Adjustable Cam Sprockets - what's the deal?

[Chris Corolla S]

What do adjustable cam sprockets such as this:http://www.obxracingsports.com/perfo...18&subCat2ID=1 do? I understand the application of light-weight accesory pulleys and crank pulleys like these:http://www.obxracingsports.com/perfo...18&subCat2ID=1 and this: http://www.obxracingsports.com/perfo...18&subCat2ID=3 as reducing parasitic power-loss, is this the same idea as the cam sproket? Or is it suposed to adjust the timing (advance) for power gain? And if so would it work on a VVT-i engine? Is anyone running products like these?

Thanks,
Chris

[wunderboy]

adjustable cam gears let you advance, or retard your timing, based on your setup. You can adjust the timing with stock gears, but you have to take off the timing belt to do it, which doesnt make for friendly tuning.

[rezzle]

Adjustable cam sprokets allow to adjust (fine tune) the valve timing *not* the ignition timing and valve overlap.

You just had to make me post a link to this page didn't you ...

don't fall asleep.

http://www.twelve100.com/faq%20and%2...haft_story.htm

[Chris Corolla S]

Well I read the link but it did not answer one of my questions:

O.K. so it allows you to adjust the valve timing? Doesn't that go hand-in-hand with ignition timing though? If you change the lift durtation or what have you, wouldn't you have to adjust the ignition timing as well?

Anyway I have Intelligent Variable Valve Timing so would this mod work since the ECU controlls valve timing? Plus my ignition timing is not mechanically adjustable (no dizzy, so plug wires, no coil), it is controlled by the ECU directly so wouldn't these things interfere with modding the valve and ignition timing to take advantage of say i/h/e...?

[rezzle]

First know that with VVTI you already have adjustable valve timing that is being controlled by your ECU and chances are you will be hardpressed to do better.

EDIT: The timing on between the intake and exhaust cams varys as much as 60!!!! degrees

On the track or on the rocks most performance engines use non stock ecu's in these cases the VVT is switched based on RPM or boost. Note i said VVT not VVTi because VVTI is not single stage. Performance VVTI ECU's do exist but they are very expensive, think WRC type vehicles.

I don't think that on a stock engine there is much to be gained by playing with valve timing. Bigger gains could be had by switching to cams with a more favourable lift and duration for the type of driving you are looking for. Don't forget that changing cams to gain power at the high end almost always means losing some of the streetable qualities of the engine.


Not only that but with these newer more complex valve systems (Toyota even has a special bolts on the thing so it can't be disassembled easily without 'their' tool) Mating camshafts can be rather troublesome.

This link discusses variable valve technology discussing its past present and what we will be seeing within the next few years.

http://www.mr2sc.com/websites/articles/vvt.htm

[rezzle]

Oh ...
forgot to mention.

The ignition timing and valve timing are still calculated separately, performance engines normally use a crank triggered ignition device. In your case I honestly have no idea how the spark is fired (cam triggered event or crank). I haven't bothered to read up on the newer Toyota's and I probably won't untill the Echo needs some serious work.

[Chris Corolla S]

"First know that with VVTI you already have adjustable valve timing that is being controlled by your ECU and chances are you will be hardpressed to do better." Yes this is what I was getting at, I figured as much.

As for how the ECU advances the timing:
http://www.autoshop101.com/forms/h40.pdf

[boroEF]

vvti only controls the intake cam. if u got an adjustable cam sprocket u can use it on the exhaust cam.
should help u get some more power...wont do much tho unless u get some real cams

[Chris Corolla S]

Haha well it's not like I have 3 or four cams to choose from like a 4A-GE, there is no such things as cams for a 1ZZ-FE.

[boroEF]

Originally posted by Chris Corolla S
Haha well it's not like I have 3 or four cams to choose from like a 4A-GE, there is no such things as cams for a 1ZZ-FE.

errr i'm sure web has regrinds of it.

they have regrinds of everything!

[Chris Corolla S]

regrinds=

Anyway it doesn't matter. I'm not trying to build my 1ZZ to drag or anything I know extracting horsepower from this plant is a fruitless endeavor beyond a certain point. I'm gonna get a TRD quick shifter for my birthday, that'l make me happy

[boroEF]

Originally posted by Chris Corolla S
regrinds=

what's wrong with regrinds? u do know that back in the day, they didnt have billet cams right? everyone was using regrinds.

myths about them fucking up ur valvetrain and blablabla arent true. i know ppl to run regrinds on their ef's and track it etc etc with no issues whatsoever...on stock valvetrain!

[Chris Corolla S]

Fine then you go get your cams re-ground, but read that link that Rezzle posted on 4A-GE cams first...

[boroEF]

Originally posted by Chris Corolla S
Fine then you go get your cams re-ground, but read that link that Rezzle posted on 4A-GE cams first...

who needs regrinds when u can get 20v :p

and remember, i'm boro...if i were to get cams, i'd go regrinds.
i didnt look at his links yet..but just from ppl's experiences it has been okay...at least on honda motors(they dont use shims and buckets)

[Chris Corolla S]

Shuddup about hondas already How the hell does that apply to anything? No one here has a damm honda... Your 4A-GE is not a honda motor o.k.?!
Bad Boro! No V-Tech!