Alternate history: M96 Cup engine
Discussion
The reason to have gone with Schrick would have been if we had to use a stock base-circle, in which case we could have then optimised for one of the grinds that they offer - which are off the shelf. I did speak with them directly about whether they would supply us with blanks - sadly the answer was no. We'd have gone with Schrick blanks if they'd been available.
Given that, and the work we'd done with the other elements of the head and valve-train it was significantly better to use grinds created with specific reference to the weight of valve/spring/retainer, point of valve-train separation, fuel cut, desired performance characteristics and of course flow performance through the head (and many other elements that no doubt Mike will point out to me as being even more important, but that are beyond me!)
Given that, and the work we'd done with the other elements of the head and valve-train it was significantly better to use grinds created with specific reference to the weight of valve/spring/retainer, point of valve-train separation, fuel cut, desired performance characteristics and of course flow performance through the head (and many other elements that no doubt Mike will point out to me as being even more important, but that are beyond me!)
Slippydiff said:
Dammit said:
Interestingly this has knock on effects in other areas - the Porsche exhaust cams are (relatively speaking) rather inoffensive little things, so choice of exhaust manifold design doesn't really make a huge difference. Moving to rather spikier cams means that we now need to optimise the exhaust for the cam design, so equal length primaries become important, although we're constrained by the packaging when it comes to primary length (there being a finite amount of room between the underside of the engine and the road), still we should be able to get a decent amount of tube under there.
Good to know there are other lunatics hell bent on cramming as much N/A horsepower in the most unorthodox manner possible, under the engine cover of a narrowbody 996 Neil 
If these fit under my steed :
I'm sure you'll be able to get something as, or more impressive, under yours and Martins ...
Very interesting read and good luck!
Yes and no, which isn't that helpful of an answer I am aware.
The Mezger does mount lower - if you look at a naked C4 shell and a GT3 shell then the only panel differences are in the rear of the engine bay where the engine mounts are lower down, and to the firewall behind the rear seats to accommodate the oil tank, although this latter change is apparently not strictly needed. I'm not sure whether the mounting points being lower equates to the engine being lower, though.
The Mezger engine also has an intermediate shaft which drives the cams via chains, and the depth of the sump in the M96 directly under the crank is very shallow - most of the space inside it is too either side, see this excellent video for more detail:
https://www.youtube.com/watch?v=4DOLuqLFOUk
The Mezger does mount lower - if you look at a naked C4 shell and a GT3 shell then the only panel differences are in the rear of the engine bay where the engine mounts are lower down, and to the firewall behind the rear seats to accommodate the oil tank, although this latter change is apparently not strictly needed. I'm not sure whether the mounting points being lower equates to the engine being lower, though.
The Mezger engine also has an intermediate shaft which drives the cams via chains, and the depth of the sump in the M96 directly under the crank is very shallow - most of the space inside it is too either side, see this excellent video for more detail:
https://www.youtube.com/watch?v=4DOLuqLFOUk
We are looking at piston design - complex things, pistons. Ours need to hit a very precise compression ratio target and to be as light as we can make them (amongst other design goals), and only once we've resolved these issues can we finalise rod geometry and get those ordered.
Hopefully once the design part is done we can get the parts made fairly quickly, but I think the goal of getting an engine in a car in 2021 is probably now unlikely, bit we may still be able to get an engine on the dyno before year end.
Hopefully once the design part is done we can get the parts made fairly quickly, but I think the goal of getting an engine in a car in 2021 is probably now unlikely, bit we may still be able to get an engine on the dyno before year end.
Piston design finalised and they're in production, new ITB design finalised and awaiting machining, and a prototype dual-stage scavenge pump is installed in my engine and has had a short test run. I'll be putting as many miles on the pump as I can before the end of the year, when we'll strip it down again to check that everything worked as expected. It was installed by Precision Porsche using the standard Porsche workshop manual for the X51 dual-stage pump, and used the OEM hardline.
The pistons should be arriving in the next few days and we're ordering the rods now that we have the precise dimensions.
Next stage is a dry-build of an engine to measure basically everything, then if everything is nominal and we don't need to adjust anything we put it together properly and map it on the dyno, make any adjustments that are required and then put the engine into a car and map it again.
Next stage is a dry-build of an engine to measure basically everything, then if everything is nominal and we don't need to adjust anything we put it together properly and map it on the dyno, make any adjustments that are required and then put the engine into a car and map it again.
The dry build confirmed that everything was correct, so the engine was stripped back down again.
We're waiting on some parts now - the billet tappet chest pictured earlier in the thread is in a stock 3.4 at the moment getting miles on it, as it was designed for the stock camshafts.
We are putting a fairly significant grind on the camshafts to get the profiles that we need so in turn the base circle is reduced, which means that the tappet chest design has to be revised in order that oiling and so forth is correct.
The revisions should be complete shortly, then we need to slot into the CNC places schedule, then that is ticked off.
In terms of the other elements that we are waiting for the ITB's just need to be CNC'd and assembled- that's a fairly self contained process as the chap we are working with can do all that in-house. That leaves the equal length tubular manifolds and I'm uncertain where we are with those - we have found a chap whose work I've seen on a heavily customised F40 and is of excellent quality, but I don't know his timescales at the moment.
However, with all that said, I believe that 2021 is the year that we get an engine on the Dyno, and all being well - in the car.
We're waiting on some parts now - the billet tappet chest pictured earlier in the thread is in a stock 3.4 at the moment getting miles on it, as it was designed for the stock camshafts.
We are putting a fairly significant grind on the camshafts to get the profiles that we need so in turn the base circle is reduced, which means that the tappet chest design has to be revised in order that oiling and so forth is correct.
The revisions should be complete shortly, then we need to slot into the CNC places schedule, then that is ticked off.
In terms of the other elements that we are waiting for the ITB's just need to be CNC'd and assembled- that's a fairly self contained process as the chap we are working with can do all that in-house. That leaves the equal length tubular manifolds and I'm uncertain where we are with those - we have found a chap whose work I've seen on a heavily customised F40 and is of excellent quality, but I don't know his timescales at the moment.
However, with all that said, I believe that 2021 is the year that we get an engine on the Dyno, and all being well - in the car.
shalmaneser said:
What's the plan with the itbs? I'd love to fit those to my boggo m96 3.4 in time, if only for the noise!
We initially looked at re-purposing some ITB's from an M3 with an adapter plate, but whilst it looked good (and would have sounded great I'm sure) the flow-bench showed that the adapter plate was killing flow. Given the not insignificant work that has gone into raising flow (both in terms of volume and velocity) of the heads themselves it would be lunacy to then write-off these gains with ITB's that were not optimised.We started discussions with a UK company that makes custom ITB's who is based close to Martin and went through a discussion that led to a CAD model, once that was signed off we went for a rough 3D print, then a higher resolution one which went to the flow-bench, and once that was signed off we ok'd the final design.
I would warn - these are designed for our application, and whilst they can of course be bolted to a stock 3.4 (or indeed 3.6) the question of whether they'd give gains on a stock engine is one that we have not looked at answering. They'd sound excellent, of course.
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