comp, pistons vs boost
Turbo Mini Forums

G'day lads,

So my 7 port is fun but I'd like a tad more and unfortunately the way the valves and springs are I can't run more lift.

So my question is .... can I run boost { turbo } on hypereutectic pistons running 9.75:1 ?

1977 Leyland mini Sunshine -- moleseted -- Named " Ray" becoming a 7 port efi slowly
1971 Nota Fang 145 bhp 5 port fun @ 450 kg
1969 Austin 1800 ute, 1800S running gear, tip rat and hardware store runner

What are the pistons? Manufacturer??

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

If your pistons have survived Nat Asp high RPM, a little boost (and at that CR you are talking a small amount of boost) won’t hurt the pistons. Are you fuel injected and mapped ign? If so, you may be able to do a surprising amount of boost quite easily.

providing the pistons are decent quality I'd expect you should be able to stick in 7 psi happily with a good setup.

Joe I presume by good setup you mean fueling, timing and intake temps?

So having a way to control the timing as the boost comes in and ensuring you have an intercooler a no lean spots will help.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

yep, exactly that.

Reason i ask is I had some Hypatec Australian pistons, I had 2 sets and both the ring lands shit them selves.

I was running 10 with a moderate map and they just couldnt handle that much boost. You might be ok running 4 or 5 and this was a few years ago so may be different.

Edited by MikeRace on 19th Jul, 2018.

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

currently running 73.5mm hypertech pistons with { I think} 8cc dish. mapped ign and fuel.
As for intake temp I've not looked while running { laptop on lap while driving, and no I don't like passengers as they tend to squeal a bit} but being a Clubbie and down here in Aust they could be anywhere ....

1977 Leyland mini Sunshine -- moleseted -- Named " Ray" becoming a 7 port efi slowly
1971 Nota Fang 145 bhp 5 port fun @ 450 kg
1969 Austin 1800 ute, 1800S running gear, tip rat and hardware store runner

Just make sure you have a larger than normal ring gap......

There are two types of Hypatech as sold by MiniSport Australia (there may be others on the market in other countries but I'm only familiar with the ones stocked in Adelaide).

There is the standard size range (normal bore, +20, +40 etc) and then the metric ones for significant overbores.

The standard range has a horrible large pair of slots behind the oil control ring so are probably very weak.
The metric ones are a completely different design and have a series of holes behind the oil ring and are very strong IMO.

I'm using the 73mm ones (so only 1360cc) and I dished them out to 14cc from their standard 6cc and they have been fine at 1Bar

I bought another set whilst I was in Adelaide last year to build a second engine (yet another project) so I have confidence in them.

EDIT - I should probably add I too run injection/ignition and with an ECU/code specifically for the siamese ports and with widebands on inner/outer/after turbo so I know I'm not putting them at risk but I also run a VERY conservative 8.3:1 (could go a lot higher with the ECU I'm using).

Edited by Rod S on 20th Jul, 2018.

Schrödinger's cat - so which one am I ???