1g Exhaust Manifold Design

[Gst18]

Im planning on having a 1st gen manifold made by a friend who just finished making his for a b16.
I already have the exhuast flange.
I need some more information on the type of material to be used.
I was thinking about t304 Stainless Steel. I know T321 is much more expensive and slightly stronger in strength.
For those who have made custome manifolds before...
what ID size did you guy use?
What type of material?
What type of design?
I already know i want it equal length.

Im just looking at what different ways there are to build this manifold and what might be the best.

Thanks for any inputs

 

[Lunch_Box]

I have made 2; both used 1 7/8" 304 SS tube with a .065 wall thickness. That is a pretty thin wall thickness so I braced both of them. As for the design just look on the internet and come up with something or just make something on your own.

 

[Gst18]

Did you see/ feel any horsepower gains?
I was doing some research on full race motorsports website and was looking at a few of their exhaust manifold designs.

Im thinking about running a divided housing with 2 wastegates for a few seperate reasons. I read that it smooths out flow and also doesnt interfere with exhaust pulsations.
I also saw a dyno run on their website that changing from a log style manifold to ram style with equal length runners will give about 50whp at 10 psi on that setup. Now doing something like that with divided runners should be even better right?

Im just gonna test it out since i have some extra time on my hands.

 

[awdrst]

You really only use divided runner setups on turbos that have divided housings. Mitsu doesn't offer that as far as i know. If you are putting on a t3 or a t4 you can get that option. As far as material I use 1.5" sch 10 stainless steel. Another option is sch 40 stainless steel. You can get them from http://www.acestainless.com or from McMaster Carr. It's cheaper than using mild steel this way. Equal length is great if you can make it that way if not just get as close as possible. If you need to get a collector already made you can use http://www.bmcrace.com/ or just make your own.

 

[Gst18]

thanks for the info but im going to buy my tubing from mcmastercarr and gonna run a divided setup on a divided turbo. I wasnt planning on running a divided manifold with out a divided turbo.

Thanks for the replies

 

[WatchItExplode]

You really only use divided runner setups on turbos that have divided housings. Mitsu doesn't offer that as far as i know.

Actually they do. Evo 8's use a twin scroll 16g. I have heard of at least one person successfully putting an Evo turbo on a DSM using a custom built manifold. I believe the STI uses a twin scroll turbo too, but I think it would be shaped kind of funky for a DSM.

By the way, here's a new product I saw in Turbo magazine that might help you design your manifold: http://www.icengineworks.com/

 

[Gst18]

Someone told me that I should pair 1-3 into one scroll and 2-4 into the other. I've also read elsewhere that I should pair the runners so the pulses are as far away (in crank degrees) as possible... so 1-4, 2-3 are paired.

If #1 is on its exhaust stroke which cylinder is on the intake stroke? It would make sense that those 2 cylinders should not be paired so the exhaust pulse does not interfere with the overlap of the other cylinders intake stroke.

firing order is 3214

 

[WatchItExplode]

304 stainless is pretty standard for good exhaust manifolds, that would be a good choice. Another option would be mild steel if you're cutting corners on cost, but it corrodes a lot easier so you would want to get something like an industrial chrome plating on it.

The inner diameter should basically just match the exhaust ports, but if you are stuck trying to decide between a couple different sizes, always opt for the smaller which will increase exhaust gas velocity. Length of the runners should be equal length as you said, and should be as short as possible to avoid loss of heat (more surface area=more heat loss). Obviously avoid sharp angles and such, both for flow and to avoid hot spots.

For the wastegate section(s), avoid a 90 degree angle like in the picture above. It's best to have a smooth flow of exhaust gas into the wastegate tube. Since you'll be using two gates for your twin entry housing, you ideally want to mount the gates where each pair of cylinders converge into one, so you'll be venting exhaust from both cylinders (as in the picture above).

As far as which cylinders to pair up, I don't know about that one.

Also, since it sounds like you haven't picked your turbo yet, I'll give you my opinion. I don't think a twin entry housing is worth all this extra trouble unless you're using a twin scroll. The difference being a simple divided housing will just seperate your exhaust pulses to help spool, whereas a twin scroll does that AND changes the A/R to increase spool...much more effective.

 

[MyBeatGSX]

I'm in the same boat right now. So let me know what you come up with and we can compare designs. I'm using 1.5" stainless which needs to be ovaled a little to match the port. There's much less room to work with then I thought there would be, but we'll be making a custom downpipe also, so that helps. So far I think I'm going with something like this.

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Obviously that wouldn't work for your divided housing unless you want the compressor facing forward...

Divided housings pretty much eliminate reversion and cross cylinder contamination. It's impossible for exhaust to go into the turbine and back up the other side to the cylinder that's in its overlap period. This is the benefit, and yes it does help power/safety, not just spool.

EDIT: "does" help power and safety, not "doesn't".

1-4 go together and 2-3 go together.

 

[Gst18]

sounds good...
Heres what i bought so far.
12 pieces of 90 degree bends
2 pieces of 45 degree bends
4 feet of 1-1/2" sch10 welded pipe 304L
I know i bought a lot of material...(just incase i change my mind)

Here are the measurements

1-1/2" sch10 welded pipe 304L
Outside Diameter
1.900"

Wall Thickness
0.109"

Inside Diameter
1.682"

Im going to have to ovalize the tips next to the flange and im going to mount the wastegate flanges on more of an angle to help flow.

BTW does anyone know where else i can buy a t3 flange thats divided? I found one on ebay and i dont wanna buy it from that person.

My only problem after this would be to make sure i can make the manifold and turbo fit.
Im also planning on running that same design with the compressor facing towards the front.... does anyone see any problems i might run into? besides fitment?

 

[MyBeatGSX]

PM me if you want, I have divided T3 flanges.

I need to measure the bends I have, but the walls are definately way thicker than that. Are you using regular SS pipe or is it the cast SS bends?

 

[Gst18]

its not cast...
I was wondering how thick is yours?

 

[Gst18]

http://www.acestainless.com/index.php?act=viewProd&productId=2
This is the type i bought

 

[MyBeatGSX]

Hmm, yea that's the exact same stuff I have. Looks a lot thicker than 0.1" though.. I could measure it when I get back home.

Are you sure it's not cast? Mine is sand cast and that piece looks identical.

 

[Gst18]

i will recieve my items on tuesday. Usually the tickness is about .0682 or something like that.
I wanted to go a little thicker so i went with the .1... thickness

 

[GVR4592]

PM me if you want, I have divided T3 flanges.

I need to measure the bends I have, but the walls are definately way thicker than that. Are you using regular SS pipe or is it the cast SS bends?

Are you affiliated with CC-Fab?

 

[MyBeatGSX]

Yea as a matter of fact I am. In what way would you like to bi*** at me now?

 

[GVR4592]

Well my intention was to warn you of their business practices if it is in fact the same CC-Fab I'm thinking about. I'm not sure how long you've known Josh, but he is very well known in the Honda community for his shady dealings. You can go on Honda-Tech and find dozens of threads about some of the things he has done, and I can send you links from other forums as well. My advice to everybody is to not buy anything from him unless you like getting screwed around.

 

[2gAWDTalon]

GVR4592, Thanks for looking out...

 

[MyBeatGSX]

Well my intention was to warn you of their business practices if it is in fact the same CC-Fab I'm thinking about. I'm not sure how long you've known Josh, but he is very well known in the Honda community for his shady dealings. You can go on Honda-Tech and find dozens of threads about some of the things he has done, and I can send you links from other forums as well. My advice to everybody is to not buy anything from him unless you like getting screwed around.

Dear sweet mother, I can't wait to show the shop owner this post. As a matter of fact I'm going to call him right now. This is just too awsome, I love being right.

Here's the deal. My friend Corey and I have been working on Hondas for awhile. Corey met Josh about a year ago. Corey had a building and Josh had welding skills, so against EVERYONE's advice, he invited Josh to go into business with him. Obviously it was a no brainer that this would be nothing but problems and make for an instant poor reputation for the business, but whatever, don't even get me started on it.

Bottom line, it's under new management. Josh sits in the back room and does the final welding on the manifolds and Corey runs the business. There is nothing shady about it anymore and we're doing everything possible to get Josh unassociated with the business (A couple of us want him completely gone, but that's a long shot until someone can learn to weld as good as he does). And FYI, anything dealing with DSM's is handled solely by me.

 

[GVR4592]

It's good to know Josh isn't handling the business side of things anymore, he really gave the company a bad rep.

 

[MyBeatGSX]

Hopefully that cleared it up. Corey was kind of speechless that Josh's rep had spread all the way to this board.
He's to you and I both hoping he gets fired :thumbsup:

Back on topic...

Gst18, how's the manifold coming along? I'm still waiting on my flange from RRE (ordered a week ago).

 

[Gst18]

thanks for looking out.
I havent been on honda-tech in a while but can you post some threads of what you mean?
thanks

Nice catch

 

[Gst18]

ok i finished moching up my manifold. I have only one "BIG" problem. I was planning on using a t3 flange and it seems that there is no way i can fit all those 4 pipes in a divided t3 flange.
LIke i mentioned earlier the inside pipe diameter is 1.682.
I was wondering what you some of you guys use to fit the piping on the divided flanges?

 

[the_skin_eater]

Get me some measurements and I can make you a flange...I got some extra 1.5" thick SS/Titanium laying around....I can cut it down obviously....

Just pm me and Ill try to help ya if you wish.

I make exaust flanges for other cars, not out of SS, usually just outa steel... If theres anything I can do let me know.