91 octain fuel

[J W Miller]

Put 5 gallons of 91 octain fuel in my RTS other day and bike really seemed to run a lot smoother and it felt comfortable putting along in high gear at 4000rpms with two up which it has not been able to do since I have bought it. Last fill up used 89 grade not as smooth but better then 87 grade.Seems most on this board use 87 octain. Looks like i will have to stay at least 89 grade. Milage seems the same (29.4) no matter what fuel grade. Have others found the above true or am I the only nut in the group. JW Miller

[major]

I have only used high octain as you discussed. The gas mileage is terrible.

Put 5 gallons of 91 octain fuel in my RTS other day and bike really seemed to run a lot smoother and it felt comfortable putting along in high gear at 4000rpms with two up which it has not been able to do since I have bought it. Last fill up used 89 grade not as smooth but better then 87 grade.Seems most on this board use 87 octain. Looks like i will have to stay at least 89 grade. Milage seems the same (29.4) no matter what fuel grade. Have others found the above true or am I the only nut in the group. JW Miller

[bcspyder]

All octane does is prevent detonation, particularly under load, or in high compression motors. I think I remember the Rotax is a sub 10:1 CR motor. There is no performance advantage although the placebo effect can be at work. For those that don't know higher octane fuel is actually harder to ignite, that is the reason it helps with detonation as there is less unintentional combustion due to cylinder temp. Many people feel that there is somehow more performance in higher octane because it is usually marked "extra" or "supreme". All marketing IMHO.

The reason you may feel a little rough during the riding you mentioned is because you are a little out of the powerband in 5th gear and 4,000 rpm. Especially two up I would be inclined to shift down to fourth and move into the right part of the curve. These motors NEED rpm's and you will find it much smoother there.

[docdoru]

Many people feel that there is somehow more performance in higher octane because it is usually marked "extra" or "supreme". All marketing IMHO.

Using Aurocharge Turbo: always require premium grade.

[InspectorGadget]

bcspyder said it best. I have been using 89 since running the first 2 tanks of 91. Never had a problem in 9000 miles.
Just keep the RPMs up and don't lug the engine and you shouldn't have a problem.
Have fun and ryde safe C-YA RL

[CyncySpyder]

Costs me a small fortune (But it's worth every penny) but I usually only run 91+ in my RT-S as it's called for in the Users Manual & I don't want to void my Warranty. After the Warranty period is over, I'll play a little with grades to see if I notice a difference or not

[J W Miller]

As for rpms I know that these bike like a lot of rpms and seldom use 5th unless ove 60mph. But with 91 in tank engine could be run at lower rpms! Makes no sense to me at all. I will from here on use nothing less then 89 It has taken awhile for me to get use to buzzing along at such high rpms compared to 2800rpms on my ex Voyager 1200.
JW Miller

[NancysToy]

BRP recommends premium fuel for the RT model, for a reason. The ECM will adjust to lower grades, but performance will be reduced. Your manual explains this. If you get 25 mpg, and ride 25,000 miles per year, the additional cost of the premium fuel is only $200 per year. Each rider needs to decide if the decrease in performance from using regular, is worth saving $200 per year. To me, it is not...I will continue to use high test.

[effgjamis]

Scotty..

As to MPG.. I only get 25 with a high side of 27 average Regardless of solo, solo with trailer, with teacher, or with teacher and trailer.

I was using 91 as the book calls for.. I have in the past two weeks changed to 87.

I found no difference in mileage nor performace. The engine sounds and runs the same.

My measurement of MPG is riding on expressways 90% at 70-75 mph. Rpm's being 5500-5800.

Yes... Wheeler will state I got 32 mpg once. However, we did not exceed 45 mpg for almost 80 miles and I did not leave 4th gear.. This has not been repeated ( 32 mpg ) since.

[chris56]

in europe most contrys have 95 octain - only in italy you can get the shell v-power (100 oct) .. my feeling is the RT runs better more smooth and likes that .. little stronger & less fuel - but still sometimes (hot engine) she starts very bad ..
chris

[Y Rider]

Has anyone noticed a difference when using non Ethanol fuels? With my HD Ultra Classic I have always used 91 octane but if all possible I would stop at a Shell station for fuel. Shell and Amoco stations around here don't add Ethanol. The bike seems much happier without it. Not sure about the Rotax V-Twin.

[MouthPiece]

Don't get me started on ethanol. I'll be ranting and raving for three hours reference the stupidity of adding this stuff to gas. However, yes, I do believe it does effect gas mileage. I personally think about 3 to 4 miles per gallon.

Chris PE # 0004

[Lamonster]

[NancysToy]

+1 !!!

[GypsyBill]

I know the ECM will adjust for different octanes.. but the manual for my RTS states the engine compression ratio is 12.2:1. In a few other vehicles I have owned or built, that kinda compression ratio almost demanded 91 or better pump gas.. but then again those were carb non computer engines (yes I am dating myself).. but to this thread.. I have run all octanes from 87 to 93 and haven't noticed much of a difference.. it does seems to like the higher octanes if I am running 5th gear under 5K (doesn't happen often here in the Texas Hill Country with all the ups and downs and twisties). Disclaimer: I only have 1350 miles on my RTS. As far as fuel cost is concerned.. my other vehicle is a '09 F450 (6.4ltr diesel with 4.30 rear gears) so I am used to "high" fuel prices and piss poor fuel milage.. heck, premium gas is a break for me..

[docdoru]

+1 !!!

http://losangeles.cbslocal.com/2011/...senate-follow/

[Bootie]

BRP recommends premium fuel for the RT model, for a reason. The ECM will adjust to lower grades, but performance will be reduced. Your manual explains this. If you get 25 mpg, and ride 25,000 miles per year, the additional cost of the premium fuel is only $200 per year. Each rider needs to decide if the decrease in performance from using regular, is worth saving $200 per year. To me, it is not...I will continue to use high test.

[boborgera]

I believe the following to be true, at least in the Northeast:
Premium grade fuels do not contain ethanol.


If anyone knows the contrary let me know.

I think you'll find all Premium has Ethanol [n/east] ,it's used as an octane booster among other things.

[cjackg]

Near Chattanooga there are several stations that offer all grades with No Ethanol.

Sent from my DROIDX using Tapatalk

[rogerb]

Up here in Maine we have the ethanol additive and the highest octane is 91. Our last governor wanted to save the world from polution. I have to use 91 in my RT especially when its hot out. But when I can I fuel in New Hampshire where they still have real gas(93 octane no ethanol) and its also cheaper. But the way gas prices are going now we won't be able to afford riding our Spyders we'll have to trade them in for Vespas. The prediction is for $4 a gallon by June. We're paying more for heating oil right now than gas and heating oil has no taxes. Somebody has to pay for the Gulf oil spill.

[Bob Denman]

Somebody has to pay for the Gulf oil spill.

I heard a little about this whole pricing deal this morning...
While Libya doesn't provide us with much oil; it does send it to Europe. Now that they're worried about their supply, their competing with us for OUR supplies... Jacks the price up for sure!

[Marker]

+1 !!!

+1=2 In my opinion Ethanol

[dancogan]

in europe most contrys have 95 octain - only in italy you can get the shell v-power (100 oct) ...

Chris, I believe measurement of octane rating is done differently in Europe than here in the U.S. I don't know how to do the conversion from one to the other but I have seen it in the past. It may be that your 95 octane is the same as what we rate at 91 ... something like that.

[docdoru]

Chris, I believe measurement of octane rating is done differently in Europe than here in the U.S. I don't know how to do the conversion from one to the other but I have seen it in the past. It may be that your 95 octane is the same as what we rate at 91 ... something like that.

EU ratings are 95/98, which are equivalent to US ratings of 91/93.

EU 95 octane = US 91 octane and EU 98 octane = US 93 octane

RON: Reaserch Octane Number in EU
MON: Motor Octane Number.
AKI: Anti-Knock Index. This is the number that is posted on the gas station in the USA as "Octane"= (RON + MON)/2

[StriperKing]

Just make sure everyone is aware of the difference between the RS and RT. The RT does run a higher compression ratio than that of the GS/RS and that is why BRP recomends higher octain for the RT. The RT is 12.2:1 and the RS is 10.8:1. Octain slows burn rate and is harder to ignite, compression increases burn rate and makes fuel easier to ignite. Lower compression will run better on lower octain and higher compression will run better on higher octain. There are some very complicated mathmatical formulas for all of this. The objet is to get the fuel ignition point at the desired piston location and the burn duration for a desired length of piston stroke. High compression and high outdoor temps mixed with city stop and go traffic is a bad mix for high compressin engines (12.2:1). If your engine pre-detinates you may not really know just how much but trust me your engine does.
Fact, high octain fuel in a low compression engine is a waste of $ and will probably rob HP. What happens is the burn rate slows to a point where the fuel does not all burn through the desired piston range. This is not the desired condition. By the way low is in the 8`s, low 9`s.
Fact, low octain fuel in a high compression engine does not create max efficiency. The higher compression causes fuel to burn faster (faster flash rate) so the fuel will be all used up before the desired piston range has completed leaving a dead zone in the stroke. High comp. at least in my oppinion is about 12.5:1 and above. 10.8:1 is somewhere in the middle so no you probably can not tell one grade from another. If you have an RT as some of you have noticed, you should be able to tell 87 from 93. Right now it is cool so not as big of a deal. This summer when it is hot as @#$% it is a bigger deal.
Just incase some may not know why low octain is so bad for high compression here is a short explanation. All modern engines ignite fuel before the piston reaches full compression or the top of the stroke (TDC) so that the max flash point can occur just as the piston starts its down stroke. If you use fuels that flash to fast you will reach this peak before the piston is at the top of its stroke. This wastes some of the fuels efficiency and literally tries to shove the piston backwards (pre-ignition).

There is way more to this but I made it as simple as I could. Bottom line BRP makes the recomendation for higher octain in the RT for a reason, not just to suck $ out of your pocket. Hope this helps.

PS: I know my spelling is bad but hope it`s not so bad you couldn`t read it.