Projection mileage

[Narnian]

I have returned from my voyage to the northeast, and I hafta say, my mileage still stinks! I know there were a few folks who wanted a mileage report before and after projection so here it is.

Mileage when I first got the Jeep this summer was @ 14.0 mpg. That was with the Edelbrock carb, no emissions, no cat. I up until the end of the year I normally drove 250 to 450 miles a week in the Jeep, half city, half highway.

After I slapped the cat on to satisfy Ohio, my mileage dropped to 12.0 mpg.

There was a period of about a month between losing my main pulley and installing the pro-jection kit. The weather turned cold, and I had a few things hooked up poorly. My initial mileage with the projection was 8.5 mpg. This included the wasted fuel while tuning the projection at idle.

Before I went to the east coast I went to my buddies house and we checked the timing. It was at 4btdc instead of 8, and we fixed it. I felt I had everything hooked up right, and this little change would adjust any mileage issues.

After totaling my trip mileage (1554), I averaged out to @ 10.5 mpg. I am sure that the cold weather affected the mileage some, but I can't see it making that much of a difference. I am guessing at one of two culprits:
A) I still don't have the projection properly tuned. (very possible)
B) The cat is REALLY clogged because there is no other emissions equipment on board, and needs to be "opened" up.

Any suggestions?

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360 w/Holley Fuel Injection, Edelbrock manifold, NP219, 3.31, 33's, no fuzzy dice (yet)
AND an 86 Corvette & 87 GMC Jimmy (Jimmy soon to be for sale)

[mhoffor]

Your lucky, I get 8 no matter when or where I drive, a new moter is in the works.

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Mike Hoff
74 J10
360 Edelbrock Carb
TH400 w/shift kit
Headman Headers 3" pipes w/flomasters
Spring over front 8" net lift
Shackel flip w/2 1/2 steel blocks rear 7" net lift

[JeepFreak]

Depending on your gas you can bump that timing some more. I run around 12 to 13 deg BTDC with no pinging. However the best I can do in the summer is 11 deg. I got quite a bit more power when I first added some advance and mileage was better when I kept my foot out of it. Cold weather will effect mileage but that sounds a little extreme. If I was getting 14 MPG I would have never takin off the carb...Man thats some great mileage. All three of mine average around 10 to 12.

I might add that my motor is supposed to be timed at 5 DBTDC(it's from my 75 Wag) but it now is in my 85 Wag so with its ignition I have never been able to run 5. It has always ran best at 10 or better. Most stock ignition timing can be advanced some though with good results.

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JeepFreak

[This message has been edited by JeepFreak (edited January 08, 2001).]

[Michael F]

I am with JeepFreak, I have my timing set as far as I can get before it will ping and use 87 octane fuel (with no alcohol!), I tried out my 81 to see what it gets on the highway and ran it at 70mph for 45 miles carrying the family and groceries, filled up, and went OUT and BACK to the same place, and filled up again, 2.8 gallons and spilled some down the side of the jeep! I got 16MPG! NO I do not quite believe it myself and I am going to retest, but it sure did it!

I am going to try and install a GM TBI on it and have some of the parts already to do it, and need to know what fuel pump you all have used inplace of the Holley pump when the Holley pump did not work.

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81 Cherokee Laredo WT
54,000 orig. miles
360/727/208/3.31w/tracklock/31x10.5AT
79 Cherokee Chief WT (snow plow)
360/400/QTw/LR/3.54/31x10.5
My family has 7 FSJs!!!

[Narnian]

Hey Michael, about where did your timing end up at when you got 16mpg?

I would have left the carb on, except it dropped to the 12/12.5 mpg when I put that cat on, and low end performance was terrible.

I have not had any problems with the Holley fuel pump, but someone told me they liked the carter better.

[TPIGUY]

Michael,

Are you going to get a new chip for your GM TBI? The factory chip from a GM 5.7L engine won't work well.

Narnian, I get 15 MPG at 70 MPH in my '85 Grand Wagoneer (AMC 360/NP 229)with my GM TBI kit. What you may need is an air/fuel ratio meter to watch as you drive so you can see where your mixture is. It has green, yellow, and red LEDs where RED is rich, yellow is lean, and green is lean. You hook it up in parallel with the Holley ECM and then have a passenger watch. You can tell a trend after a while.

[Michael F]

Narnian, I have a 2.5" monolithic stock type aftermarket cat, 2.5" high flow muffler, and 2.5" stock exhaust. It could be quieter, but it is not that bad.

I used a timing light to set it but do not remember what I ended up with, my jeep has a new timing chain so the advance I have come up with may not work on your's, you just need to use the light to know your beginning and just move it a couple of deg at a time until you have pinging and back it off, and make sure your vacuum advance is hooked to ported vacuum like it is supposed to be.

TPIGUY, I was going to talk to you to see how much you wanted for the chip for a 1227747ECM, I have not been able to find theturboshop and it would be cheaper to get your chip until I get this all figured out, it is my only stumbling block I know of at this time, the other problems I will get figured out eventualy, or it will burn!

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81 Cherokee Laredo WT
54,000 orig. miles
360/727/208/3.31w/tracklock/31x10.5AT
79 Cherokee Chief WT (snow plow)
360/400/QTw/LR/3.54/31x10.5
My family has 7 FSJs!!!

[This message has been edited by Michael F (edited January 08, 2001).]

[JeepFreak]

The best way to time like Mike is talking about is to make your timing change and put it in gear and power brake it. If it's gonna ping it will then. Make sure you have good motor mounts before doing this though. My Dad and Grandfather were both mechanics and they never used timing lights. They did everything by ear. Now with todays new cars thats impossible to do but it was one of the ways I was taught.

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JeepFreak

[Michael F]

<BLOCKQUOTE>quote:</font><HR>Originally posted by JeepFreak:
The best way to time like Mike is talking about is to make your timing change and put it in gear and power brake it. If it's gonna ping it will then.

<HR></BLOCKQUOTE>

Sorry, I forgot to mention that little tidbit, I usualy do not use a light either but was having some problems at that time getting it to run like I am used to things running!