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78P930 12-29-2006 08:12 PM

Fuel Consumption
Does anyone know, specifically, what Porsche changed in 83 to bump up the torque from 303 to 318 and increase fuel mileage from 18.5 to 23.9 at 75mph.

RarlyL8 12-29-2006 08:44 PM

Where did you get that information?

9dreizig 12-30-2006 07:17 AM

yeah I don't believe that 23.9 number , must have been downhill!

A930Rocket 12-30-2006 01:35 PM

All I know is I get 3 MPG at the track. That's just less than one lap around VIR....

Noah930 12-30-2006 02:06 PM


Holy schite!!! :eek:

Of course, what's your (s)miles per gallon figure? :cool:

RarlyL8 12-30-2006 04:54 PM

You can get close to 24mpg with a properly tuned CIS and a few mods but that is a different topic.

I was just wondering where the information came from that shows a difference in power output along with mileage for the Euro 930s. All I have read states the Euros were basically unchanged from '80 to '85, putting out 300HP.

Craig 930 RS 12-30-2006 05:07 PM

Got 25 mpg with the (EFI) 3.6 Varioram SC at 75 on a 180 mile trip.
I'd be amazed to get close that in a CIS Turbo. I got 14 mpg freeway..and a great 5 mpg on!

briankeithsmith 12-30-2006 05:54 PM

When I bought my 83 930, I drove it home from Cape Canaveral FL to Charlotte, and ended up getting 22.9 MPG on the trip home.

Now, I'm like A930Rocket, if I see anything above 5mpg, it means something is WRONG.


Chuck Jones 12-30-2006 06:27 PM

I get 11.6 to 13 mpg even when I drive it judiciously...I've seen some of the posts that claim 18 or higher....all I can say is ....How did you do it?

78P930 12-30-2006 07:44 PM

I found it in an old Porsche book by Michael Cotton, but obviously not real world numbers. I think the best I ever got in my 78 was 19mpg on the highway @ 70mph. I haven't checked it since modifying my engine.

RarlyL8 12-30-2006 08:37 PM

Modifying your CIS based engine does not mean giving up fuel mileage on the freeway.
A rebuilt and properly tuned fuel head and WUR are capable of delivering over 400HP at the crank and 22+mpg on the freeway. I would venture to say that the vast majority of CISystems in service are not in optimum working order due to age and neglect. Most 930 owners also don't tune their hopped up motors with fuel mileage considered.
We should start seeing this reported more frequently on both Pelican and Rennlist. Several companies now produce infinitely adjustable WURs and fuel heads for those folks who do not wish to tackle the job themselves.

78P930 12-31-2006 05:32 AM

Do you know of any books that tackle CIS in detail? Also, who is making adjustable WURs and fuel heads?

NathanUK 12-31-2006 06:17 AM

You need to talk to Brian Leask, he can modify your WUR and tell you how to check your car before you send it so he can set it up ready for you. Of course you can also fine tune it after if you wanted to using an AFR meter.

Most people use an Innovate.

You can buy them from Stephen Kaspar of

The WUR from Brian Leask

Craig 930 RS 12-31-2006 07:27 AM

Brian Leask does modify WURs and does a great job - and provides excellent instructions. Be aware that you ought to be ready to adjust it yourself and have an AFR setup to properly do so. The fuel head itself may or may not be necessary - this right from Stephen - and it isn't adjustable (and doesn't need to be) FWTW.

I have both, and once winter eases up, I plan to final tune it.
Right now I'm at 438 RWHP and 396 lb ft tq.....

911boost 12-31-2006 10:12 AM

On my first tank of gas I got 17 mpg, that included half on the interstate and the other half taking friends out for some bistering acceleration rides. I do know that it needs to be tuned for the elevation, and I expect forthe mileage to get better.


RarlyL8 12-31-2006 10:50 AM

Fuel heads ARE adjustable and may need to be adjusted in higher HP engines. They may not need to be MODIFIED as iA has done. There is a difference between adjustment and modification.
The fuel head must match the WUR adjustment ranges for your specific application. Age can also cause a fuel head to be out of spec.
A set of CIS diagnostic tools is maniditory to know where you are now and when you get to where you need to be. Of course you also need to know where you need to be.

I have several books on CIS and will list them for you when I can get to it. None of the books goes into much detail concerning adjustments or modification but they do tell you how each component works. You take the next step yourself.

Noah930 12-31-2006 12:04 PM

To go back to the original question: no, don't know if there were any changes to the '83/'84 motors. Where did you get those figures?

To respond to the side discussion on MPG: on my stock US-spec '87 motor, I get 24+ mpg on the highway at a steady 70 mph. If I bump it up to even 80 mph, it drops down to 20-21 mpg. Spirited street driving will see it plummet to 12-14 mpg.

RarlyL8 12-31-2006 12:51 PM

Probably the best book I have for troubleshooting CIS is titled "Solving Bosch Continuous Injection System (CIS) Problems" by James Weber.
The tools you need are a fuel system presure gauge and a Gunson Gas Tester. An LM1 is even better but rather costly at $300+

Has anyone come up with an answer to the original question posted?
Were there changes made to the Euro 930 engine in 1983 that increased both torque and fuel mileage?

Craig 930 RS 12-31-2006 02:03 PM

Tell us how you adjust the fuel head non-invasively, Brian.
Height of metering rod reach via shim or ?

F350Lawman 12-31-2006 03:04 PM

I get 13-14 MPG combined during relatively conservative driving interrupted by semi-frequent moments of insanity.

It only takes a few full boost lift-offs to ruin some real nice MPG numbers...but it's worth it! :cool:

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