|
03-30-2014, 09:13 PM | #11 |
Senior Member
Join Date: Mar 2006
Posts: 958
Likes: 618
Liked 165 Times in 60 Posts
|
Re: Ordering New Transmission, but What Gears ?
The statement on what is considered a good SLR being 9,10, or 11 for the Walace Racing calculator might be fine for automatics but is completely wrong for a stick car. We do not have a torque multiplier. So our SLR will be higher. Sorry I did not elaborate on SLR earlier.
So what clutch did you get? The dual 7" is very user friendly and extremely predictable. Sean
__________________
Sean Marconette 84 Mustang 5060 SS/N Last edited by Sean Marconette; 03-30-2014 at 09:17 PM. |
03-30-2014, 09:35 PM | #12 |
Member
|
Re: Ordering New Transmission, but What Gears ?
No, not quite that exotic, Sean. Still just single disk. Rob set it up so it has a "soft hit".
__________________
Aubrey N Bruneau 6409 C/S 62 BelAir sport coupe, 409 HP 409 Last edited by Aubrey N Bruneau; 03-30-2014 at 11:01 PM. |
03-30-2014, 10:15 PM | #13 |
Member
Join Date: Oct 2006
Posts: 177
Likes: 0
Liked 1 Time in 1 Post
|
Re: Ordering New Transmission, but What Gears ?
You also have to look at the strongest column with regard to gear selection. We have a 3.08 Jerico in our Vette, but the car is light at 3000 pounds . The old Doug Nash was a 3.25. I would try to talk to Richard Feldman if possible. I don't know him but hes been at it for a long time with the big car and stick. Good luck my friend.
|
03-31-2014, 01:49 AM | #14 |
VIP Member
Join Date: Dec 2001
Location: Texarkana Ark/TX
Posts: 2,348
Likes: 434
Liked 677 Times in 261 Posts
|
Re: Ordering New Transmission, but What Gears ?
Aubrey a little math:
3.19 1st gear to a 1.91 second is a 40% drop 7,000 - 40% =drop to 4,200 3.08 1st gear to a 1.91 second is a 38% drop 7,000-38% = drop to 4,340 after you get past the first gear: 1.91 second to a 1.32 3rd is a 30% drop 7,000 - 30% =drop to 4,900 1.32 3rd to a1 to 1 is a 24% drop 7,000-24% = drop to 5,320 you always want the % drop less as the gears go up. The 1.91 may have just a little too much drop with either the 3.19 or the 3.08 with your high torque engine it migh not. Either way I would try to work it from peak Tq to peak HP since it is not an RPM combination. This ain't your Dad's Small Block Chevy! That low gear will have to be determined by testing just how much "Hook" you really have. When I ran a stick I kept 2 low gear ratios and 2 different weight flywheels to tune to track conditions and available "Hook" Keep in mind that if you are crossing too high at the finish line you can always take a little rear gear out and add the starting line ratio back with low gear in the tranny. More Math: pick your poison! 2.83 X 5.13 = 14.52 That you had trouble hooking @ 6,200 leave 3.19 X 5.13 = 16.37 Proably too low leaving at a high RPM 3.08 X 5.13 = 15.80 leave at just above peak Tq 4,300 3.19 X 4.88= 15.57 3.08 X 4.88 = 15.03 That is the beauty of using a stick. You can vary the leave RPM, clutch and gearing combos and do like Todd said, Drive it off the line!! just my .02 for free! Good luck.
__________________
Adger Smith (Former SS) Last edited by Adger Smith; 03-31-2014 at 02:07 AM. Reason: sp |
03-31-2014, 07:38 AM | #15 |
Member
Join Date: Sep 2006
Location: Moncton, N.B.
Posts: 276
Likes: 24
Liked 24 Times in 13 Posts
|
Re: Ordering New Transmission, but What Gears ?
I don't want to steal the thread but; I have always done(and read) finish line RPM,shift RPM and launch RPM calculations off of engine max HP not max torque.
May be I've been looking at this wrong!? |
03-31-2014, 09:22 AM | #16 |
VIP Member
Join Date: Dec 2001
Location: Texarkana Ark/TX
Posts: 2,348
Likes: 434
Liked 677 Times in 261 Posts
|
Re: Ordering New Transmission, but What Gears ?
Terry,
You are right, but he has no real RPM HP he has a torque engine. A 409 will not RPM like a SBC. You have to "work" the engine differently. If you have ever seen a 409 piston and pin you don't want to RPM one of those. Just the sheer weight will take things apart. Right Aubrey? I feel 7,000 is really pushing it. BTY you aren't stealing the thread, you are adding to the discussion.. :~) If I was gearing a good RPM engine I would go for 8-10% RPM over peak Hp as a shift point and then figure the % gear pull back based on that to keep the engine right around peak HP. I would also work the ratios to get it in high gear somewhere around the 330' on the track. Sean added a good point about stick cars not having the TQ multiplier of a TQ converter. The old rule of thumb that we used was add at least 20% to the low gear ratio of a stick over an automatic. My 330 ft mark may be a little early for a stick, but a good automatic will respond to that. It would be interesting to watch a stick Comp car with about the same power to weight ratio as he has and see where it goes to high. On second thought that may not be the real deal because most all Comp cars are 5 speeds. Hummm, might be interesting just to watch!! :~)
__________________
Adger Smith (Former SS) Last edited by Adger Smith; 03-31-2014 at 09:38 AM. Reason: SP & add |
03-31-2014, 09:42 AM | #17 |
Member
|
Re: Ordering New Transmission, but What Gears ?
Thanks Adger. No, Terry, you're not stealing the thread.
Just looked at my old dyno chart. Same cam, using stock stamped rockers. Here's what I have: ( stupid printout wasn't legible in places... or maybe I'm over 50 ? ) 4000 450 350 4100 465 361 4200 467 373 4300 473 384 4400 475 398 4500 481 410 4600 479 420 4700 482 429 4800 479 438 4900 479 444 5000 478 456 5100 477 461 5200 477 472 5300 477 478 5400 476 481 5500 465 485 5600 461 491 5700 459 495 5800 446 493 5900 443 496 6000 437 500 6100 439 508 6200 429 507 6300 423 505 6400 419 511 6500 ??? 512.6 6600 407 510 6700 ??? 509 6800 384 501 6900 ??? 497 7000 372 497 7100 ??? 490 7200 357 486 You're right, need to be careful about RPM, but Adger, the failures have never been pistons !... it's the damn "super duper" race car parts on the uncontrollable intake lobe... shattering retainers ! Have a toned down intake lobe now. I've used the "average horsepower" system.
__________________
Aubrey N Bruneau 6409 C/S 62 BelAir sport coupe, 409 HP 409 |
03-31-2014, 09:55 AM | #18 |
Senior Member
Join Date: Sep 2007
Posts: 574
Likes: 6
Liked 44 Times in 22 Posts
|
Re: Ordering New Transmission, but What Gears ?
Scott at Jerico talked me into 3.08 first (1.93, 1.34, 1.00) and said it could be changed to about 3.19 later if needed. His argument was that I would have no time in first with 3.19. I have found with the right clutch slippage, I am OK, but still wonder if 3.19 would be better. If I do decide to change, I will discuss gear strengths with Scott.
I also have a torque type engine that I don't want to over-rev and gear the diff for the top end, then take what I can get in terms of first gear. |
03-31-2014, 10:35 AM | #19 |
VIP Member
Join Date: Dec 2001
Location: Texarkana Ark/TX
Posts: 2,348
Likes: 434
Liked 677 Times in 261 Posts
|
Re: Ordering New Transmission, but What Gears ?
Aubrey,
I think the 3.19 is too steep a gear for you combination. It will have too much 1-2 drop and with the 5.13 rear gear you have you will never hook it. IF I tried it I would use 4.88's in the rear. I think you have the shift point just about right. You might want to pull it 200 early in low to second with all that new gear ratio. then string it out in 2-3 & 3-4. One thing about it is all the thinking and planning needs to be verified by testing. Do Not shove what you want at the car. Let the car tell you what it wants.
__________________
Adger Smith (Former SS) |
03-31-2014, 11:52 AM | #20 |
Member
Join Date: Jul 2006
Location: Kansas City
Posts: 397
Likes: 104
Liked 106 Times in 33 Posts
|
Re: Ordering New Transmission, but What Gears ?
Lots of good information, give us an update when you do some testing.
|
|
|