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HD 2007/2008 Engines

High Heat on 2007/08 HD engines

HD 2007/08 Performance Recommendations

Cool your exhaust temperature with the Wide Band O2 upgrade for 2007/08 HD

Harley Camshaft Specification Tables

HD Twin Cam Engine Builds
TC 128 HP 95 CID
TC 100HP Street Engine

The basics of Fuel Injection explained

DEWEY'S CUSTOM
Rammer Performance Air Cleaners
TC Performance Heads 100+HP

Pro Tuning on a Shade Tree Budget

   
Harley-Davidson Performance Guide

Calculate Exhaust Header Length

Maximum Horsepower Output

Tuning the exhaust system can be an important component in achieving maximum power when optimizing the performance of an engine for racing or dyno shootouts. While not recommended for street bikes, the use of drag or straight pipes can maximize the horsepower produced by any specific engine combination. The RPM range that the straight pipes produce their maximum power is very narrow. The best ways improve the performance of straight pipes is to "tune" the exhaust length to the required power band.

Determining Exhaust Pipe Length

Opinions differ as to the best exhaust pipe lengths for any engine. There appears to be two major "schools" of thought on the best exhaust system length. The "short" pipe and "long" pipe calculations performed below present both views. Short pipes seem to win from an esthetics point of view, but the longer pipes seem to produce a better power curve. The decision of which to use is up to you.

Any formula that calculates header pipe lengths must take into account conditions such as exhaust temperature, gas speed, exhaust valve duration and the RPM the engine is running at. Each formulae makes different assumptions about these items resulting in different results from the same basic input parameters. The formulas used here result in short and long pipe length being calculated.

For serious performance efforts, the pipe lengths are calculated for a 3-step drag pipe. This 3-step design has generally proven to give the highest horsepower results over any other design. 3-step pipes are generally a custom build pipe.

There are two pieces of information that must be supplied in order to determine the exhaust pipe lengths for an engine.

  1. The RPM's for the middle of the desired power band is needed. For Harley-Davidson applications the following RPM values would be typical: a street engine will be 4000-5000, a street/strip engine 4500-5500, race engines 5000-6000 and dyno shootout engine 5500-6500.

  2. The opening point of the exhaust valve is required. This number must be reported as degrees BBDC ( Before Bottom Dead Center ). The default value used in the calculations is for an Andrews EV-3. The EV-3 is a general purpose cam that works well in stock engines and reacts positively to more extensive engine modifications such as increased compression and air flow. Determine the value for the camshaft in your engine. Values for stock HD, Andrews and Crane cams are listed below.

What is the RPM in the middle of the power band? RPM
What is the opening point of the exhaust valve BBDC? degrees

Short Pipe

Long Pipe

Total Length in inches
Step 1 length exhaust header
Step 2 length middle section
Step 3 length exhaust outlet

Some specifications for common camshafts are listed below.

Manufacturer

Cam Grind

Intake Open BTDC

Intake Close ABDC

Exhaust Open BBDC

Exhaust Close ATDC

HD Stock 92-98

"N" Grind -02 30 31 -09

Andrews

EV13

15

31

45

13

Andrews

EV27

20

36

44

16

Andrews

EV3

21

37

43

15

Andrews

EV35

21

37

52

20

Andrews

EV46

25

41

49

17

Andrews

EV51

28

44

54

22

Andrews

EV5

28

44

52

20

Andrews

EV57

26

46

59

27

Andrews

EV59

28

48

56

24

Andrews

EV72

30

54

60

28

Andrews

EV79

31

55

64

32

Andrews

EV7

31

56

59

27

Andrews

EV81

32

60

66

30

Andrews

EV84

32

64

70

30

Andrews

EV88

34

70

76

32

Crane

Fireball 300

12

34

41

15

Crane

Fireball 310

16

40

43

19

Crane

H290

17

43

45

23

Crane

Fireball 316

19

43

48

24

Crane

H286

19

43

48

24

Crane

Fireball 326

24

48

57

25

Crane

H296

24

48

57

25

Crane

H304

24

50

55

25

Crane

H314

26

54

65

21

Crane

H306

28

54

69

23

Crane

H310

23

63

68

28

 

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Modification, Installation, Maintenance and Tuning Index  will help you find most of the information you want on one page.

How to get Professional Tuning Results at home
Testing the Innovate Motorsport LM-1 portable air fuel meter

Profession Tuning on a Shade Tree Budget

Veypor VR2 Data Logger and Instrument Panel
Video Installation and Demo
Purchase VR2


Engine Performance
How to Build a
TC96 2007 Engines
TC88 70HP Stage1  
TC95 128HP Stage 3
TC95 100HP Street
 
TC96 2007 Stage 1/2
EVO 64 HP Stage 1
EVO 74 HP Stage 2
EVO 82 HP Stage 3
EVO 95 HP Stage 3
883 to 1200 Upgrade
Shovelhead Modifications

New EFI for EVO and TC

Performance Gallery
Horsepower Gallery
Evolution 80
Shovelhead
Sportster
Twin Cam 88/95
Evolution Unlimited
Sportster Unlimited
Drag Strip Gallery
Land Speed Racing Gallery
CV Carburetor
Modifying the CV carb
Tuning a CV carb
Camshafts
Selecting a cam
Install a TC 88/95 cam
Install a Big Twin cam
Install Sportster cams

Camshaft Specifications
Twin Cam
EVO
Shovel
XL


Exhaust Systems
EVO Exhaust Testing
TC Exhaust Testing
Khrome Werks AR100 test
Making Drag Pipes Work

SHOP TALK
Shop Manual
Carburetor
Carburetor Troubleshooting
Exhaust
Ignition
Finding Manifold Leaks
Camshafts
Cylinder Heads
Pistons and Cylinders
Clutch
Belt Drive
Shop Manual Appendix
$20 Bike Lift
Plug Wires
Spark Plugs
Engine Tuning
Nitrous Oxide
Motor Oil
Stutter Box
General Information
WEB Links
Buy Books and Manuals
Miscellaneous
Performance Calculations
Estimate Horsepower
Estimate 1/4 Mile Time
Estimate Top Speed

Engine Displacement
Exhaust Length
Gear Ratios
MPH at RPM
Air Density

The Nightrider Diaries
The ramblings of a genius a, a madman and something in between.

Where is Sifton Cams?

Autocom Active-7 tested

Harley-Davidson EFI
-EFI basics explained
-EFI modifications explained

183 HP, 2 carbs, 2680cc

Copyright 1997-2006  Stephen Mullen, Oldsmar, FL -+-