Nissan Patrol 4x4 (Africa)

Saw the magic "PVA" abbreviation mentioned elsewhere on our forum as a means to get better consumption and responsiveness from a 4.8 auto... googled PVA mod and came up with this..

http://www.patrol4x4.com/forum/diy-modi ... ndex2.html

Looks like a no-brainer?

Regards,

Peter

Peter, I spent a bit of time reading up on this issue around the web and the conclusions I reached are that (a) there are wildly different outcomes reported by various people (some report significantly improved power and consumption, others the exact opposite and yet others no change at all – it is all just too inconsistent to be able to reach any proper conclusion) and (b) nobody who has been doing this fiddling seems to have a really thorough understanding of the systems behind what they are fiddling with; I got very much the impression of "experimenting in the dark". In the end it seemed to me that the Nissan engineers probably knew far more than the people who are doing the modifications and I decided I would rather place my trust in the engineers than the modifiers.

Huh?

Great, I was going to attempt doing this the weekend? Reason I spoke to a Patroller yesterday and they did the MOD and with the freeflow, they are getting 7 km/l. And the responsiveness of the vehicle is apparently very good.

Clem, considering that you did so much research, can you maybe say if there has been any negative results after doing this?

I also didnt want to originally do this mod, but the guys I spoke to says that it was put in place to prevent wheelspin etc at take off. After this mod the torque is there from start and you have to be a bit more careful.

Is there anybody on here that has done this mod? What is your take on this? Maybe someone with machanical background could shed some light on this?

I was excited to do this and now I dont know anymore?

Would a Tyota Prado also have such a thng-a-majiggy PVA welfie [the V6 Praat-ou ??]

NISMOnator wrote:Huh?

Great, I was going to attempt doing this the weekend? Reason I spoke to a Patroller yesterday and they did the MOD and with the freeflow, they are getting 7 km/l. And the responsiveness of the vehicle is apparently very good.

Clem, considering that you did so much research, can you maybe say if there has been any negative results after doing this?

I also didnt want to originally do this mod, but the guys I spoke to says that it was put in place to prevent wheelspin etc at take off. After this mod the torque is there from start and you have to be a bit more careful.

Is there anybody on here that has done this mod? What is your take on this? Maybe someone with machanical background could shed some light on this?

I was excited to do this and now I dont know anymore?

I can only tell you what I have read. If you start to search around the Internet you will find that there are other guys who have reported that the fuel consumption went up. I can also tell you that I am not sure that there is any proper explanation out there of exactly how it all works and fits together. My own perception (and I do stand to be corrected) is that if you have more torque (or power) it is only because you are burning more fuel. A petrol engine with an ECU detects the amount of air going into the cylinders and injects the correct proportionate amount of fuel. So if you increase the amount of air (by free-flowing) going into the cylinder, then the ECU must also increase the amount of fuel going into the cylinder. The only other possibility would be that if the free flow somehow improves the efficiency of the engine – perhaps by increasing air swirl in the cylinders or enabling a cooler airflow or something like that. On the other hand, nobody seems to have caused any harm to the motor by trying this so there is probably no reason you should not give it a try – it is after all completely reversible.

I would very much like to know and understand more about it if anybody has more information and a more comprehensive explanation. Perhaps one of the more technical guys on this forum will chime in.

My understanding is that if you cable-tie the valve shut you are actually lengthening the intake duct which provides maximum torque. Don't know if any of you played around with side-drafts carburettors with different length trumpets?
With longer trumpets maximum torque will be available at lower revs. The negative is that the torque band gets narrower and maximum torque might drop off earlier than before.

Resonance ram air effect? Could be but wouldn't one then lose on HP? When does the PVA open in normal operation?

Bit difficult to see when it moves. The butterfly is actually normally open and by doing the mod you cable-tie it closed. Can't remember the post but I remember somebody commenting on the Aussie forum that they did the mod and on the dyno it lost power On my car my revs are 99% of the time between 2&3k or below 2k so it doesn't feel like it lost anything - only gained low down according to my butt-so-meter.

i had a chat to graham and he said that the butterfly sits behind the airflow meter ,it allows more air into the motor and gives you more power faster .
all modern cars have them audi bmw toyota ect it is activated by vacuum after 3000rpm . on a 4.8 i hardly ever get to 3000rpm becouse i am doing 140 gps speed at 2400 rpm in 5 gear
my trottle response is much better also .the thing we must watch out for is going to lesotho highlignts you might be getting to lean but then u just cut the calble tie
my feul consumpsion on the new 4.8 is 6.1 to 6.2 at 140 gps speed and that with 35 takkies .........

Tinus,

So Graham approves this mod or just dont have a problem with it? Is it better to get someone like Graham to do this or can I do this myself? Vehicle is going for a service by G-TECH next week, maybe I should rather wait and let him do it?

Thanks