Comparison of 575M and Superamerica timing specs from the WSMs.
I had to reread the line, I understand except for Int 575M -1/50 mean my WSM had -7/56 and that is what lines up my rear marks.
Taz, I think you transposed the figures for the 575M and SA in post 73, hence the confusion? Steve, I note that you're saying the EC event is 13 degrees ATDC? Are we saying the WSM spec description is incorrect below for the Exhaust End event, where it says "- End before TDC: 13 degrees". Should this be saying "- End after TDC" ?? Image Unavailable, Please Login
That is a mistake, an exhaust valve closing event would not take place before the piston reached TDC. It should be after TDC.
The retarded intake opening is also strange, But if Steve set the intake cam opening at 7 degrees after TDC and then found that the intake cam closing matched up to the spec of 56 degrees after BDC, I would have to think that those timing specifications are correct. I am no engine designer or cam expert, just a mechanic that tries to get motors to run at their best and to factory specifications. Someone smarter than me is going to have to explain the weird cam timing that Ferrari is using on these motors.
It looks like Ferrari is keeping the exhaust valve open until 13 degrees after TDC but not opening the intake until 7 degrees after TDC, having only 6 degrees of overlap! Instead of the exhaust having a scavenging effect, helping pull in air/fuel in, it looks like they are trying to keep some of the exhaust in the cylinder as sort of a form of EGR? Maybe they are just trying to keep the scavenging effect to a minimum, so as to prevent the new air/fuel mixture from going into the exhaust? This seems like very tame cam timing on a performance motor, but may be necessary for emissions. It is also probably why the went to variable cam timing on the later V12 motors: 599, F12, etc. Can some cam expert shed some light on what Ferrari is doing with this strange cam timing?
Brian, your explanation for the retarded intake timing sounds logical. I'd also like to see a screen shot of the Superamerica cam specs from the Ferrari literature. Taz indicates the exhaust events are at 42/7, but I'd like to confirm if the wording in the SA literature has the same mistake as the 575M for the EC event, and it's actually supposed to be 7 degrees ATDC. I've redone my cam spec table from a few years back to reflect Steve's findings, and the "575M (corrected)" row now reflects Steve's work with his 575M, and the correction of the mistake in wording for the EC event. I also changed the SA's EC event to be a positive 7 degrees ATDC, which now gives believable overlaps and LSA's. I'm no cam expert, but Kevin Ban of Kelford Cams in NZ helped me a lot in the past with optimising cam profiles for both forced induction and naturally aspirated DOHC Japanese V8's, so I'll shoot these numbers over to him for comment. Image Unavailable, Please Login
I've been corresponding with Kelford Cams over in NZ about the weird retarded valve timing on the 575M cams, and here are their initial thoughts: The retarded intake timing could be a result of raised rpm to try and improve the cylinder fill efficiency by giving the charge a little more time at the end of the intake stroke. It’s not uncommon for VCT cams to be at that sort of timing for operation above 7000rpm where they retard back out. I wonder if Ferrari’s thinking was run the retarded intake timing for high rpm, but then also retard the exhaust to keep the overlap in it for midrange scavenge etc. If they have an efficient exhaust port then they may not need the advance we usually see on the exhaust cam to help on blow down before BBDC. I'll update with anything else I receive from them.
Could it also have anything to do with the intakes being extended in length after 6000 rpm when the actuator opens up the butterflies in the inlet plenum? and the timing needs resultant of that change being covered by such a method. There appears to be no gradual transition, the ports are either closed or fully open at that transfer point. Given that everything mechanical between a 575 and a 612 is the same, but Ferrari changed the timing on the latter, could that be an indication of them improving on their original thinking regards the best timing on these engines?
When I looked at the cam timing procedure for the 612 in the WSM it was identical to the 575, with all of the same dial indicator readings. So I have to assume that the cam timing is the same for the 575 and 612.
I am pretty sure I have read that the timing was altered on the 612 spec engine but the cams are the same as a 575?
Superamerica was changed, 612 was not. Part number for SA cams is different to reflect assembly marks advanced 6 degrees, but cams are otherwise identical.
I have obviously mixed up SA and 612 info then, thank you for the clarification. Given that both produce the same power, using the same cam profiles then I guess that change in degrees does not make any real world difference anyway, other than maybe where in the rev range it kicks in?, so any worries the OP has from deviating slightly from factory 575 settings should not be of any great concern in the overall scheme of things.
We do not know how much power the Superamerica produces after the hot rodding changes. The 575M was already on its way to more than 515 hp after the center muffler was replaced with straight pipes in Summer 2003 and later models had ECU upgrades (last version same as SA) that further pushed hp upwards. It is also possible the intake manifold runners were increased in size for the 575M and 612 when the boss for the intake manifold actuator was added in 2003 so a common casting could be used for the 612 and 575M. The 612 engine had enlarged intake ports in the heads to match larger intake runners, but most of the changes to get to 540 hp had already been introduced on the 575M. When the Superamerica engine came out (F133F for 612, F133G for the SA) well after the 612 engine, the 612 enlarged intake ports on the heads were also used on the Superamerica, in addition to the SA's increased 11.2:1 compression ratio from shaving the block, camshaft advance, and the improved exhaust valve seating. Ferrari did not want to say the interim SA had more hp or torque than its latest model, the 612, so they gave it the same ratings as the 612 engine. Would be interesting to run one of each on a dyno and see how they compare. Not sure what changes were made for the late 612 F133H engine except going to Motronic 7.3.2. There was no simple chart for the 612s like there was for the SA in the SA WSM, probably because Ferrari was not too anxious to advertise the 612 engine was an upgraded 575M engine. Image Unavailable, Please Login Image Unavailable, Please Login
