Exhaust manifold design

[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.

Any comment will be appreciated, as I don't want to have a pooorly designed manifold, or one that won't be up to the task. Aiming for 450rwhp, and yes all the other things have/will be done to the engine before the turbo is in place.

See'ya:burnout:

[GTS-t VSPEC]

Come on guys, some of you must have custom designed manifolds. Just let me know what they were made of and whether your happy with the result.

See'ya:burnout:

[Steve]

EDIT: got off on a tangent, so I'll start again,

I have owned a car with mild steel headers, and it performed fine, weight less than stainless (can't be a bad thing) and had good heat transfer qualities (dont know how it would compare to stainless).

Haven't used stainless, but if you are going for ceramic coating, the advantages of stainless (look good and dont rust -are there any others?) will be completely negated I would think.

Steve

[GTS-t VSPEC]

Thanks for the reply Steve, I was beginning to think no-one had done this. I've heard that due to the heat transfer of the stainless it becomes brittle after prolonged use, heating and cooling. I believe that if you have it sand blasted to destress the stainless then it will perform better.

The mild steel sounds the go as it can withstand the high temperatures better, and once its ceramic coated should look quite nice.

Any opinion of tuned length vs not, it just cost more to have a custom tuned manifold and I'm not sure its worth the money.

See'ya :burnout:

[Steve]

I believe (perhaps very wrongly) that tuned length offers more than just a really nice note to the exhaust.

Having tuned lenght, means more equal flow and heat characteristic from the cylinders, reducing back pressure due to less turbulence = higher output with less stress on the motor and probably a quicker spool up. Is the price difference that much? Tuned length has been around for a long time.

[GTS-t VSPEC]

Steve,

I can appreciate the difference in theory, pretty much the same as any tuned length extractor, with the air arriving at the same point at different times so as not to create turbulance and back pressure.

I'm just wondering whether anyone has actually tried both ways and noticed any real difference. The price is probably only $200 more, but if it makes f#ck-all difference then I can spend that on getting the block ported.

I'm after about 450rwhp, I don't know if the tuned length is really for high horsepower engines or whether I will see the difference on a mild-tuned engine.

Thanks for the help.

See'ya:burnout:

[Steve]

450rwhp = over 600bhp, that's reasonably serious HP IMHO.

But if it means the difference between head port or not I can understand why you want to go the port. Are you getting your block deburred whilst she is apart?

[GTS-t VSPEC]

Steve,

I'm hopefully having anything that I can get done to it, as I don't really want to ever have the head off again. Forged pistons going in, overboring the cylinders, shotpeening the rods, balance the crank and port and polish the head. Yeah it does seem like alot of power, but I think it should still be quite responsive and street drivable.

I suppose if I'm going to the extent of maximising the airflow everywhere else I should't scrimp on the exhaust manifold. It's just that it all cost so much.

See'ya :burnout:

[Steve]

big $$$ = huge grin factor, I'm jealous and I'm sure I'm not the only one. But good on you for doing it, your car will be a beast:)

[GTS-t VSPEC]

Yeah but having a beast and knowing how to drive it are two different things, judging by my pathetic 13.9 at the drags last night. I feel I'm letting the car down, it probably deserves a better owner, but I do spend a shitload of money on her, even more then my ex-girlfriend. The car doesn't bitch as much either.

See'ya:burnout:

[Steve]

Don't worry about letting the car down, as long as you're having a good time that is all that really matters. Plus there is the added bonus that with 450 neddies going onto the deck, some people may be thinking you are just out there to get the jump on the burnout demos - lol

[Guest GT N1K]

to add to this thread -

I have a Garret T66 turbo mounted onto a custom exhaust manifold. this is in mild steel then HPC. It achieves the necessary function without any problems of cracking or overheating. I would have to say that i haven't had a stainless steel manifold made, but 4 me it was a cheaper alternative. the price can be relativeli cheap depending on who u commision to construct the manifold. I'll enquire 4 u.

N1K

[GTS-t VSPEC]

GT N1K,

I'm definately thinking of the mild steel over the stainless, I know a few race cars with stainless and there's have cracked. I will also pay that bit extra for the tuned length, even if I'm still unsure about the possible benefits.

Thanks for the help, how is your car going, has it been dynoed yet?

See'ya:burnout:

[slayer]

Where in Perth can you get the ceramic coating done? I was planning on getting my dump pipe HPC coated (via eastern states) but if ceramic coating is a local offering I would be interested in that.

Sounds like your car is an absolute friggen monster... would love to see it go through its paces on the track

Conrad

[GTS-t VSPEC]

Slayer,

Will be a monster, its not there yet, but over the Christmas/New Year quite a bit of the internal work will be done.

I will find out about the ceramic coating, hopefully tommorow, and then I'll let everyone know.

See'ya:burnout:

[MrMayhem]

I run stainless extractors and 1 and 6 cracked from the head fange and had to be re-tigged...

If your going to throw a fortune at it .... do whats "theoretically" right and blow the $200 on the tuned length if you think everyone else who make performance manifold are wrong ... then dont

but whatever you do set the external gate up in an appropriate place, clearances become and issue

[Guest GT N1K]

I couldnt have it dynoed yet. They couldn't fit it on the dyno at speedworks as it was too wide to fit the Dyno pack onto my hubs. So now i gotta wait til 2morow 2 c if any other dynos can fit my car without hitting the body skirts. & rising the car is out of the question as its at its max height. The anticipation is killing me!!

N1K

[GTS-t VSPEC]

Shit N1K, the anticipation is killing me too, you must be ready to have a heart attack. I'm not surprised that your having difficulty with such a wide body kit. It does seem sad that the dyno doesn't take into consideration for cars with a bit of bulk to them.

Hope you get it sorted soon.

MrMayham,

I will be get it tuned length, and thats the reason I didn't want stainless, cause they tend to crack.

See'ya:burnout:

[Neo]

Hey,

Have you seen this place look under parts&accesories-skylines-exhaust. Just if u wanted some more ideas just may be of interest, dont know.:confused

:http://www.uniqueautosports.com/

Goodluck

Jason

[Guest GT N1K]

Well, im settling for a road tune until february when extensions arrive for the Dyno packs to fit my car.. *sigh*...well, let u kno how tat goes this week.

N1K