Improving acceleration

[Kieran O'Quick]

The throttle controller is a good cheap bit of extra speed. Mid corner subtly suffers though unless you can flick between modes with a third hand...

 

If you want to actually get quicker times its all about grip, a diff and weight. Overall though, if it doesn't feel quick enough for you even these mods won't help. If you want a car to feel crazy fast you'd need to get something light and turbo  

[charles davidson]

like the man said brakes then handling,

[Jay84]

I'm surprised ekona didn't mention this, but the right tyres will always be a great investment for speed.  They'll give you confidence in the corners, get the power down better and grip the road better on harsh breaking. No point spending on a good power and handling set up then fitting ditch finders. 

[Ekona]

I figured I’d let someone else mention tyres for a change  

[coldel]

Throttle controller is a bit of a myth as it does not give you extra speed, the throttle controller does make the throttle input more sensitive i.e. if you have the peddle down 10% it will push the input to the ecu as something like 50% You can replicate this by pushing the throttle down with your foot 50% also. It does give the illusion of extra speed because on high settings any touch on the pedal literally jerks the car forwards, much like it would if you drove around with your foot pressed completely down. 

[Ekona]

It's fun for three minutes, then you realise you lose precise modulation of the throttle so the car actually becomes harder to control on the corners. I had one for a bit, then binned it when I realised the illusion was doing more harm than good. I really don't recommend them any more.

[Jay84]

They've never been something I was interested in, the sport button on vauxhalls did the same, powered an led and increased throttle sensitivity. 

[Kieran O'Quick]

There is a built in delay in throttle response in the low gears - great in traffic but not when you're going flat out. The tuners remove this delay usually. The throttle controller is handy if you want to calm it down in the wet for example.  

[Ekona]

Perhaps, but it's not like you can't do the exact same thing just flexing your ankle a bit less. Plus it's not like the throttle on the 350 is particularly snappy.

[coldel]

There is a thread on here somewhere if you search for it explaining it all.

[coldel]

And if I remember correctly Mark at Abbey debunked the whole limited power in gears 1-3 at some point (like 6 or 7 years ago), again would need digging out! Or maybe Mark could jump on here and clarify given his knowledge of ecus and mapping 

 

That the first three gears the throttle input isnt linear i.e. 25% of the way down does not result in 25% throttle, but once you have the foot to the floor in first three gears 100% throttle gives you 100% throttle. Its just wound back in terms of how quickly it builds, the TC will change that curve, but wont give you any more acceleration or speed - you can achieve the same by pressing the throttle pedal in a bit more.

 

This is all from memory from years ago so open to being told otherwise!

[OnlyAfro]

With a mech throttle, the butterfly opening is directly proportional to pedal position and instantaneous.

 

However, with DBW, there are 3 factors that affect throttle response, the sensor calibration, position translation and PID control.

 

PID control determines the step response of the throttle, i.e. how fast it can react. 

 

Position translation determines the correlation between pedal and throttle position. So if gear 1-3 are less sensitive at low throttle, the table would look something like this:

*This is just an example of a translation table based on gear, but you could set it up for anything and then implement comps for different factors.

 

Sensor calibration is essentially the same as position translation, but is a global position translation curve.

 

A throttle controller just messes with the calibration, removing resolution, squishing it horizontally, making it more sensitive. The max and min values won't change, but rather than needing the press the pedal fully, you may only need to press it half way to open the throttle fully. The PID step response still limits how fast that can physically happen, but assuming that isn't a bottleneck, in theory you save the fraction of a second it takes to press the pedal that last 50%, but at the cost of lack of control.

 

[Kieran O'Quick]

So does the remap change the PID and physically open the butterfly quicker then?

[OnlyAfro]

Don't know the specifics of the base map or UpRev.

 

I'd guess the remap just makes the position translation linear in 1-3, or the same as the other gears, but you can set whatever curve you like.

 

PID settings are global and aren't altered on the fly for different conditions. Changing the PID values isn't something I'd expect anyway, you generally tune the system and then don't touch it. Nissan probably already optimised the step response - minimising rise / settling time, error and overshoot - so I doubt you can make the butterfly open quicker without adding unwanted properties. The butterfly motor actuator will only be able to move so fast anyway.

 

Could be wrong and Nissan may have artificially delayed how fast the butterfly opens, but seems silly to me. One of the tuners would be able to give the more accurate insight.