octane & compression ratio in Buddy 125 and 170i

bradsarno · Post by **bradsarno** » Wed Sep 04, 2013 9:03 pm

Yeah, I know the topic has been hammered to death and has left many with somewhat vague answers, but I did just learn some tech spec's directly from Genuine regarding the Buddy 170i and Buddy 125 compression ratios and how that relates to the appropriate octane levels to shoot for in each. I must assume they're speaking in USA terms with regards to the octane ratings as they are a Chicago based company relating to an American Buddy owner.

Brad

Info directly from Genuine Scooter Co.

"The Buddy 170i has a high compression ratio of 10.5:1, so it is recommended to run mid grade 89 octane or high grade octane 91...

(then after another question regarding 92, 93 octane) :
91 octane will work fine, I know the price is not much higher for 92/93 but it nice to save a little. "

"For your 125 running 89 octane mid grade will be enough, since the compression ratio is 9.2:1."

GrFa · Post by **GrFa** » Thu Sep 05, 2013 2:52 am

Great info. But what about the 150?

Post by **ericalm** » Thu Sep 05, 2013 5:01 am

Was this in response to email questions?

I ask because it sounds as if the answers are recommending the highest octane you should run. It would be nice to know the original questions and have a little more context.

There are a couple other considerations. Gas formulations vary in some states (in some, such as CA, there are seasonal changes) and also have varying amounts of ethanol.

All that aside…

In 7 years, there has been no info ever presented on MB either demonstrating any benefit to running high octane or any issues from running 85/87.

And…

Riders are more likely to experience reduced performance and MPG when running too high an octane for the engine.

bradsarno · Post by **bradsarno** » Thu Sep 05, 2013 5:23 am

Tomorrow when I get to my email computer, I'll dig up my questions that triggered those answers.

My take is that we want an octane high enough to not ping, or pre-detonate. This is only likely to happen in a high compression motor. The 170i is apparently pretty high compression, so a reasonably high octane seems appropriate. For lower compression motors, the cheap stuff should be fine.

I do find it interesting, this discussion about the risks of TOO high an octane as the higher rated octane is said to burn slower, and we surely don't want it still burning as the exhaust valve opens.

Then we have issues of spark timing that again can relate to the issue as well.

Then we have the fact that the octane number on the pump has been said to, in reality, test a few points lower than stated, like 87 may actually be 84, 92 may be 89. And this varies from brand to brand, time to time, etc.

And then there's the ethanol factor and how that affects certain motors and the combustability of various fuels.

After reading thread after thread on the topic, I was left still curious.

So, my basic point of this thread is to simply share the data of the compression ratios in the Buddy 125 and 170i. Seems to be useful information in this larger octane conversation as we all would love to know just what fuel will make our particular scooter run cleanest, fastest, longest, and most efficiently.

B

Wolfhound · Post by **Wolfhound** » Thu Sep 05, 2013 12:08 pm

Owners Manual which covers 50cc-170i cc says in regards to fuel type: unleaded only. That is all it says. With regards to tire pressure for all
scoots it recomends 22 psi front, 25 psi rear. On the 170i badge on the scooter it says 30 psi both tires. I run regular unleaded with Stabil and 30 psi
front and rear. In my opinion the OM is a "one part fits all" type and not of
a great deal of useful information.

bradsarno · Post by **bradsarno** » Thu Sep 05, 2013 1:36 pm

Wolfhound wrote:Owners Manual which covers 50cc-170i cc says in regards to fuel type: unleaded only. That is all it says. ....... In my opinion the OM is a "one part fits all" type and not of
a great deal of useful information.

I totally agree. Clearly a higher strung engine with a high, 10.5:1 compression ratio is going to want a little bit higher octane than a lower compression engine would call for. I had to bug the company to get a more detailed answer.

B

Wolfhound · Post by **Wolfhound** » Thu Sep 05, 2013 2:52 pm

Now here is a possibility. Octane ratings are interpreted differently in other countries. As a result what they use as hi test is actually regular in
our country. At least that is how it was explained to me when the Tank owners manuals recomended super unleaded fuel.

Dooglas · Post by **Dooglas** » Thu Sep 05, 2013 4:26 pm

Actually, I burn premium in all my scooters all the time. Premium is definitely recommended for the Vespas. Our Buddy has run fine on premium for years with no problems. I usually fuel the bikes out of a gas containor in the garage so using the same fuel for all of them is just simpler.

Wolfhound · Post by **Wolfhound** » Thu Sep 05, 2013 5:06 pm

I do the same thing as you do only I burn regular and have never had a problem because of it. Works for me

BuddyRaton · Post by **BuddyRaton** » Thu Sep 05, 2013 9:59 pm

Dooglas wrote:Actually, I burn premium in all my scooters all the time. Premium is definitely recommended for the Vespas. Our Buddy has run fine on premium for years with no problems. I usually fuel the bikes out of a gas containor in the garage so using the same fuel for all of them is just simpler.

I've done that too. Any 2T I run high octane so when we are out and filling a vintage and the Buddy the Buddy gets premium. It probably runs a little hotter but I have never really noticed a difference.

Post by **ericalm** » Fri Sep 06, 2013 12:40 am

Wolfhound wrote:Now here is a possibility. Octane ratings are interpreted differently in other countries. As a result what they use as hi test is actually regular in
our country. At least that is how it was explained to me when the Tank owners manuals recomended super unleaded fuel.

Yep, our lowest octane in the US is equivalent to the highest in most other countries.

Dooglas wrote:Actually, I burn premium in all my scooters all the time. Premium is definitely recommended for the Vespas. Our Buddy has run fine on premium for years with no problems. I usually fuel the bikes out of a gas containor in the garage so using the same fuel for all of them is just simpler.

I use high in my Vespa and the Stella 4T. I noticed a performance difference with the Stella, but who knows, could be in my head. These things are so subjective.

High is what Vespa recommends, so it's what I use. Never really questioned it because it runs fine and my MPG sucks anyways because of all the performance mods. (Which makes me wonder how compression ration is affected by rejetting, performance carbs and exhausts…)

Even the higher compression 170i is still fairly low all things considered.

All in all, my attitude is basically "do what works for you, just don't buy the cheapest stuff on the block."

Wolfhound · Post by **Wolfhound** » Fri Sep 06, 2013 1:32 am

I buy name brand fuel. keep 10 gallons at home treated with the correct measure of StaBil, have always done it this way.I have seen what ethanol
can do to a carb. Not pretty.

BuddyRaton · Post by **BuddyRaton** » Fri Sep 06, 2013 2:34 am

Wolfhound wrote:I buy name brand fuel. keep 10 gallons at home treated with the correct measure of StaBil, have always done it this way.I have seen what ethanol
can do to a carb. Not pretty.

Carb is nothing. You should see what it does to 2T oil seals...many cases split.

Ethanol sucks!

Wolfhound · Post by **Wolfhound** » Fri Sep 06, 2013 9:56 am

Wait til the 15% ethanol hits the market big time. It will have adverse effects on all gas powered equipment.