Thanks Mick and Simon no worries about steel work back to doing that myself again its been 2 decades but last 6 months got into the swing again. Doing nice alloy tig welds is an art, finally found someone who can actually do it properly!

Here`s a graph showing the diference between a stock A12, an A15 with weber and extractors and the Turbo A12. You can see that the turbo and non turbo A12 make about the same torque and HP until the boost kicks in.

I must just say, I've been following this thread, and I'm still amazed at the numbers this simple setup produces!

Crikey! 155hp from stock A12 internals ...

It is a bit to get your head around! The comparison graph realy makes it stand out.

Ive put a diferent cam in it, and replaced the round port head with a stock and unmodified H89 head. Ive used ARP head studs aswell. So not totally stock A12 internals, but close.

Secondhand bearings, standard cast pistons and rings, standard rods + bolts, standard crank, standard headgasket,no balancing or special prepwork on the engine. I had old pistons in the first engine aswell, before i had my ignition problem that damaged two of them. So i had to put some new cast pistons in it.

Im not an engine builder, but the things i think are critical are-

Good ring and valve seal, good head clamping, good intercooling, using a fuel to match the compression ratio/boost level and a good tune.

or something like that!

i'm still trying to get my head around making power so late... only 50% of power at 5000rpm, and about 25% at 4000rpm...

how do you find it at the track for drivability?

It`s fairly good. I change gears at about 7k and revs drop 1800rpm 3rd to 4th and drop 1200rpm from 4th to 5th.
It makes about 120FtLb from 5100 to 6800.

It was runing out to about 7300 in 5th at Philip Island (215KMH)

If i could get it to work about 750-1000rpm earlier, i wouldnt have to use second gear in the slowest corners. This might be an advantage because i wouldn`t have a gearchange that unsettles the car a touch on corner exit.
mmm Not sure.
Im still using 6 year old tires, with new tires and more seat time, my corner speed will be up. mightn`t be a prob then.

From a rally perspective, If the engine was going into a rally car it certainly wouldnt be much good as it is.

And i do agree that it can be better. That why its a development thread

hope everyone is remembering this is with e85 too... i guess you could play around with different turbos that might come on a little earlier but you might lose top end. hmmmm

Sequential turbo? THat's getting complicated.

I only just came accross this thread now.
The results really do come down the the engines management. If we compare apples with oranges for a moment, Compare this engine to the much talked a bout engine that topgear posted up a few years ago. he made great numbers for what might be described as a crude-amentry system. Where yours has cooler charge from the IC, variable spark timing from the ecu, and E85 into the mix as well. With all these factors (Plus the others not mentioned) it's no suprise to me that your engine is making the numbers it is. Where Topgear's engine was encountering limiting factors, yours isn't fazed.
Seeing your results get me re-insspried to built an A14 turbo for which I've been squirreling away parts. For the last ten years or so.
Which ECU are you running? (I must have missed that bit)

Does your engine produce much blowby?
I've found that forcing A series motors with standard-ish pistons (Even with out pinking the nuts off them) tends to get them fuming a bit.
Now that I've seen this thread I'll definately be following developments.