Great News, Sports Cat Finally Fitted!

[CAMSHAFT]

kev do you do custom systems, what i want to do is get a new system from the manifold back,i don`t need the manifold as the HKS turbo includes one, so i need all the new pipes,sport cat and maybe a back box as mine is a TTE jobbie. what ya think??

[kimi]

Kev,

if its true that i have two cats..is it going to cost me twice as much

being serious though if thats the case with phase 2, take me off the list as

it would'nt be worth it really would it.

my cars been on ramps loads of times but i've never looked

kimi :D

[clarky]

Kimi,

On the case with this ... speak soon

Clarky

[Envy Performance Ltd]

Hi Kimi, no need to worry. My car is a 2001 and had two cats. The idea of the Mod is to use one small Sports Cat to re-place both the stock cats and still pass the MOT which it did.

I would imagine you would get a nice increase in performance with the Sports Cat when using a Super Charger as those stock cats must really be causing a restriction. The more air you can flow the better the performance.

Kevin

Kev,

if its true that i have two cats..is it going to cost me twice as much

being serious though if thats the case with phase 2, take me off the list as

it would'nt be worth it really would it.

my cars been on ramps loads of times but i've never looked

kimi :D

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[clarky]

Would people please stop saying supercharger all the time ... its starting to get to me!

[Woody27]

lol jealous are you? :P imagine how i feel not even old enough to drive yet! i so cannot wait! i need a yaris more than food or beer at the moment!...

[kimi]

Hi Kimi, no need to worry. My car is a 2001 and had two cats. The idea of the Mod is to use one small Sports Cat to re-place both the stock cats and still pass the MOT which it did. 

I would imagine you would get a nice increase in performance with the Sports Cat when using a Super Charger as those stock cats must really be causing a restriction. The more air you can flow the better the performance.

Kevin

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Thanks KEV

As long as its ok on P2

Any idea of how long youre talking for this?

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Would people please stop saying supercharger all the time ... its starting to get to me!

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LOL its seeing all that power yesterday isnt it ...shame mark got lost

getting out the car park

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and WOODY27 welcome to the club :group-cuddles:

[clarky]

Ive never seen a Micra with a decat before!

[scionic]

Hi Kimi, no need to worry. My car is a 2001 and had two cats. The idea of the Mod is to use one small Sports Cat to re-place both the stock cats and still pass the MOT which it did. 

I would imagine you would get a nice increase in performance with the Sports Cat when using a Super Charger as those stock cats must really be causing a restriction. The more air you can flow the better the performance.

Kevin

That's not a hard and fast rule.

There is such a thing as too little backpressure you know. Hypothetically, a Yaris with 3 inch diameter headers and a straigh 4 inch pipe with no muffler or cat wouldn't make big power. It could quite possibly be less than stock and torque would suffer enormously.

[scionic]

Would people please stop saying supercharger all the time ... its starting to get to me!

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Why? Because superchargers actually do increase performance?

[clarky]

Actually that was humour ...

[Envy Performance Ltd]

I give up! Who mentioned 3 Inch Diameter Headers and 4 Inch straight through pipes, now your being stupid!

I don't sell anything I have not already tested on my car. Or if I do I always tell people I have not tried it yet and try and give an unbiased view point in to the possible benefits!

I am not quite sure what you are trying to get at but I am certainly not on here to make a fortune! In fact I will never get back the time and money I have invested in developing the sports cat system. The reason I started to look into it as lots of people wanted someone to take up the gauntlet and try it out, including me a fellow Yaris owner and Toyota enthusiast! :censor:

Kevin

That's not a hard and fast rule.

There is such a thing as too little backpressure you know. Hypothetically, a Yaris with 3 inch diameter headers and a straigh 4 inch pipe with no muffler or cat wouldn't make big power. It could quite possibly be less than stock and torque would suffer enormously.

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[earpl]

completely true kev.. its just finding what size is best :P

[yvvan]

There is such a thing as too little backpressure you know.

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Please stop assisting the "Backpressure Myth". Sigh. Backpressure is not required when an engine has been designed properly.

Yves.

[scionic]

There is such a thing as too little backpressure you know.

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Please stop assisting the "Backpressure Myth". Sigh. Backpressure is not required when an engine has been designed properly.

Yves.

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Anyone who thinks a "sports cat" gives a measurable increase in performance has ZERO credibility when it comes to performance knowledge, sorry.

There is performance, and then there is tinkering around and putting bits on your car that may or may not do anything of substance.

[seveer unaek]

A sports cat DOES give a measurable increase in performance. It's a highly restrictive device to our cars.... maybe not american cars, but on our cars it is highly restrictive due to very strict emissions laws. Therefore, removing it allows a better flow of gasses, therefore improving breating of the engine and allowing more performance. Ive seen the results on a Dyno and through personal experience.

Also, if they make no difference, then why are catalytic converters taken off every single vehicle used in motorsport, or why is a sport-cat used in 90% of manufacturers sports exhaust systems... ferrari, lambourghini and lotus come to mind.

[s0cks]

There is such a thing as too little backpressure you know.

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Please stop assisting the "Backpressure Myth". Sigh. Backpressure is not required when an engine has been designed properly.

Yves.

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Anyone who thinks a "sports cat" gives a measurable increase in performance has ZERO credibility when it comes to performance knowledge, sorry.

There is performance, and then there is tinkering around and putting bits on your car that may or may not do anything of substance.

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For once I'm not going to agree with you :) The Yaris has two cat's both of which you cannot see daylight through if held up to the sky because they are so frikkin tiny and restrictive. A sports cat is probably the MOST effective bolt on mod for the Yaris.

[admanirv]

There is such a thing as too little backpressure you know.

←

Please stop assisting the "Backpressure Myth". Sigh. Backpressure is not required when an engine has been designed properly.

Yves.

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Anyone who thinks a "sports cat" gives a measurable increase in performance has ZERO credibility when it comes to performance knowledge, sorry.

There is performance, and then there is tinkering around and putting bits on your car that may or may not do anything of substance.

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ive got to agree with nearly all points. Removing the standard cat will give a performance increase - it will yes but will be minsucle on car (yaris) of this power output, couple that with other mods it will help.

We've gotta remember were working with a 105bp car here, not a subaru 2.0 litre turbo with a high power output, the higher the power output more potential in gains from mods.

toyota likely put a lot of effort in getting good performance with a standard cat.

thats my 10pence anyways

[admanirv]

I also recommend this site, which give dyno results and notes on mods

http://www.importtuner.com/tech/0406it_ppscion/index.html

[s0cks]

I disagree. That website doesn't show a sports cat test?

Your exhaust is only as good as its most restrictive point. So making the CAT more free flow (bigger) will increase performance more than a manifold or backbox.

[admanirv]

I disagree. That website doesn't show a sports cat test?

Your exhaust is only as good as its most restrictive point. So making the CAT more free flow (bigger) will increase performance more than a manifold or backbox.

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true and the throat is tiny to begin with looking underneath car.

true true but it still filtering crap out from exhasut which means neligable icnrease. I was talking to a guy who did it on a subaru, he got about 3bhp dynoed. he got fed up and got a de cat that gave which gave 13bhp.

looking at a yaris this is a different case.

It just wont give much increases. we really need a dyno result!

[s0cks]

I disagree. That website doesn't show a sports cat test?

Your exhaust is only as good as its most restrictive point. So making the CAT more free flow (bigger) will increase performance more than a manifold or backbox.

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true and the throat is tiny to begin with looking underneath car.

true true but it still filtering crap out from exhasut which means neligable icnrease. I was talking to a guy who did it on a subaru, he got about 3bhp dynoed. he got fed up and got a de cat that gave which gave 13bhp.

looking at a yaris this is a different case.

It just wont give much increases. we really need a dyno result!

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To be honest it also depends a LOT on the quality of the sports cat. And remember the Yaris has two CAT' so if you replace 2 with one high-flow CAT then it'll be a lot better. There is also the o2 sensor situation, so if you do a full de-cat you get an engine check light, and I don't think anyone really knows what the ECU is doing to the car while this light is on (maybe decreasing performance - safe mode). The sports CAT doesn't suffer from this.

But in the end nothing but forced induction is gonna give big increase.

[admanirv]

I disagree. That website doesn't show a sports cat test?

Your exhaust is only as good as its most restrictive point. So making the CAT more free flow (bigger) will increase performance more than a manifold or backbox.

←

true and the throat is tiny to begin with looking underneath car.

true true but it still filtering crap out from exhasut which means neligable icnrease. I was talking to a guy who did it on a subaru, he got about 3bhp dynoed. he got fed up and got a de cat that gave which gave 13bhp.

looking at a yaris this is a different case.

It just wont give much increases. we really need a dyno result!

←

To be honest it also depends a LOT on the quality of the sports cat. And remember the Yaris has two CAT' so if you replace 2 with one high-flow CAT then it'll be a lot better. There is also the o2 sensor situation, so if you do a full de-cat you get an engine check light, and I don't think anyone really knows what the ECU is doing to the car while this light is on (maybe decreasing performance - safe mode). The sports CAT doesn't suffer from this.

But in the end nothing but forced induction is gonna give big increase.

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sure i dont want to but a downer on things, this what ive found out been told. And i dont want to put a bad light on sports cat and take away trade from "envy" - no this isnt a plug for kevin. this is just my opinion and share my knowledge with people :D

[Envy Performance Ltd]

I thought you had let this lie. If you don't want to mod your car then thats fare enough but let everybody else enjoy their hobby! Nobody is claiming a sport cat is going to give you big power. As somebody has already stated sports Cat is really the only option to avoid the check engine light coming on and it also allows you to pass the MOT (UK Emissions test) without having to keep replacing the orginal Cat pipes.

I am happy with my sports Cat, and if and when I put the car on the Dyno with the mods I have planned and I get 10 bhp increase I will be over the moon, thats nearly a 10% increase in power which I will be more than happy with.

Thanks

Kevin

Anyone who thinks a "sports cat" gives a measurable increase in performance has ZERO credibility when it comes to performance knowledge, sorry.

There is performance, and then there is tinkering around and putting bits on your car that may or may not do anything of substance.

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[yvvan]

There is such a thing as too little backpressure you know.

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Please stop assisting the "Backpressure Myth". Sigh. Backpressure is not required when an engine has been designed properly.

Yves.

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Anyone who thinks a "sports cat" gives a measurable increase in performance has ZERO credibility when it comes to performance knowledge, sorry.

There is performance, and then there is tinkering around and putting bits on your car that may or may not do anything of substance.

←

Where the hell in that quote do you see the words "sports cat"?

Learn first, talk later!

Yves.

EDIT - just to show this guy that it is the earth revolving around the sun and not the other way around:

When the exhaust valve opens, a positive pressure pulse travels down the primaries at the speed of sound, and when this reaches the primary/secondary junction, a negative pressure pulse is reflected. It is this reflected negative pressure pulse that assists in cylinder scavenging.

The overlap of a cam works by allowing the intake and exhaust valves to be open at the same time for a given period. Ideally, there is a low pressure pulse arriving at the exhaust valve (produced by length tuning of the manifold) as it is nearly closed, and this helps to suck more waste gas from the cylinder, and lower the cylinder pressure when the intake valve opens.

The problem is that a given overlap works best in a fairly small rpm range. Too high a rpm means that the overlap is not large enough, and thus not enough time for the exhaust to assist cylinder filling, too low a rpm means that the intake and exhaust valves are open at the same time for too long, such that there is little benefit from the exhaust, and also allows the fresh intake charge to be sucked out through the exhaust valve.

Ideally, you want the exhaust negative pulse to hit the exhaust valve before the intake valve opens, and a positive pulse to hit the exhaust valve just as the fresh intake charge reaches the exhaust valve, as this maximises the benefit of the low exhaust pressure pulse, and minimises intake charge loss.

For instance, if you have an engine that revs to say 5000rpm, and a cam with a 300deg duration, you have a problem. A cam like that is "meant" to work well at about 5500-6000rpm. If you never reach that rpm, then you will always lose fresh charge out through the exhaust, and thus you lose the benefit of the exhaust pressure depression.

Now, if you have a too large cam and you are losing fresh intake mixture out the exhaust, what can you do? You restrict the exhaust, in such way that you increase the pressure in the exhaust manifold, so that it is above the residual cylinder pressure, so that when the exhaust valve is open, the fresh charge will not escape as much past the exhaust valve. This will be both effective at increasing power and economy, as you are keeping more of the air/fuel where it should be.

In essence the long and the short of it is, if you have a free flowing exhaust, you should choose your cam carefully so that it matches your desired rpm range of operation. Or, if you have chosen too large a cam for your desired rpm range, fit a restrictive exhaust so that you keep more mixture in the cylinder.

In conclusion, the first will give better power and torque overall, and the second is a band-aid for a poor choice of cam.

So maybe it is not really a myth when it is based on poor engine design, but it sure is one for a good engine design.

Edited April 21, 2005 by Ken