AdC Posted June 6, 2016 Share Posted June 6, 2016 As above really. I'm used to the occasional burble / pop when decelerating but yesterday there were a couple of proper 'old-style' BANGS when accelerating hard and changing up - scared the bejesus out of me!Should I be concerned? Will my inside rear arch explode? Has my engine gone out of tune (carb'd Fireblade)? I've recently had a Flatshifter fitted if that's a possible culprit...Any ideas? Ta'. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 6, 2016 Member Share Posted June 6, 2016 I've recently had a Flatshifter fitted if that's a possible culprit... What does that involve for the ignition and fuel and air supply?JonathanPS: Quiz of the day: In which James Bond book is this noise made deliberately? Link to comment Share on other sites More sharing options...
AdC Posted June 6, 2016 Author Share Posted June 6, 2016 There's a pressure switch on the gear lever. When you start to pull the lever it senses you're about to change up and kills the spark momentarily, allowing the engine to decelerate enough to comfortably slot the next gear in. All without using the clutch or needing my right foot to relax any pressure. Have I answered my own question? Carbs wide open, fuel and air going in, but no ignition until it gets to a hot exhaust? :-) Link to comment Share on other sites More sharing options...
SM25T Posted June 6, 2016 Share Posted June 6, 2016 That's how we used to scare the High Streets in the days of carburettor engines. Ignition off for a few secs while car still moving. The backfires could do some damage though ! Link to comment Share on other sites More sharing options...
AdC Posted June 6, 2016 Author Share Posted June 6, 2016 Laughs. Now you've told me, SM25T...What is the potential damage? All the wadding burnt or blown out of the back? Or more serious? Link to comment Share on other sites More sharing options...
Ivaan Posted June 6, 2016 Share Posted June 6, 2016 I have one fitted to my BEC, but it has a separate on/off switch in the power feed.When you're going slow, or in traffic, you'll be using the clutch as normal, so don't want the ignition to cut out.Sounds like it may be set up wrong, with too long a cut out allowing too much unburnt fuel to build up.Mine's set for milliseconds, just to unload the gearbox when you're pulling back the gear lever, but the timing must be right. I don't tend to use mine much, as I prefer a quick throttle peddle lift to do clutchless upshifts. Does your's blip when going down the box?Probably no harm done. What exhaust can do you have?Clive. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 6, 2016 Member Share Posted June 6, 2016 Sounds like it may be set up wrong, with too long a cut out allowing too much unburnt fuel to build up. I was wondering what adjustments are there on these?AdC: I presume your engine has a working engine speed limiter... Jonathan Link to comment Share on other sites More sharing options...
Simon.Rogers Posted June 6, 2016 Share Posted June 6, 2016 Absolutely the Flatshifter.Listen to any car with proper flat shift and they will do that. They are cutting spark but the fuel is still going in - unburnt fuel exiting and bobs your uncle.Proper closed loop systems should not do it but I do still here it regularly and we were discussing this at Gurston last weekend.If its an injection set up that works as it should the injectors are cut also = no bang! Link to comment Share on other sites More sharing options...
AdC Posted June 7, 2016 Author Share Posted June 7, 2016 Thanks Ivaan, there is some adjustment so I'll have a twiddle.I replaced the original non-repackable James Whiting exhaust with an Andy Bates (AB Performance) one last winter because it was struggling with Brands' noise levels. I'm yet to find out how much quieter it is but I notice that Brands' levels have reduced again in the meantime...Hi Simon - I don't think I'm serious enough for a closed loop system, nice as they are!Jonathan - it does have a rev limiter, but it's somewhere north of 12,000rpm I believe. I'm curious why you want to know now! Okay next q - why does the rev counter needle drop momentarily to zero during the shift? I'm thinking it's not good for the longevity of the counter. Does the counter read the spark for it's information? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 7, 2016 Member Share Posted June 7, 2016 ... why does the rev counter needle drop momentarily to zero during the shift? I'm thinking it's not good for the longevity of the counter. Does the counter read the spark for it's information?At what point does the flatshifter cut the ignition? The feed to the rev counter must be downstream of that. I wouldn't worry about the instrument.... it does have a rev limiter, but it's somewhere north of 12,000rpm I believe. I'm curious why you want to know now!Because if I was going to back off eg the duration of cutting with the throttle wide open and no load on the engine I'd like a security blanket... :-)But for this protection you'd need an engine speed feed that isn't disconnected when you need it!Experts, please: how is this usually managed?Jonathan Link to comment Share on other sites More sharing options...
garybee Posted June 7, 2016 Share Posted June 7, 2016 "why does the rev counter needle drop momentarily to zero during the shift?" Your rev counter is looking at pulses from the ignition coil to determine engine speed. No pulses = engine not turning (as far as the tacho is concerned). Link to comment Share on other sites More sharing options...
elie boone Posted June 7, 2016 Share Posted June 7, 2016 When your exhaust is not air tight it allows air in and thus resulting in a louder bang Link to comment Share on other sites More sharing options...
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