Twin Seq. Dry sumping for beginners :D

[Turbo-Brown]

Happyness and joy, will mine be the first E30 to feature not one, but two Holset turbos?

Cheers to Fozz for the heads up on a dinky little HX27 which set me back the princely sum of £90! Gotta love the brand anonymity of Holset, God knows how much the equivalent Garrett would've gone for.

So, here's the spec so far:

2 Door shell (to have it's diff mount reinforced!)
2 Litre block to be bored to 84mm
2.9 stroker kit from Ireland Engineering featuring forged crank, steel rods and forged pistons (it'll work out at 2791cc if I keep the bore to 84mm instead of 85mm)
Holset H1C
Holset HX27

Be interesting to see where this leads!

Cheers!

Alex

[Dan318-is]

[m-dtech]

hmm nice twin turbo beast. !

[Turbo-Brown]

Nothing like making things excessively complex is there?!

[E30BeemerLad]

are you going for sequential spool up then old chap?

nothing like 2 shovs in the kidneys

[Speedtouch]

Why the use of a 2-litre block, out of interest - so you can use a 731 head?

[Turbo-Brown]

Gonna use a 2 litre block bored out to 84mm which is what the 2.5 blocks start out as.

That way I'm guaranteed parallel bores which are cut into fresh metal instead of having to get a 2.5 block honed or finding out that the spare 2.5 block I have is beyond just a hone.

Keeping to 84mm means the cylinder walls stay reasonably thick too.

It'll be interesting to see how the system I have planned works out. I'm probably way off the mark, but I'm hoping for more of a big engine effect than the traditional turbo punch if that makes sense.

Figure the only way to find out if it's possible is to give it a go

[Speedtouch]

Sounds like a cool project dude - best of luck!

[WillG]

making and controlling a valve to bypass small turbo on WOT is going to be the hard bit i think, could you just use a wastegate and put exit into pipe going from small turbo to big one? Would still need one between turbos aswell tho to control big turbo i think

[E30BeemerLad]

look at what the setup is on the Supra TT lump, the 2JZ-GTE engine
a look on www.mkivsupra.net will probably take you to some technical info on this engine and turbo setup.

[fuzzy]

quality mate are holset turbo's generally that cheap?

[Turbo-Brown]

I've got a good idea on how I'm gonna control them, will do a sketch at some point so you can all laugh

The difficult part is controlling air into (or out of) the turbos rather than exhaust but I've got a reasonable idea on how to overcome that little doozy too

I'm not keen on the idea of having a conventional wastegate to divert flow between the turbos as they'll be massively restrictive I feel.

I've only really got the two Holset's that I've bought as a grid of reference Fuzzy, but the bigun' cost me £215 including shipping and the little one was just under £90 which for brand new turbos is insanely cheap, especially when they're as well made as Holsets

[WillG]

right , i guess you need some kind of non return on compressor exits or you will get your boost braking (slowing) the other turbo down?. A wastegate before both turbos exiting in between, a 40-50mm wastegate combined with what the HX27 can flow should be enuff, I dont know what other type of valve will work under that much heat and not leak?

[Turbo-Brown]

Problem is that you need all the gas going to the HX27 to start with and going through a WG would involve the gas doing a sharp 90degree bend.

I plan to make up a twin 6branch manifold which has six fairly hefty divertor flaps which effectively blank off the H1C at lower engine speeds.

These will also form the WG for the HX27 in that they'll be moved by a normal actuator so as boost gets high enough the wasted gas will be allowed to get to the H1C so starting to spool it.

In addition, the gas from the exducer of the HX27 will also be diverted to the inducer of the H1C so that all exhaust gas must pass through the H1C at some point untill it's doing it's thing.

The external WG for the H1C will be held shut until such time as high boost is reached which should only be when the H1C is going properly.

I will indeed need some sort of valving in the inlet which prevents boost escaping. I believe that a large Butterfly valve may present the solution to this which again should be controlable using a pressure capsule under the direction of the ECU.

I'm not concerned about a small amound of leakage from around the spindles of the divertor flaps, only that they don't sieze up!

[maxfield]

Sounds an awesome project

[WillG]

i dont mean having all exhaust going throught a wastegate, what i mean is you have a normal manifold and wastegate, to start wastegate is closed and all gas flows throught HX27, the HX27 turbine exit is connected to the H1C turbine inlet, then when HX27 is spooled the 1st wastegate opens and bypasses some of the gas into the pipe going from HX27 to H1C. The flow from wastegate and throguth 1st turbo should be enuff to not cause any backpressure.

[fuzzy]

I've only really got the two Holset's that I've bought as a grid of reference Fuzzy, but the bigun' cost me £215 including shipping and the little one was just under £90 which for brand new turbos is insanely cheap, especially when they're as well made as Holsets

certainly beats the £800 i paid for my low to middle of the range stage 2 garrett t34

[WillG]

like this, i drew 2 wastegates too close but they are not connected atall, i dont think butterflys/flaps will be any good in an exhaust system

[Turbo-Brown]

Here we go, the first sketch of many! Don't smoke so I have no fag packets to draw on

Don't all laugh!



I reckon this should represent relatively low restriction to flow being effectively a 12 branch manifold

[m-dtech]

pity you didnt have two HX27s one for cyls 1,2,3 and another for 4,5,6

[JaMMi]

I pray that one day this means something to me.

I do know one thing. This is DEFINITELY "freakin' awesome"



Nice concept ; good luck!

[Turbo-Brown]

Think two two of them like that would be veeeeery laggy indeed. I've got two little T25s set up on 1-3 and 4-6 at the moment which works quite nicely, but despite them being ceramic, there can be a long wait for boost.

The aim with this setup is to eliminate lag as far as possible and yet still retain an extremely strong top end.

[liam012]

my way looks better but i thinkthe manifolds could be restrictive....

[Turbo-Brown]

like the way there's money pissing out one side of the engine, adds that touch of realism

[Simon13]

can you not gleen info off the spec of a Alpina Bi turbo M30 lump? or BMW's 535d lump. If i'm getting you right youre having 1 small turbo for low mid range and the the big one for mid and top end? At the top end the small turbo is fazed out and low down the big turbo is spooling up like a banshee!

sequential rather than a turbo each for 3 cylinders?!

[Turbo-Brown]

Yeah, will have to have better look into what the pro's have done but in essence yeah, one small tubby for lower engine speeds and one massive one for higher speeds.

There's the added advantage that the more the little turbo blows, the exponentialy more exhaust gas becomes available to spool his big brother.

The extra 300cc should help out too

[dom-1984-320i]

Sounds like a great project! lookin forward to seeing some pics whe you have some, good luck with it all mate.

[liam012]

sorry i coiuldnt resist
on a serious note when i asked for my 2 litre block to be bored out to 84mm i was told "are you kidding mate?, on 6 cylinders, do you rrealise how long that would take i would be blue in the face from looking at the machine"
also do the bores then need to be sleeved? if so where do you get sleeves?
and the stroker kit for the money just has to be ridiculous good value -
can they work with you regarding the compression ratio/piston size/bore? or is it a set kit?

[WillG]

link

This is BMW's new "BIturbo" setup, looks like twin to me, isnt sequential

[WillG]

dodgy

[Andy335Touring]

Jeezus, you like complicated projects dude !

[Andyboy]

Gonna use a 2 litre block bored out to 84mm which is what the 2.5 blocks start out as.

It does work but they are different castings to begin with - the 2 litre and 323i have '80' cast into the blocks, 325i's and Etas have '84'. I'm not sure if all 2 litres have the small steam holes but no matter - it'll work. It's worth hanging onto these 2 litre blocks!
Rather than an expensive Ireland crank, you could use a 330d crank (88mm for 3 litres with an 84 bore) or a 525tds crank with an 82.8mm stroke (about 2750cc). Both are forged steel.

[Turbo-Brown]

I think that the longer the throw you end up with, the shorter the rods will need to be which ain't so great for power.

Is that a Pug engine Will? Dodgy looking though that setup looks it's a good way of extracting massive boost from a turbo (the second in the system) as the second multiplies the boost of the first.

The bores shouldn't need sleeving, unless they go too far that is, but that ain't my problem. I trust my local machine shop to do a good job too (assuming they're still in business!)

[jkarran]

Might also be worth a look at RX7, Supra (sequential or twin?), Legacy (RS or typeR? - an import one anyway) and I think Lancia did sequential turbos on some of their 80's homologation specials. The RX7s sequential setup is apparently quite unreliable in getting the second turbo to spool up, I'm not sure why though.

Those exhaust diverters will be a nightmare to fabricate. What are you planning to use, Inconel? Rather you than me.

That engine pic above looks well dodgy No wastegate (that I can see) and all the flow always passes through the first turbo?

Cool project

jk

[bootyman]

Sounds like a fat engine if you can get it to work, but take your time cause you might be the 1st with twin Holset Turbo's, but you're way behind on the twin turbo in general thing. I've seen a Zoners car which has twin turbos, individual throttle bodies and 100bhp of Noz directly tapped so there is no lag what so ever and over 500php. I was looking at doing something like it, but was put off by the huge price tag, so stuck to my 2.7 engine. I just have to persuade him to post a couple of pics up