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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Tracking, Autocrossing, Dragstrip, Driving Techniques > When DTC is OFF I can't launch straight ahead



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      04-23-2010, 03:59 PM   #1
Patrys@BimmerTech
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When DTC is OFF I can't launch straight ahead

Today I was practicing before going to the 1/4 mile drag strip on Sunday.
My car is a 335i AT and when I switch DTC all the way off I can't launch straight ahead. My car always goes to the right that much that I am afraid I can hit a car on the other lane.

If I press the DTC button just once and the DTC sign shows up on the dash everything is fine.
You can see my mods in my signature. They include an LSD.
What can be a reason for this ?

I have read that it is better to turn the DTC off to achieve better times, so I am worried my times will not be that good.
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      04-25-2010, 12:46 AM   #2
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Quote:
Originally Posted by Patrys View Post
Today I was practicing before going to the 1/4 mile drag strip on Sunday.
My car is a 335i AT and when I switch DTC all the way off I can't launch straight ahead. My car always goes to the right that much that I am afraid I can hit a car on the other lane.

If I press the DTC button just once and the DTC sign shows up on the dash everything is fine.
You can see my mods in my signature. They include an LSD.
What can be a reason for this ?

I have read that it is better to turn the DTC off to achieve better times, so I am worried my times will not be that good.

Rear subframe deflection can cause the car to steer left or right when power is applied. The fix - M3 subframe bushings.

Couple of other component to consider is the M3 guide rods, it takes away a rubber bushing and replace it with a bearing with almost no deflection at all.

The last piece of the puzzle is a toe links. Toe changes will cause the rear of the car to steer.
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      04-25-2010, 10:51 AM   #3
satakal
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this one time at the strip, I had all nannies off. I was in the left lane. I launched then all of a sudden, I was in the right lane. Thank goodness the car I was heads up with was way quicker. Also, thank goodness I wasn't in the right lane.

It could have been expensive. I don't think I've been back to the strip with the e90 since.
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      04-26-2010, 06:52 AM   #4
Patrys@BimmerTech
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Quote:
Originally Posted by HP Autowerks View Post
Rear subframe deflection can cause the car to steer left or right when power is applied. The fix - M3 subframe bushings.

Couple of other component to consider is the M3 guide rods, it takes away a rubber bushing and replace it with a bearing with almost no deflection at all.

The last piece of the puzzle is a toe links. Toe changes will cause the rear of the car to steer.


Thanks Harold.

I will have to seriously consider upgarding my rear suspension.
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      04-26-2010, 06:54 AM   #5
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Quote:
Originally Posted by satakal View Post
this one time at the strip, I had all nannies off. I was in the left lane. I launched then all of a sudden, I was in the right lane. Thank goodness the car I was heads up with was way quicker. Also, thank goodness I wasn't in the right lane.

It could have been expensive. I don't think I've been back to the strip with the e90 since.
I know what you mean. It was really scary to feel the car was out of control...
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