Adjusting adjustable cam gears.. 130-95?

[TurboRA28]

Hi all, I thought it might be good to start a thread in regards to adjusting cam timing.

I've done some searching on the old forums and yes it has been discussed, but didn't find anything in a real technical nature.

This is an interesting read, most of it is a plug for AEM adjustable gears, but once you get past that there is some real world dyno results - http://www.turbomagazine.com/insidet...technology01a/

The most gain seemed to be from advancing the inlet cam slightly. Though it seems the tests were minimal. Like there was no test advancing the inlet cam and retarding the exhaust cam.

I've got quite short runners on the RWD 3S manifold I designed, and after reading that article it seems that short runners can benefit from advancing the inlet cam and closing the valve earlier.

So yeah it would be interesting to get some discussions happening on this.
Cheers
Joel

[Ben Wilson]

Once again, Bill Sherwood has some stuff on his site about it...

[Celica RA45]

if your cams are std ,leave them where they are
if you are getting some hard faced then you will have to dial them in ,because most of them will be ground offset to the std profile
when you do advance a cam it will start early and finish early in the rev range
example std cam starts at 3500 and goes to 7000rpm
you advance it cam starts 3000 and goes to 6500 rpm
so you gain some and loose at the top end

[Jonny Rochester]

This is my favorite subject, as I don't have a turbo.

First you have to wash your brain, forget all the american forums saying "oh you have to advance the exhaust" or whatever. You are shooting in the dark if you just put adjustable gears on, then "adjust" it a bit either way by sight. (Feel free to experiment, but please don't get on a forum and say it worked well a bit this way or that, because there is no way another can replicate the results and its a waste of time).

With new cams or cam gears, you need to start again from square one in timing the motor. To do it properly, you need a degree wheel on the crank pully, and a dial gauge setup to detect valve movement. Find a page that describes timing a motor, or "degreeing the cam", with a degree wheel.

Now, once you know where everything is with stuff written down, you can tell people your exact specs if it works well and people can copy.

After reading some stuff, and trying a few things, generaly... Stock standard motors have cam durations of about 240 degrees, with the maximum lift, or cam lope center timed at about 110 degrees before or after TDC (both intake and exhaust).

And for race use (non turbo at least) you will have both cams timed at around 100 degrees between centers, with cam duration closser to 300 degrees.

Even with big cams (300-305 degrees) you can get a very mild engine just by timing them to 110 degrees, a perky very usable mid to top end power timed at 105 degrees, and a lumpy screamer timed at 100 degrees. But everytime to adjust this, you need to change carby/computer settings to make it work.

But don't listen to me, my reputation only at... 10

[Jonny Rochester]

CelicaRA45: most of us have twin cam motors now! So you can change each cam seperately. For the backyarder (and myself) if you want more high rpm power at the sacrifice of a good idle, you need to advance the intake cam and retard the exhaust cam.

On a 2T-G for example, the two notches on the top of the cams will end up tilted over a bit facing each other.

[Cameron_Datto]

My feeling is if your not getting much of a gain from in the top end power then its not your cams causing the problem .. more like your turbo is maxed out in its flow efficiency.. you can`t make more power if your turbo cant flow any more air ..
In the past in general ,i have gained more driveabiliy by changing the Exhaust cam timming ..when the cams are std .. I find what works good as a general rule is the following lobe centre angles on most street cams .. Inlet cam 110deg + or - 2 deg ... Exhaust cam 114 deg + or - 2 deg ..
i never dynod the cam angle changes ,, but hillclimbed the car with various cam changes to make the car as driveable and quick as i could get it .. these days i tend to use lobe center angles to set up cams in turbo engines as my starting point ...Btw iam not chassing Max hp in the setup .. but the broadest power band i can get ..

WHAT I HAVE SAID ONLY RELATES TO TURBO ENGINES ..

[Celica RA45]

yeah not to use to 2tg .as im only running a vvti 3sge that moves the cams all over the place and thats just the same as what you are doing except mine moves both inlet and exhaust
jonny i think im a bit older than you 2 ,as i used to have a TE27 levin with a grp A 2tg in it the cams we had then was something along 300 degress advertised at 50 thou was 260 and had about 11.5 mm lift these were a TTE rally grind and we set them up as we were told but moved exhaust back and only played with the inlet which made most of the difference
even with vvti we still only mainly move the inlet and only move exhaust for start up

[JustCallMeOrlando]

Okay. Say I had a turbo application. I'm running 1GGE cams in a 1GGTE with a factory inlet manifold, what would be an ideal way to begin?

[Jonny Rochester]

I would say the first thing to do, playing with any of this, would be to get a degree wheel, turn the motor over without adjusting anything, and just record your base standard settings. See when the valve opens then closes, then use that to work out your lobe center angles and duration.

Only after doing that, you can compare your setup to a dozen other setups.

As CelicaRA45 says, fine tuning the intake cam will be more critical on a non-turbo car. I think with turbo the timing of the exhuast cam will matter more.

For non-turbo, look at the TRD Corolla Bible. It shows exact cam specs for both Group A, race, rally, and N2 setups.

[takai]

Any suggestions on where to get the aforementioned degree wheel? The one i have is pretty old, cruddy and scratched up. The only place ive been able to find sofar which sells them wants $70 for an ARP one :O

[Celica RA45]

chris just use a 360 degree protractor and blue tack it to your harmonic balancer ,i think they cost 1.50 but you will have to cut the center bar out ,that way you can still rotate the motor over .
also i use lifter rise at tdc when setting my cams ,even for vvti same set up applies unless its a std motor

[takai]

Ah yeah, 360* protractor, i had never thought about that option. Really not hugely expensive either. Thanks for that man.
I just use my dial gauge which i have for machinework when i do cam timing.

[TurboRA28]

All very interesting read sounds like I should be getting a dial guage and protractor!

I mainly fitted adjustable cam gears during the build because the head had to be line bored as the cam bearing caps were not matched to the head. The engine machinist thought this may slightly change the cam timing and adjustable gears would be a good idea to fine tune it.

I'm finding the engine lacking power down low for a 2ltr/small turbo engine. But once the revs get up above 5k it starts pulling like crazy. So I am thinking this could be due to incorrect cam timing. Maybe I need to move the power band down in the RPM range.

So that would be done by advancing the inlet cam yeah?

[oldcorollas]

save this to your PC and print out...

http://www.tavia.com/free_degree_wheel.html


as the splurge says, 7"wheel, print out at high dpi etc...

Tavia = good

[GTI16V]

Repco sell degree wheels fairly cheaply about $40 trade