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.

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Induction Modifications

There 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.

• Stage 1 Torque Induction Kit - Airbox Mods.
• Stage 1.5 mods - Airbox Mods + internal airbox baffle removed and bottom cut out of filter and airbox.
• Stage 2 mods - Airbox Replacement & Pod Filters.

Induction Comparison Dyno Graphs

The 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: TORS

TORS with Stage 1 Torque Induction Kit - Very strong low-mid range torque compared with Stage 2 mods up to 5,600rpm and although top end power is as strong, it isn't as prolonged as Stage 2. TORS with Stage 2 mods - Slightly better top end power, but a significant loss of torque below 5,600rpm compared to Stage 1.

Exhaust: Long free flowing silencers

Long free flowing silencers over 20"/50cm with Stage 1 Torque Induction Kit - Excellent low-mid range torque with a reduction above 4,500rpm compared to Stage 1.5 and 4,800rpm compared to Stage 2. Long free flowing silencers over 20"/50cm with Stage 1.5 mods - Same torque as Stage 2 up to 3,700rpm and then more torque up to 5,500rpm, but loses out to Stage 2 above 5,500rpm and almost equal to Stage 1 above 6,500rpm. Long free flowing silencers over 20"/50cm with Stage 2 mods - Best overall top end power, but a loss of torque below 4,500rpm compared to Stage 1 and 5,500rpm compared to Stage 1.5.

Exhaust: Short free flowing silencers

Short free flowing silencers under 20"/50cm with Stage 1 Torque Induction Kit - Best torque upto 4,900rpm, but not as much top end power as Stage 2 mods. Short free flowing silencers under 20"/50cm Stage 1.5 mods - Lowest torque figures up to 3,800rpm and then more torque for 1,000rpm than Stage 2 and dropping down to Stage 1 levels above 6,200rpm. Short free flowing silencers under 20"/50cm Stage 2 mods - Best top end power above 5,500rpm, but a loss of torque below 5,000rpm compared to Stage 1.

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Exhaust Modifications

For 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 Graphs

The 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.

Induction: Stage 1 Torque Induction Kit.

Stage 1 with TORS silencers - Best torque up to 4,000rpm and then loses out to short silencers from 4,200rpm and long silencers from 6,000rpm. Stage 1 with long free flowing silencers over 20"/50cm - Loses out to the TORS up to 6,000rpm and then gives a better top end than TORS. Stage 1 with short free flowing silencers under 20"/50cm - Loses out to TORS up to 4,000rpm and the gives an excellent torque boost from 4,200rpm to give a strong mid-top end.

Induction: Stage 1.5 airbox mods.

Stage 1.5 airbox mods with long free flowing silencers over 20"/50cm - Equal in torque up to 3,800rpm, but then the short silencers pull away to give a better mid range and slightly better top end. Stage 1.5 airbox mods with short free flowing silencers under 20"/50cm - The better combination with stage 1.5 giving better figures from 3,800rpm to the rev limiter.

Induction: Airbox Removal & Pod Filters.

Stage 2 mods with TOR silencers - The least power & torque with stage 2 mods. Stage 2 mods with long free flowing silencers over 20"/50cm - Less power & torque than short silencers up to 6,200rpm, then similar figures to the rev limiter. Stage 2 mods with short free flowing silencers under 20"/50cm - The best performing silencer type with stage 2 giving the best power & torque throughout the rev range.

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Stage 1.5 mods vs. Stage 1 Torque Induction Kit & Stage 2 mods

We 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.

Stage 1 vs. 1.5 long silencers

Stage 1 Torque Induction Kit vs. Stage 1.5 mods with long silencers over 20"/50cm - Stage 1 gives good low-mid range torque up to 4,500rpm and then Stage 1.5 gives good mid-high range torque until 6,400rpm at which point the curves are very similar up to the rev limit.

Stage 1.5 vs. 2 long silencers

Stage 2 mods vs. Stage 1.5 mods with long silencers over 20"/50cm - Both Stage 1.5 and Stage 2 give similar torque up to 3,600rpm and then Stage 1.5 gives better torque up to 4,800rpm, from that point to the rev limiter Stage 2 give better power & torque.

Stage 1 vs. 1.5 short silencers

Stage 1 Torque Induction Kit vs. Stage 1.5 mods with short silencers under 20"/50cm - The Stage 1 kit gives much better torque up to 4,800rpm and then from 5,200rpm for approx 1,000rpm the Stage 1.5 improves on Stage 1. Then from 6,400rpm similar curves to the rev limit.

Stage 1.5 vs. 2 short silencers

Stage 2 mods vs. Stage 1.5 mods with short silencers under 20"/50cm - Stage 2 gives beter power & torque throughout the rev range except from 3,600rpm to 5,400rpm where they are very similar.

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EFI America/Speedmaster Power & Torque Quick Reference Guide

Please click the tune number to see the relevant dyno graph.
Tune	Induction	Exhaust	Peak Power (BHP)	Peak Torque (ftlb)	Max Torque Increase
OEM	OEM	OEM	+0.0% (53.08)	+0.0% (48.20)	+0.0%
1	Stage 1	TORS	+8.1% (57.38)	+14% (54.96)	+16.7% @ 4,200 rpm
2	Stage 1	Long Silencers	+9.6% (58.19)	+12% (53.97)	+15.4% @ 4,200rpm
3	Stage 1	Short Silencers	+11.7% (59.29)	+17.7% (56.73)	+21.2% @ 4,600rpm
5	Stage 1.5	Long Silencers	+10.7% (58.77)	+12.6% (54.26)	+16.2% @ 4,600rpm
6	Stage 1.5	Short Silencers	+12.2% (59.55)	+16% (55.88)	+19.6% @ 4,700rpm
11	Stage 2	TORS	+8.8% (57.75)	+7% (51.80)	+9.7% @ 4,700rpm
12	Stage 2	Long Silencers	+13.7% (60.35)	+11.3% (53.65)	+14.6% @ 4,600rpm
13	Stage 2	Short Silencers	+15.5% (61.32)	+15.7% (55.78)	+19.7% @ 4,700rpm

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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.

Mike

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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.

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All text and dyno run graphics are copyright of Triumph Twin Power ©2008-