speed limiter in dig-s
- Thread starter mik
- Start date
I've seen some Micras tuned with unichip:
http://www.unichip.us/
http://www.facebook.com/GettunedTuningService?ref=stream
But it might be costly... balanced to the max speed you'll get, but hey! You never know.
http://www.unichip.us/
http://www.facebook.com/GettunedTuningService?ref=stream
But it might be costly... balanced to the max speed you'll get, but hey! You never know.
Speed limiter from what u say can't be an issue if its as high as u say, limit for cruise control to be set at is much much lower than that.
I would not go for a re-map unless you have a friend with access to equipment, from what I heard most places that do the mapping only seem good for cars that lots of people have already re-mapped, take something new to them , something they never mapped before they can make a right hash of it...........
Sent from BlackBerry 9790 using Tapatalk
I would not go for a re-map unless you have a friend with access to equipment, from what I heard most places that do the mapping only seem good for cars that lots of people have already re-mapped, take something new to them , something they never mapped before they can make a right hash of it...........
Sent from BlackBerry 9790 using Tapatalk
I didn't want to start filling up the tech topic, but its interesting that the boost drops to .1/.2 bar from .4bar when it hits a speed.
Was this a sudden change or was it gradual as you plough through the revs? I would have thought this is intended and managed by the air recirc solenoid rather than the supercharger running out of puff....? Can I assume that in any other gear, >5000rpm still produces ~.4 bar of boost?
I suspect there are a lot of things that could be tweaked in the ECU's programming to release more power from the DIG-S motor before any physical changes (IE change in pulley size) are needed such as controlling the on/off periods of the supercharger, control the recirc valve and valve timing (re: maybe reducing the amount of time the inlet valve is open on the compression stroke) to releasing more power top end to gain more top end speed...
Depends on the performance increase, releasing the top end speed restriction maybe of interest for drag racing, but then I am sure you would need more than 1/4 mile to wind the Micra up to those sorts of speeds anyway so maybe a moot point.
*boost pressure values corrected
Was this a sudden change or was it gradual as you plough through the revs? I would have thought this is intended and managed by the air recirc solenoid rather than the supercharger running out of puff....? Can I assume that in any other gear, >5000rpm still produces ~.4 bar of boost?
I suspect there are a lot of things that could be tweaked in the ECU's programming to release more power from the DIG-S motor before any physical changes (IE change in pulley size) are needed such as controlling the on/off periods of the supercharger, control the recirc valve and valve timing (re: maybe reducing the amount of time the inlet valve is open on the compression stroke) to releasing more power top end to gain more top end speed...
Depends on the performance increase, releasing the top end speed restriction maybe of interest for drag racing, but then I am sure you would need more than 1/4 mile to wind the Micra up to those sorts of speeds anyway so maybe a moot point.
*boost pressure values corrected
OP
OP
will have to do a video it seems that the boost drops are different in each gear. at 195kmh it drops suddenly. the other gears are more easing out at the rev limiter. while in fourth gear it holds the boost till 6000rpm in third it seems to have a curve which drops slightly earlier.
im no high speed freak im just curios
but i feel safer if the limiter wasnt there as we have unlimited speed on most autobahn parts here, and when the car suddenly breaks without any brake lights at 200kmh i dont feel safe cause people tend to tailgate a lot here.
im no high speed freak im just curios
but i feel safer if the limiter wasnt there as we have unlimited speed on most autobahn parts here, and when the car suddenly breaks without any brake lights at 200kmh i dont feel safe cause people tend to tailgate a lot here.to be honest, there are very few people with the "luxury" to be able to push their motor faster than the speed limit.
You are after all, talking >120mph (in our money!), in a Micra lol
Be interesting to see a vid of a vid of each gear from 1 or 2000rpm all the way up to the red line to see how it behaves. In theory it should just be static as the supercharger should have enough puff to be able to supply the engine at full boost all the way through the rev range. Maybe a small leak on the recirc/bypass valve, or programmed to slightly open the valve...
You are after all, talking >120mph (in our money!), in a Micra lol
Be interesting to see a vid of a vid of each gear from 1 or 2000rpm all the way up to the red line to see how it behaves. In theory it should just be static as the supercharger should have enough puff to be able to supply the engine at full boost all the way through the rev range. Maybe a small leak on the recirc/bypass valve, or programmed to slightly open the valve...
frank
Club Member
they use the d-b-w for cruise control and traction control, so why not the speed limiter eh
and with a turbo you can easily govern the boost level with the throttle pedal (less so on a S/C tho i guess)
OP
OP
ok so today i drove on the autobahn ( no speed limits yay! )
i reved each gear from 2nd to 4nd into the limiter. each gear the drop is similar curve.
this is what i got.
boost drop:
)i reved each gear from 2nd to 4nd into the limiter. each gear the drop is similar curve.
this is what i got.
boost drop:
- @5500rpm full boost approx .45bar
- boost drop starts after 5500rpm
- until it hits the rev limiter (which is between 6000-6200rpm)
- at 6200rpm the boost is .3bar
Interesting...
I remember when I had the Primera, the power graph was fairly similar, started to dip at 3krpm before climbing again. According to a number of people it was programmed that way to encourage people to change gear lower down, and people who had re-maps done the power increase was smoother and that middle drop gone.
IF true, I wonder if Nissan have repeated the same "function". I would not have thought the charger would be running out of puff on our engines, given that its max rpm is not reached, and the charger was designed for 4 pot 1.4's
I remember when I had the Primera, the power graph was fairly similar, started to dip at 3krpm before climbing again. According to a number of people it was programmed that way to encourage people to change gear lower down, and people who had re-maps done the power increase was smoother and that middle drop gone.
IF true, I wonder if Nissan have repeated the same "function". I would not have thought the charger would be running out of puff on our engines, given that its max rpm is not reached, and the charger was designed for 4 pot 1.4's
Forgive the thread necromancy, but it's kind of relevant to my own issues at the moment.
First question: I don't supposed anyone else has dyno'd a 1.2 NA at all? I'm not really sure how I'd go about doing mine...
Anyway, I managed to con dropbox into showing me that image even though it's broken here, and I think there's some misinterpretation going on, confusing the torque and power curves... what I see is:
1650-2500, torque rising fairly steeply
2500-3400, torque rising more gently
3400-5400, torque relatively stable, allowing for some momentary variation for various reasons (quite possibly it's supposed to cap at 149nm, with a gearbox rated for no more than 150 constant, and the wobbles we see between 144 and 152 are nothing more than that... wobbles)
5400-5600, very steep torque fall-off
5600-6000, medium grade torque fall-off
(bearing in mind it's *supposed* to peak at 4400rpm...)
as well as
1650-5050, power rising in a fairly steady fashion, with some slight changes in gradient, both for calculated ("normalised"?) crankshaft output, and for directly measured wheel output
5050-6000, crank output fairly stable, with a "wobble" of no more than 5hp (or +/- 2 to 3hp vs its initial state at 5050-5200). Never falls below 108-109, and is at 110+ on the whole.
...and indeed, 5050-5500, wheel output fairly stable around 84whp, with a slight fall 5500-5600 to a reasonably well maintained plateau of 76~78whp to the redline (the difference caused by increasing and quite strong gearbox/shaft drag, stealing a full 26hp at the redline).
*Doesn't* look like there's any great power loss happening, there's 6-8whp lost between 5400 and 5600 (or a little under 10%), but that's not particularly significant in terms of "easing off towards the limiter" and is still higher than what you get from any rpm below about 4750, so won't be a major impediment to max speed. The 110hp level, and the hard torque drop-off needed to achieve that, is either a function of what would otherwise have been a more natural looking torque curve that just happened to end up falling there, or in order to hit certain tax bands in different countries where it's sold (e.g. a lot of cars that cover the French market amongst others which don't care as much end up with cars exhibiting 54, 59, 64, 68, 74, 80, 86, 106~113hp... etc... as with CO2 emission figures that just sneak within the upper limits of each band as found in the UK and some others, those are the horsepower figures that just about sneak within certain french bands (as it's based on CO2 x HP with some balancing coefficients). Depending how you cut it, the DiG-S has between 106 and 113 PS/HP/bhp/etc (...though to be technical, the French system works on kW anyway), so they might have needed to mute the output right at the very top end to give what is, on average, a flat 79.9kW from about 5000 to 6000rpm (and, with its 99g/km emissions, a very close fit for a low tax band) instead of allowing it to organically peak upwards a little further in that really rather narrow rev band. It may even be that the "peak" torque/power rpms quoted are for the unlimitered engine, even though the figures at those peaks are the ones developed with the limiters in place.
A 5th gear graph would basically show the same curve up to the high 4000s, then a very, very steep drop from, say, 4995 to 5005... (or given the published gearing / tyre size specs, and assuming it is actually 195.0km/h not 5000.0rpm, from 4947 to 4957... with a +/- variability of about 0.2km/h...). You are still more-or-less accessing the full available engine power, it's just that you have to sit right on that limiter in order to do so.
I wonder what it's for? If it's to protect tyres that may only be rated for 190km/h, then surely it should be set to 190. If it's for protection of higher-rated ones, the next step up is 210, which the car would only reasonably reach down a steep hill (110hp is good for maybe 200k, but I doubt you'd see 210 on the flat), and that speed is pretty close to the terminal velocity you'd reach by dropping it out of a plane with a heavy weight in the nose, so it'd be entirely fair to set a 209k limiter to ensure it never exceeded that.
Maybe it's to stop the gearbox from overheating. 26hp (nearly 20kw) is an awful lot of heat to dissipate through a relatively small amount of metal, even with all the air that will be flowing over it. Consider the effect that a domestic 2kw heater has... then imagine plugging in 10 at once. And the figure would only get higher as the speed went up - consider that this chart is for 4th gear, not 5th, after all, and the drag is mainly down to how fast the road wheels are turning more than the engine itself. The wheels are permanently coupled to the box, but the engine can be decoupled. Alternatively, it might be to avoid too easily overheating the charger; you're unlikely to want to slam along at 5000-6000 in 4th that much when you can go about as fast in 5th (terrain permitting), but you may be tempted to do so in top gear.
The only other thing I can think of is that maybe it's to prevent accidental overspeeding of the engine with enthusiastic downshifts, when you're already going faster than you otherwise would be able to achieve on an upshift. 195k in 4th works out as basically 6250rpm, which may indeed be where the limiter actually sits... or not that much above it to be particularly significant - in fact, the speed lost during the gearchange itself, and in the split second where the ECU detects the slight overspeed and cuts all power for a few revolutions, would be enough to bring it down to 6100~6200. So if the car is electronically topped out at 195k in the "cruising" gear, you can't absent-mindedly bang it down into 4th to try and get more speed for passing or hill climbing and end up over-revving it as a result.
Similarly I'm wondering if that might have been why the one I've experienced was implemented. The mph/1000rpm figure worked out from ratios and tyres puts it at an entirely ludicrous 99mph on the 6900rpm limiter in 3rd gear (something which I'm not sure if I want to test), or 159.7km/h. The engine being less powerful and more revvy, the temptation might be there to drop down not only from 4th but also 5th gear into 3rd should the road rise sharply and suddenly... and there's always that risk of an, ahem, "typical" :-/ Micra driver getting 3rd and 5th confused when shifting up from 4th (though quite what at least 50% of that contingent would be doing at 100mph is anyone's guess). Limit the thing at 160km/h or even 165km/h (which is what the machine at least *claims* it's achieving - judging the speedometer and elective limiter against roadside laser readout machines, it seems a bit optimistic even at low speeds), and the risk of exploding the engine with an unwise gearchange is banished. If you're very determined, it might briefly peak near to 7200, but in practice it's unlikely to exceed 7000...
(That said, the one and only time I've managed that sort of mistake myself was slipping up on a 3rd-to-4th shift and getting 2nd. I must say, Vauxhall build their engines quite tough; despite a 6000rpm limiter, and my reaching for the shift quite close to that in 3rd, with the rev needle going off the end of the 0-to-8 scale for several seconds, it seemed to withstand the ordeal with no obvious damage...)
This would still be an annoying and rather dumb thing to be saddled with, but I could at least see the logic of it if so. The numbers are just too convenient, with the limiter in a higher gear(s) being a mere fraction higher than the rev-limited max speed in a lower one for both cars, despite the different power outputs and gear ratios.
(Certainly the tyre explanation/gearbox explanations don't make much sense for the lower powered car, as it's probably got the exact same box just with two slightly altered ratios, and the tyres are largely the same as well. 170km/h (R) rated rubber tends to be full winter spec; summers and all-seasons are rarely found claiming less than 190km/h (T) capability, and I don't think I've ever seen or fitted anything with less than an "S" (180k) code)
Also wonder if the gaps between 3rd/4th and 4th/5th on the NA being relatively narrow and almost the same as each other is of any significance...
FWIW on that chart, it also shows that the NA's max power is developed at just 3900rpm in the DiG-S, and its max torque is exceeded at all revs above 1950rpm, so it's certainly not a car that's hurting for power in any way. You can pretty much cap yourself at 4000 (or about 4150 in 5th) and drive it like an NA with effectively much lower gearing, only breaking out the full post-4k drama when you really need to...
First question: I don't supposed anyone else has dyno'd a 1.2 NA at all? I'm not really sure how I'd go about doing mine...
Anyway, I managed to con dropbox into showing me that image even though it's broken here, and I think there's some misinterpretation going on, confusing the torque and power curves... what I see is:
1650-2500, torque rising fairly steeply
2500-3400, torque rising more gently
3400-5400, torque relatively stable, allowing for some momentary variation for various reasons (quite possibly it's supposed to cap at 149nm, with a gearbox rated for no more than 150 constant, and the wobbles we see between 144 and 152 are nothing more than that... wobbles)
5400-5600, very steep torque fall-off
5600-6000, medium grade torque fall-off
(bearing in mind it's *supposed* to peak at 4400rpm...)
as well as
1650-5050, power rising in a fairly steady fashion, with some slight changes in gradient, both for calculated ("normalised"?) crankshaft output, and for directly measured wheel output
5050-6000, crank output fairly stable, with a "wobble" of no more than 5hp (or +/- 2 to 3hp vs its initial state at 5050-5200). Never falls below 108-109, and is at 110+ on the whole.
...and indeed, 5050-5500, wheel output fairly stable around 84whp, with a slight fall 5500-5600 to a reasonably well maintained plateau of 76~78whp to the redline (the difference caused by increasing and quite strong gearbox/shaft drag, stealing a full 26hp at the redline).
*Doesn't* look like there's any great power loss happening, there's 6-8whp lost between 5400 and 5600 (or a little under 10%), but that's not particularly significant in terms of "easing off towards the limiter" and is still higher than what you get from any rpm below about 4750, so won't be a major impediment to max speed. The 110hp level, and the hard torque drop-off needed to achieve that, is either a function of what would otherwise have been a more natural looking torque curve that just happened to end up falling there, or in order to hit certain tax bands in different countries where it's sold (e.g. a lot of cars that cover the French market amongst others which don't care as much end up with cars exhibiting 54, 59, 64, 68, 74, 80, 86, 106~113hp... etc... as with CO2 emission figures that just sneak within the upper limits of each band as found in the UK and some others, those are the horsepower figures that just about sneak within certain french bands (as it's based on CO2 x HP with some balancing coefficients). Depending how you cut it, the DiG-S has between 106 and 113 PS/HP/bhp/etc (...though to be technical, the French system works on kW anyway), so they might have needed to mute the output right at the very top end to give what is, on average, a flat 79.9kW from about 5000 to 6000rpm (and, with its 99g/km emissions, a very close fit for a low tax band) instead of allowing it to organically peak upwards a little further in that really rather narrow rev band. It may even be that the "peak" torque/power rpms quoted are for the unlimitered engine, even though the figures at those peaks are the ones developed with the limiters in place.
A 5th gear graph would basically show the same curve up to the high 4000s, then a very, very steep drop from, say, 4995 to 5005... (or given the published gearing / tyre size specs, and assuming it is actually 195.0km/h not 5000.0rpm, from 4947 to 4957... with a +/- variability of about 0.2km/h...). You are still more-or-less accessing the full available engine power, it's just that you have to sit right on that limiter in order to do so.
I wonder what it's for? If it's to protect tyres that may only be rated for 190km/h, then surely it should be set to 190. If it's for protection of higher-rated ones, the next step up is 210, which the car would only reasonably reach down a steep hill (110hp is good for maybe 200k, but I doubt you'd see 210 on the flat), and that speed is pretty close to the terminal velocity you'd reach by dropping it out of a plane with a heavy weight in the nose, so it'd be entirely fair to set a 209k limiter to ensure it never exceeded that.
Maybe it's to stop the gearbox from overheating. 26hp (nearly 20kw) is an awful lot of heat to dissipate through a relatively small amount of metal, even with all the air that will be flowing over it. Consider the effect that a domestic 2kw heater has... then imagine plugging in 10 at once. And the figure would only get higher as the speed went up - consider that this chart is for 4th gear, not 5th, after all, and the drag is mainly down to how fast the road wheels are turning more than the engine itself. The wheels are permanently coupled to the box, but the engine can be decoupled. Alternatively, it might be to avoid too easily overheating the charger; you're unlikely to want to slam along at 5000-6000 in 4th that much when you can go about as fast in 5th (terrain permitting), but you may be tempted to do so in top gear.
The only other thing I can think of is that maybe it's to prevent accidental overspeeding of the engine with enthusiastic downshifts, when you're already going faster than you otherwise would be able to achieve on an upshift. 195k in 4th works out as basically 6250rpm, which may indeed be where the limiter actually sits... or not that much above it to be particularly significant - in fact, the speed lost during the gearchange itself, and in the split second where the ECU detects the slight overspeed and cuts all power for a few revolutions, would be enough to bring it down to 6100~6200. So if the car is electronically topped out at 195k in the "cruising" gear, you can't absent-mindedly bang it down into 4th to try and get more speed for passing or hill climbing and end up over-revving it as a result.
Similarly I'm wondering if that might have been why the one I've experienced was implemented. The mph/1000rpm figure worked out from ratios and tyres puts it at an entirely ludicrous 99mph on the 6900rpm limiter in 3rd gear (something which I'm not sure if I want to test), or 159.7km/h. The engine being less powerful and more revvy, the temptation might be there to drop down not only from 4th but also 5th gear into 3rd should the road rise sharply and suddenly... and there's always that risk of an, ahem, "typical" :-/ Micra driver getting 3rd and 5th confused when shifting up from 4th (though quite what at least 50% of that contingent would be doing at 100mph is anyone's guess). Limit the thing at 160km/h or even 165km/h (which is what the machine at least *claims* it's achieving - judging the speedometer and elective limiter against roadside laser readout machines, it seems a bit optimistic even at low speeds), and the risk of exploding the engine with an unwise gearchange is banished. If you're very determined, it might briefly peak near to 7200, but in practice it's unlikely to exceed 7000...
(That said, the one and only time I've managed that sort of mistake myself was slipping up on a 3rd-to-4th shift and getting 2nd. I must say, Vauxhall build their engines quite tough; despite a 6000rpm limiter, and my reaching for the shift quite close to that in 3rd, with the rev needle going off the end of the 0-to-8 scale for several seconds, it seemed to withstand the ordeal with no obvious damage...)
This would still be an annoying and rather dumb thing to be saddled with, but I could at least see the logic of it if so. The numbers are just too convenient, with the limiter in a higher gear(s) being a mere fraction higher than the rev-limited max speed in a lower one for both cars, despite the different power outputs and gear ratios.
(Certainly the tyre explanation/gearbox explanations don't make much sense for the lower powered car, as it's probably got the exact same box just with two slightly altered ratios, and the tyres are largely the same as well. 170km/h (R) rated rubber tends to be full winter spec; summers and all-seasons are rarely found claiming less than 190km/h (T) capability, and I don't think I've ever seen or fitted anything with less than an "S" (180k) code)
Also wonder if the gaps between 3rd/4th and 4th/5th on the NA being relatively narrow and almost the same as each other is of any significance...
FWIW on that chart, it also shows that the NA's max power is developed at just 3900rpm in the DiG-S, and its max torque is exceeded at all revs above 1950rpm, so it's certainly not a car that's hurting for power in any way. You can pretty much cap yourself at 4000 (or about 4150 in 5th) and drive it like an NA with effectively much lower gearing, only breaking out the full post-4k drama when you really need to...
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