Boxerworks.com

Hi All, I have searched high and low for info on the correct fuel rating for my 1978 R80/7, in NZ I can easly get 91 or 95 RON and sometimes 98' would be nice to know what it needs but I am suspecting it would be fine on 95, the bike is fitted with aftermarked electronic ignition.
Re rated HP for these bikes, in my search looking at specifications I have come across diffrent rated HP and some showing 2 HP rating as in HP/KW 54/40, 50/37. has anyone any idea how I can tell what my bike would be, it was first sold through a dealer in the UK.

Thanks

The BMW repair manual quotes two figures for a high compression (9.2:1) engine and a low compression (8.2:1) engine. The manual quotes the low compression engine as 37Kw (50 bhp) at 7250RPM and the high compression engine as 41Kw (55 Bhp)at 7000rpm (The '79 brochure actually quotes the latter as 40Kw). A footnote in the repair manual suggests that the lower compression ration is itended for 'regular' or (standard grade) fuel.

Fuel grading is more problematic. The nomenclature for fuel grades has changed over the years and also differs between territories. Working from memory, back in the day, standard or regular grade fuel was 91 RON, Premium was 95 RON, Super was 99 RON and Super Plus was 101 RON. These days (in the UK at least), regular fuel is rated at 95 RON and Premium or super at 98 RON (91 ROPN isn't generally available).

As has been said, using the MaxBMW or Real OEM websites will tell you what compression engine your bike left the the factory with but in the 40 odd years since the bike was produced, anything could have happened so the only real way to tell (if it really bothers you) is to calculate the compression ratio.

In practice, I don't think you would see any difference and in my experience, you won't see a lot of difference using different fuels. They all seem to run pretty well on 95 RON and I can't say I've seen any difference when I've experimented with 98 RON.

If you were expecting a straight answer to either question, I'm afraid you aren't likely to get one... these are BMW's after all

Rob

Octane listed on the pump, at least here in the States, is an average of RON (Research Octane) and MON (Motor Octane). RON numbers are generally higher and can be above 100 for premium.

https://www.sae.org/publications/techni ... 7-01-0662/

As far as I can see, AKI (average Ron/MON) is only used in the US and Canada. Other territories make do with RON on it's own...

In the UK, Octane numbers are seldom, if ever, posted on the pumps. You've got 'unleaded' or 'super unleaded', take it or leave it...

Your link above has an interesting list of the standards used in various territories.

Rob

Here in Norway they put up to 10% ethanol in the 95 octane, but none in the 98. 98 is only sold by Shell and Esso.

Here the 95 may have up to 10% but 98 may have up to 5%. Some 98 still has none and some companies have none in some regions of the country. It's a real mess.

H i use 95 ron unleaded form any uk pump on my 55hp r80/7 and never had any trouble, except that one time in the highlands when I bought fuel contaminated with water which left alone in the dark in Glen Gary, took out 1/2 a litre of water when I finally got home. How ever before I switched to modern unleaded from 4 star I had to have new valve seats due to the lack of lead in the fuel. I did not do this to my vw beatle which dropped a valve after 20,000 miles on unleaded.

mkj wrote: ↑Thu Jan 06, 2022 4:58 pm H i use 95 ron unleaded form any uk pump on my 55hp r80/7 and never had any trouble, except that one time in the highlands when I bought fuel contaminated with water which left alone in the dark in Glen Gary, took out 1/2 a litre of water when I finally got home. How ever before I switched to modern unleaded from 4 star I had to have new valve seats due to the lack of lead in the fuel. I did not do this to my vw beatle which dropped a valve after 20,000 miles on unleaded.

Yes those VW motors were prone to that as the valve stems used to go brittle, when I worked in an Engine Reconditioning shop we used to take the valves and holdeing the valve stem tap the vleve head on the vice, 9 times out of 10 the valve would snap where the machined end of the stem ended, in the end we took no risks and replaced the lot on every rebuild.

SteveD wrote: ↑Mon Jan 03, 2022 12:25 am Try sticking your vin into www.realoem.com
That should tell you the kW.

Thanks, already tried that but nothing comes up as in powere and so on, unless I am missing somthing.