Info wanted on ajustable cam gears and cams

[maxhag]

hey guys,

I dont know much at all about aftermarket cams and ajustable cam gears and i just wanted to get some info.

At this stage, i am just building my knowledge and not applying to a motor (yet)....

First of all, What do Ajustable Cam gears do? (i know many will laugh, i dont care, i want to know this stuff) ;)
What and where do you benefit from them? When do you need them?
Do they eliminate the need for aftermarket cams?

any info is greatly appriciated.....


Also, Aftermarket cams. At what point do you need them? If wanting more torque? My 4AGTE could do with some more torque down low, would cams help that? What do i look for when purchasing? I have noticed alot on the market, What do other people use?

thanks

J Riftin

[slide86]

baically you use adjustable cam gears to fine tune the cams.

you can adjust when the cams "come on" in relation to each other and crankshaft position.

they can be used them on stock cams aswell as aftermarket ones.

you have to be careful as to what cams to use in a forced induction application, too much duration will cause problems, as the boosted air goes straight out the exhaust cause the valves are open too long.

i am currently looking into getting some higher lift cams, to open the valve further. this should increase the amount of air going into the cylinder but with the same or similar duratuion time. ie the valve is open for the same length of time. it just opens further....if you can understand that :)
probably something round the 260 degree and 8.5mm lift

you will need to remember also that when upgrading cams its a good idea to get decent quality valve springs.....coil bind is very very ugly

[maxhag]

<div class='quotetop'>QUOTE (slide86 @ Jan 9 2008, 01:14 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=465375)</div>
i am currently looking into getting some higher lift cams, to open the valve further. this should increase the amount of air going into the cylinder but with the same or similar duratuion time. ie the valve is open for the same length of time. it just opens further....if you can understand that :)
probably something round the 260 degree and 8.5mm lift[/b]


Yeah , i can easily understand that...

If you did what you have said above, where would you notice the effect in performance? (ie more air in cyl but same duration?)

thanks

[slide86]

more boost in cyl + more fuel = bigger bang = :D

[86adz]

i think he's wanting to know at what rev range will the increase in power from that type of modifcation be most noticable or is it just an all round improvment in the power curve?

[johl]

im no pro but by the sounds of the type of cam gears he was going to use it would be an all round improvement as the cylinder is open for the same amount of time and nothing really has changed. thats my assumption anyway till someone proves me wrong?

[maxhag]

<div class='quotetop'>QUOTE (86adz @ Jan 9 2008, 10:15 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=465446)</div>
i think he's wanting to know at what rev range will the increase in power from that type of modifcation be most noticable or is it just an all round improvment in the power curve?[/b]


correct

[skit]

Guys,

From what I have read, it would be worthwhile if you all read some textbooks on engine theory. I am not flaming anyone - everyone has to learn from somewhere, but what is written in this thread sounds like a very basic interpretation of heresay.

Maxhag, rather than asking a broad question such as yours on a forum, you may be better consulting known resources (such as in textbooks). On any forum you will get a spectrum of answers ranging from B.S. to facts, and everything in between. There is plenty written on this. Two such books that springs to mind are "Four Stroke Performance Tuning" and "Forced Induction Performance Tuning" both by A. Graham Bell. While different people have different theories on tuning, the basic principles are all covered in such books. There are a million others like these too.

For future reference. Cams do not "come on" and "off". I think someone is confused with the term "coming 'on cam'" which is used to describe when an engine enters the phase where it begins to work most efficiently (i.e. pumps air most efficiently). On a lightly tuned engine this is usually not noticable. The opposite can apply for hard tuned motors.

Adjustable cam gears allow you to change the camshaft timing, relative to the crank, and in the case of a 4a-ge, relative to the opposite camshaft. There are different "types" of cam gears, but the only difference is how accurately they adjust. The function is always the same.

Perhaps the earlier reference to cams coming "on" was describing a valve being lifted off its seat. Of course, the transition of valve closed > open is not a matter of on/off. This is dependant on other factors such as cam lobe angle (i.e. how fast the valve is accelerated off the seat and decelerated to point of maximum lift).

Keeping cam duration constant but changing cam timing will still change the characteristics of the engine. Advancing/retarding the valve opening angle (relative to the camshaft) has pronounced effects, as it is relative to where the piston is, and therefore cylinder pressure is affected. Changing the timing of one cam relative to the other changes the "overlap". Someone refered to too much duration being a problem due to lost charge out the exhaust valve, and therefore lost cylinder pressure. To some extent this is a good thing (referred to as overlap breathing) as it helps flush the combustion chamber of old "burnt charge" from the previous cycle which can linger. This is more of a concern for atmo tuning than turbo, as far as I am aware.

Any engine will only work most efficiently over a certain rpm range. We band aid this using technology such as variable ignition and cam timing to try and maximise the efficiency over the total rpm range. Some engines even have adjustable compression ratios. What you gain somewhere you will usually lose somewhere else, all performance is a compromise.

Anyhow, I don't proclaim to be an expert at all, but there is much that can be understood by turning a page.

[maxhag]

All so very true skit....... They are some wise words.... Obviously i do realise that peoples opinions can either be true, or bullshit...... But, you never know when you might learn something new...

I WILL do some reading, are those books you mentioned Australian? But i just thought that someone else on this forums would be using this equipment and therefore know what it's doing to their engine, and give me a few tips etc.....

thanks

J Riftin

[skit]

<div class='quotetop'>QUOTE (Maxhag @ Jan 9 2008, 10:02 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=465842)</div>
But, you never know when you might learn something new...

I WILL do some reading, are those books you mentioned Australian?
thanks

J Riftin[/b]

The books are written by an Australian fellow, from Maitland I believe. Thinking back, there is a good chance I bought those books from the Pitstop bookshop online. I really can't recall, it was a long time ago. He also has a good two-stroke book too, if you have even more time on your hands!

I agree with you, you can learn alot here - but it helps to know who is providing the answers. There are some people here with a wealth of knowledge & practical experience to back it up. The more specific your Qn's are, the better your answers will be :)

Good luck.

[slide86]

i meant coming on in the sense that you have stated. i know its not exactly the correct term, sometimes i forget that im not at work and others dont understand what i mean......

im pretty sure i read a few books in the 4 years that i was at trade school and the 100 or so engines that i built at work would help. not flaming anyone, but like i said, i forget that im not always talking to other mechanics who know when this is doing that, and this causes that, kinda thing.....

[Jonny Rochester]

For a non-turbo motor, cams of longer duration is the fundamental key to getting more power. Standard cams are around 240 degrees duration, in a hot N/A motor they are closer to 300 degrees. The timing is critical, so adjustable cam gears are used to put the cams exactly where you want them. 1 tooth of the timing belt is not nearly accurate enough.

For a turbo motor, the standard cams are fairly good. You may want adjustable cam gears only to get the best setting. Without heaps of your own experience, it maybe worth noting other peoples setups. If a similar turbo motor to yours is making good power with cams of similar duration and of known lobe centre timing, you could set your motor up with adjustabe cam gears and the same lobe centre settings.

[SpotterOne]

<div class='quotetop'>QUOTE (Maxhag @ Jan 9 2008, 01:03 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=465371)</div>
hey guys,

I dont know much at all about aftermarket cams and ajustable cam gears and i just wanted to get some info.

At this stage, i am just building my knowledge and not applying to a motor (yet)....

First of all, What do Ajustable Cam gears do? (i know many will laugh, i dont care, i want to know this stuff) ;)
What and where do you benefit from them? When do you need them?
Do they eliminate the need for aftermarket cams?

any info is greatly appriciated.....


Also, Aftermarket cams. At what point do you need them? If wanting more torque? My 4AGTE could do with some more torque down low, would cams help that? What do i look for when purchasing? I have noticed alot on the market, What do other people use?

thanks

J Riftin[/b]

Adjustable cam gears allow you to put the cams in exactly the right spot as others on here have said. Its generally not an issue for standard cams, because manufacturing tolerances will only change the cam timing by a degree or 2, but if both of them are out by a couple of degrees, there COULD be some ground to be made back up. What they might be able to provide for you is a little bit of "torque tuning" whereby you adjust your cams relative to each other (and TDC) so that the cams open and close at slightly different times, which may change the torque characteristics of your engine. Is it worth putting adjustable cam gears on standard cams? I wouldn't, because its not quite as simple as "throwing them on". Getting someone to time your cams again may cost you as much as the gears - especially with the engine in the car.

On aftermarket cams, they try, but sometimes fail when it comes to where the cam sits in the grinder on the initial setup when building/grinding a camshaft billet. What can happen is the the locating pins on the front of the cam wont line up exactly with the stock position on stock cam gears, and you wind up with odd cam timings. Again, this is usually only a few degrees, but a few degrees on a few degrees makes a big difference.

What the cam gears allow you to do in this instance is work out EXACTLY where the high point on the lobe is, and put that in the most ideal place in the cycle. The couple of degrees makes a fair bit of difference, so its best to get someone who has done a few to time your cams for you. Dont even think for a second that you can "skip a tooth" on your cambelt to advance/retard a cam. 1 tooth on a 4AGE is 20 degrees!!!

Most aftermarket cams move your torque curve further up the rev range. They probably aren't the best way of getting more torque. They certainly are effective for liberating power at the expense of torque, but thats not what you asked. Some torque can be gained back by effective design of exhaust manifolds and secondaries, as well as good tuning, but that is another story for another topic. There is a point though (regarding cam lift and duration), where you will actually LOSE torque at the expense of power. There are theories out there, but from personal experience it is in the region of anything over 8mm lift and 272 degrees duration. I currently have cams with these specs in my car at the moment, but thanks to a number of other mods I did in conjunction with the cams, I have a big, fat torque curve that makes my car very easy to drive very fast.

The other thing you need to think about is that you want more torque down low. Why? If you want to go fast, don't you get into it a bit and get some revs going? I know that on a track my car never revs below 4k, fat torque curve or not!

Hope some of that helps someone!

Leo

[ToySprinta]

Hey man, I've been playing with cams. Tried 282s with my GTE made great power, but laggy as fuck. playing with the cam adjustment we brought the boost on earlier (4200 instead of 5500) at the expense of top end power. To get the cam settings right, we played on the dyno for about 2 hours to get the best out of my setup...

[ToySprinta]

Also got a set of bigport cams for a cheap easy upgrade if you want them :)

[maxhag]

GTE? Steve, Have i not seen this car?

What are the specs of bigport and smallport cams?

[denialmark]

toysprinta- you say put in bigport cams. (mines a small port gze turbo)
im guessing the cams can only come from a GZE bigport or can GE be used?
whats invovled in putting them in? originals out-new ones in-driveaway. put simply

[skit]

<div class='quotetop'>QUOTE (NFI @ Jan 12 2008, 06:24 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=467480)</div>
toysprinta- you say put in bigport cams. (mines a small port gze turbo)
im guessing the cams can only come from a GZE bigport or can GE be used?
whats invovled in putting them in? originals out-new ones in-driveaway. put simply[/b]

Guys,

Download the 4a-ge service manual to give you an idea on how to change cams. Otherwise searching over the web you should find a "how to do" page with some pics. Such pages are not always the "proper" way to go about things though, so common sense prevails. Yes the job can be done at home, but you should check your valve clearances while you do so. The steps are in the manual. It's not quite like changing a starter motor in your driveway though.

Oh, and I believe all 16v cams are interchangeable.

[ToySprinta]

Yup, all 16v cams are interchangable. If you are mechanically minded enough to swap the cams at home, it is simple plug n play :)
Had an interesting combo of 282 intake and standard bigport exhaust for a while. Brounght boost on real early, but fell over at high revs...

Stock smallport ge/gze and bigport GZE cams
Dur: 232
Lift: 7.1mm

NA Bigport
Dur: 240
Lift: 7.56mm

[Jonny Rochester]

If you are going to have mismatched cams,
you are better to have the longer duration cam as the inlet for N/A.
You are better to have the longer duration cam as the exhaust for turbo.

[ToySprinta]

Lol, yeah i know. I managed to destroy the exhaust cam, and was running the smaller one till i got a new one.
PLanning on trying out 260 inlet and 270 exhaust...

[denialmark]

thanks fellas, exactly what i wanted to know.