My Speedster is suposed to have 3.88:1 gears. How many rpms should it be turning at 70 mph? Thanks, Bill
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My Speedster is suposed to have 3.88:1 gears. How many rpms should it be turning at 70 mph? Thanks, Bill
hi Bill;
That will depend on the tire size youre running, there are many gear ratio calculators out there you can use. This topic has been covered extensively on this forum, do a search on the subject and youll find your way - cheers jJ
That will depend on the tire size youre running, there are many gear ratio calculators out there you can use. This topic has been covered extensively on this forum, do a search on the subject and youll find your way - cheers jJ
somewhere around 3,250 (with 205X16's on front, 225X16's on rear)
www.actionimport.com/Tech_Files/gear_ratio_computer.htm
This should get you started.
This should get you started.
With that ring and pinion: rough guess that usually works, considering that you've probably got pretty much stock height tires stuffed under the tight confines of the little 356 tub . . .
Your MPH is twice the RPM.
At 3500 RPM you're doing 70 MPH.
At 2000 RPM, you're doing 40 MPH.
And so on, of course, you have to be in fourth gear for this to work.
Your MPH is twice the RPM.
At 3500 RPM you're doing 70 MPH.
At 2000 RPM, you're doing 40 MPH.
And so on, of course, you have to be in fourth gear for this to work.
This subject really confuses the heck out of me. I hate math!! Having low profile tires(225/50's) screws up speedo readings and my r/p ratio is probably not the best compatible set up either. My stroker has pretty good torque and I'm not sure it's being all it can be. I've been working on the gear ratio computer to see if I can improve anything. Is stock tire height 25" or 25.4"? The 225's have a 23.9" tire height.My feeling is since the tires are smaller, the engine spins faster to cover the same distance as stock tires. Hence, I think I should drop down to 3.88 or even 3.44 to compensate??
BD
BD
This topic has been discussed at length several times before, I'd recommend doing a site search on this topic. I've got a lot of data gathered concerning available gear ratio combinations to tailor the 4 speed VW transaxle to the available power band of the motor. It is possible to get this perfect without resorting to a 5 speed, but it will require some aftermarket gears.
Firstly, the stock R/P for a Beetle is 4.12- the 3.88s were stock on Type 3s I believe. When you order a "standard" transaxle, the gear ratios are: 3.78 first, 2.06 second, 1.26 third, and .89 fourth. There are two different ways to get a "freeway flier"- one is with a .82 fourth and the standard 4.12 R/P, the second is with a standard gearset and a 3.88 R/P.
For a 1776/1914, the 3.88 with the stock gearset is a decent choice. However, there are some generalizations that can made. Firstly, first gear is way too tall for anything other than full-on drag racing. Secondly, the spacing between third and fourth is too close. These ratios were compromises that VW made to compensate for the fact that the original engines were underpowered- the tall first was get the car rolling with an engine with no torque, and the close 3rd/4th was because the engine wouldn't pull the car up a hill in 4th.
A speedster is quite a bit lighter than a Beetle, and has shorter tires generally. In addition, almost all of us run something bigger than a stock 1600. All this works together to make the gear selections frustrating, and poorly spaced. What good is that 2110, if the power doesn't make it to the ground in an optimal manner?
A bigger engine will need some custom gears to make driving the car a good experience. It will also require the "pro-street" treatment that was outlined above. $1500 will get you pretty much everything you could want- custom ratios, hardened keys, welded gears, heavy duty diff and side plate.... everything. Less will be a compromise.
Bill- When you use the calculator, its good to know where your engine is making power. I don't know what you've got, but shifting at 5000 rpm, and dropping to 3000-3500 rpm would be about optimal. This keeps you in the heart of the power band for most larger engines. You can calculate where exactly that is by plotting how fast you are going in any ratio at a given RPM, and then finding that same speed in the next gear- that will be the RPM drop on the shift, because the car will be moving that speed when you shift.
With even shorter tires than the 165/65s most of us "classic" guys are running, I can imagine your gearset is too tall. I'd definately do something- the 3.88 with the stock gears would be a start, and it's cheap. More money gets you better spacing- call Rancho and get a catalog (they're free).
As far as your speedometer problem, one of the speedometer shops in CA will be able to fix that for you. Good luck.
Firstly, the stock R/P for a Beetle is 4.12- the 3.88s were stock on Type 3s I believe. When you order a "standard" transaxle, the gear ratios are: 3.78 first, 2.06 second, 1.26 third, and .89 fourth. There are two different ways to get a "freeway flier"- one is with a .82 fourth and the standard 4.12 R/P, the second is with a standard gearset and a 3.88 R/P.
For a 1776/1914, the 3.88 with the stock gearset is a decent choice. However, there are some generalizations that can made. Firstly, first gear is way too tall for anything other than full-on drag racing. Secondly, the spacing between third and fourth is too close. These ratios were compromises that VW made to compensate for the fact that the original engines were underpowered- the tall first was get the car rolling with an engine with no torque, and the close 3rd/4th was because the engine wouldn't pull the car up a hill in 4th.
A speedster is quite a bit lighter than a Beetle, and has shorter tires generally. In addition, almost all of us run something bigger than a stock 1600. All this works together to make the gear selections frustrating, and poorly spaced. What good is that 2110, if the power doesn't make it to the ground in an optimal manner?
A bigger engine will need some custom gears to make driving the car a good experience. It will also require the "pro-street" treatment that was outlined above. $1500 will get you pretty much everything you could want- custom ratios, hardened keys, welded gears, heavy duty diff and side plate.... everything. Less will be a compromise.
Bill- When you use the calculator, its good to know where your engine is making power. I don't know what you've got, but shifting at 5000 rpm, and dropping to 3000-3500 rpm would be about optimal. This keeps you in the heart of the power band for most larger engines. You can calculate where exactly that is by plotting how fast you are going in any ratio at a given RPM, and then finding that same speed in the next gear- that will be the RPM drop on the shift, because the car will be moving that speed when you shift.
With even shorter tires than the 165/65s most of us "classic" guys are running, I can imagine your gearset is too tall. I'd definately do something- the 3.88 with the stock gears would be a start, and it's cheap. More money gets you better spacing- call Rancho and get a catalog (they're free).
As far as your speedometer problem, one of the speedometer shops in CA will be able to fix that for you. Good luck.
Stan: Thanx for the input. I don't know much about the engine except it was "built" up a bit. I do know it has an 88mm stroke and assuming at least stock bores makes it around 2L or so. Only an autopsy will reveal what else is inside(but I really don't want to go there). I was told it had a "mild" cam also. I have searched some, but nothing was comparable with my tire heights, just stock. I found thru one search a 3rd gear ratio of 1.58 and .82 fourth. I'll have to rerun the numbers with the 1.26 3rd gear and .89 4th. I usually run it up to 4k or so, but when feeling frisky will go up to 5500 on occasion only. It does hop between 3k and 5k It'll pull from 2500 not to bad also.
BD
BD