Turbo vs Super for M20?

[whitebulat22]

I'm aware the answer most of the time is Turbo, but 9/10 times I personally prefer supercharging. My plan is to build a 2.7i out of an 86 ES and down the road add whatever additional power I might want through a supercharger. It's so rare to see supercharged M20s I'm wondering about the pros and cons of it.

The pros for supercharger IMO are instant response and keeping exhaust volume which are so big for me I'm tempted to overlook the higher efficiency of the turbo process.

If all goes well I'm trying to fit the supercharger on the car along with standard preparations like head studs / injectors / megasquirt etc. If this can be done with a fair chance of keeping the kit under 3 grand via a used Eaton m90/m112 or something I will probably take the plunge, too much further and I'd rather be swapping in an engine that can reach 350 ish HP NA.

How often is this done and how difficult would attaching the supercharger + intercooler be?

[downforce22]

Not sure what you meant on the 'keeping exhaust volume' part.

Either way, it sounds like you need to identify your goals. Do you want more power? Highway cruiser? AutoX car?

There have been superchargers done before, read this thread: http://www.r3vlimited.com/board/showthread.php?t=306699

I personally don't see the appeal of the supercharger. The super charger is connect to the crankshaft and is constantly pulling the load off of the engine. This translates into wasted power such as cruising on the highway when the supercharger is not being used. I believe this can be upwards of 50 hp depending on the output of the engine. They can also 'choke' flow on the top end of the powerband. I would prefer to build a turbo setup with the correct components so as to minimize lag and optimize the system. Don't get me wrong, a turbo can also 'choke' flow at the top end.

I think some people rush into cobbling together used parts and don't spend enough time thinking about the entire system and how each piece will work together. I'm not saying you should consider going with a turbo, just that you should decide what purpose the car will have.

I want a car that can cruise on the highway, be used year round, and can be driven on a track. My plan is for a 325iX with 3.64 final drive, and a turbo setup.


Whatever you do, always research and learn more!

[whitebulat22]

I may be wrong and haven't heard enough turbo cars in person but it seems to me like it takes away the naturally aspirated noise of cars. Supercharged Vettes / Stangs / Koenigseggs all sound like NAs to me + the whine while the new BMW M cars / F1 cars / Pagani etc. seem to have lost that magic NA noise post turbo. All of the turbo examples I mentioned still sound exciting but not to the extent of the older NA variants.

I am aware that a Supercharger is a significant parasitic loss as well outside of the boost it gives. I am the kind of guy who's concerned about wasting energy to the extent where I'm always (carefully) slowing down before red lights trying to conserve a little extra momentum that I'll use when it goes green, I usually drive 60 on the freeway etc. so there's still a slight chance of being talked into a turbo for economy reasons.

The goal is a future goal because I'm building a 2.7i to toss around in both drift sessions and autoX changing up my suspension as needed and figuring out where to focus the car. Suspension will be sorted out first. I'm only thinking about induction now because I feel I have a nice M20 (150k ish miles runs well), it feels nice every time I drive it and seems like the easiest way to reach my maximum power goal which won't be far above 300 if even there. I won't know if I even want the extra power of induction until after going 2.7i but I know if I do want to up the power I want to do it by boosting this engine.

My goal is fairly similar to yours of having a usable cruiser that sees track time but more track focused because I have a DD I trust to drive across the US.

[Ether-D]

First, I built an eaton m90 supercharged m20b25 e30 on megasquirt from scratch. It is my DD. So my knowledge is real.

There have been superchargers done before, read this thread: http://www.r3vlimited.com/board/showthread.php?t=306699

This is just a for sale thread for a product that doesn't currently exist.
Click the link in my sig for an actual "build" for the purposes of learning something.

The super charger is connect to the crankshaft and is constantly pulling the load off of the engine. This translates into wasted power such as cruising on the highway when the supercharger is not being used. I believe this can be upwards of 50 hp depending on the output of the engine.

Not correct.
About parasitic loss at cruise. There is almost none if you design your system well. That is one of the functions of the by-pass valve in a supercharged setup. When you are at very light (cruising) throttle, vacuum is created in-between the throttle body and the supercharger. This vacuum is what opens your by-pass valve (it's between the TB and the output side of the charger) to allow the supercharger to basically pump into it's own intake.

I think some people rush into cobbling together used parts and don't spend enough time thinking about the entire system and how each piece will work together. I'm not saying you should consider going with a turbo, just that you should decide what purpose the car will have.

A lot of people do do this, and that's why most supercharger builds die on the table, or don't last. 7500 miles and counting on mine...

I want a car that can cruise on the highway, be used year round, and can be driven on a track. My plan is for a 325iX with 3.64 final drive, and a turbo setup.

You may want a supercharger…

Whatever you do, always research and learn more!

This is good advice.

The glory of a supercharger for me is in it's OE feel. The power doesn't rage on at 5000rpm (as you're apexing that corner in 2nd), it starts as soon as you touch the pedal and builds in a very linear fashion. A supercharged motor (properly built) just feels like a bigger motor. A turbo feels like a turbo. Lag, lag, lag, WHOOOOOOAAAAAA!!!! Now a well built turbo can spool earlier. Just not instantly.

Side note: At 70mph, cruise control set, I get 27mpg in mine. Hogging it around town I get 22mpg.

[cleanasse30]

The glory of a supercharger for me is in it's OE feel. The power doesn't rage on at 5000rpm (as you're apexing that corner in 2nd), it starts as soon as you touch the pedal and builds in a very linear fashion. A supercharged motor (properly built) just feels like a bigger motor. A turbo feels like a turbo. Lag, lag, lag, WHOOOOOOAAAAAA!!!! Now a well built turbo can spool earlier. Just not instantly.

Side note: At 70mph, cruise control set, I get 27mpg in mine. Hogging it around town I get 22mpg.

Please don't generalize all turbo systems like this... Not all turbo systems are like this, and if yours is like this you are probably shooting for high horsepower numbers to tell your buddies how much power you make on the dyno but give no shits about driveability. A properly designed turbo system can make smooth power and be great on a track.

You should not be in boost through an apex anyway, if anything you would be maintaining throttle which puts the engine under vacuum. Unless you are drifting of course...

[Ether-D]

Please don't generalize all turbo systems like this... Not all turbo systems are like this, and if yours is like this you are probably shooting for high horsepower numbers to tell your buddies how much power you make on the dyno but give no shits about driveability. A properly designed turbo system can make smooth power and be great on a track.

You should not be in boost through an apex anyway, if anything you would be maintaining throttle which puts the engine under vacuum. Unless you are drifting of course...

I'm sure this is true. I mentioned properly built turbos and their ability to spool earlier. I mainly needed to clear up the misinformation regarding superchargers.