Blow off valve on CVT

Bladed · Jan 2, 2008, 01:31 PM

I just have a quick question. If you have a CVT tranny and you get a turbo, is a BOV needed? From my understanding, a BOV is only used in between gear shifts to release air to reset itself, but since the cvt never shifts gears (unless your using sports mode) that means the turbo could keep spinning right? But what if your using sports mode, how will you engage the BOV when you shift since its not really shifting, just a different tension in the cvt belt? (sorry if this doesnt make since, i only have a basic understanding of turbos)

Lol title is missing an F.

evo_soul · Jan 2, 2008, 02:21 PM

as long as you have throttle/ (foot on the gas) even in sport mode, there is no blow off. Its continous power unless you take you foot off the gas.

mattsgts · Jan 2, 2008, 02:48 PM

Quote:

Originally Posted by evo_soul

as long as you have throttle/ (foot on the gas) even in sport mode, there is no blow off. Its continous power unless you take you foot off the gas.

thanx for explaining that, it kinda had me baffled to. so will the continuous use being on the cvt tranny couse the turbo to ware faster or dammage the turbine??? or am i just thinking to hard

futurevowner · Jan 2, 2008, 05:06 PM

cvt switches gears, unless your first gear can do 100, it has gears and shifts for you, yes you need a bov

ambystom01 · Jan 2, 2008, 05:09 PM

You would need a BOV anyways for when you get off the throttle.

SpeedI2acerX · Jan 2, 2008, 05:55 PM

so there's a throttle plate? which close and open.

ambystom01 · Jan 2, 2008, 06:08 PM

No idea, I don't drive a 2008 lancer much less a CVT lancer. I would assume there is something like a throttle plate.

SpeedI2acerX · Jan 2, 2008, 06:10 PM

so there's a throttle plate? which close and open right?

ambystom01 · Jan 2, 2008, 06:13 PM

If the 4B11 is like the old 4G94 then yes there should be throttlebody with a butterfly valve which necessitates the use of a BOV (as do other things).

**Blacksheepdj** · Jan 2, 2008, 06:14 PM

Quote:

Originally Posted by futurevowner

cvt switches gears, unless your first gear can do 100, it has gears and shifts for you, yes you need a bov

Um, the CVT doesn't have a 1st gear. Are you unaware of what the CVT transmission is? There are no gears. The transmission DOES shift for you.

Quote:

Originally Posted by SpeedI2acerX

so there's a throttle plate? which close and open right?

Yes, I'm 99% sure that it has a throttle plate.

futurevowner · Jan 2, 2008, 06:20 PM

thats what i meant it is an automatic essentially, and switches for you

evo_soul · Jan 2, 2008, 06:47 PM

no I think your still not fully getting it, there really is no gears at all, the transmission is run by two pulleys that have the ability to shift in sizes. These changes in sizes are what gives you an unlimited range of gear ratios. Mitsu Development team has choosing certain 6 Gear ratios.

Lets take a look, below are the 5 speed MANUAL transmission and following behind it are the CVT Ratios,

5 speed gear ratios
1 3.538
2 1.913
3 1.333
4 1.028
5 0.820
Final Drive
4.235

CVT Sportronic Ratios
1 2.349
2 1.397
3 1.074
4 0.832
5 0.631
6 0.518
Final Drive
6.120

Now remember since they are arbitrarly selected ratios, in theory if i didnt like gear ratio number 6 i could change it to .49 or .55 If i wanted to i could copy the 5 speed ratios if i wanted to. Of course i would need a CVT ECU override controller to do so. but in theory anything is possible for the CVT.

Getting backto its operation, the shifts on the CVT happen almost instantly, and even in that fraction of a moment of flux, the throttle of the engine remains at 100%. Its beautiful

futurevowner · Jan 2, 2008, 06:54 PM

ok but you would still need a bov, am i right or wrong? i understand how cvt works, i just didnt feel like going into detail, but what im sayin is under normal driving you wouldnt floor it and when you let off the gas it would release the built up boost from the rpms?

ambystom01 · Jan 2, 2008, 07:01 PM

Yes since there's still the issue of you letting off the throttle.

**Blacksheepdj** · Jan 3, 2008, 07:53 AM

Quote:

Originally Posted by futurevowner

ok but you would still need a bov, am i right or wrong? i understand how cvt works, i just didnt feel like going into detail, but what im sayin is under normal driving you wouldnt floor it and when you let off the gas it would release the built up boost from the rpms?

Yes. You always need a BOV. Any car can function without one, but it's always smart to use one.