Richyd Posted September 2, 2007 Posted September 2, 2007 I have just fitted a cat by-pass pipe onto my 1.6ss with DVA's Emerald kit (DTH Jenveys, Emerald ECU, airbox, verniers). The car was mapped by Dave Walker a few weeks ago and it was low on power. A subsequent compression test and leak-down test has shown that 3 cylinders are losing compression. So, whilst I wait for DVA to return from hols (I guess he may recommend we lift the head to see what is going on), I still want to take the car out for a good blat from time to time (also, I have a trackday in a few weeks plus Dunsfold handling day next week). With the cat removed, the car now backfires big time whenever I lift off the throttle, then go back on the gas.... Whilst this is good fun, I am already getting a little too much attention from my neighbours. So, the quick question was meant to be, does anyone know if I can adjust the fuelling on the Emerald a little to compensate for the Cat removal and dial out some of the pops and bangs......?? This will hopefully be a temporary measure for a month or so until DVA can look at the engine, and then I'll have Mr Walker re-map afterwards... I am a little nervous about it running too lean, as I do not want to damage the engine at WOT, so any advice would be gratefully received..... Cheers - Rich He's only gone and DVA'd it!!..here
MattC Posted September 4, 2007 Posted September 4, 2007 Rich I had a backfire coming down from high revs on a closed throttle, caused by the mixture going too lean to ignite. Unburnt fuel ends up in the exhaust where it explodes Try richening up the map a tad for closed throttle position at mid to high rpm Matt
Ray Pearce Posted September 4, 2007 Posted September 4, 2007 The Emerald (or mine at least) has a 'Fuel cut-off on overrun' option on the Events tab which is designed to sort this out for you. Is this enabled? If so, are the settings reasonable? Oh- and the backfiring is likely to be due to air leaks at the joints in the exhaust rather than the lack of Cat Ray Edited by - Ray Pearce on 4 Sep 2007 17:05:18
Richyd Posted September 4, 2007 Author Posted September 4, 2007 Cheers - the backfire happens when I come off the gas and then gently apply a little pressure on the throttle........ If I do not go back on the gas it does not backfire..... He's only gone and DVA'd it!!..here
MattC Posted September 4, 2007 Posted September 4, 2007 What I think is happening is that you have zero fuel on the overrun but when coming back on throttle the fuel cannot be instantly switched back on at exactly the right mixture..... (this is different to my problem as I kept fuel in the map for zero throttle) Rich, do you know if 'Fuel cut-off on overrun' is enabled? Not sure what the options are here on Emerald, can you twiddle the rpm at which the fuel cuts back in? Alternativey try adding a little fuel in the map at the rpm / load sites that your're getting the pop Oh and Ray is right, check for any air leaks in the exhaust system......... Matt
Ray Pearce Posted September 4, 2007 Posted September 4, 2007 If I remember correctly, the fuel cut-off takes a throttle-pot position and rpm setting. If the throttle is below that specified and the revs above then it cuts the fuel = no bangs. If you get bangs when you tickle the throttle during overrun then increasing the throttle-pot value a bit should sort it.
Richyd Posted September 4, 2007 Author Posted September 4, 2007 Cheers - Will get the laptop out on Thursday night to have a peek at what is going on...... He's only gone and DVA'd it!!..here
Grubbster Posted September 4, 2007 Posted September 4, 2007 Mine pops and bangs a lot on overrun (following a number of upgrades including an Emerald), but I haven't bothered about it much as I am going for a mapping session in a couple of weeks, I assume that will sort it? I never expected it to run as well as it does without having it set up on a rolling road so I'm not dissapointed. For reference I can confirm the fuel cutoff on overrun is not enabled at the moment (maybe I should switch it over and see if it makes a difference?)
MattC Posted September 4, 2007 Posted September 4, 2007 Grubbster I assume that will sort it? Not neccssarily as it's impossible to exactly replicate real driving on a rolling road! I was very pleased with my rolling road session (quick plug for Northampton Motorosport) but ended up with the backfire on the overrun that I didn't have before! If you haven't enabled the fuel cutoff on overrun then you can richen up the TP1 sites to get rid of the pops and bangs Matt
Richyd Posted September 5, 2007 Author Posted September 5, 2007 Update - Went out for a blat last night and, just to stop any confusion, these are full blown backfires with flames!!!! 😬 - not your run of the mill pops and bangs... I only want to rein this in a bit as I am at Dunsfold on Saturday morning and I don't want Anthea Turner to get her knickers in a twist Plus I have a trackday in a few weeks and do not want to get black-flagged... He's only gone and DVA'd it!!..here
Richyd Posted September 8, 2007 Author Posted September 8, 2007 Okay guys - feedback as promised... I emailed Dave Walker at Emerald and his advice was as follows... First check that the overrun cut off box is ticked on F2. if not tick the box and send the map down. Next alternative is to try altering (up or down) the fuel line on load zero above 2500 rpm - overrun not ticked. I set the first option at 11 O'clock last night as the overrun fuel cutoff was not ticked - had good thrash at Dunsfold this morning, and all sorted Thanks for the advice guys - you were both spot-on... He's only gone and DVA'd it!!..here
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