I am curious about mileage and what you are getting out of your 4.9. I am running a 5 speed Getrag and can't get above 18 mpg even taking it easy using 5th and lugging it. So what are you getting and what type (octane) gas are you running? I may need Rockcrawl to check if the chip is burnt correctly.
Thanks

Earl

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1986 FieroGT now a 4.9

I was getting nearly 30 on the highway but have not reset the ECM yet since I did the clutch so I am getting around 12 in town and low 20's on the highway.

I think when I had it running perfect it was 20 something in town and 30 something on the highway with the Isuzu

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85GT 5spd MSD Everything,4.9 With Nitrous. www.captfiero.com

I'm usually in the 26-27 mpg range on the road. Have gotten 29 in the mountains one trip. 4.9 , T460e with Transgo shift kit , Rockcrawl chip.

I just got back from Fierorama with mine. My gas mileage around town the week before was 14mpg and that was all hard driving. On the way to Fierorama I got 21mpg. We were stuck in a traffic jam for about an hour around Chicago. Stop and go. I'm at 145 miles since I filled up and I still have a half tank. I'll know what the mileage was when I go fill up tomorrow.

Oh, and mine is a 4.9 from a 91 DeVille. Rockcrawl chip. Ported heads and allante intake. Larger Delta camshaft. custom 2.5" exhaust and an Isuzu transmission.

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[This message has been edited by FieroMaster88 (edited 09-11-2005).]

Lets see, we use to fill the tank and drive to the drag strip that was 15 miles away, do 20 or more 1/4 mile runs and bring it home empty . But that was a 4.9 turbo. and I thought it was great fuel milage. Anyways, our 4.9 turbo was better on gas then the 2.8 was, We use to get 180 kms to at tank of gas on the 2.8, with the 4.9 turbo we could get about 230 kms. But then we did not put in a 4.9 V8 for fuel economy.

Pete

I am running a 4 speed and Rockcrawl 's chip. I just got 22 MPG going to and from Fierorama and I only use 87 octane. I tried to use 92 octane for a couple tank fulls a while back, but my gas milage dropped off so I went back to 87. In town I get around 18 MPG.

Jack

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If you can not run with the big dogs, stay on the porch!

I thought with the fuel and timing map of the performance chip you had to run 92/94 oct gas.

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85GT 5spd MSD Everything,4.9 With Nitrous. www.captfiero.com

I'm getting 19.7 mpg with 4.10 4sp tranny & Rockcrawl's chip.

In the Finale, with a 4T60E and relatively stock 4.9, I normally get about 28-29 highway but if I actually drive at or below the speed limit I've gotten 32 on Interstate. General, all around mix of city/highway driving I get about 25 or so, depending on HOW I drive it. I normally run about 210 miles on a tank of gas before I fill, but it's not real empty at that point and I take about 8 gallons to fill up (I just don't like to walk ).

John Stricker

I had the GT go through PA inspection with emmishions today and this is what was found. A 86 needs what is called a 2 speed idle test and at idle the HC was 900-948 which is unburnt gas and very high. The engine has a reground cam so this might be the reason for the high HC. At a rpm of about 1600 the reading is HC 45, CO .03, and O2 200 this is all raw data. Theese are good but the idle test would not pass in PA. I didn't need to get these done because my car was driven less than 5000 miles so it gets an exempt emmission sticker but if I drive more than the 5000 miles in a year I will have to pass the idle test. Do you think this is why I am running rich and getting less mileage than almost everyone else? My one ton van did the same trip to Philadelphia it has a Dodge 360 engine and got 16.5 miles per gallon today and I can only get 18 out of the GT which is much lighter.

Earl

My first thoughts would be what modifications have you done to the engine? You already mentioned a reground cam. Did you change the fuel mapping? What transmission are you running? (sorry, I don't remember) Does the car smell and seem rich to you? What rpm are you turning on the highway? I turn about 1900 rpm at 70 mph in the Finale, if you are running a faster engine speed than that it's going to really hurt your mileage. One of the big reasons these engines do well on fuel is that at cruising speed they are just loafing and have a lot of torque down there to keep the car moving easily.

John Stricker

quote Originally posted by aqua-man: I had the GT go through PA inspection with emmishions today and this is what was found. A 86 needs what is called a 2 speed idle test and at idle the HC was 900-948 which is unburnt gas and very high. The engine has a reground cam so this might be the reason for the high HC. At a rpm of about 1600 the reading is HC 45, CO .03, and O2 200 this is all raw data. Theese are good but the idle test would not pass in PA. I didn't need to get these done because my car was driven less than 5000 miles so it gets an exempt emmission sticker but if I drive more than the 5000 miles in a year I will have to pass the idle test. Do you think this is why I am running rich and getting less mileage than almost everyone else? My one ton van did the same trip to Philadelphia it has a Dodge 360 engine and got 16.5 miles per gallon today and I can only get 18 out of the GT which is much lighter. Earl

When I had the 2.8 in and with the Getrag 5 speed when my RPM's were at 2000 and I was in 5th my speed was 60 Mph. With the 4.9 in my RPM's at 60 are just under 3000. I have a reground cam, heads ported and the engine had new bearings done.

Earl

quote Originally posted by aqua-man: When I had the 2.8 in and with the Getrag 5 speed when my RPM's were at 2000 and I was in 5th my speed was 60 Mph. With the 4.9 in my RPM's at 60 are just under 3000. I have a reground cam, heads ported and the engine had new bearings done. Earl

Unless you have changed the transmission, the rpm at 60mph should remain the same.
If you are turning 3000+rpm at hwy sppeds, that is where your mileage is going.

My 4.9 4T60E with 2.73 final drive got 29mpg at 75mph. Now that I have shaved the heads and installed the large Delta cam, along with changing the final drive to 3.06, I get 25mpg at 75. This is running the stock chip. I have a Rockcrawl chip coming, but I do not think it will effect the hwy cruise mpg.

Around town is another story all together. I get around 10mpg, but I NEVER drive it easy. Every shift is a full throttle on the rev limiter shift.

Gene

Earl,

While your mileage is lower than I'd expect, the 3,000 rpm at 60 is really killing you. Did you correct your tach for the V8? The rpms should NOT have gone up due to the engine change, everything else being equal. If you didn't correct your tach then if it was showing 2000 at 60 before it should now be reading about 2,700 rpm or close to it at the same speed.

Did you leave fuel pressure alone (considering you Ported the heads and have the reground cam)? Stock injectors? If it were mine, and I was getting that mileage, I'd head for a chassis dyno, stick the wide band O2 up the pipe, and see what's going on.

John Stricker

quote Originally posted by aqua-man: When I had the 2.8 in and with the Getrag 5 speed when my RPM's were at 2000 and I was in 5th my speed was 60 Mph. With the 4.9 in my RPM's at 60 are just under 3000. I have a reground cam, heads ported and the engine had new bearings done. Earl

Rockcrawl did the 4.9 installation and set up with his chip. The tach and trans were to be set up by him along with any fuel settings needed. I wouldn't think that the RPM's on this engine with the speed should be about the same as my 2.8 set up but it's not. It's showing higher RPM's per MPG than the 2.8.

Earl

aqua man it sounds to me like the tach wasnt modified. Cause the trans Im running in my 4.9 has a 4th gear that is almost Identical to the getrag's 5th. I have not changed the tach yet and I am getting the same readings you are.

If your tires stayed the same and you kept the transmission, and the speedometer is correctly wired and calibrated both before and after, it won't matter if you're running a 600hp viper motor or a Briggs and Stratton, the rpms will be the same. That's simple mechanical gearing.

John Stricker

quote Originally posted by aqua-man: Rockcrawl did the 4.9 installation and set up with his chip. The tach and trans were to be set up by him along with any fuel settings needed. I wouldn't think that the RPM's on this engine with the speed should be about the same as my 2.8 set up but it's not. It's showing higher RPM's per MPG than the 2.8. Earl

quote Originally posted by aqua-man: Rockcrawl did the 4.9 installation and set up with his chip. The tach and trans were to be set up by him along with any fuel settings needed. I wouldn't think that the RPM's on this engine with the speed should be about the same as my 2.8 set up but it's not. It's showing higher RPM's per MPG than the 2.8. Earl

Make this simple. Please go to a shop have them hook up a scan tool and show you that your tach is wrong.

Then have a good day. Once you are ready to get your tach calibrated please come back and people will help you to set that up.

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85GT 5spd MSD Everything,4.9 With Nitrous. www.captfiero.com

I still have to calibrate my tach. Maybe I'll figure it out this week.

I am running at 22 mpg around town with a 91 Deville and a 5 speed Izusu (mostly easy driving - but that is hard to do always). At last check, I had 298 km on a tank of gas, not sure how much was left in the tank - maybe one day I will take some spare gas with me and see how far it goes

Tim