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how many 7 liter strokers are out there????

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how many 7 liter strokers are out there????

 
Old 02-09-2018, 06:22 PM
  #76  
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Old 02-09-2018, 07:14 PM
  #77  
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7.4? What's the point, exactly?
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Old 02-09-2018, 08:25 PM
  #78  
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Originally Posted by Catorce View Post
7.4? What's the point, exactly?
To have a bigger one than anybody else.
No argument that it an amazing piece of work.

Turbo Todd's car is already so fast he can't run the 1/4 mile at the drag strip. He needs more safety equipment to run as fast as the car can go.
So he runs the 1/8 mile.
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Old 02-09-2018, 08:29 PM
  #79  
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Too fast for the drag strip? Let's put this into perspective. 1000 hp is not much when you compare it to the 2000 UGR Lambos, the 1800hp Turbos, and the 1800hp GTRs. There's guys on Rennlist that run sub 8 second times in their 911 turbos and post videos doing it.
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Old 02-09-2018, 08:39 PM
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Here's a rennlister pulling 8.0 flat on a 997 GT2 with 1890hp. The point of posting this is that you could make a 928 engine 7.4, but it won't ever touch this performance. It's much better to keep the motor under 6.5 and strong for forced induction.

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Old 02-09-2018, 09:40 PM
  #81  
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Originally Posted by Catorce View Post
Too fast for the drag strip?
The drag strip (it's local to me) has rules on that sort of thing.

Once you hit certain trap speeds, or go below certain E.T.s, you are required to have more equipment. Cages, fire suppression, fire suits, that sort of thing.

Todd's car is capable of speeds that put him in a class that the car isn't equipped for.
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Old 02-09-2018, 09:58 PM
  #82  
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Originally Posted by Catorce View Post
Here's a rennlister pulling 8.0 flat on a 997 GT2 with 1890hp. The point of posting this is that you could make a 928 engine 7.4, but it won't ever touch this performance. It's much better to keep the motor under 6.5 and strong for forced induction.

https://youtu.be/v9OyMS7PdMY
This is the truth. Long stroke, small bore, low compression, and turbos is the way to go if you want to make power. Then again, there are other objectives and other self-imposed constraints we put on ourselves in these projects,
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Old 02-10-2018, 12:08 AM
  #83  
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Originally Posted by Marti View Post


Hi Greg, I have seen the billet strengthening ďgirdleĒ that he made, do you know what material he made it from? Feedback on whether this helps will be an important step.

Its looks a good effort to strengthen what appears to be the critical failure point for a wet liner engine.

I believe you have shaved some weight off the crank over the years, What would be required to take it to 50lbs. - even lighter pistons/rods, smaller big ends,



The more weight you take off of the rods and the pistons, the smaller the counterweights can be, which reduces the mass of the crank. It's an uphill battle, since the pistons get heavier as they get bigger. Going down to Honda rod journal sizes (1.88") also would reduce the mass, but on a 95.25mm stroke, the journal overlap gets a little bit sketchy. However, since these "big" engines really shouldn't be reved much beyond 7200 (because of piston speed), the 1.88" rod journal might be OK.

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.
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Old 02-10-2018, 03:21 AM
  #84  
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Originally Posted by Catorce View Post
Here's a rennlister pulling 8.0 flat on a 997 GT2 with 1890hp.
I thought that drag strip looked familiar- Bahrain F1 - awesome performances.

If you want to see something equally impressive try looking at some video of the local chaps drag racing up the sand dunes of Liwa [UAE] in their specially modded 4x4's. They are racing on desert sand up a gradient of 50 degrees! You really have to see this to believe it. It started out as local petrol heads having a bit of fun now it is a major event.

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Old 02-10-2018, 04:03 AM
  #85  
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Does 6.8 count?

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Old 02-10-2018, 05:34 AM
  #86  
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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?
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Old 02-10-2018, 06:54 AM
  #87  
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Originally Posted by FredR View Post
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?
Iíll jump in and say $50K is cheap, to engineer these solutions successfully takes time patience and money. Also lots of knowledge. Iíll post separately to disseminate more info on my journey.
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Old 02-10-2018, 08:24 AM
  #88  
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Originally Posted by Marti View Post
Hopefully I can guide us back on topic,

from the discussion it seems that the wet liner approach is a step further than a dry liner solution.

Larger capacity does appeal to me but there is not a lot of information being shared to help drive forward more builds- a more open source approach might help give people confidence to attempt more builds adding to the overall development of the engine.

Reducing the mass of the rotating parts must help reduce overall forces on the block which could help with perceived weaknesses in the block. More information on this would be very interesting.
ĎHey Marti,

I will Iíll have to answer this question in detail later, the problem with these builds is the amount of custom parts. Then you will have the occasional screw up which will probably not be your fault exclusively. I just had a Nicasil failure, the material didnít stick to the bore, it needs to be atomically bonded but for whatever reason that didnít happen. Another plater told me not to try with Alusil due to the high silicon content. This is due to the fact that silicon doesnít conduct electricity. I donít know what Millenium does to make it stick but given your in the UK, there there is lots of platers but do they know a technique in a very oddball application?



Delaminated Nicasil.


So some caution needs be applied when it comes to Nicasil and the 928 block, this has been quite a set back since it took 15 months to get the blocks back from the plater and now I have to try and salvage something from this mess. I put this out there for this very reason. O.k you might ask, how did it come off? Well I was cleaning it up with my water jet blaster, it is a 13 hp diesel and produces 4600 psi of pressure and basically it managed to get under the Nicasil. Itís supposed to be atomically bonded but the high silicon content stops this. Maybe Millenium puts a coating on the Alusil first and then coats the Nicasil on top of this. Much like chrome plating, copper, nickel, chrome. I dont know.

So so this has meant I had to find another solution and pretty fast too. That solution has come in the form of cast iron sleeves. However RET recently ran an article on sleeves and I hadnít paid much attention to sleeves but there is a big difference in the various materials being offered. Fortunately there is some options at a pretty cheap price. In fact the Porsche 991 has cylinders which are failing and the company I sourced my sleeves from make replacement liners. This cast iron is very strong having around a 50,000 psi tensile strength. CBN is the normal honing method and lots of rings are compatible. My liners are flanged off the shelf items. There are almost as hard as Nicasil or Sume bore without the price tag, this is the material used in the Top Fuel liners.

Now I was going to order my wet sleeves i.e a 7.0 litre package, however this is a setback and I need to concentrate on solving one problem at a time. I did do a CAD drawing of the wet sleeves which I believe incorporates the best of the various designs. Iíll keep that one to myself for the time being. Although there is a group discount for qty, just to put it out there.

Marti you asked about lightening up the mainly the bottom end, well the engine I am now concentrating on cuts at least 5 kgs out of the rotating and reciprocating assembly. I will offset grind the factory crank and get a stroke a bit of 82 mm. Depending on the dollars we will cut more unneeded weight from the factory crank. I believe the standard bob weight is around 2390 grams. This engine will be under 1500 grams.



Factory versus Pankl



O.k, the factory rod and pin weighs 990 grams, the Pankl rod and pin is 660 grams. I have sent details to CP pistons and I am waiting to hear if there have a suitable forging for the piston guided setup. A factory piston weighs around 570 grams, the CP will be around 370 grams, the rings and bearing are lighter also. So if you do some very rough numbers you see that, the piston, rod assembly is 500 grams per cylinder lighter times that by 8 and that is 4 kgs. I then need to reduce the counterweights but the stroke is a bit longer and this adds to the counterweights which is why I say at least 5 kgs.

Regarding the 50 lbs crankshaft, yes it is no doubtably achievable, but it will need plenty of dollars to pay for it. There was a recent article in RET and it was on the dirt motors which are 410 CI engines which matched pretty much exactly my intentions of the full on stroker with wet sleeves. The stroke and main and rod journal sizes were again extremely close to what I intended to run. The engine builder who build around 150 engines a year gives a run down on the pros and cons of Honda rod journals versus 2.0Ē journals, 1.00 mm rings versus 0.8 rings, 2.45Ē mains versus 2.65Ē etc. You will get greater life from bigger components however in our case they weigh more, this adds to mass forces.

So I donít know when the full on engine will be built due to this stuff up, however this little engine, a 351 CI has plenty of nice bits, mainly from NASCAR, the rods, pins,pistons,rings and valves come from there. Here a few more pics.....



Pankl small end details


Sawtooth big end


Pankl pin


Reinforced big end.

I should add there is a lot of precision needed with high performance setups, they run pretty tight clearances, however you will notice from the parts lots of strength built into them. The example that perfectly demonstrates this is the rods. The bottom end cap of the rod is very stiff and the cap cannot move around due to the sawtooth design. The reason they use this is that the piston guided setup runs a tight clearance on the rods. So you cannot afford deflection. However there is a reason nearly every top race engine is piston guided. There are reduced friction and the whole assembly is lighter.


When you cut away weight on the rod piston side you get to remove more on the counterweight side. Hence removing the unneeded crank guided design aspects results in considerable weight savings.
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Old 02-10-2018, 01:14 PM
  #89  
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When boring out the engine block to 114mm or 4.500" you will break through the walls at these points front and rear. It will allow up to 110mm bore, 7242cc with a 3.750" stroker crank.
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front and rear.
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Old 02-10-2018, 01:28 PM
  #90  
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The boring bar I made for boring out the engine block.
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