912E / Dual Webers / Poor MPG / Help

[fastricky]

Hi all, I proudly own a 912E that has been converted to dual Webers. The car pulls adequately, drives very nicely and I've even mastered how to confidently start it in cold weather (!) My only disappointment is the fuel economy (I do tend to drive with a heavy foot, generally 80+mph) - I'm averaging 20mpg highway. That seems quite low, I'd truly like to get the economy higher, at least 25mpg. Here's a list of work done to the motor:



So any thoughts on what to consider to improve mpg? The car has been tuned recently by a very high end shop here. If anyone can also suggest a Type IV specialist in the NY area that'd be highly appreciated. Danke!

[WFBowen]

You seem to have a nice setup. If you’re getting 20 mpg at 80mph with a heavy foot, I wouldn’t ask for much more. When you switch from factory FI to Webers there’s always some trade off - in your case you’re getting better performance and improved driveability for lower mpg. A good Weber setup on these motors should error on the slightly rich side to avoid any chance of a lean mixture, especially at high speed/rpm. You might have the best of both worlds - when you want better fuel economy you just lighten up on the right pedal. Besides, the price of gas is coming down.
Also, it looks like you have a good elec. ignition system. If your temp gauge stays cool at sustained high speeds, I’d avoid adjustments.
Bill

[fastricky]

Originally Posted by WFBowen

You seem to have a nice setup. If you’re getting 20 mpg at 80mph with a heavy foot, I wouldn’t ask for much more. When you switch from factory FI to Webers there’s always some trade off - in your case you’re getting better performance and improved driveability for lower mpg. A good Weber setup on these motors should error on the slightly rich side to avoid any chance of a lean mixture, especially at high speed/rpm. You might have the best of both worlds - when you want better fuel economy you just lighten up on the right pedal. Besides, the price of gas is coming down.
Also, it looks like you have a good elec. ignition system. If your temp gauge stays cool at sustained high speeds, I’d avoid adjustments.
Bill

Thank you Bill! I'm new to this car and the IV motor in particular so a knowledgeable POV is very helpful. I do notice when I rev the engine enthusiastically in my garage that the exhaust seems rich on gas, so I reckon that is normal / correct? Any reason for me to consider going back to modified or updated EFI in hopes of the performance I'm enjoying now but with better MPG? Also, I've read folks generally aren't keen on the 009 distributor, something I should replace or let be? - Rich

[WFBowen]

Rich
You could double check your timing to be certain it’s showing 27deg @ 3500rpm. Also, you might check the accelerator pump quantity on each carb - it could be set too high, but be sure to save your starting point (current setting) since the 2.0 Type 4 never came with dual carbs so quantity specs found on the internet might be anecdotal.
Bill

[fastricky]

Originally Posted by WFBowen

Rich
You could double check your timing to be certain it’s showing 27deg @ 3500rpm. Also, you might check the accelerator pump quantity on each carb - it could be set too high, but be sure to save your starting point (current setting) since the 2.0 Type 4 never came with dual carbs so quantity specs found on the internet might be anecdotal.
Bill

Cheers again Bill!

[fastricky]

I'll be having the car looked at with the helpful comments in mind. Out of curiousity given the mods to the engine what would be involved in going back to EFI? New pump I imagine, anything else to consider?

[WFBowen]

Originally Posted by fastricky

I'll be having the car looked at with the helpful comments in mind. Out of curiousity given the mods to the engine what would be involved in going back to EFI? New pump I imagine, anything else to consider?

Referencing the motor’s build sheet posted above, I’d say whoever built the engine chose a good setup for a nice street motor. If you were to revert to FI, you’d be changing the cam/lifters maybe ignition, plus wiring, fuel return line and pump, etc., back to stock. Then there’s the problem of sourcing the airflow meter, ECU, intake system EGR, FI system, and other 1 year only parts which have become very rare.
IMO you’ll be going in the wrong direction as the Webers give you a separate throttle for each cyl. placed very close to the intake valve. The original FI system with the thermal reactors was pretty much a smog setup and shouldn’t be confused with the earlier 911 mechanical injection which was a high performance design.
Here in Calif. these cars must pass smog, preventing engine modifications. Most all 912E owners here would die to be able to run your setup.
JMO,
Bill

[fastricky]

Thanks again Bill, I'm looking for that sort of POV as I'm new to this car and don't know anything other than this carb'd version. I do still have all the original FI parts btw if that makes any difference. All I've been going on are the thoughts online and in my informal research got the impression that most folks prefer FI for it's predictable starting and fuel economy which sounds favorable to me... however the performance of the current setup is pretty dang nice, just don't know if that would suffer going back to FI?

[bsherrard]

Fast tricky
Name?
You need to research Jake Raby over on shoptalkforum.com
He is well known for building our 912E motors and getting Great mpg from carbs. It is all in the package and setup.
I think I have seen some of your posts on the 912E forum on 912bbs.
Brook
Bring k

[fastricky]

Hi Brook, thanks. I'm well familiar with Jake and have corresponded with him, he no longer offers parts or kits so not much to gain from him unfortunately. - Rich

[sixbanger]

Any idea what jetting you Are running?

[fastricky]

Originally Posted by sixbanger

Any idea what jetting you Are running?

I don't, but the car is in the shop and I'll report on what they find and where we go with it... thx