Horrible gas mileage...
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TECH Fanatic
Joined: Oct 2002
Posts: 1,255
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From: nor cal (ripon)
Horrible gas mileage... Lately im looking at 13mpg and my low end is pathetic..im THINKING that im really rich 
When i Tuned her i had cats and macs, and we never got an accurate a/f, now i changed to pacesetters and ORY/cutout.. i know low end will lack but damn my mpg is horrible 
When i Tuned her i had cats and macs, and we never got an accurate a/f, now i changed to pacesetters and ORY/cutout.. i know low end will lack but damn my mpg is horrible 
Teching In
Joined: Dec 2001
Posts: 387
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From: Southern IN, USA
You mean you tuned PCM with an Editor? What baseline and factors were used in determining spark and fuel maps over OEM?
Is the X1 cam an efficent cam or does it have much overlap? Did you modify valvetrain?
I do hope you know that 4.11 gears are not good for mileage!
What other mods have you that increase drag, friction or fuel use (big radio, sticky tires, etc...)?
Normally one who modifies finds MPG irrelivant, and Ii am interested in why this is an issue here?
What about alignment, tire pressure, routine maintenance, air filter, and other obvious items.
Throwing any codes?
Have any vacuum leaks?
Generally, if you were rich enough for it to hurt your MPG that much, you'd have melted platinum coming out your carbon coated exhausts, and a small fire in the passenger compartment where the cats torched the mats!
What dynanic conditions were you using to calcualte A/F ratio - wideband of course, but at WOT, part throttle, cruise, coast, idle???
What regimen were you optimising for - remember best power in a typical (naturally aspirated) gasoline engine is like 12 to 1 AF, Stoich is 14.5 to 1 (best compormise) and best MPG is like 16 to 1 as a general rule...
FYI my basically stock 2000 Z28 with 66K miles gets a steady 23 -25 MPG around town (really it's real rural) and 28 to 30 on long trips.
Tell us more!
Is the X1 cam an efficent cam or does it have much overlap? Did you modify valvetrain?
I do hope you know that 4.11 gears are not good for mileage!
What other mods have you that increase drag, friction or fuel use (big radio, sticky tires, etc...)?
Normally one who modifies finds MPG irrelivant, and Ii am interested in why this is an issue here?
What about alignment, tire pressure, routine maintenance, air filter, and other obvious items.
Throwing any codes?
Have any vacuum leaks?
Generally, if you were rich enough for it to hurt your MPG that much, you'd have melted platinum coming out your carbon coated exhausts, and a small fire in the passenger compartment where the cats torched the mats!
What dynanic conditions were you using to calcualte A/F ratio - wideband of course, but at WOT, part throttle, cruise, coast, idle???
What regimen were you optimising for - remember best power in a typical (naturally aspirated) gasoline engine is like 12 to 1 AF, Stoich is 14.5 to 1 (best compormise) and best MPG is like 16 to 1 as a general rule...
FYI my basically stock 2000 Z28 with 66K miles gets a steady 23 -25 MPG around town (really it's real rural) and 28 to 30 on long trips.
Tell us more!
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Joined: Mar 2002
Posts: 1,421
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From: Your Reality Check Bounced...
I could get 20+mpg w/my X1....it's an efficient cam. I'd check ur 02 sensors, foot and plugs....just do a tune up on the ole gal..and u'll never ever get the X1 to be as gooda cam as it should w/that stupid tuner you have....
Thread Starter
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Joined: Oct 2002
Posts: 1,255
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From: nor cal (ripon)
actually my tuner is one of THE best out there...he had just never done a car with cats before LOL..he got a stock head ls1 to 422whp with a tr230 and a moser.. I guess ill just get it fine tuned for the new setup and see what happens..ill check the plugs and o2's as well.(what can i physically see on the 02's)?
Check for exhaust leaks where the Headers/Y pipe mate up. I was getting Horrendous gas mileage with my cam only setup...and couldn't figure out why. (BTW...my setup is: 6 speed, TR230 cam, Jet Hots and True duals, stock 3.42 gears). In mostly hwy driving conditions I was getting 13 mpg. To compare, my SS (Full heads/cam, Strange 12 bolt w/ 4.10's) would get 18 mpg in the same conditions (and 25 mpg on long distance Interstate driving). I couldn't believe that the 230 cam would be that inefficient...so I began to look for stuff....with the help of Autotap it didn't take long.
While on the Throttle my Ltrims were in the 0.0 - 2% range. However when I would accelerate and then let off, my Ltrims would literally spike off the chart to +25% (w/ +25 being the max that Atap will read). I knew right then I had a leak near my 02's. As soon as I fixed the leak, voila' gas mileage in the 17-18 mpg range again.
I couldn't believe such a small factor could crush my mileage that badly.
While on the Throttle my Ltrims were in the 0.0 - 2% range. However when I would accelerate and then let off, my Ltrims would literally spike off the chart to +25% (w/ +25 being the max that Atap will read). I knew right then I had a leak near my 02's. As soon as I fixed the leak, voila' gas mileage in the 17-18 mpg range again.
I couldn't believe such a small factor could crush my mileage that badly.
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