How to Calculate MPH, Axle Ratio & RPM. Take the guesswork out of building a drivetrain for your car
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- Опубликовано: 17 май 2021
- Simple How to! How to build your car from the rear tires forward! Don't Guess, do the math. It's SIMPLE. Using Axle Ratio and RPM to calculate the cruising and top end RPM for your car!
#AxleRatio #Fabrication #RustToRevival #welding #metalfinishing #SuperClean #OldCar #VintageCar #abandoned
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I really wish you were my math teacher back in school, that made complete since! Unlike most of the math classes I took haha. Using your formula, I ran the numbers on the Death Charger and it tops out at 45mph with 6.17 gears and 37 inch tire haha. Definitely not my going to town truck. Great video Mike! I will be using this math on my future builds!
I’m the same as you. Math never made sense to me in school. I failed miserably because of no practical application.
@@MyKARSShop Albert Einstein wasn't a good student either.
Thanks for this video!
You are very welcome. I hope you enjoy the channel. I try to share both educational and entertaining information.
I didn’t know Paul Giamatti‘s brother was a petrolhead 👍
😂😂 thanks for watching
Numbers made fun, good stuff dude....
numbers can be fun when they make sense. Especially when they apply to our cars. 😎
Perfect explanation... math can be fun!
If only they would’ve taught us this in school
Thank you
You're very welcome
Sometimes the simple calculations make all the difference
Thanks for watching. Hope you’re enjoying the channel.
Hello. You mentioned that there is a further calculations about horsepower needed for a certain rpm. Do you have any video regarding the hp? Thanks
I have done nearly 500 videos in the last 4 years, but I don’t recall having done one on calculating horsepower yet. Stick around. I probably will do one eventually.
@@MyKARSShop I appreciate it.
Please help.I have a 3.90 gear with 27 inch tires.My motors cam seems to be done at 4800rpm.Comp cams says it's good until 5500 but when I run it out in 2nd gear to that the motor just goes flat.I lost .3 tenths over shifting at 4800.So I have went up to 29.5 tires.Going back to the track this weekend.Do you think it will improve my quarter mile time??? My next plan is to go down to a 3.55 gear and try the 27 inch tires with that gear.When I did the math these two combinations are almost identical in rpm to speed.With all of your expertise what do you think would be the best between these to set ups ?? My motor has a dual plane intake and about 300 hp.C6 transmission and the truck weigh is 4,000 with driver.I have traction bars and hook up good on take off with the 27 inch tires.
I have noticed that I get 300 more rpm on launch with the 29.5 tires.
Can't wait until Saturday to try again.
Please respond if possible, really like your video's.
I will respond to you soon. I wanna take time to study what you’ve said and think about it. I’ll get back to you as soon as I can
First of all I would never claim to be an expert, but thank you for the compliment. 😂😂.
There are obviously a huge number of variables that are going to make it difficult to answer this without asking 1 million questions.
So let’s just begin some generalities.
In general, larger tires are needed with deeper gears so that you have more contact patch on the track so it can hook. And you definitely are thinking correctly about balancing gear ratio and tire size.
I will be very curious to see what happens with the bigger tire and your 390 year, although it sounds like you’re hooking good with the 27’s. My fear is that going to the taller tire is actually going to make the problem worse. Because in essence you are going to a little bit higher gear by increasing tire size, it’s going to increase the load on the engine especially in second and third gear.
But that’s OK because that’s another bit of information that’s important
If your motor pulls good over 4800 in first gear but does not in second gear, I’m wondering if maybe you either have a timing or a fuel issue. Remember that the load on the engine is a lot harder in second gear so it’s going to demand more fuel and more spark over a longer period of time. My guess is that you are not near that RPM when you’re going through the traps so you don’t notice it in third gear.
Can you tell me a little bit more about exactly what engine you are running, what carburetor, and what your overall timing is at full advance?
@@MyKARSShop My overall timing is 34 degrees.I have a 750 quick fuel carb with vacuum secondary.I have the secondary adjusted to open up quickly.I have 68 jets in the front and 74 in the back.Plugs look ok .My cam is 219/219 at.050.Gross valve lift is.456. I have gt40 heads long tube headers.I have a stock torque converter.358 windsor bored .40 over.Just rebuilt c6 with shift kit and upgraded servo.
@@stevecooper8121 All right. Good information. I wanna ponder that a little bit. stay tuned. 🤔
@@stevecooper8121 I pondered this all night and I keep coming back to the same conclusion. This is total speculation, and without looking at it myself obviously I can only take my best educated guess
Everything sounds pretty straightforward on your build. We know the issue is not with the converter because you’re not bogging or anything coming out of the hole. Your issue is in second gear if you push it past 4500, you lose TIme.
Sounds like you’re launching fine and hooking good.
I suspect going to the taller tire is actually going to make the problem worse & you’ll lose more time. Again I could be totally wrong. But all I can do is take a guesstimate based on the information you’ve given
I did a quick calculation And the 750 carburetor is just a little much for that engine. However that is not a big deal since it is a vacuum secondary. It can be dialed in
In first gear, it is likely the secondaries and are not having as big an affect as they would in second gear. After all you’re not in first gear that long and the vacuum secondaries are a little bit slower to react than mechanicals.
But in second gear, the vacuum signal lasts longer and is pulling those secondaries open longer. It may be just enough to hurt your ETA without actually sooting up the plugs or blowing black smoke. My guess is you’re not hitting over 4500 RPM in third gear before you’re at the traps. If you were the problem would likely reoccur
I would try setting the secondaries to come in a later. And see what that does to your time.
Another thing I might look at is the advance curve in the distributor. But instincts tell me it’s a fueling issue.
Obviously very hard be definitive without seeing, hearing it and experiencing it myself.
Hope that helps, even if it’s just to solidify in your own mind what you are thinking the problem is. Let me know if there’s any other way I can help.
Mike
I need to go measure my tire diameter. The only thing I haven't replaced is the rear end. Why stop now?
RAWK ON!
Hotrods. An endless series of upgrades. Lol