Hey Jake what do you have for us on the MPG engine Options

[toon1]

78 x 90mm is a great combo. The valves are only shrouded if the valves are to big for a mileage engine. Short strokes with large bores are great for racing and any high speed engine. Long strokes and small bores are great for low speed torque engines. They, by nature, require less induction. The smaller quench area of the bore means better thermal characteristics. Stay with a rod ratio around around 1.7 for even better mixture motion during quench. This combo is not nearly as easy to build as a 1911, and cost more, but would make a great DD. And if money is really no object, add a second set of spark plugs. On that tiny bore it would up the mileage even more. I believe 50MPG is realistic.

What does " the valves are shrouded " mean?

what does " keep the rod ratio around 1.7 mean?

how would this combo perform with the stock 1.7 heads and a 9550 cam? (IMG:style_emoticons/default/idea.gif)

[Todd Enlund]

78 x 90mm is a great combo. The valves are only shrouded if the valves are to big for a mileage engine. Short strokes with large bores are great for racing and any high speed engine. Long strokes and small bores are great for low speed torque engines. They, by nature, require less induction. The smaller quench area of the bore means better thermal characteristics. Stay with a rod ratio around around 1.7 for even better mixture motion during quench. This combo is not nearly as easy to build as a 1911, and cost more, but would make a great DD. And if money is really no object, add a second set of spark plugs. On that tiny bore it would up the mileage even more. I believe 50MPG is realistic.

What does " the valves are shrouded " mean?

what does " keep the rod ratio around 1.7 mean?

how would this combo perform with the stock 1.7 heads and a 9550 cam? (IMG:style_emoticons/default/idea.gif)

Shrouded valves means that the valve is close enough to the cylinder wall that the cylinder wall actually obstructs the flow.

Rod ratio is the ratio of the stroke to the rod length... rod length/stroke=rod ratio.

I can't answer the last one :-)

[Dave_Darling]

...What compression ratio should I am for? Or does this depend on the cam I have? which leads me back to finding out the cam. (IMG:style_emoticons/default/headbang.gif)

The cam can dictate what compression you need, and your choice of cam can be influenced by what compression you want to run.

Sorry....

--DD

[RJMII]

...What compression ratio should I am for? Or does this depend on the cam I have? which leads me back to finding out the cam. (IMG:style_emoticons/default/headbang.gif)

The cam can dictate what compression you need, and your choice of cam can be influenced by what compression you want to run.

Sorry....

--DD

Thanks, Dave!

I got the builder's e-mail address, so hopefully I can get some answers as to what I've got for a cam so I can complete the build.

[Chris Pincetich]

No doubt twin plug is our best bet for best performance and burn - that's what Jake's dyno day high MPG engine uses.
But for those of us that $$$ is an object with limits, where does multiple spark discharge like MSD and others come into the equation?? If one designs a TIV to run in the low rev multiple spark range, like 2.5-3K rpm, is it effectively like having twin plugs?? Or is the twin plug location(s) the big gain?
Would a 1911 with Ljet be tuneable for higher MPG vs. Djet vs. carbs??? Some SoCal folks claim 40 mpg on carbs, but common wisdom is EFI (even the old kind) is more fuel efficient.
Let's discuss (IMG:style_emoticons/default/beerchug.gif)
BTW - my stock 1.7 with 13lb flywheel and header kicks @$$ and gets 30 mpg on the highway (IMG:style_emoticons/default/beerchug.gif)

[Jake Raby]

Keep this realistic!!!! Quit the day dreaming and hypothetical design!

Of course we can create 50 MPG- we have already done that! The Super 2 liter is a proven combo and is being further developed as we speak, but not a single person reading this can assemble that engine other than yours truly, because its a real bitch to build. Its also one of the most expensive engines I can create, for the HP output it IS the most expensive.

That said, the old 140K mile engine in my 912E has been my driver car this week as I broke it out of moth balls to get some MPG figures. Today it still gets 35 MPG after not having an oil change for 10K miles.

The 1911 is the combo. Cheap. Reliable and effective...
You guys just don't like it because you are stuck in the "Bigger is better" mentality, in that case I'll suck your wallet dry and won't get you much more MPG than the 1911 will at 1/3 the price. You'll swear the 1911 is a 2056-

[johannes]

Jake , as your engine runs cooler , what about removing fans to the blower ?
Thinking about alternator. Won't a 914 with a modern battery need less amps ?
Both should provide fuel economy ?

[Jake Raby]

Battery voltage increase ignition system voltage. More charge energy= more power at the spark plugs, so you would not want to reduce that.
Street driven 914s need to retain their fan impeller blades...

[RJMII]

Ok, so I got an email back. I've got a scat cam... no idea on the lift or duration, so I need to do some more research. AND... I'm starting to think I need to double check whether it was a 1.8 or a 1.7 to start out with. The car is a 73, has 73 FI.

Here I go needing to look at my heads again to find out what they are. All this time I thought they were 1.7 heads.

Differences between 1.7 heads and 1.8?

[Todd Enlund]

Differences between 1.7 heads and 1.8?

http://www.tunacan.net/t4/tour/heads.shtml

[RJMII]

Differences between 1.7 heads and 1.8?

http://www.tunacan.net/t4/tour/heads.shtml

Thanks! that's a great website, much appreciated.

[r_towle]

look at the top of any page here, there is a button way up top called 914info.

Look around in there...

Rich

[RJMII]

OOPS. I really didn't mean to ask that. At the beginning of my post I said I had more research to do, and typed that out in question form instead of statement form that it was one of the things I was researching. Both Jake's site and Tunacan have been a great help in IDing parts.
Mr. HAM Inc posted to me in another thread that it didn't matter which 1.7 head I had, that I should just build with what I can afford, what I have if I can't afford something new (or something like that. really friendly and helpful advice, thank you sir)

So, thank you Jake, Tunacan man, and Mr Ham inc, Rich (for pointing out the link up top) It's making my research go much easier, as I have a tendency to research things several times when I get paranoid that my memory is failing from having certain health issues.

So, again, thank you for the help. I will make sure not to play jeapordy in my posts now.

[Mark Henry]

If you want great MPG the engine is only part of it, get rid of as many pounds as you can, thin tires stock 165/15's, make sure bearings and brakes are in perfect order, leave the top on, windows up, no rabitt starts, no hard braking, keep it to 55mph, etc.

To me this sounds like in a 914 it would get pretty boring.....

[Todd Enlund]

To me this sounds like in a 914 it would get pretty boring.....

That's why I thought about a Type 3 Squareback. Not much heavier than a 914. Much lighter than a Type 4 (411/412), and better looking too.

[pete-stevers]

great read!
of course there is a tdi option as well, but my bet is 1911 would still be a the best option dollar wise

[johannes]

great read!
of course there is a tdi option as well, but my bet is 1911 would still be a the best option dollar wise

That' what i call digging out an old thread....