I've had an 89 sohc and now have a 94 dohc, both stock. My seat of the pants assesment is the sohc pulled harder from low rpm. Lower HP but more torque perhaps? Or, it could just be that my dohc is a dog.

 

was your 89 stick? you 94 is an auto for sure (convertable) so that could explain it. the sohc duzn't have more torque tho.

 

bottom line is that both engines are surprisingly good and can handle the abuse of heavy footed guys and girls.
i've seen examples of both stock, boosted and built. all can hang with the more technologly advanced motors on the market.

so bottom line is

 

actually i'm pretty sure they hav the same compression..nissan lied...there's a post on freshalloy about dohc vs sohc in the basic 240sx section and they showed that it had the same compression..but i'm not sure if its true?

 

Post a link.

 

i saw a cpoy of a TSB where nissan lowered the CR of the sohc for driveability issues
but i also saw conclicting reports of the KA24DE engines CR between the S13 and S14

 

http://socal**********/faq/images/92c.jpg <- here's the link guys..not sure how reliable it is but it says nissan corp so it should be a pretty good source...wat's fsm? thats who they said did the stats..maybe different years had different c/r?

 

FSM = factory service manual

c/r = compression ratio

Here is my assesment, i think the SOHC motor has a better accelration and torque than the DOHC. But the DOHC has better top end. I have out accelerated altimas and other 240's with the DOHC motor, but once i hit top end, they creep up, then keep on going. Plus that 115mph speed limiter doesnt help.

by the way, what is the compression for each cylider suppose to be in terms of psi in a SOHC motor?

I love the SOHC motor, but i want a DOHC motor, which we know won't be a KA but either a CA or SR, (most likely SR)

 

how can a SOHC have better acceleration. the DOHC has more hp, more torque, and a similar powerband. maybe you just can drive better than the guys w/ the DOHCs.

i really don't see how the SOHC could be better. maybe it's got the same potential, but how could it have more.

 

I have driven both, and i think the SOHC has the better acceleration. stock to stock. racing wise, i have beaten DOHC motors. who knows, it may be driver, but I don't think that I am that great of a driver on these cars, i'm still learning. Maybe I will try one right after the other, and see what it feels like. I personally wanted one with a DOHC because of the ease of the SR swap, but I was able to afford the SOHC equipped 240, and I love almost every minute of it.

 

May be the 3 valves a cylinder flows better at low rpms while 4 valves a cylinder flow better at higher rpms?

 

one cure for the sohc top end whoes is an apexi n1 exhaust which vastly improved my cars drivability on the intersate,(as long as you don't mind the noise) though i honestly can't say wich is better, and keep in mind if your racing a 95 up 240 that they are heaveir than the s-13's wich are lightest 89-90 in coupe form.

 

my top end sucks, i found out how to cut off the speed limiter, i just don't knon wifh of the 2 wires to cut to tke it off

 

ain't it the green wire with red stripe?

 

i was originally told to cut the yellow wire with the green stripe on the ecu. that controled the fuel pump shut off. problem was, the fuel pump was shutting off at 3000rpms. so needless to say, that wasn't the plan. then i found out that the speedlimiter is controled by a signal from the tranny to the speedometer. if you disconnect the wire, your speedometer and odometer stop working, so the ecu doesn't know to cut the flow of fuel. but there are 2 wires from the tranny that are routed together. I don't know which one controls what, and i don't want to cut the wrong one since they are exposed to the elements.