Hi All Does anyone know at what RPM points the variable cams (VCT) activate and then de-activate in an N/A VG30DE? Thanks Nathan
Hi Nathan, hopefully others will add what they know, but this will answer the basic question. Info taken from Z32_VG30DE_40P01_1991_NA_MT_JDM.bin as supplied with Nistune. VTC Min Temp Cut: -45 VTC Max Temp Cut: 110 VTC RPM Recover: 1800 VTC RPM Cut: 5800 VTC TP Cut: 40 VTC Maximum Speed Cut: 0 I think these are fairly self explanatory, but if any one has interesting insight to the working of VTC, please post.
I have read that the VTC will change it's on and off points within those ranges noted above. It is not a steadfast setpoint.
Yeah I would think so, TP cut being the main factor, temp and speed are out of operating range. That 40 is actually TP (MSB), so 40 on a scale of 256, so it's like 15% of scale, and that scale is roughly a load indicator. If there is a cut at approx 15% "load", I would assume it means under that point, VTC is not used. I have generalised a bit, this is taken from a Nistune mapping guide page 7, good outline I have based the above on. http://nistune.com/docs/NIStune_Mapping_Guide.pdf Theoretical Pulse width (TP) = MAF Lookup * Injection multiplier/RPM
Speaking of VTC... I was playing with TunerPro the other day and saw that the VTC release on my TT is set at 5900 rpm. Yet a few "tuned" bin files I have looked at, have reduced this down to 4900 rpm. I know the correct way to set this value is on a dyno, but how does reducing the VTC release point make more power?
5800/5900 RPM is usual TT manual and NA auto/manual cut, 4800/4900 is normal TT Auto cut, and what is the commonality of that data set ? The cams are different in the TT auto. The "tuned" BIN files with the lower cut are possibly TT auto BIN's.
Nah, most "off the shelf" tunes tend to drop the VTC to 4800rpm. Probably because Devon did a few dyno based tunes and found this to be approximately optimal, and seeing he was one of the most publicised VG30 tuners on the net it's popped up in most the tunes out there.
So how does it work?? In real life experience, or from a mechanical point of view, how does reducing the VTC release generate more power?
To Mike and all respondents - I appreciate you too. Thanks for the info. The reason for asking is that I'm running a VG30DE in a speedboat (Miss September) that runs a Holley 390cfm 4-barrel carby. Currently for ignition, I'm running an adapted RB30 dissy, where the CAS fits on. The dissy is set up to run a Crane Fireball electronic ignition system. As for the VCT cams, they are activated constantly, being hard-wired on. My current dilema is that the ignition is breaking down at 6000/6200rpm. So I'm looking to use an EMS Stinger to run the ignition and cams only, leaving the carb on (for now - ITBs a future plan). Thanks again. Nathan
Nice boat you have there. Any video with sound ? I guess that you going with the stinger to support injectors and ITB's latter on. Had you considered using a Nissan ECU with Nistune fitted ? Would be a lot easier/cheaper to set up as maps are available. Only thing is you would have to run some sort of intake for the MAF.
