K thanksOriginally Posted by AKDMB
K thanks
Guys, possibly a stupid question, just trying to grasp cam timing a little better. The IVO degrees is in terms of degrees before TDC on the exhaust stroke, right? For instance -20 being 20 degrees before tdc. Then EVC is after TDC on the intake stroke. 16 degrees evc being 16 degrees after tdc.
ivo.PNG
evc.PNG
It refers to crank shaft degrees. That way the ecu definitely knows where the piston is.
Yeah I should have clarified that it was in crankshaft angle, but the order that I mentioned the events occuring was correct right? Negative IVO values are before TDC on the exhaust stroke and Positive EVC values are after TDC on the intake stroke.
It's movement from base or start position. Yes negative is in the direction of BTDC and positive is in the direction of ATDC. Depending on the height of the lobe that you measure from is what gives you true overlap. But you don't really need to know that to tweak it a little bit and see what it does. As long as you know which way the numbers move the cams you get a general idea of what overlap should be doing. You have it correct.
I'm just doing a little research(very informal), for an engineering class, trying to compare cam timing in a typical old school small block to that of a modern dohc motor, using the coyote for an example. It helps to put the cam timing data in the tune into perspective. Thanks for the info.
Last edited by AKDMB; 02-24-2016 at 11:44 PM.
We don't know the true starting point of a 15/16 at this time. Waiting for someone to degree the stock cams and then share the info with us for free.
Numbers are very similar to what you would see with a timing light. Movement of the distributor from a vacuum ignition advance/retard(not sure which it was) would be comparable to movement of the cams. Over simplified of coarse. Everything improves with more variability.
Just to make sure I've got it right, though, VCT parameter values relate to the "park" position for the cams?
So 0 is not 0 (TDC), 0 is actually 0 degrees from park position?
To know what actual cam position is for a given value of VCT IVO, you reference it to park position.
IVO @ park = 33.5 ATDC, if VCT IVO parameter = -10, then actual cam position 33.5 - 10 = 23.5 ATDC
I'm basing this on what I read here:
http://www.hptuners.com/forum/showth...position+units
Higgs - "the numbers I am using are what get's it close to the old numbers based on their valve events at park and max.
If the 14 was IVO 33.5 ATDC @.050 at park, and we assume 0 is park, then it idles at 33.5 ATDC and the 15 idles at 40 ATDC.
and so on.... again, "or maybe not...."
and this thread @ SVT
http://www.svtperformance.com/forums/showthread.php?823528-Stock-Cam-Specs
Last edited by GapRider; 02-25-2016 at 05:39 AM.
2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
Stock everything else
they both idle at 33.5 ATDC
cam events.JPG
Thanks for the recommendation, will have to try it later since I'm away form the car for a few weeks. Was going for the more aggressive -40 since I know if it runs there it will at -35, -30 and so on. Idle is set at 800 if I remember correctly (all my cam tunes are in the 800-950 range), don't have the tune file with me.
On a side note, I was trying to get better drive-ability (mostly of the line), using one of the limiting tables (stock the table was set all to -60) set it up by rpms and on the intake cam limiting to -15 since I saw the none cam tune going to that range at low rpms and it became not driveable with the A/C off which I found completely strange.
2014 GT BLACK MT Brake Package - GT500 AB
This is assuming they both idle at 33.5* ATDC. The cams are known different so we are not sure.(ford dealers are not responding to my request for specific cam specs) The numbers movement of the base positions are all correct. notice how ever IVO 0 EVO 20 = -42 and IVO 20 and EVO 40= -42. The overlap is the same just in a different position to TDC so it will not have the same flow benefits. That is the benefit of dual VCT instead of just one cam VCT.
looking at the speed density MP 13 and 26 have the most overlap they also have the best looking numbers for lower or higher RPMS. For reference the offset value is how much pressure above BP the cylinder can actually get to before the IVC happens. This is why I choose to have the ECU target 26 instead of 14. Now my stock engine will not ever come close to producing the values in the speed density with out FI. It does however allow me to tweak the vct numbers and get improvement rather than have the ECU try to modify the path to fit a worst speed density it modifys the path to achieve something it could never get to. I may have been a little bold and it could be further improved by seeing where the values get to and choose a target closer to the actual values. Its another factor in what drives MP % weight's. May be the only factor to keep the MAF and SD as close as possible. We can discuss further in another thread.
What they are saying is use -35/20 for a cam tune. In the 15+ GT the equivalent would be -15/11. but it would only be the same as far as movement from base position actual over lap is sure to be different.
Last edited by murfie; 02-25-2016 at 12:54 PM.
I got my tune file working almost perfect thanks to you! one week of testing gone smooth, how can I smooth my idle, after driving or revving engine for say, when the car goes to return to idle it drops to 500 rpm then surges back to 800-1000, ive raised spark more and more but seeing little change
2013 Roush stage 3
Pypes cat delete
Tuned by me.
actually, it sounds like you are where I am with the cam tune : ) I'm still experimenting and haven't played with the cam tune in a little while. I'm trying to learn some more stuff before I give it a go again. I will definitely post up as I find anything.
2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
Stock everything else
banging my head against the wall with this lol
itll chop for a while then smooth its idle out, you blip the throttle and itll surge from 800-1000 too. getting closer with it
Post your tune and your log if you don't mind
post your tune file, what have you changed from your stock file this far?
2013 Roush stage 3
Pypes cat delete
Tuned by me.
ghost cam tune.hpt
changed eot vvt table, mapped point tables etc etc
probably doesnt help its got a edelbrock on it lol
I couldn't open it, said it was locked
2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
Stock everything else
I'll fix it
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