Twin Turbo 325i, one rear mount, one up front?

[327ire]

Some of you may remember I started a rear mount turbo project aaaages ago. Engine trouble has stunted the progress. Im now at a point where I have to replace the mr2 turbocharger due to poor oil supply so Im starting to rethink the project.

1. Do I spend £235 to replace the turbo?
2. Buy an ebay mani and t3 turbo and go the normal way?
3. Do BOTH?

Doing both would open up twin turbo power but is it possible? It would mean that...

A. the bigger turbo is rear mounted and gets all gas AFTER the turbo in the engine bay. (normally spools at about 2000rpm)
B. the smaller turbo is mounted in the engine bay getting a feed from all 6cyls.

Am I dreaming???

[GrindCulture]

Do it! Not seen/thought of that before, could be pretty cool and remove the lag associated with rear mount turbos. There are probably reasons why it's a bad idea, but ignore them

[bigbhpwannabe]

i have been watchin your project as i read the one on the 205 gti rear mount turbo i would say that because you started and had option 1 running and only a problem was the oil feed seems a bit early to change plan ,and it seems that no3 could be a bit complex as the exhaust comeing from the front turbo to feed the rear turbo would have to be big enough to not ristrict the amount of gases leavein both turbos ,but not too big to cause extra lag to the rear turbo although im sure i will be corrected
no 2 is gonna be a few more quid ,and you will rlly need to relocate the oil filter with that ebay manifold as i have tryed it
i gave up on the ebay manifold as i have the cheap one ,there is two and the exotic raceing is the one too have
you can have a look at the cheap one if you like its well funny ,kinda like a banna and if put on faceing up the studs and ports dont line up
gary

[E30BeemerLad]

what's the problem with the rear oil feed?

[dannywolf]

I was using an independent system.

12v pump in the boot slightly above the turbo, feeding towards the turbo, from the turbo to an oil cooler above the pump (also in the boot) and into a tank (coolant reservoir from a mk2 golf) then back to the pump.

The pump overloaded and melted. I need a pressure release valve apparently. Not really sure what to get. What was happening was the pressure was building up and overloading the pump.

Would it be possible to tap into the engines system? Is there a cost affective way to pipe into the engine from the rear of the car?

[dannywolf]

This is 327i by the way!

[Gunni]

this is such a way to over complicate things,
a single turbo close to the engine would yield greater speed at which this car could be finished.

there is nothing overly complicated about putting a turbo up front, so why bother fitting one in the back with the complications related to that?

And being different is not cool when it yields no real gains over doing things right.

[327ire]

m o n e y is the reason for my rear mounted turbo. If i hadnt messed up the turbo and pump (which was just my inexperience to blame) it would have cut out the cost of a manifold and an intercooler. Both of these things cost 100's for ones that work. Im just looking for more power in my e30, not looking to "be different".

If you feel so strongly about it....
PLEASE buy me a turbo manifold and intercooler for my m20 engine.

"With great challenges comes great engineering", is this not your quote? The word hypocrite comes to mind.

[fuzzy]

£235 to replace a turbo ? is that all? i wish mine were as cheap ....3 times £800 each so far....

[appletree]

Replace the turbo and sort the oil feed and then have fun driving it £230 is cheap boost!

[Gunni]

m o n e y is the reason for my rear mounted turbo. If i hadnt messed up the turbo and pump (which was just my inexperience to blame) it would have cut out the cost of a manifold and an intercooler. Both of these things cost 100's for ones that work. Im just looking for more power in my e30, not looking to "be different".

If you feel so strongly about it....
PLEASE buy me a turbo manifold and intercooler for my m20 engine.

"With great challenges comes great engineering", is this not your quote? The word hypocrite comes to mind.

If you don´t get the quote then it´s not for you.
You obviously have a engineering proplem upon you,
looking for more power in your e30, and you choose a turbo, in itself a good choice,.
"great engineering" means that you not only have to use your head but your hands, you could have made an adapter for your stock exhaust manifolds
like so.



The adapter when bought from mild steel or cut from old exhaust , could have cost as little as nothing + one T3 or T4 flange

And then at least a downpipe to the stock exhaust.

And then you wouldn´t have had to get charge piping from the rear mount turbo either to the engine either.

Rear mounts are only valid when you have an engine bay where there is NO room. It´s absolutely not a cheaper choice....

[327ire]

2 years ago I didnt know how to drive a car. Today I dont know how to weld a custom turbo manifold adapter! Im a school teacher, not an engineer. I like fucking around with cars. Its fun and a challenge. No need to knock me!

To the rest,... thanks for the motivation! Im bidding on an almost new replacement turbo. Il get a post up soon and get your advice on how to get a proper feed of oil.

[appletree]

Fair play mate, i can see why you've gone the route you have, like you say its been a learning curve for you, an you've had fun overcoming the challenges of doing a project like this one!

At the end of the day who cares if it doest make as much bhp as a 'conventional' turbo set up, if your happy with what your doing!
So carry on, keep takin pics and make this forum abit different and worth reading.

Who knows it might be less bhp behind a normal set up than you think and if you didn't explore the idea we'd never know.

[Chuntington101]

327ire have you got a link to your rear mount biuld???

also i think the below thread might intrest you if you are after ways to make a rear mount without the lag.....

http://www.ls1tech.com/forums/forced-in ... -kits.html

Take a look at post 12 onwards. basically the guy is using a twin scroll turbo but only using one side of the housing. once a set boost presure is reached, the 'gate opens and start to use all the housing. This effectively means you are runninng only 50% AR untill peak boost is made (or whatever you set the gate to open at). if you are using a big enough turbo then you could do away with a second wastegate all together!

so on a 325 you could run say a GT35 (or equivilent) turbo and get VERY fast boost responce and still make bags of power!

Thanks

Chris.

PS i think its great to see people trying these things. i have been thinking about a rear mounted turbo E30 for a while.

[Chuntington101]

327ire can you post any pics? i have searched but all your pics are not showing for some reason.

Chris.

[appletree]

Just thinking about your oil pressure problem we use a pressure regulator like what you need in our machines at work they drop the pressure from 8bar to 0.5bar and are adjustable inbetween the limits.

If you put one of these after your pump and pipe the recirc (wasted pressure) back to your resivour and then plumb a pressure gauge after the regulator and your cooler (incase theres a pressure drop across the cooler) to show the line pressure to the turbo you will be fine.

Think normal engine oil pressure will be 3.5- 4bar once warmed up but i dont know what pressure you normaly send to the turbo, weather its regulated or if its full engine pressure.

[Turbo-Brown]

Guess it depends on the system, but there's a thing on e30tech at the moment saying that Holsets should have no less than 10psi and no more than 60odd psi.

The only problem I can see with having a large rear turbo and a small front one is that the small one will be strangling the engine all the time.

I'd say either stick with with one turbo at the back or just switch to a front mounted one.

It almost makes more sense (in my mind anyway) to use the smaller turbo at the back where it has a smaller volume of gas/unit time to pass....but it'd still be strangling the larger front turbo.

Personally reckon that if you can fab the exhaust parts to make a rear turbo fit, you can equally fab a manifold etc. for an engine bay mounted turbo.

The oil pressure in your engine will start off high when cold (forget what but about 80psi springs to mind for my old M20) and drop to about 20psi at hot idle.

[327ire]

Thanks boys!

Heres the link Chris, ... http://www.e30zone.net/modules.php?name ... highlight=


Would it be a terrible idea to use some sort of metal piping back to the engine for an oil supply? It would mean that the hot oil coming from the turbo to the engine would have a chance to cool down under the car.


Im using a CT26 from a 1992 ish MR2 or Celica GT4. Its intake has two openings, does this mean I could do the above trick with the A/ R housing?

[Turbo-Brown]

Think you'd have to measure the pressure drop across the pipe, and also come up with a way of getting oil from the back of the car up to the sump again.

[Gunni]

What did I say about over complicating.

[Turbo-Brown]

Some people (myself included) learn best by giving things a go though dude, and while I don't personally see any advantage to having a turbo at the back of the car, there's no harm in somebody trying I guess

[fuzzy]

does the oil have to be from the engine? what about a reservoir, oil cooler and small electric pump at the back of the car near the turbo ?

[e30_Turbo]

I've seen one setup that had the oil feed/return plumbed into the diff.

No idea on what oil was used though.

[327ire]

This is the setup iv been using...

12v pump in the boot slightly above the turbo, feeding towards the turbo, from the turbo up to an oil cooler above the pump (also in the boot) and into a tank (coolant reservoir from a mk2 golf) then back to the pump.

Theres a possibility that the oil was pumping the wrong way. Il have to check it. I think Iv set it up to pump into the larger of the oil pipes in the turbo... (iv learned the larger is probably the exit pipe )





Specification

Volts: Available in 12 or 24 volt. Please note we automatically supply 12 volt unless 24 volt is specified when ordering.

Pump ports: 3/8 BSP with brass connection for 14mm diameter tails (will fit 14mm inside diameter tubing)

Self priming: 1.5 metre

Pressure: 2 bar (29psi)

Flow rate: 14 litres per minute (3.7 gallons per minute)

Power consumption: 5-6 amps

Fuse rating: 10 amp. This pump must be fused, if the system becomes blocked the motor would stall and the windings would over heat

Size: 163mm x 166mm x 95mm

Weight: 1.4kg

Construction: Bronze gears, brass pump body with stainless steel shaft and ball raced motor.

[327ire]

This idea of only using one of the two exhaust inlets to the turbo seems great. Some people are simply blanking off one of the inlets, some are setting up a pressure sensitive gate to the second inlet once the boost has been reached in the first inlet.

Anyone know how the gated one is setup?

[Turbo-Brown]

Hang about, how does the oil get back up to the resevoir?

Does the pump force oil down through the bearing cartridge and then back up again?

That's probably not great for the seals on the turbo.

With the gated setup shown there, the pressure signal line would presumably be plumbed into the air outlet of the turbo so that it's boost regulated. You'd get some very turbulent flow from that wastegate though.

[appletree]

Matts Dad here
Looking at your lube set up, gut feeling is that your pump pressure is ok but litres per minute is a bit excesive, if you can't realise the flow due to back pressure your pump is going tom have a hard time! Also without some forced cooling (fan) the oil cooler is unlikely to dissipate much heat. Not knocking your efforts just offering points for consideration, stick with it learn and enjoy. Learn and be wiser, after all failure is just another chance to succeed. Phil

[327ire]

Thats correct, is there a problem with the fact that the oil is traveling up against gravity to the cooler?

Would the pump be better to draw oil from the turbo instead?

[327ire]

Iv ducted air from the side of the rear bumper and i have a 12v electric fan that can either suck behind the cooler or blow towards it.

Im loving the feedback bty. Its all constructive so keep it coming! Appreciate your time!

[Turbo-Brown]

Yeah the oil really needs to be able to freely fall out of the turbo, but the turbo also needs a pressurised feed.

I've seen a piccy of a setup which has oil fed to the turbo from the engine oil circuit but has a scavenge pump to take oil from the turbo back to the sump as the turbo was mounted very low down.

Kinda similar to what you've got, except you still need the pressure feed pump.

[327ire]

So if i was to take a pipe from the engine to my turbo (pressure feed) and use a pump to get it back to the engines sump,... would that work?

Maybe I could use a metal pipe back to help with cooling the oil.

[327ire]

Sorry, uv already answered that!

[appletree]

Matts Dad again
Keep the pump supplying pressure to the turbo, the back pressure is from the restriction of the ports in the turbo and the pipework (length/cross sectional area, the backpressure due to gravity is neither here nor there. Phil

[327ire]

Thanks phil. It could be a case that iv just hooked it up wrong, the pump feeding the turbos exit oil pipe. Maybe it just needs to be reversed, and possibly a pressure valve just after the turbo spilling the excess oil back into the reservoir.

[baptie0]

hi
i think you should make a new oil container and mount it below the turbo. the pump then feeds the turbo from here and the turbo can drain properly. a cooler is not required, just experiment with different amounts of oil to control the temp.
interesting project, good luck.