SeanR

Mark did not invent this so it will not work like everyone thinks it does.

Jim Morton

Sean: There is another variant that can take this topic to the "abyss"... that is that if you have aftermarket or reground cams, you need to verify the lobe center angles with a degree wheel to "calibrate" this tool before you know the "zero" for the installed cams. Once "calibrated", it's a great tool for tuning !

SeanR

I miss you posting, you really should come back more often.

mark kibort

awesome! I remember we used to double check my work, and it all worked out as expected with some variance that we were able to contrubute to the cams or the heads being shaved. i forget.

Gregory would be very happy to hear we took a look at the timing. ive checked all i can and im not about to pull cam covers on any car but mine and maybe yours!

mark kibort

smart guy, with shaved heads things get a little off. we found this out when i was doing the tests on the holbert engine. ALSO, if you remember Ken and I were in a heated battle for how i was tesing the cam timing, as i repeated my process, i took a short cut on the starting position of the crank, rather than the full two revolutions, i started it at 2 revs yes, but didnt keep the dial indicator connected as it was getting in the way on rotation. so, i was getting a pre-moved value on the lifters. fortunately, my values were never that off, because i had always used that technique and matched the values when installing or adjusting the cams. in the end, the porken tool was pretty accurate and we ended up using the cams at the same 8 degrees retarded setting for the intake cam. (cold)

SeanR

No need for a diatribe, we are all just waiting patiently for your approval so we can either buy this or not.

PorKen

You may get a small improvement with just cam timing up to a few degrees retard, but to really get power out of it, my results appear to show that you have to retard a lot more and crank up the ignition advance at the same time, as previously noted.

With more retard, there is less dynamic compression, so more ignition advance can be used w/o knocking.

Doing this leaned out the AFR for me, either by burning more, or by being less efficient (more fuel just passing through unburned), so I also had to add more fuel.

The combination of more fuel, and more ignition advance more than makes up for the loss in compression, at least with S3 cams.

I really didn't lose much torque at all, but gained a lot of HP, and it really loves to stay rev'ed. It doesn't 'feel' as though it has much power down low, but it has basically the same HP at lower rpms - it just has so much more up high, so I tend to keep the revs high. 4000 rpm feels effortless.

Another thing I did was disable injector cutoff, which helps keep the engine at high revs, even if you let off the throttle for a moment. It also makes that racy, snap, crackle, pop on decel.

Interesting.

Put in a PKT, yet, BTW?

You might get better throttle response, but you'll get more knocking at high rpm, so you'll end up having to take out ignition timing, and lose power.

From my results I'd postulate (pontificate) that you'll probably be better off retarding the cams, and adding a bunch of ignition advance down low, instead.

Do you have a knock sensor installed?

PorKen

Another tidbit I forget to mention (it has been mentioned by others, too, I believe).

Advancing makes the exhaust note quieter.
Advancing increases engine braking.
Advancing raises the idle speed.

Retard makes the exhaust note louder, sometimes unpleasantly so.
Retard decreases engine braking.
Retard lowers the idle speed.


My '86.5 auto, with +3° advance is unnaturally quiet with X-pipe, dual '86.5 (=GTS) resonators, and modified pumpkin, even at full throttle.


If I'm thinking about this correctly, another way to do -8° retard, or more, would be to rotate the engine CW to the 1|0 mark on the balancer after T|0, then use the 32V'r to advance to the desired setting, EG. -10° + 2° = -8°. (0° on the 32V'r becomes -10°.)

If you want to go big, 10°+, and there is not enough slot to allow this, you can restring the belt over the cam gears one tooth (7.5°) retard, then use the 1|0 as 'zero'.


First, I'm going to see how much more I can get in the slot on my '86.5 5-speed, then maybe restring.

mark kibort

yes sean, buy it . its got my approval.

SeanR

Thanks

Glad I spent my munee's on it a few years ago, It's a great tool.

mark kibort

I would have only used it, if it wasnt for the fact that i had mystery cams and wanted to really know what i had with the original settings

PorKen

Setting it to 1|0 worked great!

The 1-4 max'ed out at -16°. Tough to turn the top screw, so I set the 1-4 to -14° cold, for a target -12° for both sides hot.

I bumped up the ignition timing a bit more, but haven't had a chance to log it for AFR, yet. It has not lost power, at least...in fact it keeps pulling all the way to 6700 rpm.

fbarnhill

Ken, what kind of results do you predict from this on the street? Is this something I should be looking at on my setup? Still waiting on the x-pipe though they say it is ont he way. I am going to the paint shop today and see what the chances are that you could put a satin topcoat over the standard Schwartz black finish. That with black chrome phonedials should look pretty awsome, I think?

Keep up the good work. I almost have my 1000 miles so that I can start messing with the timing. Car is running just awsome. I can't find enough excuses to drive it though.

dprantl

Do we also have any idea what retarding the cams this much does to emissions? In my case, I need to pass every year. Just passed again this year with flying colors. 4th year in a row with X-pipe, high-flow cats and a supercharger. My cams are currently set to stock.

Dan
'91 928GT S/C 475hp/460lb.ft

PorKen

Brian - more HP! Not sure yet how it will work with an auto, though. Will probably have to adjust the Bowden cable for higher rpm shifting.

Dan - NOx emissions may be lower? MPG might go up on the highway?


I have increased the idle ignition advance a touch, because the idle has lost some of it's S3 smoothness. Oddly, low speed (<2K) torque is still good. The exhaust note seems 'better' at 12 (vs. 8), more musical.

Needed more fuel >4500. Going by my past dyno graphs, I'm pretty sure the HP peak has inched closer to 320 rwhp. (SAE, Tom M.! )



From what I've been reading, later closing of the intake valve is what is making power here. Closing the exhaust valve ATDC may be helping too. The late closing of the intake valve effectively gives the cams more duration, which packs more air/fuel into the cylinders at high rpms. The late closing exhaust lets the exhaust pulse vacuum out the cylinder.

More duration lowers the 'high' S3/GT 10:1 static compression into the low nines (more?) reducing the effort required to compress the mixture, and allowing for much more ignition advance. More ignition advance masks the lower torque which would occur if only the valve timing were changed.


With -12° retard (crank° BTW), the S3 intake closes at a manly 62° ABDC, the exhaust at 7° ATDC.


(Valve timing, low vs. high speed engines)


(GT, GTS cams)