George K said:
See if he's got a dictionary n' all. :?
What's your 5K kick like?
See if he's got a dictionary n' all. :?
This is all very interesting, if you could talk to Ben, that would be brilliant, I think it'll be worth finding out more about the engine's characteristics, as knowing exactly what is going on inside the engine will help make informed decisions about induction tuning etc.
I have read in more than one place about the advanced timing at 5500 RPM in the F4R though, but I completely agree that there is a timing retardation, as you first stated, at the bottom of the rev range, this is undoubtedly to produce smooth running at low speeds and to help emmission testing at idle. I also completely agree that something happens with the induction system, as the valve is there for everyone to see, it explains why replacing the system, with say a Pipercross Viper, upsets the low-end torque.
I wonder how fitting a de-cat pipe affects the lamda sensor's oxygen reading and how this affects the fueling in turn. To find this out would be useful.
I have read in more than one place about the advanced timing at 5500 RPM in the F4R though, but I completely agree that there is a timing retardation, as you first stated, at the bottom of the rev range, this is undoubtedly to produce smooth running at low speeds and to help emmission testing at idle. I also completely agree that something happens with the induction system, as the valve is there for everyone to see, it explains why replacing the system, with say a Pipercross Viper, upsets the low-end torque.
I wonder how fitting a de-cat pipe affects the lamda sensor's oxygen reading and how this affects the fueling in turn. To find this out would be useful.
Have e-mailed Ben and hope he will respond directly onto the forum - probably not until the small hours!
One of the main reasons for the retarded inlet timing at the bottom end is to reduce the overlap so that the MAF does not see de-stabilising pressure fluctuations which completely wreck the idle quality - these disappear at higher rpm. (over 1,500). TPS management systems do not have this problem, but are not so well suited to all the niceties required for everyday road use and emissions/economy.
Even Ben is not clear on when the valve in the inlet system opens/closes - his testing has nearly always found it to be open! Perhaps someone could wire an indicator light into the solenoid circuit!
One of the main reasons for the retarded inlet timing at the bottom end is to reduce the overlap so that the MAF does not see de-stabilising pressure fluctuations which completely wreck the idle quality - these disappear at higher rpm. (over 1,500). TPS management systems do not have this problem, but are not so well suited to all the niceties required for everyday road use and emissions/economy.
Even Ben is not clear on when the valve in the inlet system opens/closes - his testing has nearly always found it to be open! Perhaps someone could wire an indicator light into the solenoid circuit!
at the call of George K
Since so many are interested in the true phenomenon of the '5k kick' I am more than willing to clear it up, its actually quite simple.
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.
If you have any specific questions, just ask.
Since so many are interested in the true phenomenon of the '5k kick' I am more than willing to clear it up, its actually quite simple.
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.
If you have any specific questions, just ask.
This explanation is brilliant, at long last, a definitive answer...Although it doesn't explain why Francois Ratinet, Renaultsport's powertrain manager, is quoted as saying "The old Clio (182) had just an on-off system - the timing switched 11 degrees at 5500 rpm..." in this month's EVO magazine.
I really like the explanation of 'Coming on cam' and 5000 RPM being the optimum engine speed for the cam profile, but personally, I think the kick is much better explained by there being another camshaft rotation at 5500RPM, the kick is so pronounced and violent, it has to be the result of a deliberate electro-mechanical switch of some sort. If it was simply the cam profile operating most efficiently at these revs, it would not be so sudden but would graduate to it's maximum VE and torque output (5250 RPM) and would feel just like a surge in torque around those revs.
I am left as confused as ever, because it is obvious you know what you are talking about but I can't bring myself to doubt the words of Renaultsport's powertrain manager or my own instincts.
Thanks.
I really like the explanation of 'Coming on cam' and 5000 RPM being the optimum engine speed for the cam profile, but personally, I think the kick is much better explained by there being another camshaft rotation at 5500RPM, the kick is so pronounced and violent, it has to be the result of a deliberate electro-mechanical switch of some sort. If it was simply the cam profile operating most efficiently at these revs, it would not be so sudden but would graduate to it's maximum VE and torque output (5250 RPM) and would feel just like a surge in torque around those revs.
I am left as confused as ever, because it is obvious you know what you are talking about but I can't bring myself to doubt the words of Renaultsport's powertrain manager or my own instincts.
Thanks.
That's cool, I've spoken to a guy that used to work for Renault, and he's going to find out from the guys that built the engines. So I'll know for sure. I didn't say I didn't believe you, I found what you said extremely informative, especially about the mechanics of operation of the camshaft rotation.
I don't believe everything I read in EVO either, but I did book a test drive after the strength of the Trophy reviews in EVO and other places, which then led me to buy one (the only car I would replace my 205 GTI with). So I use what I read to make my own informed decisions, and all I'm saying is, my mind's not made up on this one, yet.
It's clear there's a difference in the '5K kick' between absloutely standard cars, which is quite interesting, and indeed the subject of this whole thread.
I don't believe everything I read in EVO either, but I did book a test drive after the strength of the Trophy reviews in EVO and other places, which then led me to buy one (the only car I would replace my 205 GTI with). So I use what I read to make my own informed decisions, and all I'm saying is, my mind's not made up on this one, yet.
It's clear there's a difference in the '5K kick' between absloutely standard cars, which is quite interesting, and indeed the subject of this whole thread.
Sorry but doesn't this just mean that the phase shifter is non-operational before 1800rpm and above 6500rpm, so there is no valve opening overlap outside of this rev-range for low speed idle smoothness and near rev-limiter power-loss, but that the phase shifter is operational between these revs and can advance the timing further, say at 5500rpm?
If you say 'No, it's not possible', I'll believe you and never say another word about it. I'm actually a little past caring now, I was in a bad mood this morning and found waiting for the 5K kick a little annoying and I feel I've been over-rating it.
Those new Shelby GT500's are only $40,000, you could ship one over for £28,000, I reckon. Doubt there's much on this earth that would be more of a power fest for that money. And they go round corners pretty well too, considering the live rear axle.
Thanks for all your input to this thread, Ben. I won't be doubting an engine tuner again, I'll stick to my buildings.
If you say 'No, it's not possible', I'll believe you and never say another word about it. I'm actually a little past caring now, I was in a bad mood this morning and found waiting for the 5K kick a little annoying and I feel I've been over-rating it.
Those new Shelby GT500's are only $40,000, you could ship one over for £28,000, I reckon. Doubt there's much on this earth that would be more of a power fest for that money. And they go round corners pretty well too, considering the live rear axle.
Thanks for all your input to this thread, Ben. I won't be doubting an engine tuner again, I'll stick to my buildings.
Steve, certainly done ever stop questioning a tuner.
Just because they carry the title 'tuner' or are in the industry, by no stretch of the imagination, does this actually mean they understand the most basic principals of engine development or operation. The best way to find a good tuner is to question them, and keep questioning them, if they say something stupid, or give a uselessly vague answer, then go somewhere else. There are alot of pretenders out there.
Anyhow, the comment you just gave pretty much perfectly answers your own question, if i read it correctly. The Solenoid is not operational between those areas yes, thus the cam does not advance outside those areas. However, by simple reasoning you can say that if it does stay dephased at between those rpm points, then it will be on low load/cruise conditions. Once you are at full throttle, the cam CAN advance from as low as 1800rpm. Therefore, if you are at WOT from as low as that, the ECU will trip the soleniod, phase the shifter and you will be running with overlap from as low as the specified lower limit rpm point.
And in performance terms, there is no reasoning why any manufacturer (apart from honda) should sell on the point of a heavily defined power jump. All this simply means is that you are loosing substantial torque and drive/acceleration below that 'kick' point. So, if it is electronically controlled, why? what the point, you'd be faster without it.
Just because they carry the title 'tuner' or are in the industry, by no stretch of the imagination, does this actually mean they understand the most basic principals of engine development or operation. The best way to find a good tuner is to question them, and keep questioning them, if they say something stupid, or give a uselessly vague answer, then go somewhere else. There are alot of pretenders out there.
Anyhow, the comment you just gave pretty much perfectly answers your own question, if i read it correctly. The Solenoid is not operational between those areas yes, thus the cam does not advance outside those areas. However, by simple reasoning you can say that if it does stay dephased at between those rpm points, then it will be on low load/cruise conditions. Once you are at full throttle, the cam CAN advance from as low as 1800rpm. Therefore, if you are at WOT from as low as that, the ECU will trip the soleniod, phase the shifter and you will be running with overlap from as low as the specified lower limit rpm point.
And in performance terms, there is no reasoning why any manufacturer (apart from honda) should sell on the point of a heavily defined power jump. All this simply means is that you are loosing substantial torque and drive/acceleration below that 'kick' point. So, if it is electronically controlled, why? what the point, you'd be faster without it.
Couldn't agree more with that last paragraph, if you are feeling a sudden surge (and you're not activating a second inlet cam as in a VTEC or similar) there must definitely be a loss of potential torque below the surge, I guess at optimum efficiency any particular camshaft/electronics configuration should deliver a smooth rise in power with revs up to a certain point where the cylinders aren't as efficient due to thermal efficiency, VE, etc.
Anyway...I was a passenger in my car for the first time today (since the test drive) and the 5K kick (i'm getting really sick of typing that now!) wasn't nearly as defined as I thought, but as always, being a passenger, it felt bloody quick and a really solid ride. My old boss, the test pilot, who's also a complete car nut and has driven some real exotica, was enthralled by the car and says he wants one. We drove it on some really great roads around Fulking and Steyning that he knew well and he said that was as fast as anything he'd driven around those roads, and he's had an S2000, a 350Z and an M3 on the same roads. He was really blown away, and admitted he was a bit biased against french cars before, expecting the thing to feel a bit flimsy and rattly, but he's not now.
Shit, I'm really sorry... (offtopic)
Anyway...I was a passenger in my car for the first time today (since the test drive) and the 5K kick (i'm getting really sick of typing that now!) wasn't nearly as defined as I thought, but as always, being a passenger, it felt bloody quick and a really solid ride. My old boss, the test pilot, who's also a complete car nut and has driven some real exotica, was enthralled by the car and says he wants one. We drove it on some really great roads around Fulking and Steyning that he knew well and he said that was as fast as anything he'd driven around those roads, and he's had an S2000, a 350Z and an M3 on the same roads. He was really blown away, and admitted he was a bit biased against french cars before, expecting the thing to feel a bit flimsy and rattly, but he's not now.
Shit, I'm really sorry... (offtopic)
I asked the following question on the renaultsport forum, thought I would post the answer here for those who aren't members. Doesn't really say anything we (GeorgeK and BenR) didn't already know. It's worth reading for the response to the centre console plaque though, this was to take the piss out of his previous response to a question where he stated one of the differences between the cup and trophy was a numbered plaque on the centre console.
Trophy 298/500 asked VVT in the F4R
I have a Clio Trophy. Could you please explain exactly what happens in my engine at 5500rpm, apparently there is a timing change actuated by a camshaft rotation of 11 degrees but there is also a timing retardation at 1500rpm and there seems to be no evidence of camshaft phaser operation after this point. This issue has caused much debate amongst enthusiasts and engineers alike, so only an in depth and accurate explanation will suffice. Could you also please send me the numbered plaque you mentioned for my centre console as this was missing upon delivery of my car.
Allen Collen responds
The solenoid valve is closed at rest. It authorises the passage of oil to control the phase shifter in line with the operation of the engine: - if the engine speed is between 1,800 and 6,500 rpm, - if the throttle potentiometer is not at no-load NOTE: if the solenoid valve is jammed in the open position this will result in an unstable idle and the pressure in the manifold at idle will be too high. This affects the mechanical timing of your inlet valves and the other mechanical components: pistons / exhaust valves. The result will affect the volumetric efficiency of the engine, hence a change to the fuel and ignition maps. The solenoid only opens or closes as detailed above and it is not continously variable. Regarding the plaque I understood my colleague was trying to manage a solution? I'll check with them next week, and let you know. :lol:
Trophy 298/500 asked VVT in the F4R
I have a Clio Trophy. Could you please explain exactly what happens in my engine at 5500rpm, apparently there is a timing change actuated by a camshaft rotation of 11 degrees but there is also a timing retardation at 1500rpm and there seems to be no evidence of camshaft phaser operation after this point. This issue has caused much debate amongst enthusiasts and engineers alike, so only an in depth and accurate explanation will suffice. Could you also please send me the numbered plaque you mentioned for my centre console as this was missing upon delivery of my car.
Allen Collen responds
The solenoid valve is closed at rest. It authorises the passage of oil to control the phase shifter in line with the operation of the engine: - if the engine speed is between 1,800 and 6,500 rpm, - if the throttle potentiometer is not at no-load NOTE: if the solenoid valve is jammed in the open position this will result in an unstable idle and the pressure in the manifold at idle will be too high. This affects the mechanical timing of your inlet valves and the other mechanical components: pistons / exhaust valves. The result will affect the volumetric efficiency of the engine, hence a change to the fuel and ignition maps. The solenoid only opens or closes as detailed above and it is not continously variable. Regarding the plaque I understood my colleague was trying to manage a solution? I'll check with them next week, and let you know. :lol:
Nik said:I have no idea what that all means. Unfortunately I dont see a TechyMechanicSpeak > English option on Babelfish
Don't play dumb, you probably know more than this Renaultsport 'expert' about the mechanics of the Trophy. He's just regurgitated the textbook answer about the phase shifter operation. A solenoid is a lump of ferrous metal that drops in and out of an electromagnetic coil in response to an electric charge, a switch in other words, which in turn allows the passage of oil down the hollow camshaft which puts oil pressure on a mechanism that rotates the camshaft thereby rotating the cam lobes upon the camshaft so that they operate the rocker arms sooner in the crankshaft rotation or later, thereby advancing or retarding the inlet and exhaust valve opening, meaning that at higher engine revolutions the valves can operate more efficiently for the higher engine speeds, greater gas-flow etc. while also being able to operate smoothly at low rpm without the advance, or with retardation. Anyway, I only included the dull and uninformative text because I thought the plaque thing was funny.
What's Babelfish?
What it means is that the inlet cam is retarded until 1,800 rpm, then advances (iirc) by 15 degrees into a 'normal' postion, but then is retarded again at 6,500 rpm. He is also saying that this only will happen if the throttle is not closed - presumably on lift off.
The point about the solenoid being jammed open, is that if someone finds a way to keep the cam advanced all the time, then the idle and emssiions will be all over the place. The problem is that ordinary road car management systems work on inlet manifold vacuum(actually rather like an SU carburettor) and can not cope with the pressure fluctuations casued by more extreme cam timing. Most high performance management systems mainly work from throttle position, so are not affected in the same way - iti s just that they seem to much more difficult to set up for low emissions with a cat.
Why it retards at the top end is not clear - possibly a reliability issue. Would be interesting to find out if a clever re-map(per) could raise the retard point from 6,500 to say 7,000. Wonder if anyone has aever tried to see if there is a benefit, or if the engine is restricted in other ways?
The point about the solenoid being jammed open, is that if someone finds a way to keep the cam advanced all the time, then the idle and emssiions will be all over the place. The problem is that ordinary road car management systems work on inlet manifold vacuum(actually rather like an SU carburettor) and can not cope with the pressure fluctuations casued by more extreme cam timing. Most high performance management systems mainly work from throttle position, so are not affected in the same way - iti s just that they seem to much more difficult to set up for low emissions with a cat.
Why it retards at the top end is not clear - possibly a reliability issue. Would be interesting to find out if a clever re-map(per) could raise the retard point from 6,500 to say 7,000. Wonder if anyone has aever tried to see if there is a benefit, or if the engine is restricted in other ways?
From Hitchhiker's Guide to the Galaxy - a small fish you place in your ear which translates any known language for you.
Also proves the non-existence of God. Something along the lines of:
You cannot prove God exists because proof denies faith and without faith, God is nothing. However the Babel Fish is such a useful creation that it proves God exists, and therefore (because proof denies faith) he doesn't. God "vanishes in a puff of logic"
Douglas Adams was a genius.
Good luck waiting for your plaque....
