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Thanks!
I talked yesterday to one German S2 manual owner who changed his injectors to the Denso ones and he told me his car had after that a consumption of 18l /100 km.
After changing back all was like before, normal fuel consumption.
Just to be sure: do you mean the injectors from 9zwo8 are 'bad' ones, and fuel consumption of 18l was worse than before?
We took a trip to the Champagne region this weekend with the 928 and I took the toll-free scenic route. Apart from the first 45km which were highway (130 kmh), most of it was 90 kmh from village to village. This was altogether 440km of fuel efficient driving. We were with friends and did some mixed spirited driving during the weekend for another 100km.
Over the total of 550km, I averaged 15.5 l/100km (15.1 mpg). We'll see if my regular trajectory (mixed town/highway) will be better with the new air temp sensor.
I had contact with the workshop in Roth, Germany who worked on the car while it was at the seller during 2021-22. They were asked to straighten the car after it was stored for many years (probably 20y, since the tires it came with looked new but were from 2002). Timing belt, water pump, spark plugs and clutch were replaced and the car was jerky under partial load.
He replaced the injectors with a set compliant with the factory specifcations, according to his supplier. This solved the jerkyness. The car was still not 100%, so the seller took it to another workshop, who replaced the new bosch sparkplugs with NGK plugs, and also had the MAF refurbished.
When I had it inspected, it ran fine. I bought it and took it to a respected 928 workshop here in Belgium, and the mechanic was also quite pleased with how the car runs.
He didn't find anything unusual which would explain the high fuel consumption.
I still don't have a definitive answer on which injectors are installed, but they could very well be similar to the ones you linked above. The invoice was however €850 + VAT for the injectors alone (without labor).
My contact tells me the China copies have all the Denso script like the ones this shop sells and can be found on Alibaba way cheaper but 220 € isn‘t also much.
I can‘t say the injectors from the link are copies but I‘m skeptical.
Nice pictures from the trip to France. Why has the car no distance shims in the back?
If the car don’t loose water yet you should monitor your coolant level regularly.
Dangerous is if one bore is full of coolant if the car sits longer in the garage and if you crank it the water breaks the block.
Better doing the gasket job planed so you can moderate the time frame.
I let my engine refresh after water consumption and the car was month away.
Hm, my coolant level is getting lower, I drew a line on the tank at where it is now. There are no puddles of coolant on the ground, so it must be going somewhere else. This is bad news I suppose?
I also took a better look at the injectors. They don't have 'denso' written on them, only a part number 0 280 150 252. The other side has no script.
They look exactly like these: ebay
You have the car half a year?
I would inspect and tightened all hoses. After a long drive I would check CO in the coolant in a shop.
It's not a lot of fluid you lost, could be the cap or heater and so on.
Your injectors should be fake!
Look Here: Original Bosch Logo and every field has a number in it.
Yes, I did see lots of those orange ones with prices going from 10$ a piece on alibaba to 100$ a piece elsewhere, having that bosch serial number imprinted.
The workshop (independent Porsche workshop in Germany) who installed them had them delivered by their regular supplier and charged €850 for the set of 8 (while at the previous owner, a car dealer in Germany). Someone down the line probably made a huge profit there.
I was looking at that set of bavarianwerke you bought, but out of stock now.
I wrote something above!
It's not much fluid loss in a half year.
Test CO and look at all tubes, clamps, heater cores, coolant reservoir and the cap.
Inspect the bores with a camera, if you have a clean piston you have water in this cylinder.
If not I would look often but let it go.
You can buy the injectors from Roger, A little bit a PITA with custom but the price should be the same as from bavarian.
Just a thought, from outside the box: I see that yours is a 5-speed. I discovered that my 86.5 5-speed had poor gas mileage (10-11mpg) when I started to measure it. I took it to my mechanic and he said "let's go for a drive". When we returned, he knew for certain what was the cause: my right foot! Specifically, my shift points tended to be high in the rev range.
If you have a similar practice, go for a long drive and never shift above 4000 RPM, then check your gas consumption. My gas mileage doubled when I started doing so!
The coolant leak was not too heavy indeed, but I had my car looked at by a well-respected 928 mechanic in the Netherlands (Garage De Loods) for this and the steering rack.
The head gaskets were on their way out and leaked coolant. The engine came out and finally had a complete rebuild. You do it once and you do it good.
So this means everything was inspected, and vacuum lines were replaced where necessary. Spark plugs are the right ones, and these injectors in mine are apparently the same as those sold by 928srus (which is where my mechanic buys his as well). He recognized the writing on the connector hoses.
Fuel pressure regulators were new, and fuel pressure in the rails is according to the WSM spec.
Everything is how it is supposed to be. He checked the CO and it is still running rich. I had adjusted the pot on the MAF back to 380 ohm last year. When I bought the car in 2022, it was around 0 ohm.
He dialed the MAF back to get the CO down, but at its minimum value, it is still running rich. The MAF was even switched with a known newly revised unit, and the results were exactly the same. The MAF is thus good.
My mechanic found it strange as well, the fueling system seems to be in order, the MAF is good, both temperature sensors were replaced by original ones, but the engine is still running rich.
When we were talking about this when I picked up my car, he suggested we could try and install adjustable fuel pressure regulators to lower the pressure in the rails, as a kind of last resort. I mentioned the ECU, but they rarely fail like this.
I drove home with my 'new' engine and noticed it was indeed still thirsty.
As I was going through my earlier posts, I discovered that the octane loop on the EZF unit was still closed. It was like this since I got the car (it came from a country with inferior fuel). The air temperature was thus completely ignored. I unplugged the loop and hoped it would bring down the consumption too, but alas. I drove 750km since I got it back, and did mainly long distance (it's been only 1 week) visiting friends around the country. It's using 18,2 l/100km (12.9 mpg), mainly on the highway doing a constant 125 kmh (77mph). I would say this is even worse than before. I did have to vary the revs as I was running in the engine, and I noticed the revision brought quite a few horses back to life; but I did 750km and most of them were very civilized.
I will check the fuel pressure again per the WSM.
Before throwing more parts at it, I would like to eliminate the ECU as well. @Darklands if your offer to let me try your spare computers still stands, I'd like to give this a try somewhere in the future. I'll first drive more and see how the consumption evolves. A 'new' engine may drink a little more in the beginning too.
Great! I appreciate it very much!
I'll drive some more first to see where it settles after the rebuild.
It just started snowing here and temperatures are below 0°C the coming week. Unfortunately my garage is almost as cold as outside, so not ideal to get work done. (doing the cluster swap now)
I went over the fuel pressure again today.
At idle it's at exactly 2 bar (29 psi), disconnecting the vacuum from one of the regulators (in back of the engine) raises the pressure to 2.55 bar (37 psi). Jumping the fuel pump relay without the engine running also gives a 2.6 bar reading.
These are all according to the specification in the WSM.
After shutting the engine down, the pressure raises during the next 10 minutes or so. The WSM dictates at least 1 bar remaining after 20 minutes. Mine is still more than 2 bar at that time.
Pulled a spark plug and it is quite black.
Checked the MAF reading and it was at 250 Ohm. Dialed it back to 170 to make it leaner.
Mixed use, but mainly highway over the last 280km, it ran at 20 l/100km, which is definitely worse than before the rebuild (I ran the MAF before at 180 Ohm if I remember correct).
Now that I have the fuel consumption gauge in the cluster, it tells me it should only be using 10 l/100km when driving 125 kmh.
If the pressure is correct, than either the injectors are spraying too much, or the ECU is telling them to spray this much.
Since the fuel consumption gauge is based on the injector pulses combined with the speed of the car, I would think the ECU is fine. That would leave the injectors.
Or I have a fuel leak somewhere, but I think I would have noticed right?
I'll drive another tank of fuel to see if my MAF adjustment leads to something. After that I'd like to swap the ECUs to rule those out.
The units in my car are: 928.618.123.00 (Bosch 0 280 002 501) and 928.618.124.00 (Bosch 0 227 400 012).
03-26-2023, 04:19 PM
