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Home » Public Forums » GMCnet » Gas Mileage 500 Cadillac, 26' coach, 3.42 diffy (Response to Rob Mueller, US Aussie)
Gas Mileage 500 Cadillac, 26' coach, 3.42 diffy [message #242215] Mon, 03 March 2014 17:54 Go to previous message
cbryan   United States
Messages: 451
Registered: May 2012
Location: Ennis, Texas
Karma:
Senior Member
Rob,

Took the liberty of starting a new thread about gas mileage I get with my setup 500 Cadillac, EFI, multiport Accel.

I have a smorgasbord of answers:

1. Not sure because of leaks in lines top of tanks, can't fill it all the way.

2. Even if I could, I don't really "trust" that wondrous setup with the bouncing ball in the drivers side rear wheel well. Liquid gas gets into the line? Then what?

3. I think it is all right, smack in the middle of ERF's predictions. 8 - 10. Just think so, haven't been able to measure it. Having said that, it doesn't smell of gas, and starts quickly and seems dependable so far. I drive about 60 or 65 depending on conditions. It is strong, even with its problems.

4. It is premature to ask, as there is a suspected cam lobe that is flat. Or a cam lobe suspected flat. Or a bent pushrod.

5. As well, there are fuel tank anomalies. Pickups off the floor, nonop tank switching valve (cross connected, so when out of gas, you are out.)

6. It is premature to ask, as I have just discovered the extra squirts that can be programmed just before cranking, the cold start enrichment, that assured half a dozen lean false starts, now fixed, and the acceleration enrichment that has taken care of flat spots. Plan to "balance" the injectors using an IR gun.

7. It's premature to ask because due to KenH's experience and not having looked at all at exhaust temps at or nearing WOT, I want to make sure that the exhaust valves don't overheat, so I will have to look at that for sure, and in the meantime, I won't be putting my foot into it much at all.

8. It's premature and may always be because I will always have a hare brained idea to improve the mileage. This time because I want to investigate lean burn while I am at it.

So, Rob, you have asked something simple that has proven to be complicated for me to do.

With respect to the multiport setup, I think it is potentially a little better than the TBI systems in common use now. I hasten to add that the supposed superiority of the multiport system seems hard to substantiate, or actually there is negligible difference between the two. I think lots of tweaking might add a small amount of efficiency. New aluminum heads with a direct injection setup sounds like a winner by comparison. I have heard of none setup to do this.

Repair is a little iffy. Some of the ignition parts seem to be generic and easily sourced, but that computer box looks long in the tooth and hard to replace. Mercy.

I am as anxious to hear about your setup in your Aussie Coach that will have the 500 rebuilt and all the goodies you plan. You might get a little better mileage with your switch pitch in economy mode with the lower stall speed.

Best,

Carey


Carey from Ennis, Texas 78 Royale, 500 Cadillac, Rance Baxter EFI.
 
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