3.2 or 3.5? Piston Velocity/Acceleration Curves
#1
Safety Car
Thread Starter
3.2 or 3.5? Piston Velocity/Acceleration Curves
All.
I did some preliminary investigation of the benefits/ill-effects of upgrading to the 3.5 using STOCK parts with limited customization. Attached are curves depicting piston accelration at 8000 RPM for the stock 3.2, stock 3.5 and 3.5 using 3.2 rods.
It appears that stroke is the important factor here. There isn't really a big difference... and I don't think anybody plans on going past 8K RPMS anyways:
http://photos.yahoo.com/bc/gunjan_ra...c=ph%26.view=t
More on this later...
I did some preliminary investigation of the benefits/ill-effects of upgrading to the 3.5 using STOCK parts with limited customization. Attached are curves depicting piston accelration at 8000 RPM for the stock 3.2, stock 3.5 and 3.5 using 3.2 rods.
It appears that stroke is the important factor here. There isn't really a big difference... and I don't think anybody plans on going past 8K RPMS anyways:
http://photos.yahoo.com/bc/gunjan_ra...c=ph%26.view=t
More on this later...
#4
ex 6 Speed owner :(
Join Date: Jun 2002
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If you know the rod length, you can also derive acceleration numbers from one of the calculators here:
http://www.slowgt.com/Calc2.htm
I can't comment on its validity, but looks good to me.
http://www.slowgt.com/Calc2.htm
I can't comment on its validity, but looks good to me.
#5
Safety Car
Thread Starter
Hey that's a cool site... saves me some math in the future!
There are two larger effects of rod-ratio and several smaller effects. Larger effects include:
(1) Piston speed/acceleration and motion dynamics (forces on the rod, wrist-pin, crank etc.)
(2) Dwell-time (time the piston spends at TDC)
The real purpose of graph was to ondicate that there ISN'T a very significant difference between the MDX block and the CL-S block at 8K rpms in terms of piston acceleration. Dwell-time changes and hence hence limits very aggressive cam profiles.
Just stuff to think about.
There are two larger effects of rod-ratio and several smaller effects. Larger effects include:
(1) Piston speed/acceleration and motion dynamics (forces on the rod, wrist-pin, crank etc.)
(2) Dwell-time (time the piston spends at TDC)
The real purpose of graph was to ondicate that there ISN'T a very significant difference between the MDX block and the CL-S block at 8K rpms in terms of piston acceleration. Dwell-time changes and hence hence limits very aggressive cam profiles.
Just stuff to think about.
#6
Liquid Ice
So is what you're saying basically that we can continue to use our existing block and just grab the MDX rods and end up with pretty much the same results as if we got the MDX block put in our cars?
Sorry I don't know much about cars, but I am pretty interested in getting the 3.5L upgrade..
Sorry I don't know much about cars, but I am pretty interested in getting the 3.5L upgrade..
#7
Safety Car
Thread Starter
The rods won't make a difference.. in fact you should use the CL-S rods as they are longer. You have to use the MDX crank, however. The problem is the pistons. If you use the MDX crank and CL-S rods, you have to get custom pistons. I think the CL-S pistons are 346grams each, so you want to definately be lighter than that!
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#8
Liquid Ice
Originally posted by allmotor_2000
The rods won't make a difference.. in fact you should use the CL-S rods as they are longer. You have to use the MDX crank, however. The problem is the pistons. If you use the MDX crank and CL-S rods, you have to get custom pistons. I think the CL-S pistons are 346grams each, so you want to definately be lighter than that!
The rods won't make a difference.. in fact you should use the CL-S rods as they are longer. You have to use the MDX crank, however. The problem is the pistons. If you use the MDX crank and CL-S rods, you have to get custom pistons. I think the CL-S pistons are 346grams each, so you want to definately be lighter than that!
How were people like TypeR doing this in the past? using all MDX parts for the crank, pistons, rods and block?
#11
Safety Car
Thread Starter
One of the folks on this board e-mailed me the complete vehicle specifications for ours cars... so if you PM me with your e-mail, I'll just e-mail it to you.
-OR-
MODS: Let me e-mail this to you... and you guys post it in the 'useful info' section! They are .pdf's
-OR-
MODS: Let me e-mail this to you... and you guys post it in the 'useful info' section! They are .pdf's
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