Ok i took all my octane test and used the good ole racing calulator to get the differant hp increaes to the wheels from the ET GAINS WITH THE HIGHER OCTANE. Most of the gas mix was 50/50. The 91 octane dyno tune was never touched during the test. Race wt was always 5190 lbs. TO THE WHEELS HP.....GAS USED 91.00 - 368.00...........MOBIL 91 WAS USED IN ALL TEST 93.00 - 379.74...........SUNOCO 104 & 91 95.50 - 381.31...........VP 100 & 91 96.50 - 383.88...........SUNOCO 100 & 91 98.00 - 390.12...........VP 109 (105 OCTANE) & 91 101.5 - 379.33...........SUNOCO 104 & 100 & 91 My price for the gas mix. All gas mixes were 9.5 gal 91.00 - 3.36 gal 93.00 - 7.06 gal 95.50 - 5.80 gal 96.50 - 6.19 gal 98.00 - 8.88 gal best buy for the gains +22.12 hp & dropped ET.195 101.5 - 8.12 gal As you can see useing higher octane gas is the cheapest mod you can buy. Now you can go faster if you datalog and add timing & fuel to take advantage of the octane. I hope this may help some of you and go try it.
Heres the best times run in the 1/8 mile on each octane. Every test had 4 runs and each test was done a month apart. I did avg all the runs in each test and there even better than just listing the fastest runs. The gains on the avg runs are listed from the least to best. - 0.10,0.12,0.13,0.19 over the 91 octane avg. These are not listed in the order below. TO THE WHEELS HP.....GAS USED....................................TIMES 91.00 - 368.00...........MOBIL 91 WAS USED IN ALL [email protected] 93.00 - 379.74...........SUNOCO 104 & [email protected] 15MPH HEAD WIND 95.50 - 381.31...........VP 100 & [email protected] 96.50 - 383.88...........SUNOCO 100 & [email protected] 98.00 - 390.12...........VP 109 (105 OCTANE) & [email protected] 101.5 - 379.33...........SUNOCO 104 & 100 & [email protected]
As much as I appreciate your attempt to quantify this, I think there a lot of variables that would prevent you making apples to apples comparisons at the track like this. You'd have to run exactly the same DA, same oil temp, same intake and coolant temp, have exactly the same weight in your car everytime and have perfect traction for every run to be able to point to the octane difference as the only variable. I vary by 2/10ths at the track quite often due to the above factors. I've run back to back runs with 100 octane vs. 91 octane mix and ran faster with 91. I can't say for sure it was the 91 or not, too many variables. When I test and tune I only compare runs with perfect traction, the same DA on the same day at the same track. Even then you have to do multiple runs to verify that one run isn't a fluke. I think averaging is a good idea but again there are lots of variables to consider.
Yes i agree but this was done just to see if my tune would handel the higher octane with out touching the tune as it was just for me but thought i would pass it on. As far as DA AND 60' they will never be the same through the day or night because of oil downs and weather temps and humidity. I tried to pick the thursday nights through out the months to try and get the DA as close as i could.
The higher the octane the less energy per gallon.....if everything was equal in your tests it may mean your engine is pulling timing on the lower octane due to spark knock??....other variables as mentioned above...
Yes but its so hard to get 5 test DONE over 5 months to have the same DA and track conditions BUT i tried. This will give someone at least how there car with a good cmr dyno tune may or maynot benifit from the higher octane.
I think there is some meat in your tests....running a car down the track pushes the engine to the limits....the motor was designed for street performance...WOT is usually short and not from a stop..........I do know that tuning for higher octane will make a diff....I have a 100 octane tune for my truck and it makes a very noticable diff....
Althought I agree that this test can't be taken completely at face value, I think there is some worth to it.
Well it might give someone an idea to tri it just to see if there tune will take to it WITHOUT doing any adjusting to the tune to take advantange of the higher octane as mine did. NOW HERES 2 RUNS I MADE WITH CA 91 GAS AND LOOK AT THE DA AS WITH MY TUNE IT DIDNT AFFECT IT AT ALL AS THERES 1617 FT BETWEEN THEM IN DA AND I NEVER TOUCH MY TUNE. As you see i ran them 2 months apart and there this 1 that i ran in april 2010. I have made 103 passes and the DA doesnt seem to affect it much. All runs on the same 91 octane tune with no changes to the tune. CA 91 0CTANE WITH 1.8% OXYGEN........93 OCTANE MIX WITH 3.37% OXYGEN MIX 9/09......................11/09.......................4/2010 DA.......3254...........1637........................1613 - THERE WAS A 15 MPH HEAD WIND ON THIS RUN 60'......1.786..........1.800........................1.747 330'.....5.301..........5.309........................5.179 1/8......8.246..........8.246........................8.089 MPH.....83.21..........83.37........................84.25
Jim, I think the thing is that there are a couple of dozen variables that all (each one by themself and then collectively) could effect the result significantly. As to using higher octane gas without adjusting the tune I would expect any higher octane to work just fine. It's when you have a tune adjusted for a particular octane and you go down in octane that you will have problems. Assuming your baseline tune and octane are adjusted for the best performance, you could only go down in performance by simply switching to higher octane gas without corresponding adjustments to the tune. There is less energy in higher octane gas. Here is one reason why you might get better performance simply using higher octane gas that Larry pointed it out earlier. Generally speaking, advancing spark will give you better performance. What usually limits how much you can advance spark is knock/detonation. lol, lots of people make their very best pass just before they blow the engine. With electronic control the PCM will guard (to some extent) against detonation by detecting knock and retarding spark to eliminate it. So you have some margin where the spark can be too far advanced in the tune and, under operation, the PCM will retard it below the critical point. Some tuners rely on this. I don't think it's optimal, good, or even safe in some cases, but it's simple, fast and easy. So let's say with your baseline tune and octane you are getting some initial knock but the PCM retards the spark 5* to eliminate it. Then you switch to a higher octane fuel (that burns slower and more evenly). Now the engine can run without detonation with more spark advance. Due to less or no knock detected the PCM retards the spark less or not at all. and you get better performance. So in this case (sort of) you could say that the PCM automatically ajusted your tune to take advantage of the higher octane. The way to verify if this might explain your results would be to log for knock retard with your baseline tune and gas.
Wow Jim, major props for all the effort. Might I suggest logging both advance and knock retard if you ever do this again. That'll give you a much better indication if the motor's happy and what you can adjust too.
Yes Dave this is all true but like i said i didnt want to touch the tune as i no i could of added timing and gone faster. The other thing was i wanted to see just what gas was better VP OR SUNOCO and the reason i chose diff octanes was to see what 1 it would benifit the most without changing the tune. If the 93 didnt work then i would another 1 till i found the 1 that was the best over all. This way i could also see what brand was the best as VP cost a lot more than SUNOCO. I really wasnt going to post this but then i fig what the hell lol.
LOL Cam i have only used the predator 1 time and that was to log basic timing in a 1/8 mile pass and when i launched it jumped to 25 degrees and stayed there 1/2 sec then fell to 24 degrees and stayed there the whole run. Ill have to try it on my next test as im redoing the 93 octane test as my passes at IRWINDALE THURSDAY we had head winds all night. My 1st pass the weather station we had showed 15 mph 2nd pass 12 mph 3rd pass 9 mph and 4th pass about 5 mph. For the cost factor running CA 91 GAS cost me 3.36 gall and 93 cost me 7.06 gal to mix and the best mix was the 98 octane at 8.88 gal. GEEEEE i hope my wife dont read this as were both retired on SS LOL.
Haha, if she does you can honestly tell her that it's an investment that will end up saving you a lot of money going forward since you'll know the least expensive gas to use (for racing). :bigwink:
It has cost me more than i though to test as i spent 290.00 on 28 gal of hi octane to do all my mixing as that 10.35 gal but now i no what to use.
