Jake Posted May 2, 2006 Share Posted May 2, 2006 I've fitted an AEM Wideband gauge (AEM 30-4100) and taken the car out for a spin. When cruising along on partial throttle at any speed, even like 100mph, the AFR varies from about 14:1 to 15.5:1. Does that sound OK? But, when I accelerate hard the AFR goes off-the-scale rich. As soon as it comes on full boost with WOT the gauge display dives to 10:1 and stays there until I let off. (This wideband can only display AFRs between 10:1 and 20:1) That's not right, is it? At the moment I'm running the car (93 RZ Auto by the way) with the boost controller turned off and using a CW restrictor ring. It was hitting 0.95bar max today. The car doesn't feel slow, it feels just as powerful as usual to me but if those AFRs are correct the car is running way too rich, isn't it? What would cause that? Is the stock lambda sensor used at WOT? (I always forget whether it's used in closed or open loop) Any thoughts? Thanks Quote Link to comment Share on other sites More sharing options...
tDR Posted May 2, 2006 Share Posted May 2, 2006 Partial throttle seems fine, and my car with just a walbro gets similar AFR's on full throttle whilst peaking at similar boost levels to yours. On first turbo I see around 12:1 and as soon as the 2nd comes in my AFR's jump to a steady 10:1. This is silly rich but I attribute it to the walbro pump raising the base fuel pressure 3 or 4 psi. Lambda sensor is only used for closed loop, IE throttle shut. I'd blame it on an uprated fuel pump if you have one or a dodgy FPR. Cheers, Brian. Quote Link to comment Share on other sites More sharing options...
bignum Posted May 2, 2006 Share Posted May 2, 2006 sounds strange, only thing i can tell you is that at wot the lambda is not in play, so open loop. Quote Link to comment Share on other sites More sharing options...
Alex Posted May 2, 2006 Share Posted May 2, 2006 I've fitted an AEM Wideband gauge (AEM 30-4100) and taken the car out for a spin. When cruising along on partial throttle at any speed, even like 100mph, the AFR varies from about 14:1 to 15.5:1. Does that sound OK? But, when I accelerate hard the AFR goes off-the-scale rich. As soon as it comes on full boost with WOT the gauge display dives to 10:1 and stays there until I let off. (This wideband can only display AFRs between 10:1 and 20:1) That's not right, is it? At the moment I'm running the car (93 RZ Auto by the way) with the boost controller turned off and using a CW restrictor ring. It was hitting 0.95bar max today. The car doesn't feel slow, it feels just as powerful as usual to me but if those AFRs are correct the car is running way too rich, isn't it? What would cause that? Is the stock lambda sensor used at WOT? (I always forget whether it's used in closed or open loop) Any thoughts? Thanks Yes the AEM only displays down to 10:1 (actually mine stopped at 11.3:1). Have you gone all the way to 7000rpm to see if it's still off the clock rich there? If it is you could probably lean it out with an eManage or through more boost (lol)...Toyota programmed the MAP (it's not the Lambda on WOT that's for closed loop cruising and idle) to run rich and safe. I think it sounds like normal behaviour for a Stock ECU'd and turbo'd Supra. Quote Link to comment Share on other sites More sharing options...
Jake Posted May 2, 2006 Author Share Posted May 2, 2006 my car with just a walbro gets similar AFR's on full throttle whilst peaking at similar boost levels to yours. On first turbo I see around 12:1 and as soon as the 2nd comes in my AFR's jump to a steady 10:1. This is silly rich but I attribute it to the walbro pump raising the base fuel pressure 3 or 4 psi. I'd blame it on an uprated fuel pump if you have one or a dodgy FPR. Yes, I do have a Walbro fuel pump - I should have mentioned it in the initial post, sorry. It's fully decatted as well. Quote Link to comment Share on other sites More sharing options...
Homer Posted May 2, 2006 Share Posted May 2, 2006 Jake, I was just about to make a very similar thread. From 4.5k to 5k it will be around 12.2 then go down to 10.8 until redline. Alos, anytime going from partial to full throttle while on boost it goes off the scale for a second or two. I've got an aeromotive fpr at 40psi, might bring this down a few psi and see if that helps. Have you checked the fuel pressure on your car? Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted May 2, 2006 Share Posted May 2, 2006 A lot of turbo cars tend to have the stock ECU maps run pretty rich at full boost, more a safety feature, it would be better at about 11.- 11,5.1 and best power is up around 12.2.1 but there is no safety margin, your only a bit of det away from disaster! and like Alex says it could well lean out again at peak RPM. Quote Link to comment Share on other sites More sharing options...
Ian C Posted May 2, 2006 Share Posted May 2, 2006 I concur, it's rich for safety reasons. You could pull some fuel out to 11.8:1 or thereabouts and get some power with no loss of safety margin IMO. Also, the 14:1 to 15.5:1 bounce is the closed loop hunt and is also normal. It'll do it until you get past 4000rpm so you'll get closed loop up to about 115mph. Cool huh? -Ian Quote Link to comment Share on other sites More sharing options...
Jake Posted May 2, 2006 Author Share Posted May 2, 2006 Thanks for all the replies. No Alex, I've only had it up to 5650rpm so far. Too much traffic about to be playing "WOT and looking at me gauges". I'll go out later and find some clear road. Darryl, no idea what fuel pressure it's running TBH. I always thought it would remain at the stock pressure even with a Walbo pump, seeing as it's still using the stock FPR. I'm wondering just how rich it's really running, seeing as this wideband only goes to 10:1, it could be running really rich for all I know. When I had the same car Dyno'd at Thor ages ago it was running lean at high boost and on the stock fuel pump. Pete was having to take his foot off the throttle at 1.15 bar because of the 13:1AFR at 5000rpm. Maybe I'll turn the boost controller back on and see what the AFRs are like at 1.15 bar now I have the Walbro pump. Quote Link to comment Share on other sites More sharing options...
Alex Posted May 3, 2006 Share Posted May 3, 2006 Maybe I'll turn the boost controller back on and see what the AFRs are like at 1.15 bar now I have the Walbro pump. Sounds like a plan to me Quote Link to comment Share on other sites More sharing options...
Mcgoo Posted May 3, 2006 Share Posted May 3, 2006 Just fitted my AFR, I'm j-spec, decatted, 1.1 restrictor ring, walbro, FCD, and my readings are almost identical to this. 14.5 to 15 .5 on idle and normal driving up to around 4k rpm, after that between 10.5 to 11.5 all the way to red line. Wasnt sure if that was right, but sounds ok then? just a tad rich under boost? Quote Link to comment Share on other sites More sharing options...
jason m Posted May 3, 2006 Share Posted May 3, 2006 Will be getting mine fitted soon - I am assuming that if it does a similar thing then this can be tuned out with the e manage... Quote Link to comment Share on other sites More sharing options...
Jake Posted May 13, 2006 Author Share Posted May 13, 2006 *Update* I've beening running the car with the boost controller at 1.2 bar for a few days now. The AFRs seem better at this boost level. It's a consistant 11.2/11.3 under WOT runs (6500rpm max, 1.21 bar peak) 11.3 AFR is pretty good isn't it? Nice and safe? It's great to be able to check your AFRs on the fly. Gives you a nice peace of mind. Quote Link to comment Share on other sites More sharing options...
Homer Posted May 13, 2006 Share Posted May 13, 2006 Cheers for updating the thread, that could explain why mine is so rich now. Since the warm weather arrived the boost is now only just over 1 bar. Think I'll invest in a boost controller to get it back to 1.25 bar... Quote Link to comment Share on other sites More sharing options...
Jake Posted May 13, 2006 Author Share Posted May 13, 2006 That's a good point D, cheers. If I keep an eye on the AFRs would I be safe to push the boost up a bit further, to 1.25 or 1.3 bar? Or do I need to consider EGTs as well as AFRs? What I mean is, do the two things go hand in hand or can you have good AFRs and dangerously high EGTs? Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted May 13, 2006 Share Posted May 13, 2006 What I mean is, do the two things go hand in hand or can you have good AFRs and dangerously high EGTs? Unfortunately no! ignition timing plays a big part to, if your on a std ECU then you should be ok, but just because you AFRs are good it does not automatically mean that EGTs are good. Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 14, 2006 Share Posted May 14, 2006 ...or can you have good AFRs and dangerously high EGTs? yes you can. EGTs are also a function of exh backpressure and cam timing. That's why big singles can keep EGTs low. By the way I gained 30-odd bhp by keeping my AFRs to 12.5 (instead of the stock 10s). That's how much the safety margins of 'richness' cost in power terms. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted May 14, 2006 Share Posted May 14, 2006 yes you can. EGTs are also a function of exh backpressure and cam timing. That's why big singles can keep EGTs low. By the way I gained 30-odd bhp by keeping my AFRs to 12.5 (instead of the stock 10s). That's how much the safety margins of 'richness' cost in power terms. Good point! forgot all about cam timing:senile: Quote Link to comment Share on other sites More sharing options...
Chiefgroover Posted May 14, 2006 Share Posted May 14, 2006 OK, I could be way off here but if the vvti model report is a problem due to emissions, perhaps its that 10.5 AFR thats causing the problem. If so couldnt we find a way of discreetly changing this a bit to get it to pass? Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 14, 2006 Share Posted May 14, 2006 Probably not, the 10:1 is at full throttle conditions. Quote Link to comment Share on other sites More sharing options...
Chiefgroover Posted May 14, 2006 Share Posted May 14, 2006 yes but dont they test all conditions, its not an mot! Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 14, 2006 Share Posted May 14, 2006 True Quote Link to comment Share on other sites More sharing options...
Ian C Posted May 14, 2006 Share Posted May 14, 2006 *Update* I've beening running the car with the boost controller at 1.2 bar for a few days now. The AFRs seem better at this boost level. It's a consistant 11.2/11.3 under WOT runs (6500rpm max, 1.21 bar peak) 11.3 AFR is pretty good isn't it? Nice and safe? It's great to be able to check your AFRs on the fly. Gives you a nice peace of mind. The reasons for this is - your injectors are at 100% duty cycle The stock ECU, once it sees boost creeping towards 1bar, goes into a "fackinell" mode and just opens the injectors full. Any boost past 1bar and it then just cuts the fuel as something has obviously gone wrong But you run an FCD so that means once you reach about 0.98bar you're flat out on your fuel system. So, at 1bar you run very rich. So you add air by turning the boost up to 1.2bar and that balances out to the low elevens. Nice and safe and doesn't sap too much power. The stock setup doesn't run 10.5:1 at full boost (0.8bar), only when the injectors are flat out, so I doubt it's just that which stopped the VVTi being sold. Toyota didn't miss that trick 12.5:1 is all very good but 13:1 can see the onset of det, especially with stock turbos heating up the charge air. If an extra 30bhp is worth running that close to shagging your engine then that's great I map to 11.8:1 -Ian Quote Link to comment Share on other sites More sharing options...
supra matt Posted May 14, 2006 Share Posted May 14, 2006 im fitting mine soon i got welbro full decat 1 bar ring and frount mount . if its rich could i use a safc 2 to take the fule out at top end? sorry for the hijack . Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 14, 2006 Share Posted May 14, 2006 im fitting mine soon i got welbro full decat 1 bar ring and frount mount . if its rich could i use a safc 2 to take the fule out at top end? sorry for the hijack . You could, but take it easy and be conservative. As Ian said from 13:1 onwards you risk dicing with detonation, especially if your intercooling is not up to the job and the fuel is not fresh and high-octane. I personally aim for a figure of '99RON' displayed clearly on the pumps (I have also run it at 13:1 with a tad more power still, but I also inject lots of water/methanol so under boost my charge temps are lower than expected, and the octane rating is higher than otherwise. ) Quote Link to comment Share on other sites More sharing options...
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