255 LPH+SCT tuner from Lonnie=poor gas mileage

WIP95MRK8

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Okay, so I know that with the tune I was expecting to drive a little bit heavier on the foot. But I ran a tank of gas with primarily all highway miles using cruise control and only got 240 gallons out of the tank. Could it be that the fuel pump is dumping too much fuel? I noticed it is REALLY wet on the muffler tip. How do I fix it? I justified the cost of the programmer to the wife with the mpg gains I was going to see, now I'm getting hell for it.
 
Okay, so I know that with the tune I was expecting to drive a little bit heavier on the foot. But I ran a tank of gas with primarily all highway miles using cruise control and only got 240 gallons out of the tank. Could it be that the fuel pump is dumping too much fuel? I noticed it is REALLY wet on the muffler tip. How do I fix it? I justified the cost of the programmer to the wife with the mpg gains I was going to see, now I'm getting hell for it.

Did you clear the computer memory by disconnecting the battery for 1/2 hour? After that is done, the car will still need some time to 'learn' its new components.
 
Are you saying that you get 15 MPG as an Average? You need to be sure that your plugs are in good shape, and that you have no other issues underlying. Call Lonnie !!
 
. Could it be that the fuel pump is dumping too much fuel?.

no, the mark 8 uses a "return fuel system" controlled by a fuel pressure regulator.
the regulator opens and closes and keeps the fuel rail at a specific pressure by varying the amount of fuel that is "returned to the tank".

Simply put.. you have increased the volume..but unless you increase the pressure via an adjustable regulator then you haven't "added more fuel" per say.

The presence of water in the exhaust is normal but also can indicate a rich condition.
The normal operation of the cats turn unburnt hydrocarbons<--gas into water vapor.

That water vapor depending on the amount could be normal, or could be a sign that it's running "pig rich".

your best advice would be to contact Lonnie and follow his steps to the letter.
This isn't the time to get information from message boards and use it to debate with the tuner.

you will get futher, faster by simply following what lonnie says.

Back to the fuel pump.. the reason the 255 is an upgrade is not because it puts out more fuel. the real benifit for most comes from the fact that the pumps output can degrade a WHOLE LOT before fuel delivery becomes and issue.

if you take a 190LPH pump and a 255LPH pump and they both lose 10% a year, it doesnt take a rocket scientist to figure out the 255 pump is gonna perform better over the long haul.
 
no, the mark 8 uses a "return fuel system" controlled by a fuel pressure regulator.
the regulator opens and closes and keeps the fuel rail at a specific pressure by varying the amount of fuel that is "returned to the tank".

Simply put.. you have increased the volume..but unless you increase the pressure via an adjustable regulator then you haven't "added more fuel" per say.

The presence of water in the exhaust is normal but also can indicate a rich condition.
The normal operation of the cats turn unburnt hydrocarbons<--gas into water vapor.

That water vapor depending on the amount could be normal, or could be a sign that it's running "pig rich".

your best advice would be to contact Lonnie and follow his steps to the letter.
This isn't the time to get information from message boards and use it to debate with the tuner.

you will get futher, faster by simply following what lonnie says.

Back to the fuel pump.. the reason the 255 is an upgrade is not because it puts out more fuel. the real benifit for most comes from the fact that the pumps output can degrade a WHOLE LOT before fuel delivery becomes and issue.

if you take a 190LPH pump and a 255LPH pump and they both lose 10% a year, it doesnt take a rocket scientist to figure out the 255 pump is gonna perform better over the long haul.

All these points are very valid. I will contact Lonnie tomorrow. Thanks for all the advise. I will update you to the end result.
 
So got a hold of Lonnir and didn't get the help I was looking for. I got the winter fuel blend could be part of the problem of my car. I'm not sure how going from averaging 22mpgs to 15mpgs with a tune could be a mechanical problem. I did unplug the battery for a half an hour so we will see what happens there.

Any more thoughts?

With the a/f ratio, how do I check it and what should it be?
 
I don't know anything about the tuner program you are using. I do know that other software they use on my vette, e.g.EFI live, gives a graph of the a/f ratio and to get while you drive around it at higher RPMs they install a wide band O2 sensor.
You can also get it on a dyno at a tuner shop and they can tell you the a/f ratio.
 
without saying that I "know" how lonnie does things, which I dont know exactly how he tunes cars, but I am very familar with the tuning process with these cars.

I spent along time tuning my own car and can say this.

there isn't ANY possible way that a performance tune will kill your gas mileage, unless it is the owners driving habits causing the MPG variance.

the stock mark 8 has a near 10/1 AF in the stock fuel table.
one of the first steps in getting a mark 8 dialed in is to remove this SUPER FAT fuel setting and replace it with a more performance orientated fuel setting like 12/1AF.

there isnt any way that "taking extra fuel out" is going to decrease your fuel economy.

what year car? im assuming a 95, based on your username.

id suggest running the car stock for two tankfuls, then putting the tune back on for two tank fulls, then compare mileage.
also..how are you caculating the mileage? using the message center? or doing the math on the next fill up?
 
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thought from the far side?

here in texas now that it has cooled off considerably, I now run outside in the morning and start the car so it's warm when we put my son in the car.

that has had a measureable effect on my mileage, on the order of 5MPG per tankfull
 
It would be easy enough to compare the stock mileage and the tune mileage by switching tunes.
 
Does the ECM need some time to optimize and adjust for the different tune?

I'm not so sure. I don't know if the flash rewrites everything or just portions of the programming. The 'modifiers' could be zeroed out by a battery disconnect. That would be the preferred approach I guess.
 
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