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post #1 of (permalink) Old 09-16-2000, 04:20 PM
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TR ignition upgrade - mileage loss

I recently did the tfi upgrade to my 4.2, and like the difference in smoothness. It already ran great with all the mods that it has-Holley 390, Clifford intake, 264 cam, header and reworked distributor. It always started fast, so that doesn't seem any better, but it does pull to 4000 rpm very smoothly, and I do feel a little more power, but I've gone from 13 mpg down to 11.5! I gapped the plugs at .040, but that's the only change. If I can't figure this one out, I'm going back to the stock ignition. I can handle bad mileage, but that's down-right terrible. Any suggestions?

Thanks,
Darren

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post #2 of (permalink) Old 09-16-2000, 05:55 PM
 
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Re: TR ignition upgrade - mileage loss

Hey Big D, It may just be if you keep the foot out of the carb. and the RPMs down that your milage will come back.
But that is no fun!

Happy Trails
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post #3 of (permalink) Old 09-16-2000, 06:09 PM
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Re: TR ignition upgrade - mileage loss

I guess I should have stated that I was very easy on the gas during the mileage test. It is more fun now though to put my foot in it.

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post #4 of (permalink) Old 09-16-2000, 06:27 PM
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Re: TR ignition upgrade - mileage loss

Did you change the timing? (Usually around 15* initial, 35* total mechanical by 3500rpms, 10* vacuum works well). Did the engine backfire at all since the upgrade? (Check/replace the Holley power valve).

Hope this helps!

post #5 of (permalink) Old 09-16-2000, 06:36 PM
 
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Re: TR ignition upgrade - mileage loss

Hey Big D, I was just kidding about your foot, but a better ignition should give you better performance overall. Hope you do find your problem.

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post #6 of (permalink) Old 09-17-2000, 12:06 AM
 
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Re: TR ignition upgrade - mileage loss

Let him change what ever he wants to.
It's not the ignition that is causing the milage loss unless he fiddled with the timing.

He said he made lots of changes, I just wonder how close together they all were....??

I wonder why everyone blames the ignition instead of tuning the vehicle?
It happens a lot.!!!

Best of luck to him, and let him change around what ever he wants to.
When he finally gets tired of blowing cash, and gets totally exhausted, then maybe he'll listen and get it tuned correctly.
Ignition has NOTHING to do with fuel delivery, and a hotter, cleaner spark couldn't do anything but help MPG...
He would be the ONLY person to loose MPG's with the upgrade, if in fact it is the upgrade causing the MPG drop.... (I don't believe it is).

My guess is he listened to some hack at the local 'Speed Shop', and has much too big of power valve and jets in the carb, and not nearly enough timing....
Probably doesn't have the idle mixture set correctly either...
Or a vacuum leak somewhere....
Real common when milage suddenly drops...

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post #7 of (permalink) Old 09-17-2000, 02:11 AM
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Re: TR ignition upgrade - mileage loss

That Post by Team Rush is in incredibly poor taste! He said that it ran good with his mods before. I find it hard to believe that a person who could come up with a good upgrade like that can't READ. Oh well I guess it does not matter to me either way but I do know that after the bull I just read I will cross that upgrade off my list right now. I am shure that he would have just liked some advice from the person who sold him a package of "stuff" for a profit, not to be called stupid. I also like how T.R. says that it happens alot. Hmmmmm
John

88 XJ ltd some mods. 92 XJ quite a few mods. 98 TJ dad's & mine joint toy stock more or less . & now a beater 79 CJ7 soon to be a non beater I hope
post #8 of (permalink) Old 09-17-2000, 02:47 AM
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Re: TR ignition upgrade - mileage loss

WAIT! EVERYBODY, please keep all the negativity to yourselves....I know it can be hard not to think something and also not type it, be geez....lets be a little more CIVIL!!! You all nee to take out your aggression on the damn JEEPTHEIVES that have been looting and pillaging our beloved JEEPS!!!

BIG-D, try messaging Alec78CJ or FlMudCJ, I know they both have the upgrade, and it took a little work to get Alec's running right, it turned out to be the carb i think!

mikey

If you cant DODGE it, JEEP it!
post #9 of (permalink) Old 09-17-2000, 07:19 AM
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Re: TR ignition upgrade - mileage loss

Before you do anything radical, like removing your upgrades, I would double check your dist. curves. I think that the key phrase here is the re-worked dist. Other than obvious carb problems, like the notorious Holly power valve leaking, most fuel econemy problems are related to the vacuum advance curve. Did you check the obvious fisrt? Is the dist. vacuum advance hooked up? Is it on a good ported signal? Does the advance even work? Some diagnostic time may be in order. Get a good timing light with a delay unit, and a vacuum guage and run some tests. CJ-8/5.2 MAG gave some good specs for timing.

Remember, when tuning an engine, you must do things in the proper sequence. First, is the engine even tunable? Mechanical condition of the engine has to be correct, and there were some older posts on using a vacuum guage to help diagnose mechanical condition. Second, the ignition must be correct. That means cap, rotor, wires, plugs, and all of the timing curves. The last step is the fuel system.

From the sound of your post, was the TR upgrade done the same time as the re-curve? I seriously doubt that improving your secondary output will cause a decrease in fuel econemy, but re-curveing the dist. will. Very few people know the proper way to do this, and most of the small improvements in drivability that are gained with a re-curve, are almost always associated with a loss in fuel econemy. Hope this helps, good luck!

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post #10 of (permalink) Old 09-17-2000, 09:00 AM
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Re: TR ignition upgrade - mileage loss

Thanks to those who responded positively to my post. I will hopefully start digging further into it today. I think it's a great upgrade, and I guess I should not have said I was ready to toss it. I guess I was just frustrated, because to me at least, it "seemed" to be running great before the upgrade. I've been running it for a year with the mods listed with no problems. I guess that when I bought the jeep I should have asked just what was done when the distributor was reworked. That could be the problem, as the carb "at least to me" seems to be fine. Hopefully I'll figure it out. Thanks again for your help.

Darren

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