Now that's almost deserving of the SS badge.

 

You are correct! My pocket book cares though.

Jeremy your G6 would probably not pick up 5 mpg from this engine. Its rating came from a smaller car. The extra 300lbs in your car would cut into the 38.5 number, plus add in premium gas.

The real world best answer probably lies back in the E85 thread. I past three pumps daily. Its going for 2.29 and 2.39. If GM could put the 1.4T in the aveo or astra and get the same gas mileage as the current NA cars the customer would win out. Same goes for a 1.8T or 2.0T in epsilion. That would sell. With the 104 octane and E85's cooler burn you probably wouldn't need a intercooler which would helps costs and packaging. If you fill up with 91 octane in a pinch the computer could dial back the boost and you would be okay.

Will manufacturers get CAFE relief for vehicles designed to primarly run on E85? Seems like they should. Not Flex fuel but a vehicle with a HP rating and marketed based on E85.

 

No, it doesn't. For a modern aerodynamic car, it's probably a little under 20.

As a kid, I recall commercials for the NEW 1980 Chevy Citation, and they pointed out that the car took 8 road HP to go 50mph.

And 20hp for an AC compressor? I'd have to see that to believe it. Show me the data.

 

Also jeremy the extra gear in the auto tranny doesn't always mean extra mpgs. Maybe if you dont put alot of weight in the car, dont drive on hills or when its windy it may help, but theres alot of varibles that effect mpg. My wifes Aura XR gets 26 mpg, the G6 GT rental I just turned in got 29 mpg with a 4 speed auto. The final drive ratio favors the Aura but less weight and lighter wheels come into play for the G6, same for your saturns. Dont forget autotrannys usually add more weight and are less mechanically efficient. For you car with the six speed auto the 2.4 would be stressed at an uphill grade and would downshift alot which uses more gas than a better overall gear ratio. Our Aura is the perfect example of this, at 74 mph the rpm is 2000, start going up a hill and the car looses 4-5mph, downshifts to fourth and applies like 30-40% throttle. It does this 3 times on her 55 mile commute. The G6 never lost momentium or has to downshift thanks to better overal gearing. On hilly state highways I dont even think of using the cruise on the aura. Its more efficient to put it into manual and leave it in 5th.

Overall our six speed has been a dissappointment. The reason we had a G6 rental was because I didnt like the tranny shift logic and the dealership was updating the program. Too bad it took three days. The 3.5 and four speed seem to work alot better together. I am always amazed at the 3.5L mpgs.

Another example would be to ask toyota why the six speed tundra cant match the four speed silverados mpgs?

 

Depends on the tech. A variable swashplate (and maybe also a variable scroll)compressor might only use that under light loads, but what is on most cars right now (fixed scrolls or fixed displacement swashplates) uses a bit more than that. I've been out of that field for a couple of years, and my old company might have used very conservative numbers, but I am confident we are looking at at least 15hp under high loads.

When would those high loads be? Initial startup through the first 10-15 minutes of running in high ambient temps.

Now that I think about it, it doesn't really mattersince we will be using electric compressors by 2020...

 

confidential guys, sorry...

 

??? That's 14kW, which is more than I'd expect for a home A/C unit. I have trouble believing this number for an automotive engine. Hell, that's a lot more airflow than the IAC valve can provide!

I found these numbers for the Turbo Grand Prix:

Road horsepower at 30 mph: 7 hp
Road horsepower at 50 mph: 17 hp
Road horsepower at 70 mph: 36 hp

And for the Turbo Trans Am:

Road horsepower @ 30 mph:.......... 6 hp
Road horsepower @ 50 mph:.......... 16 hp
Road horsepower @ 70 mph:.......... 34 hp

I could run some numbers based on EPA fuel economy, but I'm in-between meetings right now

 

And if we need a 20HP motor to drive said compressor, we're in big trouble.

 

IREngineer,

Are you thinking of the peak HP robbed if the compressor were engaged with the engine at redline, perhaps? As opposed to the power required for it to actually maintain the A/C cycle at road speeds... (I don't know much about HVAC systems, sadly, so I'm just thinking out loud a bit).

I do agree with Eric and the others that 20 hp sounds pretty dang high.

 

You know, maybe I'm confused or we are talking about different things here. I'm speaking about drag on the engine via the drive belt. Maybe i'm way off here (as it appears I am due to the being raised here), as I wasn't a systems engineer. This is just what I thought I was told during cross-discipline training.

Sorry for causing a ridiculous tangent. If you need any help designing a F/I cooling loop, I'll be in the corner with a dunce cap on.

 

I've heard some absolutely horrific numbers for drive belt losses, and so your number may indeed reflect some of that under less-than-optimum conditions (or the number you heard may have been an example of what happens if the belt-n-pulley crowd screws up).

After eyeballing the 300V AC compressors that I've seen on hybrid vehicles, I'd guess that they're a few kilowatts (in continuous-duty operation) at best.

 

I can say that on my '80, I consistently gained almost 1 full mph at the top end of the strip, just by taking the AC Belt off. I'm guessing that has much to do with the inertial load of accelerating that heavy pulley on the front of the R4. It was a bigger loss than expected.

What's the typical "tonnage" or BTU rating on a typical passenger car AC system? 2-3 Tons perhaps? 3 Tons is 15-ish HP, but that's full load, and auto AC systems don't run this way much. Then again, I'm not even sure you can look at it that way, because the AC system isn't creating 15-ish HP of heat, but instead simply transporting it.