tips for turbo manifold design

[myne]

Turbo backwards?

It makes a difference?

Oh... It's an FWD manifold if that's what you're thinking...

3rd attempt :

http://www.users.on.net/~jvizard/myn...fold/3-top.jpg
http://www.users.on.net/~jvizard/myn...old/3-left.jpg
http://www.users.on.net/~jvizard/myn...ld/3-right.jpg

[roadsailing]

yeah, on a FWD you can put it either way. you can on RWD too, but it makes the plumbing more complex. just do it whatever way gives you the simplest pipe work and best clearance.

of a FWD one of your limiting factors is going to be radiator clearance. you could always go remote oil filter for a bit more room.

[mrshin]

Here's a tip: use playdough. At least it'll set to a nice crisy finish, and taste alright if served warm with some jam afterwards!

[Toysrme]

There are a lot of designs.
If you're a newbie, a log manifold is quicker, easier, and cheaper.
Otherwise, a Ramhorn manifold gives a quicker spool, and relatively large horsepower gains over a log manifold due to the large amount of exhaust reversion in a log manifold. (Your common t3 sized turbo on a log VS a good ramhorn on a 250bhp i4 can make a 30-50bhp peak power differance at high rpms. Rules of thumb are bad... But that wone's fairly consistant.)

From there, there are as many choices as you need, or could possibly want.
Bottom mount, top mount.
Clearance problems.
(4-1 collector is generally regarded as better, even if it means more pipes.)




Log Manifold VS 4-1 collector (ramhorn) VS a 4-2-1 merge pipes.

Log


VS
Traditional ramhorn

[Toysrme]

VS
Top Mount ramhorn








VS
4-2-1 collector


I highly suggest having a 4*6 bandsaw if you're going to tackle any sort of real manifold. Using chop saws get's old when you're cutting off only1/2 a pipe (or less) at an angle... Common "$200" bandsaw is fine. You'll want a Bi-Metal blade, and if it's not the better of the two generic Asian $200 models, you'll want to sure up the stock stand it comes on.

The largest differance is that the cheaper design has no external blade adjustments.

If you can't get what "200" bandsaw is by googling... (I'm sure yall have your $200 Chinese equivilant models).

There's the $200 harbor freight model
And the $209 harbor freight model (With aforementioned better base & externial blade adjustments) Realize that *all* $200 bandsaws from any company are one of these, or the other!

Mock-ups are great, but tack-welds are spectacular! Just a little joke.

[3AM]

well ive heard that the longer the runners are the more lag there is, so its best to keep them shorter..

also the lower the turbo is the more effectively its cooled by airflow through the bay and under the car, but this can be overcome easily with a turbo blanket if you high mount.

[30psi 4agte]

Im not sure about the longer runners more lag theory ?????? ????? ( where did you hear that.?????????

A longer runner style manifold will provide better response from the turbo and a shorter runner will provide more top end


Hence the turbo cars of the 80s used very short runners!

[3AM]

well im just going on what ive heard.... it might be wrong.

[6BOOST]

My best advise for making a turbo manifold, or your mock up, is put the turbo in the engine bay where it will fit, then make it backwards from the turbo flange to the head plate. Changing 1 single pipe 1cm will change every other pipe in the design. once you have the turbo in the position of best fit, make your collector. Cutting 2 pieces of pipe to fit together in a V first, then tacking them together, then do the same with another 2 pieces. Then join these 2 together in a V, so you end up with a "merge' collector that comes to a point like the ones in the previous pics.

Make them pretty short, as you have to fit a fair amount of stuff in. Don't go bigger than the ports, rule of thumb is for any street or street/race engine, thats not pushing the limits of the power of the engine, no bigger than the port, preferably same size or slightly smaller. After you've made the collector, fit that in the bay on the turbo flange, and work backwards from there. Only tack everything together till its all built, you may want to change something, or figure out how to weld it all, as this may require some disassembly to get to other pipes. Also count on needing to oxy weld in very tight places, such as in the middle of the collector you've made.

Lastly, short pipes and long pipes don't effect spool as much as people think. Short pipes often spool earlier, but if you get the tuned length of the pipes correct for the capacity of the engine, the right size "long" pipe will actualy spool earlier, and make more power. Long pipes however in most cases will make more top end power 9 times out 0f 10. After much testing, research and development, I can tell you to forget all the theories, pipe length, spool, hp, the only 3 things to know about good manifold design, are:

1: Collector is the most important aspect. All pipes should point at flange plate, not at each other, or on an angle. Turbulence is the enemy, smooth transition to the turbo is paramount.

2: Never use short radius bends. On a flow bench, a short radius elbow loses over double the flow of a long radius elbow for a 90 Deg bend, we have found .5% for each long radius elbow and 1.2% for each short radius elbow.

3: Start with the turbo placement, and work backwards from there. Take into consideration everything that has to fit in, such as cooler pipe and intake pipe, and where all 4 pipes will fit if you put the turbo in your desired location. Having the collector assembled at this stage will help greatly in forward thinking. Easiest bet, it bolt th ehead flange plate on, bolt the turbo plate to the turbo, put earth for welder on engine with battery disconnected, hold turbo in place and have friend measure distance from turbo to head flange. Cut desired length of 10mm rod or 20mm flat bar/plate, and tack between the 2 as a support. You may need 2 supports to hold weight of turbo, but once this is done, there is your jig, now just join th dots!!!!

Cheers.............................6BOOST

[Toysrme]

Lastly, short pipes and long pipes don't effect spool as much as people think.

Exactly chief.

[JP]

I've been using a program called "Solidworks" to mock up manifolds.

I drew up the manifold flanges in autocad then imported to solidworks where you place all the parts in 3d space, I also drew up all the standard steampipe bits and a couple of merge collectors.

Once you have the flanges in place, you simply piece together the parts concentrically. It saves a lot of time being able to move stuff around quickly and see how long each section needs to be etc without doing it in the "real world" cutting and tacking to see if the parts will actually fit and clear each other, allow for manifold nuts to go on, etc etc.

[myne]

I'll have a look into this solidworks. Though I am not that optimistic - I have no skills in 3d programs.

I've thought a fair bit about this, and I'm going to have an attempt at a ramshorn style, with the collector between ports #3 and #4.

As for optimising the lengths for spool up, would a longer runner, optimised more for low end cause excessive losses up top?
What length would be ideal for say 2000rpm?

I'm also wondering if it might make more sense to optimise the INLET runner length for lower RPM, rather than simply make the exhaust runners longer.
My reasoning is fairly simple. Once you're into boost, any optimisations done in the inlet should make minimal difference to the performance, but BEFORE boost, obviously it's an NA motor, so normal NA rules apply.

Could optimising the inlet tract for an NA 1500rpm, help the spool up faster?
If so, would it reduce top end power?
If so, would a variable runner system compensate?

[BigWorm]

I think runner diameter would have a much larger impact on spool up times than runner length.

Have a look inside the inlet of your chosen turbos turbine housing. In my case I have an HKS GT2510, which is rated somewhere around 300+ hp. Now inside the turbine housing inlet the passageway narrows down to at the most 1 1/2" diameter, prolly closer to 1 1/4", and this carries the exhaust from all 4 cylinders. Currently I've been using a manifold made of 1 1/2" diameter steam pipe, so thats 4 x 1 1/2" runners converging into a 1 1/2" passage. So even with 4 x 1" runners, the biggest restriction will be the turbine itself.
Now think how much faster that exhaust gas will be travelling down 1" or 1 1/4" pipes compared to 1 1/2" pipes, and thus how much more force it will be hitting the turbine wheel with, and how much less lag there will more likely be.

Because of this (combined with the impressive results of another small capacity turbo charged motor equiped with tiny turbo manifold runners I've been lucky enough to witness) I'm having a new turbo manifold made up out of 1 1/4" pipe.

Kudos to Jason/Yellorolla for the idea.

[myne]

4AGE's appear to have a 32mm exhaust port. (1.25") So I'd assume that'd be the best pipe to use anyhow.

[BigWorm]

Sorry, I should have been more specific in relation to I.D. and nominal diameter.
1 1/4" pipe rarely (if ever) has an internal diameter of 1.125", so yes it prolly would be the best size to use.