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Truthfully, I've been going down in engine size, in some of the engines I build. There's a limit to how much mid range torque one really needs. I've been "moving" the power range higher and reving the engines higher...trading mid range torque to gain more high rpm horsepower.
Once you get your new intake(s) going and assuming they're sized properly, you won't be forced to make those compromises any longer.
Holding the bob-weights constant, usually the better and more expensive crankshafts are heavier than the cheaper and worse ones. That’s because how the balancing physics work, a heavier counterweight closer to the crankshaft centerline is usually better in terms of acceleration.
Piston-guided rod setup makes sense for a high-rpm 928 because the bore offer is so long at 25mm. You don’t want 25mm let alone 27mm wide rod big ends in a high rpm motor. A lot of dead weight there that does do one any good.
Luckily, the factory stock S4 setup is nearly perfect for forced induction. Not a lot changed needed as long as the rpms stay in check. And 5 liter displacement is plenty.
Engine block bored out to 114mm and reinforced with Belzona Super Metal. Insert cylinder blocks of similar design as for Volvo (picture) will be installed.
Åke
Lightweight 3.750" stroker crank is 24 Kg or 53 lbs, think I will be able to shave some additional weight off when carrying out the balancing job.
A mill mounted crank balancer like the one I have comes very handy. Do not mind the heavy bob-weights, it is just a mockup for the picture.
Åke.
Holding the bob-weights constant, usually the better and more expensive crankshafts are heavier than the cheaper and worse ones. That’s because how the balancing physics work, a heavier counterweight closer to the crankshaft centerline is usually better in terms of acceleration.
Piston-guided rod setup makes sense for a high-rpm 928 because the bore offer is so long at 25mm. You don’t want 25mm let alone 27mm wide rod big ends in a high rpm motor. A lot of dead weight there that does do one any good.
Luckily, the factory stock S4 setup is nearly perfect for forced induction. Not a lot changed needed as long as the rpms stay in check. And 5 liter displacement is plenty.
‘I agree that standard parts for the boosted application are very good. For this piston guided set up the pin end is exactly 20 mm wide in the piston. The pin is only 1.888” long or roughly 48 mm. This part would be too weak for boost. They normally go to 0.866” or 22 mm for those applications. One fellow on Speedtalk was using NASCAR rods to drag race, from memory his stroke was 3.95” and he took it out to 9,000 to 9,500 rpm with 1,100 hp N/A.
He did break a rod after three seasons of racing, it’s wasnt a Pankl, so far so good with them. He said (and I knew this from talking to Pankl) that they had never had a failure attributed to them in NASCAR. The steel they use (they gave me the technical specs but I lost them🤭 is a triple remelt Vim Var French steel. He said it costs as much as titanium. That’s why if you can use the odd ball sizes used in Nascar they are a great bargain. Depending on your design Pankl rods are around $1,000 each rod if bought new and not in qty. Same for the pins over $1,000 per set of 8.
Lightweight 3.750" stroker crank is 24 Kg or 53 lbs, think I will be able to shave some additional weight off when carrying out the balancing job.
A mill mounted crank balancer like the one I have comes very handy. Do not mind the heavy bob-weights, it is just a mockup for the picture.
Åke.
Very nice Ake, it will depend on what rods and pistons are chosen for the final weight. You can piston guide on a crank guided crankshaft but not the reverse. The crank pictured has a bore spacing of around 112 mm whereas the 928 crank is 122 mm. Also the stroke is longer for the 928 it’s 95.25 mm versus 82.5 mm and that adds weight, the crank pictured was around 38 pounds or 17 kgs.
Piston guided Winberg Toyota crankshaft
in fact in the article on the dirt motors for which Bryant’s made the cranks, they used undercut weights and then put heavy metal in them. That is the style I had in mind. Marti, I think you can see how you can get to 50 lbs with a high degree of certainty. If you look at the crank pictured, it has 53.34 mm journals and standard mains. I was and still might even on my factory crank fit LS main bearings to reduce weight and friction further. The friction reduction comes about via the smaller diameter and th
improvement in the bearing grooving. It only uses 140 degrees versus 220 degrees.
As a hilarious counterpoint, the Viper guys commonly install 9.0 liter stroker kits on the cars, and there are some experimental 10.0 liter kits out there. It's never enough, is it?
Greg, can you please tell me the inside diameter of your 48mm long, 20mm wrist pin. Is it a straight bore or inside taper at the ends?
Sorry about your Nicasil failure.
Åke
You can see the block in the oven in one of those pics, and we had to heat the aluminum quite a bit as a) that's a big chuck of aluminum, and b) we went for a tight press fit. Then we also used Loctite Sleeve retainer in the mating areas.
Cylinder rotation was not considered a big concern. When finished, the block was decked and we sent custom MLS head gaskets along with the engine to the customer. When the heads are clamped down over those MLS head gaskets, those cylinder walls are held quite securely.
Missing from the photos is a little material was removed from the outer walls in the Siamese areas to facilitate coolant flow around the outside of the cylinder walls. Not so much as to weaken the cylinder, of course. The outer cylinder walls do not actually touch each other, and we just widened the gap a little more.
Yes, you certainly could fill the block up to the bottom of the cylinder - but even better would be to fill the block up almost mid-way. All the heat is produced only in the flame area, of course, and that's about the upper third of the cylinder wall. Both Hard-Blok and Morosso make fillers for this.
However, we did not do that, and this engine has been in the field now for 5 years in the customers hands and I have no reports that there is any issue with it. Granted, with stock cams and intake manifold, he is under-stressing the engine.
I have made the same kind of work on many, many motorcycle cylinders and cylinder blocks. Basically you make the sleeves with an interference fit, heat up the aluminum piece to well over 200 C for the sleeves to drop in. However one thing happens when it has cooled down. The aluminum shrink at a higher rate compared to the cast iron sleeves creating an air gap between the sleeve flange and the aluminum block. The upper large diameter part of Carl´s sleeves can be seen as a very think flange. When cooled down using several tons of pressure the sleeves must be pressed down to close the air gap. Failure to press the sleeves down will result in sleeves dropping and blown head gasket.
I find it particularly difficult to perform the pressing down of the sleeves on the huge bulky 928 engine block. I have been thinking of making a special tool where the sleeves can be pressed down using a large threaded bolt.
Carl I very much want to know how you managed to do this?
Åke
Greg, can you please tell me the inside diameter of your 48mm long, 20mm wrist pin. Is it a straight bore or inside taper at the ends?
Sorry about your Nicasil failure.
Åke
Thanks Ake,
yes the pin is straight wall of 0.16” thickness, it weighs about 78 grams. I have an option to use a PPPC pin with is made from C-350 and is longer and thicker. It’s 2” and 0.210” thick, it weighs 100 grams. There would be no risk with these pins, these can take 850 HP but they are used, one race so have some tiny tiny marks. I don’t want buy new pins as they very expensive. I’m going to put it out on Speedtalk to get an opinion on the thinner Pankl pins. The problem is I don’t know how much power I will make with this setup. If it’s 500 hp it’ll be fine, if it 600 it will a question mark.
There is great information in this thread of late. What would be cool, is if we could take all of the positive info and pics in this thread and add it to a Stroker Collaboration thread. So that we could see what others are doing. Set some ground rules about trash talking, and the like and keep it fact based. If you post something negative it could only be about your experience, like you tried xyz and y failed. X & Z were good though. A collaborative exchange of information. We would need mod sponsorship to keep the rennlist out of the thread.. LOL
That the 928 engine platform can handle 900 bhp plus is quite something in itself not to mention the engineering skills it takes to make such modification and to do so reliably. If we conservatively price your skills at $100/hr I am left wondering how much it would cost in real world terms to build such motors considering development/build time and the exotic materials. If we assume 300 hours per custom build and $20k materials that places such motors in the $50k department- does that sound about the right ballpark?
Economy of producing a reliable wet liner motor is important to consider otherwise only a few will ever exist built by mainly engineers as experiments.
It is important to work out what works and what does not work. This will help standardise the method or methods which work reducing waisted money.
The choice to build a 7.0 could then be as straightforward as it is currently to build a 6.0
Gathering information from advocates of the 928 who have gone to great lengths to further the engine development is a key stage along with understanding failures and concerns.
If this can be collated together, even better if people were able to work together then things could move faster.
02-10-2018, 12:31 PM
is a triple remelt Vim Var French steel. He said it costs as much as titanium. That’s why if you can use the odd ball sizes used in Nascar they are a great bargain. Depending on your design Pankl rods are around $1,000 each rod if bought new and not in qty. Same for the pins over $1,000 per set of 8. 
