lsvtec build

[JDM91SIR]

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.

 

[sohcslammer]

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.

[post=530370]Quoted post[/post]​

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.

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....


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.

 

[97CTR]

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.

 

[94CivicSlow]

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

 

[sohcslammer]

Originally posted by 97CTR@Jul 24 2005, 01:55 PM
And a perfect R/S ratio is all theoretical numbers any way.

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".

 

[97CTR]

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.

 

[sohcslammer]

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]

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.

 

[sohcslammer]

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.

 

[phunky.buddha]

Originally posted by sohcslammer@Jul 25 2005, 10:16 PM
Fucker.

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