Turbo Charging an aircooled motor

[joose]

Hi Everyone,

I have been thinking about this for a while, and I decided to run it by everyone on the forum to get idea's/opinions etc. As we are all aware, petrol is nice and expensive now, and getting the best economy out of an engine is very important these days. With that in mind I was wondering how feasible it would be to build a turbo-charged aircooled engine aime primarily at fuel economy. Something like an 1100,1200, or 1300 CC beetle engine with EFI, engine management and a small, low boost turbo (0.4 bar or thereabouts). Kinda like the modern turbo diesels and small tubo city car engines. Power would not be the major concern (although at least 55kw would be required I think for the car to be reasonably usauble in the modern urban/highway environment). I like the idea of using the aircooled motor because it is cheap to buy, cheap to run and simple. What do you guys think of this idea? I know they offer all kinds of turbo-charged engines in the USA, but there doesnt seem to be anyone here who does this kind of thing...

[Tony Z]

The key to fuel economy is compression (engine efficiency) which is why a diesel is more efficient than a petrol. Running a turbo means you need a lower compression ratio. So you loose out there.
Small city cars make up for the loss of effiency with fany electronics and a small engine, meaning they loose very little power to friction.
Making a Beetle ultra effienct will cost more than the fuel you will save in the long run. Your best bet is prob to take a stock engine, get the crank counterweighted and all parts balanced. Get twin carbs (IDFs would be best, but the SP carbs will be great too). Get a vac advance dizzy and plumb it into the manifold. Run the dizzy with 28 to 30 deg full advance, which equates to around 46deg adv on the vac.
Then bump up the compression to around 9:1 or 8.8:1
Dont lighten the flywheel
Thats about how far I would go on a smallish budget.

[joose]

I thought that the increase in efficiency comes from being able to have a smaller engine with similar power/torque to a bigger N/A engine? That is why I wanted to go for an 1100 or 1200cc to give me the increase in fuel economy. Also, doesnt the fact that you are scavaging "wasted" energy from the exhaust and using it to feed the engine more air also help to make a turbo-charged engine more efficient? This, combined with efi and engine management should make for quite a usuable and effcient little engine surely? or am I talking rubbish?

[Bugger]

Hi Everyone,

but there doesnt seem to be anyone here who does this kind of thing...

There are a few mad ones of us But we do it for POWER and nor fuel economy what tony said is 100% correct in the cost that it will cost you Turbo EFI Chargecooler etc you have to do some serious miles to recoup money on saving But believe me if there is boost to be turned it will def be turned up after a while for just that little bit extra power and there goes the fuel consumption to Hell

What I have seen for good fuel economy is bigger cc N/A with nice Torq and high profile wheels to bring the RPM down on a 1600 transmission

[Rabid_ant]

Eh..., i stand to be corrected, but there's no real need to drop the CR on the motor if you're only running 0.4 bar boost.

[Tony Z]

I thought that the increase in efficiency comes from being able to have a smaller engine with similar power/torque to a bigger N/A engine? That is why I wanted to go for an 1100 or 1200cc to give me the increase in fuel economy. Also, doesnt the fact that you are scavaging "wasted" energy from the exhaust and using it to feed the engine more air also help to make a turbo-charged engine more efficient? This, combined with efi and engine management should make for quite a usuable and effcient little engine surely? or am I talking rubbish?

Your ideas are correct, but just not thought out 100% yet.
The smaller engine idea is right, but only because you have less friction which leads to less losses while operating.
The turbo engine is more efficient under boost than a N/A engine. But 90% of its life, it isnt under boost conditions, and at that time, its a N/A engine anyway.

[vader]

mmm Interesting.... What about a small turbo on a 1915cc to give you more ooommmmfff but keep it reliable???

[Tony Z]

I would say if you are not too concerned about power, go small.
Small diameter pistons and longer stroke if you can. Increases torque while keeping the burn clean
If the car needs 50hp at 3500rpm on the highway, then aim to design for a max power of 55hp.

[vader]

But what if you want it to make say 110hp but still want the reliability?

[Tony Z]

then go 1600 turbo if you have the cash. If you want fuel effiency, then go 1900 with a stroker crank

[Bugger]

Eh..., i stand to be corrected, but there's no real need to drop the CR on the motor if you're only running 0.4 bar boost.

You are correct Ra the bug has in any case quite lower CR than W/C motors and alot of the newer cars the aftermarket Guys just bolt on the Turbo or Supercharger(with 10/1CR) and do the extra fueling and lower timing under boost with Piggyback ecu`s and stay around 0.4Bar boost

I had a 1600 Turbo bug Quite awhile back with a SU Suck through system and at that time the std 2.0L Opel Boss was King on the road and I used to Nail them with a STOCK 1600 with just the Turbo set up added with around .8Bar boost

[Blitzkrieg]

I had a 1600 Turbo bug Quite awhile back with a SU Suck through system and at that time the std 2.0L Opel Boss was King on the road and I used to Nail them with a STOCK 1600 with just the Turbo set up added with around .8Bar boost

That is blitz quick!!

That means that my future 1800 Turbo, even on mild boost, will be a lot of fun to drive

[Chris]

I was womdering if you can fit a turbo straight onto a standard Beetle engine.

I want to fit on with about 0.4 bar boost just to give it that extra punch off the line.

[eben]

REMEMBER TO IMPROVE COOLING!

[Tony Z]

I was womdering if you can fit a turbo straight onto a standard Beetle engine.

I want to fit on with about 0.4 bar boost just to give it that extra punch off the line.

Yes you can, its nto really that hard, but for a little extra punch, why not just improve the engine in N/A guise a little. 80hp 1600 isnt that hard to achieve and reliability is still almost 100%