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Discussion Starter #1
does anyone know the differences between a b13 sr20de and a b15 sr20de?
i know the b15 sr20 has 5hp and 4lbft more torque, but is that it? also doesnt the earlier sr20 redline later than the b15 sr20?

thanks in advance
 
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The b13 sr20 has a 8 counterweight crank and hydraulic valvetrain. The b15 sr20 has a lighter (4 counterweight?) crank and roller valvetrain. Older sr20's also had a different intake manifold.
 

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bitter old man
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1991-1994 SR20 redlines at 7,500 rpm later models redline at 7,100.

As to why, moving parts experience friction. Friction eats power. Friction increases exponentially with rpm. Reducing the rpm at which a specific power can be achieved reduces power lost to friction and increases fuel efficiency.
 

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Discussion Starter #5
does this affect the powerband? or is the powerband different in the newer motors? also wouldnt a synthetic oil help with the friction?
btw my b15 sentra redlines at 6750rpms.

sorry for all the questions.

thanks
 

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bitter old man
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Power band is determined by cams and engine design. Friction just lowers the magnitude of power.

Synthetic oil does help, but friction is still there, it still increases exponentially with rpm, lower rpm equals milder engine design to attain target power. Milder design equals cheaper build and longer life.

I forgot the QR25 has such a low redline. You can't say B15 because 2001-2002 Sentras are B15 and use roller-rocker SR20.
 

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Discussion Starter #7
by b15 sentra i meant the 2000-2001 se that came with the sr20de. that is what i have. the b15 +2002 will only have a 1.8lt or the 2.5lt. i have no idea what a qr25 redlines at. i would guess it would be kind of low since it has more displacement.

one more question, what is a roller rocker? im guessing it has to do with the valve train.

thanks again
 

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Platinum
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SR20 Rocker arms

shaolin_racer said:
one more question, what is a roller rocker? im guessing it has to do with the valve train.

thanks again
There are two different SR20 Rocker arms. One on right is roller rocker arm, the other one is solid rocker arm. Roller ones are suppose to be smoother, but if you over rev the motor, that thing is going to give you problems. I think this is one of the main reason B15 redline had to go lower. JDM SR20DE made after September 1995 came with roller rocker arms. But people are swapping back to solid rocker arms for more rpm and reliability.



 

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bitter old man
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2000 was first model year with roller rockers, and it's the one on the left in the picture.

SR20DE
1991-1994: 7,500 rpm redline
1995-1999: 7,100 rpm redline
2000-> shrug

GA16DE: I don't know.
GA18DE: I don't know.
QR25: I think it's 6,750 rpm.
 

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There is a short, but excellent write up comparing the roller-rocker -vs- non-roller-rocker SR20's in the June 2000 SCC on page 191. This is the same issue as the SR20 cam comparo test.
 
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