Sup w/them 2026 Spring Projects?
That's what I was wondering. If the 4.9 is more temperature sensitive I'm guessing the control is working to get it to temperature but not able to keep it from going over temp and killing it. Which would make sense that its dying at an AX with sustained heat vs street driving.
At least from all of this, I'm happy I've stuck with the 4.2 since mine is in the o2 housing too.
At least from all of this, I'm happy I've stuck with the 4.2 since mine is in the o2 housing too.
That's what I was wondering. If the 4.9 is more temperature sensitive I'm guessing the control is working to get it to temperature but not able to keep it from going over temp and killing it. Which would make sense that its dying at an AX with sustained heat vs street driving.
At least from all of this, I'm happy I've stuck with the 4.2 since mine is in the o2 housing too.
At least from all of this, I'm happy I've stuck with the 4.2 since mine is in the o2 housing too.
Evolving Member
Joined: Feb 2018
Posts: 297
Likes: 47
From: St. Petersburg, Florida
FWIW I had 2 genuine Bosch 4.9 sensors not working straight out of the box. Just pegged max lean at all times with the dashes on the gauge. 3rd sensor finally worked and has been perfect for a couple years now.
Mine work for normal driving, and then fail after an event. Once failed, they do not work again, I just get an E8 error on the reading on the gauge.
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.
Non ACD cars have the viscous coupling, which will heat up and lock once there is too much wheelspin.
I'm wondering if drilling the VCU case to release the fluid work work... Make it an open centre diff
Yes, on 2 cars. The very very early English Racing proto tunes didnt work and made the ECU error and go full open. It was absolutely atrocious. Like it would snap over and snap under steer all in the same corner. Was basically impossible to drive.
Originally Posted by Evo9isLife
FWIW I had 2 genuine Bosch 4.9 sensors not working straight out of the box. Just pegged max lean at all times with the dashes on the gauge. 3rd sensor finally worked and has been perfect for a couple years now.
Evolved Member
Joined: Mar 2008
Posts: 2,110
Likes: 320
From: Croatia
ACD goes open when the pump breaks down and it is no fun... drives like **** and understeers all over the place
The 4.9 is used in high volumes in OEM applications all over the place. It's definitely not failing at that rate with OEM controllers.
Bosch provides a proprietary integrated circuit for operating the sensor, but I don't know which, if any, of the aftermarket gauge companies actually get access to it. If they roll their own control loops and algorithms then the sensor could easily be operating out of the safe area.
If you had a working setup then I don't blame you for returning to it, but personally I'd be switching to a different 4.9 based system if I was going to spend money on something new.
Bosch provides a proprietary integrated circuit for operating the sensor, but I don't know which, if any, of the aftermarket gauge companies actually get access to it. If they roll their own control loops and algorithms then the sensor could easily be operating out of the safe area.
If you had a working setup then I don't blame you for returning to it, but personally I'd be switching to a different 4.9 based system if I was going to spend money on something new.
OEM applications have it dialed, totally reliable in normal applications. Im guessing they have a lot of control and testing in each specific application. Then we throw them in random places with huge variance in heat, carbon, and fuel loads. Just really seems to be the wrong sensor for aftermarket where robustness is more important.