Fuel additive??

[pincher]

Hello,I have just got myself a 944,been waiting about 24 yrs . I was didgging about in the boot and i came across a bottle of fuel additive, Will a 1985 pre oval dash 2.5 944 have to have the additive put in if i use unleaded juice ??

I never thought about this,i just assumed unleaded would be ok on a 85 model.


Thanks Dave

 

[Northern924]

Unleaded is perfectly fine with all 2.5l engines, don't know why the PO would have been putting in an addative, not required on that engine at any age

 

[Eldavo]

Depends what sort of additive it is though. I put injector cleaner additive in with every tank for example.

 

[944 man]

Early cars certainly want 98RON fuel, but all Porsches have been able to run on unleaded fuel since the early seventies. Most additives are usless, or worse than useless too; particularly when you realise that there are four points to one RON octane rating. NF is the exception to the general rule, although I dont think that the new(ish) recipe is as good as the original and normally aspirated cars arent going to see a tangible benefit over V-Power.

 

[pincher]

Many thanks all, Perhaps the bloke just left it in the boot for some other reason, But thought i had better ask the question as i dont want to kill my valves

Thanks Dave

 

[Northern924]

DOn't worry you'll be fine, just fill it up and take it out for a long drive, best way to keep the internals clean[]

 

[david924s]

ORIGINAL: 944 man

Early cars certainly want 98RON fuel,

I had an early 924S 2.5l and that ran fine on 95RON and indeed was indicated as petrol of choice on the filler cap.

 

[MRGT]

According to my 86/87 handbook, Lux's need 97 Ron and S's 95 Ron.

Howard

 

[Gary C]

Unless the previous owner has had it chipped to run on higher octane ?

Is the additive lead replacement or just an octane booster.
Would be more likley on a Turbo though.

 

[944 man]

ORIGINAL: david924s

ORIGINAL: 944 man

Early cars certainly want 98RON fuel,

I had an early 924S 2.5l and that ran fine on 95RON and indeed was indicated as petrol of choice on the filler cap.

I too have a 924S, although I dont know what it says in the filler cap.

In this instance a 924S isnt an 'early car', which would be a series one 944, because its a series two engine. If we were talking about brakes or front suspension of course, then 'early car' would apply to 924Ss also.

 

[Mike_Pollock]

My '83 wants 98RON according to the filler cap.
You cant chip the early cars in the same way you can the oval dash cars, so I'd go with 98 + , I usually use Shell V-power.
It sounds different on the different fuels, and has sharper response on the 99.
Mike

 

[944 man]

ORIGINAL: 944 man

ORIGINAL: david924s

ORIGINAL: 944 man

Early cars certainly want 98RON fuel,

I had an early 924S 2.5l and that ran fine on 95RON and indeed was indicated as petrol of choice on the filler cap.

I too have a 924S, although I dont know what it says in the filler cap.

In this instance a 924S isnt an 'early car', which would be a series one 944, because its a series two engine. If we were talking about brakes or front suspension of course, then 'early car' would apply to 924Ss also.

In my rush Ive overlooked the obvious reason. The modified series two engines found in the 924S run a far lower compression: hence the 95RON sticker.

 

[david924s]

ORIGINAL: 944 man

ORIGINAL: 944 man

ORIGINAL: david924s

ORIGINAL: 944 man

Early cars certainly want 98RON fuel,

I had an early 924S 2.5l and that ran fine on 95RON and indeed was indicated as petrol of choice on the filler cap.

I too have a 924S, although I dont know what it says in the filler cap.

In this instance a 924S isnt an 'early car', which would be a series one 944, because its a series two engine. If we were talking about brakes or front suspension of course, then 'early car' would apply to 924Ss also.

In my rush Ive overlooked the obvious reason. The modified series two engines found in the 924S run a far lower compression: hence the 95RON sticker.

The early 924S 1986-1987 were 150bhp and ran a compression ratio of 9.7:1 which is actually a higher ratio than the 944 150bhp from 1983-1986 which ran a ratio 0f 9.5:1. The later 924S 1988 with 160bhp ran a ratio of 10.2:1 the same as later 944s

So working on that basis if a 924S 9.7:1 can run on 95 fuel then I would have to presume a 1985 944 with a ration of 9.5:1 would have no issues running 95RON unleaded.

 

[Mike_Pollock]

Thats an interesting table, where is it from?
My 944 book by Peter Morgan shows very different figures! ie 1982-5 Euro models 10.6:1 cr 163bhp DIN @ 5800 rpm.
Would like to know more, I've always 160 - 165 quoted for the 2.5 n/a models.
Mike

 

[944 man]

Whilst Im not going to argue with what David is saying broadly (certainly I follow his reasoning), the series one 944 didnt have 150bhp, it had 163bhp. Perhaps the compression ration figures belong with the American power output figures?

 

[pincher]

shall i run her on 95 or 98ron or does it not reaaly matter ???

Thanks

 

[david924s]

ORIGINAL: A9XXC

Thats an interesting table, where is it from?
My 944 book by Peter Morgan shows very different figures! ie 1982-5 Euro models 10.6:1 cr 163bhp DIN @ 5800 rpm.
Would like to know more, I've always 160 - 165 quoted for the 2.5 n/a models.
Mike

It's from here http://www.connact.com/~kgross/FAQ/944faq.html and I think the table identfies the US and EU versions.

 

[Mike_Pollock]

The more I look at that table the less it makes sense. The early cars have always been quoted at 163 bhp and have stickers in the fuel caps saying 98RON - this would not be needed if they were only 9.5 : 1.
Also the oval dash cars had lower c/r to run on 95RON with better engine management accounting for the losses keeping the output the same - this is for Euro models.
Anybody got any Porsche original docs?

Mike

 

[david924s]

ORIGINAL: pincher

shall i run her on 95 or 98ron or does it not reaaly matter ???

Thanks

Forgetting the compression ration discussion (I agree the list may be tainted by US spec stuff) and back to your question I found this

The official memo from Porsche states 944 1982-85 must use 98 (97) ron only and cannot be adjusted so super unleaded is preferable or if not available use L R P With any Porsche, lead is not the issue its the octane rating As a point of interest the only water cooled Porsche that will not run on regular unleaded is 944 1982-85 (source; Porsche tec. bulletin 25/05/99) regards Bert Gear - 20th June, 2000 which may answer it came from here​

http://www.titanic.co.uk/FAQs/FAQ39_944Petrol.html

 

[Mike_Pollock]

Thanks for that link/ article, David, it confirms what is on my filler cap!
Mike