Turbo Manifold - Size

[e30-323ti]

Hi guys,

I am needing to make a single turbo manifold for my 1JZ.

What size Sch40 would people recommend?

I was thinking 25NB (27.6mm internal dia), this closely matches the ex.port height.
And I also need to merge into a split pulse T3 flange which will be fun :\
I think I recall someone saying 25NB should be fine for 400cc/cyl (1jz isn't much more at 416cc/cyl).

And 32NB (35.7mm internal dia), just seems too big!?!?!

TIA

[e30-323ti]

oops.

Mods, please move this up a folder to the Tech section, sorry.

[IN 05 NT]

sounds good to me, ive been told to keep the pipe diametres close to the size of the head ports, as it keeps the heat and velocity in the gas flow, which means quiker spool and better response,

[e30-323ti]

Bump - Any more comments/thoughts??

[celicapain]

sounds good to me, ive been told to keep the pipe diametres close to the size of the head ports, as it keeps the heat and velocity in the gas flow, which means quiker spool and better response,

^^ ideally you want to be have slightly smaller(say 1mm) smaller ID manifold runners that the size of your exhaust ports to maximize exhaust velocity prior to belting the turbine, but were talking bees dicks here. the SC size you mentioned sounds about right to me.

[abently]

^^ ideally you want to be have slightly smaller(say 1mm) smaller ID manifold runners that the size of your exhaust ports to maximize exhaust velocity prior to belting the turbine, but were talking bees dicks here. the SC size you mentioned sounds about right to me.

That theory has been disproved.

Also keep runner length (ie manifold volume) down to a minimum. The shorter the better.

[1JZ-Rolla]

That theory has been disproved.

elaborate please? What is the ideal target diameter in that case for a given application like this?

[oldcorollas]

That theory has been disproved.

Also keep runner length (ie manifold volume) down to a minimum. The shorter the better.

you might wanna ask Yellorolla about that..
but i am looking forward to your explanation

[The Real Roadrunner]

25nb is a good size for 1jz head ports, the cross section is very close to the same diameter (smaller by 3% from memory) and should keep both the velocity and gas temps high to reduce lag.

ive built several 1J manis from 25nb and all bar 1 has worked well (still waiting Phil), the new mani for our drag corolla is built from 25nb and links a big cammed 1J with a GT42, im expecting it to work very well at building boost on the line without restricting top end but i will be make another out of 32nb to test wether it could be better suited.

split pulse is actually easy to build than a 6-1 collector, ill see if blake can get some pics for you.

Im eagerly awaiting Abently's response with random quotations of inaccurate information.

cheers
linden

[actionDAN]

25nb sounds pretty tiny...i use 32nd on all my 4agte race engines and 40nb on all my 4g63 evo engines. ive never had a build that has required runners that small. as long as it has a similar area value from port to the id of the sch40 pipe you will be fine. alot of ppl kill performance coz they think its better to go small for response. do you have the dimensions of your exhaust outlet ports?

[abently]

Actually on this topic you will find I hold all the cards.

I'll link up the scientific test report disproving the theory later on tonight.

You can't actually kill performance from going same CSA of exh port to runner diameter unless ofcourse the gas velocity is that extreme (rare due to big HP setups using similar intake duration exhaust cams) or the exhaust port was undersized from factory etc.

I'll be the first to tell you 3% smaller is not going to hurt performance, but I do hope more and more people start using shorter length runners whenever possible. I.e. Turbine entry horizontal or atleast 45 degrees. The equal length factor is negligable compared to the gains of halving the manifold volume (ie half the runner length), you can actually see the difference on the same road reading the tacho and boost let alone on a dyno.

[actionDAN]

i didnt say you would kill performance by going same CSA of ex port. just curious...how many of these have you actually made, and what CAD program do you use to design them? we had a 4agte back in nz that gained an extra 25kw at the wheels at 1 psi less boost from changing the runner length from about 283mm to about 760mm long if i remember right. and it made the bov way louder (i know thats gay!). i would always recomend going longer just coz of my experience. maybe im wrong, but the fastest cars on earth have extremely long runners.

i hope im not taking this too far. after all its just a manifold for a street car.

[abently]

you might wanna ask Yellorolla about that..
but i am looking forward to your explanation

As promised > http://www.mne.psu.edu/ifrtt/Confere.../s2-2%2087.pdf

[love ke70]

i find this interesting, i would have thought the more gas temp you can get through the turbo the better as thats what makes it spool, interesting to hear about more power from a longer runner.
maybe it was just a better manifold design and had nothing to do with the length of the runner?

cheer, andy

[abently]

i didnt say you would kill performance by going same CSA of ex port. just curious...how many of these have you actually made, and what CAD program do you use to design them? we had a 4agte back in nz that gained an extra 25kw at the wheels at 1 psi less boost from changing the runner length from about 283mm to about 760mm long if i remember right. and it made the bov way louder (i know thats gay!). i would always recomend going longer just coz of my experience. maybe im wrong, but the fastest cars on earth have extremely long runners.

i hope im not taking this too far. after all its just a manifold for a street car.

No that's fine. I enquired about this exact phenomenon a while ago and basically it comes back to inertia tuning. There is a trade off in turbo response by going to a longer manifold but if the Turbo only starts to spool at 4000rpm then you should tune the manifold runner lengths to the cam timing and Intake manifold.

EDIT: To put some perspective on that 25kw gain, can you recall what the power reading at the wheels was ?

I guess if you still have doubts, you could always look at some WRC exhaust manifolds.