power from a M50 B27 supercharged

[dicko]

What power would you expect from a m50 stroked out to 2.7 running about 7 psi of boost .
The c/r will be dropped to 9.75 so would I get away running a little more boost .
remember the sc uses about 30 hp at full speed so that will take the power down a bit.

[Gunni]

I´d say 285hp or so.

[appletree]

How do you get a M50 2.7? Do you mean M20? I'm runnin 8psi on 10:1 cr to give you an idea an that added 70bhp to my 1.8 16v

[dicko]

you get a 2.7 m50 using m51 2.5 tds crank and m20b20 rods with m50b25 pistons ( I think that is using info of the net so will believe it when its done )
It will actually be closer to 2.8 and 9.75 c/r so maybe I would get away with 9 psi of boost.
An extra 70 bhp from a 1.8 thats impressive bet that car is quick.
What charger are you using and are you using a intercooler.

[appletree]

its a eaton m45 off a supercharged mini bit small which is why i'am upgrading to a rotrex and hopefully another 100bhp with propper low comp build and making everything stronger.

Not intercooled it i didnt have room so i made a charge cooler that fits in the manifold the inlet air temp was 70c before anf 40 after still abit high but alot better.

the roots type chargeres are crap only aroun 45-55% effeicent as apposed to 75-80% from the new rotrex chargers

[dicko]

I dont like centirfugal type blowers the way the boost comes in I am looking for boost low down not to bothered about top end , I would love a twin screw blower but cant find any cheap. I am going with a charge cooler in the manifold as well thinking of using a cut down rad .
Roots type are a bit old fashioned but they sound nice .
Would you think of turboing your car and do the rotrex need an oil supply.

[hongkongfuey]

couldn't you just use an m50 iron block with 2.8 internals???

[dicko]

I would but cant find a 2.8 crank over here and the pistons have to have a teflon skirt as well I dont think nikasli engines have these .
There are loads of 2.5 tds engines here and they have nearly the same stroke as a b28 and will lower my c/r
What injectors are you using Appletree and what sort of duty cycle are they up to at full power

[ShepsEvo3]

I dont like centirfugal type blowers the way the boost comes in I am looking for boost low down not to bothered about top end , I would love a twin screw blower but cant find any cheap. I am going with a charge cooler in the manifold as well thinking of using a cut down rad .
Roots type are a bit old fashioned but they sound nice .
Would you think of turboing your car and do the rotrex need an oil supply.

The Rotrex needs its own oil supply. There is special oil used too. I would also advise an oil cooler just for the charger aswell, I have seen failures with systems without oil coolers.

Yes, the way the Rotrex works is centrifugal, ie more boost with RPM. Its not a bad idea as it is nicer to the engine, and the car is much more driveable. However, I am sure there is a way of sizing the charger pulley so that boost comes in very low down and using some kind of boost controller/relief valve which can then keep the boost to a desired setting.

[Gunni]

For me , If I where even to install a supercharger, let alone a centrifugal one.

I´d size the pulley so that boost builds with engine speed and no relief valve.
Especially in a way that 4-5psi is possible at 3k, at peak torque and after that the engine breathes in more per cycle.
That means even as the charger keeps raising it´s rpm in ratio with the engine the boost delivery slows down as it reaches peak torque, then after peak torque boost would start rising again, not much but little,

I´d say 3k - 5psi
6k 10psi , no issues on any stock bmw engine made, aside from the very high compression ones.
Maybe even 7psi upto 14psi.
Or just jerk the thing to 14psi and a massive relief valve , depends on what one want´s

[dicko]

I think I would turbo before putting a centrifugal blower on it as the power delivery is similar and I would think using a relief valve to limit over boosting would waste a lot of power,
Why are VNT turbos not used on petrol engines is it because of the higher Exhaust gas temps or something , they are great on diesel engines

[Gunni]

the vanes on the vnt ones can´t handle the heat, unless some ultra material,
which makes them very expensive.

[dicko]

Thats a shame they are great.

[dicko]

I wonder would a Whipple 140 ax be to big for my 2.7 m50 .