I recently upgraded to the LS6 intake and performed the LS6 valley tray conversion. I've noticed that the mileage has gone down quite a bit. The first week I started looking at it, I got 12.8 MPG. But, that was a week of getting on the gas a lot. So, I tried to be really conservative on the following tank full. I didn't get into it too much, drove in 6th most of the time driving to work and I still only got 15.52 MPG the last tank full.

Could the LS6 intake be responsible for more fuel being consumed? I wouldn't think so, but I haven't done anything else. Well, I did remove the EGR and had the code removed from the computer (thank you, MTI!). I haven't noticed any fuel smells, either.

Any thoughts?

 

I'm shooting to hit 8mpg by mid summer next year

 

Hi Folks
I doubt that very much that LS6 intake could drop your gas mileage. Remember they put them on 02 LS1 engines and they get high 20's stock. What you did is just add the intake - there is something else wrong here.
Bill

 

Is that up or down!!

 

Where would you suggest looking?

 

Built 370 with a blower and i see 13mpg in the city if i dont play and 16.5mpg on the freeway with a A4 and 3.73's spinning 2500rpm's @ 70 mph....... Under 10mpg this tank..... playing some..... 1/8 tank left with 115 miles so far...... 13.5 gallons to fill me up.... 98 tank...... dirty fuel filter..... whens the last time you changed it???? clogged injector???
Kyle

 

That's quite low MPG. You must stay on the loud pedal too much! After I installed my heads I made a trip up to Rapid and nailed 27MPG with the AC on and a 10.8-1 AFR which is rich as hell. On the return trip after tuning I pulled 29.1 MPG after being tuned. This is crusing in 6th @ 75mph mostly. Did MTI do any tuning after the LS6 intake or just delete the EGR code? I highly doubt the loss of MPG is due to adding the intake.

 

That will be after the new fuel system and several other major mods

 

MTI didn't indicate that they did any thing else other than delete the EGR, but who knows. Jayson was out and someone else did the job. Perhaps I'll stop by this weekend and inquire. Car runs great, but at these gas prices I'm not too happy. Even with my measely 5 cent discount from ChevronTexaco (I'm an employee)!

 

check what kyle stated... and your car might be running really fat in the midrange or low end from 1500 to 4500, where a lot of your acceleration and cruise rpm's are at. If it is fat in that area, you use that the most, and you would be wasting the most amount of fuel..

most 6 spd heads/cam cars are still making 20 some mpg's i know Tony personallh has netted a few 31 mpg tanks in his SS.

Just check the injectors, fuel filter, tune, anything fuel related... or just examine your right foot again

 

Removing egr can cause your gas mileage to drop, it's not just an emissions thing. Your gas mileage is really low for 6th gear cruising though so you probably have another problem, bad o2 sensors maybe?

 

Hi
Looking at the other posting and noticing you have de-screened the MAF. The De-screened MAF change how your car runs - when I was tuning my car, I was told to go back to the Stock unit and have not put the other unit back in. I believe that would effect your gas mileage. If you can, I would put back the stock unit. Also the 02 LS6 intake does not have an EGR - so I don't believe that is an issue.
Bill

 

I appreciate the responses. I did have a new fuel filter put in last summer, maybe it's time for a new one. The injectors are the factory ones and I have 78,000 miles on the car now. Could they be bad? Wouldn't I be getting a code for the lean/rich condition? Also, the o2 sensors are fairly new and the catalytic converters are brand new (thank you GM warranty!). The screen has been out since 2001. I have observed a high of 29.5 MPH on a drive to Fort Worth and up north for Chryslers at Carlisle and got 27 MPH. So, it's certainly a recent change.

The car idles fine, so I don't think I have any vacuum leaks after the LS6 intake installation.

As far as observing the fuel usage between 1500-4500, how and were can this be done? Is tuning the answer??

Once again, thanks to all.

 

Could the increased air intake cause the PCM to alter the fuel map, thus decreasing the fuel efficiency? I would bet a good tune would bring the efficiency back to it's original range. When Rapid Motorsports did the ARE H/C and other mods(see sig)...the gas mileage was quite a bit lower for the first couple months(about 500 miles) but after the break-in was complete the mileage went back up. Even with the added weight of the SFC and 12 bolt, AND the gear swap to 4.10s (from OEM 3.42s) the MPG didn't seem to change much...That's until I jump on the throttle!

 

I am having the same problem. My MPG is about 15 city/highway. I am pretty sure it is tuning. Tuning makes a big difference in MPG.

 

I'm actually talking to MTI as I write this. They said that tuning shouldn't make any difference in the mileage. I'm not 100% sold. I would think that a bad tune (ie: running super rich) would effect the fuel economy.

Anyone have any further thoughts?

 

Closed loop automatically puts you at 14.7 to 1 at part throttle using the fuel trims. The only reason it wouldn't is if your o2's are bad, o2 extensions are bad, you have an exhaust leak so your o2's are reading wrong, you have a bad injector, or your fuel trims are maxing out, but then you would set a code. So MTI is right, a tune will not help for cruise gas mileage unless your fuel trims are maxed out which is unlikely.

Using a logging tool could definately help you diagnose if you have another problem though.

 

Would that be something like AutoTap? I've never used, don't know where to get.

 

How are you measuring your MPG? I have noticed that after a tune my "computer" is no longer accurate. It claims I am getting 23MPG but doing the simple math of miles/gallons I see it is more like 18.5MPG. Before I got that car tuned the computer was damn close. SOOOooooo if your not actually calculating it yourself and relying on the computer you may be .

I don't understand how you guys get these crazy 28-29MPG numbers either. Must be in the midwest or somewhere with 0 hills. Here in New England I have done numerous attempts at maximum MPG on the highway and NEVER see more than 23MPG. That is REALLY babying it.

--Bill

 

I think if your tune is far enough off it can dump extra fuel in....even though most of the time it would be right.