M42 Turbo Options

[Threehz]

I have some questions about turbocharging an M42.

Can anyone give an estimate for how much it would total turbocharge an M42?
(considering you already own the M42 and want to do a clean proper install)

Or how much their setup cost in total?

Also how much of a fuel economy increase could be expected from turbocharging an M42 in a '91 318is?

Anyone have any real world figures?

In turbocharging my M42 I wouldn't be aiming for power, more for efficiency. Any other ideas or suggestions related to turbocharging and M42's would be great.

Thanks!

[Dj Buttchug]

when you boost mileage goes out the window... to do it right and have it actually work and be reliable it costs in upwards of $3,500 just in parts, including well over 100 hours of work. if you do it yourself.

[Threehz]

Please tell me this is some sick and twisted buttchugging lie!?

Well that is a fucking bummer. Why is it so hard and expensive to do a proper job, and what would be the difference between a proper and improper job?

[Hey-U]

I have super charger fuel goes out the window. Boost is awesome unless you are a guru it's spendy.

[trackjunkie21]

If you're asking these kinds of questions, walk away.

[JohnHenryE30]

My personal project has taken over 2k in cash for the turbo stuff to be complete(excluding the tuning stuff)... but the compression ratio of a stock m42b18 engine is 10:1 which is not the safest for high boost IMO. It has and can be done... but detonation is a risk if not tuned correctly. Very intricate.

[nrubenstein]

Please tell me this is some sick and twisted buttchugging lie!?

Well that is a fucking bummer. Why is it so hard and expensive to do a proper job, and what would be the difference between a proper and improper job?

Parts are not cheap. There is a lot of labor, even if you do it yourself. Tuning is very expensive. And you should be ready to replace the motor while you debug the setup too.

As for fuel economy, well.... No. I mean, if you out in a tiny, tiny turbo that just makes lots of torque off idle and then gear the shit out of it (we're talking eta gearing) then you'd see some improvement if you do it right. But for all intents and purposes, aftermarket turbocharging does not improve economy.

[Threehz]

Did some quick reading and this all makes sense now. No turbo for my M42

[Richard Fitzwell]

Yeah, not a cheap motor to boost. i just did a quick add up of SOME of my parts and im at $4420 and thats guessing and missing out on a good amount of parts. Buy rob e30's block and you'd have a nice little project.

[gearheadE30]

I'm sitting a little under $3k right now for my setup, which is almost entirely done by me. I got a good deal on a stainless manifold and downpipe though, so I didn't have to do any r&d there. I also did everything myself, including a new head gasket and ARP studs when I popped the original. I get about 23 mpg average in mine at the moment, and I'm not done tuning. It's doable, but it is kind of an ongoing investment of constantly hunting down the next weakest link. (mine are currently the cat-back, a diff in need of new clutch plates, and tuning...and fixing the turbo oil drain and a crack that developed in the header and finding a way to vent excess heat from the engine bay....see what I mean?)

[Threehz]

Jesus. I'll definitely be leaving my M42 in peace, she doesn't deserve all that stress anyways. Thanks for the clarifications haha

[bwawuz02]

In turbocharging my M42 I wouldn't be aiming for power, more for efficiency. Any other ideas or suggestions related to turbocharging and M42's would be great.

Flip the stock exhaust manifold and build an adapter for an IHI VF38 turbo. done. semi-cheap and meets your requirements. You can run 10psi on the stock motor without worry, properly tuned of course ;)

[Vivek]

Why would you turbo for fuel efficiency? Those two things are like polar opposites. (I'm not trying to ridicule you, i'm just interested in your thinking)

[Massimo]

Turbo can be efficent if it wasn't then why is there a tread for new cars pushing fuel effeceny and turbo 1.6lt?

though you would not be looking for power gains you would be looking to run a really small snail to get you low end torque. That way you wont have to use as much gas taking off from lights, hence saving you gas. Along with a fuel effecency tune.

Even then though your feul savings are going to be small if any. You are better off going for weight saving.

[Threehz]

I'm about to make some assumptions and guesses based on my limited automotive and physics knowledge so correct me where I'm wrong.

Exhaust gasses are technically wasted power in a NA engine setup. However they are necessary waste because harnessing the entire amount of energy from combustion would require a huge stroke and massive engine and wouldn't work in an automotive application for many reasons..

A turbo-charger uses that waste gas to spin a compressor which compresses air before it enters the combustion chamber. Now this is me guessing, but pushing compressed air into the combustion chamber is like raising the compression ratio allowing for better performance.

That by definition means that you are using waste energy to increase efficiency which is a win win.

So the obvious problem is that the M42 was not built to be turbo-charged.

Again let me state that everything I said was just me making guessing from what I know so correct me if I'm missing something.

Wouldn't the only reason for not seeing improved efficiency be tuning issues? The aspects that I would see as restrictive would be tuning and threshold.
Tuning comes down to timing, AFR, and volumes of intake/exhaust hoses/pipes.
Threshold would be engines capacity to not break under increased stress.

Anyhow I'd love to hear some insight or have someone correct me if I made some dumb assumptions!