dohc idea

[cero]

i was on my way to work with a friend talking about cars, and i had a wierd idea: would a dohc work with 2 dif cams? like one bottom end cam and one top end cam in each head?

[AllTheGoodNamesAreGone]

git' your god dam doe-hic out of here..

sounds like some kinda crazy wild vee-tech to me..

lol.. I dont really understnad what you are trying to say here.. but.. yeah.. its pretty irrelevent to our cars..

[cero]

speaking of "irrelevent" thanks for the post.

now what im saying is dohc 2 cams in each head right? now what would happen if you ran 2 different cams. like one made for bottom end and one for the top end?

[MrCoffee]

just in case this helps clear things up...
thats not what VTEC is, if you're friend was using that as an example.

[cero]

im confused, but does someone understand what im trying to say

[njspder]

do you mean using the stock position lower cam to run either intake or exhaust and runnign another cam on each head to perform the other function?
if anyoen came up with an overhead cam conversion it would be really cool. the reduction in parts mass and extra stability of going overhead woudl add a ton of rpm to the power band and allow for more reasonable use of more gear.
anyone wanna try this, there is no budget, and development costs would make it too expensive for anyone to buy. but you would earn the admiration of others, which is worth more than money...really it is. [img]smile.gif[/img]

later
tim

[cero]

at least someone gets it, but i was talking about a real dohc. but from the techincal side would it work

[Dojo2000]

In a real DOHC setup one cam is for the exhaust side and the other is for the intake side.
http://auto.howstuffworks.com/question562.htm

[cero]

ahh thx
DO you think that it would be possible to have it run the way i was thinking?

[CamaroRob97]

I see what your asking cero, no running different cams in dohc woulndt be a very good idea. The car would run so bad and it would vibrate the crap out of you. You probally woulnd't even be able to take it on the highway it be so bad.

[Arctc Wolf]

if ur gonna take it that far, why not just delete the stock cam location, and put 2 cam's in each head? make it a 4 valve head, have 1 cam for intake, 1 cam for exhaust in each head. This would cost a ton of cash, but earn a lot of respect. You would definitely gain a lot of flow and hp from it. RPM range would increase drastically too. it would be a good idea too because our engines are oversquare, meaning we have a bigger bore than stroke. this helps top-end hp a lot, and is ideal 2 use in a 4 valve percylinder motor.

First, u'd have to design the head and camshaft setup. i'd look at the nissan 300Z motors, as well as the ford DOHC 4.6 V8's. those would give u a good idea where 2 begin. once u have the head design, ur gonna wanna figure out a way to spin the cams in each head. u'll have to modify the stock block to somehow turn them. oh, and someone will have to make the heads at some point, which will prolly be the hardest part of the whole thing.

[Lord_Verminaard]

Not to mention that there is basically no way that tall DOHC heads will fit in our cramped engine bays... If you dont believe the size difference, look at the two 3.4 60-degree v-sixes that GM offered- the OHV engine (like the Camaro had) and the DOHC version that the Grand Prix's had- they both basically share the same block and bottom end, but the heads are WAY different, and the DOHC version sits at least six inches taller and nearly 12 inches wider. IMO, not worth all the effort it would take.

Brendan
2000 Camaro L36 M49

[John_D.]

At first glance, this sounds like a good idea.

The problem is, you get the worst of both worlds, instead of the best of both worlds...

For instance, on top end, a lot of valve overlap is good. And advanced valve timing, because things are happening so fast. So you could set up one of the cams this way. The other cam could have less overlap and later timing.

But when you're running at low speed, the high speed (advanced, big duration) cam will be opening the intake too soon and too long. Same with the exhaust. So you end up with the negatives of the big duration cam still hurting performance on the bottom end.

And when running at high speed, the low speed cam (small duration, late opening) will be bleeding off the intake charge and holding the exhaust open too long.

The two cams will be having their valve events occur at different times, but you end up with the earliest one still opening early, and the late one still opening late.

So the net effect is the openings will be early all the time, and the closings will be late all the time, because both cams are operating at the same time.

Variable duration and variable timing are the only way to accomplish what you're thinking...

Unless you had two sets of intake and exhaust ports, and could seal off one set of ports when that cam wasn't needed.

[MustangEater8251]

In theory you coudl it would work... but why not just cram the extra cam in the cylinder like they do now? makes things a little less complicated...

I hope this was hypothetical, cuz to get this to work on an existing car not like this would cost a fortune!

[Ike]

~==

Argh; he's not talking about a conversion here people.

He is suggesting the same thing that lots of people starting out believing is the road of great modifications:

"Hmm...if this part is good for low-end horsepower (read: torque) and that part is good for upper-rpm horsepower, if I use them BOTH then I'll get the best of both worlds!"

Which is of course, ridiculous. [img]graemlins/stickpoke.gif[/img]
[img]graemlins/twak.gif[/img] ;) No, really...
Racers have found that it is best to tune for one or the other--if it was that easy to get everything, then what would be the challenge?

And now for this example (on topic):
I don't think the car would run like crap unless you went with an extreme set of cams. I mean, how would you tune it? It definitely wouldn't make as much "power under the curve" as would be possible if you had set out to design for low, middle, or high regions of the rpm band. And it even might not make as much power as a stocker.

Ok, don't mean to upset anyone, but it was just aggravating to see hardly any replies to the actual question. And I wasn't trying to insult any one, maybe just poke a little fun. [img]smile.gif[/img]

Just try to keep all of you modifications in support of a singular goal--it's the proven road of success.

Of course, I could be wrong...In that case, disregard this post. :D

[ March 23, 2004, 06:07 PM: Message edited by: Ike ]