SMW Posted February 15, 2003 Share Posted February 15, 2003 I posted on this a while back and have since been to Leon's and mentioned it to him. He made a small adjustment to my boost controller reducing the top setting from 70 to 67. This seemed to have done the trick at least until today when I hit fuel cut twice. The highest recorded on the DSBC was 1.38, boost gauge confirmed this. After the first instance of cut I reduced the top setting to 63 but once again experienced fuel cut soon after (at least it didn't occur until after I'd dispensed with the Merc SL500 that had been sitting on my tail for the previous 2 miles Further reduced the setting to 60 after this and took things a little easier for the rest of my journey. Drove pretty hard on the way back though but never boosted above 1.26 I have a TRL fuel cut device fitted and if I understand correctly it has an overboost protection feature that prevents the car boosting beyond 1.4 bar?? I have stage 2 hybrids and am running on Optimax so I don't want to exceed that figure, just slightly confused as to why the data from my DSBC and boost gauge doesn't indicate 1.4 bar + Is this something for me to be concerned about or should I concentrate on fine tuning the boost controller settings to prevent it happening in the future? Quote Link to comment Share on other sites More sharing options...
Thorin Posted February 16, 2003 Share Posted February 16, 2003 I'd trust a boost gauge more than the displayed figure on a boost controller. I think with the TRL thingymajig once you raise it above a certain level (1.3 I think) it effectively removes the fuel cut limit completely. Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted February 16, 2003 Share Posted February 16, 2003 Yes the TRL VFCC (FCD) will only have an active OVERBOOST protection at the maximum readable pressure measurement from the MAP sensor. i.e. you cannot set the overboost setting above about 18.5 (19psi) as this is the max the MAP sensor can read. (giving 4.95V out) If you set the overboost to any other setting it will not be able to trap the overboost and initiate fuel cut. if you look at the VFCC Settings you'll see that the setting close to 4.95V is B. This is the default position I set all VFCC's to. If you change the setting to C,D,E,F; the VFCC will now ONLY remove fuel cut and you have to look after the overboost yourself. It is a limitation of the stock MAP sensor. It is also assumed that if you intend to go above 19psi then you should really have had other items added to aid correct fueling etc. I'd be very careful in thinking itis fuel cut, when in fact it might be detonation and/or spark plugs dying/breaking down at high boost. This MAY be fuel cut but remember...... Fuel Cut is not only a function of boost pressure but TIME! Fuel cut will ONLY happen if you have exceeded the maximum boost threshold setting for say 2s. Now 2s is a long time and you could have strayed from the new overboost 19psi max and be closer to 22psi or whatever by the time fuel cut happens. The only cure for this is to reduce the gain of the boost controller, the attack rate to the boost setting selected is too great leading to massive overshoot. This is the thing with tuning these boost controllers. You have to find a critically damped setting that will work in the majority of cases. Sounds like you're still tweaking to find this critical point. (currently you're underdamped) Regards Pete Quote Link to comment Share on other sites More sharing options...
Steve W Posted February 16, 2003 Share Posted February 16, 2003 SMW (and Pete!), at Santa Pod today, I was experiencing 'something' at higher revs/boost (~5,500revs at full throttle). It was like a slight hesitance/holding back but with no noises I took it a 'little' easier at those higher revs/boost for the day ! ! I've never changed the plugs and have no reason to believe they're anything other than standard, so, I'll first try the '7's in case the 'de-catting' is straining the '6's ? ? ? [i was running Esso S/U with Millers CVL so think the fuel was OK ? but, it WAS very cold up there, so, = higher boost ? ? ps. slap my wrist, but, STILL haven't got boost guage yet ! !] Quote Link to comment Share on other sites More sharing options...
SMW Posted February 16, 2003 Author Share Posted February 16, 2003 Pete Thanks for explaining the VFCC settings. I'm pretty sure what I experienced was fuel cut as the symptoms match exactly what has been described by others. From what you have said it's clear that my settings on the DSBC need looking at, I'll spend some time trying to sort this out. Cheers Steve Quote Link to comment Share on other sites More sharing options...
Mohammed_A Posted February 17, 2003 Share Posted February 17, 2003 Guys was out last about 11ish,and as I was flooring the car at about 5.5-6.5K it would jerk and the hazard ligh came on with an orange oil light as well. I totally forgot to look at the boost gauge,is this fuel cut? Also,also what boost is fuel cut activated at? As if this was fuel cut, like to get a rough idea of what amount of boost I was getting last night,I must add it was freezing,and the car was at its quickest since purchase! Any help appreciated! Quote Link to comment Share on other sites More sharing options...
SMW Posted February 17, 2003 Author Share Posted February 17, 2003 the hazard ligh came on with an orange oil light as well Sounds like it could well be fuel cut to me. Has your boost gauge got a peak hold feature? If it has you should be able to see what boost level you reached. Also,also what boost is fuel cut activated at? I think it depends what type of FCD you've got. Some of them just remove fuel cut altogether I think. Quote Link to comment Share on other sites More sharing options...
Mohammed_A Posted February 17, 2003 Share Posted February 17, 2003 I'm not sure whether it has a peak hold feautre,it's aGreddy one though,does peak hold just hold the needleat the higest level of boost reached,so that so that you can see what max boost you got. If this is the case then it most probably dosen't have this feature,but also I didn't watch the boost gauge once as was alarmed as to what was happneing with the car. I was thinking that mabe the freezing cold whether could have caused an up in boost,but does anyone know what boost has to be reached in oreder for the fuel to be cut? Cheers Steve! Heard that fitting fcd is mad as they just make the turbos go..and on leading to a higher chance of failure.But seeing as most people putting them on are using hybrids/hks/trust tubbies is ok,but with normal j-spec's and uk ones, I was advised not to fit the FCD. Hope I don't hit this fuel cut all the time as I couldn't be able to stand it! Any help? Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted February 17, 2003 Share Posted February 17, 2003 Steve, yours sounds like iffy plugs/gaps. I had the same problem. Fuel cut is more definate... You have more of a 'bang' and the engine/hazard light come on, by the time you've thought "Shit, what have I broken", it all goes back to normal. (Assuming you've backed off!) Mo, are you sure it was the oil light?!? - It should be the engine light and the hazard/warning triangle.... Or at least that's what mine did Quote Link to comment Share on other sites More sharing options...
Mohammed_A Posted February 17, 2003 Share Posted February 17, 2003 Yeah Matt it was probably the engine light mate.... Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted February 17, 2003 Share Posted February 17, 2003 Heard that fitting fcd is mad as they just make the turbos go..and on leading to a higher chance of failure.But seeing as most people putting them on are using hybrids/hks/trust tubbies is ok,but with normal j-spec's and uk ones, I was advised not to fit the FCD. This is exactly why I put the warning on my site (but about fuel not ceramic turbos I admit) http://www.trlperformance.com/vfcc.html This is also why I added an overboost protection facility. i.e. I remove fuel cut at the stock setting of 15psi and replace it at a user selectable pressure. By default I leave them at 19psi. So the turbos can go on and generate more boost but the overboost setting will trap any boost above the NEW fuel cut threshold, set by the VFCC. So once again you're safe. Or safer than without it. The device can also remove fuel cut altogether if you wish to boost higher and have sorted out the fueling yourself. Regards Pete Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.