Just had a thought (idea from General Discussion), i'm still new to FI and i haven't really pay attention to my fuel mileage lately, but just wondering how everyone's fuel mileage with FI (turbo or SC).
Thanks
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^^ damn i used to get like 300ish before turbo...now im LUCKY to hit 250...210~220 on average
Errr...not to be a dick but it sounds like you need some tuning...or to lay off the boost! With a good mix of driving (including a decent amount of boosting) I still go 270-290 on a fillup...with all highway and taking it easy I've gone 320-330...
--Ian
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'01 Prelude SH w/ stuff
12.3@118
Just WTF is that supposed to mean...he's got a greddy kit. Obviously _you_ don't know _my_ setup. Just because he's got a hondata doesn't necessarily mean it doesn't still need to be tweaked for part throttle driveability/mileage. Most tuners out there simply tune WOT and max power. I've spent countless hours on mine tweaking and getting my every day driveability better than it was stock.
--Ian
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'01 Prelude SH w/ stuff
12.3@118
Just had a thought (idea from General Discussion), i'm still new to FI and i haven't really pay attention to my fuel mileage lately, but just wondering how everyone's fuel mileage with FI (turbo or SC).
Thanks
I want to throw in something interesting here. If you have an EMS that has closed loop wideband capability (all the expensive ones do, like AEM), you can tune for high vaccum for A/F ratios leaner than 14.7. A local AEM EMS tuner routinely tunes H22s for 16:1 at cruise without any issues, and he says that with the right map he can improve MPG by about 4 on average. You can tune other ECUs for leaner than 14.7:1, but you have to do it open loop, which is touchy. Most lesser ECUs don't have the type of throttle-open compensation to prevent detonation at lean cruise, even if you do manage to get a <14.7:1 ratio.
Something to think about.
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Im not sure what you mean by tuning closed loop or open loop? Are you referring to closed loop as setting the A/F ratio using the feedback coming from the o2 sensor and open loop would just be setting fuel on a table without any feedback from the o2 sensor?
Im not sure what you mean by tuning closed loop or open loop? Are you referring to closed loop as setting the A/F ratio using the feedback coming from the o2 sensor and open loop would just be setting fuel on a table without any feedback from the o2 sensor?
Correct. Open loop is used on most ECUs because the engine is responding faster than the feedback is provided by the O2 sensor. Since nearly all cars have narrowband (NB) O2 sensors, the only A/F those sensors can read is pretty much 14.7:1. At WOT, you want to be richer than that, so reading a NB sensor is pretty much useless because it can't tell you anything useful.
Hondata/Uberdata can only run closed loop at 14.7:1. As far as I know, nobody has figured out the part of the OEM code that runs closed loop. Therefore, the closed loop code always shoots for 14.7:1 using a NB sensor, just like stock. You could target other A/F ratios, but you would have to turn off O2 feedback (run open loop) and tune it all by hand using a wideband. Running open loop is kinda dangerous at high vaccuum (low load), because environmental factors (air temp, humidity, intake breathing, fuel quality) have a much larger effect on combustion. If you are running close to the lean detonation limit, which I would say is leaner than 15:1, you need a high degree of ECU control to keep the mixture exactly where you want it. Open loop pretty much eliminates any feedback, so any significant change in environmental factors will change your A/F, and you would have no way of correcting it. In closed loop, the ECU will figure out if the A/F is going to lean (or rich) and take corrective action.
Another issue is that Hondata/Uberdata (H/U) does not have the throttle tip-in correction necessary to pull a lean A/F to a reasonable A/F when acceleration is desired. So if your cruising at 16:1 and you want to pass someone, you need the ECU to add fuel when you step on the throttle (and get the mix closer to 13.5:1 before the MAP sensor responds). Apparently this can't be done well enough with H/U, but the AEM can do it.
I hope this makes sense. Some of the topics here are kind of advanced tuning issues, but I did my best to explain it.
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well I was just wondering if you drive it hard all the time. I'm built and running a full bar but still get anywhere from 250-280. I mean, it can be less but very rarely do I hit as low as you.
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I want to throw in something interesting here. If you have an EMS that has closed loop wideband capability (all the expensive ones do, like AEM), you can tune for high vaccum for A/F ratios leaner than 14.7. A local AEM EMS tuner routinely tunes H22s for 16:1 at cruise without any issues, and he says that with the right map he can improve MPG by about 4 on average. You can tune other ECUs for leaner than 14.7:1, but you have to do it open loop, which is touchy. Most lesser ECUs don't have the type of throttle-open compensation to prevent detonation at lean cruise, even if you do manage to get a <14.7:1 ratio.
Something to think about.
That's exactly how I tune most of the hondas that I deal with...low throttle/low load I usually aim for 15.5-ish, I'll usually ride shotgun and pull fuel with low load until the car starts getting a lean surge or pop then add a bit back in. As long as you've got the accell fueling down it works great. I've gotten the best results when I spent a good bit of time tuning this open loop and then enabling closed loop operation...just seems smoother.
--Ian
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'01 Prelude SH w/ stuff
12.3@118
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Just WTF is that supposed to mean...he's got a greddy kit. Obviously _you_ don't know _my_ setup. Just because he's got a hondata doesn't necessarily mean it doesn't still need to be tweaked for part throttle driveability/mileage. Most tuners out there simply tune WOT and max power. I've spent countless hours on mine tweaking and getting my every day driveability better than it was stock.
That's exactly how I tune most of the hondas that I deal with...low throttle/low load I usually aim for 15.5-ish, I'll usually ride shotgun and pull fuel with low load until the car starts getting a lean surge or pop then add a bit back in. As long as you've got the accell fueling down it works great. I've gotten the best results when I spent a good bit of time tuning this open loop and then enabling closed loop operation...just seems smoother.
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