14 mpg guzzler

mdrburchette · Post by **mdrburchette** » Fri Oct 27, 2006 6:21 am

I tried a higher octane in my fuel injected Bonneville, thinking it would clean the engine and improve performance. It had less power and got worse fuel mileage! My technician explained that higher octane fuel burned more slowly and could be dumping unburned fuel into the cat. My Fiat owners manual says to use 91 octane or higher so that's what I use, but newer cars with fuel injection usually require a less octane fuel to burn efficiently. Unless I was getting a predetonation ping, I'd use the recommended octane and not waste my money.

So Cal Mark · Post by **So Cal Mark** » Fri Oct 27, 2006 9:41 am

best results are from the lowest octane fuel that the engine will run on without detonation

TulsaSpider · Post by **TulsaSpider** » Wed Jul 16, 2008 7:01 pm

Well I just measured mine to the best of my ability. I got 174.5 miles and it took 9 gallons to fill it back up, so that's about 19 MPG, in town I was a little dissapointed, but I guess it's not uncommon. Next time I am gonna find a station without ethanol and see what difference it makes.

Hvnfn · Post by **Hvnfn** » Thu Jul 17, 2008 6:39 pm

I own a '79 Spider and mine is pulling in ~18 mpg about the city.

So far I have put in a new carb, 1800 manifold, new exhaust system and I installed an 6AL ignition module kit... I am getting poor performance at the top end, I.E. poor power at the top end. I am considering replacing the vaccum valve at the dizzy... or just putting in a new distributor since I just put in the new ignition stuff...

So Cal Mark · Post by **So Cal Mark** » Thu Jul 17, 2008 10:47 pm

a non-functioning vacuum adv will cost you about 10% fuel economy. How is the new carb jetted? That 2L should have great top end performance

Hvnfn · Post by **Hvnfn** » Fri Jul 18, 2008 11:53 am

The carb is a DFEV sitting on an 1800 manifold. It is jetted with the stock jets... I thought that they would suffice...

The car idles great, granted I am not absolutely positive that I have the dizzy hooked up to the Ignition control correctly...
I took your advice and installed a 6A ignition control and new coil. It did make a difference, although I am not entirely positive I have the proper config to the dizzy...

What would you suggest for the main and air circuits? should I consider going larger on the air and main and smaller on the idle?

I would assume the idle jet is a 50... on the 2L, should I change this to a 45?

TulsaSpider · Post by **TulsaSpider** » Sun Jul 20, 2008 10:11 pm

On this subject I drove mine today and got it nice and hot. I popped open the air cleaner to check out the choke and with the car off it's completely closed. With the car idling it cracks open about MAYBE 1/2 inch. Is this normal or is it contributing to why, (as I think Mark mentioned about a closed choke), my gas mileage isn't what I had hoped for. I tried adjusting the tiny screw on the diaphram there but no change, which way to open it up?? or is there a new diaphram needed or are they available? I was going to wire it open for the summer but didn't really see an easy way...

So Cal Mark · Post by **So Cal Mark** » Sun Jul 20, 2008 11:10 pm

the choke should be wide open on a warm engine. The diaphragm only pulls the choke open initially so the engine can get enough air to run when first started. The most common problem is that the small nipples for the choke hoses get rusted shut so no water flows to the choke. Hence, my love of the dfev with the electric choke!
With a closed choke, you will get extremely poor mileage and lose tons of power

TulsaSpider · Post by **TulsaSpider** » Sun Jul 20, 2008 11:23 pm

Well sounds like that's a problem, any suggestions on the remedy?

So Cal Mark · Post by **So Cal Mark** » Mon Jul 21, 2008 12:00 am

it usually requires removing the heater tube to clean the nipple, the other nipple on the back of the intake manifold is sort of accessible. You gotta make sure you have good water flow thru the choke cover

TulsaSpider · Post by **TulsaSpider** » Mon Jul 21, 2008 12:14 am

Both hoses get hot I checked. So just take the choke housing off and clean? Will I need an new gasket there?
Thanks Mark!!!

So Cal Mark · Post by **So Cal Mark** » Mon Jul 21, 2008 9:56 am

both hoses getting hot is a plus! Does the choke housing get hot also?

TulsaSpider · Post by **TulsaSpider** » Mon Jul 21, 2008 6:53 pm

Yes it does.

So Cal Mark · Post by **So Cal Mark** » Mon Jul 21, 2008 8:53 pm

that's also good news. Now you need to take the choke housing off and see if the spring is secured and working

TulsaSpider · Post by **TulsaSpider** » Mon Jul 21, 2008 9:06 pm

Ok, is there more than one spring in there? The butterfly spring seems to work it travels easily when I open it with my finger, it just wants to close. I drove it till it got pretty hot today (full 190) and checked it it opened up a bit more but not close to fully open. It's a bit late to do anything tonight and I drive it to work, so if the spring is good then what? I don't wanna crack it open and then not know what to do.
Thanks!
Clark

14 mpg guzzler

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