One of the problems was that he discusses locking sensor voltages. Unless you have a standalone or ECU flashing ability... this is not an option for the majority of tuners.


And as far as S&Ds Ethanol blending, I meant to address that last bit seperately, and he is correct, ethanol does like higher IATs for fuel economy purposes, and it can release energy more efficiently, but there is a sweet spot for it.

Its for the same reason that on cold days when you go to start an E85 engine, the alcohol might not catch. At least not on the first few tries.

Higher temps = better atomization = more complete, efficient combustion

 

I found a dyno test and even though its top end cars, remember Honda is Japan and also has 102 ron fuels. http://www.tesco.com/Momentum99/file...uel-Report.pdf , Thorney Motorsport - Fuel Test Results Update

 

Anyone that needs to see scientific test procedures applied to different levels of octane fuel and the results of the test on a number of cars in order to form an opinion of whether higher octane fuel improves fuel mileage and power output needs to look at this link.

 

Quite surprising results. I understand many UK cars would be tuned to take advantage of 99 RON fuel, but I wasn't expecting such a huge difference between the blends.

 

The 99 ron fuel is very close to BP ultimate 93 octane. Specifications - Product Benefits - MOMENTUM99 - Tesco.com . What I dont understand is modified, If the ecu runs MBT then it optimized and if you tune for max brake torque in the fuel, it would be 13.2-13.8 A/F and that would not give best mpg. Anyways I got fresh gas and it warmed up and I am getting summer mpg. I thought my scan gauge was broken but it works fine. I got 65 mpg going 2 miles after I got gas and got 48 mpg on the way to work and the temp dropped and got 34 mpg on the way home. The temps and gas is whats killing mpg.

 

MBT was explained as Mean Best Torque in the Hondata article.

13.2:1 would actually be leaner than the 11:1 the Fit ECU typically runs.

 

When I dynoed my Fit it ran lean through out the rpm band 14.2 and it never ran 11:1. 14.2 is 14.7 because of the oxygen in the gas. 15.6 is best mpg and 13.2-13.8 in Max. brake torque and best Hp is 12.5 The 11.0 is probably a tuning reference for add ons and running bad gasoline.

You are right on what Hondata said, but I knew it as minimum brake torque and this article say max. brake torque General Air Fuel Ratio Effect on Engine Performance. No wonder I am confused. I do know it the least amount of timing needed for max efficiency, because of higher efficiency's of the motor.

 

Exactly right!

Though on a hot day on poor fuel it pegs 9:1 @ WOT in certain load cells because of our compression ratio.

For those who have the option to tune their car, and don't have to worry about emissions but want excellent mileage you can burn pure gasoline as lean as 15.4:1AFRs under idle and cruise. But OE tunes don't often allows this anymore because you would fail emissions through excess NOx among other things when burning that lean and hot.

So often the leanest you'll see is stoich or Lambda 1.0v on a narrow band oxygen sensor on an OBD2.

What sort of timing and AFR is everyone seeing under idle and cruise? I know some of you guys have scan tools!

Last time it was on the Fit it was seeing as much as 43* under cruise and 25* under WOT. But that was on Shell E10 93oct.. I have since switched to BP 93 as an experiment on a tip from SB. So far, it feels like there is a tangible difference on cold starts which is expected because there is no ethanol in BP 93. I think I get slightly more response and pull at the top of 2nd and 3rd, but I won't know for sure until I have run a couple more tanks through.

I used my OBD2 datalogger which is not as nice as everyones scan gauge but gives me every single thing going on in the ECU, But no live read out read out.. Its only about the size of a tangerine after all.

I have to plug the logger into a computer afterwards and check it out but after a while of looking at logs you can actually see what the car is doing and what the driver is doing.

 

The gas station I go to must of got fresh premium, MPG is way up. My car runs 27 degrees at WOT and runs 32 around 60 mph. It never goes higher than 45 degrees timing. DSM if you look at Tesco 99 msds sheet, I am sure its similar to Amoco ultimate 93. I just wish that info was easier to get that info rather than going to other countries websites to get it. The scan gauge doesn't give fuel trims,or A/F ratio for Honda like on some cars. The fuel trims worked on the van but not the O2. I might have to reprogram the X gauges and they might work on this car.

 

Call me a cynic, but I don't entirely trust a study conducted by the company that sells the fuel being studied.

 

Then how do you buy things? All company's do there own tests. Gasoline is easy to see the results with out going broke.

 

imo the higher grade is a waste, unless you have boost or something.

 

Get a scangauge or ultra gauge and check out how the ECU compensates by pulling ignition timing and requires a larger % of throttle to be opened to maintain the same speed when using 87 octane instead of 93 before you form an opinion... It does make a greater difference in improving the power of a boosted engine and water / methanol injection makes even more... If you don't drive in a rather sporting manner, have to climb steep hills, accelerate hard to comfortably get on a freeway you may do fine using 87, but if you want your car to have a bit more power the 2 easiest things you can do is to use 93 or higher octane fuel and colder heat range spark plugs... A lot of people that had the same opinion as you have been open minded enough to use a few tanks of 93 octane to see for themselves and are still using using it because they have and opinion based on their own personal experiences.

 

Exactly- if I feel I want to test different kinds of gasoline, I can do it myself, or even get a "non-partisan" opinion from users of this site. I'm just saying that, when someone with an obvious interest conducts a study, it should always be read with a critical eye.

 

Exactly, I use mid grade in wifes Civic just because its quieter and mpg is up to 29 instead of 26. It depends on how far north you live and how you drive. Mpg is one reason I use premium but there is more, a better running car with better acceleration and I see the operating temp in the 180 instead of 190's also I see timing in the MBT range with means a learner burn with good power. The Cat temps are in the 1200 degrees during cruise and can go up to 1400 during hard acceleration. There was a guy at work that said the cats burn out but after reading the safe cat temps is 1200 to 1600 which Ive never seen. There is alot of info through out these pages and the engineers even say there is a difference.

If your happy using regular and getting in upper 30s in mpg then premium wont make a big difference. There is a difference between brands and types, so experimenting till you find what is best. In Japan they recommend 95ron octane which is 91 here in the states and Regular in the 80s was 89 octane and then they had unleaded.

 

I have been running 87... if I was to switch to a higher octane should I try to reset my ecu to relearn the new grade or will it just make the proper adjustments? thanks...kirinzon

 

I would also add, if you have control-of and a willingness-to shift gears, then higher octane can improve acceleration. Both are less likely on an AT, even with paddles.

 

No you dont have to, Ive been switching back and forth with mid grade to premium with no side affects. If you go from premium to regular on a empty tank I would do a relearn but its not necessary with the new ecus as long a you dont drive the car hard.

 

My shifts are improved with an automatic trans on premium over regular.

 

ty. I wish we could go back to the day with no ecus...when an engine gave you all it had and wasn't held back to meet advertised mpg estimates...kirinzon