I`ve been running VP-100 and 101 unleaded fuels for 3+ years now and noticed the timing needs are slightly different from this compared to say 110 leaded and was curious for those w/a dyno or those that have dynoed different fuels how they differ on the egt`s. I would ASSume the unleaded burns hotter but not sure so what have you guys found.............Thankxxx

So no one has compared egt`s between unleaded and leaded or is it top secret................ Or does it not work that way........just trying to learn here.

Never played with unleaded race fuels or cared what pump gas swill did honestly. Then again we don't look at EGT numbers either just O2 data. IMO EGT info can be misleading at times. Only thing we use it for is to make sure a cylinder is firing. In a blown, alky or nitrous deal it is a more helpful barometer IMO.

Thankxx Al, I think I`m going to go back to mixing 110 leaded w/91 pump 50/50 for the cooling effects of leaded and my car ran real good that way in the past.

For years we use to use EGT for the balance of fuel.. but
now that A/F meters came about most think EGTs are nothin but
trash.. I still use them to balance intakes(runners).. and until
about 15 years ago that was also how some tuned the fuel...most
fuels are designed for 1280*-1300*... some will go higher.. but
you have to know what all the specs are on that fuel... if it doesnt
give the temp spec on the MSDS sheet call the company... and 2 companies
that make the same fuel wont be the same

You can find 100 unleaded in Vegas Dom. At some of the Rebel stations in town.

Higher octane is slower burning so it would want more timing. Generally speaking.

Thankxx guys...............Ya, I found 100 at the pump and in pails but figured it`s cheaper to mix 50/50 since 100 is about the same price last time I checked.

As said, not too many guys running individual thermocouples for EGT data anymore - for the reasons stated ( 02 info ). I run Sunoco 110 leaded pump race gas because 1. their use description fits my application. 2. It's less expensive than buying fuel at the track. 3. fuel at the track isn't always available. 4. Not much interested in lugging a 5 gal can of fuel around the pit area.
Sunoco 100 ( unleaded ) is also available at the same station where I get my 110 for the same price. From what I have seen, combustion chamber temps are pretty much in the range that Mr P stated. FWIW, looking at the specs of the 2 mentioned fuels, unleaded 100 has a BTU / gallon of 109200 while 110 leaded has a BTU/gallon of 113400. Sooo, it appears that 110 leaded puts out more heat than 100 unleaded ( which also BTW, contains 9.8% ethanol ). Conclusion = I have no idea? For sure, a change in fuels would warrant a change in timing. As you said Dom, dyno info.

I have been retailing race fuel for like 25 years, sell Sunoco.

Have never seen any kind of spec sheet that show what the EGTs should be.

I don't recommend blending fuels because it can affect consistency, maybe that is not concern of yours? Plus its a major hassle. For a street car, I guess no big deal but sure would make it harder to tune.

We sold both Sunoco fuels too at the pump, 110 leaded and 100 octane unleaded...with a ton of ethanol in it. Like said. I don't know about you, but I would not want ethanol in my performance gas.

We did not sell much 100 octane unleaded, we sell tons of 110 leaded out of the pump plus we stock many other grades in 54 gallon drums.

This past spring I took out the 100 octane unleaded and started selling 91 octane straight unleaded with no ethanol. This would be the gas to blend, with no ethanol. We have many street customers do just that. Buy a little of both and put it right into there muscle car at the pump.

We have sold way more of that gas so far this year than we did 100 octane all last year, like 4 times as much so far. It's popular for small engines and classic cars. It stores well and will last for years, try that with 100 octane with tons of ethanol in it.

And yup 110 leaded has more btus than unleaded so it will make more power(heat) than unleaded just because of the BTUs. I don't think it would change how hot your car runs, that's done by richer or leaner. You could easier make the "hotter" fuel burn cooler just by adding more fuel to the engine.

Great info thankxxx guys. I don`t like straight 91 and neither does my car fully wooded by the "peppering" I saw even w/a fairly cold #8 NGK so just wanted a safety margin plus I have a street race here in the near future so maybe I`ll just stick to what I`ve been running which is VP-100 and go from there...............

An EGT number is just a number. As Al said, it basically tells you if a cylinder is running and not much else. The design of the header can have as much to do with EGT numbers as anything. They are more reliable in zoomies than regular headers for obvious reasons. BENDS effect things, numbers included

At Chrysler we FINALLY set a standard of 1" off the head surface
for ALL exhaust reading(EGT).. before for that guys were putting
the probes in where ever they liked... and when I say 1".. thats
measured within .005.. thats why the 1".. its easy to get that
point.... over the years since O2s came around I used to set max
power based on the O2 then check with the EGTs on all the cyls
just to see what the numbers were in relationship to what the fuel
companies called out for max temps... its very close... yes guys
now days wouldnt ever think about EGT... but the top fuelers and
all those guys still use them

Who makes a good inexpensive O2 sensor.??



Chris..

I went with "Inovate" from Summit # SUM-G2995. Lots of options with it - data logging, Etc,

I have my O2 meter loaned out right now or I could tell
you what I have for a replacement... its been doing good
for 6-8 months so for

Now I`m really confused. You say we don`t want ethanol in or "race gas" but doesn`t the E in E-85 stand for ethanol? The biggest plus I hear about from people on E-85 is how "cheap" it is and that it runs a bit cooler but I have zero desire to change over at this point and will figure something out.............

I called the airport to see about some 100ll but they don`t sell to the public............bummer as I`ve heard good things about it from MOST people..............

Think his main concerns were blending ( non ethanol with ethanol - could run in to compatible issues ), Longivity / storage, and a fuel system that may not be "totally" compatible. Not to mention adding another variable ( blending ) to the mix - so to speak. Since the $ is the same for the 2 fuels I mentioned ( Sunoco 100 With E and Sunoco 110 leaded ), no brainer choice for me. Running av gas opens up a whole nuther can of worms, starting with reeds vapor pressure issues, etc. I wouldn't run it and I wouldn't blend with it. BTW, think most AF meters are calibrated using gas with 0 ethanol in it, so when you blend, exactly what are you using for a conversion chart???

Thankxx 4 the info. I see what you mean about blending but had zero issues blending 110 Rocket leaded w/91 Cally swill and plugs looked good and car ran great and was told ON HERE that it was fine. When I meet up w/the two machine shop owners next week I`ll see if they sell gas, what they have(if)and go from there. I drive my dart more now them I have in a long time and $$ does play a role but a happy motor is my major concern in case I have to educate someone on a side road late at night.

I'm not an ethanol fan, but if your blend has been working, stick with it. IMO, you want to run just enough of an octane # so you don't have to compromise timing to stay out of detonation. I probably play it a little on the safe side, but 21 lbs of boost in the lights equates to a pretty scary static CR, so I run 110 - and some windshield solvent.