Drivers surprised at performance when JB4 removed???

[BMW135pls]

Found a thread on bimmerfest where the driver said he was shocked at the power difference when he removed his JB4 for service. Wouldn't it feel the same as it does every morning for the first 8 minutes until the engine oil hits 160°F and the tune kicks in? Am I missing something?

[DSSG]

What's missing is some details about the difference the driver experienced. From your post, we don't if the JB4 improved or not the performance.

What may seem obvious to some isn't to all. For example, after the removal of some so-called performance stuff, the car ran better.

[MightyMouseTech]

You should not be driving it hard until the oil warms up.

[e36addict]

I drive mine every morning on Map4 until I wake up/car warms up and I switch to Map6. The difference is magnificent..

[darkrom]

Originally Posted by MightyMouseTech

You should not be driving it hard until the oil warms up.

Exactly. I wouldn't be driving a cold car hard, stock OR JB4.

[BMW135pls]

Originally Posted by DSSG

What's missing is some details about the difference the driver experienced. From your post, we don't if the JB4 improved or not the performance.

What may seem obvious to some isn't to all. For example, after the removal of some so-called performance stuff, the car ran better.

He was surprised how slow it felt without it, he noted that the car without JB4 felt like it was in a "weakened state."

I fully understand to drive in "good boy" mode until the oil gets to temp, but the operativr thought here is that the JB4 tune doesnt kick in until 160°F anyway, so how could someone be surprised what the stock car feels like? By my knowledge, I'm driving a stock car for the first 8-10 minutes of my commute. Unless, does the JB4 stoll 'manage' certain engine functions until warm and then only the boost curve gets kicked up?

[ShocknAwe]

Well, if you normally wait to get on it until the engine is warmed up, then you would notice a huge difference. My car behaves no differently if I drive easy whether tuned or stock.

[BMW135pls]

Originally Posted by ShocknAwe

Well, if you normally wait to get on it until the engine is warmed up, then you would notice a huge difference. My car behaves no differently if I drive easy whether tuned or stock.

I guess that's pretty reasonable. Maybe I'm just sensitive to this, but I def feel a difference when the tune kicks in even if I'm only putting 15-20% throttle down and following traffic. The tuned engine sure seems like it has more "lift" and the boost guage usually shows an extra 1-2lb when it's kicked in, traffic driving.

[BMW135pls]

Just an update as I've found the answer. After asking Jon@BMS about the JB4, it seems the JB4 will control the boost levels even when the car is in its warm up cycle. I didn't know this. So apparently the only way to have a stock tune again is to remove the JB4 entirely... pretty interesting.

[Ginger_Extract]

Because he/she is comparing hard driving on stock tune to hard driving on the JB4. The difference IS dramatic. When I dialed the boost back for track days, I am amazed at how lethargic these cars feel.