Going for 40 MPG, Let me hear your 2 Cents worth Options

[smontanaro]

Practice your technique. (IMG:style_emoticons/default/biggrin.gif)

[swl]

Watched a myth busters last night where they proved significant milage improvement from texturing the body surface like a golf ball. Not for the CW's (IMG:style_emoticons/default/biggrin.gif)

Convert to diesel - good for about 25-30% milage increase.

[Dave_Darling]

I've been told exactly opposite. You want the engine to be at cruise speed about 40-60% of your max horsepower RPM. Thats why those little fuel efficient Hondas and such run a fairly high RPM on the freeway.

To be blunt, you've been told wrong. The Hondas that get better mileage have taller gears. The CRX HF, in particular, has exceedingly tall gears. That's one of the things that helps it get good mileage. And a number of people have switched to taller gears in several different types of cars, and all have gotten better economy.

--DD

[campbellcj]

I haven't measured it scientifically, but I think I get about 10mpg...LOL

[Teknon]

you can shut the engine off and coast, but I think that opens up the door to the possibility of significant problems in an air-cooled car.

--DD

Yup....the 914 only restarts 60% of the time. (IMG:style_emoticons/default/lol-2.gif)

914 restarts? (IMG:style_emoticons/default/headbang.gif)

Kevin you are a pisser (IMG:style_emoticons/default/51.gif)

[Porcharu]

Hiya Kevin,
I averaged 32 mpg in the silver car from Denver to Seattle. Average speed about 68 mph dial it in, inflate the tires and go for it.
In driving my wifes jeep I found that I could squeek out a couple of more miles per gallon by shifting to netrual and coasting down hills, up off ramps, to a stoplight. No reving the motor unless necessary, and long un intrupted highway driving. 60 mph may be slow when the speed limit is 75, but that extra 15 mph cost a lot of fuel. and the puppies may have to deal with the windows up during free way driving.

I did that drive but the other way around from Abbotsford BC to Colorado Springs being chased by a storm in November with near bald tires on my old truck. Got new ones in the Springs. Damn long drive by yourself.

[Brando]

I was able to get 34-38mpg consistently in my well-tuned 1.8.

Okay, it wasn't well tuned. Just tuned.

205/65/15 tires. Good fuel. Clean filters. Clean injectors. Good spark (MSD). Good induction and exhaust. Keep it at 3000-3200 rpms for long distance drives.

40mpg is not unattainable. You could re-gear 5th so that you cruise at 2600rpm in 5th doing 75. There may be cooling issues but... You would get good MPG.

[Porcharu]

My 84' Civic with a mild cam and simple header got 54MPG on the freeway at 70MPH. This was with a CARB and that silly extra valve thing that Honda used to do. After I swapped the 130HP Integra engine and trans (lower final drive) my mileage dropped to the mid 40's but never less than 30 even when beating the living crap out it (like running at full tilt to see just how fast it would go - M on the speedo, think to the left side of the odo!)

[Mark Henry]

I find trying to make a high mileage car out of a sports car just sad.
Buy a Honda.

[Dominic]

(IMG:style_emoticons/default/type.gif) Programmable EFI

[johannes]

Skinny tires will help. Go for the original 155 or 165 x 15
High pressure will also help
The slower you drive, the best milage you will get. Going 60 instead of 65 will help.
No cooling issue because your engine will not generate a lot of power. 15 hp are enough for 60 mph.
I owned a 1964 Citroen 2CV. It was rated for 18 HP and could reach 60 mph with a bad aerodynamic shape.

[Root_Werks]

Remember as a general rule:

Torque = Acceleration
HP = Top speed

Lazy, higher torque engines with taller gear get better mpg than high strung short geared cars do.

I know, there are about a million exceptions to this.

I had a 4.5 V8 Fiero that always touched 30mpg averaged with a good tall geared 5spd.

I've also had a 77' 911S all stock that got low 20's for mpg at best driven normally. So much of it has to do with fuel delivery. CIS doesn't compare to EFI systems.

My current 914-4 2.0 with carbs probably gets upper teens. (IMG:style_emoticons/default/icon8.gif) And I baby it. Worthless.

So if you want that 40mpg 914, get any stock FI 914-4, make sure it's tuned 100%. Good alingment, tires (no 205's either) and drive it easy. I bet you'd get darn close in any stock 914-4 FI to 40mpg. Even if you never made it, you'd get close.

(IMG:style_emoticons/default/driving.gif)

[underthetire]

I've been told exactly opposite. You want the engine to be at cruise speed about 40-60% of your max horsepower RPM. Thats why those little fuel efficient Hondas and such run a fairly high RPM on the freeway.

To be blunt, you've been told wrong. The Hondas that get better mileage have taller gears. The CRX HF, in particular, has exceedingly tall gears. That's one of the things that helps it get good mileage. And a number of people have switched to taller gears in several different types of cars, and all have gotten better economy.

--DD

Our little CRX ran about 2.5K at 65 MPH, so I wouldn't call that real tall gears. I mean, if you've got to keep your foot in it to keep going, your putting more air through the motor, causing the ECU to add fuel to compensate. Doesn't make sense to me. The HF CRX was like 1.3 liters, thats why they got good mileage.

[JoeSharp]

Coming back from the Route 66 in 07 Linda used 6 gallons to go 295 miles. She was running 205-50's and stayed above 70 most of the way. She was running twin Solex's with a D-Jet cam. 49.16 MPG
Thomas ran twin 34 Webers and was getting 44 all the time.
If you want to get good mileage cheap look into putting the 34's on your D-Jet and you will smile at the Pump. You will suffer from the lack of head-jerking preformence that you lost from the conversion of the 1700cc's. I have to admit that I did notice a loss of power but the MPG is there if someone wants to do it.
Just from my experience I would do an L-Jet and put it in an early car with the tallest tires I could find. Put in all new wheel bearings and clean and grease the C/V's.
I THINK 60 MPG is waiting for one of Us.

[Root_Werks]

I've always wanted to build a 50mpg 914. (IMG:style_emoticons/default/driving.gif)

I was really on the fence about the yellow 1.8 CAMP914 has. I think that would be a great platform to start with.

(IMG:style_emoticons/default/driving.gif)

[realred914]

my old 1.7 914 would do about 35 mpg driven HARD round trip to yosemite (about 500 miles) lots of hills and windy roads, really had my foot into it, (really hit 100 mph and caught air on a hill) this with 195 50 tires (stock gears) so my rpms were a bit high. this was an ealry car (lighter doors)

i assume if I had high pressure tires that were skinny i would have done better, also would have done better if I had actually tired to go slow


this was the early high comnpression 1.7 with stock FI system. good old real 92 octane gas (now days expect 10-15% lower milaegae on the "new" oxygenated gas shit that the nazi smog folks force on us. I noticed the drop in MPG in all my cars when they switched to the shit gas. just as they said it would do, 10-15% reduction in mpg. dam the californianazi government


keep in mind, depending on the attitude of the jack boot thugs that run your state, your milage may differ with their "new ' gas. (plus it cost more!!!)

[Katmanken]

You want a high mileage car?

Saw a 80-115 MPG Mustang once at an American Society of Mechanical Engineers meeting. It was built by one of the Ford GT engineers that built cars for the 1960's Lemans races. He went into exactly what he did in front of a pack of initially critical engineers, and how he allowed several packs of reporters to beat the crap out of his car for several days to verify his results. Basically, he handed them the keys on Friday and said "Bring it back on Monday". They verified the mileage.

How did he do it?

First thing- replace the V-8 motor with a small displacement 4 banger turbo diesel that had high torque at low revs . That's a max torque at about 1200 rpm and never run it above 1800 RPM. It was rev limited to 1800 rpm.

For today, new engines are available and maybe you should look at Kubota garden tractor engines. I think there is a 2-3 cylinder diesel engine that meets the high mileage requirements and it would sip even less fuel than a 4 cylinder. Not much on acceleration but high mileage.

Go with the proper gearbox gearing to have the max engine torque at 1200 RPM to coincide with 60 MPH.

Use special high pressure tires.

No muffler to impede back pressure.( ie use straight pipes ) Why? With a max of 1800 rpm, it's a little faster than idling and the engine it doesn't make much noise.

A little bit of aero ( plex headlight covers) and that was it.

A high mileage gutlless wonder that never exceeded 1800 rpm.

Wit the normal teener engine, you should never put your foot down on the accelerator or your mileage goes to heck. Put in a rev limiter that kicks in at peak torque. This will cause your top speed to go down becasue you can't exceed peak torque, but hey, your stated goal is simple- high mileage which means not fast.

And I agree with Mark. Why turn a great handling sports car into a low revving gutlless wonder? Wouldn't a garden tractor engined Yugo work about as well or maybe better?

[Root_Werks]

"First thing- replace the V-8 motor with a small displacement 4 banger turbo diesel that had high torque at low revs . That's a max torque at about 1200 rpm and never run it above 1800 RPM. It was rev limited to 1800 rpm."

There you go, torque = acceleration coupled with tall gears and low revs, you've got the formula for high mpg. That's exactly why my old POS V8 Fiero was quicker and got better MPG than any CIS 911 I've ever had. Just the way of things.

I agree, while it would be cool to have a 914 that got 40-50mpg, what would that do to the "fun factor" of the car? If I can drive a 914 like I want and still get 30's mpg, I'd be happy.

(IMG:style_emoticons/default/driving.gif)

[zymurgist]

I find trying to make a high mileage car out of a sports car just sad.
Buy a Honda.

You can have both. (IMG:style_emoticons/default/wub.gif)
(IMG:http://www.914world.com/bbs2/uploads_offsite/www.theweeklydriver.com-4238-1271866765.1.jpg)

[Katmanken]

Yup, and gutless at normal teener RPM's too

That's just sad.... (IMG:style_emoticons/default/biggrin.gif)