Should I? Could I? Twincharger

[pilt]

Hi,

So heres my toy (and daily driver!), 325iSE Facelift with Holset H1C turbo. Im too embarased to show a full photo because its Brilliant Pink at the moment with 3 years of no polish!

Anyway, heres my dilema. The turbocharger is all nice but theres no real power from the turbo below 3000rpm. Now the gearing isnt that bad so its not hard to keep it above 3000rpm, but there are occasions where i think I dont want to change down.....

It just so happens I have a brand new mini cooper S supercharger laying around (with fancy teflon coated rotors) and there is a nice big gap there in the engine bay that looks just about big enough for it..... Im really not sure if the supercharger is big enough, but going on my awful calculations im guessing if i use it only upto 3000 rpm then declutch it, it only needs to supply enough air for a 1.25 litre engine (im sure it doesnt work like that!!)

So what do you reckon? Mad idea? Or First twin charged E30?

[Rav335uk]

You sure that'll work, turbo and charger??

[pilt]

Yeah,

VW do it on their twincharger 1.4 and Lancia did it on the intergrale rally car!

Something like this I was thinking:



With an electronic clutch on the S/C to diengage it at >3000 rpm.

THe electronic throttle body would then open at the same time to supply the turbo with air.

[rix313]

Sure can be done.

If you look, Geoff bob has done some calculations for fitting on to an M42. I know you have an M20 but still be worth a look as it's very informative. The Eaton will provide you with some brilliant low down torque until the turbo kicks in and goooo.

Mounting it how ever is the reason I decided to go Rotrex.

[appletree]

Agree with rich here that would be almost imposible to get a good enough mount to the charger from the engine block, also i think you may find it hard to get a path for the belt, and you'ud need a long belt.

there was some one on a scooby forum that mounted the charger on the car body and used stiff engine mounts and a fancey trensioner not my idea of a reliable set up but if it works....

[jimmyspeed]

good luck if you go for it as mentioned before lancia liked doing this and the s4 (see avatar) had it to- sick car

would be very cool having a torque and top end would make a good combination , but matching the boost , belts, bypasses and all that technical stuff will be a right mission

[baptie0]

looks like space is going to be tight.
could the charger fit on the offside of the engine down below the turbo?

[JWaller360]

Would love to stick a boost gauge on mums TSi golf, the boost never seems to end!

Been thinking about this a lot recently, need to investigate it a bit more, especially how it's installed on the VW and lancia, see how they differ.

Possible to use the supercharger after the turbo inlet, so that it acts like a primitive anti lag system?

[pilt]

Thats the thing, I wasnt sure which way round is best Supercharger or Turbo?. But the plumbing would be so much easier if the supercharger comes first (which is the way the TSI golf is I think) as its just one pipe accross the top of the engine to the turbo inlet.

I think that side is the best place for it, theres no room down the other side of the engine as the turbo manifold is split pulse type so takes up loads of room. Looking a bit closer it looks like it will fit by relocating the dipstick and removing the diagnostic connector and re routing the intercooler to manifold charge pipe to clear it.

I think one of the big problems is going to be getting the belt and tensioner setup all correct as I imagine that could be a big PITA. Can they be run with fixed tensioners or do they need to be self adjusting? Looking on the forums over at E30tech it looks like a m50 AC pulley can be used on the end of the M20 pully (instead of the PS one) to drive it. Can any of you M50 owners over here confirm if it looks like it will fit?

[GeoffBob]

Pilt, I already answered this one for you here

Lose the electronically servoed butterfly valve and fit a simple vacuum operated poppet valve. Works a charm with no fancy electronics required.

[MarkT]

Compoundcharging sounds like a cracking idea. Could you not run a small charger pulley and have it running all the way through the rev range, when the supercharger tails off the turbo will be coming in with some carefull mapping.. IIRC if you run the turbo after the supercarger, the supercharger will compress the air a second time.

[rix313]

m50 AC pulley can be used on the end of the M20 pully (instead of the PS one) to drive it. Can any of you M50 owners over here confirm if it looks like it will fit?

I'm not sure how the M20 and M42 crank pulleys differ but we've used an M43 crank pulley with the trigger wheel machined off. With the Eaton M45 (lots of M4* going on here ) pulley wheel being 65mm and the M43 crank pulley being 140mm, the charger is maxed out with an engine limit of around 6500RPM.

[Gunni]

I think the first thing to look at is supercharger performance curves on M20´s and to see what benefits in terms of gains there are over no forced induction. As most turbos make some boost from 2k onwards you´ll have to size things perfectly so that your not hindering the supercharger performance or the turbocharger performance.

The problem with M20´s is that they come on cam hard at 4k, and your working with two very different beasts on each side of the cam.

Also the supercharger will mostly just be a feeding device for the turbo as when you start boosting low down the turbo can come on full boost alot sooner and the supercharger isn´t needed. If your getting full boost now at 3500rpm from the turbo it could be down to say 2700rpm if you have a supercharger as well. Then you have to take into account how long time that actually is in terms of performance enhancement and how your driving style suits it. You might only be using the supercharger for 1-1.5seconds until the turbo is doing all the work.

What are the specs on your turbo now size wise. You might be able to just run a smaller turbo and maintain the same peak performance without all the work involving a supercharger and turbo install. Are you running electronic boost control ?

Do you have any hard data in relations to your current setup and the spool character?

[Chuntington101]

Compounding is the easiest way to go about this. The MINI guys have done it for years now.. So have the ford guysi n the US.

main problem is heat. You need to cool the air from the turbo before it gets to the supercharger. and then you need to cool the air again after the supercharger.

another problem is back preusre. i recently saw a LS2 running coumpound boost that had MAJOR back presure problems even though the car ran REALLY well with just the turbo on there! you need to run a BIG turbo. Id look into the holset stuff as they should run larger exhaust housings than most petrol engined turbos. Alternatively you could just run a BIG turbo. GT42 antone???

you are also going to need a REALLY good flowing weastgate! also make sure you position it where it wil have priority of the exhaust gas. this will help to reduce/eliminate boost creap. This is a comon problem in compounded engines and any boost spikes will happen alot faster (thanks to the turbo responce being soo much quicker with compound) and result in a destroyed engine.

There are advantages to a simple compound setup (turbo feeding Supercharger). first NO valves! im guessing your going to be doing it yourself so the KISS idea might be the best untill you test it. Only one air filter. again makes things a little simpler and means you only need to buy one! piping will be easier as from the pics you would only need to fab a aftercooler.

Sounds like a great project.

Cheers

Chris.