The 'Maverick' Classic Porsche Forum and Classic Porsche Club for Porsche 356, Aircooled Porsche 911, Porsche 912, Porsche 914 & Porsche Replicas. 'We join for the cars but stay for the people'
Recently acquired a 2.2T with 2.2S engine 'n' stuff. So now I have myself an S/T
I wish!!!!
Nevertheless it really does move when you grab it by the short and curlies!!! Quite amazing when you consider it is only just over two litres.
However it has a slightly higher compression ratio (2.2S 9.8:1) than the later cars (2.4S 8.5:1) which were designed to run on low octane fuel. Question is whether to run it on 95 regular or 98 high octane.
BTW this is a different car to the one in my rolling road post.
the 2.4's were designed to run on low octane fuel (the shity USA stuff in teh early 70's) out of the box. In fact the CMA MFI manual states not to run 2.4's on high octane fuel.
Using this theory, the 2.2S with its high comp motor should probo be run on high octane stuff like optimax
not wanting to cast disparity or debate, but... I would NOT run a high comp motor on low octane fuel. There is a wealth of material evidencing detonation with comp ratio's over 9:1 with lower octane ratings. The VW scene, which i have a bit of exposure to, has a lot of experience with getting higher horsepower from increasing the comp ratio in an air-cooled motor, and the accepted wisdom is 8.5:1 is a good (i.e. long term, reliable) ratio for 95 or lower octane. of course, a lot depends on timing and fueling, but you are always better to err on the side of caution when it comes to comp ratio's and octane ratings. for the sake of a few pence a litre you're insuring against a multi-thousand £ repair bill. no-brainer in my book.
'53 356 Pre-A (a box of bits!)
'54 Okrasa/Porsche/VW special
'58 356A Super (GS-spec)
'65 Razoredge Ghia
'66 Westfalia Camper
'70 911S (2.3 ST Le-Mans spec engine)
Interesting: I have also heard a lot of talk about octane and CR, but personally I have not and do not experience any problems with my car. It's actually going back on the dyno soon, I might try and do different runs on different octane levels
upping the comp ratio from 9.8 to 10.3 def made a difference for the motor in Banshee - Autofarm recommended only 98 Octane. i half thought about the 102 from BP but at over £2 per litre i couldn't justify it, even one tank as an experiment!
'53 356 Pre-A (a box of bits!)
'54 Okrasa/Porsche/VW special
'58 356A Super (GS-spec)
'65 Razoredge Ghia
'66 Westfalia Camper
'70 911S (2.3 ST Le-Mans spec engine)
Steve, 10.3:1 is a world away from 9.8:1 and with that sort of ratio 98 octane on pre CIS would be a 'no brainer'. It is interesting to note that the 2.2S only runs 30 degrees of advance standard probably due to the high comp, I'm not sure how much you are running. What I really need is to find out what others running 2.2S to my standard spec are using otherwise it's comparing apples with pears but thanks.....
Alan. It'lll be interesting to see if anybody else with a 2.2S chimes in but based on what you say I'll probably go with regular. So where are you going for a rolling road session?
You won't do it any harm running on 98, you just won't see a benefit if the timing is optimised to 95. Treat it to a tank of optimax and see how she goes
Just by chance I've been reading the March/April 1994 copy of 911 & PW (thanks Middlefour!). In that copy is an article written by one Mark Waring and says:
"The 2.4 engine was developed from the 2.2 engine it replaced. When Porsche developed the engine they were mindful of new emission control regulations in their expanding markets of America and Europe. The bore and stroke were increased ............. but the compression ratios were lowered to enable the engines to run on 91 Octane fuel as opposed to 98 Octane for the 2.2 engine."
I, for one, wouldn't argue with Mr Waring.
