ka24det vs ka24et

Post by **w1ngzer0** » Thu Jun 05, 2003 7:35 pm

hmmm all this is helpful. SOHC is cheaper for aftermarket but is not as reliable as the DOHC. The DOHC produces more power but not by much also aftermarket is more expensive and the engine is more reliable, pollutes less, and is lighter cause it doesn't use rocker arms...

Is this all correct?

Website · Post by **TurboKA37** » Thu Jun 05, 2003 7:35 pm

c-kwik didnt say they SOHC was heavier just said that the rocker arm set-up is heavier than direct actuated valves

Post by **SingleCamSam** » Thu Jun 05, 2003 7:35 pm

Quote »require a stiffer valve spring to prevent valve float.[/quote]

I wouldn't say "require." I've been running a shadbolt stage II camshaft (similar to pdm's) for about a year now on stock valve-springs (105k miles) with no float problems. You'd only need stiffer springs if you had some crazy 8-roller race cam.

And i think he meant the valvetrain components were heavier, not the engine itself. So which engine is heavier?

Post by **C-Kwik** » Thu Jun 05, 2003 7:35 pm

I wasn't referring to requiring a stiffer spring for a cam upgrade. I was referring to the need to use a stiffer spring on a SOHC over the DOHC to use a cam that achieves the same flow rate. Or to be more clear, the minimum spring stiffness required to prevent valve float would be higher on the SOHC. Didn't mean this was actually the case with the KA's. The SOHC makes less power, so I doubt it's actually opening the valve enough to achieve the same flow rate as the DOHC.

Post by **SingleCamSam** » Thu Jun 05, 2003 7:35 pm

Oops... misunderstood you.

Post by **McAdam** » Thu Jun 05, 2003 7:35 pm

ah ha! yes, but in a DOHC, there is 2X as many exhaust lobes, 2x as many exhaust cam springs, and 2X as many camshaft bearings! not to mention the "jackshaft" that a SOHC doesn't have. but if your going all out, just have all surfaces moly caoted. also, with the SOHC, it would be possible to convert to a roller rocker arm, if one were so inclined. I wonder if anyone has done that yet??

McAdam

Post by **C-Kwik** » Thu Jun 05, 2003 7:35 pm

That is true. And there is definitely some validity to rotating mass. But most of the resistance of a valve train is from the spring itself. And DOHC's can use a lower lift cam with a shallow ramp to achieve the same flow. With a single valve, it has to open more. The cam will have to have more lift and open faster. Since speed is a factor in momentum, the valve will carry more momentum than 2 smaller valves that open less.

As far as roller rockers, they can help reduce friction, but become less effective on lighte valvtrains. They are particularly useful on pushrod motors which is why most V8 heads turn to them at the same time they decide to upgrade their cams.

Post by **w1ngzer0** » Thu Jun 05, 2003 7:35 pm

all this engine talk is making me coo koo :P Cause i understand 1/2 of it :P

Post by **gyfer** » Thu Jun 05, 2003 7:35 pm

2 valve is not better than 1

No evidence support here (I seached Maximum Boost for half an hour), but I read some in somewhere that Single Valve and Twin Valve has it Pros and Cons.

2 valve has bigger "flow area" than 1 valve setup. But when your air is flowing slow, the size "flow area" doesn't make different. Indeed, single valve produce more "swirl" air than double valve ( 2 valve has more turbulence) at low rpm, thus able to produce better torque respone and higher VE.

When it gets high rpm, 2 valve took over 1 valve setup because of its bigger flow area.

For turbo application, in my opinion, I want better & faster spool, thus 12valve KA-E has a little better advantage.

Keep in mind that bigger area (more valve) DOES provide more area for air to flow, but it also increase air turbulence, which turbulence affect air flow proportionally. In same cases, it actually flow worse.

Post by **TomsMR2** » Thu Jun 05, 2003 7:35 pm

^ 2 valves is better than 1. its almost non-debatable. it IS better, and its been proven.

Post by **C-Kwik** » Thu Jun 05, 2003 7:35 pm

http://www.nissanperformancemag.com/may03/nerds/

Feel free to argue with Mike Kojima if you want. He knows what he is talking about.

Post by **gyfer** » Thu Jun 05, 2003 7:35 pm

TomsMR2 & C-kwik,Mike Kojima website support what I just said. DOHC is better in high rpm, while SOHC provide better torque respone in low rpm.

I didn't say SOHC is better than DOHC. They are just different. Therefore depend on your application, DOHC doesn't mean better.

Post by **gyfer** » Thu Jun 05, 2003 7:35 pm

Oh yeah, my mistake.Single Valve doesn't mean must be SOHC.

Lots vechicle has Double valve (16v) on SOHC. Some vehicle has Single valve on DOHC.

Post by **JPRempe** » Thu Jun 05, 2003 7:35 pm

McAdam wrote:I guess its personal preference. dohc will also have more internal friction, marginally. SOHC is cheaper. up to you to decide. I say go for what ever you can get your hands on easiest

JPRempe>>>> actually, there was a datsun 810 made form 77 to 81, I beleive. ugly as hell, came with a L24E.

the Z24 came in like 82 to 88 4 X 4 pickups. and a few other tings. oh yeah, L30's kick ***. torque. lots and lots of torque. a guy at hybridz.org is putting down 255RWHP with over 200 ft/lbs available from like 4000 all the way to redline and a peak of like 275, me thinks. thats some serious motor. all N/A.

so SOHC's can perform too!!

McAdam

The American Maxima started in '81 and has only been powered by a V6 (it was RWD for the first 2 generations). The name Maxima and 810 were only used in conjunction in '81. There was no prior Maxima in the US before '81, although there "might" have been a model 810. And yes, the original Maxima was a butt ugly car.

Post by **w1ngzer0** » Thu Jun 05, 2003 7:35 pm

C-Kwik wrote:http://www.nissanperformancemag.com/may03/nerds/

Feel free to argue with Mike Kojima if you want. He knows what he is talking about.

Great article :thumbup

But im just trying to find the answer what would be better for a turbo setup.. I meen that article was saying

These archaic pieces have a single cam deep within the engine block with long pushrods to connect the cams lobes to the rocker arms. These valvetrains have a lot of flex and inaccuracy in them in addition to a lot of weight. This limits them to low RPM's and heavy valve springs. Even highly modified domestic engines like the ones used in NASCAR, Top Fuel Dragging and Trans-Am are usually limited to about 9500 rpm even it the most radical form of modification. In contrast, the direct acting, shim-in-bucket DOHC valvetrains in Formula One racers routinely hit 17,000 rpm!

Post by **JPRempe** » Thu Jun 05, 2003 7:35 pm

Cool article...

Stock VQ35 internals are good to 9K RPM. I like that

Post by **TomsMR2** » Thu Jun 05, 2003 7:35 pm

the ability to rev has very little to do with a turbo engine on the street.

Post by **JPRempe** » Thu Jun 05, 2003 7:35 pm

Very true, but a little more RPM never hurt for use NA guys (like my Max).

Post by **McAdam** » Thu Jun 05, 2003 7:35 pm

this is fun! I guess you could say that the KA24E is a special case because it has 2 intakes and one exhaust. therefore it is leaps and bounds better than a traditional single valve SOHC set up. i think it would be interesting to take teh two motors, take out the spark plugs and measure, with a torque wrench, how much force is required to turn each one. i think the SOHC would be the victor in this one.

As far as which is better for a turbo set up, depends on what you want. If you want stump pulling, off the line torque, get the SOHC, but if you want some high RPM HP, get the dohc. or, if you want the best of both, get a VATN turbo and the sohc with some major porting!! lol

JRempe>>>> actually, the first labeled MAXIMA came in 81, and that body style lasted til 84, It was RWD, it had a L24E straight 6. it was known as the datsun 810 and the nissan maxima, or datsun maxima. i know because I used to have one. in 85, the maxima became FWD and used the VG30E. i used to have one of those too. I beleive in 85 some were labeled maxima/910. the datsun 810 of the 77 to 80 yrs also had the L24E straight six engine and all the same underpinnings of the 81 to 84 yrs, just a different outward appeareence. also came in a very rare coupe.

Post by **C-Kwik** » Thu Jun 05, 2003 7:35 pm

gyfer wrote:TomsMR2 & C-kwik,Mike Kojima website support what I just said. DOHC is better in high rpm, while SOHC provide better torque respone in low rpm.

I didn't say SOHC is better than DOHC. They are just different. Therefore depend on your application, DOHC doesn't mean better.

Again, this can vary with cam profiles. A DOHC can easily be cammed to be better for low-end torque. It will likely make similar power as a SOHC with that kind of lift, but why use DOHC if you aren't going to rev?

Post by **gyfer** » Thu Jun 05, 2003 7:35 pm

I said Single Valve has better swirl effect, thus able to give you better torque number at low rpm

Post by **C-Kwik** » Thu Jun 05, 2003 7:35 pm

Swirl has more to do with intake port design and/or combustion chamber design. Intake port designs tend to promote a vertical swirl while combustion chamber shape promotes more horizontal swirl or tumble. Both SOHC and DOHC motors can be designed to swirl failry well. But swirl is really nothing more than turbulence. Some DOHC motors and Ferrari's 5 valve motor uses offset intake valve timing(one valve opening slightly sooner) to promote a very good swirl. And swirl is important at all RPM's.

ka24det vs ka24et

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