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Location:
Sydney
Registered:
May 2002
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Why is a twinky better than a single cam
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Tue, 15 April 2003 07:43
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Hey all
Just wondering why a Twin cam has better performance than a single cam
Logic suggest that with another cam shaft theres more precision with the timing of the valves ???
Ta
Mani
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I supported Toymods
Location:
Northern Beaches
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Tue, 15 April 2003 08:11
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my thoughts are that with 4 valves you can have better positioning than with only 2 ie. having more surface area of openings. Which gives a greater amount of flow in and out of gases.
Im probably wrong though 
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Location:
Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Tue, 15 April 2003 08:16
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Wasnt talking about having more valves...
or i suppose another camshaft means more valves ???
Cause i understand how more valves helps ...
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Location:
was adelaide now newcastle
Registered:
February 2003
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Re: Why is a twinky better than a single cam
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Tue, 15 April 2003 08:46
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in a twin cam engine with only two valves per cylinder i understand that the correct shape of the combustion chamber can be acheived.
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Location:
c'town, NSW
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Tue, 15 April 2003 09:02
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go to bill sherwoods website he has a write up on this very question.
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Location:
Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Tue, 15 April 2003 09:16
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Ok sweet
a link would be good Rob
Thanx
Mani
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Location:
c'town, NSW
Registered:
May 2002
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Location:
Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Tue, 15 April 2003 09:41
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umm....your link doesnt work
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Location:
c'town, NSW
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Tue, 15 April 2003 10:21
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whoops.... i mean yes it does work!! just ignore [Updated on: Tue, 15 April 2003 20:19] in that post 
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: Why is a twinky better than a single cam
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Tue, 15 April 2003 10:23
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cross-flow is king baby 
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Club Member
Location:
Sydney, NSW
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Tue, 15 April 2003 10:23
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| rob_RA40 wrote on Tue, 15 April 2003 19:34 |
FFS
http://www.google.com.au
type +"bill sherwood" in the search field
want me to come over and hold your hand while u do it? 
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ROFL...
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Location:
cambo
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Tue, 15 April 2003 10:59
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i think it also has something to do with the angle of the valves which is also why a GE is better than an FE cause GE has a wider angle to the valves than the FE. so the G and F doesnt just stand for seperate cam gears for G and scissor gears for F.
my thought on the opinion anyway.
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Tue, 15 April 2003 11:47
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My stuff on why four valve engines are so much better than two valves can be found here - http://www.billzilla.org/2v4v.htm
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Tue, 15 April 2003 12:17
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"the push-rods often voice their disapproval by falling apart, frequently poking expensive holes in things on the way)"
bill, you have a way with words that gives me the giggles
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On Probation
Location:
North East NSW
Registered:
December 2002
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Re: Why is a twinky better than a single cam
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Tue, 22 April 2003 07:03
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i find it amusing that you had to ask where bill sherwood's webpage is, and didn't even have the common sense to go looking for it yourself. of course, if you had done some research yourself in the first place, this thread would never exist
so in future, learn the below two websites before you go wasting people's time asking questions that have been answered many times before
www.howstuffworks.com
www.google.com
(warning : advanced subject matter keyword skills needed)
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Location:
Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Tue, 22 April 2003 07:39
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Ok guys the reason i ask on a forum is because i dont like asking one person
because generally speaking, i have more chance of finding out the most correct and unbiased response by asking in a forum with many ppl responding, as oppose to looking at a website that one person has decided upon
is that not fair ???
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Location:
Hornsby, Sydney
Registered:
October 2002
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Re: Why is a twinky better than a single cam
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Tue, 22 April 2003 07:52
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A twin cam has less moving parts such as push rods, rocker arms pivots ( dont move but do create friction).
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Tue, 22 April 2003 13:22
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I'm with mani.... if you go researching, you tend to spend a lot of time finding different opinions.
if you ask on a forum and get a response others think is wrong, there's guaranteed to be an argument to follow, and usually the result is a lot of *very* helpful info, with more knowledgeable people weighing in to their side of the argument.
PS. howstuffworks is one of the greatest websites ever
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Registered:
November 2002
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Re: Why is a twinky better than a single cam
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Wed, 23 April 2003 08:57
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Google is a good tool, but I think you guy should be chuffed that somone is asking for you advice about somthing than just taking the word of any web site out there .
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Location:
Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Wed, 23 April 2003 12:08
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| draven wrote on Tue, 22 April 2003 23:22 |
if you ask on a forum and get a response others think is wrong, there's guaranteed to be an argument to follow, and usually the result is a lot of *very* helpful info, with more knowledgeable people weighing in to their side of the argument.
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EXACTLY
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Location:
Hornsby, Sydney
Registered:
October 2002
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Re: Why is a twinky better than a single cam
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Wed, 23 April 2003 23:37
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There is always one person who tells you to go get fucked and look it up on the web. this has happenned to me before and id say most of us. the web is good for looking up porn but for information you can never find what your looking for. also(not really with this thread ) the information that is sometimes requested changes so quickly if you get older unupdated web sites this infos useless. If you dont want to help someone ( and thets what this section is here for ) why are you looking here and dont waste your time typing WHY DIDNT YOU LOOK IT UP IN THE FIRST PLACE. the answer to this question is simple but if someone wants to know give them the desency to give a response.
Twin cams have less moving parts. single cams have cams rubbing on lifter rubbing on pushrods rubbing on rocker arm rubbing on vale stems. twin cams have cams rubbing on tappets pushing on valves. less movement over a smaller distance equals efficency/powewr
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Location:
Hornsby, Sydney
Registered:
October 2002
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Re: Why is a twinky better than a single cam
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Wed, 23 April 2003 23:44
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You can get cross flow and the same size valves in a single cam ( over head or pushrod) but i cant think of any push rod with 4v
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Location:
Hobart, Tas
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Thu, 24 April 2003 09:16
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Did I miss something road runner? Single cam does not imply pushrods... or are we comparing pushrods with OHC? I thought the topic was (overhead) single cam vs twin overhead cams.
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Location:
cambo
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Thu, 24 April 2003 09:29
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thats what i thought which is why i mentioned the angle of the valves. you can get a wider angle with twincam heads. also with the wider angle of the valves i believe there is a better 'scavenging' effect which is a good thing. i dont know if bill mentions that on his site if not look into a textbook about it cause its somewhat relevant.
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Location:
Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Thu, 24 April 2003 10:58
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Thanx for the positive response guys
and yes im talking about Overhead Cams
Thanx
Mani
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Location:
Hornsby, N.S.W
Registered:
September 2002
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Re: Why is a twinky better than a single cam
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Thu, 24 April 2003 11:28
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| manipulate wrote on Tue, 15 April 2003 17:43 |
Hey all
Just wondering why a Twin cam has better performance than a single cam
Logic suggest that with another cam shaft theres more precision with the timing of the valves ???
Ta
Mani
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FAR OUT MAN, look what you have started!!!! 
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Location:
Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Thu, 24 April 2003 11:35
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Only on toymods
but we all love it
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: Why is a twinky better than a single cam
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Thu, 24 April 2003 11:51
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'cos twinky heads look siiik bro
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Location:
Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Thu, 24 April 2003 12:08
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OK can we save the F**king around for the general discussion forum
all other forums such as tech should be SPAM free in my opinion
SPAM = General Discussion u bored pricks
Im up for a cruise tonite actually
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: Why is a twinky better than a single cam
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Thu, 24 April 2003 12:15
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sorry mani, dont get so uptight.. i was just mucking around... sheesh!
twincam heads allow for improved cross-flow and flow in general. The better the flow the more power the engine is able to produce more freely since it doesnt have to work so hard pushing the air/fuel/exhaust gasses around. Also better valve angles are obtained, further aiding flow and that scavenging stuff
And the most obvious is what everyone else has said - less moving parts = less friction, allows more power in the end result.
And since all the toyota twincam heads were made by yamaha, they didnt mess around with getting the formula right!!
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Location:
Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Thu, 24 April 2003 12:18
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Ahhk
thats much better
Thanx Carl
PS: Relax man
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: Why is a twinky better than a single cam
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Thu, 24 April 2003 12:29
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mani - stress is not in my diet
i am in a permanent relaxation....
and its Karl
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Location:
Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Fri, 25 April 2003 02:02
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No worries Carl
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Sat, 26 April 2003 07:47
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| EVOSTi wrote on Thu, 24 April 2003 19:29 |
thats what i thought which is why i mentioned the angle of the valves. you can get a wider angle with twincam heads. also with the wider angle of the valves i believe there is a better 'scavenging' effect which is a good thing. i dont know if bill mentions that on his site if not look into a textbook about it cause its somewhat relevant.
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Works the other way - Up to a point the narrower the valve angle the better the head works.
Eg -
Bad head - (relatively)
Good head - (relatively)
They make for a more efficient combustion chamber.
The F1 engines are around the 15° - 20° angle.
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Location:
cambo
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Sat, 26 April 2003 08:29
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is that so? i thought it was the other way. the GE's have wider angles to the FE's right? i thought that somewhat helped flow? i know other things such as port sizes and the like contribute but i thought wider angles were better. ohwell.
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Sat, 26 April 2003 09:18
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generally that gives them more power, not more economy.
the F1 cars can get away with the narrow angle, since they are PERFETLY tuned to get absolute maximum power out of the best possible combustion
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: Why is a twinky better than a single cam
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Sat, 26 April 2003 10:44
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i dont think i want to argue with Bill here...
except that he LOVES FWD
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Location:
Perth
Registered:
July 2002
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Re: Why is a twinky better than a single cam
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Sat, 26 April 2003 11:07
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| draven wrote on Sat, 26 April 2003 17:18 |
generally that gives them more power, not more economy.
the F1 cars can get away with the narrow angle, since they are PERFETLY tuned to get absolute maximum power out of the best possible combustion
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Efficiency = power = economy.
The closer valves are to the centre of the combustion chamber the more efficient the combustion process is, all else being equal.
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Sat, 26 April 2003 11:28
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power = economy?
there are a lot of sports car enthusiasts out there who would disagree.
think of tuning an engine for maximum economy ... you get nowhere near maximum power from this setup
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Location:
Sydney
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Sun, 27 April 2003 02:34
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Blown i understand what you;'re trying to say
Complete Combustion = Economy = Power...but thats a generalisation
its not ALWAYS this way
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Location:
Hornsby, Sydney
Registered:
October 2002
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Re: Why is a twinky better than a single cam
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Mon, 05 May 2003 09:47
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efficency to power to economy.
stefan wrote
Single cam does not imply pushrods... or are we comparing pushrods with OHC? I thought the topic was (overhead) single cam vs twin overhead cams.
a OHC still has to have rocker arm and shafts etc.
Unless it has both inlet and exhaust valves running parrallel as in wedge or flat faced heads.
this is no where near as good as cross flow as people have refered to before.
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Mon, 05 May 2003 10:15
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I know I'm more than slightly slow mentioning this, but I can think of 4 valve/pushrod combinations - about 10 years ago, an American company brought out bolt on replacement heads for the Chev small block with 32 valves, working off 16 pushrods. I've got a magazine article on it... somewhere...
Another interesting thing I thought I'd mention is has anyone taken a look at the replacement for the GENIII V8? It uses 2 camshafts, pushrods, and only 16 valves. Why? So they can get cam phasing...
Now's a good chance for those that like to bag out 'bogan' engines to speak up
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I supported Toymods
Location:
Central Coast
Registered:
May 2002
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Re: Why is a twinky better than a single cam
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Mon, 05 May 2003 23:50
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| mrshin wrote on Mon, 05 May 2003 20:15 |
Now's a good chance for those that like to bag out 'bogan' engines to speak up
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Under normal circumstances, I would. But it'll be hi-jacking the thread
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Toymods Board Member
Location:
Sydney
Registered:
September 2002
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Re: Why is a twinky better than a single cam
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Tue, 06 May 2003 00:43
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| Quote: |
find it amusing that you had to ask where bill sherwood's webpage is, and didn't even have the common sense to go looking for it yourself. of course, if you had done some research yourself in the first place, this thread would never exist
so in future, learn the below two websites before you go wasting people's time asking questions that have been answered many times before
www.howstuffworks.com
www.google.com
(warning : advanced subject matter keyword skills needed)
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Super Jamie.... Uncalled for!!!! Manipulate simply asked a question. Thats what these forums are for. Get off your high horse and relax!
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Location:
Madrid - Spain
Registered:
August 2002
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Re: Why is a twinky better than a single cam
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Tue, 06 May 2003 03:16
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There seems to be a bit of confusion about power, economy and complete combustion.
Complete combustion is great for emissions but it definitely does not equal power and economy.
The whole idea of running high octane fuel is to allow increased advance on spark timing. This means that the plug is ignited prior to the piston top dead centre (TDC) and fuel/air mixture begins to burn before TDC. This means that you are getting a sharper explosion, increasing your Brake Mean Effective Pressure (BMEP). Or to put it another way more power. This comes at the expense of incomplete combustion, or as far as the EPA are concerned, pollution.
As far as power and economy are concerned, the most economic way is to use as little power as possible to do the job. Economically this translates to as little fuel/dollars to do the job.
More power doesn't increase economy, it is just more power. Your engines ability to generate the required power near it's optimum BMEP is what makes the difference. Thats why a Corolla
gives great economy for trips around the burbs and a Soarer is better for towing a caravan. (Nothing implied about either car)
Well thats my rant anyway, I apologise for anyone who has actually read through this.
When it all comes down to it though, I prefer my car to be on the power side of the balance
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Location:
Hornsby, Sydney
Registered:
October 2002
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Re: Why is a twinky better than a single cam
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Tue, 06 May 2003 11:42
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Your motor counts as more efficent if it makes the same power as another motor for less fuel.
for the same amount of power to be made by a DOHC to a OHC or OHV the DOHC should in theory ( depending on design and purpose the motor was built for) use less fuel.
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Location:
Madrid - Spain
Registered:
August 2002
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Re: Why is a twinky better than a single cam
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Wed, 07 May 2003 00:11
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I think you mean that there is less losses with an OHC type arrangement than a side cam engine. As far as the difference between DOHC and SOHC losses are concerned, it depends on the valve actuation method. some DOHC engines use a rocker type set up which would give greater losses than an equivalent SOHC engine.
There is a lot more to engine efficiency than cam configuration.
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Location:
Perth
Registered:
July 2002
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Re: Why is a twinky better than a single cam
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Wed, 07 May 2003 09:21
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Valve train friction plays a part in efficiency, also important is valve train inertia.
The inertia of the valve train limits ability to rev as well as consuming power.
As far as an engine is concerned economy(efficiency) is determined by the torque/power produced for a given quantity of fuel.
ie a powerful engine can be economical because it maximises torque/power output for every gram of fuel used, a less powerful engine may use less fuel but can be less economical because it produces less torque/power for every gram of fuel used.
Economy is commonly used to just define fuel consumption, this is not technically correct.
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I supported Toymods
Location:
Berowra-Sydney
Registered:
July 2002
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Re: Why is a twinky better than a single cam
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Wed, 07 May 2003 12:30
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SOHC= Single Over Head Cam
DOHC= Double Over Head Cam,
friction has no part in why DOHC is better then SOHC, come on guys tell me how much friction there is? crap all, if your so worried about the extra "friction" of a SOHC then why don't you also think of all that extra mass of a DOHC that has to be turned around by the engine still having the same friction if not a DOHC would have more friction,
DOHC isn't exactly "BETTER" than a SOHC its just a DOHC is easier to adjust the exhaust valves and intake valves for best performance, so rather then having to re-ground a new cam every time you just adjust the angle of one of the two cams to obtain best performance, but thats just an easier way to do it you can still get the same performance from a SOHC it just requires more money and time in development,
The main reason a DOHC is better then a SOHC is the fact that DOHC are usually cross flow heads "where intake is on one side and exhaust on the other" where SOHC were usually both on the same side like an 18-RC vs a 18-RG "for the celica guys to understand"
also DOHC tend to ev higher then a SOHC, the DOHC can rev higher and longer then a SOHC
DOHC isn't better or worse then a SOHC its just all depends in the complete design of the engine but a general rule is that DOHC is a cross flow head and can rev higher "usually due to more precise valve timing"
so if you want an engine so you can play around with valve timing ect get a DOHC, or if your looking at getting an old style engine "for example carby" get a DOHC,
but these days SOHC doesn't have a huge diff over a DOHC, its just having two cams in there is a cheaper and easier way of fine tuning the engine.
like if you take an 18rc and rg engine and put lumpier aftermarket cams in you will get a bigger hp increase in the rc "SOHC" because the new cam has been tested and grinded to have to best valve timing where the RG "DOHC" already has spot on valve timing. why? because it was easier to tune the valve timing on a DOHC cam then a SOHC,
my car is a SOHC it has a cross flow head and loves reving high and can sit at 8,500rpm all day long with no problem,
so yeah any of that make sense?
i'm not very good at explaining things i understand something but i'm not very good at explaining it to someone else,
but old engines as a general rule DOHC is better
modern engines there isn't much difference between DOHC and SOHC
anyone want to argue my point? 
also lower octane fuel is more explosive then high octane,
just high octane is more stable "doesn't pre ignite" there for you can advance the ignition timing more which increases power.
also peak power doesn't = economy, in theory yes it should be right but we don't live in a perfect world, just look out our engine more then 50% of the energy is lost as heat!!!!
usually with a standard car you can increase power and increase economy but when your foot is into it then economy is out of the window, only time peak power and economy can be obtained is at one set cruiseing speed, not when moving up and down through the rev range,
if you tune your car for the most power possible then look at your fuel consumption as it will go straight out the window, look at a pure bred race car thats only used for racing on the track, it chews through the fuel like nothing else and also wasts alot and spit it out the back, you think the flames coming out of the V8 supercars is a sign of good economy? NOPE but they sure are tuned for peak power.
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: Why is a twinky better than a single cam
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Wed, 07 May 2003 13:24
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aww common martin, you spoiled my fun 
i thought those flames on V8 supercars were small rockets to make them go faster...
*sorry just joking guys!!*
seriously. Most of what has been said above has gone over my head. It seems the most common point is that twincam has the advantage over singlecams because of costs and inherent design properties.....
.... but then again i could be wrong
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Location:
Madrid - Spain
Registered:
August 2002
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Re: Why is a twinky better than a single cam
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Thu, 08 May 2003 00:20
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Not really, manufacturers are not interested in tuneability of an engine, only manufacturing costs.
Cam shafts are not cheep to manufacture as they require casting, machining and hardening.
The main benefit of a twin cam head is in most cases it removes the rocker arms, removing some inertia from the valve system, allowing the engine to rev a bit harder without reducing reliability. Hence improves power through increased RPM (obviously cam/fuel is different to take advantage of the higher RPM).
A twin cam engine also gives the designers more freedom with valve angles (angle between exhaust and inlet valves). This can improve combustion chamber design.
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Location:
Melbourne.
Registered:
June 2002
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Re: Why is a twinky better than a single cam
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Thu, 08 May 2003 06:23
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TwinCam (DOHC) heads still have Rocker Arms dude.
My friend actually broke one of them from his SR20DET. Funny thing is that he is very into backyard mechanics, and wanted to pry back the valve spring using large screwdrivers! LOL
ANd how he snapped his cambelt (chain) is beyond me!!!
Lucky the Sr20 has a non interfering head, and didnt smash a piston!
Anyways, multivalve heads also tend to have an effect on torque produced, i mean looking at pushrod/OHC large 3 valve heads, you can see how torque is made much lower with similar capacity engines than their multivalve counterparts. I know that bore and stroke have a lot to do with torque, but im still thinking that smaller multivavle heads were created to fit a larger valve surface in a smaller jap 4 cylinders, which releid on being compact.
I mean u could fit 2 large heavy inlet valves and one exhaust valve in a 4age, or you could fit lighter, more compact 2xexhaust valves and 2xinlet valves that make up the same area as that fat ass one.
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Location:
Hornsby, Sydney
Registered:
October 2002
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Re: Why is a twinky better than a single cam
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Thu, 08 May 2003 07:34
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GIN51E said (dont know how to quote people)
i'm not very good at explaining things i understand something but i'm not very good at explaining it to someone else,
but old engines as a general rule DOHC is better
modern engines there isn't much difference between DOHC and SOHC
I'll agree strongly with this. I think i could explain my points of veiw easy in person on this topic.
LowRollaBoy. the earlier model toyota DOHC such as 2TGs (im guessing mani is questioning these owning a TA22) dont have rocker arms. they run directly on the tapet to the valve.
GIN51E's last comment on may post said about DOHC to SOHC.
if you look at the 2TG DOHC to the 2T OHV engine there isnt alot of difference in the power any way (some but not massive)
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