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Re: Throttle Lag
quote:
I've noticed a few times in the last few months that if I'm accelerating moderately from stand-still, and then back off the accelerator, it seems to "run on" for maybe a second, or surge forward if it decides to shift up a gear just as I back off the accelerator. I think it's nothing serious, and more likely a chance occurence as I mis-time my backing-off of the accelerator just as the gearbox decides it wants to shift up a gear.
Has anyone else experienced this?
Rich
Rich, this happens to me as well, especially if I get stuck in traffic where you would press the accelerator gently to start moving only to find the car in front of you has braked yet again, so you move your foot off the pedal while the gearbox in the process of changing/shifting-up gears and this run-on happens. I think this is normal.
The throttle lag I was describing happens more often in a situation where you try to overtake a car in a hurry and you need all the speed and momentum you can find, so you press the accelerator harder (floor it-I call it) to initiate a faster gear change, only to find that the exy accelerates at it's own pace and that much needed throttle response to your hard pedal-work is not there when you needed it.
The above would also (obviously) increase your fuel consumption and you would only need to glance what happens to that petrol indicating needle to see how it moves down all of a sudden, so it's not something that is encouraged to be done on constant basis.
I should add that this lag doesn't happen all the time.
It gives me the impression that there is some sort of a "magical" method and strength, which you need to carefully time before pressing the accelerator, and get that instant throttle response. Something that I haven't yet mastered nearly 3 years down the track of driving an exy LOL 
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5/Jul/2005, 9:32 pm
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Re: Throttle Lag
Thinking out loud:
If the petrol needle moves, that is more likely because the fuel in the tank(although it must have baffles) has moved to the rear. I agree though, flooring it regularly in any vehicle is hard on economy.
Are we talking about what I would call throttle lag - delayed engine response to accelerator movement - which I would find unacceptable, and still think ought to be no different in fly-by-wire from a mechanical connection, or are we talking about the rate of accelaration of a 1500kg+ vehicle with a 2.5 litre engine (which I think is pretty good in the XTrail).
Automatic gear boxes do have a small delay in recognising the nedd to change up (our XTrail seems pretty quick to me - without even comparing it to the 1960 falcon I once had), but this is not what I would call throttle lag either.
--- David M (X095)
 ST Auto (series 1) 165,000 kms
Nissan nudge, fog lights, towbar, floor mats, K&N filter, Dunlop RV501's did 85,000 kms, now on Cooper CS4s |
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6/Jul/2005, 10:05 am
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Re: Throttle Lag
quote:
David M wrote:
Are we talking about what I would call throttle lag - delayed engine response to accelerator movement - which I would find unacceptable
Yes, well at least that is what I was trying to describe in my response above
quote:
or are we talking about the rate of accelaration of a 1500kg+ vehicle with a 2.5 litre engine (which I think is pretty good in the XTrail).
I'm happy with the acceleration rate given the size of our exy. It's no race car for sure LOL
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6/Jul/2005, 11:07 am
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Re: Throttle Lag
In basic terms if I understand it correctly:
Fly by wire: the accelarator pedal is simply a "volume control" - varies a voltage to the computer. Engine response should be instantaneous: the ecu is set though to open the butterfly valve (controls how much air enters the engine) at a rate appropriate to the engine's increase in rpm (and to inject appropriate amounts of fuel). Presumably for performance reasons, Nissan would have set this so that when you floor it, the computer increases the engine revs at the quickest rate possible consistent with not sending unburnt fuel through the exhaust - the advantage of fly by wire is its easier to meet emission standards.
With a direct mechanical connection, flooring it opens the butterfly valve wide, and usually there is a squirt of fuel so the resulting air mixture is not too lean.
David M.
--- David M (X095)
ST Auto (series 1) 165,000 kms
Nissan nudge, fog lights, towbar, floor mats, K&N filter, Dunlop RV501's did 85,000 kms, now on Cooper CS4s |
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6/Jul/2005, 5:39 pm
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Re: Throttle Lag
Hi Dave,
Your explanation is 100% correct in every detail.
Further details and pics can also be found HERE
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6/Jul/2005, 7:42 pm
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Re: Throttle Lag
Copied from another thread-Posted by hicksy
Hi i had some throttle lag in my 04 xtrail the passed few months so we took the car back to the nissan dealer up here and they made some ajustments the xtail now goes like a rocket ship . the service mannager told me that they checked the tdc time ,they reset the IACV control what ever that is it seems to they done the job the throttle responce is a lot better then has ever been
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20/Aug/2005, 8:55 am
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Re: Throttle Lag
Copied from another thread-Posted by Exy Ti
Hi thanks for that ... when you say "throttle lag" ... did the throttle come on with a surge after the lag or was it smooth?
And has your engine revs returned to idle speed without delay when moving to neutral or depressing the clutch on gear changes?
Exy Ti
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20/Aug/2005, 8:57 am
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Re: Throttle Lag
Thanks, Hicksy. As I said before - throttle lag is unacceptable (to coin a phrase) and not to do with fly--by-wire versus mechanical throttle. David M
--- David M (X095)
ST Auto (series 1) 165,000 kms
Nissan nudge, fog lights, towbar, floor mats, K&N filter, Dunlop RV501's did 85,000 kms, now on Cooper CS4s |
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22/Aug/2005, 9:27 am
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 Re: Throttle Lag
We don't seem to have any throttle lag with our series 1 STR. In fact it is very similar to the '98 Pulsar we just sold, which of course was the old throttle cable. We just bought new a Mazda 3, which still has a cable, and it is LESS responsive than the Xtrail!!
I've noticed this:
a)if I am cruising on the highway in 5th with very little trottle movement,the Xtrail seems to go into economy mode where overtaking would be a bit sluggish.
b) I come up behind a car and I am waiting for an overtaking opportunity, I go back to 4th gear and wait - the Xtrail goes into overtake/responsive mode and IF I have to go back to 3rd to overtake throttle response and power are VERY impressive and leaves almost anything for dead, even uphill! 4th gear is also good for overtaking in this situation, so long as I drive in 4th for a while to make sure economy mode is left behind.
Naturally the K&N helped somewhat.
---
Shawn and Belinda Eggins
2003 STR, K&N, Strut brace, Ground wires, Dunlop LM702's, Tint, Mud flaps, Tow, Nudge, Spots, Mats, Rear scuff plate
http://eggins.synthasite.com/
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15/Sep/2005, 9:49 am
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Re: Throttle Lag
This would seem to be more common with the Auto models.
Mine is a Manual and I have no Throttle lag whatsoever that I notice.
Last edited by NPC73, 15/Sep/2005, 11:19 am
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15/Sep/2005, 11:15 am
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