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How good is VVT

how good is the vvt on the 172.. (Variable Valve timing...)

If you are so inclined - try this little exeriment and report back...

remove the plastic engine cover (four Torx bolts) screwdriver and torx bit is in the spare wheel tool kit....

at the cam end of the engine you will see a 2 wire connector goint to the vvt actuator vavle.. (there is a circle the size of a 2 pence piece goint into the head)

unplug it - you have disabled vvt..
no go for a drive and let me know the results


hmm, what results did you get?
surely the increase in overlap at high rpm as better than keeping the timing the same all throughout.
i will try tomorrow, but its 11 now, so i have to im on the dyno tomorrow so ill have a go and report back, before and after the new viper kit is added.

Its pretty handy having a dad who is chairman of the HKAA, who incedentally have a RR!!!

Hi Ben.. errrrrr, well... not a lot to report actually, a very quick test revealed nothing different really

it may be noticable with a dyno or on fuel consumption, but I am baffled.

I would be interested to know your findings.

I have not spent much time on this, but first result was nondescript

I am not even sure at which point the vvt kicks in.. ??

I will hook up an led to the actualtor to see at what rpm it activates.. the clio cup racers (Actually the mechanics) I have talked to seem to believe it comes in at about 1200 Rpm !!. and is really used for better idle.

will need to look at this further


will post the results tomorrow.
i personally cant tell when the vvt kick in, its more like the cam comming on.

oh well, no doubt well be dissapointed. I could have a look at it with the special renault diagnostic equipment we have here? anything cool you would like me to check?

oh, and from your experience, what sort of A/F ration should i be running on the RR? we dont have much diagnostic equipment at the RR to see what happening with the engine, so a a/f meter is one of the basic thing we can use. well, we could bring along the diagnostic laptop, but i would have to see what it can check on the move.

Hi Ben,

the norm is for full throttle look for about 5% that will keep the engine safe. When Nick Hill tested his superb airbox system, it was found that the mix was leaning out to unsafe quantities at WOT.. better watch that one.! as for other techy stuff.. I wil sell ya me mother if ya can get the wiring details - or better still the service cd....

Geoff, the cam certainly come on at about 5k, I too thought this was the vvt.. but at the moment I am not convinced.. as Ben says, it feels more like coming on cam than anything..

will do some more research into it when the rain stops !.


Oh Ben,

one major point.. if your mods cause leaning out at the top end.. be very careful.. you CANNOT add a fuel pressure reg (ie Rising Rate) to compensate due to the non return system.

the Pressure MAY be adjustable electronically in the integrated reg on the fuel pump in the tank.

but, again, I need the diagrams to be able to deduce that

If you can get the diagrams, AND the reg is adjustable electronically, it will be a fairly easy microprocessor add on to up the fuel pressure at WOT.

A good test you can do please... If possible hook up a fuel pressure guage into the injector feed rail and tell me if the pressure remains constant.. (I think it will) but it is marginally possible that the ecu has control over it.. (again, I doubt it though)

Cheers M8...


Your abbreviations are beyond me. what WOT?

As for the fuel pressure test, ill have to see if GTi engineering have a fuel pressure guage to test it. And do you mean hook it up to the fuel entry pipe on the fuel rail?

Also, 5% what? What is the %tage of? and is it 5% @ full throttle, throughout the rev range?

Any other little tip you could give me on how to drive the car on the rollers? gear etc.

in return, ill spend the morning chasing the service CD.

Yo Ben m8.

Your abbreviations are beyond me. what WOT?

Wide Open Throttle - this is often where the efi system uses a simple look up table and not math !!.. the Lamda is bypassed too.. this can only be altered by reprogramming the ecu or adding fuel pressure (or more fuel)... below WOT, the sensors are active and Stoichiometric ratio is maintained - so dont worry about readings through the range..

As for the fuel pressure test, ill have to see if GTi engineering have a fuel pressure guage to test it. And do you mean hook it up to the fuel entry pipe on the fuel rail?

either, its the same supply

Also, 5% what? What is the %tage of? and is it 5% @ full throttle, throughout the rev range?

5% co - 5-7 is kewl !.. see above for through the range.

Any other little tip you could give me on how to drive the car on the rollers? gear etc.

Do the tests in 4th gear.. (closest to 1:1 overall gear ratio..) accelerate smoothly, watch for wheelspin and drift - the front of the car moving sideways.. ALWAYS check that... the rest depends on if the roller is constant load or operator applied. have all the ignition diags hooked up first (ie Krypton) - if you have a problem during the run.. check the Kryp readings too..

in return, ill spend the morning chasing the service CD.

What more could I ask Sir
  BMW 320d Sport

Ben I thought youd know that WOT= Wide Open Throttle.

Joe, Ive got a dorky interest in this weird concept of not having a return to the tank...does the pump have its own fly by wire regulator controlled by the engine management or something?

Thinking about the normal system, I suppose it is a bit archaic to have the fuel pressure regulator hooked up to the manifold going back to the wonderful world of carbs, vacuum advance etc!

BTW Ive had the ignition module out and wired it up, in the end I had to solder a pair of flying leads directly to the coil terminals. There was obviously an amp inside the body of the module but the space was all filled up with rubbery foam stuff - no user serviceable parts in other words!

Im out testing tonight to see if its working, Ill try different amounts of ignition r****d and see if I can feel it working.
Only problem is because its wired to work automatically when the gas is firing, its gonna be tricky finding a proving ground where I wont be interrupted

Hiya Nick..

the concept IS a bit wierd aint it

the pump UNIT (containing the reg) can sense the pressure in the single line.

as fuel is injected, the pressure would normally drop, but, as the pump has reserve quantity as a buffer, and, the speed of the pump and regulator pressure(we think) is instantaneously adjustable, it maintains a single line, no return, constant pressure.

for the tes.. take the activation wire to the unit and, if it sees 12v at activation, wire it to a switch to supply 12 volts.. if it grounds a circuit.. do the same through a switch to ground..

disarm the gas and drive along trying the switch in and out... that should tell you its working - although the effect will be minimall use the greatest r****d to test....

once you are happy its doing SOMETHING.. then hook it up as per normal... if you didnt get detonation before (although bloody hard to tell) you will be able to run more gas.. there will be no power benefit.. in fact a slight loss.. its the amount you can go up AND safeguad the engine from detonation (knock)

have fun M8 and report back.!


sorry, yes, Nick.. it IS controlled by the ECU I think.. it is possible that it has its own controller.. but that would fall outside renos strategy of combining everything including the rear wiper (seriously !) into the ecu..


cheers mate, ill just see how everything goes.

as for the fuel line, if i disconnect the fuel rail? or are you assuming that the pressure tester will allow fuel to pass through it? other wise is would be silly ...........oh god my brain is dead, ive been running around4 2 days solid and im tired....

if ithe pump is controlled byt the ecu, then i should be able to increase the base line pressure and add more fuel everywhere, more importantly @ WOT () and at peak power.....avoiding the running lean....but wont the lama system keep the rest of the running stoichiometric.

oh, we took the TB apart today, and the bloody spindle is huge!!!! a decent amount of flow could be gained by thinning the spindle, and porting the inlet mfold.

p.s. ill also be running the clio cup zorst.....

man, im gonna have to get superchips only people around here who can, to modify the serial maps so to increase fuelling. and were gonna have to have each ecu of every car checked by superchips in the UK, cause we dont wanna invalidate the warrenty (or cause expensive damage for ourselves), to tailor each one if needed, so its not a generic map, which is good for superchips i think,they have been very helpful.

use a tee piece in the supply to the gauge.. no probs..

the pump theory....... YEP!

the tb is often considered a culprit in flow dynamics.. dont be too sure its causing a problem.. the lumenition tbs with roller valves (NO SPINDLE !) are only showing 2 bhp at 285 !..... a mere non-entity..

Superchips. yep doos I would LOVE a prgrammer... get me the reno one and I will mod it LOL

  172 sport,

dont know about anyone else but thats just gone right over my head hope it all works out as if any improvements can be made im up for em

lumis roller barrel TBs are in theory good...however in practice there only a true advantage @ WOT (i like this abb now!) where there is no obstruction to flow,But if your usesing twin injectors per port (say shower type and down near the head toget better drivability) then pooling and acumulation of fuel droplets can form on the barrels at part throttle.

what is 2 @ 285?

I know you knew that....but as BT say, its good to talk!

I have come up (dunno if its original or not) with what i think is the perfect combination of a traditional butterflys tractability and a roller barrels balls out top end.

Imagine a rubber cylinder (thin rubber walls) now if you encircle it with your thumb and forefinger then squeese, the diameter of the tubes gonna get smaller right. bingo, a shape that reflects a venturi, restricts flow, no shaarp edges or steps etc etc. Combine this in a TB and you have almost perfect laminar flow. I just have to think of a way to squeese it evenly from all sides. The easiest way right now is the use of a camera style aperature (the ones made out of tons of plates, which slide at an angle to each other to create a circular hole) with the rubber (petrol resistant of course ) part of the TB body inside could just use a normal throttle linkage (the aperature works by sliding one plane) and then flow would be so smooth, tractable, perfect flow @ WOT etce etc.......what ya think?

BTW, im really knackered, that explains my typing skills.

oh, as far as the mod im doin goes, i will do each individually, first filter, add chip, tune, add zorst, tune. I can do this cause i have the development time. however, i cant when it comes to slapping them onto customers cars..they have to be plug and play, so im hoping to save the parameters of each stage, and hopefully itll be close enough to most cars not to cause a prob....leave it the tiniest bit ruch, just in case.


my email addy is
please leave not to remind me tomorrow (7 hours) to get he CD.....and exactly what it is you want...i may have to get the factory to email it.

I am absolutely convinced the VVt kicks in at 5000 on the Mk1, and I see no reason it would change for the Mk2.

In mine there is a definite kick at 5k, almost like a mini turbo effect, and the car would be a LOT slower of the VVT was absent....

is not such a boost, i can barely feel it!!!

but i will be testing the car on teh RR today with and without the VVt connected, we might be able to see on the graph where any switch is flipped.

is not such a boost, i can barely feel it!!!

but i will be testing the car on teh RR today with and without the VVt connected, we might be able to see on the graph where any switch is flipped.

dont you?

no, im in Hong kOng now, 7 hrs ahead of you guys, so its almost midday, and im working at renault.

capt, your right, the fuel reg and return valve is in the tank, just after the pump. so that mean only the fuel needed reaches the rail, but that must mean an amazing amount of pressure or flow to respeond so quickly.

i need to know exactly which diags you want, as there is only a fuel level indicator diag (the only fuel related diag) an nothing else. I was wondering what else i could do?

oh, and upon closer inspection to the F4R engine, its so basic, and there is still so much that they could have done to improve its power. Its got so many restrictions in the whole air flow through the entire engie, apart from the exhaust ystem which is ace, looks like they skimped on the ind system though.

yo capt!

i went on the rollers today, and its an outdoor dyno. Nice sunny day, didnt get time to pump up the tyres, let the engine bay cool a little etc, so want expectin its best, but it was for a base test.

But youll never believe it!!! as i pulled into the compound, a thunderstorm rolled in 4 ft behind me, i could see it in me mirrors!! and when i stopped, i could see the shiney rollers get all nice and wet!!!

well, we waited a bit and i went on when it was only a little drizzle, but after a damn smoking leaking diesel minibus!!!!!

anyway, i dont got traction control cause it just reved up nice and evenly (had to do 3rd gear cause there are only 2 towing eyes, so it couldnt be strapped down at its best, limited to 100mph) and the power at the wheels was 122bhp, so using a conversion factor of 0.72, about 166bhp....but just rough calculations though.

good thing is, it means that when we re test the clio witht he mods on, the gains are gonna be much higher and will help us sell better!

my abs warning light and sevice light were on after though, so i switched off and on, then it was ok.

bad news, the viper kit didnt fit cause it was designed for the MK1 which has a flexy TB to airbox pipe, the mk2 has rigid plastic. So i ordered a MK1 pipe. I hope its gonna fit on the MK2 TB, but i wouldnt see any reason for them to change the outer diameter of the you?

Ben m8 when youve installed the viper and rolling roaded it I would interested in the results. My cars running 121.5 at the wheels. And thats with superchip, viper + scorpion exhaust. So not too happy with that. Might put the standard induction system back on before the rolling road day to see what power I get at the rolling road.


itll be fitted tuesday or wednesday.

but 122 in the pouring rain, 98% humidity, thin hot air (3eg C!!!!),and tyres @ 28psi.

the engine has been ragged since day 1 though, its let out to mag for testing etc etc.

As capt said I suspect oe of my mods isnt doing the power any good. Just a case of finding it now hehe. What do you think of modding the standard induction system?. Fitting bigger bore piping + performance element + heatsheild it. Its just looking at the Mk1 induction system theres more capacity and more filter area for bettter flow than there is on the viper. The rolling road operater (spelling) mentioned that there was a flow restriction at the top of the rev range. Now it could be the filter or exhaust.