Larger throttle for D jet, Sort of a how to Options

[colingreene]

So, I sometimes work for someone with a really nice 914, his car had always been handicapped with a single carb. Obviously that was never going to work all that well and he grew tired of how poorly it ran.



Eventually he said to me, i just want fuel injection after i tried to encourage him to run dual carbs.
Not one to shy away from a challenge I bought a SDS off of McMark. we did get it to run but honestly it kinda sucked. (not at all marks fault) so with that experience over eventually we bought a microsquirt. Would not have been my first choice but hey budgets are what they are.
Bunch of fussing around later and we have a car that runs sort of ok. Never did make sense of why it was so variable.
I do think that all things considered a microsquirt is a good option if you are willing to tinker a bit to get it to work.

I did previously do a lot of things with Subarus as a product development engineer Often that meant checking if the intake system was sealed. I brought that testing into this by deciding to smoke test the intake tract.
Turns out the factory throttle body smoked out of the shaft quite badly.
not to mention the seals from the runners to the plenum (solved with ugly hose clamps for now)

On the hunt for a throttle body repair I found not a lot of great options out there.

http://www.914world.com/bbs2/index.php?showtopic=376444

I had read this and thought, "Ah, yeah ill get a go westy throttle body."

Heres where the issue surfaces. My car has always had dual carbs on it. I bought it with fuel injection and early on i asked how well the factory fuel injection would support a larger motor and was told "not well". Not to get political but I like carbs and they seem to like me. buttttt this leads to the next problem.

I was unfamiliar with L jet/D jet differences.
the throttle body came in. (its quite nice) and i quickly figured out this "wont work"

So this should cover some of what I have done to make it work on the D jet plenum as a bolt on.
This also assumes that you are using a aftermarket ECU.

First for starters the throttle position sensor bracket will run right into the plenum.
and the throttle shaft is a bit long for the sensor I was running, I have seen in the past where people have poked a hole in the cover of the sensor and let the shaft poke though.
Of course I was not going to do that. I nipped the throttle shaft shorter and cleaned it up. Ok that problems solved.



the bolt pattern was set up for smaller bolts than I had so they were opened up with a file. Next time i do this I think i would do it in a mill.



Next was how to solve the bracket running into the plenum. I took a grinder and cleaned up as much of the metal that sticks down on the bracket for the TPS to minimize the interference.
Still we had issues. So a notch was in order. with it notched it fit, neat.


But the throttle arm for the cable sticks out too far and needs to be minimized.
I was able to salvage off of the original 2.0L throttle body the bracket that holds the cable, and cut off the new loop for the throttle.
The original needed to be kept because it was what worked as the throttle stops for open and closed.
I took the throttle linkage apart, swapped some fatory parts on and turns out it works great.
I did have a sticky throttle however that was tracked down to not cutting the throttle shaft end where the tps mounts a bit too long. easy solve there.

The factory gasket that the throttle comes with cannot be used, so that was removed and the factory paper gasket was used with some light sealant.

of course once i put all this together i needed to start it, problem was someone left the key on with a already weak battery. will have to check it out when I get a chance.
Also will be re dyno tuning it with this new throttle and the plenum fully sealed up.