Engine swaps, Mpg focused Options

[r_towle]

Leave the SBC and flat6 conversions out of this.

Who has swapped a different engine into a 914?
Something Japanese, great mpg?

[r_towle]

I got 48 mpg from my tuned 1.7 with djet….and I really learned djet that year.
And I learned all about low roll resistant tires….which are great for mpg but suck for traction
But I digress.
Just curious if anyone put a newer FI engine like a Toyota or Honda into a 914

[Superhawk996]

And I learned all about low roll resistant tires….which are great for mpg but suck for traction
But I digress.
Just curious if anyone put a newer FI engine like a Toyota or Honda into a 914

You're on the wrong track with an engine swap. You were on the right track with low rolling resistance tires.

Fuel economy is a function of rolling resistance, aero dynamic drag, and parasitic drag.

Aero drag is almost a fixed variable based on body shape. 914 is already surprisingly good with flat underbody, small frontal area, and small side mirrors, you'll largely need a wind tunnel to tweak it any further. Someone did a nice CFD on 914 aero. If you are serious about trying to improve MPG, you can't ignore aerodynamics.

Here: http://www.cassidy-online.com/porsche914/a...aids/index.html

Tire are ABSOLUTELY the the largest rolling resistance variable you can easily affect. Look at Honda Insight (165/65R14) - skinny, low rolling resistance tires. Sounds a lot like stock 914 tires. But notice, the Insight went 14". That is to reduce inertia of the wheels vs. stock 914 on 15". The larger diameter wheel requires more energy (i.e. lower MPG) to accelerate the wheel up to speed after each stop. You'll also want to keep wheel mass as low as possible (carbon fiber would be ideal (IMG:style_emoticons/default/laugh.gif)). Big meats that look cool and provide awesome handling aren't going to get good MPG.

After that, you're chasing parasitic drag. Need to go to high roll back brake calipers (makes brakes feel crappy), low drag bearings and seals (differential, wheel bearings, etc.).

The actual engine has very little to do with MPG other than it needs to overcome rolling resistance, aero drag, and parasitic drag. As noted by Mark as well as your own claimed MPG, a stock 1.7L driven gently is going to be pretty respectable.

I'm curious if you got 48 mpg; what target MPG are you hoping for and for what purpose? How much gas could you buy with the money spent on the engine swap and/or pursuit of lowering parasitic loads?

If you want more fuel efficiency out of an engine, you're going to end up looking at something like 1.0 - 1.2L, 3 cylinder turbo charged engines.

The Mitsubishi Mirage 3 cylinder is 1.2L - about 76 HP. Sounds suspisciously like a stock 1.7L (IMG:style_emoticons/default/happy11.gif) but will have better Brake Specific Fuel Consumption than a 50 year old air cooled motor.

Or, there is the Ford Fiesta 1.0L 3 cylinder EcoBoost that is good for 123 HP. But if you're on the turbo and making 123 HP, you won't be getting best fuel economy (IMG:style_emoticons/default/av-943.gif) and we're back to square one. Same for the 3 cylinder out of the Mini Clubman which is 1.5L and 134 HP.