Photograph by Chris Tropea
Let’s get the big question out of the way for our BMW 328i project: No, the intake manifold swap and power tuning didn’t make it any faster on track. But you’re asking the wrong question if that’s the only answer you want.
The intake manifold we swapped into our BMW 328i. (Stay tuned, more info in a future update.) Photograph by Chris Tropea.
A deeper dive into the VBox data–and a look at the radar and even into the sky–told us that a faster lap probably wasn’t on the table during our test day at the Florida International Rally & Motorsport Park. And that’s all because of the weather.
Rain had just ended, and although the Central Florida track was drying, there were still wet spots in key corners that caused us to either reduce speed or drive a slightly different line to stay on the dry parts. So we just didn’t have the grip to produce a faster time given the conditions.
What we did have, however, was measurably improved thrust pretty much everywhere. In every single acceleration zone, the red trace of our improved E90 sedan climbs steeper and stronger than the green curve of the stock car.
Even in corners where we got a particularly mediocre run through the tape–like the slippery Turn 5 at 2700 feet–once we got back on the gas, the massaged car quickly outpulled the previous setup down to Turn 6.
This made for some nice speed gains heading into key braking zones, like an extra 2 mph of terminal velocity heading into both Turn 4 and Turn 8.
On a longer track with more straights, those speed traces are just going to keep diverging and handing advantage to the more powerful version of our project car.
The longitudinal acceleration graph showed the tweaked E90 was pulling harder as well, with longitudinal g under acceleration showing 5 to 10% greater through most power zones. That’s a real difference that lowers lap times.
Photograph by Chris Tropea
So, what can we estimate on a dry track? Well, if we look at the delta t graph, which shows the difference in the two times, pretty much anywhere the line is going down shows the modified 328i clawing back time under acceleration.
If we add up all the gains from those acceleration zones, we get 0.35 to 0.40 second. So, assuming a track delivering similar lateral and braking grip to our previous test, we should be looking at shaving close to that much off our previous best lap time of 1:25.69.
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