VVT 1*2.

[Aluco]

Do the 1*2's (including ph1) have VVT ?

Only reason I ask is a mate who's a mechanic has offered to do my belts for cheap but I told him it had VVT and he swears blind that it doesn't.

What can I tell him to make him understand that they do ? (If they do)

Tar.

 

[Scadden182]

yea they do. if he swears blind they dont....stay clear tbh.

 

[jaleach]

Just take him for a drive and let him feel it kick in??

 

[Revels]

Just take him for a drive and let him feel it kick in??

The 'kick in' is nothing to do with VVT. That's the car coming on cam.

VVT is much lower in the rev range.

 

[Aluco]

The 'kick in' is nothing to do with VVT. That's the car coming on cam.

VVT is much lower in the rev range.

Aye that's what I thought but he wont have it haha !

He's saying he can do the belts easy as it's not VVT but he wouldn't do a VVT so I'm confused.

 

[Jat_172cup]

Deffo VVT at 5k it kicks in iirc

 

[caister]

VVT on these is only for emissions at lower revs. The 5k kick is when the ECU allows the engine to have the fuel it wants and hence the kick in power and torque.

 

[theduck]

Definately has VVT.

Though it has nothing to do with the 5k kick as people keep saying.

 

[davebem]

We dont know your mate but be very wary, the correct tools are needed the and there is a strict tensioning procedure to follow. The cars do have VVT but its not as affective as it is on Hondas and Alfas.

 

[theduck]

Bens explanation of VVT

the vvt system in the 172/182 range is there simply to allow the renault engineers to run a wilder camshaft without any of the problems you would associate with larger overlap cams on a plenum with a classic speed density system.

The vvt system is a simple 1 step phasing operation which advances the inlet cam only by 16 degrees. In its resting (depahsed) status it sits with the valve events netting a zero overlap status. This gives a strong map signal and constant manifold vacuum at idle and low throttle angle, which makes smooth mapping at lower rpm and throttle angle easier, along with better emissions and economy.

As soon as you increase manifold pressure to 800mb+ and go above 1450rpm, the ecu will advance the cam. Its such a low rpm threshold because the cams are not that wild, but wild enough to cause problems at idle.

The kick at 5000rpm is simple the 'on cam' phenomenon where all operating parameters favourably meet and you get a sudden increase in volumetric efficiency.

and of the 5k kick

By no means is the 5k kick the result of any mechanical/electronic chance withing the engine system, whether that be mapping paremeters or valve timing.

I think to fully understand, a base understanding of the operating system of the vvt is needed. The vvt system employed on the clio is what we refer to as cam phasing, this is where the whole camshaft (inlet or exhaust or both) is advanced/retarded. This can be in a single step as it is in the clio (single stage 16 degree advance on the inlet), or variable. The camshaft is hollow and is used as a galley to feed the front pulley (called a phaser) with oil pressure, this pressure simply acts on vanes inside to rotate it in a desired direction, and returned under mechanical pressure. The cam does not always carry oil pressure, but a vvt switch is used, and is basically a plunder activated by 12 (grounded by the ecu (a lowside switch)) which allows the passing of oil from the lifter galley to an area of the cam bearings with holes that can feed the inside of the cam, which then passes through to the nose of the cam and into the pulley (phaser).

Variable setups (like the new 197) will use the same base components as what is used today, but instead of the vvt plunger being used as a switch, the same plunger has the ability to open and bypass oil to either side of the vanes in the phaser. By using a PWM signal, you can gain full control of the phaser to advance the cam in a near infinately variable curve vs rpm vs manifold pressure vs throttle angle etc.

Honda's Vtec system is a cam 'changing' system where the actual cam profile is changed in its entirety (hence the 3 lobes per cylinder), the actual 'timing' of the primary lobe remains the same at all times. And now with I-Vtec and VVTL-i the benefits of both phasing and changing is being used at the same time to build some monster VE (volumetric efficiency) curves.

Anyway, in the clio the cam sits in its dephased state until the required parameters are met. This is above 1450rpm and 800mb manifold pressure. When it is required though, the cam is phased and the cam timing effectively advances 16 degrees, at 6800rpm it is dephased again and power drops off like a stone. No official reason, but my thoughts are that they do it so you guys shift up once there is a loss of acceleration. The reason for that is because the stock pistons just fall apart with prolongned high rpm use.

The 5k kick is the result of a few natural phenomenons within the engine. At 5000-ish rpm VE suddenly reaches a higher %'age and the resultant torque increase gives you that wahey feeling. VE increases due to the cam comming 'on'. This term has nothing to do with VVT and is quite an old term, whereby the reference is to the rpm region that particualr engine/cam combo requires to process the valve timing events efficiently.

VE refers to volumetric efficiency, or the %'age of the cylinder that you can fill with fresh charge. For a 2ltr, thats 500cc per cylinder. If you can only fill that cylinder with 430cc's at peak efficiency (normally at peak torque point) thats 86% VE. The higher the VE on any engine, the higher the torque output at that specific RPM, and all engine tuning revolves around increasing or rather sustaining a good VE for as long as possible, and upto as high an rpm as possible.

Anyway, back on track. The clio with its advanced cam timing (phased) operates with an overlap value that is larger than when it is dephased (infact it has no overlap when depahsed). This overlap is part of cam design basics, and larger overlap periods are used to help generate higher VE's via scavenging and inertia ramming. At 5000 rpm the natural effects of the port velocity and pulse tuning al reach a level where they start to actively enhance the torque production with the valve timing it is running. Put in a wilder cam and it will push the 'kick' higher up if nothing else changes, but lower rpm efficiency will loose out, and peak power will be pushed up the rpm scale, along with a higher peak bhp figure. To an extent, there will be a point where you can go wilder on the cam and just loose out everywhere as the engine system as a whole does not work with the cam profile you are running.

Not very clear sorry, basis is that the 5k kick is the result of natural phenomenons within the engine, primarily port velocities and pulse tuning harmonics.

 

[Aluco]

Thanks duck I'll send him the top one haha, hopefully shut him up !

It's going to birchdown or northwest performance I think :rasp:

 

[nick.]

Deffo has vvt, so I wouldn't get your belts done there personally.
Thanks for them quotes 'theduck' I understand what the VVT's purpose is now
Birchdown FTW, had my belts done there.

 

[sideways danny]

lot of bullshit in this thread. s**t on a stick

the "kick" is coming OFF lean burn/enonomy. nothing to do with coming "on cam", nothing to do with VVT.

It's ENTIRELY mapping, due to regulations for emissions, proven by proper mapping smoothing it out completely

 

[sideways danny]

oh, and the VVT acts to give a more stable idle as the stock cams are "relatively" wild for a standard car. without it you'd need a high idle, and i doubt it'd be happy at lambda 1.

 

[Dangerous_dave]

The 'kick in' is nothing to do with VVT. That's the car coming on cam.

VVT is much lower in the rev range.

you love it revels!
Suprised no one busted out the VTEC yo spammage

 

[Dangerous_dave]

lot of bulls**t in this thread. s**t on a stick

the "kick" is coming OFF lean burn/enonomy. nothing to do with coming "on cam", nothing to do with VVT.

It's ENTIRELY mapping, due to regulations for emissions, proven by proper mapping smoothing it out completely

i believe i have seen & experienced this in the flesh from one of jms maps on Matt wills trophy with stock cams. Impresive i tell thee



To the op it def has vvt lol
i'd be cautious about matey who might be doing ur cambelt, but maybe he is just un aware as such.

Could always get JMS/danny to do it if ur unsure

 

[cliosportap]

in ph1 s
the vvt open at 1600rpm and closes at 6500 rpm

 

[cat171]

..Suprised no one busted out the VTEC yo spammage

Whaaaat?? It's not like Vtec yo !

Tell me about the shift light


**I'm taking the pee, I don't expect anyone to reply to my comments**

 

[Dangerous_dave]

Whaaaat?? It's not like Vtec yo !

Tell me about the shift light


**I'm taking the pee, I don't expect anyone to reply to my comments**

:rasp:

i was reading through the manual for my 1.5dci van and it said something about the shift light in there - obviously a generic manual ...but for a split second i was like 'what my van has got a shift light yo!

 

[Lee-182]

another awesome CS thread

 

[jack_davey]

ive never read so much crap

 

[RSTuning]

lot of bulls**t in this thread. s**t on a stick

the "kick" is coming OFF lean burn/enonomy. nothing to do with coming "on cam", nothing to do with VVT.

It's ENTIRELY mapping, due to regulations for emissions, proven by proper mapping smoothing it out completely

The kick is NOT coming off lean burn at all, the car has the required fuel WELL before 5k. It's actually down to the CL-OL delay TIME and not set rpm when it goes from lambda 1 to x:1 based on ms of injection on the main VVT ON map. VVT control is based on RPM, switched on at 1500rpm and above 457 mbar and back off at 6601 (ph1 map). A couple of degrees advance in the OE map also helps to give the "kick". There can also be a big influence based on the IAT as they r****d the ignition far too early IMO. Lots of the info that Ben posted is pretty good actually but so many people have a different take on things. In short it's pretty much hitting the peak VE of the engine and making power how it should.

 

[Will.]

I love these vtec threads.

Even a 1.2 yaris has vvt, dont think that has vtec y0

 

[Mark One]

the "kick" is coming OFF lean burn/enonomy. nothing to do with coming "on cam", nothing to do with VVT.

This

You can see it clearly with a standard car on the dyno and an AFR plot. They are lean up till 5k then richen up to make the power.

 

[Lee-182]

I personally think its the turbo Yo

 

[Aluco]

All I wanted was confirmation that they had VVT, admin can lock this now if they so wish before the Vtec kicked in yo pics start flowing.

 

[Earpl]

mine just kicked in yo. + they dont go "on cam".... as theres only one set of followers