This part of the TTP X-Files is about tuning the Triumph America and Speedmaster with bolt-on modifications. It outlines our experiences using different induction and exhaust configurations which are outlined below.
The America and Speedmaster are different to the rest of the range as they have a very different airbox design compared to the Bonneville, Thruxton and Scrambler. This combination of airbox design and the camshaft setup Triumph used gives better mid range torque than any of the other bikes in the range.
The initial dyno run was carried out on a factory standard 2010 EFI Speedmaster with around 3500 miles on the clock and the SAI system removed. The induction modifications used were the TTP Stage 1 Torque Induction Kit and Stage 2 mods (i.e airbox removal and DNA pod filters installed). We also tried what we call the stage 1.5, this involved cutting out the internal airbox baffle and also modifying the airbox and filter so that they could breathe from the bottom as well as the top of the airbox. The stage 1.5 mods didn't prove to be a beneficial experiment, but we'll explain more about that later. The exhaust silencers used were the Triumph Off Road Silencers (TORS), free flowing short silencers of less than 20"/50cm (not including link pipe) and free flowing long silencers of more than 20"/50cm (not including link pipe). All of the dyno graphs shown have the 'OEM Factory' run as a comparison.
Induction ModificationsThere are two common variations of induction modification for the Amrica/Speedmaster. There is also the less common mods which we decided to experiment with (Stage 1.5) as there are owners that have tried this method and we wanted to see if these mods were beneficial or not. Deciding on which airbox mods are right for you is very much dependent on how much power you want, where you want the power to be produced and how much time and money you're willing to invest in your bike.
Induction Comparison Dyno GraphsThe dyno's below compare each of the induction systems with a specific exhaust system. This enables you to see what effect changing the induction has on your chosen exhaust.
Exhaust ModificationsFor our exhausts selection we chose TORS, long free flowing silencers over 20"/50cm and short free flowing silencers under 20"/50cm as these are representative of the most used silencers by owners of the America and Speedmaster. With silencers, if the exhaust note is louder, then generally they give better power at the top end and sometimes in the mid-range unless little thought has gone in to the silencer design.
Exhaust Comparison Dyno GraphsThe dyno's below compare each of the three pairs of silencers with each of the induction systems. This enables you to see what effect an exhaust has on a particular induction system.
Stage 1.5 mods vs. Stage 1 Torque Induction Kit & Stage 2 modsWe decided to experiement with what we call Stage 1.5 mods as there are owners of the America/Speedmaster who have carried these mods and we wanted to cater for them with our EFI tunes. Stage 1.5 mods involve cutting out the internal airbox baffle and also cutting out the bottom of the airbox and air filter so the engine can breathe from both top and bottom of the airbox. (Click on the graphic to the right to see what's involved)
The results of these mods are varied and in my opinion, for the time and effort involved, not worth doing. In general you lose low-mid range torque that you gain with the stage 1 and the top end power isn't as good as with Stage 2 mods. But, we carried out the work so the tunes are available on the EFI tunes section if the power & torque curves suit your style of riding and you want to carry out the work involved.
EFI America/Speedmaster Power & Torque Quick Reference Guide
America/Speedmaster Induction & Exhaust Conclusion.After all the development and testing we carried out, we came to the conclusion that Triumph did a great job on the airbox and camshaft combination for the America/Speedmaster cruisers. No matter which combination of induction and silencers we tried, the best low-mid range torque was achieved with the standard airbox modified with our Breathe airbox intake cover and DNA Performance air filter along with the appropriate tune or jetting kit (Stage 1 Torque Induction Kit).
You can achieve higher peak power figures with stage 2 mods (airbox removal & pod filters), but for low-mid range torque improvement which suits a cruiser style bike, you can't beat the standard airbox modified with our stage 1 kit. For this reason we didn't develop a "Stage 2 Power Induction Kit" for the cruisers as the low-mid range torque sacrifice far outweighs the small increase in top end power that can be achieved with a stage 2 kit.
If your riding style on your Triumph cruiser calls for the ultimate top end power, there are a couple of airbox removal kits on the market for the America/Speedmaster, but we decided not to make or market one. Having said that, we can supply the excellent high surface area DNA Performance Pod Filters, DNA crankcase breather filter and EFI tune for your stage 2 project.
The stage 1.5 mods were worth experimenting with, but to be honest, if you want low-mid range torque then our stage 1 kit beats stage 1.5 and if you want absolute top end power stage 2 mods are the way to go.
In conclusion, for the best low-mid range torque for your cruiser, you can't beat our EFI Stage 1 Torque Induction Kit or Carb Stage 1 Torque Induction Kit and a pair of short free flowing silencers. The down side to this combo is that short silencers are generally louder in volume than any other silencer type, which may not suit some owners. If this applies to you, then TOR silencers from Triumph aren't a bad bet as they are relatively quiet and apart from top end power over 6,000rpm, give better low-mid range torque over the long free flowing silencers which are louder than the TORS.
If your riding style requires the best top end power regardless of low-mid range torque, then the short free flowing silencers will be best for you with a stage 2 airbox removal kit.
We hope this article will help you to be informed about the bolt on power mods available and may help to make your America/Speedmaster right for you.
Keep the rubber side down and ride safely.
We have a guide on how to remove the internal airbox baffle HERE and our testing on air filters HERE determined which filters to use.
All text and dyno run graphics are copyright of Triumph Twin Power ©2008-