924Board.org

[jcope]

I don't really mean to start another survey thread, but I am curious what kind of mileage (mpg) people are getting. I'm getting around 21 or 22 in my 87 924S. It didn't change much when I replaced the ECU, and (I think) at the same time the chip.

I'm on the highway about a quarter of the time, so traffic lights could be part of the story. Also, I know these cars use more gas when the engine isn't warm, so short trips are going to cost me.

It seems low to me. If it is, I'm not sure what I would do to bring it up. My driving style is more aggressive than most, but I'm still nice to my car. So I don't know if there is much savings to be had there. Maybe 21 or 22 is just what I should expect. What do you think?

[d12-Matt]

That sounds normal. I think the specifications say 20 mpg city, 28 mpg highway.

[ltgland]

4.7l/km whats that in old money?

[dwak]

depends on who's gallon. Or is whom's gallon or even on who's/whom's (womb?) money.
dwak du bois

[ This Message was edited by: dwak on 2002-05-02 08:07 ]

[Paul]

The only way to break 25 mpg in a 924S is to always shift below 3000 rpm or drive it at a steady 55 mph for long distances....not an option.

[jcope]

So, what's up with that? These are 4 cylinder engines, after all. And they're fuel injected. I would expect a little more efficiency. Not like a Honda, of course, but this isn't any better than my truck.

My step-dad's Firehawk gets almost the same mileage. At 5.7L, he has over twice the engine. And it's a GM.

[Cbass]

Your dad's firebird also has EFI, doesn't it. Fuel economy is based off of 2 things. Power required and driving style. A 4000lb truck requires a lot more power to move it 300 km than a 2000lb sports car. Similarly, a car with a drag co-efficient of .28 will take a lot less gas than a car with a co-efficient of .40

However, gearing and speed also dictate fuel economy, because of power need. The drag from the air and the friction from the tires increases in a non linear curve the faster you go. However, if you have a 6 speed tranny, and can go 100 mph at idle, you will be expending far less fuel than a 4 speed car doing 4000 rpm at the same speed. It's all how the car is set up.

[jcope]

Keep in mind I'm driving a 924S, not a 924. I don't know what the difference is between EFI and the Motronic. Beyond design details, maybe not much. I have a 5 speed. And my step-dad is the single most agressive and competitive driver I know. I'm much more tame. I'm not disputing what you said, but I'm still curious why these cars aren't more efficient.

Based on what you said, I should be able to explain it based on:
1) the weight of the car
2) a high drag coefficient
3) driving style
4) gearing
5) speed

Well, these cars aren't THAT heavy, are they? And the Firehawk may be more aerodynamic, but the 924s aren't exactly cube-shaped. And I think for the sake of argument, we should factor out driving style and speed. Everyone knows that those will affect mileage and how. That leaves gearing. Is that it?

I don't mean to start a Firehawk-versus-924 car comparison discussion. I just want to understand the 924 a little better. I still think the mileage is kind of low.

[Benski]

Two things.

1) It may be possible that your father's firehawk shuts off gas to certain cylinders when the power is not needed. Some modern V8/10/12s do this, although I don't know anything specific about modern GM fuel injection

2) The low gas mileage of the 944/924S is because of the design. Porsche designed this engine to compete at Le Mans, a grueling 24 hour endurance race. Many of the engine internals are larger and heavier as a result. This is also the reason why it is not uncommon to see a 944 with 250,000 on the original engine.

[jcope]

That's true about the new cars. I forgot about that. He once got almost 27 mpg on a road trip!

I didn't know about the design of the 924S engines for racing. It makes sense. I guess that would also explain the oil consumption. Even when things are working properly these engines consume oil. I think I put in a quart every 900 miles or so.

Thanks for the insight.

[Geddy T]

I may be wrong, but I don't think the firehawk has displacement on demand. That's something that GM is starting to go to more, but until recently, was a cadillace thing. How new is the hawk? Also, when the 924 was first released, it had the lowest CD of any production car. It may be slightly above the firehawk's, but there's not that much room for it to be that much higher. I'm more for the gearing theory. Also, a big v8 does not have to rev as high to get it's power. Also, a well-tuned SEFI is a big deal. That's all about efficiency.

[jcope]

The Firehawk is a pretty cool car. It handles well and is fast as hell. I'm not a big fan of the body style or the size. And there are more rattly plastic parts than I think are necessary. When you close the door on the 924, there is one solid clunk. When you close the door on the Firehawk, there are lots of noises.

I'd still like to hear more explanations (if anyone has them) for the low fuel mileage. There hasn't been much agreement. The LeMans explanation was good, but maybe some more detail would bring it home for me.

[larso]

The 944 engine is a pretty big displacement for a four cylinder...all the 4 cyls out there that get really good mileage are really small, the 944 is a huge 4 cyl. v-8s seem to be smoother engines but I don't know if that would make a big difference.

[GRATIAN]

I drive aggressive with my car and the consumption is aroud 16l/100km.This is european units of mesurement.

[ltgland]

after the last 300 miles (200 on the highway) 27MPG yay