How much fuel enrichment???

I might add some nitrous to the trusty old 501 this winter.... I run in on E85 which of course requires bigger jets (bigger carb in general) then race gas...but it's about 1/3 the price of race gas which is why I use it... The engine will be going back in the Comet (2600 lbs.) and will continue it's part time life on the track and on the street...

Question is when (and if) I add a shot of nitrous to it, how much bigger should I jet the fuel side of the nitrous injectors? Carb is an 850, jetted at 78 and 83.... I would think that using E85 instead of gas I might be needing a bigger shot of E85 when using the nitrous because of the lower efficiency of the fuel????? Or am I just creating a problem where there isn't one????

Dave I'm first to admit I haven't played with nitrous that much but if the carb is already jetted for the E85, I would think that might be fine as you would add (inject) the extra fuel along with the gas. As far as the jet size for the fuel injector I think I would get ahold of the tech line for the manufacture and see what they say for the E85.

Remember it's better to start fat and adjust leaner than to start to lean and melt a set of pistons.


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are you gunna run a plate type under the carb ? if so the manufacturer should have one set up with the correct spray bar for E85 and the horsepower you want to add ..i loved it on my 429 with automatic .. blew up a winsdor with it though .. missed a gear ... 5 speed ..

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Originally Posted by HOSS429

are you gunna run a plate type under the carb ? if so the manufacturer should have one set up with the correct spray bar for E85 and the horsepower you want to add ..i loved it on my 429 with automatic .. blew up a winsdor with it though .. missed a gear ... 5 speed ..

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I probably called the people too late yesterday, the guy I talked to was obviously just a phone bank guy--wasn't real sure he even knew what E85 is!!!:LOL::LOL::LOL: Have to try again next week someday! Yes, it will be a spray bar system.

I'm with Mike I don't think you'd have to rejet if its running now. The extra fuel should come in the bar

Ok, maybe I didn't state things right,,,, my concern is the fuel jet for the nitrous kit, not the carb jets. Just wondering if I should use a fatter fuel jet on the nitrous system because of E-85 instead of gas.....

I would think so in that case but have no idea how much bigger you'd go. Hopefully that phone call will let you know

A gallon of E85 has ~72% of the energy that's in a gallon of gasoline, or stated another way, it takes 1.5 gallons of E85 to equal the energy in a gallon of gasoline. With that thinking it would seem to me that the jet for the fuel bar would be in the range of 1.5 times the orifice area that's called for on pure gasoline to match the "HP Shot" of NOx that you're using. That said, it will be interesting to see what the NOx guys say about E85. With the added timing that you run with E85 I would think that the whole energy equation would be different.

Should be able to work off that 72% figure for the fuel side of the nitrous, huh?? Suggests that the fuel jet would be 1.25 to 1.5 times larger for E85 vs. gasoline??? I've got an MSD timing retard module, so pulling timing out with the RPM rise shouldn't be a problem. I should be able to find a tech guy at one of the nitrous companies that has some experience with it!

Thanks guys, gotta keep the old mind working!!!

An air/fuel ratio system would seem to be necessary to me. If nobody could tell me definitively, I'd start pig rich at 140% of the gasoline jet area (.7854 x bore x bore) and lean down until I got the right mix according to the A/F gauge. Correct A/F ratio for E85 is 9.8:1
Aem Electronics 30 5143 E85 Wideband Air Fuel Gauge 5 7 to 11 9 afr Analog | eBay

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Originally Posted by techinspector1

An air/fuel ratio system would seem to be necessary to me. If nobody could tell me definitively, I'd start pig rich at 140% of the gasoline jet area (.7854 x bore x bore) and lean down until I got the right mix according to the A/F gauge. Correct A/F ratio for E85 is 9.8:1

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I'd say that you're spot on target, Richard. Most of the kids running nitrous just believe the jet to spray ratio that comes with the kit, which I expect is biased rich to limit what little liability the kit guy might have. Seems to me an A/F meter would be a necessary accessory to get the hardware dialed in right.

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Originally Posted by techinspector1

An air/fuel ratio system would seem to be necessary to me. If nobody could tell me definitively, I'd start pig rich at 140% of the gasoline jet area (.7854 x bore x bore) and lean down until I got the right mix according to the A/F gauge. Correct A/F ratio for E85 is 9.8:1
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I've got a good Air Fuel monitor, we learned a long while back that it's about the only way to tune with E85, plug reading is about the same as plug reading a methanol engine! Takes too long to get any color on them! Works with the data logger too which is good when you're a bit busy with other things!!!! I run a bit fatter then the suggested 9.8:1 just to cover an occasional leanout.

You're absolutely correct on the AF monitor, cost me the tops of 4 pistons to learn that little lesson!!!!!:o:o:o IMO it's one of the two essential items when running E85 (or 90), second thing being a fuel hydrometer that works with ethanol!!!!

Thanks for the input guys!!!!