This has been pressing for a while.... A few independant studies have shown that changing the catalytic converter to a highflowing catalytic converter in SC's does just about nothing for you.... I am now discussing and debating this same subject on the CL forums with others and need to hear from you guys about this....

My 1992 SC400 Lexus has been dealer maintained with 100,000 when I first changed out my stock cat..... I purchased a Magnaflow 2 into 1 highflowing catalytic converter...This is what I found, tested and discovered during the mod change:

1) Immediately after my stock cat was removed and still hot to the touch I put the new magnaflow cat next to it and shot compressed air threw both to test the difference in passing air flow.. The stock backened cat of 14 years was barely was able to pass the air out the back and the new Magnaflow allowed the air to pass like it wasn't even there....

2) This magnaflow cat. has a high flow built in Y design that replaces the first stock Y...I believe the flow is increased with both the cat and the built in Y...


I road tested before and after the install. I noticed power gains clearly and immediately to my suprise... Only the cat was changed out at that time and nothing else on my exhaust system...

Now how does you explain this? I truley believe there are nice gains to be made and I thinkI proved it, but so many think otherwise...Why do the experts say different? I don't think my stock cat. would be any different or worse off then any other 100,000 older lex car... Am I missing something here? Here is a pic....

Anyone?

 

[bansheebuzz]

comparing an new high flow cat to an old stock cat with 100000miles of use is no test.

You need a new stock cat and a new hi flow to do a proper comparison.

 

[Peewee]

As above, you have to test new for new.

And you can't test new crap vs new expensive.
Its the same with anything.

There are crap cats, and good cats.

I personally don't believe there will be any benefit to a high-flo cat/metal cat/magic cat vs a quality standard cat.

What I believe you have to do is put 'oversized' cats on the car.
I have twin 2.5" into a single 3".
Simple maths shows that twin 2.5" is much greater than a single 3", so twin 2.5" cats will still outflow the single 3" pipe.

If I used twin 2.25", then maybe it would be a restriction.
If I used twin 2", then for sure it would.

 

[stevechumo]

This Magnaflow is a good and hi-performance cat. It's not a regular replacement cat. As with the concept of larger pipes, this Magnaflow will make more hp by itself. Of course there'll be more technicalities to this than just bigger is better. Hi-flow cats allows more gas to flow, thus reducing backpressure. So even new Lexus cat can't flow as good as this Magnaflow cat. All Lexus exhaust systems are to reduced noise to the minimum, which hurt power. We all know this plus it's the same concept as when we delete the cats. The hp gained is very noticeable and variably. That's why many track cars have no cats. No questions asked. I've been playing with several exhaust systems on other cars and I know this for sure.

 

[jibbby]

Thanks for the replies fellas..The thing about this discussion is that I know there are gains to be made with this mod, but write ups on Planet Soarer and so many others say the stock Cat flows as good as any other other high flowing cat...Then in my discussions on the Club I found that with the stock cat when it is headed to operating temp the metal or insides expand allowing to the air to pass thru more efficiently..Is this true? .So again they are saying my compressed air test in really not a good test at all...Any gains being made from this mod are strictly because of the Y design built into the cat and not the cat itself.....

I told them they are all wrong....I told them that Planet Soarer is wrong and probably did a new cat to new cat comparison and not the old cat to new cat.... Then I mentioned that on a 14 year old Cat. converter there has got to be some clogging going on.. Am I wrong in saying all this?

 

[Damien]

The gains your found are because you replaced an old cat which was probably clogged with a new one - any new cat fitted to your car would see an improvement.

The most restrictive part of your exhaust is where it merges into 1 pipe, then you've put something even more restrictive at that point... better off with 2 oversize cats before the Y as Peewee suggests.

 

[Autobahn_stormer]

All in all a combustion engine is a glorified air pump and shining example of inefficiency. Anything you do to assist the evacuation of air and "lighten the load" on the engine is going to improve efficiency. So by replacing your old clogged cat (s) with one that flows better than the stock one way back when it was new is gonna help no matter which way you look at it.
if you're worried about back pressure then take a closer look at your exhaust I.D.
but i could be wrong