Is it even possible?

[Newcat016]

There is a certain person on a seperate forum that is claiming to get 45 mpg highway out of a 351w engine. I'm not too good with specs but here is what he listed as having. Its a 2250 lb kit car, it has custom gears 3.27:1 rear axle ratio with a HD 5spd transmission with 3.27:1 first, 1.97:1 second, 1.34:1 third, 1.00:1 fourth, and a 0.68:1 fifth. I will now quote the rest "I am also running gapless piston rings and a roller camshaft and dual idler timing set with no power steering. The engine is running at 97 - 98 % efficency at highway speeds and something like 90 - 92 % efficency at idle. With the gapless piston rings I am able to run a leaner air/fuel mixture and make the same power because these rings have no more than 2% blow by where convential gapped rings have something lik 20% blow by and can get up to 35% blow by after engine break in where these gapless rings will keep less than 2% blow by and guarenteed to do that for 100, 000 miles for the road race/forced induction/nitrous ones I went with. By the way I am also running sequential fire fuel injection not a group fire injection where all 8 fuel injectors fire at once. They only spray fuel for the cylinder that is opening. Then I have ignition timing controlled by the computer and map sensor so its just like the factory except it is finetuned for efficency and power....I wanted the block to avoid the roller camsahft retrofitting. For heads I went with World Products Windsor Sr Aluminum Lite heads with 200 cc intake port runners with a 2.02"/1.60" valves. I also went with dished pistons to bring compression down to 9:1 with the 64cc combustion chambers. Then for induction I choosed a pricy $3, 000 aluminum intake manifold that has eight 50mm throttle bodies for each cylinder with small short velocity stacks to immitate the old Weber Down Draft carbs."

WTF? Possible or not with mods listed?

[sonza68]

Seems unlikely, but C5 and C6 Corvettes have been known to pretty easily get 30 mpg on the highway and they are 1000 lbs heavier. My Mark VIII at 3768 lbs can get around 28 mpg on the highway if I'm gentle with the throttle. If the kit is reasonably aerodynamic, it might be possible.

[Jorgen]

There is a guy on an explorer forum claiming somewhere in the neighborhood of 30 mpg out of a 2nd gen explorer.

It might be possible with the engine listed out, that would be very ginger on the gas though. Really who builds a kit car for gas mileage?

[Newcat016]

Thats the thing, he still claims 415 hp with it? Its his road racer. hes kinda like contradicting itself. He has a track car that gets good gas mileage? He says he drives it to the events thats why he needed the gas mileage. The block is apparently out of a 95 cobra R? Idk, it just seems kinda stupid to me.

[shoult]

I'm just gonna call B*llsh*t on anybody that claims 45 mpg from a 351W, period. It's not going to get that no matter the weight of the vehicle, gearing or mods to the engine.

If some goomba in his garage really could get that kind of mileage you KNOW he would be selling the technology. He wouldn't just be boasting in the forums.

So I call B*LLSH*T!!!!

[Jorgen]

Who is he going to sell the technology to? You think that OEM's an aftermarket companies don't have the ability to achive better mileage than they do? a car coming from the factory has to be designed to make everyone happy (emissions, noise, power, fuel economy etc.) they are all trade offs and you end somewhere in the middle with a mediocre car. If you built things out for a specific goal (ie fuel economy), knew what you were doing a little and researched a lot you can achive some pretty amazing numbers.

This is not to say that this guy achived it but I wouldn't say it isn't possible either.

[Turbo Zetec 'tour]

with the gearing, light weight of the car, gapless rings, and ITBs i wouldnt doubt if he can get excellent gas mileage. 45 MPG still seems too high IMO but 30s should be achievable i would think.

[papatedroach]

I think 45mpg is very resonable... while rolling down a hill in neutral

Honestly though, if he has a very good runnning motor in a very light car he could be pretty much ideling down the highway which could give that good of a mpg.

BUT: Those efficiencies that he posted is total and utter BS. Gasoline as a fuel is not even capable of those efficiences. Then with all the mechcanical, frictional, and heat losses in a motor, efficiencies of internal combustion motors are nowhere near that high.

Also to there is a big problem that will come up with fuel efficiences, the power of the motor, weather it be measured in HP or Tourque, will always be related to the amount of fuel you use. The motor simply converts the carbon in the fuel into mechanical energy by burning it. With a theorectical 100% efficient motor XX hp will always take XX fuel to make that power.

[Turbo Zetec 'tour]

Originally Posted by papatedroach

I think 45mpg is very resonable... while rolling down a hill in neutral

Honestly though, if he has a very good runnning motor in a very light car he could be pretty much ideling down the highway which could give that good of a mpg.

BUT: Those efficiencies that he posted is total and utter BS. Gasoline as a fuel is not even capable of those efficiences. Then with all the mechcanical, frictional, and heat losses in a motor, efficiencies of internal combustion motors are nowhere near that high.

Also to there is a big problem that will come up with fuel efficiences, the power of the motor, weather it be measured in HP or Tourque, will always be related to the amount of fuel you use. The motor simply converts the carbon in the fuel into mechanical energy by burning it. With a theorectical 100% efficient motor XX hp will always take XX fuel to make that power.

yes but while cruising down the highway, in a car that light he is probably using at most 10-15HP (on a flat road) to cruise. It doesnt take a whole lot of fuel to make 10HP.

also, the efficiencies he is talking about is probably Volumetric Efficiency, which can reach 100% NA and break 100% with FI. i know on my Zetec with nothing but an intake and exhaust i had a calculated VE of 95%.

Edit: as i stated before, 45MPG seems a bit of a stretch, but mid 30s should be possible.

[papatedroach]

A high volumetric efficiency is possible.

I had a calculated VE of 95%.

Just curious how did u calculate it?

I cant wait to see what kind of mpg i can get with my kit car, 1200lbs and a 1600cc motor