Bob Evans
Administrator
I tend to agree with you.
Gearing question
- Thread starter b13
- Start date
rebsfan4
Member
And then mutiply that by the course of a twenty lap race.
sCREamnClones
New member
Bottom-line answer on this discussion is....."What ever works BEST for You/Me!" However....I like 'smallest' combination for short/tight track and 'largest' combination for long/open track. (ie: same 'theory' as flywheels) 
Note: Until 'proven' otherwise
Note: Until 'proven' otherwise
alvin l nunley
Site Supporter
Actually 2.28 inches, so the 15/59 would have the advantage on the top, but the 16/63 would have the advantage on the bottom, coming out of the turn, and “all things being equal”, I’m going to guess they would equal out.
And I’m aware that if the 15/59 gets the lead on the start, he would have the top end advantage, but the 16/63 might have the advantage on the start.
And then you get into how much time they spend in, and coming out of, the turns compared to how much time you spend at peak RPM. The advantage, 2.3 inches, doesn’t get you a quarter of the way up on his rear wheel.
And of course I know this debate is worthless, you have to try it on the track.
For instance; if you change the ratio, will they both pull the same peak RPM. I have my doubts about that, from personal experience. And if the lower ratio does pull more RPM, they end up being equal again. If the lower ratio turns 6016 RPM, they’re at the same top speed.
Sorry, I carry on too much.
BrendanFitz #73
New member
Yes Al compression is king. It makes a slight difference in gearing but your only comparing the 2 ratios at 6000rpm just to find top speed. Can you find which will accelerate better?
I've always thought a smaller driver with a smaller rear gear gave better accel and a bigger driver and bigger gear gave more speed.
rebsfan4
Member
Bottom-line answer on this discussion is....."What ever works BEST for You/Me!" However....I like 'smallest' combination for short/tight track and 'largest' combination for long/open track. (ie: same 'theory' as flywheels)
X2 on that!!!
CarlsonMotorsports
Site Supporter
Compression is NOT the "Holy Grail" -- it is only part of the equation.
I've seen many times on alcohol engines (from 5HP flatheads to 850HP sprint car engines) that higher compression at a point only hurt power and that the engine made more usable power when it was able to "breathe" a bit more. There is a reason that not everyone uses Total Seal rings anymore. Personally, I am much more concerned with valve seal than ring/cylinder seal. Considering that legal WKA flathead Briggs engines are ridiculously low in compression ratio, you will find that angle milling the deck and head for increased airflow helps considerably more than increased compression. Perfect example is the Horstman fireslot head or 4 horse head, application in a stock appearing flathead -- a bit more compression, sure, but the airflow and tumble effect into the cylinder is so drastically hurt that it hurts the overall power of the engines.
Furthermore, egt is not the Holy Grail either....an overly rich (fuel) small plate (purple or blue) flathead will ALWAYS make more torque and CHP than a razor edge egt "properly" tuned same alcohol engine.
There's more to it than physics equations...and that goes for gear ratios as well. There is no black magic in gearing -- all the rules of physics still apply. Much like the arguments of engine building for optimum power output, there's a lot more to it than stating a ratio is a ratio.
I think that many in our sport get overwhelmed/confused by all this debate as if there is some huge monumental difference in changing from a 14T driver to a 15T driver (final ratios remaining the same.) If you start looking at rpm drops in the corners, you will start to see where there is a slight advantage from one driver to another. Also try to think of changes in larger increments - say 2 tooth driver (the chain going click - click around the clutch like a screwdriver) to a 400T driver (where the chain is wrapping around the clutch like a torque cheater bar at a MUCH larger circumference.) Consider the same on the rear sprocket.
This great debate about gearing (specifically which driver is best suited for a specific application) will continue until cows fly. The only one that ever did flew clear over the moon!
I think if you polled most of the top engine builders in the country, you'd see where they stand on this debate and thus what they recommend to their customers at the track. (ie if it's faster on the watch, run it! - at least for qualifying. )
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts
www.CarlsonMotorsports.com
765-339-4407
bcarlson@CarlsonMotorsports.com
I've seen many times on alcohol engines (from 5HP flatheads to 850HP sprint car engines) that higher compression at a point only hurt power and that the engine made more usable power when it was able to "breathe" a bit more. There is a reason that not everyone uses Total Seal rings anymore. Personally, I am much more concerned with valve seal than ring/cylinder seal. Considering that legal WKA flathead Briggs engines are ridiculously low in compression ratio, you will find that angle milling the deck and head for increased airflow helps considerably more than increased compression. Perfect example is the Horstman fireslot head or 4 horse head, application in a stock appearing flathead -- a bit more compression, sure, but the airflow and tumble effect into the cylinder is so drastically hurt that it hurts the overall power of the engines.
Furthermore, egt is not the Holy Grail either....an overly rich (fuel) small plate (purple or blue) flathead will ALWAYS make more torque and CHP than a razor edge egt "properly" tuned same alcohol engine.
There's more to it than physics equations...and that goes for gear ratios as well. There is no black magic in gearing -- all the rules of physics still apply. Much like the arguments of engine building for optimum power output, there's a lot more to it than stating a ratio is a ratio.
I think that many in our sport get overwhelmed/confused by all this debate as if there is some huge monumental difference in changing from a 14T driver to a 15T driver (final ratios remaining the same.) If you start looking at rpm drops in the corners, you will start to see where there is a slight advantage from one driver to another. Also try to think of changes in larger increments - say 2 tooth driver (the chain going click - click around the clutch like a screwdriver) to a 400T driver (where the chain is wrapping around the clutch like a torque cheater bar at a MUCH larger circumference.) Consider the same on the rear sprocket.
This great debate about gearing (specifically which driver is best suited for a specific application) will continue until cows fly. The only one that ever did flew clear over the moon!
I think if you polled most of the top engine builders in the country, you'd see where they stand on this debate and thus what they recommend to their customers at the track. (ie if it's faster on the watch, run it! - at least for qualifying.
)Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts
www.CarlsonMotorsports.com
765-339-4407
bcarlson@CarlsonMotorsports.com
alvin l nunley
Site Supporter
A lot of people will say this, but never give a reason why. It’s a mystery that will never be solved, I guess.
I’ve never been much on “trust me”.
I’m sure I’m just stupid to keep trying.
jack burroughs
member
Still sounds to me like a "broken record", just keeps showing up, why not just try the different combos and determine for yourself what is best, you do own a stopwatch or a timer of some type don't you? so why not just try and then you can have your own little speed secret?
Good to know we don't need Dynos, durometer, scale, and gear charts, just a stopwatch. Thanks for the info.
CarlsonMotorsports
Site Supporter
That's right - a stopwatch never lies. All those other items are great tuning and learning devices though. Not many times you'll see a dyno at the race track - but without it in the shop, we'd be guessing at best on quantifying the exact power made from your engine and the best place to engage the clutch.
rebsfan4
Member
Jack speaks the truth. The only way for YOU to know is to run both combinations of gearing.
This question will be ask over and over and over and over again and again and again and the same debate will come about EVERYTIME. You have those that know because they have done it. You have those who only theorise about it. And you have those who ask and only get more confused until they do it and see the results.
The biggest problem for most though is getting hung up on a certain ratio when the final ratio is irrelevant so long as you accomplish your best speed/lap time possible.
Wright4
Member
I agree, I try to base it off of RPM. Let's say I'm on a 17/65 turning 6100but I want to be at 6300, then I will change the driver to a 16/63. Is that right thing to do? I am on a small pipe clone. Some have told me to go up on rear gear for the 17 but for what ever reason I can get the clone to get any better with anything above a 65 for the Clone so I go to the drive and adjust. Is that the right thing to do, I'm fairly and still trying to judge a track fro gear and tire pressure..LOL
alvin l nunley
Site Supporter
When I say “compression is the Holy Grail” I of course am saying, (and I suppose I should include this every time) “all else being equal”.
And yes; you can have “too much” compression. I thought everybody knew that. Even the highest octane fuel has a limit to the amount of compression it can handle before it starts detonating. Once a fuel starts detonating, (and it starts long before you can hear it) the HP starts going down.
And you are, of course, right; the engine will make more HP if it can breathe “a bit” better. Most everybody knows that, even me. The thing is; can you explain why an engine can do that with less compression?
The ruling bodies of many motor sports go to great lengths to control the compression ratio of a lot of “controlled” engine classes, this alone should give us some indication of how important compression is.
rebsfan4
Member
If that gets you within your target rpm range and produces the best lap times then absolutely.
hillygoat77
New member
The way a guy showed me one night was two rolls of tape one was half used the other was new. He had me roll them across the floor of his trailer and asked me which one went further and the bigger one won. He said thats whats happening with the kart a bigger driver will still be pulling down the straight while the smaller one will be ran out.
GeorgeHenry
New member
That says it all
alvin l nunley
Site Supporter
And if that makes even one tiny bit of sense to you, then you’re half way to understanding why this subject goes on and on.