Pete Posted July 12, 2005 Share Posted July 12, 2005 It's just a fuel filter isn't it? Some people like more than one I guess. Quote Link to comment Share on other sites More sharing options...
JohnA Posted July 12, 2005 Share Posted July 12, 2005 If you're talking about the picture I posted, that is a dangerous experiment I did so I could measure the exact AFR change under boost without any 'compensation' signal to the FPR. (this fuel flow reduction you can calculate easily from the pressure differences, but you cannot calculate the fuelling degradation due to the spray pattern change) At 10psi boost I saw AFR 15:1, which was a bit worse than the theoretical calculations predicted. Mine is a UK model, with a LOT more fuelling under full throttle (the injectors are 20% bigger than JSpec, as you know) If that is getting so lean at 10psi, can you image a JSpec at 1+bar? *shivers* The ECU will be none the wiser, as it is operating at open-loop. So it squirts what the maps say, and hopes for the best. It has no way of getting feedback (unlike late designs that run closed-loop under boost) Quote Link to comment Share on other sites More sharing options...
merckx Posted July 12, 2005 Share Posted July 12, 2005 If you're talking about the picture I posted, that is a dangerous experiment I did so I could measure the exact AFR change under boost without any 'compensation' signal to the FPR. (this fuel flow reduction you can calculate easily from the pressure differences, but you cannot calculate the fuelling degradation due to the spray pattern change) At 10psi boost I saw AFR 15:1, which was a bit worse than the theoretical calculations predicted. Mine is a UK model, with a LOT more fuelling under full throttle (the injectors are 20% bigger than JSpec, as you know) If that is getting so lean at 10psi, can you image a JSpec at 1+bar? *shivers* The ECU will be none the wiser, as it is operating at open-loop. So it squirts what the maps say, and hopes for the best. It has no way of getting feedback (unlike late designs that run closed-loop under boost) Yep , frighteningly high AFR. In Jakes case if the rubber tube had come off the FPR and the AFR ratio had shot up, wouldn't the O2 sensor have detected this lean running and shut the engine down? Quote Link to comment Share on other sites More sharing options...
JohnA Posted July 12, 2005 Share Posted July 12, 2005 Yep , frighteningly high AFR. If he was running over 1 bar at the time, I wouldn't be surprised if the AFRs had gone to 17:1 or worse. He didn't stand a chance. In Jakes case if the rubber tube had come off the FPR and the AFR ratio had shot up, wouldn't the O2 sensor have detected this lean running and shut the engine down? No, as I said under such load it runs OPEN loop (i.e. the signal from the O2 sensor is not taken into account) I know of aftermarket ECUs that do use the signal of the narrowband for feedback during full-boost, but OEMs don't do it this way. Quote Link to comment Share on other sites More sharing options...
merckx Posted July 12, 2005 Share Posted July 12, 2005 Appears to be crazy that this pipe coming off can cause such high AFR's resulting in massive damage to the engine. You would think there would be a failsafe way of protecting the engine under these circumstances. Quote Link to comment Share on other sites More sharing options...
JohnA Posted July 12, 2005 Share Posted July 12, 2005 It is possible to do it as a failsafe, but they don't do it. They could have the ECU keep an eye on the O2 sensor, and if it registers 0.7V (or thereabouts) under boost, then play it safe and throw an ECU error and reduce boost at the same time. That's the theory behind AFR gauges anyway, isn't it? If you see 'red' under boost pull your blody foot off the gas. It won't tell you if you run rich enough, but it will tell you if you're too lean. I can't understand how people can be running tuned turbos without an AFR gauge (as an absolute minimum). I'd just feel blindfolded without one. In fact I'd feel blind without a wideband. Quote Link to comment Share on other sites More sharing options...
Alex Posted July 12, 2005 Share Posted July 12, 2005 ...Fuel pressure regulator is spring loaded to a certain pressure from factory the only time they need to decrease this pressure is during idle to have better idle, fuel consumption, emission control etc ... so to achieve that they connected it to the intake manifold to sence vacuum ... and this vacuum will suck the spring/diaphram down a bit to decrease the FB ... and since the only time you have vaccum is when your throttle closed at idle ... so in normal driving conditions the regulator well have no vacuum acting on it and the pressure will be higher. Sorry for the dump explenation but Hope this help !! Ali Hi Ali, What happened with Jake is that he went on boost without his FPR connected (it seems) and this means the FPR didn't see boost pressure to raise the rail pressure in line with the increase in boost. What you've said is true if Jake hadn't gone on boost. In fact Jake was probably running rich till he put his foot down. Quote Link to comment Share on other sites More sharing options...
Jake Posted July 12, 2005 Author Share Posted July 12, 2005 I can't understand how people can be running tuned turbos without an AFR gauge (as an absolute minimum). I'd just feel blindfolded without one. In fact I'd feel blind without a wideband. I'm confused, I thought an AFR gauge was connected to a wideband O2 sensor, no? Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted July 12, 2005 Share Posted July 12, 2005 You can get narrow band AFR or Lambda gauges too. Quote Link to comment Share on other sites More sharing options...
Alex Posted July 12, 2005 Share Posted July 12, 2005 I can't understand how people can be running tuned turbos without an AFR gauge (as an absolute minimum). I'd just feel blindfolded without one. In fact I'd feel blind without a wideband. Because the car was near enough stock...he shouldn't need one...no one should need an AFR gauge on a stock car as if it needed one the OEM would have fitted one. Jake's suffered a terrible piece of hard luck, nothing more nothing less... I totally rely on mine WB02 now I've modded the car and wouldn't be without it but Jake shouldn't have needed it... Quote Link to comment Share on other sites More sharing options...
Ian C Posted July 12, 2005 Share Posted July 12, 2005 I too find it odd, thinking about it, that the engine could lunch itself due to this unclamped hose popping off. There are plenty of hoses on the engine with spring clamps on that really don't need them, and yet the vital FPR ones have no clamps at all... (my Aeromotive pressure reference line is tie-tag clamped on ) Nevertheless, I can't think of a better explanation for a stock motor going pop in such a fashion. Damned bad luck. -Ian Quote Link to comment Share on other sites More sharing options...
The Hornet Posted July 12, 2005 Share Posted July 12, 2005 Right thats it, when I get home I'm lifting the bonnet and checking if mine are clamped / Tie wrapped on. If not, jubliee clips going on at weekend! Sorry to hear about this event matey.. Quote Link to comment Share on other sites More sharing options...
JohnA Posted July 12, 2005 Share Posted July 12, 2005 Bad luck indeed. My bet is that this hose popped off under boost, for two reasons: 1. hoses cannot normally pop off under vacuum, you don't even need to clamp them if they only see vacuum (this one sees both) 2. if it had popped under vacuum the running would be funny. It would be running richer than normal (higher fuel pressure than it should). Yes the ECU would compensate and readjust injector timings to bring it around stoich, but it would also struggle to handle the significant vacuum leak that this popped hose created. Revs would go up and down and Jake would have noticed that something's wrong. Most probably it popped off under boost, and he didn't stand a chance to do anything. An AFR gauge (and a keen eye) would have saved the day perhaps, but as it was stock he wouldn't have fitted one -- I thought it was BPU. Goes to show how marginal fuelling the JSpec has, the UK spec at stock boost runs 14.5-15:1 without this hose. Dangerous, but not immediate-meltdown territory. 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.