Accralite piston info
Turbo Mini Forums

Have been looking into the possibility of building a 1430 bottom end for my 7 port recently, the chambers are only 24cc though whic would mean 20cc pistons,

On Accralites website there is info on all the avonbar pistons (thought that might be of intrest to you all) they quote the crown thickness as 5.5mm, In tuning forced induction by A Graham Bell it's stated that the crown thickness can go down to 6% of the diameter, so using this rule 1 mm could be machined from the accralites giving approx 20cc and maybe a bit more if the edge of the bowl is taken squarer.

What are your views on this?

the edge of the bowls are already quite square

Do you really stand to gain from the extra 50 cc?

You're using forced induction, so you could probably get the same power increase equivalent of the extra 50cc by increasing the boost a notch more.

Ultimately, a 1430 is a bored-out 1275 with some life machined out of the crank. Do you really want this on such a high-power build?

Personally I'm sticking to 1330cc for my 7-port turbo, after all, 160 bhp is already quite a handful in a Mini... no point in going for a lot more power unless you're sure it can be transferred to the tarmac and not get wasted in wheelspin....

Sorry if I'm being a bit of a spoilsport...

I donated, but somehow didn't get the label! :(

i find the 6 percent of the diameter rule a bit iffy ! it sees to me there are so many different forces on the piston ,and how it reacts to those forces depends on material heat conductance tolerance rpm efficiency ,octane etc etc , i feel its best to take it engine by engine ,and by what the manufacturer of the piston says rather than a blanket rule .
regards
robert

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

mmmmmmm,

If you look at the accralite's compared to JE's the JE's have a much squarer edge, i'd guestimate the radius on the edge of the accralites is around 10mm or more and probably about half that on the JE's, if you machined the Accralites to a similar shape to the JE's you could probably "find" 2 or more CC's

The idea was to get an even spread of torque and a quick car without having to run loads of boost, the assumtion being 10 psi and 160 bananas and boost from 2k will be quicker than 20 psi and 220 bananas and the car coming on boost heavily at 3.5k (Bearing in mind this will be used on the road)

I'm more worried about the 73.5mm bore than the offset ground crank, from what I've heard you would need to be putting some serious pressure into the combustion chamber to get any where near the stresses caused by RPM.

the main thing that makes it attractive is the fresh 73.5mm block sitting in tha garage doing sweet FA.

BUT your right i should just go for a trusty 1293, there's enough issues to sort already without funny rods and piston's.

I'll use the money saved on the box instead.

The 6 percent rule does seem iffy, after drawing out a crown with a 6% thickness i wouldn't go there, even the 5.5mm of the accralites looks worrying let alone removing 20%!

It's all Benross's fault, he made a comment about going 1380+...