Alternate history: M96 Cup engine
Discussion
Dammit said:
The chaps from Project Binky recommended the engineering place that machine these- for which I’m very grateful as their work is excellent.
We now have a set for each of the three engines we have in build.
Here with the stock version:
And here with the new, larger valves, titanium retainers, and a 3D print of the ITB’s we’ve designed to check dimensions and fit.
Fixed formatting.We now have a set for each of the three engines we have in build.
Here with the stock version:
And here with the new, larger valves, titanium retainers, and a 3D print of the ITB’s we’ve designed to check dimensions and fit.
What throttle body are you planning on using?
I admit, they're largely there because of the small boy inside me who wants to hear an over-square, cammed, tuned flat six howling through throttle bodies at 8,000 rpm. Of course, there are performance reasons, but the noise should be incredible - and bear in mind my car has no roof to get in the way of appreciating it.
Yes, that's it - I think it's more commonly known as the lifter carrier.
The stock version is a cast part that can fail (hydraulic fracture is the most common cause of failure IIRC) which is, as you might suspect, Bad News for the engine:
Our dual oil scavenge pumps should reduce the chance of this significantly as they prevent the type of oil build up that may lead to the carrier fracturing, but there are other reasons to move to the billet ones in the picture.
We looked at billet cams, we looked at sourcing cam blanks, and we came back to re-grinding original cams as the best blend of cost/performance.
This means that the base circle is going to be smaller, so the lifters will ride higher in the bore, so the bore itself needs to be adjusted to prevent the lifter tipping, and the oiling needs to be modified slightly to accommodate this.
We're also spinning the engine a lot faster than Porsche did for the X51 series, so valve train stability and strength is important.
We can't modify the stock items to meet all these goals, so CNC'ing new ones became the logical choice.
The stock version is a cast part that can fail (hydraulic fracture is the most common cause of failure IIRC) which is, as you might suspect, Bad News for the engine:
Our dual oil scavenge pumps should reduce the chance of this significantly as they prevent the type of oil build up that may lead to the carrier fracturing, but there are other reasons to move to the billet ones in the picture.
We looked at billet cams, we looked at sourcing cam blanks, and we came back to re-grinding original cams as the best blend of cost/performance.
This means that the base circle is going to be smaller, so the lifters will ride higher in the bore, so the bore itself needs to be adjusted to prevent the lifter tipping, and the oiling needs to be modified slightly to accommodate this.
We're also spinning the engine a lot faster than Porsche did for the X51 series, so valve train stability and strength is important.
We can't modify the stock items to meet all these goals, so CNC'ing new ones became the logical choice.
Dammit - I'm loving this thread. Have been following for some time!
I've been looking at how I can make my C4S the best it can be, and am getting there. Brakes, set-up, geo, suspension is pretty much all there now. The only thing I've got left is the engine. I was looking at the 3.9 Hartech but I can't help feeling I'd like a few more RPM. I know that torque is king etc, and why would you want more RPM, but for me its also about the experience. I do wring my C4S out to the red-line regularly and love it.
How is progress since your last post? Is the engine together yet?
I'll be following this closely as you near completion - and certainly giving Baz a call if/when you are hopefully successful!
Good luck!
I've been looking at how I can make my C4S the best it can be, and am getting there. Brakes, set-up, geo, suspension is pretty much all there now. The only thing I've got left is the engine. I was looking at the 3.9 Hartech but I can't help feeling I'd like a few more RPM. I know that torque is king etc, and why would you want more RPM, but for me its also about the experience. I do wring my C4S out to the red-line regularly and love it.
How is progress since your last post? Is the engine together yet?
I'll be following this closely as you near completion - and certainly giving Baz a call if/when you are hopefully successful!
Good luck!
Very impressive stuff!
Wrt suppliers of custom camshafts I'd like to mention the supplier to Porsche of the original M96 camshafts (and probably many other Porsche engines prior and after):
https://www.schleicher-fahrzeugteile.de/en/product...
They're based in Munich and have supplied BMW Motorsport too.
They are equally well regarded as Schrick are and offer prototype manufacturing too.
Wrt suppliers of custom camshafts I'd like to mention the supplier to Porsche of the original M96 camshafts (and probably many other Porsche engines prior and after):
https://www.schleicher-fahrzeugteile.de/en/product...
They're based in Munich and have supplied BMW Motorsport too.
They are equally well regarded as Schrick are and offer prototype manufacturing too.
Edited by hardtailer on Saturday 22 January 10:58
Have you seen the posts on Facebook (yuk) by Jake Raby about cam timing retardation across the cam itself? He seems to suggest the individual cam lobes are retarded across the cam itself for some reason. I suspect it might be manufacturing or measurement issues but he seems convinced it is deliberate.
I personally find him pretty irritating but that was quite interesting to me. Maybe this is a common thing on production engines for one reason or another, some cylinders getting less airflow than others for example.
I personally find him pretty irritating but that was quite interesting to me. Maybe this is a common thing on production engines for one reason or another, some cylinders getting less airflow than others for example.
shalmaneser said:
Have you seen the posts on Facebook (yuk) by Jake Raby about cam timing retardation across the cam itself? He seems to suggest the individual cam lobes are retarded across the cam itself for some reason. I suspect it might be manufacturing or measurement issues but he seems convinced it is deliberate.
I personally find him pretty irritating but that was quite interesting to me. Maybe this is a common thing on production engines for one reason or another, some cylinders getting less airflow than others for example.
Haven't see the FB post, but a look at the exhaust manifold design may explain why there's a difference in the cam timing from one cylinder to another.I personally find him pretty irritating but that was quite interesting to me. Maybe this is a common thing on production engines for one reason or another, some cylinders getting less airflow than others for example.
For all the scorn heaped upon the 3.4 engine, it was clearly very cleverly optimised by the engine development engineers at Stuttgart. All the more so as I'm guessing there were many questions asked which were responded to with "Nope, we don't have the budget".
Mr Raby "pretty irritating", ? I'd say that was being very diplomatic ...
But love him or loath him, there's no doubt he knows these engines inside out, and is one the few individuals who's worked out how to extract big horsepower from them, but more importantly, to do so reliably.Slippydiff said:
shalmaneser said:
Have you seen the posts on Facebook (yuk) by Jake Raby about cam timing retardation across the cam itself? He seems to suggest the individual cam lobes are retarded across the cam itself for some reason. I suspect it might be manufacturing or measurement issues but he seems convinced it is deliberate.
I personally find him pretty irritating but that was quite interesting to me. Maybe this is a common thing on production engines for one reason or another, some cylinders getting less airflow than others for example.
Haven't see the FB post, but a look at the exhaust manifold design may explain why there's a difference in the cam timing from one cylinder to another.I personally find him pretty irritating but that was quite interesting to me. Maybe this is a common thing on production engines for one reason or another, some cylinders getting less airflow than others for example.
For all the scorn heaped upon the 3.4 engine, it was clearly very cleverly optimised by the engine development engineers at Stuttgart. All the more so as I'm guessing there were many questions asked which were responded to with "Nope, we don't have the budget".
Mr Raby "pretty irritating", ? I'd say that was being very diplomatic ...
But love him or loath him, there's no doubt he knows these engines inside out, and is one the few individuals who's worked out how to extract big horsepower from them, but more importantly, to do so reliably.Exhaust manifolds - we have an update.
Our engine designer stated that (amongst other dimensions) 27" was the ideal length for the primaries. Anyone reading that sentence who has ever been underneath a 996 will probably be wearing a slightly bemused expression - but luckily when you are designing the entire exhaust you have a degree of flexibility over where things go.
Yes, we, erm, moved the silencers and used that space to fit in 27" truly equal length primaries and a nice merge collector, before turning the exhaust back toward the rear of the car.
Out of the car and from the side this looks like this:
Looking down through an imaginary decklid you can see the overall packaging - this system will have 200 cell cats (removable) in the straight sections that come down from the merge collector turn to the start of the X pipe:
And from under the car:
The silencers are repackable and the system is designed for 105dB maximum - although with the ITB's I suspect that track day noise limits are going to be interesting.
As this is Pistonheads in 2023 I understand that I can't post without talking about values, so: in order to make building a car in the UK easier I moved to Singapore at the start of the year. Cars here are *expensive* - a 996 in good condition is a hundred thousand pounds, minimum.
I went to see a BMW 2002 from 1976 which (as a classic) was actually fairly affordable - chap who owns it owns around 70 classic cars, and is moving some out in order to make space for some new 911's, which he is intending on importing from the UK due to the price difference (UK cars are, even with import duties, stupidly cheap in comparison).
Our engine designer stated that (amongst other dimensions) 27" was the ideal length for the primaries. Anyone reading that sentence who has ever been underneath a 996 will probably be wearing a slightly bemused expression - but luckily when you are designing the entire exhaust you have a degree of flexibility over where things go.
Yes, we, erm, moved the silencers and used that space to fit in 27" truly equal length primaries and a nice merge collector, before turning the exhaust back toward the rear of the car.
Out of the car and from the side this looks like this:
Looking down through an imaginary decklid you can see the overall packaging - this system will have 200 cell cats (removable) in the straight sections that come down from the merge collector turn to the start of the X pipe:
And from under the car:
The silencers are repackable and the system is designed for 105dB maximum - although with the ITB's I suspect that track day noise limits are going to be interesting.
As this is Pistonheads in 2023 I understand that I can't post without talking about values, so: in order to make building a car in the UK easier I moved to Singapore at the start of the year. Cars here are *expensive* - a 996 in good condition is a hundred thousand pounds, minimum.
I went to see a BMW 2002 from 1976 which (as a classic) was actually fairly affordable - chap who owns it owns around 70 classic cars, and is moving some out in order to make space for some new 911's, which he is intending on importing from the UK due to the price difference (UK cars are, even with import duties, stupidly cheap in comparison).
Edited by Dammit on Friday 8th December 08:51
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