View Full Version : Turbo exhaust tube diameter questions???


TT LS2 1969 Camaro
12-23-2007, 06:58 PM
I have to fabricate headers for my twin-turbo LS1 and i need feedback about tubing sizes. i had planned on running 1 7/8" tubing, but was told that that small of a diameter would choke the engine. It was recommended for me to run at least 2 1/4" tubes to the merge collector. The engine will be force-fed by two Turbonetics 62-1's. Any help, advice, suggestions and or feedback would greatly be appreciated. Thanks all!

HUNTER02SS
12-23-2007, 07:35 PM
What kind of power you looking to make. I think you will be fine with the 1 7/8 pipe. I have truck manifold's and they are pretty small diameter also!

TT LS2 1969 Camaro
12-23-2007, 10:52 PM
What kind of power you looking to make. I think you will be fine with the 1 7/8 pipe. I have truck manifold's and they are pretty small diameter also!
Well hopefully, if all goes as planned, the engine will be in the 900-1000hp range. Looking to run a max of 18-20psi, it will be intercooled, yad, yada, yada...

Josh@KY-Turbo
12-23-2007, 10:59 PM
I have done them with great sucsess in 1 5/8".

W8N2SQZ
12-23-2007, 11:19 PM
I'm a little confused? Do you mean the tube from the flange at the head to the collector or from the collector to the flange on the turbo.

I have seen good success with 1 5/8" from the flange at the head to the collector. Many people are using stock manifolds and I doubt they are bigger than 1 5/8s to the collector. However I have never measured because there are 7 second cars on the stock manifolds.

From the collector to the flange on the turbo you will want 2.5" tubing. The stock manifolds measure right at or just under 2.5" at the collector.

Good luck on the build.
Glenn

FieroZ34
12-24-2007, 01:17 AM
I personally would go 1 7/8", but that is the maximum your motor can really use at those power levels.

I don't know why there are people comparing stock manifolds to your header. The stock manifold is what you want to replace, so improve upon it. Just because it works doesn't mean it can't be better, making more power at lower boost, and spooling quicker.

I would go 1 7/8" primaries, into dual 2.75" pipes into the two turbochargers. 1 5/8" to dual 2.5s will work great as well, but I think at the specific outputs you'll be nearing you should go at least 1.75".

TT LS2 1969 Camaro
12-24-2007, 01:44 AM
Everyone that I deal with says to use 304 stainless steel material to build the exhaust system out of. Any comments or suggestions about mild steel vs. 304 stainless?

TT LS2 1969 Camaro
12-24-2007, 01:45 AM
I personally would go 1 7/8", but that is the maximum your motor can really use at those power levels.

I don't know why there are people comparing stock manifolds to your header. The stock manifold is what you want to replace, so improve upon it. Just because it works doesn't mean it can't be better, making more power at lower boost, and spooling quicker.

I would go 1 7/8" primaries, into dual 2.75" pipes into the two turbochargers. 1 5/8" to dual 2.5s will work great as well, but I think at the specific outputs you'll be nearing you should go at least 1.75".

Are you kidding me?!?!?! Stock manifolds, running 7's?!?!?! I need proof and pics! Please.

Josh@KY-Turbo
12-24-2007, 02:47 AM
I was referring to 1 5/8 tubes for my Turbo headers. I use 2.5" from the header to the Turbo Flange.

DanZ28
12-24-2007, 03:36 AM
I think 1.75" would work great. Isn't the exhaust port on the head only 1 5/8" and ported ones around 1.75" for most heads?

Dan

parish8
12-24-2007, 04:18 AM
1 5/8" with 2.5" logs on my truck. good for 1050rwhp thru a 4l80e and tcase.

i think the 2.5" logs are a little on the large side. we are steping down to 2.25" logs on our next project and are hoping to see ~1500rwhp eventualy.

here is a pic of a header we made today.

http://www.neufamily.org/images/67novagallery/images/67nova%20166.jpg

y2khawk
12-24-2007, 06:24 AM
Are you kidding me?!?!?! Stock manifolds, running 7's?!?!?! I need proof and pics! Please.

search for Ohio Boys

Pretty sure both cars are on truck manifolds and in the 7's. But they have got to be getting close to the limit ;)

FWIW, Tom's radial car has been going high 180's on 1 3/4" primary into 2.5" crossovers. Even with the header shrouding the port pretty badly it's still making power :)

DanZ28
12-24-2007, 07:09 AM
search for Ohio Boys

Pretty sure both cars are on truck manifolds and in the 7's. But they have got to be getting close to the limit ;)

FWIW, Tom's radial car has been going high 180's on 1 3/4" primary into 2.5" crossovers. Even with the header shrouding the port pretty badly it's still making power :)

Tom running AllPro heads? Just wondering because of the shrouding as I know they have 1 7/8" ports on their 6 bolt heads.

SUPERBOOST
12-24-2007, 08:48 AM
Everyone that I deal with says to use 304 stainless steel material to build the exhaust system out of. Any comments or suggestions about mild steel vs. 304 stainless?

Mild steel is cheaper and easier to weld and work with,it works ok too but it will rust and look terrible in no time.Even if you have it coated it will rust from the inside.Best to bite the bullit and use stainless even though it cost more,its harder to work with at least in the average home shop.It will have to be tig welded also.

y2khawk
12-24-2007, 09:46 AM
Tom running AllPro heads? Just wondering because of the shrouding as I know they have 1 7/8" ports on their 6 bolt heads.

ET canted valve. They have 2" ports, so we're not exactly ideal. Since the headers were made for a different car, we just dealt with it.

smokinHawk
12-24-2007, 09:59 AM
Mild steel is cheaper and easier to weld and work with,it works ok too but it will rust and look terrible in no time.Even if you have it coated it will rust from the inside.Best to bite the bullit and use stainless even though it cost more,its harder to work with at least in the average home shop.It will have to be tig welded also.

how are they going to rust from the inside if you have them coated.
they will be fine if coated.
some of my junk has been ok, also check out klyes green TA that stenod built looks fine to me.

parish8
12-24-2007, 11:00 AM
Mild steel is cheaper and easier to weld and work with,it works ok too but it will rust and look terrible in no time.Even if you have it coated it will rust from the inside.Best to bite the bullit and use stainless even though it cost more,its harder to work with at least in the average home shop.It will have to be tig welded also.

that pic of a header i posted up above is 304 stainless scheduel 10. cheap and easy to work with. should be very durable too. you can mig or tig the stainless just like steel.

the little elbows are $7, a 2.25" elbow is $11. that entire header has $132 in parts and we burnt up $22 in holes saws. that includes the t4 flange and header flange all in 304 stainless.

W8N2SQZ
12-24-2007, 03:55 PM
Hey Parish, did you notice a difference in spool when dropping from 2.5" tube to 2.25" tube?

parish8
12-24-2007, 04:03 PM
we are just now puting the 2.25" combo together and it will be completely diferent so i wont be able to say even once it is running.

SS4Matt
12-24-2007, 04:30 PM
i used 1 3/4" stainless for my header material, and then a stainless works collector and 2 1/2" stainless for my crossover from the merge to the turbo, and from the turbo all the way to the back of the car is 4" stainless downpipe. and all my cold stuff is in aluminum 3 1/2" and 4"

1320
12-24-2007, 04:49 PM
Remeber the dutweiler thunderbird that ran comp eliminator. It ran a 399 ford, and said it had 1.5 inch headers, they looked like 1 5/8's to me but may have been pretty thick. It only ran 6.70's about 10 years ago..... it probably made in the 1600 hp area I bet.

TT LS2 1969 Camaro
12-24-2007, 10:00 PM
i used 1 3/4" stainless for my header material, and then a stainless works collector and 2 1/2" stainless for my crossover from the merge to the turbo, and from the turbo all the way to the back of the car is 4" stainless downpipe. and all my cold stuff is in aluminum 3 1/2" and 4"

If you could link up a pic for me to view, that would be awesome. I'm not really sure what you mean by the term "crossover" either. I was thinking more along the lines of something like the pic that I have attached. But I am unsure of primary tube sizes for the application that I plan on running.

SS4Matt
12-24-2007, 10:35 PM
If you could link up a pic for me to view, that would be awesome. I'm not really sure what you mean by the term "crossover" either. I was thinking more along the lines of something like the pic that I have attached. But I am unsure of primary tube sizes for the application that I plan on running.

i don't have a camera at the moment since my last one took a shit and i've been too cheap to go buy a new one :lol: but just like your pictures show...the headers are all 1 3/4". the "Crossover" is in 2 1/2" the crossover is the piece that goes from each collector/header to the turbo.

TT LS2 1969 Camaro
12-26-2007, 12:35 AM
how are they going to rust from the inside if you have them coated.
they will be fine if coated.
some of my junk has been ok, also check out klyes green TA that stenod built looks fine to me.

What are the pros and cons of using stainless vs. mild steel?
Will the mild steel hold up in a 20psi of boost situation for a street-driven car?
I appreciate all of your input, fellas!

Reject
12-26-2007, 06:51 AM
the mild vs SS has been done many times on here before, do a search, litterly HUNDREDS of threads

Big Geek
12-26-2007, 10:50 AM
Thing to remember is that the more area you have the less velocity you will achieve unless you are going to spin it hard. Gotta have velocity to get the exhaust wheel moving. Just part of the puzzle.

Jim C.

FieroZ34
12-26-2007, 12:39 PM
Volume > velocity.

Although you need the velocity, the volume of exhaust is more critical. So you need to find the size that maximizes velocity without impacting volume.

TT LS2 1969 Camaro
12-26-2007, 02:33 PM
Thing to remember is that the more area you have the less velocity you will achieve unless you are going to spin it hard. Gotta have velocity to get the exhaust wheel moving. Just part of the puzzle.

Jim C.

I understand....Does anyone know the approximate diameter size of the "truck" manifold exhaust manifolds? I think that would be a good starting point for me to determine what exactly I need for my set-up, if guys are out there using them to go 7's!!! That's unbelieveable!:D

W8N2SQZ
12-26-2007, 08:54 PM
I am not sure on the truck manifold size, but I just put on a pair of C6 manifolds and they look A LOT better than the stock 2001 F-body manifolds I have.

The other nice thing about the stock manifolds is that they are cast and durable. I have twin TC66's from Forced inductions and they are capable of 1000 at the tire.

So I decided to run the C6 manifolds for cost and ease of installation. Plus they are durable and they are easy to change plugs on.

TT LS2 1969 Camaro
12-26-2007, 10:40 PM
I am not sure on the truck manifold size, but I just put on a pair of C6 manifolds and they look A LOT better than the stock 2001 F-body manifolds I have.

The other nice thing about the stock manifolds is that they are cast and durable. I have twin TC66's from Forced inductions and they are capable of 1000 at the tire.

So I decided to run the C6 manifolds for cost and ease of installation. Plus they are durable and they are easy to change plugs on.

Hmmm...any pics of the manifold or a twin turbo set-up with those manifolds? I have a '69 Camaro...not sure of clearence issues that would arise from either of the manifolds. A pic will kinda give me a good idea of locatio and or space and routing requirements. I appreciate the feedback! Please keep it comming.

ABeasst
12-26-2007, 10:43 PM
I am not sure on the truck manifold size, but I just put on a pair of C6 manifolds and they look A LOT better than the stock 2001 F-body manifolds I have.

The other nice thing about the stock manifolds is that they are cast and durable. I have twin TC66's from Forced inductions and they are capable of 1000 at the tire.

So I decided to run the C6 manifolds for cost and ease of installation. Plus they are durable and they are easy to change plugs on.

thats the exact setup I'm starting on.

W8N2SQZ
12-26-2007, 11:54 PM
NICE!!

I should have pictures in about three weeks!

How about you?

ABeasst
12-26-2007, 11:59 PM
NICE!!

I should have pictures in about three weeks!

How about you?

I'm a ways out finishing up the motor now.