What will the average MPG be? Poll!

[tranzformer]

Originally Posted by Allch Chcar

This discussion would be better served in the engine tech thread.

I will add this. For example only: in tests like the EPA increasing the Engine efficiency is 1%:3% for every bit of improvement. While weight lost and aerodynamics improved is like 3%:1%. From the EPA fuel economy website.

DI doesn't increase efficiency by more than 3-5%, which is a lot. But 3% more efficiency points at the engine would be something like 12% more MPG on the road.

In general too high of compression can be bad for power after a certain point even though it generally means more efficient combustion. Ask the turbo guys and they'll unanimously demand low compression with a stout stock block. Gasoline Direct injection is better than port or throttle body injection but there are still limitations on the power vs fuel efficiency range for pump gasoline. Ethanol(E85) has a wider curve because but the same theory still applies.

Yes no doubt light weight and aero design of the car will do more for the fuel economy. However I was just replying back to the comment about the high compression.

[Allch Chcar]

Originally Posted by tranzformer

Yes no doubt light weight and aero design of the car will do more for the fuel economy. However I was just replying back to the comment about the high compression.

You misunderstand me sir. Increasing the compression ratio is more cost productive than reducing weight or aerodynamics together for FE. It's just that it can be bad when under heavy loads like heavy acceleration etc.

[tranzformer]

Originally Posted by Allch Chcar

You misunderstand me sir. Increasing the compression ratio is more cost productive than reducing weight or aerodynamics together for FE. It's just that it can be bad when under heavy loads like heavy acceleration etc.

I got you.

[Matador]

Originally Posted by Allch Chcar

This discussion would be better served in the engine tech thread.

I will add this. For example only: in tests like the EPA increasing the Engine efficiency is 1%:3% for every bit of improvement. While weight lost and aerodynamics improved is like 3%:1%. From the EPA fuel economy website.

DI doesn't increase efficiency by more than 3-5%, which is a lot. But 3% more efficiency points at the engine would be something like 12% more MPG on the road.

In general too high of compression can be bad for power after a certain point even though it generally means more efficient combustion. Ask the turbo guys and they'll unanimously demand low compression with a stout stock block. Gasoline Direct injection is better than port or throttle body injection but there are still limitations on the power vs fuel efficiency range for pump gasoline. Ethanol(E85) has a wider curve because but the same theory still applies.

Only because of having to severely retard timing or make other compromises in engine tune to prevent detonation and protect the engine. Lots of Turbo guys will obviously demand that, but lots of tubro guys only think in terms of static compression ratios. Boost + Compression will result in the same dynamic compression ratios inside the combustion chamber when running, if not higher.

Anyway, High compression + Boost on DI for the win

[Allch Chcar]

Originally Posted by tranzformer

I got you.

GOOD.

Originally Posted by MatadorRacing_F1

Only because of having to severely retard timing or make other compromises in engine tune to prevent detonation and protect the engine. Lots of Turbo guys will obviously demand that, but lots of tubro guys only think in terms of static compression ratios. Boost + Compression will result in the same dynamic compression ratios inside the combustion chamber when running, if not higher.

Anyway, High compression + Boost on DI for the win

I know, "boost retards" or w/e. I was just using that for a vague example.

I hear ya on high compression + Boost .

[boostedscooby]

anything over 30mpg will make this car sell and if subaru and toyota make this happen i will be getting one a.s.a.p

[tranzformer]

[Allch Chcar]

Originally Posted by tranzformer

So in other words expect Scion tC like MPG...

[tranzformer]

Originally Posted by Allch Chcar

So in other words expect Scion tC like MPG...

No better. This is going to use the new FB20 engine from FHI. That FB20 in the new Imprezza is going to get 27 city 36 highway in the heavier Imprezza (like 3000lbs?)

[iff2mastamatt]

Originally Posted by tranzformer

No better. This is going to use the new FB20 engine from FHI. That FB20 in the new Imprezza is going to get 27 city 36 highway in the heavier Imprezza (like 3000lbs?)

I'd be sooooo happy if it got this milage.

[tranzformer]

Originally Posted by Allch Chcar

So in other words expect Scion tC like MPG...

Sorry I was thinking you meant more the older tC mileage of like 20/27. I think it could be close to the tC if not a little better.

[Allch Chcar]

Originally Posted by tranzformer

Sorry I was thinking you meant more the older tC mileage of like 20/27. I think it could be close to the tC if not a little better.

The new tC MPG score is at least a starting point anyway. Now that we know the Scion is getting the 2.0L I'd hope it would get noticeably better MPG than the 2.5L in the tC and not just because it's going to be in a smaller car.

[tranzformer]

Originally Posted by Allch Chcar

The new tC MPG score is at least a starting point anyway. Now that we know the Scion is getting the 2.0L I'd hope it would get noticeably better MPG than the 2.5L in the tC and not just because it's going to be in a smaller car.

Yeah but it is hard comparing the 2AR-FE straight-4 vs. the FB20.

I would be curious to see how the FB25 would compare against the 2AR-FE straight-4.

[Allch Chcar]

Originally Posted by tranzformer

Yeah but it is hard comparing the 2AR-FE straight-4 vs. the FB20.

I would be curious to see how the FB25 would compare against the 2AR-FE straight-4.

We may never know, as far as I know there isn't an FB25 yet. Subaru put a FB20 in the Forester of all things to presumably help with the MPG. And the press releases says that the FR-S(that's what they're going to call it) will be using the FB20.

Originally Posted by http://pressroom.toyota.com/releases/scion-fr-s-concept-reveal-jack-hollis.htm

The naturally aspirated two-liter engine features Toyota’s D4-S injection system… which utilizes both direct and port injection… resulting in increased horsepower and torque throughout the entire powerband. We all know that it’s not hard to make horsepower and torque…but it IS hard to do all that AND get great MPG. The FR-S Concept tackles all three.

There is big differences between the old EJ and the 2AR-FE but the new FB is closer in design to a regular straight 4. Narrow bores with long strokes for example.