RedM Posted May 13, 2007 Share Posted May 13, 2007 I've been wondering. We have a fuel cut system on the Supra and we have the means to prevent it. Why does the ECU cause fuel cuts and does using a FCD mean that we are potentially doing harm to our cars? Link to comment Share on other sites More sharing options...
ardasaliah Posted May 13, 2007 Share Posted May 13, 2007 The ecu has fuel cut to protect the turbos and engine from damage. Over boosting will cause premature turbo damge- People want more power so they fit FCD but at the cost of reduce reliability. Link to comment Share on other sites More sharing options...
RedM Posted May 13, 2007 Author Share Posted May 13, 2007 People want more power so they fit FCD but at the cost of reduce reliability. So, I was sort of correct then that fitting a FCD will cause the engine to suffer. What's the better way to avoid this? Boost controller? Link to comment Share on other sites More sharing options...
AndyT Posted May 13, 2007 Share Posted May 13, 2007 So, I was sort of correct then that fitting a FCD will cause the engine to suffer. What's the better way to avoid this? Boost controller? Got to fit a restrictor £15 that limits boost to 1.2 bar thus protecting the engine and turbos etc. Homers BPU faq is ace for this info... Link to comment Share on other sites More sharing options...
Wez Posted May 13, 2007 Share Posted May 13, 2007 Boost/fuel cut is 1bar stock isnt it. A 1.2bar restrictor on its own would have you bouncing off the cut which would not be very nice. Link to comment Share on other sites More sharing options...
letmeshowyou Posted May 13, 2007 Share Posted May 13, 2007 the biggest point is... it's a failsafe in case things go wrong (preventing a massive overboost situation) The Thor one lets you keep the boost cut at a raised limit Martin - definitely worth considering Link to comment Share on other sites More sharing options...
RedM Posted May 13, 2007 Author Share Posted May 13, 2007 the biggest point is... it's a failsafe in case things go wrong (preventing a massive overboost situation) The Thor one lets you keep the boost cut at a raised limit Martin - definitely worth considering What would you set it to? 1.25bar? 1.3? How often is 1.2 bar reached in a BPU car? Link to comment Share on other sites More sharing options...
letmeshowyou Posted May 13, 2007 Share Posted May 13, 2007 as I understand it you can set it to what you like. Personally I don't see 1.2 very often anyway (running off the boost controller so it's 1bar for most road use and 1.2 for the drag strip) Link to comment Share on other sites More sharing options...
jamesmark Posted May 13, 2007 Share Posted May 13, 2007 Or you could down the route of fitting a 1bar RR and using a boost controller to raise the boost, this giving you a little bit more than stock as stock is arounf 0.7-0.8 bar. You will still need the FCD for when you do raise the boost, but at least you still have more control (safeguard) than a 1.2 bar RR. As mentioned above depends if you're turbos and engine will let you go to 1.2 bar. Link to comment Share on other sites More sharing options...
Nic Posted May 13, 2007 Share Posted May 13, 2007 So, I was sort of correct then that fitting a FCD will cause the engine to suffer. What's the better way to avoid this? Boost controller? Upping the boost above stock level will reduce the life of the engines and turbos however you do it. You would still need an FCD fitted even using a boost controller to raise the boost. An FCD basically fools the signal to the ECU, so it doesn't think the car is going over the stock boost cut and so doesn't cut fuel. Link to comment Share on other sites More sharing options...
Wez Posted May 13, 2007 Share Posted May 13, 2007 Then the you ask, if it doesnt know how much boost its running how does it fuel it correctly Link to comment Share on other sites More sharing options...
RedM Posted May 13, 2007 Author Share Posted May 13, 2007 What causes the damage that the ECU and it's fuel cut are seeking to prevent? I'm assuming that it's just turbo related as big singles run at more than 1.0bar but have aftermarket ECUs too. Link to comment Share on other sites More sharing options...
RedM Posted May 13, 2007 Author Share Posted May 13, 2007 Then the you ask, if it doesnt know how much boost its running how does it fuel it correctly Bloody good question. I'm guessing it over fuels. Right? Link to comment Share on other sites More sharing options...
jamesmark Posted May 13, 2007 Share Posted May 13, 2007 Then the you ask, if it doesnt know how much boost its running how does it fuel it correctly One of those things I guess that the search button is your friend. I believe you use one of those Apexi things I can't remember the letters that go after it. Link to comment Share on other sites More sharing options...
edge Posted May 13, 2007 Share Posted May 13, 2007 Then the you ask, if it doesnt know how much boost its running how does it fuel it correctly Could well be true as ive recently read the people who have gone single seem to get better mpg? Link to comment Share on other sites More sharing options...
jamesmark Posted May 13, 2007 Share Posted May 13, 2007 Or again he could be bored and winding us up since it has been done to death already, unless Mawby has broke the search button. Link to comment Share on other sites More sharing options...
Nic Posted May 13, 2007 Share Posted May 13, 2007 Got to fit a restrictor £15 that limits boost to 1.2 bar thus protecting the engine and turbos etc. Homers BPU faq is ace for this info... A restictor ring does limit the boost to a certain extent, it is not a fail safe though and doesn't prevent the turbos from overboosting, if say a pipe was to split or come loose. Boost levels can also vary depending on the temps, ie. in winter the boost may go slightly higher than in the summer. The better FCD's raise the fuel cut level rather than remove it completely, which means you still have a margin of safety if the car does unexpectly overboost. Link to comment Share on other sites More sharing options...
RedM Posted May 13, 2007 Author Share Posted May 13, 2007 Could the whole FCD, restrictor ring, boost controller route be avoided by using an aftermarket ECU that is set up properly? I'm not sure what is happening to cause the damage that the ECU/FC is seeking to avoid but it does seem that the BPU bits are just a fudge to get more power for minimum expense but with a risk of reduced reliability/longevity. Link to comment Share on other sites More sharing options...
jamesmark Posted May 13, 2007 Share Posted May 13, 2007 The better FCD's raise the fuel cut level rather than remove it completely, which means you still have a margin of safety if the car does unexpectly overboost. Which is one of the reasons to stay clear of the HKS FCD as this completely removes it iirc. The Greddy one is the one to go for since Thor have stopped doing the TRL one. Link to comment Share on other sites More sharing options...
AndyT Posted May 13, 2007 Share Posted May 13, 2007 A restictor ring does limit the boost to a certain extent, it is not a fail safe though and doesn't prevent the turbos from overboosting, if say a pipe was to split or come loose. Boost levels can also vary depending on the temps, ie. in winter the boost may go slightly higher than in the summer. The better FCD's raise the fuel cut level rather than remove it completely, which means you still have a margin of safety if the car does unexpectly overboost. Bows to the wisdom. Will be needing you for when I go BPU next year Nic.. Link to comment Share on other sites More sharing options...
jamesmark Posted May 13, 2007 Share Posted May 13, 2007 Could the whole FCD, restrictor ring, boost controller route be avoided by using an aftermarket ECU that is set up properly? I'm not sure what is happening to cause the damage that the ECU/FC is seeking to avoif but it does seem that the BPU bits are just a fudge to get more power from minimum expense but with a risk of reduced reliability/longevity. The aftermarket ECU is an exspensive way of doing it, I asked Rob this and you could probably go full BPU inc decats(not exhaust & smic) than the cost of an ECU. Link to comment Share on other sites More sharing options...
RedM Posted May 13, 2007 Author Share Posted May 13, 2007 Or again he could be bored and winding us up since it has been done to death already, unless Mawby has broke the search button. Aimed at me? I'm just curious to know if there is a reason why everyone follows the BPU route re: parts. Is there a better way and, if so, why isn't everyone doing that? Is it more expensive? Is it harder to get right? I've just posted above that BPU seems like a cheap-ish fudge and a fudged job is usually done to keep costs or complexity down. Link to comment Share on other sites More sharing options...
Jake Posted May 13, 2007 Share Posted May 13, 2007 Could the whole FCD, restrictor ring, boost controller route be avoided by using an aftermarket ECU that is set up properly? It would be expensive and really you're never going to get a standalone mapped as well as Toyota have done. You couldn't stop the turbos overboosting though. A stand-alone ECU can't compensate for the undersized j-spec wastegate. Link to comment Share on other sites More sharing options...
jamesmark Posted May 13, 2007 Share Posted May 13, 2007 Aimed at me? I'm just curious to know if there is a reason why everyone follows the BPU route re: parts. Is there a better way and, if so, why isn't everyone doing that? Is it more expensive? Is it harder to get right? I've just posted above that BPU seems like a cheap-ish fudge and a fudged job is usually done to keep costs or complexity down. If this is you're feelings go single then, save up £6k ish iirc for a small single. Job done. Link to comment Share on other sites More sharing options...
Wez Posted May 13, 2007 Share Posted May 13, 2007 Could the whole FCD, restrictor ring, boost controller route be avoided by using an aftermarket ECU that is set up properly? The restrictor ring is needed due to the mechanics of the motor over boosting when there is less restriction in the exhaust, no electronics can prevent/stop it. A replacement ECU does replace the need for FCD, SLD and boost controller but its an expensive way of doing things. Link to comment Share on other sites More sharing options...
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