Seeing how Honda still uses single overhead cam designs for many of> their engines and they outperform virtually every other engine in their> classes, I'm curious on the real benefits of having DOHC. Even GM's OHV> engines seem outperform some comparable DOHC engines (the 3500 V6> compared to Hyundai's 3500 or Lexus's 3.0 V6, for example). Is this> mostly a marketing gimmick?

Masospaghetti <gtg803x@mail.gatec­h.edu> wrote in> news:cu8ttp$lc3$1@n­ews- int2.gatech.edu:>

No.> Many Honda's use an internally rotateable camshaft, in order to alter > valve timing on the fly.

Seeing how Honda still uses single overhead cam designs for many of> their engines and they outperform virtually every other engine in their> classes, I'm curious on the real benefits of having DOHC. Even GM's OHV> engines seem outperform some comparable DOHC engines (the 3500 V6> compared to Hyundai's 3500 or Lexus's 3.0 V6, for example). Is this> mostly a marketing gimmick?

Honda's 3.0L V6 - 240 HP, 210 lbs-ft, 21/30 mpg, reg unleaded> Toyota's 3.0L V6 - 210 HP, 220 lbs-ft, 20/28 mpg, premium unleaded> Lexus 3.0L I6 - 215 HP, 218 lbs-ft, 18/24 mpg, premium unleaded>

Honda's 3.0L V6 - 240 HP, 210 lbs-ft, 21/30 mpg, reg unleaded> Toyota's 3.0L V6 - 210 HP, 220 lbs-ft, 20/28 mpg, premium unleaded> Lexus 3.0L I6 - 215 HP, 218 lbs-ft, 18/24 mpg, premium unleaded>

I meant outperform mainly by engine output and fuel economy.

В« Paul В» wrote:> > Masospaghetti wrote:> >

Honda's 3.0L V6 - 240 HP, 210 lbs-ft, 21/30 mpg, reg unleaded> Toyota's 3.0L V6 - 210 HP, 220 lbs-ft, 20/28 mpg, premium unleaded> Lexus 3.0L I6 - 215 HP, 218 lbs-ft, 18/24 mpg, premium unleaded>

I meant outperform mainly by engine output and fuel economy.> Even Toyota's new 3.3L V6 doesn't produce as much power as Honda's 3.0,> and gets worse mileage.>

GM's 3500 V6 makes more power AND torque than Hyundai's 3500, as well as> getting much better fuel economy. Likewise, it has favorable output> numbers to Ford's Duratec 30 engine, which is a DOHC design.

http://www.leecao.c­om/honda/vtec/index.­html

a system to vary the valve timing by rotating the camshaft relative to the> drive sprocket, using either oil pressure, or an electric motor. But this> was many moons ago, and may have been a different manufacturer.

I have also heard that DOHC is only makes a difference on the highway> where you probably don't need the extra power anyway. It's around town> driving that matters to me.

Dan, i've asked one question twice because my newsgroup client showed no> responses and still shows no replies for that thread. I said this in my> email that I sent you and got no response, and if it makes any> difference, I still am interested in your "extremely detailed" reply to> my HIR/Nighthawk question.

On the other hand, I doubt if my old OHV car can go much over 100 mph.

I don't think there are many 3 or 5 valve/cylinder engines left.> Does anyone still make a 5 valve/cyl engine any more?

Masospaghetti wrote:>

The method used to actuate the valves has ZERO correlation with > performance.

Steve <no@spam.thanks> wrote in news:SpGdnZeHVYBNuI­zfRVn-uQ@texas.net:>­

But it does have quite a bit to do with maximum engine revolutions.>

Reducing valve train weight allows higher valve speed before they start to >float.>

-- >TeGGeR®>

The method used to actuate the valves has ZERO correlation with > performance. I'll give GM credit for never jumping on the OHC bandwagon > just because Condemner Retards keeps calling pushrods "archaic" and > "tractor-like" or whatever other stupid phrase strikes their fancy.>

I don't know. The only DOHC engine from GM I encountered, had the belt? > jump timing and damage a spark plug. It took a rare, tool to try to reset > the timing for both cylinder banks. If you can find the tool.

'98 Saturn SL has OHC, and the '98 SL2 has DOHC. Both have a timing chain. >

The OP's DOHC that jumped time could have been the short-lived DOHC> Chevy 3400 (not much relation to the pushrod 3400 at all). It was a real> junker.

Yes, it was. Truly a turd.>

But the facts are that a well designed DOHC engine gives you a lot of> potential for performance. Pushrod engines can do well, but advanced valve> train designs can,> when optimally tuned, run rings around them.>

GM just did a shitty job on the 3.4.>

The old Mercedes desmodromic valve system was extremely potent for its time,> as an aside.>

You can get a lot of power from cubes and pushrods, but the high tech> valves, high RPMS, etc are the art of the tuners technology.>

Yes, it was. Truly a turd.>

But the facts are that a well designed DOHC engine gives you a lot of> potential for performance. Pushrod engines can do well, but advanced valve> train designs can,> when optimally tuned, run rings around them.>

On 4/7/2005 7:35 PM, HLS wrote:>

Can't a DOHC engine generally rev higher than a pushrod?

"Advanced" valve trains (OHC has been around since the 1930s, so I don't> see why people consider it "advanced") only *BEGIN* to have an advantage> at about 7000 RPM. You have to go higher than that to really benefit> from the advantage. How many production engines operate in that regime?> The Honda VTECs are about all I can think of. Why the HECK is the Ford> 5.4 built as an OHC? Or the Chrysler 4.7? Neither of them spin all> that fast, and in fact The Chevy Gen III v8s and the Chrysler 5.7 Hemi,> both with pushrods, mop the floor with the OHC Ford Modular engines. I> can kinda see it in the case of the Northstar because it does wind a bit> tighter and has to be a very small package (no room for good 2-valve> Hemi heads, so it uses more compact 4-valve pent-roof heads that work> better with OHC).