TM___

I had previously dialed the pot to 245 Ohm and the CO started at 5% when measured today. We were careful not to turn it down too much and were able to achieve 1% CO, finally settled around 1.8% CO with a pot setting of 70 Ohm. It's very hot here today (35°C) so we ended with a rather richer setting than described in the WSM.
Filled the car up and reset the odometer, let's see now how the fuel consumption has changed. I'll do a 350km drive on Thursday and will report back.

I'm happy my airconditioning is working, I get freezing cold air with the R134a conversion.
I guess running the AC will worsen the fuel economy, any ideas with how much?

Darklands

I think the four hole injectors are at full trottle enrichment too rich! Both cars have at 1 % CO an AFR of 8,5, that's Lambda 0,65.
Drivability is good but we can only change fuel pressure or the MAF settings.
At low power AFR ist 14-15.

An s3 brain with lambda probe can cure this?
Greg told us he use LH2.3 computers with knock detection to improve the S2 performance.

TM___

15,13 l/100km over the last 336km, mainly highway at 125 kmh. That is 15.55 mpg over 210 miles driven.
Could still be better I guess. I expected a bigger difference after adjusting for CO, but let's see how it does over the long run.

Darklands

We need an special chip for the four hole injectors! Would be a job for Porken but I think not many S2 are there!

It's 50% more than Porsches claims.

Lebbon928

Why don't you make the measurement of the fuel injectors? Then you can be sure if these are the problem or if need to look somewhere else. The data in the technical spec books are constant speed consumption (probably without A/C and so on). 15-16 MPG is not so bad for a 4.7 Liter V8 engine.

TM___

Another 450km later, I'm at 16,05 l/100km (14.63 mpg) doing mainly constant highway speeds, with some in town traffic in between. Also, several short trips (< 10-20km), I take it out for almost every trip.
I can live with it, it's much improved over the +- 20 l/100km (11-12 mpg) it was doing before.

I know, a lot more than what Porsche says, but I have never had a car that came anywhere close to their factory consumption claims. City driving leads to 19,2 l/100km according to Porsche, so that affects the average quite badly.

To conclude, replacing the injectors (by a set of 928srus) greatly improved my fuel economy. It may not be as good as some figures I read here, but it's ok-ish.

928cs

What kind of highway speed, in Germany or Belgium?
This seems to be a lot.

TM___

My car shows 129 kmh, which is 124 kmh on gps. That is +- 77 mph.
Speed limit in Belgium is 120 kmh on the highway and there are many radar controls. You can pass those at this speed without getting your picture taken. Anything faster leads to one-photo-session by the government of at least €50.

928cs

That's the reason of my question. My 1987 S4 is around 12 L/100, or less, with the same conditions.

Have you checked that the ignition system is in in order? The twin system of the S2 can be tricky.

Darklands

My 84 S uses 14,8 l / 100 km with the last filling.
FRom memory she should be in the ballpark of the 87 S4 from 928CS
On acceleration, the 4 hole injectors have too much flow.

If you go to the dyno you will see the car misses 30-40 hp because of the rich condition.