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VtrSp1

G4+ Fury Sequential shift cut

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I have a G4+ Fury installed in my race car with sequential gearbox.

The ecu is awesome and all work very good. I need only a few clarification about the Sequential Shift Parameters/setting .

As i mentioned before, i use the ecu to do the Shift cut for my Sequential Gearbox in Closed loop mode with Loadcell Knob and Gearposition sensor with Ignition cut % set at 90% and a Ignition Reatard at -15° for reintroducing torque strategy at 20 mS. In the Last weekend i tested them on track and when i do the Upshift strategy i have a big bang in the exhaust . it's normal because i cut the ignition at 90% and the rest 10% is retarded at -15°. I set the retard to -15° because i feel the shift lever smooth than a -10° retard.

I have try to set the Fuel trim shift cut to a negative value to reduce the fuel amount in the shift cut but it's not possible to insert a negative value.

How i can remove fuel in the shiftcut strategy to reduce the bang in the exhaust?

In the log i take a look at Gear Parameters and when the barrell move, the Gear number go to 0 for a little moment during shifting. My Gear tollerance is set to 0.1V because i want the shift cut quite safe.

If the Gear tollerance is low value, the power re-engage is safe for a full dog engage vs a high gear tollerance number?

 

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It sounds like you understand the systems well.

 

42 minutes ago, VtrSp1 said:

I have try to set the Fuel trim shift cut to a negative value to reduce the fuel amount in the shift cut but it's not possible to insert a negative value.

Try a +10% fuel trim.  I know this goes against what your logic would expect but I find this usually works better at minimising the "bangs".  On other ECU's I use that allow both positive or negative fuel trim I still find adding fuel is usually the best.

 

45 minutes ago, VtrSp1 said:

How i can remove fuel in the shiftcut strategy to reduce the bang in the exhaust?

If you really want to try a negative fuel trim, you can do it using a 4D fuel table.  Set the table activation to "Virtual aux 1".  Set up Virtual aux 1 to become true when ignition cut is >89% and <=90%.  The 4D fuel table will then only become active when the 90% gear cut is applied. 

18dD94L.png

 

51 minutes ago, VtrSp1 said:

In the log i take a look at Gear Parameters and when the barrell move, the Gear number go to 0 for a little moment during shifting. My Gear tollerance is set to 0.1V because i want the shift cut quite safe.

If the Gear tollerance is low value, the power re-engage is safe for a full dog engage vs a high gear tollerance number?

 

Yes, this is quite normal to see a short "gear 0" between each gear when using closed loop shift.  The gear tolerance affects the position that the ECU considers that the next gear is fully engaged.  My tolerance is usually more like 0.2v on the few closed loop setups I have done so your 0.1V maybe a little conservative.   This takes some experience to get right but I suggest logging most gear related parameters at 100Hz and try a couple of larger tolerance variations, you can usually get a pretty good idea by looking at gear lever force and barrel position.  If the tolerance is about right you will often see little dip in gear lever force at the end of the shift sequence while the barrel is still moving (this is the dogs getting pulled together by the tapers when torque is reintroduced). 

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Adamw, thanks a lot for the helpfull reply .

Very interesting the strategy for quite the exhaust bang with add fuel in the shift...normally i see the opposite, so cut the fuel at 100% for don't have extra fuel washing the exhaust with ignition retarded. I want to remove all bang possible due to better life of turbo and exhaust manifold.

I take a look at my gear lever force and i see the dip of force but if you can see and give me some consideration about that , this is very helpfull for me :-)

I have a internal log at 100 Hz of my track session , so i can upload and you can take a look at my gearshift parameters. I logged at 100 hz all the shift parameters.

Log 2019-08-24 6;47;34 pm.llg

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The dip you see in gear lever force is the start of the cut when the dogs let go. Often you will also see a little dip in gear lever force at the end also when the torque is reintroduced (but not always).

Your gear shift doesnt look too bad to me, you have on average about 120ms cut in the lower gears and about 80ms cut in the higher gears so this is not bad for most car gearboxes.  The volt tolerance looks about right to me as the logs show power is being re-introduced while the barrel is still moving.

From what I can see I dont think there are any big gains that can be made.  You may be able to make the shift feel smoother with some small tweaks to tolerance and upshift force, but I think in terms of performance you are not far off.  Does the gear shift feel ok or is there something you are not happy about (apart from the backfire)?

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Adamw, thanks a lot for the awesome explain !! Your explain is about same as my when i see the log after the race .

The cut time in high gear (3-4-5) is about 70-80 mS and it's not bat for me, it's the time that i expect from this type of gearbox with shift lever. I think it's possible to improve- reduce this time with modify the mechanical rotational mass (more light flywheel and racing clutch without with small diameter unsprung).

The logs show the power is re-introduced with the barrel is still moving,  normally this  can cause premature dog wear...

What i can do for have the re-introduced power with barrell stopped? I can play with a lower gear tollerance?

The lever fell smoother but not smoother than if i dab the clutch for the same shifting..

In the first part of lever pull i feel a hard shot ("tac ") with the Upshift and this isn't present when i dab the clutch or left the foot from the throttle to unload the dog...

I have the same issue a few month ago when i used for the Gear cut the Geartronics EasyShift Ecu (coil cut) in closed loop mode.

This strange feel in the lever i think in the log is showed by the firs peak of loadcell signal..

 

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