Big cams and Bernoulli's principle (venturi jetting)

Mine still has 165 PSI. When I bought it in 1979, it had 700 miles on it. Compression was good. Used Regular 87 gas....

Honda recommends 86 Octane PON

Honda CB360 Owners Manual:



Use 91 Research Octane (RON) or Pump Octane (PON, How it is sold today) of 86 or higher. I have always ran regular 87 in mine.

CB350 is the same compression PSI, same RON recommendation. When the country switched over to PON from RON, I used 87 in my CB350 (back in the 70's) without issues.

My Older Honda's never pinged or knocked on 87 PON.

My 1991 Nighthawk 750 has a compression PSI of 142-199 PSI...Also uses regular 87 Octane.

No reason an engine with 170 PSI compression needs anything but regular gas.....You can put 91 in, it won't hurt....but is just extra $$ to the oil companies.

Compression is not the only deciding factor in octane requirement for any engine. spark, displacement, port design, volumetric efficiency, just to name a few.

this is a general rule of thumb

"in general, a cranking compression of around 170 is safe, but the maximum one would want to run with 91 octane gas."

it is far more intelligent and safe for inexperienced people to follow this to have additional insurance against detonation . . not all engines are tuned the same or have the same capacity for cooling etc.

i have seen many engines with 170 psi detonate on anything less than 91 octane.

to say or imply that any engine with 170 can run on 87 without detonation is simply wrong and a very bad idea.

also, the fact that your book says 87 has no relevance to the fact that mine said 95.

barnett468 said:

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Cute....if your half the man you claim to be post up your name so we can atleast see if your full of yourself or you are who you claim to be..

I didn't imply anything. Honda explicitly says it in the owners manual.

Not my opinion. Can you explain why Honda recommends 86 PON and that the engine works well on it ? Compression is 170 psi on a fresh engine.

Are you mixing up RON ratings and PON ratings?

DohcBikes said:

..................., port design.............

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How so? As a function of VE as it relates to how well the cylinder fills at certain engine speeds or on some other basis? VE is relevant because it relates to cylinder filling and effective compression ratio. One of the most important thing in detonation resistance is combustion chamber shape and size. That includes bore width, squish band design, etc. Ignition timing can be a problem in a motor with poor knock resistance. Engine heat is another huge variable. The hotter the charge is the more likely it is to detonate. That heat can come from too much compression or from poor heat transfer , lean mixture, too much advance etc.

Lots of variables to consider.

teazer said:

How so? As a function of VE as it relates to how well the cylinder fills at certain engine speeds or on some other basis? VE is relevant because it relates to cylinder filling and effective compression ratio. One of the most important thing in detonation resistance is combustion chamber shape and size. That includes bore width, squish band design, etc. Ignition timing can be a problem in a motor with poor knock resistance. Engine heat is another huge variable. The hotter the charge is the more likely it is to detonate. That heat can come from too much compression or from poor heat transfer , lean mixture, too much advance etc.

Lots of variables to consider.

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Honestly teazer i cant tell if you are asking me a question or just reiterating what I just said. Im not sure who the explanation was for but im sure they appreciate it. All good info.

EDIT, Ok now i see. Yes, port design, as in how it correlates to VE. Or more importantly vice versa.

It is a mistake to directly and soley correlate compression with octane requirement. There are many other deciding factors. You all are talking in circles about nothing to try to be right about something. Have fun with that.

1fasgsxr

Who has barnett468 claimed to be? If you are simply implying that he didn't work for Kawasaki R@D, and didn't play a large role in the engineering and performance of several kawasaki models, then you are wasting your time and barking up the wrong tree. Furthermore, it is his right to protect himself by not plastering his name all over the internet. The reason I am addressing this is because I know for a fact that he has done every thing he claims here and that is the tip of the iceberg as far as his impact on the motorsports industry.

People have gone down this road before and ended up eating crow pie. Barnett468 enjoys it, so by all means keep it up and so will he. Oh and don't forget to pile on folks, itll take several jealous people to rattle him.

Or you could just grow the fuck up. If you don't like what he says, how bout you just ignore it.

He has already helped several members here fix their bikes and when you do this, it takes away from what we are all doing here and makes you look like a drama queen.

Carry on.

Yup thats me the drama queen..and thats exactly what I was getting at....I dont beleive everything I read in these forums...If has has done all these things my hat is off to him. Thats why I asked the question...and I will not be eating any crow as I have not put myself in that situation. and dont tell me to grow the fuck up..address that..you carry on..

Mydlyfkryzis said:

I didn't imply anything. Honda explicitly says it in the owners manual.

Not my opinion. Can you explain why Honda recommends 86 PON and that the engine works well on it ? Compression is 170 psi on a fresh engine.

Are you mixing up RON ratings and PON ratings?

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ive already explained it . . i have had engines with 170 psi that i could run on todays 87 . . once again, my statement was a GENERAL rule of thumb . . the point is, most engines will NOT ping on todays 91, however, because some will, it is simply SAFER to use this as a GENERAL guideline. . . i have seen people with vehicles that ping to high heaven but they keep on driving them because they dont know it is a problem because they dont understand what it is . . this does not make them stupid, it only means they are unimformed or simply dont hear well.


if one is an experienced engine builder, they will know EXACTLY what i am talking about, but they will calculate the compression they need for the particular build and wont use my guideline because they dont need it . . the guideline is for people that do not know much about these things and it is simply a bad choice to run 87 in an engine with the same compression as yours just because your neighbor joe the plumber can get away with it.

i never said an engine with 170 could never, ever, run on todays 87.

you also keep harping on the fact that your book suggested 87 and neglect to answer why i had one that said 95.

as mentioned, it seems like you are focusing on a non issue and trying to make something big out of nothing.

1fasgsxr said:

Cute....if your half the man you claim to be post up your name so we can atleast see if your full of yourself or you are who you claim to be..

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.....


Yup Barn, its obvious you are half the man you claim to be!

1fasgsxr said:

Yup thats me the drama queen..and thats exactly what I was getting at....I dont beleive everything I read in these forums...If has has done all these things my hat is off to him. Thats why I asked the question...and I will not be eating any crow as I have not put myself in that situation. and dont tell me to grow the fuck up..address that..you carry on..

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i have done everything mentioned above and much, much, more . . it has been my job most of my life, so i would certainly hope i learned something along the way . . this is not to imply that i know it all because that would simply be stupid, however, i know a bit.

as far as my name goes, you would not have ever heard of it so it would have no meaning to you, therefore it is irrelevant . . you would find it in some old magazines but it would still not mean anything . . you might have also seen me in a commercial for a major motorcycle mfg, but again, since i am not tom cruise, it wouldn't mean anything to you.

as far as not believing everything you read on the net, thats obviously wise . . a lot of people with good intentions often offer advice that is less than optimal or post opinions as facts which is where one of the biggest problems occurs imo.

the other prob occurs when people naively believe everything they read [like some national enquirer readers] and never try to verify the info.

also as was mentioned, nobody is getting paid here and there is no prize to win for being right, therefore i see no need for some to act as though there is.
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DohcBikes said:

EDIT, Ok now i see. Yes, port design, as in how it correlates to VE. Or more importantly vice versa.

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I'm asking. You mentioned port design and I wondered if that was as it relates to VE or now I think more about it, maybe you were thinking about swirl and tumble which impact combustion chamber turbulence and propensity to detonate. It's OK I just answered my own question. Carry on H2tuner.

I answered your question. I also gave the info that you used to try to look smart. Par for the course.

..

barnett468 said:

i have done everything mentioned above and much, much, more . . it has been my job most of my life, so i would certainly hope i learned something along the way . . this is not to imply that i know it all because that would simply be stupid, however, i know a bit.

as far as my name goes, you would not have ever heard of it so it would have no meaning to you, therefore it is irrelevant . . you would find it in some old magazines but it would still not mean anything . . you might have also seen me in a commercial for a major motorcycle mfg, but again, since i am not tom cruise, it wouldn't mean anything to you.

as far as not believing everything you read on the net, thats obviously wise . . a lot of people with good intentions often offer advice that is less than optimal or post opinions as facts which is where one of the biggest problems occurs imo.

the other prob occurs when people naively believe everything they read [like some national enquirer readers] and never try to verify the info.

also as was mentioned, nobody is getting paid here and there is no prize to win for being right, therefore i see no need for some to act as though there is.
.

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Now thats a great answer..Thanks for not being a dick about it like DOHC !! You have earned my respect..not that would mean anything to you...