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Exhaustive
Analysis Here we are going to look at what each of several exhaust systems will do for your 1340 IF IT IS NEARLY STOCK.
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I emphasise those words as these exhausts may prove far more restrictive on a bike that has had other modifications and been given a better power output.
The bike used here is near-stock: a 1995 FatBoy with the stock air-stopping airfilter removed and replaced with a good one from previous air filter tests. We also fitted a DynoJet kit to allow us to change the mixture to suit each pipe where needed.
In order to avoid clashing with the stock rev-limiter at the top end of the rev range we swopped on to a Screamin' Eagle ignition module.
Then it was down to work. A useful tip at this point for those of you who are replacing your pipes is to buy some Sperex heat-resistant matt-black paint and spray it INTO the exhaust. I said 'into' not 'onto'! This must be done before the pipes are ever used - it doesn't work afterwards. We have given this tip out more times than I care to remember over the last 20 years - but some of you are new to the game so it bears repeating.
This has the effect of slowing down or totally stopping the blueing of the pipes. Well worth the bother if you want the pipes/bike to stay looking good.
Now to the numbers - our first effort was a base-setting run with the stock mufflers. This gives us the direct comparison to work with through the tests. The following list of numbers may not look like a great deal - but the amount of time and effort that went into making sure we were giving good comparisons was a nightmare.
Here are the stock numbers:-
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2500
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2750
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3000
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3250
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3500
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3750
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4000
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4250
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4500
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4750
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5000
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5250
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5500
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Stock:
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29
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33
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36
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39
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42
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46
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48
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50
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52
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53
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53
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52
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50
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The pipes we tested against the stock ones were:- |
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Screamin'
Eagle slip-on
tapers (stock headers): |
32
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37
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40
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44
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49
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53
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56
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59
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60
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61
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62
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61
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59
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Thunderheaders:
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33
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38
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41
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46
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51
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55
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58
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60
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62
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63
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63
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61
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59
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Rev-Tech
taper duals:
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32
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36
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40
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43
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49
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53
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56
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57
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59
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60
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59
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57
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55
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Bub
Bad Dogs:
|
33
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37
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40
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45
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49
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53
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55
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57
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58
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58
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58
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56
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55
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ARII
2" Anti-reversion
drag pipes: |
32
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34
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37
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41
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46
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50
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54
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58
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60
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61
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61
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59
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56
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SuperTrapp
2 into 1:
|
36
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36
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39
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44
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49
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53
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55
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58
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60
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61
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61
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59
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57
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In the normal operating range choosing the correct pipes for your bike can gain or lose you 5bhp - the same you would hope to gain by fitting a sport camshaft. Choose your pipes carefully.
For those who like to compare torque figures here are the numbers, measured in lbs/ft in the useable range for two of the set-ups above comprared to the stock set-up.
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3000
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3500
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4000
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Stock:
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63
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64
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63
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Thunderheaders:
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73
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76
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76
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ARII
Dragpipes:
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65
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68
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71
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I hope this all helps a little.