So to sum up, if I understand correctly, with my 340 and crank register of 1.58"ish, I can use the early version of the lockup trans(which I have) as long as I'm using a lockup converter??
Another question....is my trans a 3 spd?
Thanks
If it has a high stall, and you had the right rear gear, you could conceivably refer to an A999 as a 4.5 speed, that is;
a continuously variable convertor, with a ratio up to about 2:1
plus three gears in the case,
plus a half-gear in the lock-up.
The nice thing about a convertor, is that it is always available to be a gear-splitter between every gear.
What I mean is; say yur cruising along in second gear at 35=2000, and you want to speed up.
Ok well to do 35 at 2000, you would have have 3.23 gears
let's say you have a 2800 convertor.
so you step on it, and the rpm rises up to 2800, the convertor locks in, and yur motoring ahead at IDK say plus 20 hp. and the trans has not even downshifted!.
Now see, that's 800rpm you gained right there.
Had the trans downshifted with a 2000 stall, the rpm would have jumped to 3800, and the stock 340 is right on point, ready to race. But you didn't want that, you just wanted to speed up a lil.
So then, the 2800 stall, in this case, is acting like a half a gear.
Now, if yur looking to drop cruise rpm for a long-distance tour, the effectiveness of a lock-up is gonna depend a lot on your current gears, and the torque of the engine.
Lets assume you have 3.23s and the convertor is a 2400 LU.
In this case 65 would be 2615 at zero slip,/same as lockup. But lets say your car does not require much power to be motored at 65, so in non-LU, the rpm actually slips down to 2500.
So which combo will sip less fuel? My money is on the slipping 2500.
IMO
that's the wrong way to use a LU trans.
Lets say your current trans is a regular A904, no LU, and it has a 2200TC. and still with 3.23s. Ok so 65 is calculated to be 2616 @zero slip, and yur convertor is cruising along at 2500 just like the first example.
Your starter gear, using a factor of 1.8 at Wot, means you will be launching at an equivalent ratio of 20/1, and by the time you run out of rpm, the convertor is down to say 1.4, so the equivalent ratio is 11/1..
Now, lets convert that to ftlbs. Lets say your 340 puts out 200ftlbs at @ 2000, so then, you are launching at up to 200 x 20/1= 4000 ftlbs, and the tires are on fire.
Now lets to the same exercise with 2.76 gears, an A999 low gear of 2.54, and a 2800stall/ LU convertor.
Firstly, 65 =2230 in LU; pretty sweet compared to 2615.
Now for your starter gear;
2.76 x 2 54 x 1.8= an instantaneous ratio of 12.62, which is excellent.
Now, lets say at 2800, your 340 kicks out 20% more torqe, so she's at 240 ftlbs, so to the road is 240 x 12.62=3030. ... and the tires are still spinning enough to get you to where the power is, so off you go.
Please understand, I picked these torque numbers out of a hat, just for illustration.
That's how you use the A999 LU 2800 Tc.... IMO
Finally, your fuel economy, is estimated to get better by half the percentage in rpm decrease. So from 2615 to 2230 is a drop of 14.7 %, and half of that is 7.4% and that is the expected gain in mpg. But that does not take into account that with the A904, the trans was slipping, so that is an additional economy gain. Lets throw in a token .1%, and the savings becomes 7.5%
Say the 340 was getting 15 mpgs with the A904/3.23s. Swapping to the A999/2.76s is estimated to gain you 7.5%, so that comes to 1.12 mpg.
That's gonna save you .46 USg gallons per 100 miles. in liters that is 1.7 liters. or $2.50C, this week, lol. And 1000 miles times two, saves you $50C if I got my math right......., which at 2AM I can't be sure of lol.
Ok here's the point, if your Cruize-timing is off several degrees, as is typical, that will cost you more money.
Lets say going from 2615 to 2230 you really get out of the timing groove, and you break even at 15mpg. Now you've done all this work, and spent all this time, and bought a convertor and you didn't save nuttin' in mpgs. Boy that would sure frost my acorns.
Ok lets say your cruize-timing at 2515, is 26 total mechanical plus a typical 12* more in the VA, for a total of 38* . That is not nearly enough for steady-state long-distance cruising. More than likely the 340 will want 56 or more degrees for best fuel economy so, 38* is severely retarded. I mean IDK what your numbers are but you get the idea. That's gonna cost you way more than all that swapping chit around might.
So how can you figure your best cruize-timing?
Answer; well IDK, but I can tell you how I do it.
First you gotta know what rpm you are gonna cruize at.
Then, just rev it up to that rpm, and tug on the distributor. When the rpm goes up, you bring it back down, then add more timing. Repeat until, more timing does Not produce more rpm.
Next, install your timing lite, rev it up to cruze rpm, and read the balancer. Subtract 3 degrees for lack of load, and that is your target Cruize-Timing
Now you just gotta figure out how to make your distributor spit it out.
If you change your Cruize rpm, then yur gonna have to repeat finding the target at the new rpm.
I always drop 3 degrees to compensate for lack of load. That's done me well. I have a dash-mounted, adjustable, timing module, that I can fine tune as I drive.
After you get the timing right, you can lean the crap out of the carb until the engine complains, then give a lil back. You'll be working on the transfers probably cuz you may not yet be on the mains. This is the time that a tiny-Primary Spreadbore comes in handy, cuz it may get up on the mains making tuning way easier.
IDK, I have a hi-compression 367, that cruizes at 2240, so it's barely open at 65, I gotta do all kinds of tricks get fuel economy off the transfers..
Anyway, I gotta get some sleep, it's 2:30AM here. TTYL
