Let me rephrase, 15 is my max lean out on the low side of narrow throttle... the majority of the time it's around 10-12. And no, I didn't use a air/fuel meter to tune, I just got really good results in gas mileage when I changed it to that... I originally had a 4% lean throughout the narrow throttle.
Gray
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____99 Prelude - FIVE SPEED ____
Phuck the Sportshift Tranny
I have got a AEM CAI, AEM Fuel Rail, AEM Fuel Pressure Regulator (Currently set at 50 psi), AEM Tru-Power Pulleys, Greddy Evo Exhaust, and now a VAFC... that's about it for the engine modifications. For some reason I was getting horrible gas mileage after my mods. I was thinking that the computer must have been running really rich to compensate for the extra flow of air coming from the CAI, but I am not for sure. My performance is great, but what kind of damage could I do from running lean. I would like to keep the good gas mileage, but if I am going to hurt something I can deal with out it.
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____99 Prelude - FIVE SPEED ____
Phuck the Sportshift Tranny
There's a guy named Deadly-Lude on www.honda-tech.com that is in the process of a full rebuild on his 1998 Prelude motor. He had a V-AFC that he "street tuned" by using the settings that felt like they gave him the most power... He had crazy lean settings like you. Then he started burning lots of oil. Well after a compression test, he found he had only about 90-100 PSi/ cyl compression... His rings were shot due to running too lean.
Originally posted by aklucsarits There's a guy named Deadly-Lude on www.honda-tech.com that is in the process of a full rebuild on his 1998 Prelude motor. He had a V-AFC that he "street tuned" by using the settings that felt like they gave him the most power... He had crazy lean settings like you. Then he started burning lots of oil. Well after a compression test, he found he had only about 90-100 PSi/ cyl compression... His rings were shot due to running too lean.
Just took a day trip to see what kind of mpg I was getting. Running 50 psi Fuel Pressure, and 10% lean correction on the VAFC at 3400 rpms for the majority of the time... I got 27.92 mpg. And that's on a Sportshift. I definitely don't want to **** my rings up, considering I only have 43000 miles on the car... but that is some really good gas mileage compared to what I was getting. Could the Fuel Rail and the 50 psi compesate for the 10% lean to make it some what of a good a/f ratio? What is the stock a/f ratio anyway?
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____99 Prelude - FIVE SPEED ____
Phuck the Sportshift Tranny
Our cars dont need to be leaned out that much in narrow throttle. What you need to do is get it tuned with a wide band o2 sensor. The $150. of dyno time is a lot less than an engine rebuild would be. I would think about that if I were you.
At narrow throttle.... the air/fuel ratio is pretty good.... you might want to lean it out a little.... say 2%-4%.... but thats it!!!
At wide open throttle we run RICH and should be leaning it out a little more....... most people lean it out 5% and by the time they hit 8k rpm... it'll be leaned out to 7%-8%.....
This is with your standard i/h/e.... and its pretty much a perfect air/fuel ratio.......
damn 27.92 mpg on a SS is so tempting though... someone please figure these phenomenon out. I'm getting 17.5 mpg. That's a lot of money in gas and might be comparable to the engine rebuild.
__________________ And I... don't know why, I just... fall into the meadow.
Originally posted by 01XLude At narrow throttle.... the air/fuel ratio is pretty good.... you might want to lean it out a little.... say 2%-4%.... but thats it!!!
At wide open throttle we run RICH and should be leaning it out a little more....... most people lean it out 5% and by the time they hit 8k rpm... it'll be leaned out to 7%-8%.....
This is with your standard i/h/e.... and its pretty much a perfect air/fuel ratio.......
But once again I am running 50 psi of Fuel Pressure... stock the prelude sits in the mid 40's. I guess until someone who has dabbled in the dyno let's everyone know what's up... I will move it back to 4% lean in the narrow throttle.
Gray
But I am sure going to miss 28 mpg when I am getting 17-18 again
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____99 Prelude - FIVE SPEED ____
Phuck the Sportshift Tranny
whats up with this 17-18 mpg im hearing about? i thought thats what f'body's get. does this seem wierd to anyone? not saying its not true, i only get 20 and im not even modded, but damn...
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1999 Prelude 2.2 VTi 4WS
I speak fluent typo
I am pretty sure the raising of the fuel pressure and leaning of the VAFC is a very good mod, you just need to have it tuned with a wideband for exact AF readings. The leaning out via the VAFC also advances timing, so raising the fuel pressure and leaning with the VAFC gives timing a little boost while maintaining AF ratios.... What made you decide to raise pressure and lean with the VAFC? I suggested this to one person on another board a few months ago....... Interesting....
BTW, I get 20+ mpg city/highway and 9psi on occassion with 440cc injectors......
Originally posted by nuro whats up with this 17-18 mpg im hearing about? i thought thats what f'body's get. does this seem wierd to anyone? not saying its not true, i only get 20 and im not even modded, but damn...
wha? i'm not clear bout wha you're tryin' to say. f'body completely threw me off.
__________________ And I... don't know why, I just... fall into the meadow.
ok ill be more clear. we dont get good gas mileage. i am comparing our gas mileage to that of f-body cars. From what i hear, we get the same, yet they have over twice the displacement that we do. doesnt that kinda piss u off?
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1999 Prelude 2.2 VTi 4WS
I speak fluent typo
Originally posted by nuro ok ill be more clear. we dont get good gas mileage. i am comparing our gas mileage to that of f-body cars. From what i hear, we get the same, yet they have over twice the displacement that we do. doesnt that kinda piss u off?
The only reason that recent GM F-body cars get half decent EPA milage ratings is because their transmissions lock out 2nd and 3rd gear from a standing start under basically anything but WOT acceleration. In other words, the tranny goes from 1st gear directly to 4th gear when they are accelerating normally.
not only that but we have half as many cylinders so taking gearing into consideration our rpms are double or more when crusing in the same gear/speed. Cruising at 90 mph in a Prelude as I do every day to get to work you go through a lot of gas! We really needed a 6th gear for fuel economy...
and that gm thing is *****. my friend had the dealer take it out.
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98 Prelude
Events Co-ordinator and Moderator Toronto Prelude Club
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