The intake cam is retarded at high RPM to increase top-end power (intake cam timing logs prove this). Intake valve closing is the single most important valve event since it determines dynamic compression. Retarding the intake cam at high RPM allows the cylinder to take advantage of the inertia of the incoming charge of air. At high RPM the intake charge velocity is so high that even as the piston is coming up at the start of the compression stroke, air continues to rush through the closing intake valve. A late intake valve closing is no good at low RPM since it can cause air to be pushed right back out of the intake valve until it closes completely.

The ECU retards the exhaust cam at high RPM to reduce the lobe seperation angle and increase overlap. More overlap = better top-end power. Since the ECU also advances the intake cam at low to midrange RPM to increase torque, the exhaust cam needs to be advanced as well to minimize overlap.

When he disconnected the exhaust CVTC control, the cams were left in the retarded position. Since the ECU advances the intake cams in the low and midrange, valve overlap increased dramatically reducing power at lower RPM.


Original poster: Any idea how many degrees the electromagnetic retarders sweep?

 

Just saw this thread pop up - I know the question was asked a while back, but....

On the hex values for cam timing, '80' corresponds to approximately 0 degrees on the intake cam. 'C6' corresponds to approximately 38 degrees. If you count in hex, you'll find that each increment corresponds to approximately 0.5 degrees of cam advance.

We've done testing in increments as small as 2 degrees at a time to develop composite cam timing maps and there is sensitivity to changes that small in optimizing power. You will need a dyno to effectively make changes in this space though, as the changes in output are small and localized to narrow rpm ranges.

Shawn Church

www.churchdyno.com

 

This is why I cant wait for my OSIRIS tune! Shawn is the man!

 

this sounds like a dream come true. i love dohc

 

Shawn, thank you for answers. Now I can try doing some real damage to my engine

Wow, you must have done many re-flashes in order to come up with tuned intake cams timing map. Really wish that you were on the East coast.

Perhaps Julian or Vinny will buy into Osiris some day?

 

see im intrested in this because i have a revup and would like to know if more power is to be had even stock wise from this by manipualting the cams. This is how i hear japanese tuners are getting the most power out of DEs especially the revups. Can you explain exactly what needs to be done to actaully make this worth wild on a revup. And if this is a tuner specific thing or something that would have to be mailed ala flash.

 

I will be testing this soon on my revup once I get the OSIRIS, I will post my settings for folks to try once I think we have maxed out the stock setup I am on.....then open her up with true duals and trying again....then test pipes....then plennum (preferably cos)

Although maybe the plennum should be done first and tested ....see if the exhaust is really that much of a restriction....hmmm

Either way I feel with as rich as RevUps seem to run with a little cam timing and fuel tuning the $600 will easily clean up the cars response and add some power even stock....

 

agreed My revup list are going as so

Cosworth Plenum :which was already comment by cosworth to provide substantial gains on a revups top end.


Crawford headers : Best header nearly equal length for the DE and DER


Stillen TD exhaust Or Borla : Rational , best overall gains seen


Fast intentions HFC metallic substrate or Berk HFC metallic substrate : Rational: i have issues with choosing between both save a 100 with the berks but the piping is 60 mm. While exhaust will be 2.5 and headers will be 2.5 as far as mating them. Or Go with Fast int Which are 100 more and are 2.5 from what i seen.


JWT S7 Cams : Rational : the best damn cams i seen for a revup...matter of fact the only ones i seen.


JWT Clutch and Flywheel : Rational : Great results and almost stock feel while providing better performance.


3.9 Gear from 350 evo or central 20 :
rational : best for NA acceleration proved in road raced 350z and toted as the best bang for the buck .


Tuned with Utech( basic tuning ) Or Osrius (cam manipualtion for revup)

I believe hear well find a 300rwhp dynojet >>hopefully

 

you can get any cam you want for the revup......you just have to know where to get 'em.

 

I have the jwt s7 cams. They come on around 4k rpms if you look at my dyno. If i had to do it again I would of got bigger cams with brian crower valvetrain and spun the engine too 8000 rpms or more. I think the cams move as much as 40 degrees.

 

See your situation would be nice if you where at stock compression or even higher your numbers are reason of your motor build. Wish you werent low compression so we could see what the revup could do with teh cams etc. I think well see 300rwhp very soon with the revup.

 

Nismo blanks perhaps

 

nismo does offer blanks for the the 287 motor, but not for the revup.

 

I'm sure more shops will become Osiris tuners. In the meantime, if you can round up a few guys who want custom reflashes and rent a dyno for the day, I could see about visiting for a day or two.

SC

 

On the revup engines (like my 05 6MT that I spent a lot of time learning the Osiris package on) the cams are generally happy at near stock settings below 3500 rpm and above 6000 rpm. That isn't to say there aren't some gains to be had, but they are small. The biggest gains (on the revup again) we've seen tend to be in the transitional range between 4000 and 6000 rpm where the stock ECU program is rolling the cams back from maximum advance to full retard. Tweaking this transition can net some very nice torque gains.

I'm really interested in tuning a VQ (revup or otherwise) with aftermarket cams as these will probably need substantial tuning for optimum power. It could be that some of these cams perform much better than optimized when cam tuning is done properly.


SC

 

More people will buy into Osiris once the tunable version is released to the public. It is so easy to tune, the utec took me hours to get right. Osiris took like 30mins for a perfect a/f ratio. I just left the partial throttle map alone since the ecu does a good job there. For some reason stock it was at 11.5 a/f ratio from like 5800-7k rpms. 221whp for a low compression engine at 3800ft elevation isnt to bad, it would be quite a bit more at sea level. I have to get another car before I turbo it, so I have been playing around with different things on it untill then. I really need to take my car down to the uprev guys and leave it there for some cam tuning.

 

I will be buying the Osiris once there is a Tunable version

Got use to being able to tune my own car with the UTEC, so i dont want to take a step back in time.

Looking forward to the Tunable version.

Todd

 

Well this is an old thread of mine. Since I have newest version of Osiris I have some ideas. I think If I set the exhaust cams in Osiris at 0 degrees from 6400 rpms and up, and set the intake cams with a little more advance in the top end and slow the transition rate I should make power over 7000 rpms, as you can see in the old graph. The horsepower flatlines untill the rev limiter kills it. I am almost tempted to get some oversize hr pistons and drop them in with a bore hone 12.1 compression with them. Anyone have some input?

HR pistons about 300$ from nissan
http://forums.maxima.org/all-motor/5...hout-mods.html

 

Do it!

 

Cam tuning has always interested me. I was happy to see the revup get a variable exhaust cam.