Fuel octane rating

If you need technical information or help with your BOSCH ignition squarecase Ducati 900SS - Darmah engine - post your FAQs, comments & questions here.
Post Reply
Russell
Cucciolo - the Lil Pup
Posts: 4
Joined: Sun Mar 01, 2009 11:19 am
Location: Great Britain

Fuel octane rating

Post by Russell »

Finally got my darmah ssd running, spent a small fortune getting there.
One question, what is the best octane rating to run my darmah on, over
here in the u/k we have unleaded 95 ron and super unleaded 97 ron.
Should I be using an octane booster on an engine with a high compression
ratio of 9.5 to 1.
Russ
User avatar
BevHevSteve
SITE OWNER
SITE OWNER
Posts: 2230
Joined: Wed Mar 10, 2004 8:53 pm
Location: Lafayette, California
Contact:

Post by BevHevSteve »

Please tell us your cranking compression,....
Image
Steve Allen (925)798-BEVL[2385] Ride'm, Don't Hide'm
Ducati/Euro Spares -> https://Store.BevelHeaven.com
Facebook > http://facebook.com/Bevel.Heaven
Twitter > http://www.Twitter.com/BevelHeaven
Peter Mille
750 SS Greenframe - the holy grail
Posts: 500
Joined: Fri Aug 13, 2004 2:12 am
Location: The Netherlands, Europe.

Post by Peter Mille »

All Bevels were designed to run on leaded Super, 98 octane.
As this is no longer available ( although in the UK there are a few places that still sell leaded fuel, do a google search...!) use the fuel with the highest octane rating available, and mix it with a good lead replacement.
I know there are some outthere that don't agree, and run their bevels on plain unleaded fuel, I use Shell V-Power with Millers VSP in my '85 Mille.
Russell
Cucciolo - the Lil Pup
Posts: 4
Joined: Sun Mar 01, 2009 11:19 am
Location: Great Britain

Post by Russell »

I have checked the compression and the readings are 185psi on the front
cylinder and 186 psi on the rear cylinder. I have had new hardened valve
seats fittedand stainless steel valves. The cylinders have been rebored and new pistons fitted, the bore is now on 86.6mm with forged pistons.
Russ
Grover
Parallel Twin
Posts: 102
Joined: Wed Jun 21, 2006 3:50 am
Location: Grafton NSW Australia

Post by Grover »

Russ, here in Australia I run my Darmah on BP 98 Octane, where we go up in the mountains I need to put fuel in it to get home and all they have is one of those "no name" servo's that sell supposedly 95 Octane fuel, trust me, after 5klm's it runs like a dog and has no pulling power compared to running BP 98. When we travel around to classic rally's I always look for BP first, followed by Caltex then if I have to I will put Shell in it, but here the 98 Shell product varies way to much for my liking.
The older we get, the more toys we collect!!!
Post Reply

Return to “Squarecase BOSCH Ignition Engines > SD, SSD Darmah, late 900 SS & 900 GTS”