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Re: Left Lane Cruiser!

 To: Les Myer Re: Left Lane Cruiser! Ulix Goettsch Mon, 9 Feb 1998 08:39:55 -0800 (PST) spridgets@Autox.Team.Net <3.0.5.32.19980208235300.007a87f0@pop.qtm.net> Ulix Goettsch owner-spridgets@Autox.Team.Net
 ```Les, of course you are right, I copied down the wrong number. Regarding your 100mph, old test articles say thet a stock 67 Sprite when it was new didn't make it to 100 mph. I think they said 95 or something like that. Of course that was a _stock_ Sprite... Ulix On Sun, 8 Feb 1998, Les Myer wrote: > Ulix, > > Wouldn't my car at 80 mph with 185s be: > > 4624 * (4.22/3.7) * .947 = 4994 rpm > > Then my car at 80 mph with 145s would be: > > 4624 * (4.22/3.7) * 1 = 5273 rpm > > hmmm.....not as big a difference as I thought. > > Interesting that at 100 mph with 4.22 and 185s, rpms would be: > > 4994 * 100/80 = 6242 rpm > > Guess I was spinning it right up there. > > Thanks for the data. > > Les > > At 07:26 PM 2/8/98 -0800, you wrote: > >Les, > >a 145-13 is 566mm in diameter, the 185/70-13 is 598mm > >Circumference is pi*diameter, so I can just divide 566/598=0.947 > >So you turn 95% as many rpm as with stock tires. > >Going from 4.22 to 3.9 is 3.9/4.22=.924 or 92.4% > > > >Now to get the rpm. > > > >17.3mph/1000rpm for a 3.7 with 145s > >1000/17.3 = 57.8 rpm/mph > >80mph * 57.8 = 4624rpm in a '79 Midget > > > >In your car: > >4624 * (4.22/3.7) * .924 = 4873rpm > > > >In my car: 3792rpm. > > > >I'll try my top speed after I rebuild the engine :-) > >I think I'll have to use 4th to get there though... > > > >Ulix > > > > > >On Sun, 8 Feb 1998, Les Myer wrote: > > > >> So how many RPMs am I turning with a 4.22 and 185/70R-13 tires during an > >> 80mph commute to work on I-94 (tach is off (reads 6500), but have > >> calculated MPH by the mile markers)? Really would like to know. You gotta > >> do 80 here in Michigan (70mph speed limit) to keep from getting run over by > >> the 18-wheelers going from Chicago to Detroit and vice versa. I cringed > >> every time until I put the bigger tires on and I think the bigger tires > >> look a lot better than the little skinnies I had before. I think they are a > >> viable option to swapping diffs. Plus, it softened the ride immensely. > >> The only things I don't like about them is the wheel hop I get when dumping > >> the clutch at RPM and I don't think it handles quite as well in the 30 mph > >> range. > >> > >> BTW, 80 is not the top end - have had PUDDLES briefly over 100mph with > >> these tires - kind of weird, the exhaust note seems to get much quieter at > >> very high rpm. I try to keep the cruising speed at 70-75 mph for > >> long-distance driving. > >> > >> Les > >> > >> At 10:13 AM 2/8/98 -0800, you wrote: > >> >I swapped out the 4.22 for a 3.7 rear end in my car, which is equipped > >> >with the 5-speed. Wow! It has transformed the character of the car on > >> >the highway. WIth the ribcase and 4.22, I felt completely out of place on > >> >the highway, the car felt like it was doing something it wasn't designed > >> >to do. I used to drive ~60mph. The combination of 3.7 and 5-speed lowers > >> >my rpm to 72% of original. At 4000 rpm, I go the same speed that used to > >> >take 5500rpm, which according to me calculations should be 84mph. 74mph > >> >at 3500rpm. I ride the fast lane unstressed. (All numbers based on > >> >theory, not the inaccurate instruments of my car. rpm to mph conversion > >> >based on Haynes manual that says 17.3 mph/1000rpm in 1500 with 3.7 rear). > >> > > >> >Of course there are tradeoffs. Inclines on the highway will get > >> >me downshifting early, since the motor has less power at 3500 than at 4000 > >> >which is what I used to see at cruise. > >> >The long rear end makes for a long first gear which makes for harder > >> >takeoff from a stop. First gear on the Datsun trans is shorter than the > >> >one of the ribcase, which helps to offset this some. This shorter first, > >> >coupled with the 4.22 resulted in a very short first gear that is nice on > >> >steep hills, but is also too low to make any significant speed in the > >> >process on accelerating from a stoplight. I didn't notice this until now. > >> >Now, after taking off, there is rush of forward motion in 1st, that wasn't > >> >there. This is hard to explain, let me try again...if you take off on a > >> >mountain bike in the lowest gear it has, yes - it is very easy to take > >> >off, but this low gear doesn't get you to any useful speed before you have > >> >to upshift... > >> > > >> >I have yet to try taking off on an EXTREMELY steep hill in my > >> >neighborhood to test the difference in that respect. > >> > > >> >If you do a lot of highway cruising, I would recommend this combo (maybe > >> >not with a 948). > >> > > >> > Ulix __/__,__ > > >> >.......................................................... (_o____o_).... > >> > '67 Sprite > >> > > >> > > >> > > >> > > > > Ulix __/__,__ > >.......................................................... (_o____o_).... > > '67 Sprite > > > > > > > Ulix __/__,__ .......................................................... (_o____o_).... '67 Sprite ```
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