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Jun 3, 2024, 08:11 PM
#6122
How you get corner exit rotation is by applying force to the outside rear tire. When the inside rear tire is in the air the only amount of torque the outside wheel can put down is equal to the preload of the diff. This is why we use the gymkhana diff.
That amount of preload does require you to lift the inside tire on tight turns but if you aren't doing that you have other issues
(The pejorative "you").
Understeer seems to be cause by the center diff locking up due to inside rear or front wheel spin binding the front/rear together. And like turning a 4x4 truck locked on pavement doesnt work, its fighting high grip AWD rally cars as well.
That amount of preload does require you to lift the inside tire on tight turns but if you aren't doing that you have other issues
(The pejorative "you"). Understeer seems to be cause by the center diff locking up due to inside rear or front wheel spin binding the front/rear together. And like turning a 4x4 truck locked on pavement doesnt work, its fighting high grip AWD rally cars as well.
Jun 4, 2024, 07:59 AM
#6123
How you get corner exit rotation is by applying force to the outside rear tire. When the inside rear tire is in the air the only amount of torque the outside wheel can put down is equal to the preload of the diff. This is why we use the gymkhana diff.
That amount of preload does require you to lift the inside tire on tight turns but if you aren't doing that you have other issues (The pejorative "you").
Understeer seems to be cause by the center diff locking up due to inside rear or front wheel spin binding the front/rear together. And like turning a 4x4 truck locked on pavement doesnt work, its fighting high grip AWD rally cars as well.
That amount of preload does require you to lift the inside tire on tight turns but if you aren't doing that you have other issues
(The pejorative "you").Understeer seems to be cause by the center diff locking up due to inside rear or front wheel spin binding the front/rear together. And like turning a 4x4 truck locked on pavement doesnt work, its fighting high grip AWD rally cars as well.
In that example scenario, ice would be equivalent to one tire in the air, right? As soon as you accelerate and the tire touches down, you should get more torque transfer anyway, and that's when you want the power-on rotation. Before that, one tire in the air should essentially help corner-entry rotation, no? especially with a 1-way where there's no attempted locking between rear tires, where the lifted tire should basically be stopped when in the air.
re: the ACD's actions, I don't know but I've got the ER tune and I think we're in agreement that the center diff should more or less be open on turn-in, maybe minmal lock on braking for stability/max braking but should be open as you turn the wheel without gas, locking as you add gas.
Jun 4, 2024, 08:40 AM
#6124
In your example, the tire on ICE (assuming pure zero grip) will spin equal to the grip tire until the torque to the side with grip exceeds preload. Then any extra applied torque will just increase speed of the ICE tire. In reality the ice has some amount of friction and will create more lockup of course.
The reason for preload is so we can get on throttle as early as possible. Which is when the inside rear is in the air. Yes it will set down once you have enough acceleration, but with low preload the acceleration limit before spinning is easily exceeded before touch-down. IIRC, the low preload versions are around 30-40 ft-lbs and the gymkhana version is 90-100 ft-lbs. Since its split front/rear assuming no slip, then thats ~75 ft-lbs or 190ft-lbs for the two diffs you can put down before the inside lets go.
The reason for preload is so we can get on throttle as early as possible. Which is when the inside rear is in the air. Yes it will set down once you have enough acceleration, but with low preload the acceleration limit before spinning is easily exceeded before touch-down. IIRC, the low preload versions are around 30-40 ft-lbs and the gymkhana version is 90-100 ft-lbs. Since its split front/rear assuming no slip, then thats ~75 ft-lbs or 190ft-lbs for the two diffs you can put down before the inside lets go.
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RobbieOh (Jun 5, 2024)
Jun 4, 2024, 08:48 AM
#6125
In your example, the tire on ICE (assuming pure zero grip) will spin equal to the grip tire until the torque to the side with grip exceeds preload. Then any extra applied torque will just increase speed of the ICE tire. In reality the ice has some amount of friction and will create more lockup of course.
The reason for preload is so we can get on throttle as early as possible. Which is when the inside rear is in the air. Yes it will set down once you have enough acceleration, but with low preload the acceleration limit before spinning is easily exceeded before touch-down. IIRC, the low preload versions are around 30-40 ft-lbs and the gymkhana version is 90-100 ft-lbs. Since its split front/rear assuming no slip, then thats ~75 ft-lbs or 190ft-lbs for the two diffs you can put down before the inside lets go.
The reason for preload is so we can get on throttle as early as possible. Which is when the inside rear is in the air. Yes it will set down once you have enough acceleration, but with low preload the acceleration limit before spinning is easily exceeded before touch-down. IIRC, the low preload versions are around 30-40 ft-lbs and the gymkhana version is 90-100 ft-lbs. Since its split front/rear assuming no slip, then thats ~75 ft-lbs or 190ft-lbs for the two diffs you can put down before the inside lets go.
Jun 5, 2024, 06:26 AM
#6126
so twice in a row now after an event the o2 sensor on the car has failed. I never had an issue on my old aem wideband, and i only changed bc the shop recommended i get a newer, "better" wideband. it uses a bosch lsu 4.9 or something, and it's twice now. 1,000 mile trip home, driving all around, all good - but as soon as I have an event, right after - the o2 sensor fails. Anyone have any recommendations?
Jun 5, 2024, 09:14 AM
#6127
From what little I know, the 4.9 is very sensitive to the heater control but when done right (like an OEM application) its very robust. The older 4.2 seems to be a bit more robust but not as accurate, or maybe it wasnt as fast?
Not an expert in it of course, just going off foggy memory. I have a 4.2 thats been in the car for 15 years. Previously at the end of the downpipe but now in the o2 housing. But now that Im talking about it, I'll be keeping a spare in the trailer.
Not an expert in it of course, just going off foggy memory. I have a 4.2 thats been in the car for 15 years. Previously at the end of the downpipe but now in the o2 housing. But now that Im talking about it, I'll be keeping a spare in the trailer.
Jun 5, 2024, 11:37 AM
#6128
From what little I know, the 4.9 is very sensitive to the heater control but when done right (like an OEM application) its very robust. The older 4.2 seems to be a bit more robust but not as accurate, or maybe it wasnt as fast?
Not an expert in it of course, just going off foggy memory. I have a 4.2 thats been in the car for 15 years. Previously at the end of the downpipe but now in the o2 housing. But now that Im talking about it, I'll be keeping a spare in the trailer.
Not an expert in it of course, just going off foggy memory. I have a 4.2 thats been in the car for 15 years. Previously at the end of the downpipe but now in the o2 housing. But now that Im talking about it, I'll be keeping a spare in the trailer.
not sure what to do about the 4.9 if it is gonna keep failing event after event, extra speed is pointless. I also had a 4.2 int he car for the past 10 years, i shouldnt have listened to the shop to switch
Jun 5, 2024, 12:10 PM
#6131
so twice in a row now after an event the o2 sensor on the car has failed. I never had an issue on my old aem wideband, and i only changed bc the shop recommended i get a newer, "better" wideband. it uses a bosch lsu 4.9 or something, and it's twice now. 1,000 mile trip home, driving all around, all good - but as soon as I have an event, right after - the o2 sensor fails. Anyone have any recommendations?
Jun 5, 2024, 01:18 PM
#6135
EvoM Guru
iTrader: (1)
Originally Posted by Dallas J
Did they change out the controller too? Like, is it suppose to have a 4.2 and they just swapped in a 4.9 or did they change to a completely difference gauge/controller?