'90 320i SC project, need help please

[diogo]

hello

I've been lurking in the dark for awhile untill I decided to make my first post here.
I've read alot about the supercharger conversions done here on this forum and found the information really helpfull, although the majority of the conversions are applied on the M20B25 engine.
Being a proud owner of a euro '90 320i Mark II M20B20 (forgot to mention that I live in Portugal and at sea level) I was curious to know if a Eaton M62 supercharger (the one dubbed as Kompressor and found under the hood of the Mercedes 200 K) is the right choice for my engine capacity. I don't plan to go too extreme (at least for the time being) and since this is going to work as my guinea pig I plan to learn from my mistakes.
My aim is to have a street legal, daily commute but entertaining enough in a trackday car with +/- 200 whp. I was told that could be easially achieved with the M62 S/C, an I/C and a FSE fuel pressure regulator.
Anyway any input on this is valuable info for me.

thx in advance

Diogo

P.S.: Please don't start a turbo vs. S/C war on me cause I've already made my mind ;)

[Erick]

Being that the engine's are of similar displacement (I believe Benz uses 1.8l), and you have two extra cylinders in your advantage, I believe that the Eaton M62 will be a good choice for your car on a low boost setup (as Mercedes uses it on their 200 and 230 cars)

It will be tougher to install a supercharger than a turbo though. I'm not here to promote a turbo/supercharger war, but as much as I'd love to see an M20 supercharged, I'd just like to make sure you know what you are getting into.

- Erick

[diogo]

Yeah I aware of that, but I was thinking of relocating the batery to the trunk and I already got rid off the power steering and my car doesn't have air con, so that makes a little bit more room on the engine compartment right? oh btw you were dead right on quoting the 200K as being a 1.8. Another thing poped into my mind (I need to stay away from the internet :-S) I read somewhere that a M20B25 would drop the compression ratio of my engine, wouldn' that be a good match with the supercharger? I mean I have a faster revving engine than a 2.5 but with a better airflow head and bigger throtle body, getting a MAF sensor from a bigger engine (M50 perhaps?) would that work?

thx again for the input

Diogo

[Erick]

Well, before you get too ahead on plans, you have to tell me how you are fitting a twin screw supercharger on an M20 :p

I'd like to see the manifold design because it'd probably going to require a lot of skill to weld the manifold together. I had my manifold custom made, and it was a pain for the guys to weld since our manifolds are not pure aluminum.

[diogo]

Can't I use the stock manifold and pipe route it to the S/C!? almost all the E30s that I've seen using a S/C had stock manifold headers why should I need a custom made one?

[diogo]

sorry, perhaps you were talking about the S/C intake right?

[Erick]

sorry, perhaps you were talking about the S/C intake right?

No, I meant the supercharger itself will require a whole new intake manifold.

There's different types of superchargers. There's centrifugal, twin screws, etc. The eaton M62 is a twin screw. If you look at it, you'll instantly see what I'm talking about. Unlike the centrifugal (or turbochargers or that matter), there is no compressor housing (snail) where you can just add a coupler and piping to direct it to the throttle body.

The twin screw is designed to bolt on directly to an intake manifold. The easiest way to put it is that it will become a part of the intake manifold itself. Even the throttle body will now have to come before the supercharger itself.

Seems like what you are looking for is a centrifugal supercharger, which is a lot like a turbo (in shape). It would be much easier to bolt on, take much less fabrication, and you can use piping to connect it to the throttle body.

[diogo]

a G alike supercharger right?

[diogo]

and thx once again for the advice before I fooked things up ;-)

[Erick]

No problem. Like I said, I'm all for an M20 supercharged (if you really want to be different), but beware of how much work is ahead of you.

Ignore this if you want, but personally? Grab a T28 or a GT28R with a small turbine housing. Your car will spool so fast you won't even notice it's turbocharged. I drove an RX-7 with a 2.5l I-6 turbocharged by a GT28R and I had full boost right from the start.

If you don't have plans for 450-1000hp, then that's the best setup to go with.

[diogo]

but don't I need to change engine internals for that? new pistons, head gasket, new oil return lines fron the sump, etc etc? that's why I was thinking S/C becaue of cost effectiveness, hassle free job (now that you explained the centrifugal principle to me) and quick throttle response. If you can prove me wrong I would hapilly change my mind...(this goes against my first post tho :-S)

[Erick]

Boost is boost. Whether you are achieving it by a supercharger or turbocharger, the same pressure will affect the motor the same way. So 8psi on a S/C will affect your motor the same way as 8psi on a turbo will.

Now, there is a lot more support for M20s with regards to turbocharging that supercharging, because it is that much easier. The main problem (once you solve the mounting issue) with a S/C is that you will have to custom make a crankshaft pulley to run the belt.

I don't know the internal specs of the M20B20, but it should easily take 7-9psi, which is a nice setup that will probably get you past the 200hp mark.

- Erick

[diogo]

back to the 'charger question, I was told that you could attach a "double elbow" pipes from the bottom of the Eaton S/C and have one going to the intake manifold and another one to the I/C and it would still work like it should, that's what guys that ditch their G40 and G60 centrifugal chargers from VW in favour of a more reliable and cheaper alternative like the Eaton.

[Mako18]

^whats the point off that? why make things harder?


Where are you mounting the s/c? What exact s/c are you using?

I know your using an eaton (roots) based s/c. If its the m62, just fab a plate to mount to the outlet of the s/c, cut a hole something around 3", 3-1/2". weld a 90 to the plate you made, pipe in the i/c then to the intake manifold. After mounting its just like a turbo, just a bit more work to get the belt drive perfected.

As far as mounting goes I would personally make a completely new intake manifold with a built in air to water i/c. keep it neat!! but that may be a little much for the average DIY'er.

Look here for more info. Its not impossible just take a little skill. not much though..

http://www.e30tech.com/forum/forumdisplay.php?f=40

[Mako18]

The main problem (once you solve the mounting issue) with a S/C is that you will have to custom make a crankshaft pulley to run the belt.
- Erick

If its the same pulley as a m20b25 then you can use one off a dodge durango if I remember correctly and its bolt on!! However I would still make a custom 2pc crank pulley with a center hub and outer ring this way you can have multiple outer rings to overdrive the s/c thus increase boost. You do this when you can't mount a smaller pulley on the nose cone of the s/c. The m62's smallest pulley is 2.75" unless you machine the cone...moot IMO... I would then start using the crank pulley to increase boost.