Porsche Enthusiasts Club Forum

More questions! lol

The Euro 4.7 has a very high compression ratio of 10.4:1

Does anyone have a problem running it on the standard unleaded you get these days? Valve seat recession? Does anyone use an additive such as valvemaster?

That's a good question.

I have an 84' 4.7ltr Euro and I've been told that I should run it on 98 octane unleaded petrol - but I've never been sure about the 'unleaded' part so I always use a lead additive on the basis that if it does have hardened valve seats then there going to be very well lubricated ones and if it doesn't then I'm protecting them anyway. This does damage my wallet but then I do less than 2000 miles a year so not that much.

The engine was defiantly designed to work with 4-star petrol though which was 99 octane so if you stick in 95 octane then this is enough of a drop in performance to interfere with the ignition timing (or something). ? - so I wouldn't do that - the high performance petrol works more efficiently with your high performance engine so you gain in the long run.

Would there be any difference in fuel recommendations between the 4.7l & the 5.0l engines?

I have the 5 ltr 32 valve engine. I definitely get better MPG on the shell super stuff. It works out cheaper in the long run to pay extra and get more miles to a tank full. How long that lasts with prices going up, I don't know. The car does run better on the expensive fuel. It might be worth an experiment for you. I'm sure I need a new MAF though, so maybe the fuel is helping with that too.

Hi

OK....

Firstly the 928s all have valves and seats suitable for unleaded petrol...

1, You CAN either use standard unleaded in which case there is a link wire by the fuse panel which when connected retards the timing by 6 degrees to stop any pinking BUT you will lose between 6 and 10 hp if you do....

2, Next...Shell Vpower (or equivalent) = full power from engine and you do not need to connect that wire link....

3, The engine runs BETTER on LEADED 5*....I once actually found some at a Shell garage just outside Cambridge much to my amazement..apparently there ARE a very few garages allowed to sell a very small percentage in theory for veteran cars etc....
I had about 1/4 of a tank and filled it completely with 5* (at a huge cost) and within a couple of miles it had a VERY good effect...it sharpened the engine up and seemed to have another 20 to 40 hp.....

Amazing as I didnt really expect it.... but it worked....

Hope this helps

All the best Brett

What do you use Brett? Do you use an additive, or just Shell V-Power? I know your engine has " max'd out" a few times, so a few horses might have escaped, but how does the performance compare now on different fuels?.

Hi Lee

I use VPOWER all the time nowdays...tried "normal" unleaded a few years ago and as it pinked slightly , I used the retard wire... and the engine seemed "flat" if you see what I mean...

When I am using my Nitrous I have another 8 fuel injectors which are designed (for safety) to run rich so I never have a leaning out problem, I also have a wideband connected to my Maxx Extreme Race so IF it did go lean for any reason it would cut off the Nitrous and go extremely rich (rich enough to bog the engine lol)

Actually I was thinking last night that I probably have the most electronically assisted 928 ever lol.... Rear view camera, Lcd rear view screen, Wideband, Fuel pressure transducer and gauge, Nitrous pressure transducer and gauge, Nitrous controller, 2 Nitrous gauges, Data Logger including Rev counter and digital speed readings, oh and another Rev counter with gear shift lights (Autometer) and of course the cars rev counter (that makes 4 rev counters including the Maxx one) oh and a digital voltmeter in the Maxx....and a few other things I probably forgot lol

All the best Brett

That's good news about the valve seats! My current engine has no lead additive as I couldn't care less if the valves recess but I don't want a bit of harm to come to my shiny new V8

I have no prob spending the extra cash for the 98 stuff as I also only do a couple of thousand a year, but was worried about those times when you are low on petrol and the station only does 96 or something.

I can always get those wires connected to a switch on the dash that says 'road' and 'race' I assume it is just one output of the ignition ECU that I connect? Might have to trace someone's wire to find which one it is!

Oh and I wish I had this many replies for all my questions

Hi

To be honest you wont need that wire link on a couple of thousand a year... I seriously doubt it will pink...

You will normally get a LOT of help here as Tipec members (and 928 owning non members like me) are known to be helpful

You will get a lot more responses and help here than in the other non mentionable place that I used to run lol

All the best Brett

They don't supply V-Power or Tescos 99 over here in Northern Ireland.

Can you recommend anything else, or am I stuck with the standard stuff?

wot about that funny clear stuff they make up in the hills over there, most things seem to run well on that

Am sure that would work great, but it's a bit more expensive then £1.32 a litre

well yeah but you could always have a few nips yerself, and you wouldn't notice if the car was running a bit rough

BP Ultimate?

Isn't BP Ultimate now 96 or 97? They discontinued the 102 stuff.