I noticed looking trough alot of posts that most people are running fairly long primary tubes on their custom turbo headers. Is there a reason for this other than space/clearance problems. You would think that the closer you could get the turbo to the motor the better, at least that is the way I built mine. Also what is the norm for the id of the tube? Thanks guys!

 

The common consensus seems to be around 15"- 18" long with 2" primary tubing.
Shorter manifolds will increase lag and be down in power, particularly the torque curve due to increased backpressure as I understand.

 

Why would the backpressure go up on a shorter manifold?

 

Some people think close is better cause its closer to the exhuast pulse

WRONG!!!!!!!!!!

its about pressure!

you want long runners to keep the flow pressurized

Think of a garden hose
ever notice that with a long garden hose
when you turn off the water
and hold the gun sprayer
it still comes out strong
and the water takes longer to run out
then with a short water hose


get my drift?...hehe

 

Damn you guys. Back to the drawing board.

Thanks for the info

 

It'll work tho

I've seen some like that
made for 1st gens and older RX's

 

How much down on HP are we talking? I allways tought that it was the velocity/heat of the exhaust that drove the turbo not pressure. That is the only way that you could have turbine pres. and compressor pres that were close to the same, right?

 

depends on the size of the turbo
you plan on using..........

for a big turbo
wanting qucikest spool

you want long runners
to keep a "reserve" of air

 

Small compared to that!!!! Mine is more rotaryer tough. To4r .96 ar

 

looks Nice!

you'll still be able to make decent power
but you could make more with a nice "header" turbo manifold

that turbo can come much further

lke this one

 

MMMMMMMMMMMMMMM Right hand drive. Whos car is that? I dont think decent power will be enough for me. If it doesnt scare the hell out of me I am selling it

Thanks for the complement

 

No need to scrap it, that manifold will do just fine for you.

 

Like ZeroR said, its not going to be THAT big of an issue. I wouldnt scrap it. At least finish the car and see how it feels. If you are happy with the car then leave it alone.

 

At least I have someone that agrees with me. I have been saying this for at least 3 yrs ever since my first turbo kit became available to the public.

 

I slept on it last night and I think that is what I will do. Then mabe try a longer primary and dyno the car again to see the diff.

Thanks everyone

And pluto, I had a little setback on the progress of my car but it should be ready for you to tune before the end of the year.

 

LOL ... that water hose analogy ain't doing it for me. No offense meant, but I don't think our manifold runners are storing energy due to dilation under pressure. Maybe it has something to do with the mixture accelerating to a higher velocity as it has more time to expand in a longer runner or perhaps there is some pressure wave phasing that works. Either way I can by a longer runner length being superior but the hose analogy ain't doing it for me, still LOL

 

Read another thread that talked about positive and negative pressure waves. I'll buy that theory BUT it did not say that it was a restriction but a way to tune the power curve. By running shorter or longer pri. you shift the power curve up and down just like intake runer length does. Now that sounds very beliveable.

 

blah lol

I know its not a technical explanation

but the basic pricinple is there

I know I had way less lag
(time when it hits positive pressure)

with a 16" tubular manifold

compared to the HKS cast manifold I got now
thats a FACT

I'm working on a 100% new setup
going back to a nice 2" OD long runners tubular manifold

 

good info on this thread!

hey 13B-RX3, any pix of the front of your motor? i'm interested in your engine mounting, looks like a 1st gen cover?

 

i've actually wondered this too.....good thread if i get some pics up of my manifold would u guys mind giving some input on it?

 

It is a gen 1 cover. I hate to be a pic ***** but I have all the pics of my car in the other rotary section under RX3 street/race check it out.

Do you think that going from a cast manifold to a true tube header had anything to do with it regardless to length?

 

well all I know
if your looking for the best design

a tubular manifold can't be beat

after attending NMRA, NHRA, NDRA and World Street nationals events

I've seen some crazy long turbo headers
in mustangs they put 101mm turbos all the way to the front of the car righ in the middle

there has to be some reason
why people with very large turbos run...very long turbo manifold

John shepard's Talon has a GT42R/T4 with a Long *** turbo header that runs sideways
to the passenger sde

and he has run 7.9's

 

pro's / con's ? whatcha think?









the turbo is a pt63 for size reference.........altho i will be running a gt40r

 

dayum, did you make that yourself? i need to try something like that one day...for your main flange, is that two pieces welded together? may i ask why?

 

crazy!:-)