Fuel economy before and after blower cam.

Hi guys i have a 2009 calais v wagon with a blown l98 i had it for about 4 years with a harrop 1900 blower and had a standard cam then decided to get the cam done fuel economy want from approx 13 to 14 L per 100 to about 15.5 to 16.5 L per 100km as expected ive had it in this form for about 4 years but i recently had a seized lifter and had to replace the cam as i am thinking of selling it sometime in the not to distant future i decided to return back to a standard l98 cam,car now drives slightly smoother and quieter but my fuel figures have bearly changed still averaging around 15 to 16 L Per 100,before cam got 500 km to a tank with blower cam got about 400 km now after going back to standard cam still getting about 400 to 450 km per tank car makes about the same power it did first time with a standard cam but fuel economy has gone back to what it once was any ideas why, not overly fussed just more curious.

Likely from the larger injectors.
The tune may need some work, better injector data or the computer may even think you're using more than you actually are if they're not scaled properly. Worth checking how many kms you're getting to a tank vs actual fuel put in.

Provided of course the driving style and route hasn't changed over time.

I've got an HTV1900 on an MY8.5 LS3. Put an LS9 blower cam in - total waste of time and money!! Picked up only 5rwkw at the very top but actually lost torque. :(

Fuel economy hardly changed but it did give me a slightly lumpier idle.

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Originally Posted by white lie

Likely from the larger injectors.
The tune may need some work, better injector data or the computer may even think you're using more than you actually are if they're not scaled properly. Worth checking how many kms you're getting to a tank vs actual fuel put in.

Provided of course the driving style and route hasn't changed over time.

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Absolutely - the OP may find it's even worse than he thinks as the earlier PCMs (mine MY8.5 included) can't cope with bigger injectors. I've found with mine, and his may be the same, that the fuel economy is out by about 25% i.e. the amount of fuel it takes to fill is 25% more than the trip computer thinks it's used. If my instantaneous fuel use says 8.0l/100km I'm actually using 10l/100km. If my ave fuel use says 12l/100km I'm actually using 15l/100km.

No easy fix, so live with it.

Hi guys thanks for the responses it seems as though the computer is reading fine as i am getting the same fuel economy when i fill the tank as the reading so must be as i suspected and white lie said it was the injectors i had a quick retune when i switched back to the standard cam so might need a closer look @ the tune and injectors.

Hi guys thought i would update this thread even though its 2 years old only did something about the issue recently,over a year ago a mate who has some tuning gear looked into my tune and noticed a few problems the main 1 being my long term fuel trims were turned off no big deal many tuners do this but the short term fuel trims were fluctuating nearly 27% mostly under light load so about a year ago i booked my car in at the same workshop that did the previous work just for its 70000 km service and asked if while it was there can they have a quick look at the tune as the fuel economy had not gone back to were it used to be with a stock l98 cam they told me that it would be a waste of time as they said that 1 of my cats was lose they thought it had turned around and was causing a restriction and said that they could get me some news ones for about $750 and also that i could do with some new plugs and quoted me $230 even though the plugs they previously put in my car were just tr 6 plugs less than $10 each to buy i told them just do the basic service and i would take care of the rest i had not noticed any difference with my car regarding the cats so i took it to m y exhaust guy well known here in perth he had a look told me cats and exhaust were almost like new no problem there,so i left things as they were until recently had time off work so booked my car in same workshop and asked to have a quick look @ the tune and told them of the fuel economy issue told them it did not bother me to much as they car doesnt do many ks hoping that they would see the fuel trims and make some changes to sort it out i did not mention that i had looked into the tune as the tuning has quite the ego and i think he would get the shits with me if he knew i had been snooping into his tune,so i picked up my not knowing what to expect and when went get my car they handed me a bill for $400 to retune their own tune not happy,only had i back 2 days and have had a chance to look into the tune but its better on fuel and my idol speed is back down to were it used to be so even sitting still in gear its nearly 1 L per 100k better,i told them that i didnt want a dyno sheet just good driveabilty but they gave me a dyno sheet any way and it shows that i have lost 20 rwhp no big deal but i have also lost over 100 nm of torque maybe its my own fault but i feel ripped off what do you guys think.

Hi guys need to correct an error i havent lost 100 nm of torque only just noticed 1 dyno is in nm and the other is ftlb sorry for the incorrect info.

If they put the car on the dyno, they're going to charge you for dyno time...print out or not. $400 is probably a little excessive but depends how long they spent on it. Hopefully they didn't just lean the whole table out by a small percentage, run it up and send it on it's way.

Thanks for the response mate i do agree with you but that fact that they were cleaning up their own tune make the $400 hard to swallow, as when i went back to stock cam they charged me $200 for a touch up tune now they have charged me $400 to touch up their the touch up tune for the second time.

Jeezuz!!! Hope they supplied lube to ease the pain! :p

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Originally Posted by Wonky

Jeezuz!!! Hope they supplied lube to ease the pain! :p

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Sounds like they used "Deep Heat" :lol: