xtremerevolution Posted November 28, 2011 Report Share Posted November 28, 2011 Just curious if anyone has measured this or knows a definitive answer. Is there a difference in the fuel economy of an L67 with a stock 3.8" pulley vs a smaller pulley such as a 3.2"-3.5" pulley? I would imagine that requiring the supercharger to turn more revolutions per engine revolution with a smaller pulley might create a higher parasitic loss, but I'm not sure if its significant. Quote Link to comment Share on other sites More sharing options...
jeremy Posted November 29, 2011 Report Share Posted November 29, 2011 no noticeable difference in mpg when I went down to a 3.4" pulley Quote Link to comment Share on other sites More sharing options...
White93z34 Posted November 29, 2011 Report Share Posted November 29, 2011 from what I understand L67s get better fuel economy with some of the basic bolt ons, (headers, pulley) since you are increasing the efficiency of the engine, the problem lies in keeping your foot off the gas to take advantage of new found efficiencies Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted November 29, 2011 Author Report Share Posted November 29, 2011 from what I understand L67s get better fuel economy with some of the basic bolt ons, (headers, pulley) since you are increasing the efficiency of the engine, the problem lies in keeping your foot off the gas to take advantage of new found efficiencies I suppose so. I've been trying to find out why my fuel economy sucks so bad. There were times when I tried to keep my foot off too and the mileage didn't differ. I average 20mpg city/highway right now. On long road trips, I've managed to pull 23-26mpg highway. Kinda feels like it should be a bit better than that with a 3.4 pulley, headers, and other supporting mods. I may try changing the O2 sensor. I wonder of the 3.29 gearing has something to do with it. Quote Link to comment Share on other sites More sharing options...
Euro Posted November 29, 2011 Report Share Posted November 29, 2011 The 3.29's might have something to do with it. I pull low 20's on city driving, but haven't done a long enough highway trip in a while to calculate highway. How's your tune? Quote Link to comment Share on other sites More sharing options...
White93z34 Posted November 29, 2011 Report Share Posted November 29, 2011 what kind of tune are you running? a modified L36 tune? or a modified L67 tune. I know with my swap my MAP is not fully working (maybe its the MAP itself havent checked) Have you checked your short and long term fuel trims? Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted November 29, 2011 Author Report Share Posted November 29, 2011 Canned tune by I believe it was sinister performance based on my specific mods. I would have done it myself (and did for a while with Bob's HPTuners), but I needed a new PCM from him to make the 03 transmission work. MAP is fully working. When I was tuning it and dialing in the fuel trims, the fuel economy wasn't any different. I'll "tune it up" some time this week by cleaning the MAF sensor and replacing the O2 sensor. I'm thinking it might be the 3.29 gearing. Cruising at 70mph, I'm right around 2500rpm. Quote Link to comment Share on other sites More sharing options...
AL Posted November 29, 2011 Report Share Posted November 29, 2011 I dont think thats your problem... Im running 3.29s on both cars, both are topswapped... Im seeing an average of 25 on the highway with no torque converter lockup on the Regal and the GTP I was seeing a steady 29-30 almost anywhere I went (straight hwy mpgs)... Your MPGs will really start to drop off any higher than 70 mph, 68 seems to be a sweet spot for the Regal Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted November 29, 2011 Author Report Share Posted November 29, 2011 I dont think thats your problem... Im running 3.29s on both cars, both are topswapped... Im seeing an average of 25 on the highway with no torque converter lockup on the Regal and the GTP I was seeing a steady 29-30 almost anywhere I went (straight hwy mpgs)... Your MPGs will really start to drop off any higher than 70 mph, 68 seems to be a sweet spot for the Regal That might be why. All of my highway driving has been 75-80mph depending on the day. I haven't tried driving below 70mph for an entire tank of gas yet... Quote Link to comment Share on other sites More sharing options...
AL Posted November 29, 2011 Report Share Posted November 29, 2011 Doing 80 I sometimes drop very close to 20 because your out of the engines most efficient range (2100-2200rpms)... Try it just once and see what the gains are... Sometimes getting somewhere is more important than the mileage youre getting on the way there Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted November 29, 2011 Author Report Share Posted November 29, 2011 Doing 80 I sometimes drop very close to 20 because your out of the engines most efficient range (2100-2200rpms)... Try it just once and see what the gains are... Sometimes getting somewhere is more important than the mileage youre getting on the way there That would do it then. With the 3.29 gearing, I don't think I'm ever in my efficient range. Even if I'm in the low 70s, I'm turning at least 2400rpm. I'll see what she does when I go 65 the whole way to work a couple of times. Thanks for the insight! Quote Link to comment Share on other sites More sharing options...
AL Posted November 29, 2011 Report Share Posted November 29, 2011 Yah I look forward to seeing the results Quote Link to comment Share on other sites More sharing options...
GP1138 Posted November 29, 2011 Report Share Posted November 29, 2011 I was getting a straight 27mpg at a constant 80mph on my last trip, all highway. But then I do have the 2.93 gearing. Quote Link to comment Share on other sites More sharing options...
Euro Posted November 29, 2011 Report Share Posted November 29, 2011 Who's sinister performance? Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted November 29, 2011 Author Report Share Posted November 29, 2011 Who's sinister performance? http://www.gmtuners.com/ Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted November 29, 2011 Author Report Share Posted November 29, 2011 I was getting a straight 27mpg at a constant 80mph on my last trip, all highway. But then I do have the 2.93 gearing. Yeah...when I drive 80mph, I'm turning nearly 2800rpm. Quote Link to comment Share on other sites More sharing options...
Euro Posted November 29, 2011 Report Share Posted November 29, 2011 Interesting, never came across that site before. I have had pics of that 3800 Lumina on my computer for years, never knew where they came from til now! Quote Link to comment Share on other sites More sharing options...
AL Posted November 29, 2011 Report Share Posted November 29, 2011 At 65 with 3.29s, you should be at 2100 not 2400 rpms Quote Link to comment Share on other sites More sharing options...
9lumina6 Posted November 30, 2011 Report Share Posted November 30, 2011 With the 3.3'' pulley I still averaged just over 30mpg in the Silver GTP. (doing about 75mph). Headers, and exhaust really help. The thing that'l kill your mileage is the urge to hear that supercharger whine . If I stay out of boost....i get better highway mileage than I do in the GT. Quote Link to comment Share on other sites More sharing options...
GtpKo Posted November 30, 2011 Report Share Posted November 30, 2011 I used to do a lot of highway driving in my GTP, 2hrs each way every weekend for 1.5 years. I would consistently average 32-34mpg - according to the DIC and verified with fillups. After headers and intake, I got a sustained 36mpg at 60-ish according to the DIC. Then after I started getting MAF and O2 codes, it went back down to about 31. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted November 30, 2011 Author Report Share Posted November 30, 2011 At 65 with 3.29s, you should be at 2100 not 2400 rpms Its low 70s that I'm turning 2400. I don't remember the last time I drove 65mph on the highway to work. Seems like a MAF cleaning and an O2 replacement might be in order. Something is keeping my fuel economy down. Sent from my HTC Awesome using Tapatalk Quote Link to comment Share on other sites More sharing options...
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