Exhaust manifold design

[GTS-t VSPEC]

N1K,

A road tune with the number of cops on the road? I hope you've got a good radar detector.

It sucks that you'll have to wait so long, as without a proper dyno tune then it wouldn't be advisable to really push the engine. Let us know the results anyway, it should be pretty impressive by now.

Good luck.

See'ya:burnout:

[GTS-t VSPEC]

Neo,

The exhaust manifold at Unique Auto Sports is exactly what I'll be having made, tuned length mild steel for a GT30 with external wastegate. The custom job will be many hundreds of dollars cheaper, although there's does look very nice.

Thanks for the link, it's good to see that some aussie companies are designing stuff to compete with the jap brands.

See'ya:burnout:

[rev210]

Originally posted by GTS-t VSPEC

Hi Guys,

I've got someone about to start on designing my exhaust manifold for my R33 GTS-t, which willl be housing a GT30 series turbo. I was after some info on what people think the best design is in terms of materials and length of the runners.

Currently the idea is to have it made from mild steel, as I hear alot of people with the stainless steel ones have cracking issues. I'm not sure if having them tuned length really makes alot of difference or not, any suggestions, preferably from first hand experience. I was also planning on having it ceramic coated, as we can now get it done here in Perth, has anyone done this and compared it to heat wrap etc.

See'ya:burnout:

1) Stainless steel of decent guage. leading to cracks. If you insulate the pipe well it will prevent it from having 'hot spots' that are the real cause of problems, mild steel OR stainless. I've seen both crack with exhaust tape within months of use, due only to incorrect uneven wrapping and lack of surface preparation. With ceramic coating you don't have such problems.

2)Shortish runners. Because aftermarket runners are always going to be longer than the stock manifold. Longer pimary pipes will shift the power band and torque up the rev range (as a rule of thumb).

3) Tuned length? Sure, you can try. Basically the length of each runner is made along the lines of measuring the pulse width of the exhaust(kinda like a wavelength). Something more accuratley done by putting oil or something on straight primary pipes and seeing where they get black lines, or using an optical pyrometer or something .Well I'm not entirely sure how its done these days but thats the theory. Something that requires someone to do R&D.

4) ceramic coating is very good. Looks nice, lasts. Heat wrap done right will insulate better and slightly outperform ceramic coating in the dump pipe area. For the turbo manifold ceramic coating is a better move, its just a complete SOB to wrap (the dump pipe is hard enough). For the dump pipe you could ceramic coat it and then get the thermotec turbo kit (includes a turbine blanket).

[Merli]

Have you thought about just buying a Japanese exhaust manifold?

These are available brands in my HyperREV:

Sunyou - 128,000 Yen

Essential - 168,000 Yen

EXIT - 220,000 - 240000 Yen

Bullet - 105,000 Yen

APEXi - 198,000 Yen

Rave Factory - 158,000 Yen

Meiku - 130,000 Yen

Prime Garage - 180,000 Yen

HRD - 128,000 Yen

Climax - 148,000 Yen

HKS - 198,000 Yen (258,000 Yen with wastegate)

[Joe]

Garrett GT30 uses the T3 Flange so they will bolt on the factory manifold, but fitting it & clearing the space is another question.

I do not know squat about making manifolds, but most japanese ones are made in cast iron & mild steal & are far more well designed then a exhaust shop.

I would not put the turbo top-mounted, heat transfer will go to the intercooler pipes etc, Bottom mount is the best idea as it will get abit of air once driving.

Once the manifold is created, the GT30 is an external wastegate setup, so you would need to created a new dump pipe, with a scream pipe for the wastegate, thats the easy part.

Hope this gives abit of an idea of what your getting into :bahaha:

[MrMayhem]

havent seen too many jap ones in mild early ones are cast iron and pretty much live forever new flashy tuned length are mainly stainless. heavy steampipe mild might be the go might need to brace the weight to something

screamer pipe, anti social banshee wail, love it

[giz01]

heavy wall mild steel or so i am told is good! 304 stainless is crap as it cracks apparently, 321 stainless is the way to go if you want to use it! steam pipe is the best or so i'm told think its cast from memory & u can buy it in bends or something, have seen 3mm thickness & 4mm thickness & have been told not necessary to hpc it, but if it was mine i would definitely hpc extreme coat it (black stuff)!

[Merli]

Originally posted by Joe

I do not know squat about making manifolds, but most japanese ones are made in cast iron & mild steal & are far more well designed then a exhaust shop.

G'day Joe... Not saying you're wrong, but all the photos of the manifolds in my HyperREV are all Stainless Steel. And my HKS Exhaust Manifold is made out of Stainless Steel. Perhaps the earlier made ones were made from mild steel/cast iron? It seems to me all the ones on the market today are made of Stainless Steel.

And yeah, the Japanese exhaust manifolds are a work of art. You could pay a local exhaust workshop $4000, and they wouldn't come anywhere near to the quality of finish, or design of these japanese manifolds.

Seriously GTS-t VSPEC, spend 5 minutes, turning an HKS Stainless Steel Exhaust Manifold over in your hands, and you'll understand exactly what I'm saying.

[giz01]

C.E.S in brisbane manifolds are every bit as good as the japanese in quality, except trevor prefers to use either heavy wall mild steel or 321 ss steam pipe both of which are MUCH better than the 304 stainless alot of jap manifolds are made from!

304 is ok for na headers but not turbo manifolds as it cracks more readily as it does not like the extreme heat!

[Steve]

Saw a HKS dump pipe. It was a million bucks on the outside, but inside was another matter, wasn't too impressed.

[rev210]

Originally posted by giz01

C.E.S in brisbane manifolds are every bit as good as the japanese in quality, except trevor prefers to use either heavy wall mild steel or 321 ss steam pipe both of which are MUCH better than the 304 stainless alot of jap manifolds are made from!

304 is ok for na headers but not turbo manifolds as it cracks more readily as it does not like the extreme heat!

Stainless 304 is fine for turbo manifolds and if welded properly to begin with will out last mild steel. Cracking is because of hot spots and the kind of corrosion they promote. I have known stainless, steam pipe and mild steel exhausts to crack because of this. Steam pipe is great stuff all the same and mild steel is great for the price.

Fix the hot spot corrosion issue (ceramic coat) and you don't have a problem what ever way you look at it.

Has C.E.S had a chance to 'pulse tune' the correct length of the headers on RB25DET's? If so how did they do it?

[GTS-t VSPEC]

Shit guys, this started off as a really slow thread, but it is starting to build some momentum. I'll try and reply to everyones posts.

Rev210,

Thanks for all of the advice, I always thought that ceramic coating was superior to the thermo wraps, there was a test in HPI/Zoom where they were able to touch the exhaust manifold after use. I haven't tried any of them yet, but the clean look of the ceramic coating is appealing.

Merli,

I agree that the Japanese brand do look a million dollars, and the stainless steel does appeal, but at between $2000-$3000 I think this is one area where I can save significant money without loss of performance. I have seen the HKS manifold, and appreciate what your saying, but the cost is at least double of a custom job. Do you know what stainless they use, as I have heard of so many problems with stainless cracking.

Joe,

I didn't think the GT30 would bolt onto the existing exhaust manifold, but either way, with an external wastegate and the relatively restrictive design of the factory unit it has to go.

Giz01,

Thanks for the advice. I am planning on useing the heavy wall mild steal, used for steam pipes. It has a greater capacity to distribute heat without cracking, and as it can be bought in sections then it is relatively easy to create a tuned length manifold.

Steve,

I'm making sure that the inside of the manifold is at least as good as the outside, as this is where the gains are made and lost, not in the looks. Thanks for the opinion.

Everyone,

Thanks for all of the suggestions and comments, please keep them coming and share ideas as to what you think works best etc.

See'ya:burnout:

[rev210]

Originally posted by GTS-t VSPEC

Rev210,

Thanks for all of the advice, I always thought that ceramic coating was superior to the thermo wraps, there was a test in HPI/Zoom where they were able to touch the exhaust manifold after use. I haven't tried any of them yet, but the clean look of the ceramic coating is appealing.

Yes, thermo wrap tends to be a little better at insulating heat than ceramic coating (in general). It does depend on the thickness/type of the ceramic coating. Some companies offer different options. At any rate both are excellent and there is nothing stopping you from doing both. The ceramic coating is usually less than $200 from a very faulty memory

[GTS-t VSPEC]

Rev210,

I was considering doing the turbo exhaust housing, exhaust manifold and front pipe with the ceramic coating. I hope that it is around $200 each, as that will make it realtively good value for money.

Do you think that these coating/wrapping techniques have any benefits in terms of spooling of the turbo, i.e. hotter exhaust gases flow faster and spool the turbo quicker?

See'ya:burnout:

[rev210]

Originally posted by GTS-t VSPEC

Rev210,

I was considering doing the turbo exhaust housing, exhaust manifold and front pipe with the ceramic coating. I hope that it is around $200 each, as that will make it realtively good value for money.  

Do you think that these coating/wrapping techniques have any benefits in terms of spooling of the turbo, i.e. hotter exhaust gases flow faster and spool the turbo quicker?

See'ya:burnout:

$200 will probably only do the exhaust manifold. $100 for the dump pipe / front pipe. I'm just guessing tho'.

Spooling the turbo? Yes indeed. Thats the main reason I did mine. The more you do to help the turbo spool the less time it takes to accellerate your car. Thats also why I've done the flywheel.

[GTS-t VSPEC]

Rev210,

So did you notice the difference between the when you had heatwrap on and off?

How have you found the new flywheel? Notice the difference in acceleration? Have you found any vibrations caused by the lightened flywheel, with the harmonic balancer not being adjusted to the different weight?

Sorry about all the questions.

See'ya:burnout:

[rev210]

Yes you notice the difference, slightly quicker spool and better vacume at cruise on warm days also.

The lightflywheel is fab! Accelleration is much improved as is shifting.No vibration, I plan to ditch the stock front pulley for a lighter underdriven one some time also. Save another kilo or so there too. UAS flogs them now.

[Merli]

Originally posted by GTS-t VSPEC

I agree that the Japanese brand do look a million dollars, and the stainless steel does appeal, but at between $2000-$3000 I think this is one area where I can save significant money without loss of performance. I have seen the HKS manifold, and appreciate what your saying, but the cost is at least double of a custom job. Do you know what stainless they use, as I have heard of so many problems with stainless cracking.

As Rev210 said, cracking is due to hot spots, due to poor exhaust manifold design. I have never seen a Japanese-designed manifold crack, only locally made Stainless steel manifolds... Any metal can crack if it is poorly designed.

The Japanese spend months trialing different designs and have their exhaust manifolds on flow benches, trying to take advantage of cylinder pulsing and using near equal-length piping...

What happens when you get a locally made exhaust manifold? They will get their flange, and put it on your head. Then they'll start spot welding some bends on and slowly build up each runner until they all converge in the same spot, where they weld them all together and chuck a flange on it, where your turbo will sit. There is no flow testing done... I'd bet my puppy dog that they didn't research how the gas pulsing would effect flow properties or extraction characterisitcs of the manifold, among with other things I wouldn't have a clue about when designing an exhaust manifold.

It's true that they're much more expensive than locally made ones, but you know as well as I do, that the Japanese products are second to none, and no "custom made exhaust manifold from Cabramatta Exhaust Specialists" will ever match the Japanese design or quality.

Having said that, there's absolutely nothing stopping your local exhaust shop fabricating a decent exhaust manifold for you... You just have to get the point across that you're not after a slap, bang job... You want it done PROPERLY. Best way to ensure you don't get a dodgy one made up is if you have a mate in the exhaust business

You seem to be spending a whole heap of moolah on your car, so I just thought I'd suggest what no-one else had in this thread...

[GTS-t VSPEC]

Merli,

I appreciate the concern, and fully understand that there is very little done on the research front in Australia, and therefore trying to compare a Japanese manifold to a local exhaust company is like chalk and cheese.

The guy I have building mine has been producing 500+hp car for 15years, and I'd agree that most exhaust places have very little clue what is required, I feel that this guy will produce a manifold that is very functinal and comparable to the Japanese brands.

As I am having the head ported and polished, I will also get the inlet and exhaust manifold flow tested, to ensure that there is no restriction on airflow in any part of the system, as if one bit lets the side down then it was a waste of money. I'm not trying to be cheap here, if I thought that what I could get here wasn't as good then I would bite the bullet and purchase the Jap brand.

I won't accept the manifold if I don't believe that it will produce the goods. I will post pictures of the manifold once it is completed, and hopefully it will live up to my expectations.

See'ya:burnout:

[rev210]

Originally posted by GTS-t VSPEC

I appreciate the concern, and fully understand that there is very little done on the research front in Australia, and therefore trying to compare a Japanese manifold to a local exhaust company is like chalk and cheese.

The guy I have building mine has been producing 500+hp car for 15years, and I'd agree that most exhaust places have very little clue what is required, I feel that this guy will produce a manifold that is very functinal and comparable to the Japanese brands.

As long as the guy can do the 'tuned length' properly there won't be a problem, it will be sweet mate:D

I'd just ask him how he determines the length of each runner, to make sure he's on the level if he tells you its a 'tuned length' unit.