Playing with cam timing

[jevansio]

I've read alot of the cam timing threads, & they all come back with the same result that straight up is the best all round for low down grunt & top end power.

 

But if I was prepared to sacrifice a bit low down to gain at the top what would you do adv/ret on in/ex?

 

Also has anyone done a scientific test of the gains/losses to be had (dyno graph style) for various settings (say all combos of -5, 0, +5 giving 9 settings), and exactly how many possible horses are we talking here on say a 600bhp Supra?

[jevansio]

Anyone?

[shima60]

Personally i say fire it on a dyno and see what is best for your car

[JamieP]

I had Lee degree my engine like this for my cam specs (watch from 4:30) He had a engine builder he knows help him set it up i think.

 

http://www.youtube.com/watch?v=_MsqA-C3vGI

[pedrosixfour]

Super Trick!

[jevansio]

There's a great sticky on SF detailing the same process,

 

http://www.supraforums.com/forum/showthread.php?t=474428&highlight=cam+timing

 

I took the shortcut on mine & installed them straight up.

 

Actually reading it there's a guy who has tried messing with the timing but doesn't give any hard numbers on what the gains were.

 

I've degreed about a dozen bone stock motor Supras with HKS cams and found all of them were spot on without needed adjustment of the gears. I think HKS has a rep for quality control like non other. But, if you have the slightest doubt, you might as well get it done. If it's off by 1 degree, you may not even notice the different at WOT, while part throttle may give you varying degree of success. I've toyed with changing cam gear values from +/- 3 degrees each cam on the dyno and all that did was shift my torque curve, ever so slightly, as well as change the spool characteristics, again, every so slightly.

 

Might just have to do it for myself, TBH I'm not even bothered about getting actual dyno numbers, I just want to know where it accelerates best which I think I can log direct on the AEM on the street (which is a better real life test anyway)

[Tricky-Ricky]

I had my exhaust cam advanced by about 10deg never bothered to be precise, but although i thought it made spool up slower i could still make 1.3 bar by 3,800RPM, i do think that it made a big difference to my EGTs never saw more than 850C.

And as for power it made over 530BHP and nearly as much torque

[jevansio]

Cheers Ricky, I think I'm just going to have to take some time out & grab some data for myself. Think I'll wait for my 272 ex cam to turn up first as there's no point doing the tests on cams that are just going to come out. I'll try & be methodical & post the results here

[jevansio]

I just rewatched that video Jamie. I'm assuming he initially started with the cams straight up? But he got 8 deg ATDC and he was after 8 deg BTDC, hell that's 16 deg out, may pulleys don't even have that much adjustment in them?? Surely they can't have been that far out?

[jevansio]

Another question, when you guys are talking I've advanced my intake cam timing 5 degrees, are you talking 5 degrees of actual cam gear rotation, or 5 degrees of crank rotation?

Edited June 5, 2010 by jevansio (see edit history)

[Ian C]

Crank rotation.

 

Do let us know how you get on

[jevansio]

Crank rotation.

 

Do let us know how you get on

Ah right, I just checked my gears and the +/- 10 deg on there is actual cam gear rotation which gives +/- 20 deg of crank rotation

 

Will do, as I say I won;t be on a dyno, but I can measure acceleration at various rpms via the AEM/RLPB which is indeed what we are effectively looking for when we tune our cars

Edited June 5, 2010 by jevansio (see edit history)

[AndyT]

You've opened a can here Jay. I look at the standard spec of my engines and get the advance / retard on crank position and just think thank f;;k the club doesn't get this detailed.

Wrong. Cheers dude.