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Crank Strength And Upgrading Options.

LedZepLen

By LedZepLen,
in Engines & Forced Induction

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Spoolup Mentor

Spoolup

Posted
Posted (edited)

I have received the 2 x 95mm stroke cranks. I am going to build a new bottom end for my engine using one of them. I will use the exact same supporting parts ( head, turbo, cams, exhaust etc etc ) as on my current RB30/25. This way I can do a back to back comparison between the two engines ( apples to apples ) and overlay the two dyno charts. By doing this there will be something to compare the stroker crank setup to, as opposed to just building a completely new engine and having no base as a comparison.

I am just waiting on the new rods to go with the cranks and I can start the build.

Ill post up some pics of the cranks soon.

Edited by Spoolup
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nismomiles33
nismomiles33

I used a grub screwed, machined and balanced, nitrated standard crankshaft (Nizpro spec??) .. should hold up with most, I was told that should be good for 800+HP.

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Gerg_R31 Mentor

Gerg_R31

Posted
Posted
I have received the 2 x 95mm stroke cranks. I am going to build a new bottom end for my engine using one of them. I will use the exact same supporting parts ( head, turbo, cams, exhaust etc etc ) as on my current RB30/25. This way I can do a back to back comparison between the two engines ( apples to apples ) and overlay the two dyno charts. By doing this there will be something to compare the stroker crank setup to, as opposed to just building a completely new engine and having no base as a comparison.

I am just waiting on the new rods to go with the cranks and I can start the build.

Ill post up some pics of the cranks soon.

are the cranks balanced? or knife edged like the other stroker cranks?

Travis Trayhern Proficient

Travis Trayhern

Posted
Posted

sounds very intresting, hope it goes smooth the build up and has some nice improvments throughout the power range.

what sort of price is this kit?

I have received the 2 x 95mm stroke cranks. I am going to build a new bottom end for my engine using one of them. I will use the exact same supporting parts ( head, turbo, cams, exhaust etc etc ) as on my current RB30/25. This way I can do a back to back comparison between the two engines ( apples to apples ) and overlay the two dyno charts. By doing this there will be something to compare the stroker crank setup to, as opposed to just building a completely new engine and having no base as a comparison.

I am just waiting on the new rods to go with the cranks and I can start the build.

Ill post up some pics of the cranks soon.

  • 4 weeks later...
  • 3 weeks later...
Gerg_R31 Mentor

Gerg_R31

Posted
Posted

I've been playing around with an engine dyno/ calculator simulator and its calculated roughly a before and after figures of horse power torque etc with the stroker crank

(as long as i have had all of the motors figures including flow figures at each measured level, i have gotten very similar to what has been acheived on a real dyno -/+ 1-3hp)

all 4 have exactly the same specs as you will see, though what is not shown is both have a 64cc in combustion chamber, 10cc piston dome, 4cc valve releif in piston and a flush deck height

this is not a garanteed before and after power results with the stroker crank but a simulation/ comparasion of what results may be expected with only change in stroke, results will vary depending on supporting internal and external componants

Non-Turbo

stocker.jpg

stroker.jpg

i have also added a turbo set up, everthing is still exactly the same, just with a turbo of which i chose from a drop down menu in the program. I am also aware that different turbos and supporting mods will change the end results

Turbo

turbo_stocker.jpg

turbo_stroker.jpg

Rolls Grand Master

Rolls

Posted
Posted

Be interesting to see what numbers that program gives for a 3L and then overlay the power/torque curves on the same graph, give a nice visual representation of where in the rev range the gains will be had.

Spoolup Mentor

Spoolup

Posted
Posted

I will be assembling the new stroker bottom end soon. The custom rods arrived today

This will be run on my exact same setup that I have used with the 3.0L bottom end. Same turbo, head, comp ratio, cams, exhaust, etc etc

So I will be able to overlay my previous setup compared with the stroker engine ( ie dyno power and torque curves )

So a straight up comparison will be available.

nzeder Newbie

nzeder

Posted
Posted
Trial cranks due next week

post-220-1250841471_thumb.jpg

So looks like these are not full counter weighted (assume the pic is of the 95mm stroker crank) I would have thought if you were going to the effort of building a custom crank it would be fully counter weighted?

Would the 95mm stroke generate more harmonics and having it full counter weighted might help reduce some of this? I am not an engine builder or engineer so just putting this out there for others more in the know to reply with more logical info.

Love the idea :) of a 3.4l hmm if my RB26DE powered 260z (shell still in bits) does not cut it looks like I might have to consider installing one of these stroker crank like this into a RB30 bottom end and slap on my 26 head for 3.4L of NA power

Rolls Grand Master

Rolls

Posted
Posted
So looks like these are not full counter weighted (assume the pic is of the 95mm stroker crank) I would have thought if you were going to the effort of building a custom crank it would be fully counter weighted

Yeah I was going to say how did you do all the calculations for the size and shape of the counter weights and balance it?

Spoolup Mentor

Spoolup

Posted
Posted (edited)

As these are the trial / prototype cranks we just copied the std crank. The std crank does a terrific job and sees 10000 rpm in serious drag engines. Why reinvent the wheel. Having said that - if I have any dramas with these cranks its an easy job to have the next version redrawn into full counter weight cranks.

I have had the cranks checked and balanced here in Oz - all good.

Yeah I was going to say how did you do all the calculations for the size and shape of the counter weights and balance it?
Edited by Spoolup
  • 3 weeks later...
  • 3 weeks later...

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