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Driveshaft "rate of change" for traction control


Phil2JZ
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Hey team,

660whp 2JZ S15 with LINK G4+ FURY, 5 speed, setup for grip and drag.

Im after the best way to use my custom driveshaft sensor feedback that is connected and setup as "driven wheel speed" for  traction control. How would the 3D traction control table need to be setup to monitor driveshaft speed rate of change, ignition retard and anything else etc 

Im wanting to get the maximum benefits from driveshaft speed traction control like the big boy grip and drag guys use.

Its currently setup with a Cherry hall effect sensor picking up on the 4x driveshaft bolt heads.

Ive also got a custom sensor up front, setup as "undriven wheel". And yes i can do a slip of 5,10, 15%  but i would like this as a secondary measure and not the primary.

I understand that with only 4 pick up points on the driveshaft, the resolution will not be very good and would like to also know what the maximum amount of teeth pick up points i could run (to get maximum resolution) without maxing the "max frequency the LINK G4+ FURY can handle.

I.E 16 tooth pickup wheel?

 

My concept is, if i rely on the front and rear wheel slip, by the time the rear wheel has slipped 1/2 wheel rotation and the ecu detects this and retards the ignition, its far too late and a lot of wheel spin happens and high retard is needed. This = a slow caf. Now if the same thing happens (1/2 wheel rotation) and im running a 16 tooth pickup sensor on the driveshaft, thats 8 teeth its seen already. So If it was setup in the traction control system to start retarding the ignition at 2 teeth input, that catches the wheel spin much faster than the previous setup. 

I expect it to take some refining but its a much faster acting system?

My S15 is setup well for mechanical grip, micky thompson drag radials, Pro drag suspension etc. My main issue is wheel spin in 2nd gear roll racing. 3rd and 4th gear has full grip.

Would really appreciate some help on this 

 

kind regards 

 

 

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Picking up on the diff/prop bolts gives you 4x your diff ratio pulses per wheel revolution.

Assuming your S15 has the same 3.691 ratio as my S14 diff, for the same size tyres front and rear you need 15.84 pulses on the front wheel to be equal. (If your tyres are different sizes, that obviously changes based on circumference)

Whilst 500Hz is often quoted as the maximum frequency input, a post by Adam here clarified that that's on a really busy ECU - V8, direct spark, 4 VVT channels, 8 knock channels etc - if it's a "less busy" ECU then you can get higher frequency reads on the inputs.

 

I found that the "slip" seems to be calculated each time either wheel sensor gets an update, so when I only had 4 pulses per revolution on the front wheel, but 16 on the rears, the slip percentage would "step up" with the 4 updates of the rear, before being "reset" with the pulse from the front.

Now I've added extra pulses to the front, it calculates and tracks much better, and my traction setup works much better - I have a twin turbo V6 with about 360hp, weighing 1000kg and 185/60/13 tyres... so grip is a bit of an issue! ;)

Oh, just realised you said driveshaft, I misread it... in which case it might not be quite as I said above!

If you did mean driveshaft, doesn't it have either 3x2 or 5x1 bolts holding the inner CV joint to the diff?

Or do you mean propshaft to diff?

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Thanks for the reply mate,

Yea I have my rear sensor connected to the 4 bolt heads on the main shaft from gearbox to rear diff. My rear diff is a 4.08 if that matters.

 

But I’m not trying to use slip differences from rear to front sensors for the traction control, I’m trying to use the driveshaft data only.

This would be, say the main driveshaft rpm is 1000rpm max with no wheel spin but 1010rpm with wheel spin starting to happen. I want to detect this “rate of change” on the driveshaft speed to activate the traction control. 
 

Then potentially use the front and rear wheel speed Slip as a secondary back up. 
 

hope that makes sense haha 

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There is no way to do drag race style power management or "traction control" in G4+.  This is a function that has been added to G4X, but I cant think of anyway to achieve something similar with the functions available in G4+.

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Ok, so 4x4.08 = 16.32 pulses per revolution from the driven wheels.

As far as I'm aware, the Traction Control system in the Link requires the Slip calculation between driven and non-driven wheels - you're getting 16 updates per wheel revolution from the rear, ideally you want 16 from the front too.

However, as I'm not totally sure, no doubt Adam will be along soon to correct me! :p

Maybe it's possible with the new Math Blocks in the G4X?

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9 minutes ago, Adamw said:

There is no way to do drag race style power management or "traction control" in G4+.  This is a function that has been added to G4X, but I cant think of anyway to achieve something similar with the functions available in G4+.

Thanks Adam, that’s basically what I needed to know. So im not waisting my time.
 

If I upgrade  my current Link fury g4+ and swap it out to the newer Link g4X fury ecu, is it as simple as loading up my G4+ tune onto the G4x and it will work exactly the same? Ie the newer software converts it 100%.

oR will I need to reallocate, calibrate and tune some things? 

 

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27 minutes ago, Confused said:

Ok, so 4x4.08 = 16.32 pulses per revolution from the driven wheels.

As far as I'm aware, the Traction Control system in the Link requires the Slip calculation between driven and non-driven wheels - you're getting 16 updates per wheel revolution from the rear, ideally you want 16 from the front too.

However, as I'm not totally sure, no doubt Adam will be along soon to correct me! :p

Maybe it's possible with the new Math Blocks in the G4X?

Thanks mate, but yea It’s looking like I’ll need to move over to the G4x platform to get the desired control.

 

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2 hours ago, Phil2JZ said:

is it as simple as loading up my G4+ tune onto the G4x and it will work exactly the same? Ie the newer software converts it 100%.

oR will I need to reallocate, calibrate and tune some things? 

unfortunately G4X is too different to do an automated conversion, you have to do it manually and make some decisions along the way.  The easiest way is to open G4+ and G4X softwares side by side in a split screen, then start at the top of the ecu settings tree and work your way down.  Nearly all tables (fuel/ign/cold start etc) can just be exported/imported between the two.  It takes about 20mins to convert a map.  Ignition is mostly the same.  Fuel has quite a few new options and the accel fuel has changed quite a bit.  Stuff like idle control and most PID loops are very different and will have to be tuned from scratch.  Assignment of inputs and outputs etc is quite different but makes sense once you have figured it out.  

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On 7/6/2022 at 10:18 AM, Adamw said:

unfortunately G4X is too different to do an automated conversion, you have to do it manually and make some decisions along the way.  The easiest way is to open G4+ and G4X softwares side by side in a split screen, then start at the top of the ecu settings tree and work your way down.  Nearly all tables (fuel/ign/cold start etc) can just be exported/imported between the two.  It takes about 20mins to convert a map.  Ignition is mostly the same.  Fuel has quite a few new options and the accel fuel has changed quite a bit.  Stuff like idle control and most PID loops are very different and will have to be tuned from scratch.  Assignment of inputs and outputs etc is quite different but makes sense once you have figured it out.  

Ok thanks again.

Looks like ill be upgrading to the G4X platform. Ive been through the new software and it has many more features. The Power management, speed target tables and race timer feature look great.

With the G4X, and selecting the correct amount of pick up teeth on the driveshaft ring install? 18 tooth or more? Obviously wanting it to be quick to respond but not breach the frequency limits (if that can even happen now)

kind regards

phil

 

 

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