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The intake camshaft can be seen in the picture of post # 828. The chain gear on the cam is adjustable. The cam profiles actually come from Kawasaki drag racing motorcycle engine. Hardwelded cams made by WEB. The Stroker 7L engine exists but is half-finished. What I miss are pistons, aluminum flywheel, clutch. What I have to fabricate are headers and exhaust system, runners and trumpets for the ITBs, porting of the heads with 42/36 mm valves and many more minor things. Right now I am working on my BMW 635CSI including the building of a high performance engine. The job will probably go on all coming winter. I have a lot to fix on the house, wrong it is actually three houses we have including the workshop and a large garage.
One more thing, I have to modify the mill and make a fixture to be able to finish the machining of the engine block.
Åke
sorry , of topic, but that is Havik Racing Solutions , was a shop from Rob van Kol in Belgium building mostly race 944 cups.. ... that yellow 928 is his brother's car , seen it many times in his shop.
That's the shop who was building me a "race" engine years ago... after having already "20k €" payed in the project , he went broke and disappeared with "my" engine ! Never heard of him again...
Sad story for me..... as engine was almost finished..... a sleeved 6l 16V with ITB's as in the pic. 944 heads , custom pistons , dry sump..etc...he "was" a specialist in 928 engines... sadly it had to end that corrupt way .
Barry, I remember you mentioned it before. Sorry you were cheated this way but I guess there is not much legal you can do to be compensated. Sometimes in life we encounter bad things, you are not alone in this.
Åke
Have you seen John Gill’s ITB results? Picked up 100+ hp by dropping the S4 intake:
An otherwise sensibly tuned 928 GT 5.0 engine (11.5 compression, S3 pistons, ’87 S4 conrods, E85, Colt stage 2 cams with a too wide LSA of 114, headers, race exhaust) picked up 100+ hp in the 6000-7000 rpm range by swapping the S4 intake to 48mm AT Power individual throttle bodies with trumpets. Only intake manifold and air pickup changed. And the gap will widen if he spins it to 7500 rpm.
This is what John Gill recently said about his new engine: Greg knows this I haven’t posted my results yet on the new engine , its makes much more power over the previous unit . Wednesday had a chance to have a run at the track day , I ended up being the entertainment , as I managed to stick the car into the fence , damage sustained to the frontal area , mostly cosmetic but ended the day .On a positive note the car had ridiculous acceleration so different from previous , will be very easy to get into some serious speed trouble on the longer tracks with higher speed potential.
Åke
[QUOTE=Strosek Ultra;16851444]The intake camshaft can be seen in the picture of post # 828. The chain gear on the cam is adjustable. The cam profiles actually come from Kawasaki drag racing motorcycle engine. Hardwelded cams made by WEB. The Stroker 7L engine exists but is half-finished. What I miss are pistons, aluminum flywheel, clutch. What I have to fabricate are headers and exhaust system, runners and trumpets for the ITBs, porting of the heads with 42/36 mm valves and many more minor things. Right now I am working on my BMW 635CSI including the building of a high performance engine. The job will probably go on all coming winter. I have a lot to fix on the house, wrong it is actually three houses we have including the workshop and a large garage.
One more thing, I have to modify the mill and make a fixture to be able to finish the machining of the engine block.
Åke (Quote)
Some time ago I modified the milling machine with a 200 mm (8 inches) riser block (blue in picture). Now I am able to machine larger items like a V8 cylinder block. It made the mill as heigh I had to make a footstool to stand on.
Åke
Last edited by Strosek Ultra; 06-26-2021 at 12:04 PM.
Good work by John.
Performance gain is no surprisel.
After all, that's been normal' intake runner design and has been for decades.
Eg - 60's CB4540 Honda intake tract?
Nothing wrong with the 928 engine except for Porsche's dopey obsession with an artistic intake manifold.
UpFixen.
Last edited by UpFixenDerPorsche; 06-26-2021 at 01:54 PM.
Good work by John.
Performance gain is no surprisel.
After all, that's been normal' intake runner design and has been for decades.
Eg - 60's CB4540 Honda intake tract?
Nothing wrong with the 928 engine except for Porsche's dopey obsession with an artistic intake manifold.
UpFixen.
Those old Honda CB450s. Remember that the CB450 came with very poorly designed intake ports. The flow and performance gain from porting was very good. We went from 38 / 33mm to 40 / 34mm valves. The torsion bars had to be replaced with ordinary valve springs in order to be able to increase the valve lift.
Åke
Long before an engine is built, here, we know the potential of the engine (within 5-10%)...simply by measuring the air flow on a flow bench.
With naturally aspirated engines, maximum horsepower potential is a simple calculation, directly from flow.
Horsepower output is completely dependent upon airflow potential, in a naturally aspirated engine!
A dyno simply tells one the volumetric efficiency at various rpms.....and how well one did designing the engine.
The 928 S4/GT/GTS heads flow enough air to support ~475hp. Right out of the box.
It's no secret that the intake system is the major restriction in these engines, with exhaust system restrictions coming into play around the 375hp range.
Beyond this power level, other things must be changed, to increase the flow through the heads/increase volumetric efficiency.
For the last six continuous weeks, I've been working exclusively on solving the horsepower limits on a "bigger" S2 Euro S engine. Depending on which heads are used (closed chamber CIS heads or open chamber '84-'86 heads), the airflow will potentially make 350-375hp.
There's simply no way to get more air through the stock heads, without "pushing the air" somehow. Note that this is almost independent of the intake system (which stock, reduces this potential a bit)....the heads become the limit, once the intake is modified. And absolutely nothing one does to the exhaust will help, beyond a certain point. The airflow through the head/intake is the limit in these engines.
A quick calculation of simply making the engine bigger (which is fairly linear) will result in the engine making ~375hp. (Of course, the stock intake and exhaust will not support this and will need to be modified.)
To get beyond this power level, things have to change!
Of interest, a quick/dirty calculation of the '84-'86 S2 Euro S volumetric efficiency is pretty amazing!
At 5900rpms, making 310 horsepower is accomplished through a volumetric efficiency of just over 100%!
Crazy numbers for a production engine!
While Porsche did their work really well at this rpm range, the volumetric efficiency below 4,000 rpms was "sacrificed" to get the efficiency at higher rpms.....the stock Euro S engines are pretty "soft" in this rpm range. This is important. Regardless of what one does to the intake system....ITB's, Weber carbs on straight manifolds, etc., the volumetric efficiency isn't going to improve, very much, beyond 100%.
110% is possible, but it is going to be as tough road, with a perfect exhaust system and more intake system changes., and perfect tuning.
Six weeks of designing, fabricating, porting, welding, etc. has resulted in me being able to make enough airflow (while still keeping the velocity high) to produce 450hp...and be able to support that airflow with fuel, exhaust, intake. All without spinning the engine much higher than stock.
A fantastic improvement...but not simple., by any means!
Heads modified, intake modified, some really intense exhaust system changes.....pretty far out in the theory and function of exhaust. (We're doing stuff that I've never seen or heard anyone attempting or paying any attention to.)
But a 450hp 2 valve engine, with increased low end torque from increased displacement, more rpm potential from lighter pieces and longer rods, seems like it will be close to the "Holy Grail" of early 928 engines.
Why this sudden interest in the 2-valve heads when the 4-valve heads are superior? The 2-valve heads with 48mm intake valves I once made for myself flow at max valve lift (13,2mm - hotter cams) 253 CFM which would support 500+ HP. Someone in Australia made a couple of 2-valve heads with 52mm intake valves which according to the common calculations would support well over 550HP.
The best test intake port with 2x42mm valves I have made so far do flow enough air for well over 100HP per cylinder.
For high power output, you have to count on lower torque at lower rpm that can be compensated with larger stroke volume. Hotter camshafts are necessary, which naturally increases the engine speed. The factory S4 intake manifold is designed for best possible torque at fairly low rpm and is a bottleneck for high power output at high rpm. https://rennlist.com/forums/928-foru...ispreloading=1
Åke
Why this sudden interest in the 2-valve heads when the 4-valve heads are superior? The 2-valve heads with 48mm intake valves I once made for myself flow at max valve lift (13,2mm - hotter cams) 253 CFM which would support 500+ HP. Someone in Australia made a couple of 2-valve heads with 52mm intake valves which according to the common calculations would support well over 550HP.
The best test intake port with 2x42mm valves I have made so far do flow enough air for well over 100HP per cylinder.
For high power output, you have to count on lower torque at lower rpm that can be compensated with larger stroke volume. Hotter camshafts are necessary, which naturally increases the engine speed. The factory S4 intake manifold is designed for best possible torque at fairly low rpm and is a bottleneck for high power output at high rpm. https://rennlist.com/forums/928-foru...ispreloading=1
Åke
Quite simply, I've got quite a bit of demand for high output 2 valve engines for the early cars. I've got several clients anxious for these engines, making the investment in time and effort simply an investment in our shop's future.
Worth noting, I never go hunting for the maximum amount of airflow I can possibly make. Making huge intake ports with higher than necessary airflow isn't my goal.
I carefully match my airflow requirements to my needs, in order to retain velocity at the lower rpm and mid rpm ranges. This increases drivability by making additional torque and horsepower in the entire rpm range. (5.8 liters doesn't hurt, BTW.)
As I mentioned above, Euro S2 engines are very "soggy" below 4,000 rpms, due to terrible volumetric efficiency in the lower rpm ranges.
While tolerable, due to the lighter weight of the 2 valve cars, certainly not optimal.
Once volumetric efficiency reaches ~110%, increased airflow does absolutely nothing, unless the rpm limits are greatly increased. (At 7,000 or even 7500 rpms, there is a limit to the amount of airflow required. More airflow is only useful if the rpm limits are greatly increased.)
Making 500 hp at 9,000 rpms, with huge camshafts and poor intake velocity (which results in an engine that is terrible below 5,000 rpms) is completely useless to me.
None of my clients have any desire for this engine or the desire to brag about how much horsepower they have at 9000 rpms. They desire smooth drivability through the entire rpm range, with great performance, very efficient fuel use, while easily passing any emission test, if required.
Higher torque through the entire rpm range, with excellent usable horsepower and fantastic driveabilty at reasonable rpms is my goal. This is what I do, and what I've always done.
However, this engine is only a tiny part of our equation:
Combine an engine, like this, with all the ancillary pieces I make...butter smooth clutches, greatly improved suspension components, extremely durable torque tubes, greatly improved limited slips, extremely durable transmissions, improved braking with extremely "high end" ABS, greatly increased A/C performance (I can go on and on, but you get the idea) and we can create a really fantastic "modern" 45 year old car!
08-18-2020, 12:24 PM
