Thanks for the dyno plots.

 

red, for some reason i get the feeling that you're a BIG fan of the centrifugal SC

i trust your experience with the shop manual/testing vtec, and yes it's good to have those factual pieces of information.

i'm not familiar with the actual vtec control system, but i'm almost positive that it's some kind of feedback control system. it might take a honda engineer who is familiar with the design to tell us exactly how that control system works...which kinda makes me want to work for honda! hopefully the honda plant in ohio will need an electrical engineer in the near future!

 

[QUOTE=S2-3456789-K,Sep 19 2007, 10:08 PM]red, for some reason i get the feeling that you're a BIG fan of the centrifugal SC

 

I say that throttle position is almost not a factor, as the necessary throttle position will change depending on engine speed and therefore oil pressure. Kind of along the same lines as including Time Since Engine Startup as a condition. The amount of time the car has been running is not really wants important, being at normal operating temperature is which comes as a result of the car running for a certain amount of time.

The minimum conditions will have to be constants and not variable based on other factors.

 

be careful with that, unless your inside the factory ecu, turning it on that early, doesnt help at all. the stock setup also amplify's the spark voltage on vtec engagement. so if your turning it on without enough oil pressure, possible damage, and without the spark voltage increase, and fuel trims up, all you get is a bunch of noise, and or a huge lean spot.
but hey, just FYI. lates

 

I'm pretty sure it's 6200rpm

 

Perhaps the difference in altitude is causing a difference in oil pressure? At a higher altitude, the oil would not necessarily reach the needed pressure for VTEC engagement till higher RPMs are reached.

This accounts for the shop manual as well as the difference in VTEC engagement at altitude.

I'd have to do the math to figure out how much of an oil pressure difference would be seen at altitude vs sea level.

 

[QUOTE=S2K-F8,Sep 18 2007, 09:14 PM] Here at 5280ft above sea level my VTEC doesn't engage til about 6.5k.

 

I recall somewhere that the offical VTEC engagement point for the F20C is 5850 RPM. My dyno plot (more or less at sea level) concurs with this too.


RMX5 - My Shop (Service) Manual says this about testing VTEC engagement:

1. Reset the ECM....

2. Check engine oil level....

3. Warm up to normal operating temp.....

4. ROAD test the vehicle:
Accelerate in 1st gear to an engine speed over 6,000 rpm. Hold for at least 2 seconds.....

This (ROAD test) does lend credit to the fact that at least in the B16A engines, VTEC will not engage if the engine is not under load. They say ROAD test and not just rev at rest. There is no reason why VTEC should or would engage at any RPM if not under load.

 

[QUOTE=mxt_77,Sep 19 2007, 09:33 AM] The last time this debate came up, someone (Elistan, I think) mentioned that he has seen late VTEC when driving at high altitudes.