lsvtec build

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Yes i was plaining on building a lsvtec and i was reading a bunch of things about the bottom end not being able to handle the rev that the b16a head can give out. So i was wondering what maybe a good set up on the bottom end so it can handle it.
 
Originally posted by JDM91SIR@Jul 24 2005, 10:05 AM
Yes i was plaining on building a lsvtec and i was reading a bunch of things about the bottom end not being able to handle the rev that the b16a head can give out. So i was wondering what maybe a good set up on the bottom end so it can handle it.
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You could de-stroke the motor by around 5mm effectively creating a near perfect rod/stroke angle and thereby increasing the rpm capabilities.

Or something like that. :p

Edit - Wow. I actually just went and did the math and to have a "perfect" rod/stroke ratio of between 1.75:1 and 1.8:1 you would need to de-stroke the motor by 13mm, if you are using the LS rods. 76mm of stroke seems about perfect. Which is also mysteriously the stroke of a B16 engine from the factory.... :p


BTW- to get your rod/stroke just divide your rod lenth by your stroke. For example -

Ls rods = 137 mm
LS stroke = 89 mm
137 / 89 = 1.53:1 which is poor, yes.
 
If you want to rev high on your ls block a little more "safely". Replace your stock rod bolts with ARP. Get a crank girdle, aftermarket or oem(but not totally necessary).

Revs are mainly determined by the head and not the block. And a perfect R/S ratio is all theoretical numbers any way. A gsr I beleive is 1.58:1 not much different than an ls and I rev to 9500 to 10,000. Its all in the head.
 
I have a B16 SIRII head and LS block. The head has upgraded valvetrain and the block has a built bottom end. It sees 9k everyweekend
 
Originally posted by 97CTR@Jul 24 2005, 01:55 PM
And a perfect R/S ratio is all theoretical numbers any way.



:blink:


WTF are you talking about? There is nothing theoretical about it. For minimal cylinder wall loading you want your stroke to be exactly 57% of the length of your rod. If you had a 100mm rod then a 57mm stroke would be considered "perfect". R/s ratios have more to do than cylinder wall loading though, it also affects piston speed as well, which in turn affects power and gas consumption. Also by running a longer rod you increase the "dwell" time of the piston at TDC and create more torque with the same piston speeds.

You obviosly need to read up a little more on engine building before you go calling r/s ratios "theoretical".
 
sorry let me clarify, when I said that no perfect r/s ratio exists I was reffering to making power. There is no set or standard r/s ratio that is going to make you the most power.
 
Originally posted by 97CTR@Jul 25 2005, 07:30 AM
sorry let me clarify, when I said that no perfect r/s ratio exists I was reffering to making power. There is no set or standard r/s ratio that is going to make you the most power.
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Yes there is. There is a reason that Bizi de-strokes his f22 down to 1.8:1 r/s. It's considered "perfect"
 

phunky.buddha

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No... that's just the "best compromise" between streetable power and cylinder wall side loading. If you want to rev even higher, you can take your ratio up to 2:1 or more- great for extremely high revving power like motorcycle engines, but horrible for torque down low. It's all about compromise. Bisi knows this too.
 
Originally posted by Calesta@Jul 25 2005, 10:55 PM
No... that's just the "best compromise" between streetable power and cylinder wall side loading. If you want to rev even higher, you can take your ratio up to 2:1 or more- great for extremely high revving power like motorcycle engines, but horrible for torque down low. It's all about compromise. Bisi knows this too.
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Fucker. :p
 
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