what turbo?

[bigkev]

what turbo do you guys recommend for the M50 2,5 .not looking for stupid power maybe an extra 60-80hp

[Jon_Bmw]

Holset hx35/40. The 40 being fairly well specced for a 24v 2.5 i would have thought. So a 35 would give you more torque and reach 280bhp without any issues i would think. The larger it is the less back pressure(depending on housings) which is only a good thing. Have yet to see a broken Holset.

[bigkev]

where would i get such a turbo

Cheers

[Jon_Bmw]

You see them floating about on ebay at times, but i believe they came on a dodge cummins diesel truck or something of that nature. An american vehicle mainly. Got to be a bit careful of import charges, the Uk decides it can rinse its citizens a bit more when they buy other nationalities products.

[e30_Turbo]

If you're able to live with that power limit you could use a much smaller turbo, as Jon stated it is better to have the a larger turbo as it works less to produce more but the flip side is it works later in the rev range and I can appreciate some people do want the off the line performance.

My original GT3 would give full boost @ 2.3k and pull well to over 6k @ 7 or 8psi, thats around 250/260bhp at the crank, I was stuffing all kinds of cars at the traffic lights but as the pressure went up over 15psi ( Boost greed ) I lost the top end and would lose 4 to 6 psi over 5k.

The deciding momment for me was a 30-110mph pull against a Audi RS4, I kept with him to 95ish and then it was like I was going backwards I was gutted but on the way home I hatched a plan

I can put some of the loss down to the downpipes having many flow problems and two boxes in the system but you just need the compressor map to see where it all goes out of effeciency.

Ants A-Tech custom spec T3 is as big as they go and that aint shy, boost at 3kish and holds all the way, so maybe something similar would be ideal.

Holset's a great and I would highly recommend one but I have to say they aren't for everyone and a few people stateside have gone back to smaller units to get the low/midrange that most people use everyday.

HTH, Mark.

[Turbo-Brown]

We need someone to do a twin sequential setup

[e30_Turbo]

We need someone to do a twin sequential setup

Like a small into big, best of both worlds?

I can't get my head round the way it switches, something like a wastegate in the exhaust switching at a set pressure or controlled be ECU?

And wouldn't you need quite a complicated manifold to do that also?

Mark.

[bigkev]

We need someone to do a twin sequential setup

tell me more

[bigkev]

a bit like the toyota Supra

[e30_Turbo]

the 3ltr twin turbo is sequential, just ask my mate who lost his on a roundabout when the 2nd one kicked in and sent him down a ditch only to write the car off! 7k car with 7k's worth of bits and he could only afford a e36 325i when the insurance paid out

[Turbo-Brown]

Think the 3rd generation RX-7 had a twin sequential turbo setup and I seem to recall reading about the so called "snakes nest" of something like 47 individual pipes that control the turbos......but surely if can't be that difficult!

Anyway, the jury's out on how one activates the other (or I've never bothered to find out anyway).

To my mind, you'd want the small one to spool up and then for the larger one to be blended in untill the small one's not doing anything.

Can think of a couple of ways of controlling the flow of exhaust gas but I think the control strategy would be a bit of a head scratcher.....then again anything's possible with computers so no doubt someone could come up with something!

As for the manifold, I reckon it'd need to be either 6branches going into the diverter from where exhaust gas is sent to the required blower, or a simple log style manifold with both turbos receiving gas via one valve each so that they can be switched on or off in effect.

I'd say the mechanical actuation could come from a simple pressure capsule much like a normal wastegate which would mean that it could be controlled by the ECU using a solenoid valve which, thinking out loud, could have it's signal based on engine speed/manifold pressure.

Think if it could be made to work you'd have an absolute monster of an engine which can deploy full boost in any gear and at almost any engine speed

[dan_emaps]

Think the 3rd generation RX-7 had a twin sequential turbo setup and I seem to recall reading about the so called "snakes nest" of something like 47 individual pipes that control the turbos......but surely if can't be that difficult!

Anyway, the jury's out on how one activates the other (or I've never bothered to find out anyway).

To my mind, you'd want the small one to spool up and then for the larger one to be blended in untill the small one's not doing anything.

Can think of a couple of ways of controlling the flow of exhaust gas but I think the control strategy would be a bit of a head scratcher.....then again anything's possible with computers so no doubt someone could come up with something!

As for the manifold, I reckon it'd need to be either 6branches going into the diverter from where exhaust gas is sent to the required blower, or a simple log style manifold with both turbos receiving gas via one valve each so that they can be switched on or off in effect.

I'd say the mechanical actuation could come from a simple pressure capsule much like a normal wastegate which would mean that it could be controlled by the ECU using a solenoid valve which, thinking out loud, could have it's signal based on engine speed/manifold pressure.

Think if it could be made to work you'd have an absolute monster of an engine which can deploy full boost in any gear and at almost any engine speed

Too true, the RX-7 is reknowned for its sequential set up, unfortunately not all for the right reasons, reliability can be quite an issue. Most Rex owners either go for a larger single or stay twin but non-sequential.

To be honest i can't see the need for a sequential set up on a m20, it works well on the RX-7 as the rotary units are lacking in torque, but not really a prob with the m20, i'd imagine it would cause more hassle than what its worth, but an interesting idea

If your only after 60 odd bhp a T3 should be fine dude.

[Turbo-Brown]

Yeah think for a small gain it'd be pointless going twin sequential, but if you wanted big horsepoos from an M20 say, I reckon there could be some real merrit to the idea.

[mattG]

i use to have a subaru legacy 2.0ltr twin sequential turbo, i think they were controlled by the ecu driving a multi solonoid box with many vacume hoses ( 8 i think) comming out of it and then connected to the 2 turbos,

although must serious boost junkies in NZ would didtch the sequential setup and run them together or go for one big turbo,

i had no problems with mine in 50,000klm had a remap 320bhp could not feel the 1st turbo really as it came in at 1500rpm but the 2nd cam in with a thump @ 4000rpm before the remap it was a bit smoother,

the pipe work on the scooby flat four was like a can of worms but it did sound nice with those unequal length manifolds

[WillG]

the 7 second 1600 hp e36 M3 by VSmotors uses squential turbos on a s54, should have a look at that setup

[Gunni]

the 7 second 1600 hp e36 M3 by VSmotors uses squential turbos on a s54, should have a look at that setup

It´s a S38 afaik

[WillG]

yeah always get mixed up with that engine for some reason, not sure on the exact power either

[320Touring]

If I was gonna go to the bother of fitting twin sequential turbos, i'd just do compound charging

supercharger for the lowdown grunt and a big turbo for the uptop

[Turbo-Brown]

If I was gonna go to the bother of fitting twin sequential turbos, i'd just do compound charging

Just create a compound charge setup? :p Not sure how the controls work out for that or if they'd be any easier than a TST setup?

Personally not all that keen on having a parasite living off power that could be propelling me along but I can see the attraction of having near immediate boost off idle.

Of course turbos do represent a restriction to flow, but at least they live on energy that would otherwise be completely wasted.

[lentec]

Woooo did i hear compound charging? im half way there all ready

As for sequential turbos:
Quick googling found this

Great idea but is there enough room for the pipework needed on an e30?

[Turbo-Brown]

Yeah easy peasy poo.

Reckon you could make the exhaust plumbing quite compace with a bit of planning and there's definately enough room for two turbos under the bonnet

Love the way they assume no gas will find it's way through the little turbo when the valves open.

Does explain how the turbo's boostings are blended into eachother.

Quite intrigued by this idea now, if only I had some money and things didn't keep breaking and needing replacing!

[bigkev]

think i will stick to single turbo for now