Fuel Mileage on 2.7 with MFI?

[A.T.]

Hey Folks

Any opinions on typical fuel mileage, highway and track, for a properly set up 2.7 liter mfi engine with 9.5:1 compression? I think mine is so far off the scale that I'd rather not say what I'm getting. I'm pretty sure I'm in need of some mfi set up.

Thanks

A.T.

[Chuck Miller]

Hey A.T.,

I think we we're running about the same deal... 2.7 MFI RS + spec 9.5

- I get no better EVER then about 18 for a whole tank in 5th under 4000
- I average about high 13's on the street
- And about 7 on the track

Hope this helps

[A.T.]

Hey Chuck

Thanks.

Okay. I'm getting about 8 and a bit on track but only 13 highway. When I try to stretch it on the highway and I finally step on it again it really smokes. Under the duck tail is always covered in schmutz. My mechanic buddy was following me to the track and said he could hardly stand the fumes and suggested it may be an mfi thermostat issue.

This could take some reading and poking around.

A.T.

[RSTarga]

I get about 13 around town but on the highway I've gotten 21. Steady state cruising at about 90. I've only got 8.5 so one would think an extra point would be a little better. I've never put it on the track so I can't give feedback there. If you had a thermostat issue you would definitely notice it.

[RSTarga]

Chuck, What gears are you running. I've got the standard gears for a US 73S, and the standard rear end. I think they are a bit shorter than what was on the factory RS. Aerodynamically I've got the front RS spoiler and the ducktail at the rear.

[Chuck Miller]

Dave,

I've got standard US 5 speed gearing and diff, with S front spoiler and RS ducktail......

However, I run 225x50's all around on 7's and 8's....
I have to calculate 5.2% less mileage when I do the math. And equally, I'm do'n more revs for a given speed.

Cheers

[gulf908]

AT,

The first thing you should check is the piping from the heat exchanger through the tinware and to the injection pump is complete and undamaged.
The hose from the exhaust to the tinware is fairly robust and the ribbed piping from the tinware to the injection pump is a lighter material and should be double wrap.
If this thermostat shutoff is not working correctly ,then you are just throwing gas/money out the tailpipe.
Make sure the basic tune of the motor is correct before looking at the MFI pump.
Does your mechanic have the check,measure,adjust manual ?
The MFI system is designed to use more gas than a carb setup but this varies depending on how close your accelerator foot is to the firewall !
The search button on this forum will help you.

HTH,
Dennis.

[orange911]

AT,

The first thing you should check is the piping from the heat exchanger through the tinware and to the injection pump is complete and undamaged.
The hose from the exhaust to the tinware is fairly robust and the ribbed piping from the tinware to the injection pump is a lighter material and should be double wrap.
If this thermostat shutoff is not working correctly ,then you are just throwing gas/money out the tailpipe.
Make sure the basic tune of the motor is correct before looking at the MFI pump.

This is really true when the engine is warming up, but after about 15 miles, the heat transfer to the thermostat should get it heated up enough, unless it is pretty cold out. Either way, you don't want to be pouring gas into the cylinders for that short of time and messing your lubrication up. Don't forget to make sure that it is clear on the exit side of the thermostat too. This draws the hot air up and out.

Olin

[sithot]

Buy a VW TDI.

A tune up is great idea but It's never going to be great. The 2.4 S did 14-17 (C&D observed) back in the day and was considered acceptable.

Tom

[A.T.]

Hey Guys

Thanks.

From Chuck it sounds like 8.4 mpg on the track is normal. My 13 mpg highway seems low. I was really nursing it too. If gears mean anything I think the tranny is set up for Watkins Glen and it's got a limited slip dif. Cruising conservatively on the highway around 70 mph and around 3000 rpm or less.

I had major work done on the engine in the spring. The whole top end, pistons, cylinders, work on the heads etc. My guy knows his way around the mfi. The whole thing was gone over (checked, measured, adjusted) and set up on the bench before the motor went back into the car. I spoke with him today. We're going to have a look at the thermostat set up. I'm going to do a quick visual of the hoses now.

If that doesn't work it's the VW TDI.

I'm probably a little paranoid but oil contamination is always in the back of mind.

Is the schmutz just going to be more of an issue because it has dual out style tail pipes? My '69S had a stock single out the side tail pipe. I'd still get some residue there too but not nearly as much as with this car.


A.T.