Octane boost thoughts

[DangerousDerek]

I would be interested on peoples thoughts as to why and maybe where I can improve my tune.

I was racing at York last weekend. The TVR was quite consistent despite the weather and was running terminal speeds of 114.5 mph.
On the Monday a friend offered me half a bottle of Royal Purple octane boost so I dumped it in my tank which had about 15 litres of Vpower in.
First run I ran 114.8, then 116.2

My engine is a 5.0 with a solid cam and fairly high CR of 11:1
Do we think its crying out for higher octane?
Maybe I could add a couple degrees advance but its set at 34 degrees already.

What do we think?

[neal1980]

I think we will be seeing another rebuild thread again lol

Leave it alone it's running great !!

Concentrate on the next engine but leave this in a sellable condition... Get too greedy with timing it's all over.

[DangerousDerek]

No worries I don't intend to stretch timing etc.
I did have to add 3 points to the top of the fuel map on Sunday to get the AFR down as it was a tad lean on WOT at the top end.

What I would like to do is get it on Surrey rolling road soon if I can. I think it's now producing good numbers.

What's it worth do we think? I got a lot of blood sweat and tears in this now.

[rev-erend]

Why not buy some 118 octane av gas. They sell it at the pod.

[DangerousDerek]

rev-erend said:

Why not buy some 118 octane av gas. They sell it at the pod.

I have a drum of VP racing fuel, I think I will try a mix next meeting.

[77racing]

Try this derek, just round the corner from your sister

http://www.vpracingfuels.com/

ps more bang = more heat beware. Sorry see you already there. Much better to have more oxygen as in VPfuel than an over the counter additive. Do you know if the octane booster adds more oxygen when mixed with pump fuel, if not, it is a no brainer. You would probably need a remap on racing fuel.

Edited by 77racing on Wednesday 4th May 13:04

[rev-erend]

I think the racind fuel has more knock resistance so you can run more cr
but it brings rebuilds and failures ever closer.

[77racing]

if racing was cheap, we would all be doing it. so my bank manager says anyway

[blitzracing]

I used to add the Millers octane boost to super unleaded on the little Fiat engines I used to tune when "blitz racing". Ive never managed to get knock detection to work on the RV8 when trying to advance the timing to its peak point, but Mark Adams did pass comment that its really hard to make the RV8 knock unless the mixture is too lean, and anyway by time you have knock you are well past peak torque, so ideally you want to put the high octane stuff in, and head for the rollers to optimise the timing and torque. The later P38 lucas GEMS system does have tuned knock sensors on the Rv8 block so it must be possible to detect, Ive just failed to detect it either by ear, or after market knock detectors using P38 sensors.

[griffdude]

If you're going to change the octane, make sure you re-map as someone who shall remain nameless ran his RV8 on avgas & burnt the valves out.....

[Pupp]

Toluene and Xylene have both been used as octane raising additives; the latter was quite common in the bike racing world in the 1990s on hyper-tuned 600s etc. They blew up pretty regularly

[Alexdaredevils]

If you want to go down that route you I would get knock sensors fitted to take advantage of more agressive timing.

[nawarne]

Pupp said:

Toluene and Xylene have both been used as octane raising additives; the latter was quite common in the bike racing world in the 1990s on hyper-tuned 600s etc. They blew up pretty regularly

....As well as being extremely carcinogenic

[Pupp]

nawarne said:

....As well as being extremely carcinogenic

But smelled good...

[77racing]

Pupp said:

Toluene. They blew up pretty regularly

I have a set of heads on my race car that I had to have welded up as Toluene had been at them, It burns very hot indeed but good for an extra 20BHP apparently.