exhaust header

[asinn]

had tdi developed a exhaust header system for is200 yet?

[Jimmy Ten Toes]

I asked Mark about these recently and they hadn't sorted out pricing yet

[asinn]

tdi, hows the header development goin?

when will it be launch

[tdiplc]

Hello

You can expect an announcement sometime this week.

The new manifold is quite a complex design, I hope it will be worth the wait!

Mark :)

[TRD328]

yeah would love to see some performance mod for the IS200 (1gfe).

Imagine the untapped market out there.

Asia region

Europe

Australia.

Many IS200 owners are left in the cold due to the lack of support for the 1gfe.

By making a performance exhaust system ie headers->muffler you sure would be a pioneer!

[Jimmy Ten Toes]

Mark,

What performance GAIN can we expect from the header?

If the price is right I'm in.

[Jimmy Ten Toes]

Originally posted by GRiM

Originally posted by Jimmy Ten Toes

............ What performance hit can we expect from the header?

Surely you mean performance gain Tim, not performance hit!!

Hit, what you on about. Your eyes must be playing tricks on you mate. Look again:lol:

[superchargedmorph]

Hi, all

will a free flowing exhaust manifold actually make any difference, I mean the way to increase power is to get a bigger bang, then get the waste gas out. If our cars even the supercharged ones are removing the waste gases efficiently enough then surly it will make no difference. I thought it only improved things on Turbo Charged cars as the exhaust gases are used. So the only way for power for us is supercharger, then if a further upgrade to increase fuelling then and only then will a new manifold help.

I am no mechanic, just what I was wondering, please help me out on this.

[Jimmy Ten Toes]

I am no mechanic either, but from what I understand with the current standard back box, CAT, pre cats, manifold etc. you get a certain amount of back pressure which reduces the engines performance, the same applies for the intake, its too retrictive.

The supercharger will provide the biggest performance boost in one go, but getting the air in correctly and then getting it out efficiently, then getting it chipped will also provide a nice increase.

Please correct me if I'm wrong as I'll be wasting my money!

[superchargedmorph]

Hi Jimmy ten toes, who is to say that our cars are not getting rid of gases efficiently, I am also looking for the correct answer,so I dont waste any money.

[Jimmy Ten Toes]

Any car with a CAT is immediately retricting the exit gases quite alot. The blokes at Topgear said 4-5 % power increase can be gained by fitting a hi-flow sports cat alone and more with the pre-cats cleared. Getting a de-cat will improve performance even more but you will have to stick a cat back in for MOT's etc.

I spoke to a separate mechanic mate of mine this weekend who is going to clear my pre-cats. He also said that they quite restrictive and knocking them out will give you a noticeable increase.

Even with just the sports cat and back box, I can notice the difference. But its no good having a straight through back box if the restrictions and back pressure are happening at another point. Thats the way I'm approaching it anyway.;)

[TonyGoose]

JTT - good luck to your mate 'knocking out' the pre-cats.

One might be do-able but the other is quite inaccessible - too far up/down bendy pipes to get to.

Doubt you can do the job properly without cutting them open - unless they're already knackered.

Morph - until someone mentioned it and i looked under the covers myself,

i hadn't realised how puny the pipework is off the head .... must be restrictive.

I gather (from Mat + Mark) that temps in there can be 900deg or so which isn't good ...

except for warming the pre-cats to operating temp quickly.

Manifold / header design can be very complex ...

Factors such as scavengeing (using gases from one exhaust pulse to help suck out those from the next),

valve overlap, tube diameter and merge points etc all play a part.

I think i'm right in saying it's more critical on naturally aspirated motors than turbo'd ...

the latter you generally want to get gases away asap.

Supercharged i'm not so sure - in theory i can see fors and againsts in both approaches.

Mark - how about a swingometer for supercharged manifold / header design ...

swing towards NA or Turbo'd ? On balance, i'd guess the NA approach.

Oh and I hope these new pipes have fixing points for the stock covers ...

Let's keep things looking neat and tidy under there :smilegrin:

[superchargedmorph]

On some research I found, it stated that a certain amount of back is needed, if you remove the pre cats you create an open void, and take longer to fill with the gases slowing the car down at the low end of the scale ie acceleration.

Just trying to find out if a less restrictive header/removal of pre cats will really help.

[asinn]

whats precat?

is that the 2 cat look alike things straight after the extractors?

because i went to a custom make extractors workshop they told me those things r collectors......... i don't know what that is........ but they said if make a custom make header its good to remove them.

[Jimmy Ten Toes]

Originally posted by superchargedmorph

On some research I found, it stated that a certain amount of back is needed, if you remove the pre cats you create an open void, and take longer to fill with the gases slowing the car down at the low end of the scale ie acceleration.

Just trying to find out if a less restrictive header/removal of pre cats will really help.

Where did you here that mate?

[Jimmy Ten Toes]

Originally posted by asinn

whats precat?

is that the 2 cat look alike things straight after the extractors?

because i went to a custom make extractors workshop they told me those things r collectors......... i don't know what that is........ but they said if make a custom make header its good to remove them.

Thats the boys

[superchargedmorph]

Having a short wheelbase is usually an advantage, take the CRX for example, but in the GTi's case it became sort of a disadvantage, especially when it came to exhaust design. Even though, theoretically, the exhaust piping is supposed to be short due to wheelbase, the design of the GTi underpinnings creates sort a small maze for exhaust gases to flow through. Unlike other cars there is no long downpipe to the cat which is great, but once we get to the rear of the car we encounter the problems of design. Instead of the long space after the backseat to the bumper, the GTi exhast has to curve right to avoid the spare tire well then curve up and through the suspension pieces. These are two very tight curves within a few inches apart which might create more unnecessary backpressure if the exhaust pipe is done wrong. Depending upon how well you know the guy building your exhaust you should always opt for the mandrel bent pipes. All the premade systems are mandel bent so don't worry about it.

The other problem that you might have is if you use too big a diameter pipe or a wrong size muffler. If the pipe is to big (3.5") it might obstruct the suspension pieces especially if you're running a lowered suspension with small wheels. If the muffler pan is too big what most people do is angle it down or push it back. This could place the muffler in the way of the rear control arm if it starts to sag. It could happen to you.

If you're running a straight pipe run the exit in front of the rear wheels Mustang GT style, most people can't live with that level of noise.

Pre-made Systems:

Janspeed of England makes a wonderful exhaust system for the GTI. Twin tipped in full black it eliminates the catalytic coverter as runs from the downpipe back. It fits perfectly, looks great, and sounds just as good.

Genie Exhaust Systems, available stateside, makes one as well. This one is full stainless steel and runs from the cat back. It fits great, looks awsome, and has a very aggresive exhaust note. Worth the money.

Stromung. Looks good. It possibly fits perfect due to Stromung's excellent reputation for quality, but I've never heard one.

Do-It-Yourself:

Your first major obstacle is that none of the universal mufflers fit perfectly. It will either point down or stick a bit out making it look like you did it yourself. This is due to the lack of space. Trying to push the muffler back will interfere with the right rear suspension, so watch out. I am presently running the 'ever popular' UltraFlo which I regret ever purchasing. I just don't like the sound. Thankfully the guys at Brullen are working on an muffler that will fit cars like mine. I'll be there when they first go on sale.

Pipe Diameter:-

1.5" is stock.

1.78" is what Jackson Racing used for a 8hp gain.

2" is recommended for maximum gains with headers.

2.25" causes the torque band to shift to the mid/top [read top speed 130mph]

2.5" is what you should forget about unless you're running boost.

THE LESSON. After going through all these pipe changes I found that you must be very careful when it comes to exhausts for the Swift. They could end up changing the characteristics of the torque curve instead of enhancing it, and this leads to a further problem created by the gearing. Bottomline: TOO MUCH FLOW EQUALS NO GO!

Exhaust Page 2

TO CAT OR NOT TO CAT... THAT IS THE QUESTION

Okay you've heard the explainations, and the bench racing tales about removing your catalytic converter. Is is worth it to you the Swift GTi owner? Hard to say, but here goes. The catalytic convertor is simply a can connected to your exhaust, located generally after the downpipe to reduce nasty emission gases. It contains a sort of ceramic substance which reacts with the hot exhaust gases to produce a cleaner emission. Now since you have basic idea of how it works lets go through the truth of it.

When cats were first introduced manufacturers had no idea of how to tune engines to produce cleaner exhaust. So their cars ended up with sapped performance and they blamed it on the restrictive exhaust systems and catalytic convertors. Now it is true that they sap power, but how much power and is it worth it removing the thing.

My personal experience tells me no, but in certain situations yes. Everyone wants a free flowing exhaust, but remember the TOO MUCH FLOW EQUALS NO GO tag line. The semi-restrictiveness of the cat keeps up some of the back pressure needed to fill the engine at low RPMS. Removing it while pairing it to a too large exhaust pipe diameter will affect your performance in a more negative than positive way.

Still Rory, how does this affect my sweet little GTi? You all ask. Another thing that affects how a cat saps power is its shape, and this is where it relates to the car. The GTi has two different model convertors. I'm not sure if this varies by country, but it varies according to model year. The 89-91 model years have a long square shaped cat while the 92-present have a round pre-silencer like design.

There are two ways to remove your cat. In America, where it is illegal to drive without a catalytic convertor, the most common practice is gutting. You take your cat, beat it until the ceramic material inside shatters and falls out, thereby halting its clogging effect and retaining its appearance for the fuz. This works great till you add your exhaust to an older model GTi with its retangular cat.

I could all give you physics lessons but check the diagram below for the results.

(Was Catdia.gif, but it's gone...)

Exhaust gases from the engine come speeding out into the gutted catalytic convertor. This slows down the flow as the gasses try to fill the now empty area. Now you end up with less bottom end performance as the slow speed of the gases at low RPMS cannot fill the cat fast enough to speed exit. Due to this change in pressure you will also develop flat spots.

Now that you know what will happen the same does not apply to the round convertors on later models as it just becomes a piece of pipe.

The Janspeed exhaust system had no cat and starts from the downpipe back. The technician I spoke to said that the cat is responsible for a 4 - 8hp loss depending up the vehicle. But note the diameter of their exhaust system is 2" which retains the necessary back pressure for naturally aspirated motors.

Again I cannot stress enough that the Gti, while having a great little engine, is limited by its displacement when it comes to pipe diameter for your exhaust. Please choose wisely.

Next:-Turbo Time.

Exhaust Turbo

The major problem for Turbo-charged cars is back pressure, or more specifically too much of it. In a naturally-aspirated vehicle air pressure is what fills the cylinders, where as a turbo compresses air and forces it into the engine. This compressed air must be evacuated as quickly as possible to make way for more air before the pressure builds up beyond the capacity of the engine. This evacuation process must however be optimized for the boost level being run on that particular engine. If the air leaves the engine too quickly boost pressure falls negating the effects of having a turbo in the first place. A good sign of this is slow spool-up.

The exhuast system for a turbo starts at its exit side. The piece between the turbo and the catalytic convertor is called the downpipe. It should be the same diameter as the rest of the exhuast system for best performance. Turbos and catalytic convertors are not friends, but not for the reasons you think. Since turbos scavenge exiting exhaust flow it ends up absorbing a lot of the heat that cats need to achieve operating temperature. On the other side turbos running high boost for long periods of time generate heat which is passed to the convertor through piping. This excess heat can damage the catalytic convertor. So be prepared to have a bypass for the dragstrip.

From the cat back the exhaust pipe can be 3 inches or over as per your PSI level, but another important thing is the pipe itself. It must contain as little restriction as possible. In this case a pre-made turbo exhaust system is not available for the GTi so you'll have to have one fabricated. If so, ask if the shop uses a crush or mandrel bend machine. Unless desperate go for the shop with the mandrel system. Remember, the Swift exhaust system twists through the rear right suspension pieces creating possible sections for restriction of exhaust flow.

Finally any turbo muffler that fits will do. Not the silly ones with turbo in their name, but those for turbo applications. You can tell these by their straight through design. I cannot stress enough that you make sure it fits and doesn't touch the body work as the heat might melt the plastic trimmings or peel the paint.

Exhaust

When your car isn't a popular make or isn't being made anymore, it is very hard to find a proper exhaust system for it. When I say exhaust I mean from the exhaust manifold back.

This is very apparent in the lack of an exhaust manifold with a flex joint for the GTi. I'm not sure if I'm the only one with this problem, but my header has been slipping off occasionally no matter how much I tighten it. The Japanese rally exhaust manifold has a flex joint to deal with the massive torque of a Swift GTi in rally trim and the harsh demands of rallying, but it is a bit too free flowing for street trim, not to mention pricey. In a powerful front wheel drive car the torque causes the engine to shake which is then transfered down among through various attatchments like the exhaust manifold. The vibrations can actually shake the header loose from where it connects to the rest of the exhaust system, which is the problem that I've been having. Has anyone else seen this, or is it that my car is just that powerful?

Now I know I said that no aftermarket exhaust will fit perfectly. Maybe I was exaggerating a bit, or not being clear, but let me correct that statement. No exhaust will fit properly because of their tip, with the exception of the Brullen. You can always find a muffler that meets the dimensions of the GTi, but the tip will cause distortion in the installation. The tips are generally too long, too big, or both. When they are too long they stick out creating a most unfinished look on even the nicest looking car. When they are too big, you must angle the tip down defeating the entire purpose of having a big tip. So if you're like me I'm offering the following exhaust choices.

Go with a premade. They look nicer and take the guess work out of their capabilities due to the fact they are made to certain tuning standards. Sebring Exhausts has finally started to bring to the states their massive European line of exhausts which include the nicest GTi exhaust you'll ever see or hear. The Genie unit is full stainless steel giving it a sweet appearance, but it sounds like a typical Japanese exhaust. Not necessarily a bad thing. I have still to see the Stromung exhaust, but since they use a basic look for all it should be hot.

If you want to go self made then I suggest DTM tips. Either buy the raw box and add the tips or buy the complete box. This solves the sticking out problem as the tips angle upward and look real cool. Nopi sells the tips and a cheap DTM exhaust muffler, but for those of you with the expensive tastes 5Zigen has one with their logo laser etched on the tips. Check your local performance parts store for it.

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[Monster-Mat]

without stiring this up more and not wanting to sound like im licking TTE's bollocks........but im sure that the chief tech there........who you have spoke to tony........and TTE in general...and TDI know what there talking about

and remeber i didnt have a choice,mine had melted......im sure the fact that i feel a difference.....means there must be some added benifit.....my 2p worth:info:

[superchargedmorph]

The point is to show that removing our pre cats may not be as conducive to a power increase for acceleration as we all think, that fact that the report is on a different model is of no importance, pun intended, if it is too long for you dont read it, I suggest that if I wish to discuss the issue then Iwill, you see my view is to try and help others and if I find information that may do this then I will. This report is backed up by information I have been given from 2 other tuners, they may wrong but they are not trying to sell me something.

I have just heard back from tdi, and they have said that they cannot confirm that removing the pre cats will help, but a less restrictive header should be of help.

This is good as long is it does not steal low end power.

[Monster-Mat]

also the design of headers has a direct on performance,thats why...as in my race car i had a 4-1 header as for my ex-max demo rover that had 4-2-1 headers for low down and mid whereas the race car needs mid and top end...........

there is no simple exhaust design its a complex and specialist business.

[Monster-Mat]

i am of course discussing all this in relation to the car having a supercharger fitted

[superchargedmorph]

Matt I agree with you for your car were you can run at high speeds, and you are getting better top end performance, I am no mechanic or tuner, you are and I respect the knowledge you have, I am just wondering if I will lose out on my precious acceleration( its all I can play with in UK), so I am just trying to find anything that relates to this and be my informative self. Any input you have for me on what I want (without nos)is well worth making you lots of alcohol laced melons:lol:

Cheers DUDE, ps chris is in love :Dthe female population is safe.

[Jimmy Ten Toes]

This is just what the forum should be about, lots of input and experiences, enabling people to weigh up the options before spending their hard earned.

But..............I am now confused as to what to do. Maybe I should leave the pre-cats as is and just get the air intake and Unichip done...........or should I?

:?::?:

[dark_is200]

i think that removing the pre-cats is important for anyone with a supercharger (see Matt's post http://teamlexus.co.uk/forums/viewthread.php?tid=980) to avoid some of the long term problems, it's a good bonus that it brings a power improvement.

for a regular is200 it will probably be a case of experimentation to see whether the removal has significant benefits.

[Jimmy Ten Toes]

I can get them emptied for next to nothing (a few beers) so its not the price of getting it done, its just that I want to make sure it doesn't make performance worse.