Monday, February 14, 2011

Downpipes Yield Still More Power; Winter Tires Handle the Weather

We picked up some take-off catless downpipes from a customers, and decided to put those on the car.  The install is a little tedious because of the tight work space, but it's straightforward other than that.  If you do it yourself, plan to replace the rear gaskets.  The front gaskets are a hard ceramic type that can be re-used.

The rest of the exhaust is still stock, including the remaining main catalytic converters.  The car picked up still more power -- another 12+ hp and 10 ft-lbs, with no change in the ECU mapping.

After showing the "uncorrected" numbers in my last post, I have switched back to "SAE" correction on this one.  I figured I'd have to list out the weather conditions if I did uncorrected numbers, and with three different runs it's starting to get complicated to list all that out.  So...SAE correction just takes care of that, attempting to normalize over the different weather conditions.

In the near future Cobb Tuning will have "Stage 2" ECU mapping intended for cars with modified exhaust systems.  At that time we'll re-flash the car and get the car back on the dyno with the new ECU logic.  We expect still more power from that change, and more when we upgrade the intercooler further down the road.

If you were looking closely at the picture of our shop staff working on the 335i above, you'd see the new Continental ExtremeContact DWS tires (in stock Sport Package fitment of 225/40R18 and 255/35R18) we put on earlier this winter.  As you probably know, the Bridgestone RE050A Sport Package tires are...downright hazardous in cold weather.  The Continentals were a HUGE improvement in the snowy weather we had, with decent grip in sub-freezing temps and snow or slush.  They're fairly quiet, and they have a very comfortable ride.  The price isn't bad, either.  The one trade-off is that they are not run-flat tires, so in that sense we're flying without a net -- the 335i does not include a spare tire.  We carry a small air pump and tire plug kit, although depending on where/when we broke down we might just call for a tow if it comes to that.

Wednesday, February 9, 2011

AccessPort Installed!

We've now installed the Cobb AccessPort on our 335i project car.  As with other AccessPort installs, it couldn't be easier.  We plugged the AccessPort up to the car's OBD-II port (it's by the driver's left ankle), and selected "Install."  Fifteen or so minutes later, it was all done.  We pulled the car back on to the dyno and observed a substantial gain in power, and even more in torque.  We picked up 49 hp at the wheels, and a whopping 72 ft-lbs of torque.

Note that the graph here shows uncorrected numbers, and my previous graph was using SAE correction.  I posted the uncorrected number here because although the ambient temperatures were the same, the relative humidity levels were different by 4%, and I think the SAE correction was too heavily weighting the humidity difference.  But corrected or not, the gains are pretty impressive, especially considering how easy the install is.

Here's another graph.  This one shows our 335i with the Stage 1 AccessPort program, graphed against a stock E90 M3 that we dyno'ed a few weeks ago.  The M3 has a smidge more horsepower up towards that stratospheric 8400 RPM redline, but the 335i has as much as 113 ft-lbs (!) more torque to the wheels.

Speaking of torque, the additional grunt really points up the 335i's lack of a mechanical limited-slip rear differential.  While the "electronic differential" does work, the car has a hard time coping with so much torque, and the feeling as the power gets shuffled back and forth (as the car grabs first one rear brake caliper and then the other) is unnatural and disconcerting.  We're looking into fitting our car with a mechanical  limited-slip differential.