Re: What gas you runnin?

> ken gilbert Wrote:

> -------------------------------------------------------

> > Larry Baltz Wrote:

>

> > -------------------------------------------------------

>

> > I thought compression ratio was just the ratio of the volume in the

>

> > cylinder with the piston at bdc vs. tdc?

>

> >

>

> > I don't believe compression ration can be calculated with a

> compression

>

> > tester.

>

> gentlemen,

>

> what exactly do you think the compression tester measures?

>

> what do you think the term compression ratio means?

>

> the theoretical ratio of (swept+combustion chamber)/combustion chamber

> is the static value. great if you're designing the engine on paper, or

> have it disassembled. academic and useless when it comes to perfomance

> metrics or diagnosis.

>

> for example, poultry man here has two jugs that should be ~150psig. he

> measures quite a bit lower, and with a large spread. alarm bells,

> something's fucked. i believe him when he says he doesn't knock--with a

> leaky piston his ACTUAL cr is too low.

>

> my bone stock chappy tested a little shy of 100psig.

>

> mfgs rating for lb50 is 6.6:1. scroll up and read the chart.

>

> I installed a kit, shaved the head, and measured 150psig.

>

> slightly over 10:1.

>

> I scored the rings and bore after a seize. measured 100psig.

>

> did my swept or cc volumes change? no. but my ACTUAL compression ratio

> sure as hell did, and I could tell via the manometer.

I agree. Thus a "dynamic reading" that shows actual condition or state of parts rather than a theoretical basis. Although, basis is important, it shines on multi cylinder motors when balance will make more of a difference. Valve timing or in this case, port timing can influence final compression as measured by a guage.

Speaking of books..

s-l400.jpg

(edited)

Re: What gas you runnin?

Although compression ratio surely is a major factor in determining the need for specific octane fuel, we might need a new forum topic.

Here's an article that will make everybody happy:

https://www.autoblog.com/2016/02/23/how-to-determine-compression-ratio/

Re: What gas you runnin?

wow blast from the past. that's the book I was talking about. and I still have it. really good read. will explain where to put end gaps when installing pistons and lots of common sense checks and fixes, simple porting. teaches you how to blue print an engine as you are building it.

read that book if you can.

slightly over 10:1.

I scored the rings and bore after a seize. measured 100psig.

did my swept or cc volumes change? no. but my ACTUAL compression ratio sure as hell did, and I could tell via the manometer.

like I said unless you are lc you can forget about running premium. 2t's are low compression. keeping it cool is what its all about.(edited)

Re: What gas you runnin?

Dame más gasolina(edited)

EC1C2201-4A88-44EF-8252-2A46829287B7.jpeg

Re: What gas you runnin?

> LSLB Lou Wrote:

> -------------------------------------------------------

> Dame más gasolina

no flour

Re: What gas you runnin?

I am running alkylate gas and mix Castrol Power 1 Racing fully synthetic oil to it to run with my Puch. Overkill - probably yes, but all gas is so expensive here one might as well use the best available. Our long winters make sure the driving season is short so gas costs are not that substantial.

Positive thing is that alkylate burns really clean, its high octane, no ethanol, doesn't deteriorate rubber and does not go bad over time, so it will not gum up the carb during winter storage. We can buy it from the gas station pump too so its easy to get.

I am running 3% oil mix with new motor and then 2% after break in.(edited)

Re: What gas you runnin?

We have here only 95 and 98 type of gasoline.

And awful e10 with 10 percent of spirits.

Re: What gas you runnin?

95 europe octace = 91 USA

98 europe octane = 93 USA

Alkylate gas is 104 europe octane, maybe 96 USA

The conversion is not linear so there is no fixed number to calculate with.

I think alkylate is sold in most countries in Europe but maybe not at the gas station. They sell it by 1 and 5 liter cans at hardware store for chain saws etc. but its super expensive like 3x the pump price.

Re: What gas you runnin?

Ethanol is a magnet to condensation and water not good for any car or moped gasoline without additives are the way to go

Re: What gas you runnin?

I had been running anything up until this past month, but a new Wawa just opened down the street and it is very handy location for me. I have 30 bikes and have now switched to non-eth 89 octane. The Wawa pumps have a blue handle just for non-th 89, so no matter how small a quantity, you will always get pure non-eth 89 there. I still run each of the bikes at least a few miles every month.

Re: What gas you runnin?

^ What's a Wawa? (non ethanol is the best).

Re: What gas you runnin?

Google is a wonderful thing:

https://www.wawa.com/

Re: What gas you runnin?

Ha, thought it was an abbreviation for something, oh well, at least you have access to good fuel, I get mine at a local Shell station. I see you don't post much, I'm one of the troglodytes..when I don't know something, I tend to ask a person not the google, my bad in today's world. :) Dumb name for a store though, but hey they seem to be doing well!(edited)

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