Speaking of turbo and fuel economy

[Matt Timion]

I was thinking today about my n600 (nothing new, I know). Is it possible to turbo a small 600cc 2 cylinder carburated engine? If so, what type of fuel gains should I expect to get?

Turbo is all unexplored ground for me, so I have no idea if it's even possible to install a turbo on a non-EFI car.

[krousdb]

Originally Posted by Matt Timion

I was thinking today about my n600 (nothing new, I know). Is it possible to turbo a small 600cc 2 cylinder carburated engine? If so, what type of fuel gains should I expect to get?

Turbo is all unexplored ground for me, so I have no idea if it's even possible to install a turbo on a non-EFI car.

Sorry, I can't even begin to answer that question. But it made me think of this 5 part article about turbocharging the Prius 1:
http://autospeed.drive.com.au/cms/A_2658/article.html
http://autospeed.drive.com.au/cms/A_2659/article.html
http://autospeed.drive.com.au/cms/A_2660/article.html
http://autospeed.drive.com.au/cms/A_2661/article.html
http://autospeed.drive.com.au/cms/A_2664/article.html

[Sludgy]

Turbocharging will usually result in fuel economy gains IF several things happen:

1) You re-gear the car to a lower final drive ratio or put larger diameter tires on it. This makes the car run "on boost" most of the time. In this regard, a small turbo is better than a large (high-horsepower) turbo is used.

2) Keep driving the same way. This can be hard to do given the extra accelleration you get.

Turbocharging a twin cyclinder engine like your N600 could be tough, because of the pulsed exhaust flow from the engine. Turbos like steady flow. It's much worse than a 4 cylinder, which isn't terribly good to begin with.

[rh77]

There are a few things you would have to do. First, turbos (for the most part in Europe) are added to small-displacement vehicles, especially Diesels, to increase horsepower without adding the weight of extra displacement. With that said...

*Do you need the extra horsepower? If not, a turbo will only use more fuel.
*Secondly, managing a turbo on a older car would require a costly engine monitoring system, since forced induction tends to run the car dangerously lean unless a fuel management/monitoring system is installed to enrich the mix when necessary.

It's much worse than a 4 cylinder, which isn't terribly good to begin with.

I'm not sure I agree with this statement. 4-cylinder cars are great for turbocharging. My old street-legal, factory stock 2.0L, 4-cylinder Mitsu Evo-VIII Turbo-AWD (271 hp) would spank the pants off of "muscle" cars with twice the displacement. If you want domestic, then the Dodge SRT-4 (Neon) is insanely fast and puts cars 5X its price to shame. The turbo works very well with 4-cylinders and Diesels. 6- and 8-cylinder vehicles tend to benefit the best from a belt-driven super-charger.

RH77

[Matt Timion]

Originally Posted by Sludgy

Turbocharging will usually result in fuel economy gains IF several things happen:

1) You re-gear the car to a lower final drive ratio or put larger diameter tires on it. This makes the car run "on boost" most of the time. In this regard, a small turbo is better than a large (high-horsepower) turbo is used.

2) Keep driving the same way. This can be hard to do given the extra accelleration you get.

Turbocharging a twin cyclinder engine like your N600 could be tough, because of the pulsed exhaust flow from the engine. Turbos like steady flow. It's much worse than a 4 cylinder, which isn't terribly good to begin with.

You make excellent points about the pulsing. What makes it even worse is that both cylinders fire at the same time. The only redeeming factor would be the fact that the engine can normally run at 6000-8000 RPM in regular driving.

I just like to think of fun ways to make my n600 more driveable and efficient.

[GasSavers_DaX]

Originally Posted by rh77

*Do you need the extra horsepower? If not, a turbo will only use more fuel.

BAM. Finally someone agrees with me.

[MetroMPG]

careful of blanket statements.

i believe the answer is more like "it depends".

(i'm having deja-vu. didn't we do this conversation already?)

the owner of the prius claimed a small measurable improvement of f/e after the turbo. perhaps due to the CVT which could respond to the extra available torque by operating at a lower RPM right across the car's speed range. that would increase efficiency by reducing losses from internal friction. that's my understanding of it anyway.

[GasSavers_DaX]

Originally Posted by MetroMPG

careful of blanket statements.

i believe the answer is more like "it depends".

(i'm having deja-vu. didn't we do this conversation already?)

the owner of the prius claimed a small measurable improvement of f/e after the turbo. perhaps due to the CVT which could respond to the extra available torque by operating at a lower RPM right across the car's speed range. that would increase efficiency by reducing losses from internal friction. that's my understanding of it anyway.

I think we did have this convo already, and I think I can agree with what you're saying. I guess what I'm saying is that most of the time it will use more fuel, and the times that it won't, it will take a gem of a person to not stomp the throttle to feel the boostcrack.

[Matt Timion]

Originally Posted by DaX

I think we did have this convo already, and I think I can agree with what you're saying. I guess what I'm saying is that most of the time it will use more fuel, and the times that it won't, it will take a gem of a person to not stomp the throttle to feel the boostcrack.

Yes, we did have this conversation a while ago. I more or less started this thread to think out loud about adding a turbo to my n600, which seems to be rather unlikely.

It seems more likely to convert the engine to EFI. This of course would require a custom ECU and wiring harness. I could actually end up using the throttle body from my DPFI engine and making a custom intake manifold. Since this car only has two cylinders, and since they both fire at the same time I would only need one injector.

I would actually consider using the DPFI ECU, except my n600 engine is not water cooled, and therefore would always throw a CEL because the water temp sensor wouldn't be working.

First things first, however, I need to get the car up and registered. Soon... soon...

[Compaq888]

If I had a turbo car I would be all over the gas pedal. Actually the engine in my car is really good for turbos if it's built, otherwise the pistons fail. The pistons were designed very bad but otherwise the engine is bulletproof. There are a couple of KA24DET making 600-700hp to the wheels. For a 4 cylender that is impressive.