someone mind telling me their mph @ 3krpm w/ r-154 and 3.73

[Insidious Surmiser]

I've been trying to get my gauges set right. my tach was off when I got the car (some asshole put crinkled white gauge faces in the car) but I can't remember what speeds you hit at 3krpm in each gear (r154 and 3.73) I'd really appreciate any help.

 

[Nick M]

RPM = (MPH x 336 x Gear Ratio x Diff Ratio) ÷ Tire Circumfrence

 

[PaulDoug]

Do you have a GPS? My speed cable snapped so I been using my GPS to show me my speed, works real good and is vary accurate.

 

[Nick M]

There is also a gear ratio chart floating around somewhere that is close enough.

 

[Insidious Surmiser]

hm... lets see what I can figure out... I was just wanting bone stock figures. I USED to know my car so well that when my speedo broke I just shrugged it off... I knew how fast I was going at any given time. that was in 07 before my car was stolen... I know for a FACT that my car would hit 80mph on the dot at 3k rpms in 5th

but really? no one knows off the top of their head, or just from driving their supra around today w/ sawblades or stock 5 stars?

alright... I found a handy dandy calculator here... I posted the thread right before I bolted off to work and had no time to search.

http://www.ccsupras.com/tech/speedrpm.php?action=calc

 

[Nick M]

I know for a FACT that my car would hit 80mph on the dot at 3k rpms in 5th

Then what are you asking for?

I found a handy dandy calculator here...

Or you could give elementary math a try. Either way.

 

[Backlash2032]

Then what are you asking for?



Or you could give elementary math a try. Either way.

Personally, I didn't know how to calculate rpm given gear ratios and tire diameter in 3rd grade..

Sent from my terrible HTC Rezound using Tapatalk. Don't buy HTC...

 

[Dan_Gyoba]

Well, you could take the knowns and calculate easy enough.

R154 5th gear is a 0.75 ratio. The rear end gears are given at 3.727:1. The tire diameter is 24.86", and engine RPM is 3000.

3000 RPM is 180,000 revolutions per hour at the crank.
0.75:1 ratio through the R154 gives the driveshaft 240,000 revolutions per hour
3.727:1 differential ratio gives the axles 64,390 revolutions per hour
The tire diameter of 24.86" gives a distance of 78.10" per revolution
That means that the car travels 5,028,835 inches per hour
63,360 inches is one mile
comes about 79.24 mph, but we'll call it 80.

Repeat calculations, replacing the 0.75 with 1.00, 1.31, 1.96, and 3.25 gives 60, 46, 31 and 18mph.

 

[Backlash2032]

Wouldn't you use tire circumference and not diameter though?

Sent from my terrible HTC Rezound using Tapatalk. Don't buy HTC...

 

[Nick M]

Wouldn't you use tire circumference and not diameter though?

Typo. 24.9 is the circumfrence.

 

[Dan_Gyoba]

No, 24.89" is the diameter. I multiplied it out to a circumference of 78.10"

 

[Insidious Surmiser]

Then what are you asking for?



Or you could give elementary math a try. Either way.

yeah, fooling around with elementary math would've taken more time, sure it would have been no issue figuring out, but if I only have a few spare minutes, wouldn't it be easier if someone was able to just tell me off the top of their head? if I don't have time to work the math out, I don't have the time, sorry that irritates you so much.

I was very specific in asking what each gear hit in mph at 3k rpms 5th gear IS NOT EVERY GEAR

are you having some confusion on the definition of an elementary english word "each"?

 

[Dan_Gyoba]

Repeat calculations, replacing the 0.75 with 1.00, 1.31, 1.96, and 3.25 gives 60, 46, 31 and 18mph.

If that wasn't clear enough...
3000 RPM
1st gear: 18mph
2nd gear: 31mph
3rd gear: 46mph
4th gear: 60mph
5th gear: 80mph.

If you know one gear, then the change in the gear ratios will give you the change in speed.

 

[Nick M]

yeah, fooling around with elementary math would've taken more time

As long as you don't have to do it yourself, right? Give him the shirt off somebody else's back.

if I don't have time to work the math out, I don't have the time, sorry that irritates you so much.

It doesn't irritate me. If fact, it is largely meaningless. I do tilt my head sometimes on this board over the nonsense that is posted.

I was very specific in asking what each gear hit in mph at 3k rpms

No shit. And I showed you how to figure it up in less than 2 minutes.

 

[Backlash2032]

You have enough time to get on the board, post several times, complain about how little time you have, but you don't have the time to Google "R154 gear ratios", and plug them into a gear ratio calculator? Lol...

Sent from my terrible HTC Rezound using Tapatalk. Don't buy HTC...

 

[grimreaper]

You have enough time to get on the board, post several times, complain about how little time you have, but you don't have the time to Google "R154 gear ratios", and plug them into a gear ratio calculator? Lol...

Sent from my terrible HTC Rezound using Tapatalk. Don't buy HTC...

i 2nd this

 

[jetjock]

Must be that "I'm a genius" thing he mentioned a while back...

 

[Insidious Surmiser]

jesus christ... get over it guys.

I get where yall are coming from, but seriously, the assumptions, jumping to conclusions, and finger pointing are just flat out unnecessary and quite frankly immature.

and yes JJ if you go look up the technical definition of genious, I do fall in that category, although, if you had any clue what-so-ever, you'd know a lot of geniuses have at least 1 or 2 screws loose.

anyhow... from what I figured, for NORMAL city driving, shift points go something like 20,30,45,60 (pretty close anyhow)

You have enough time to get on the board, post several times, complain about how little time you have, but you don't have the time to Google "R154 gear ratios", and plug them into a gear ratio calculator? Lol...

Sent from my terrible HTC Rezound using Tapatalk. Don't buy HTC...

seriously? that's what I did... DAYS ago... that's all I really had time for... I havnt had time to work on my car, let alone drive it, apart from putting a new dipstick in it jesus... I'm not THAT lazy OR helpless, you guys really do have an extremely poor opinion of me.

I posted the calculator with the calculations, although I see the calculations don't show... in any case I thought you guys would've figured I had used the calculator to get my answers (which I did) but instead people are still posting in this thread that I figured would have surely died by now.

 

[SC61 MK3]

and yes JJ if you go look up the technical definition of genious, I do fall in that category

1. Genious
It is often the case that idiots describe themselves as 'genious' but are ironically ignorant to the fact that the word is spelt 'genius' - much to the amusement of us intelligent people.
"Like, woah, yeah man, I'm like, such a genious, dude!"
"Well, you're retarded..."

 

[super51fan]

Why not just fix the speedo. My lower cable broke last monday. Part was $16 plus tax and was fixed on wednesdy. Yours may or may not just be the lower cable. But the more things you put off fixing the sooner the car gets to being a pos. Plus it cost alot more fixing 10 things than 1 thing.