First of I don't condone Bass Ale: I am a 6X Bitter drinker myself but by
the by. Mind you for the ulimate in hagover causing beers, Burtons from
Burton on Trent will give you a hangover that will keep you in bed for at
least 22 hrs.
10.5:1 compression is a lot for modern petrols. To run with that
compression on 90's even 00's you will need to seriouls retard your
ignition. Going for a more reasonable 9:1 - 9.5:1 compression will meen you
will not need to retart the ignition as much, if atall if you install
electronic ignition.
Modern car's have a cylinder head designed to give high compression with low
octain petrol, and still reduce pinking. The Triumph cylinder head's just
are not up to the job, and so high octaine petrol is needed.
Here are some specs (UK octaine ratings, US take off a few).
Octaine UK US ???
2* - Regular Unleaded 92 87??
Super Unleaded 95 92??
4* - Leaded 98
5* - Leaded 101 -- No longer available
The Vittess - GT6 TR6 were originaly speced to use 5* petrol. In the UK
they have been running on 4* for years slightly retarded ignition, or opto
electronic ignition. Now they face going to unleaded in 2000 and they are
going to have real problems. UK Spitfires are 9:1 and drink 4*.
There are power - compression curves for each octain fule, the region of 9
to 11:1 compression is relativly flat. Above 11:1 and it start's a steep
slope down, same on the 9 side. The power difference between 9:1 and 10.5:1
is very little, the lower the octaine petrol, the more the power curve get's
pushed to the lower compressions.
Raising the compression will put you into drinking super unleaded, retarding
the ignition and installing electronic ignition to get the pinking under
controll.
2 / 2.5 * 10.5 = 8.4
Your currently getting 8.4:1 compression assuming both engins use flat top
pistons. You could push this to 9.5:1 and get a bit more power out. Thing
is at a guess insted of 104 BHP with 10:1 you'll be getting 102BHP with
9.5:1 or 94BHP with 8.5:1. Replaceing the mechanical fan with an
thermostated electric one will give you 10BHP more.
A friend tested his 2.5PI fan on a claibrated electric motor at work. At
rpm the fans spins at for max engine power the fan sunk 15BHP!
Somthing else to think of!
James
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