Variable Valve Timing

[skinner]

How does Renaults VVT work? Is it similar to Hondas VTEC, or is it completely different?

 

[McBunny]

its very primative
vtec is timing and lift
vvt is just timing

 

[skinner]

So are we talking 1 inlet and 1 exhaust cam profile, with the ability to adjust the phase lobe separation and nothing else, or can it alter duration in some way?

 

[Lagerlout]

Only alters the exhaust cam iirc. Its done by a solenoid activated by oil pressure iirc. Its active between 1500rpm and 5000rpm. thats about all I can remember. BenR will tell you for sure!!

 

[Alex_225]

Dunno if its me be a bit stupid (could well be lol) but I didnt really understand the explainations above. Can someone put it in the same terms as if they were explaining how to set the VCR for a middle aged woman!!

 

[McBunny]

largerlout iirc it only works at idle to smooth out the idle

 

[Griff]

It does work/active between 1800rpm and 6500rpm so largerlouts correct about that part.

Or to be exact it advances the inlet cam by 16degs if the oil temp is above 80degs and the throttle is at 85% or above.

 

[McBunny]

If your reading the dialogys you should know that the vvt system advances the cam 16 degrees (use the cam timing info if you want IO/IC/EO/EC) after 1800rpm when at WOT.

The cam sits in its depahsed status until certain parameters are met (engine speed, throttle position load, coolant temp etc etc) for a smoother idle and lower emissons due to zero overlap. Once the cam is phased overlap is created and much higher VE values can be attained at higher rpms than without any overlap.

There is no vvt ativation at 5000rpm, this is just the jump in VE when inertial acivities in the inlet tract work with the cam profile. THe point of highest torque is the point of peak VE in any engine, and the 172 has about 86% peak efficiency IIRC....so not that great.

 

[BenR]

lol.....correct, infact, spot on.

 

[McBunny]

i wonder why

that was a copy of a post done by you mr Genius

 

[Darren S]

McBunny - please tell me you copied and pasted that post. Or did you have you professors hat on at the time?

D.

 

[Darren S]

^^^^ - ah, I see!

 

[BenR]

Quote: Originally posted by McBunny on 08 April 2005

i wonder why

that was a copy of a post done by you mr Genius

shhhhhhhhh, dont tell people!

 

[skinner]

Thanks for the explanation, exactly what I wanted to know.

So from that I assume Renault arent going to get much more out of this engine. To get a lot more power would mean changing the cam duration and lift, which will affect the whole rev range, causing idle and emissions problems for them.

 

[JAF 182]

Ben R, McBunny did you pay skinner to ask this one!?

 

[McBunny]

lol nah it just get brought up very often

 

[BenR]

Quote: Originally posted by skinner on 08 April 2005


Thanks for the explanation, exactly what I wanted to know.

So from that I assume Renault arent going to get much more out of this engine. To get a lot more power would mean changing the cam duration and lift, which will affect the whole rev range, causing idle and emissions problems for them.

out of a std engine, with the current trim of VVT, no they wont get any more really.

However, the VVT system uses a vane type phaser and its quite possible to turn the solenoid plunger into a flow control valve by running frequency control through it, then you could control the entire phase pattern and have it run as a curve rather than an on/off switch.

 

[PeteB]

Does upgrading the flux capacitor affect vvt?

 

[jezp]

nope you need 1.21 jiggawatts for that only attainable with plutonium and renault dont deal with terrorists or do they?

 

[BenR]

only if you can get hold of a Mr.Fusion food rubbish converter.

 

[Tom]

Quote: Originally posted by BenR on 08 April 2005


However, the VVT system uses a vane type phaser and its quite possible to turn the solenoid plunger into a flow control valve by running frequency control through it, then you could control the entire phase pattern and have it run as a curve rather than an on/off switch.



When you say possible....

Would it be worthwhile? sounds like a fairly good thing to do.

 

[Josh]

Quote: Originally posted by PeteB on 08 April 2005



Does upgrading the flux capacitor affect vvt?







Quote: Originally posted by jezp on 08 April 2005





nope you need 1.21 jiggawatts for that only attainable with plutonium and renault dont deal with terrorists or do they?







LMAO

 

[BenR]

not really worthwhile unless your running a very wild cam on a street motor with new pistons to ensure no contact between pistons and valves.

Because if it was on the track, the thing would never come off cam.

 

[Ben H]

Does the VVT account for the "extra power" that the 172 lump has over the good old F7R Willy lump? Or is it other stuff?

 

[Mike@Rentech]

Nah thats down to the di-lithium crystals in the engine management system.

 

[BenR]

Quote: Originally posted by Ben H on 09 April 2005


Does the VVT account for the "extra power" that the 172 lump has over the good old F7R Willy lump? Or is it other stuff?

nope, its just miles better in terms or design alone.

Head, crank, piston, ring drag, intake and exhaust system, valve train etc etc

 

[skinner]

More questions!

Is the VVT active all the way up to the red line?

I could be completely wrong here, but the inlet tracts look quite long and on the picture I saw, 90 degrees of it looked like it was cast with the head. Does this make it expensive and awkward to improve?

 

[BenR]

Nope, it dephases again at 6500rpm, why i do not know exactly why they decided that, but it corresponds with a peak of just under 7000rpm for all cams being run so far, due to the ECU closing overlap.

The inlet manifold can be massively improved and i have spend ages developing the best runner profile, and currently its still only getting better. The manifold is 2 part, and the 90 deg bend is seperate to the head, its not cast on.

 

[McBunny]

he is a geek but he is our geek

 

[skinner]

So when people are using Omex or other ECUs, the VVT is still controlled by the existing ECU?
I take it the std one is not user friendly in the reprogramming department...

 

[BenR]

The std ECU isnt user friendly no.

And any standalone ECU which can control an RPM/TPS 12v output can control the VVT>