i hope i am not reposting... i looked around i did not see what i was looking for, so i guess i will ask. i have a 00' SE so i obviously have the VI. how does it work exactly? i heard it opens up around 5,000rpm for the extra power... is there a way to make it open early for more power earlier in the rpm's? will it even make more power earlier?

i am also interested in q45 throttle body swap... i think i might go wih the pathfinders tb instead because that does not have the MEVI like the Q45...

how hard is it to do the TB swap? i dont have a lot of mechanical experiance
however my brother does!! with his help i think i could get it done...

 

go to the all motor forum and check there.

 

ummm i am almost positive i posted this in the all motor forum and i think it got moved to here...

 

There's a reason why it opens at a certain RPM.

 

and i want to know why...

 

It just switches between two different intake runner lengths. One is good for low-RPM power and one is good for high RPM power. 5,000 is the point that Nissan engineers decided was optimal, but depending on your mods, you might want to tweak it slightly. Key word is slightly; if you have it switch at 3,000 you're not going to see some sudden power boost; in fact you'd see quite a power loss.

 

ok, thanks for the response... thats all i wanted to know about that...

what about switching to the pathfinder TB?

 

It doesn't switch between two runner lengths. It's operation is similar to the MEVI.

 

Acually the rod opens to a chamber, creating resonance. There is only one set of runners. BTW I have my switch set at ~4600 which is optimal for the 00VI.

 

I don't recall the details but it's the same idea. I'll be more general and say it switches between two different intake configurations.

 

It doesn't create the resonance. It takes advantage of it.

 

how did you change it?

did you change it because of your y-pipe and intake?

 

Go to a dyno, dyno with it zip tied open all the way to redline, and one with it closed -redline, and where the 2 curves cross, use that point.

 

5200 RPM, to be precise.

The crossover point was obviously chosen by Nissan, since they thought that was the optimal point.
Some org members (IceY2K1 comes to mind) believe the switchover point could be pushed back a little, to say ~4600RPM, after looking at some dyno graphs (seems there's a dip just after that point I think...)

It wouldn't make sense to open it before that, because you'll actually lose torque--The resonance chamber (high-RPM stage) is designed to provide volumetric efficiency at higher RPMs, while the regular long-runners are tuned for good efficiency at lower RPMs. Disabling the high-RPM setting would result in air restriction at higher RPMs, reducing high-end torque, but enabling it all the time would result in too slow of air velocity at lower RPMs, reducing low-end/midrange torque.

 

how do you actually change it though? i want to try it and see if i like it... thanks to my tax return i will be getting an injen intake, cattman y-pipe and d2's....

 

You use an RPM switch to change it.

 

I think for a vq30de....the lowest I would set it at would be 4500.....in my 2k2 the VI opens at around 3900 give or take 100rpms.....and I think I know why nissan set it so low on the vq35de...it's cuz this engine has so much power all over the graph that opening at 3900 wouldn't hurt too much....as with a vq30de it needs to stay close until higher revs where it gets a more power....unlike the vq35de where it gets mad power all over the place

setting a VI below 4500 on a vq30 isn't too good of an idea....unless your boosted and packing crazy punch all throughout the powerband....like the vq35