I have a 2006 RL. I also have a 2007 MDX. I know the engines are different..the MDX has a 3.7 instead of the RLs 3.5, but they are very very similar.

I've noticed that my MDX seems to engage VTEC sooner. It's somwhere between 4500-5000 rpm, you can clearly feel VTEC engage and the extra power comes on.

On my RL, it seems like VTEC doesn't come on until almost 5500 rpm.

I also seem to notice that the MDX revs higher...I want to say that the MDX seems to pull all the way to teh redline on teh tach..whcih is like 7000 rpm... but my RL seems to shift gears slightl lower..like 6500...

it's not a huge difference, but it just seems like in some ways the MDX has a more aggressive rev pattern..in that it engages VTEC sooner, and if you are really on teh gas, you pull to higher rpms..

it's not a huge deal to me...maybe it's a characteristic of the engines being different, maybe it's a tuning / ECU difference?

do all the RLs - 2005-2008 have a similar ECU profile or VTEC engagement?

i'm not gonna go out and buy a VTEC controller to change this...it's not that big of a deal..the car is plenty quick for my needs..i'm just wondering why the RL's shift point and VTEC engagement is more conservative..i know it's a luxury car..but i figure if you are hammering the gas, it' knows you want to go fast..why not just have it kick in sooner?

 

The following is from the Acura site:

'06 RL

VTEC™ (VARIABLE TIMING AND LIFT ELECTRONIC CONTROL)
Acura VTEC™ (Variable Timing and Lift Electronic Control) is a major contributor to the engine's large gains in horsepower and torque. The system operates the 12 intake valves in two distinct modes, so that the operation of the intake valves changes to optimize both volumetric efficiency and combustion of the fuel-air mixture. At low engine speeds, the intake valves have low lift and are open a comparatively short period of time during cylinder filling. At high engine speeds where breathing is critical, the valves switch to high-lift, long duration mode to deliver the best volumetric efficiency. The VTEC™ changeover point is undetectable to the driver and occurs at 4950 rpm

'07 MDX

The MDX's VTEC® (Variable Valve Timing and Lift Electronic Control) operates the 12 intake valves in two distinct modes. Operation of the intake valves changes to optimize both volumetric efficiency and combustion of the fuel-air mixture. At low engine speeds, the intake valves have low lift and are open a comparatively short period of time during cylinder filling. At high engine speeds where breathing is critical, the valves switch to high-lift, long duration mode to deliver the best volumetric efficiency. The VTEC® changeover point is virtually undetectable to the driver and occurs at approximately 4500 rpm

 

^ Interesting to know!

My 03 accord V6 changeover is at 4750rpm i believe. My old 01 Accord V6 used to change over at 3500rpm due to economy VTEC(NOT AS GOOD).

 

Acura may state that the VTEC changeover occurs at 4950 rpm on the RL, but I can clearly feel "A" changeover at 3500 rpm -- a clear increase in power and acceleration, similar to the cut-in of boost with an older turbocharged vehicle. Unless what I'm feeling is the change-over of the two-way valve in the intake manifold (to shorter intake runners) I have to assume this is the VTEC change-over -- and it is quite apparent by the much more rapid increase in engine rpm and sense of acceleration speed.

At the same time I've noticed NO change or increase in acceleration when revs pass through the supposed 4950 rpm threshold. Maybe it is undetectable, but I have noticed no similar increase in acceleration as when passing the 3500 rpm threshold.

Anyone with similar observations??

 

Rl engages a little after 5 you can definately hear it crossover if you listen

 

Yes, I suspect it's their treatment of the air intake system. Vtec is rather quiet otherwise. Very different then my S2000 which screams the moment vtec opens up.

On our TL (which we sold) it was more noticeable.

 

You can also feel a bit more acceleration as well. It's nothing like, say what happens at the VTEC crossover in an S2000 (feels like and pushes you back a little more in the seat), but you can definitely hear and feel something.

 

If you have the room, keep the car in third and accelerate through 5K and you will feel the difference. In second, the gear is a little to short to feel it. Unfortunately, 5K RPMs in 3rd is about 80, which is hard to do around here without someone who has blue lights in the car noticing!