Superchrged M20 Project

[carannc]

After building a M20B28 and getting 209bhp i am thinking about what it would take to get 300bhp for a rally engine, very limited mileage about 2000mls / rebuild, so..

I would like to build a supercharged unit over the winter and want to start sourcing parts from now on.

I have a M20B25 bottom end and can get a refurbished std head but can i get to 300bhp with OEM bits ? - what cam ? oil pump ?

already have MS and a 6 branch from hot tuning, exising cam is a piper 270.

Anyone done this before and can get me started.

many thanks

[rix313]

I know some one used a Eaton M62 charger from a Merc SLK to a 6 pot. The other option and probs the best one is to use a rotrex charger.

There's an epic thread on Rotrex chargers in this section defo worth the read if you feel you'd like to go that option.

[carannc]

will price up a used merc charger for starters then, cheers

[e301988325i]

randomdave325 on here has built a high power supercharged m20, he works at fritz bits
http://www.fritzbits.co.uk

[GeoffBob]

Any idea which type of supercharger you have in mind? Roots (Eaton), Centrifugal (Rotrex) and Lysholm screw (Sprintex) type pumps are all very different beasts, each with their own set of advantages and disadvantages. I'd suggest you read up/google/wiki each of them to decide which would be better suited to your application.

An Eaton roots blower is a great choice for improved low down torque and the Eaton website has a full set of compressor maps for their range of blowers. Roots blowers are however quite inefficient and put a lot of heat into the air they pump, so be prepared to have to do something about this! So far as I am aware, roots blowers are seldom used on rally cars unless accompanied by a turbocharger to supply increased boost at higher RPM. The Lancia Delta S4 was one such rally car.

If you are set on fitting a roots type blower, do consider a Lysholm screw instead before you fork out any money. Lysholm screw blowers offer similar boost at same RPM to roots blowers, but are much more efficient, and thus put less heat into the air they pump.

However, if you want something that provides similar-ish boost characteristics to a turbocharger, then consider a centrifugal blower (Rotrex).

[carannc]

Thanks - i really have not considered the type of blower and of course i need sustain high power for off road applications so i guess an intercooler is going to be necessary.

Sounds like a Rotrex is the way to go...

[rix313]

Mr Appletree who has fitted a R'trex so his 318iS (m42 engine), from what I've read (so correct me if i'm wrong) has had issues with his FMIC loosing sums of PSI dispite claims of minimal lose. I fitted a much smaller one for my Eaton charger so will see how I get on when I get round to fitting it.

Charge cooling (using water) is very efficient but requires a tad more fafing as it's obviously a little more complex with the water etc.

[stonesie]

Appletree found that the sums of pressure drop were mainly down to his pressure gauge holding the peak value and encountering a pressure surge before the IC when he lifted off the throttle, due to his Dump valve being after the IC.

When he modified his test method he got much better results, in the words of the man himself ....

"Gauge at plenum (after intercooler, throttle and dump valve)

2000rpm = 0.15bar
2500rpm = 0.2bar
3000rpm = 0.3bar
3500rpm = 0.35bar
4000rpm = 0.4bar
4500rpm = 0.5bar
5000rpm = 0.6bar
5300rpm = 0.7bar

Gauge at rotrex outlet

2000rpm = 0.1 bar
3000rpm = 0.2 bar
4000rpm = 0.4 bar
5000rpm = 0.6 bar
5300rpm = 0.7 bar


Wondering if the dicrepency at the lower RPM's could be due to surge and the gauge not being quick enough to react?"

[GeoffBob]

Thanks - i really have not considered the type of blower and of course i need sustain high power for off road applications so i guess an intercooler is going to be necessary.

Sounds like a Rotrex is the way to go...

Have a look here at the work I have been doing with appletree: http://www.e30zone.net/modules.php?name ... c&t=134925. Don't let the maths put you off, Appletree asked, so I posted it up for whoever is interested.

So long as you have a compressor map for your chosen blower (regardless of whether it's a roots, centrifugal or Lysholm type) I can help you decide if its a match to your engine. (I do this for my own ammusement, I am not a business).

And yeh, Appletrees intercooler is just fine!

Appletree had an Eaton roots pump on his engine before he switched to a Rotrex (and BTW I'm not saying one is better than the other, they both have their applications). Maybe he can tell you of his experiences with each himself?

Geoff.

[rix313]

Thanks for putting me sqaure on the FMIC info

[BigBavarian]

I have an m20 2.7 with an eaton m90 supercharger off a db7, ant has done some of the work, soemone else some more, now in my hands to finish off. When i go he car it was running but not well, but it went like stink! Recommend the m90 supercharger and they are peanuts off the bay!

[ShakeyC]

Supercharger kits already developed for the M20 see the link below.

http://www.fastbimmer.co.uk/projects/pr ... otrex.html

[kingcruizer]

^^^thats my engine