I created and experimented with a unique combined bellmouth and cold air intake which gave me very good results, albeit only measured with the arse dyno...I thought it looked good as well. I was surprised when I looked at Triumph-online.co.uk site the other day to see that they're marketing such a mod and, on following the link to the instructions, it turns out that it is to my post on this forum describing the mod...nobody asked me!. This is a link to where it's being marketed:
See my write-up here: http://www.triumphrat.net/twins-tech...ir-intake.html
That, rather indiscrete mod, was rendered obsolete by the fitting of PJ Glassfibre's subtle and elegant vented side panels. Lovely, well-made bit of kit, it funnels lots of cold air into the intake:
More about it here: http://www.triumphrat.net/twins-tech...ide-panel.html
Incidentally, Peter has a new, updated website that's a bit easier to use than the old one, although it contains lots of apostrophe abuse...
Up until now the most elaborate and expensive one was offered by Norman Hyde. This takes the form of a heavy and IMHO over-engineered alloy casting that substitutes the airbox cover completely and incorporates a bellmouth profile. It seems reasonable to assume that due to the work and investment in tooling needed to create this, proper airflow studies were made and indeed it flows better than most of the others according to Pieman's own research. Unfortunately on Normans site it just says that it "improves performance". No proof or details are given. Strangely, for EFI aplications it says that no re-mapping of the ECU is needed. This is somewhat suspect as any appreciable increase in airflow has to be entered in the tune map tables to gain anything. The cost is rather high at £76+tax.
See it here: https://normanhyde.co.uk/hinckley-tr...bellmouth.html
Mike at TTP (Triumph Twin Power)
has studied most of these examples and as a result of long, painstaking research and considerable investment in time and cash, has come up with what I think is the definitive performance airbox cover. Not only does it flow better than all the others, and he has the figures and dyno charts to prove it, but it's much lighter and cheaper than the nearest rival at £59+tax, as well as flowing nearly 30% more air.
See it here:
As with the OEM cover, it's made of plastic, but of much better quality, finish and appearance. It maximises the airbox opening consistent with proper sealing around the filter element. Together with a DNA filter and restrictor removal he can show important power gains, specially when combined with the usual exhaust mods and a re-map of the ECU.
I can't say how this works for carbed models though, some re-jetting will be neccessary but, being an EFI man, I can't say.
As an added refinement that none of the others contemplate, he supplies a rain guard to be added to the side cover to stop any water getting into the airfilter. I did not fit mine for two reasons: 1.- I don't ride in the rain if I can help it and 2.- The PJ Glassfibre vented side cover wraps around the frame and airbox opening a lot closer than the OEM cover and stops any water getting in.
Note that the link given above also contains instructions on fitting and the history of its development, worth reading. There are also comparison charts showing its effectiveness and relevant dyno charts. More dyno charts are shown on a recent thread discussing the BREATHE airbox cover, here, see posts 20 and 30:
I've made my own comparison chart to show the percentage airflow gains:
Airflow figures in CFM (Cubic feet per minute)
Type of air intake---------------------CFM---------- % Improvement over OEM
OEM cover with snorkel....................215
OEM cover without snorkel...............422..................+96% over OEM
OEM cover with Polaris Bellmouth.....448..................+108% overOEM
Aluminium Bellmouth.....................623................. .+189% over OEM
TTP Breathe..................................793...... .............+268% over OEM
This is what it looks like fitted. Photo courtesy of the first member that has fitted one, Ric from Bristol (aka m2MQP):
Don't forget to transfer the sealing ring from the OEM cover to ensure no unfiltered air can get past the new cover:
I know that Pieman won't be too pleased with my carving up his cover to incorporate one of my favourite mods, but it was very easy given that the material is very easy to cut and the curved section is hollow, the cover being moulded in two pieces bonded together.
It involves the relocation of the IAT sensor to the entrance of the airbox rather than being buried in the depths of the airbox, behind the blind end of the air filter element, where it's over-heated and transmits erroneous temperature info to the ECU. I don't understand why the Factory has done this, I imagine they just placed the sensor in the same place as the carb heater thermostat was fitted on carbed models. Very poor this. I only have to look at where Mazda fitted their sensor to my MX-5 (Miata) to see that I'm on the right track, it's right on the end of the cold air intake ducting, right on the entrance to the airbox, where it should be, to provide accurate data.
The way ours is fitted works OK for the first 10 miles or so, beyond that the sensor attains a much higher temperature than the real air coming into the engine and not only weakens the mixture but also retards the timing to avoid detonation due to what it thinks is a high ambient air temperature. You can see this in real time using TuneECU or a hand-held code reader/scanner. This mod retains the same level of performance and driveability that's as good at the end of a journey as at the start.
If you fancy reading more about this mod there are two links to look at: