SOHC versus DOHC? Advantage Disadvantage?
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Originally Posted by 82801BA
No, in reality, DOHC engine makes less output than SOHC engine.
Think, in general, better compare it with non-VTEC for fairness.....
A SOHC F22A4 Accord engine makes 130hp at 5200rpm, while a F22B Prelude engine makes 160hp at 6000rpm. It has a 30hp difference across 800rpm. But also take into account that F22B has intake air bypass(which helps top end with shorter intake runner. In an Accord engine, that means 10hp) while F22A4 doesn't.
In term of VTEC, we have D16Y8 SOHC engine with 127hp at 6600rpm and B16A2 Si engine for 160hp at 7600rpm. Majority of power of B16A comes above 4800rpm. But most Si are around 140 at the wheel and most D16Y are making 110. However, D16Y has a more flattened curve than the Si anyway. So rpm to rpm, stock to stock, SOHC engines makes more power at any specific rpm, up to where the maximum power is set at.
I just found an Si dyno with only 82whp at 5000rpm, can't believe that. I have my EX peak set at 5300rpm for 117whp. And SOHC engine also has weight/inertia advantage over DOHC. A SOHC engine breath better(I really don't know why, but I've heard a lot about it) at low rpm therefore also generates higher torque than DOHC engine at the same range.
Think, in general, better compare it with non-VTEC for fairness.....
A SOHC F22A4 Accord engine makes 130hp at 5200rpm, while a F22B Prelude engine makes 160hp at 6000rpm. It has a 30hp difference across 800rpm. But also take into account that F22B has intake air bypass(which helps top end with shorter intake runner. In an Accord engine, that means 10hp) while F22A4 doesn't.
In term of VTEC, we have D16Y8 SOHC engine with 127hp at 6600rpm and B16A2 Si engine for 160hp at 7600rpm. Majority of power of B16A comes above 4800rpm. But most Si are around 140 at the wheel and most D16Y are making 110. However, D16Y has a more flattened curve than the Si anyway. So rpm to rpm, stock to stock, SOHC engines makes more power at any specific rpm, up to where the maximum power is set at.
I just found an Si dyno with only 82whp at 5000rpm, can't believe that. I have my EX peak set at 5300rpm for 117whp. And SOHC engine also has weight/inertia advantage over DOHC. A SOHC engine breath better(I really don't know why, but I've heard a lot about it) at low rpm therefore also generates higher torque than DOHC engine at the same range.
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Rep Power: 0 I didn't say SOHC is better than DOHC. What I mean is that, a SOHC can perform better than DOHC. Not to mention anything beyond max power rpm. So I'm only comparing 6300rpm to 6300rpm, assume a SOHC engine has max output there, and a DOHC also having the power at that point WITHOUT any further reving up.
I guess you are talking about breathing at high rpm, because SOHC engine cannnot take the high rev for good intake/exhaust. But low and mid rpm it's always a SOHC rule.
I guess you are talking about breathing at high rpm, because SOHC engine cannnot take the high rev for good intake/exhaust. But low and mid rpm it's always a SOHC rule.
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Rep Power: 0 There's a real good example with the Cobra...the 5.0 was a SOHC. You couldn't rev it as high...like 5K or 5500 rpm redline. It's a monster on torque thru the lower/midrange. They swapped the Cobras over to the DOHC 4.6 in 1996. They can be revved much higher than a SOHC...7k redline for the DOHC. By comparison, the SOTP torque feels like a dog below 4000rpm. Without taller gears they are slugs off the line. The torque takes off unimaginably about 4000 rpm and holds it thru about 6500 before power fades off. So, SOHC...much more lowend torque, much lower redline...DOHC...slow build-up on power, but much higher redline. I will say this...the SOHC motors are infinitely cheaper to make faster tho. You are playing russian roulette with any 5.0 Mustang/Cobra you line up against. You can make one 400+ rwhp for about 2500 dollars.
Last edited by Yellow98SVT; Jan 10, 2005 at 08:11 PM.
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Rep Power: 0 Without much higher rpm available, a DOHC has no advantage over SOHC, only disadvantages.
I had a 99 Civic Si before, the low/mid just sucks until VTEC kicks in, and beyond(say 5500+ to 7800rpm).
I had a 99 Civic Si before, the low/mid just sucks until VTEC kicks in, and beyond(say 5500+ to 7800rpm).
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