As I believe, it is inevitable that the government is going to push up gas milage on both cars and probably even more on SUVs and trucks. I was wondering were the automakers can go from here? While improvements in milage will be modest, how much is left to squeeze out of the high HP V8s and other high output motors?

You can improve aero and other things left in the vehical, but how much more aerodinamic can a SUV or even a truck get? Other then converting to another fuel, how much do you guys think is left in the pump gas engine.

This question came to mind while I was thinking about some of the high HP vehicals that are getting ready to come out of Detroit. I was thinking, just how far will the government let this go before they force the auto maunufactures to improve gas milage and emissions?

thanks
Jeremy

 

i think the next big thing will be the new variable displacement engines, such as the ones GM is getting ready to start rolling out. that will help meet higher milage and lower emissions standards for a while, while allowing even larger displacements with higher power output

 

People need to stop buying SUVs because its the "in" thing to do. My mom included. Her explorer gets like 14 mpg, and all she uses it for is driving to work and home. People just think they need an SUV.

 

There are afew things I think Detroit will do to increase mpg:
1. Hybrids
2. CVT or 5,6,7 speed auto trans to keep rpms down
3. Hydrogen fuel cells

My $.02

 

1 & 3 are probably our best bet for significant increases. Variable displacement (DOD in GMese) may be 8% improvement, and 5-7 speed automatics are a little help. Some of that is trans rotating efficiency and maybe engine-off at idle like the hybrids. If I recall, a good hybrid actually gets better MPG in traffic that on the freeway.

Vehicle gross weight is the biggest culprit. At a given performance level, overall lifetime fuel economy is pretty much proportional to gross weight. Here's where big SUVs get bit

IMO, hybrid SUVs are going to become popular, perhaps in small medium and gigantic sizes.

 

I think GVW (gross vehicle weight) is a big part of the problem too.
I have herd many times that 100lb more weight can slow you a 0.1sec on the 1/4mile and cause you to loose at least 1mgp city and high way.
I'm going to put a tubular k-member, fab me some frount LCA's from Titanium for my V6 and even with my crane 272 cam I should still be able to get at least 26mpg and be under 3000lb with full trim.
Titanium scraps and ebay, the best thing I have going now.

 

BTW 7SPD transmissions are here just not at all levels

Anyone look a t the New Mercedes?

Efficentcy is the key. Lighter more efficent cars till fuel changes

 

lighter cars should come into play no matter what because all the drivetrain componets are doing less work and it allows for a numerical lower gear to keep the rpms down on the highway. DOD is going to be the next thing from GM alothough its not very exciting its better then nothing and already developed. I believe one piston is all a corvette needs to keep going after its on the road so it should help.

 

I'm really surprised that Turbine/Electric hybrids haven't hit the market, or are even on the horizon.

 

weight is one way. increasing price if steel means hydroforming which means less weight.

want to know how much weight and aero "matter?"

Silverado 5.3-285hp - 17mpg highway- maybe 18 with same gearing as a Z06
Z06- 5.7L, 405hp- 31mpg highway.


my measly 4.8 goes 17 pure highway at my gearing isn't that bad. around 2000rpm at 74mph.



what it all comes down to is you need to make enough power to overcome friction/powertain losses for the highway.

higher rpm means more friction
8 cylinders means more friction
etc etc

but its not like the V8 HAS to guzzel gas. it can have lower RPM to make the same power.

 

What Boost it! said
The Z06 proves V8's don't have to drink gas.

 

Thoughts:

Mileage is more about acceleration than maintaining speed on a "level" road. Except in some parts of west Texas, there aren't really many "level" roads which you notice if you bicycle, or for us lazy louts, watch an instantaneous MPG computer on a car.

Just maintaining a steady 60 mph on a road that rises 100 feet in a mile requires about 15 more hp than it does to overcome friction, and aero losses on a 5000 lb Ute. The friction and aero losses might consume 45-60 hp (probably high), so that 1.9% grade can be 25-33% more power required. If the gross weight of the vehicle was 2500 lb, the extra hp would only be 7.5.

A Z06 has fairly low friction and aero drag as well as relatively low gross weight so less hp is required to cruise so lower gearing can be used than in a Ute. It just gets better (or worse) depending on weight.


Turbine engines are notoriously thirsty. Controlling them is also expensive. High bypass ratio turbofans are a big help, but not unless you are cruising a few miles high at speeds approaching 600 mph. Even Detroit freeways don't reach that average speed.

HSLA (high strength low alloy) steels and hydroforming do reduce the amount of material needed for structure, but only by a few %. Exotic materials could reduce weight a ton (pun fully intended), but at what cost? Even aluminum which is 1/3 the density of steel is less strong than steel so lots more of it is needed. A well designed cast steel rocker arm is much stiffer that any aluminum rocker arm and can have the same or less moving mass.

The highest strength aluminmun, 7075-T6 for example, is about as strong as HSLA steel which has been formed. Recently some OEM suspension components of steel are lighter and stronger than some aluminum ones doing the same job. You might save a few kilos on control arms, but it's the ton of body/chassis attached to them that makes the difference.

Much of the DOD savings is fuel not burned by the 4 dead cylinders, but also from the lower pumping losses because the valve is held open. Friction is still there, but at low, often below 2000, rpm it is fairly low. Remember inline 4s have the same number of main bearngs as V8s, and more cam bearings and cam drive losses if they are DOHC vs. the pushrod V8.

Not sure about domestic 7-sp autos, but 6 sp autos are coming. With a 1st to 6th ratio probably over 6:1 (4l60 is 3.06/.7 or 4.37) they will help heavy vehicles at lower speeds with smaller engines keep up with traffic and still cruise at low rpm. Of course with different ratios they might be nice in the high-end cars also.

FWIW, a C5 probably takes well fewer hp than what one cylinder provides at max power to maintain 75 mph. Of course, who would want to have that one lung running 6000? Efficient part throttle low rpm power production often needs the opposite things from what full throttle high rpm power demands. That's a huge challenge to OEMs. We tweak our engines for more WOT power and live with lower mpg. Not allowed in OEM. One design requirement for the C5 and C6 was NO gas guzzler tax. Ferrari, Lambo, etc. don't really worry about that as much, I suspect.

My $.02

 

Valves controled by a electric motor or magnet. This way we can control have much duration, lift and lobe seperation the valves have vs rpm and throttle. This would really help out gas milage.

 

We can controal the lift and duration a little with rhoads variable lifters.
There are is the chevy VVT that changes valve timing, exhaust valve only I think.
They need to combind the 2.
RPM based varible lift and duration and load based valve timing (advance/retard for one side if it has to be).

 

Variable Valve Timing (VVT), even solenoid actuated as you suggest, certainly can help mileage, but not to a great extent. Shutting off cylinders probably does more, and combining DOD & VVT would probably be even better. We're still not talking a huge improvement. Maybe 15% max over what we have now.

Direct Fuel Injection(DFI) into the cylinder is coming, which again can help. I think Audi Racing used DFI in their LeMans winners of the last few years. They seemed to get better racing uel economy that the competition who were not using DFI. So maybe DFI, VVT and DOD might get us 20-25% if we do everything right. I may be optimistic at that level.

There really isn't a magic bullet that will improve mileage on today's internal combustion engines dramatically. Well maybe the Tornado might, and it doesn't cost an arm and a leg.