it’ll give me all the right reasons to go with lower CR pistons when I have to rebuild it!
Seriously, do you think just lower CR pistons will be enough, what about liners and the bottom end? If it’s literally just pistons then I might as well get that done too.
Put it this way if you damage the pistons, it will destroy the cylinder bores, then you will need Darton liners, while you have it open you would be mad not to upgrade the oil pump drive and shells, then as you have taken the rods out you may as well put in decent ones, and finally as the head is off upgrade the valve springs, oh well a full rebuild and �5k later you have a bullet proof build.
Or before you install the smaller pulley drop in the low comp drop in pistons 
Pistons and rods are not that expensive (although not sure rods are required for 350bhp?).A little over �1k should get you the pistons, rods and the upgraded oil pump gear set. Bit more on top should also mean the upgraded valve springs for over 9k rpm and balanced components .
I would like to know what the limit of the std components are. Do we really need to go to Darton Liners?
If you drop the piston lands due to running too much boost it will ruin the nikesil (sp?) coating, that will mean new liners, if you replace prior you won’t need them if you bores are still ok and not a bit oval, if they are out of spec you will need liners.
A lot of people suggest buying a new short block and dropping the pistons straight in.
Not sure what I’m going to do yet, if at all.
I wish I bought that engine on Seloc that suffered oil starvation 
. As I’ve said previously, a high mileage or midly damaged engine would be a good option as the worn parts on the bottom end will be replaced anyway, and the heads can be swapped straight over.
Really want to go down this route, but there is no way I’m forking out �4k for the audi g/box to cope with the power. Although I now know a company that will build an adapter plate and custom flywheel for the linkup, so I may look into the installation myself.
A Freind of mine had had oval liners after 68k and about 150 trackdays it was using oil and petrol at about the same rate 
He bought a new short engine from Toyota �1500 exchange lotus wanted something like �3.5k for the same thing
Me too, I was in 2 minds if I should buy the 2nd hand one as well and now wish I had. Also a few new engines were sold on here and I wish I’d bought one of those as well, bit silly not doing so
I’ve notice the Komotec 320s is claiming 316bhp and 202lb/ft
Interesting to see they seem to think over 300bhp is safe on standard internals.
I’m hoping (praying…) my 2bular 3" exhaust might give me a little bit more of a saftey margin if I do decide to go for the smaller pulley…
Sadly none of us have ever seen a back to back dyno with one of our cars (known HP not claimed) so we have no idea what the real world is for these, wonder what boost level they are using to achieve 320hp and what the wheel figure is? I bet they are basing their figures on high transmission losses!
…was thinking the same.
Its a shame what with our different sized exhaust systems that we never measured boost at the sincs dyno day last year - would be interesting to know the diferences.
I measured the boost pressure back to back with the 2 exhaust sizes, and I lost boost and HP with the bigger exhaust, they managed to map back the HP, in the end I gain a bit of mid range torque and lost out on high end HP, to be honest it was a wasted bit of R&D but interesting to find the right exhaust for 300hp was the smaller one, but only just
Doesn’t that mean that the larger exhaust was the better one?
If the bigger exhaust was creating less ‘boost’, then the smaller one is a restriction. The charger can only pump a given volume of air per rev, so if you loose boost with the larger exhaust, then you are using the air better for cylinder filling, rather than coming up against the restriction of the manifold on the way out of the head.
Treat the whole system from air filter to tailpipe as a whole, and you will only deliver as much power as the 1 smallest component can deliver. As an extreme example, move a 1 inch restrictor down the system, and you will create a choke point wherever it is, and temps/pressures will fluctuate accordingly.
Change pulley to reset to previous boost levels and you will gain power everywhere. At least in theory! And its all dependent on your charger speed. If you can’t go faster on the charger, then think of it as free power, with less stress on everything as a bonus.
[quote=JDS]Doesn’t that mean that the larger exhaust was the better one?
If the bigger exhaust was creating less ‘boost’, then the smaller one is a restriction. The charger can only pump a given volume of air per rev, so if you loose boost with the larger exhaust, then you are using the air better for cylinder filling, rather than coming up against the restriction of the manifold on the way out of the head.
Treat the whole system from air filter to tailpipe as a whole, and you will only deliver as much power as the 1 smallest component can deliver. As an extreme example, move a 1 inch restrictor down the system, and you will create a choke point wherever it is, and temps/pressures will fluctuate accordingly.
Change pulley to reset to previous boost levels and you will gain power everywhere. At least in theory! And its all dependent on your charger speed. If you can’t go faster on the charger, then think of it as free power, with less stress on everything as a bonus.[/quote]
That was what I was thinking - with the 3" exhaust I could go to the smaller pulley, but reach the same boost as the 2.5" exhaust cars but with more bhp.
Adrian - do you have a copy of your graph from Sincs last year with the 2.5" 2bular to compare?
Its all going to be about the speed you guys are now turning the charger at. There is a limit, and I suspect you are close, if not at it. Too much over the speed and all you do is generate more heat, for no great gains.
This is why i,m sticking with my standard pulley and A/A intercooler … CN,s did say they experimented with smaller pulleys and the main result was extra heat.
Ade in “hot air” shocker! At least it’ll complement his missus’s rollers 
There is little more to come from the mp62 charger, but is the main reason why I would like to swap the charger for the much more efficient tvs harrop charger.
you can spin the charger faster than we currently do and it is still within its performance envelope, the biggest issue is cylinder pressures and the destruction of the ring lands. The ones of us that have charge coolers, extra heat generated should not make a huge amount of difference.
As a rule of thumb 0.1" smaller gives about 1psi more boost, obviously this is not a perfect ascience so don’t relly on it, and the smallest pulley you can reasonably run is 2.6" or maybe even 2.5" if you don’t increase your rev range.
Makes sense Katana runs a 3.4" pulley which is about 6.5PSI of boost with ~250bhp. Ronin reckons 1PSI of boost is worth 10 horses so if your running a 2.5" pulley with a decent tune and cooling you’ll be around 90 horses up on the Katana at around 340bhp.
S.
As said above that works out reasonable well as well, a 2.9" pulley gives around 300hp so a 2.5" will give ~340hp but you would have to run a slightly lower compression pistons.