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Tubular Manifold design for 350bhp? - Printable Version

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+--- Thread: Tubular Manifold design for 350bhp? (/showthread.php?tid=7804)



Tubular Manifold design for 350bhp? - Cooper - 07-13-2017

I'm building a G-Wagon OM605 and i'm using a GTX28 turbo (T25 flange) which should give me around 300-350bhp at 2bar

Should I use tubular manifold? If so, what size runners?

I want lots of low down torque/spool, so maybe the stock manifold would be okay? I don't want high EGT though.


RE: Tubular Manifold design for 350bhp? - MartinB - 07-13-2017

Big IC in first step.


RE: Tubular Manifold design for 350bhp? - Cooper - 07-13-2017

(07-13-2017, 01:44 PM)MartinB Big IC in first step.

Got a nice big intercooler. 500x500mm


RE: Tubular Manifold design for 350bhp? - atypicalguy - 07-14-2017

(07-13-2017, 05:43 AM)Cooper I'm building a G-Wagon OM605 and i'm using a GTX28 turbo (T25 flange) which should give me around 300-350bhp at 2bar

Should I use tubular manifold? If so, what size runners?

I want lots of low down torque/spool, so maybe the stock manifold would be okay? I don't want high EGT though.

When you say it should give you x power level, what information is that based upon?

How much air does the turbo compressor flow at what rpm?
How big is exhaust housing?
What rpm do you want that target power to occur?
What bsfc are you assuming?
What volumetric efficiency?
What compressor efficiency?
What intercooler efficiency?
What air to fuel ratio?
And is this 350hp at the wheels or at the crank?

Answers to these questions will alow you to pick a good turBo and figure out what fuel level you need from the pump.

Or just stop asking questions , stick it all  together, and watch your egt. You can make that power with the stock manifold probably.


RE: Tubular Manifold design for 350bhp? - Turbo - 07-14-2017

could not said it better my self, right on spot to start with


RE: Tubular Manifold design for 350bhp? - Cooper - 07-14-2017

I'm not a turbo expert by any means hence why I've been looking for examples of other people's setups and dynos. I've put all the figures into the borg warner turbo calculator and it basically told me I need a gt2860 size turbo, so I've bought one and it's on its way. There were basically no BW turbos that were small enough in the 200 range to give me the low down boost I want.

I'm not bothered about an exact science, I'm just wondering if I'm best to make myself a tubular manifold or is it a pointless exercise given the power i want? I'm not bothered of it only makes 300bhp (or less), but from what I've seen of these gtx28 turbos, if pushed quite hard it might make nearer 350bhp.

I AM bothered about egt and since this is in a 2 tonne truck and will be used for pulling I want to know if there's a benefit of a tubular over the stock manifold.


RE: Tubular Manifold design for 350bhp? - NW124 - 07-14-2017

(07-14-2017, 11:23 AM)Cooper I'm not a turbo expert by any means hence why I've been looking for examples of other people's setups and dynos. I've put all the figures into the borg warner turbo calculator and it basically told me I need a gt2860 size turbo, so I've bought one and it's on its way. There were basically no BW turbos that were small enough in the 200 range to give me the low down boost I want.

I'm not bothered about an exact science, I'm just wondering if I'm best to make myself a tubular manifold or is it a pointless exercise given the power i want? I'm not bothered of it only makes 300bhp (or less), but from what I've seen of these gtx28 turbos, if pushed quite hard it might make nearer 350bhp.

I AM bothered about egt and since this is in a 2 tonne truck and will be used for pulling I want to know if there's a benefit of a tubular over the stock manifold.
As long as you have the right fueling, exhaust housing, cooling in place and downpipe/ exhaust egt's should be fine. 

There will always be a benefit running a tubular manifold but the power your wanting to make you might not see the gains or spooling characteristics your after. Now that being said you have room to grow down the road if you ever wanted to go bigger, so if you do go the tubular route make sure the mounting point will clear everything if you wanted to put a larger charger later on. 

So at this point it's up to you if you want to spend the $ for a tubular or run the stock one.


RE: Tubular Manifold design for 350bhp? - bruno_pinho - 07-14-2017

300hp with a gtx28?!good luck...


RE: Tubular Manifold design for 350bhp? - Cooper - 07-14-2017

(07-14-2017, 03:29 PM)bruno_pinho 300hp with a gtx28?!good luck...

Have you seen the compressor map for a gtx28? No luck needed.

I've seen them make 420bhp on a vw 1.8T at 3 bar and they're still efficient at that.

The little weedy gt22 will flow 200bhp at 1.5bar... I don't see your point.


RE: Tubular Manifold design for 350bhp? - awsrock - 07-14-2017

These diesels require much more air to make similar power to gas. At the very least for 300hp you will need a 2871 but even then the turbine is kind of small. Maybe with a big turbine housing...


RE: Tubular Manifold design for 350bhp? - awsrock - 07-15-2017

To somewhat contradict myself, here is a video of 290hp dyno with 2860, but it is on a 606

https://www.youtube.com/watch?v=c5zJULLd7sU

However, I suspect this was at a high rpm with some cam / valve mods. It does not say. It is also the only dyno I've seen of a GT28.

On the flip side, this G wagen with an HX35 only made 260hp. 

https://www.youtube.com/watch?v=az9KUHrdJVM

I don't know the fueling on the pumps, but it must be pretty low (less than 120cc). I think the power rating might be corrected to be at the crank as well.


RE: Tubular Manifold design for 350bhp? - Cooper - 07-15-2017

(07-15-2017, 10:08 AM)awsrock To somewhat contradict myself, here is a video of 290hp dyno with 2860, but it is on a 606

https://www.youtube.com/watch?v=c5zJULLd7sU

However, I suspect this was at a high rpm with some cam / valve mods. It does not say. It is also the only dyno I've seen of a GT28.

On the flip side, this G wagen with an HX35 only made 260hp. 

https://www.youtube.com/watch?v=az9KUHrdJVM

I don't know the fueling on the pumps, but it must be pretty low (less than 120cc). I think the power rating might be corrected to be at the crank as well.


That is running the old Gt2860, whereas I've got the gtx28. If you compare the compressor maps you'll see a big difference in flow rates and efficiency. I know of an Aussie pushing a GTX2863 to 40psi which makes use of all the fuel that a 7.5mm pump has to offer and that is giving him 400bhp.