Single turbo setup?

[Matra et Alpine]

Matra: why the generalisation? I am sure that there is a way to get a single turbo to work on a V12 without suffering "horrendous losses"...

The laws of physics
ye cannae beat them

Exhaust and inlet are GASSES, which means they are compressible and in a transmission pipeline that means you need to keep the pressure up for it to work as effectively. So now instead of 10-12 inches of exhaust pipework, you've got 10 feet -- and then 10 feet on the inlet !! Nope, it's BS on the "Lag" comment, it will have awful lag till it manages to pressurise all of that piping ... fine once it's up there it'll not de-pressurise very quicly either, so won't suffer off-boost return lag as much. Can see it working "fine" as a low pressure boost solution like a diesel. But as a closed-loop system the control is a nightmare and has delays -- whcih means lag !!!

12 exhaust pipes making their way to a single turbo inlet requires some serious flow design and SPACE - you can't have any sharp turns or twists and MUST combine the flows to keep the exhust pressure equalised. So you either put it on top of the engine ( and lift the bonnet by a foot ) or you put it to the front or rear of the block ( and extend the length of the car )

[h00t_h00t]

In short, don't bother.

I'm not sure the BMW v12 is strong enough to take much boost anyway. If it was it would have had more publicity surely?

[Kitdy]

The laws of physics
ye cannae beat them

Ye cannae kick your granny of the bus...
No you cannae kick yer granny off the bus...
No you cannae kick yer granny, for she's your daddy's mummy no you cannae kick yer granny off the bus!

So let me get it straight. Sinlge turbos on V-12s are impracitcal as designing the sloping curvy exhaust pipes in such a way that they have equal pressure and join together to go to one turbo is bad because it takes a large amount of piping, which means it takes longer to pressurize that volume of piping, thus creating more turbo lag and taking up more space?

Am I on the money? I live to learn.

[rev440]

It would also depend on what series turbo, the over all size of the turbo and so on.

[hightower99]

In short, don't bother.

I'm not sure the BMW v12 is strong enough to take much boost anyway. If it was it would have had more publicity surely?

Actually it can and does take a good deal of boost (I believe 15psi on stock internals IIRC) and it is a popular engine to use FI on (normally a twin turbo setup).

However I only have the one turbo (GT4088R) and pipe work will be relatively cheap for me (compared to buying another turbo) I don't think I would mount it quite like STS does right at the back. I am contemplating mounting the entire engine 100mm-120mm back in the car (I know this requires alot of work) and mounting the turbo in front of the engine block that way the exhaust only has to travel about 6" more than it normally would with a normal turbo manifold. With proper insulation wrapped around the manifolds the exhaust shouldn't be any colder by the time it gets to the turbine (probably be hotter then normal).

I will need to think about the whole plan some more.

Next question: Has anyone heard of modifying a cars existing AC system to work as an IC? Seems to me that it would work quite well being a refridgeration type cooler. Does anyone have any ideas on how to make a working system (thing to think about?).

[2ndclasscitizen]

What car are you planning on putting this engine in?

And that sounds like a good idea, but it may prove simpler and better to simply get a better IC (multi-core, air-water type etc)

[hightower99]

What car are you planning on putting this engine in?

And that sounds like a good idea, but it may prove simpler and better to simply get a better IC (multi-core, air-water type etc)

It is going to go into a E36 chassic 3-series. Possibly an M3. The major problem with ICs is space, so I am hoping that a refridgerator style IC will be more compact.

[2ndclasscitizen]

I can't see it being more compact. All extra piping and modifications to the AC compressor and IC itself would take up a lot of space, especially in the front of an E36, I really think in the end a good quality, high-spec water-air IC would do the job, maybe 2 small ones to aid in placement.

[hightower99]

I can't see it being more compact. All extra piping and modifications to the AC compressor and IC itself would take up a lot of space, especially in the front of an E36, I really think in the end a good quality, high-spec water-air IC would do the job, maybe 2 small ones to aid in placement.

Got any suggestions on where I might find high spec water-air ICs?

[2ndclasscitizen]

http://www.pwr.com.au/

[hightower99]

http://www.pwr.com.au/

Thanks for the link... Looks like the have some good air-water ICs....

[Quiggs]

How about you take the AC system out and put in an intercooler.

[h00t_h00t]

It is going to go into a E36 chassic 3-series. Possibly an M3. The major problem with ICs is space, so I am hoping that a refridgerator style IC will be more compact.

If I was in your position I'd be more interested in making a standard V12 fit.Since the BMW V8 conversion is a tight fit the V12 will need significant body modifications, and thats BEFORE the turbos and intercoolers go on.

Oh and sourcing things like the ridiculously rare manual box from an 8-series (because the auto won't fit), a custom propshaft and driveshafts, working out how to stop the back wheels lifting off the ground once the engine is in place and a whole bunch of other issuses will become project killing problems if you can't budget for two turbos.

[Quiggs]

If I was in your position I'd be more interested in making a standard V12 fit.Since the BMW V8 conversion is a tight fit the V12 will need significant body modifications, and thats BEFORE the turbos and intercoolers go on.

Oh and sourcing things like the ridiculously rare manual box from an 8-series (because the auto won't fit), a custom propshaft and driveshafts, working out how to stop the back wheels lifting off the ground once the engine is in place and a whole bunch of other issuses will become project killing problems if you can't budget for two turbos.

C'mon now, you're acting like this car might actually see the light of day some day...

[hightower99]

If I was in your position I'd be more interested in making a standard V12 fit.Since the BMW V8 conversion is a tight fit the V12 will need significant body modifications, and thats BEFORE the turbos and intercoolers go on.

Oh and sourcing things like the ridiculously rare manual box from an 8-series (because the auto won't fit), a custom propshaft and driveshafts, working out how to stop the back wheels lifting off the ground once the engine is in place and a whole bunch of other issuses will become project killing problems if you can't budget for two turbos.

You have a few valid points:

Yes the V12 is a tight fit but it doesn't require "significant body modifications" However I am going to try to mount it back at least 100mm (I am aiming for 120mm) so there will be significant modification in this project. But the expence of this is small to me because I have welding equipment and more than enough materials to do the work. It will still be time consuming but I don't have any real dead line.

Sourcing the manual gearbox isn't hard either only the 850CSi manual gearbox is rare (mainly because only 1500 were built). The more modest '93 850Ci did have a manual transmission option here in europe.

As for custom propshaft and driveshafts... Shouldn't be a huge problem as I will probably just shorten the existing propshaft and driveshafts to fit.

I could budget a twin turbo setup but I would rather use that money on some other area of the project. I already have the turbo (well I paid for it, should be here soon) and I like the challenge of how to get the single turbo to work with the V12.

BTW: putting the M70 into an E36 chassis has been done before and it doesn't mess with weight distribution too much so as there would be any trouble keeping the back wheels on the ground. I intend to mount it a min. of 100mm further back anyways.