2007/2008 Harley-Davidson Engine Performance
Harley-Davidson's new line of 2007/2008 engines is a major shift from
previous years. The Twin Cam engine size has grown from 88CID to 96CID
with a longer stroke. The HD CVO engines are now 110 CID. There are
upgrades to the standard 96CID engine to 103CID by installing a "big
bore kit" and to 110CID by installing a stroker crankshaft with the
big bore upgrade. All Twin Cam bikes now have 6 speed transmissions.
The very problematic cam area has also been re-engineered, requiring
different cams from previous years (with the exception of 2006 Dyna
|The 2006 Dyna's and all HD 2007 engines have a reputation for
very hot exhaust systems. This problem is well documented for the
2007 FLH's, but does exist on all the bikes. This issue is directly related to the EFI
closed loop operation mode at idle and cruising speeds. In closed
loop mode, the narrow
band O2 sensors used by the Delphi ECU hold the air fuel ratio at
14.7:1 which is good for EPA compliant emissions but creates a very
hot exhaust pipe. Nightrider has a fix for this issue that will
reduce the exhaust temperature, lower the operating temperature and improve throttle response.
Nightrider has come up with a fix for this problem. Read
about our fix here.
An even bigger change is the fact that all HD's including Sportster,
now have fuel injection with dual O2 sensors. This allows the engine to
run in a closed loop mode of operation where the fuel mixture is
controlled by the 02 sensor.
While HD does not publish horsepower numbers in its sales literature
for the 96CID (1584cc) or 110CID engines, Nightrider was able to find
horsepower numbers from Harley. As you can see below on the dyno sheet
listed below (Figure 1), the TC96CID engine for Dyna's and Softail'sproduces around 68 horsepower and 83
ft.lb. torque in stock trim. The same bikes with an HD/SE Stage 1 engine makes around 81
horsepower and 96 ft.lb. torque. We have additional HD/SE engine
configuration HP/Torque numbers in our Twin
Cam HP Gallery.
|2007 HD Twin Cam 96CID Dyno Chart
Additional Dyno charts located on FLH based bikes (Figure 5) show the
large difference in power. Stock FLH's produce 71 horsepower and 90 ft.lb.
of torque. This same engine in HD/SE Stage 1 trim makes 79 horsepower and
96 ft.lb. of torque.
The difference in power between Dressers and Dyna/Softails is due to
the exhaust system. FLH's have a very large volume in the exhaust system
which allows the exhaust to fill this space while the noise is being
dampened prior to exiting the mufflers. This shows the benefits of a
crossover in the exhaust and having larger mufflers. While few riders are
willing to put FLH sized mufflers on their Dyna or Softail, it does show
the effectiveness of the FLH exhaust in streetable engine combinations.
Harley-Davidson did publish some interesting power improvement
percentages in the Fall 2006 issue of its Enthusiast newsletter. From the information listed below it must be assumed that you can upgrade
the exhaust system and intake system on your 96CID engine without any
changes to the ECU. Nightrider has historically been a proponent of
exhaust system only upgrades with no EFI remap, but now HD has published
that HD/SE exhaust upgrades and no EFI upgrades can be added to your bike
without warranty implications. The table below summarizes power
improvements as published by Harley-Davidson.