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| gearing for turbo https://mail.slantsix.org/forum/viewtopic.php?t=42788 |
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| Author: | turboram [ Sun Dec 05, 2010 8:41 am ] |
| Post subject: | gearing for turbo |
Ok this may start an argument but what is the best way to setup a turbo motor? Should one use a 4 speed od with a higher gear for a better launch or a 3 speed with a lower gear to keep the motor lugging as turbo motors love? There are arguments ether way. Because the od with high numeric gear will have a Better 60ft which cuts down et but may not load the turbo as much and will lose mph and have more weight as well as spinning mass .I am using auto trans ether way. any help would be appreciated. Thanks Nick |
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| Author: | VG-265 [ Sun Dec 05, 2010 2:59 pm ] |
| Post subject: | |
Not a slant, and no time slips, just "feel". A GM Holden 202 six with a turbo really liked going from the standard 3.36 gears to 3.08. Seemed like it was better everywhere. I would have liked to try 2.78 gears, but the guy paying the bills was happy with the 3.08s. |
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| Author: | Shaker223 [ Sun Dec 05, 2010 4:11 pm ] |
| Post subject: | |
I'm using a 2.76 gear and 27" tall tires. The 904 trans has a low gear set in it. Leaving with 8psi I managed 1.57 60' times. Next year, I'm shooting for 1.4x by leaving with more boost. I can make the torque convertor stall at just about any RPM I want while footbraking. |
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| Author: | 75duster [ Sun Dec 05, 2010 10:59 pm ] |
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dont know about a slant, but the 4cyl turbo dodge cars like my 86 charger have a slightly higher gear than the non turbo, supposedly to help them spool quicker |
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| Author: | Sam Powell [ Sun Dec 12, 2010 5:07 am ] |
| Post subject: | |
I have the T-5 with the lowest possible 1st gear, and a 2.74 rear (I think). This gives it almost a 12:1 first gear final ratio, which seems to be too low for the turbo to provide the most advantage, even though it is running good boost right away in ffirst. There is no discernible lag. . Although it is a little hard to tell launching peg leg at this point. My 60 foot times were 2.6ish which is partly due to wheel slip,and partly just bad driving on my part. The sure grip is going in next week. All that being said, it seems the turbo starts to work to better advantage when it gets into 2nd gear. However, second is a little too high to start out in. Something between the two would be probably ideal. From the reading I have done, there is no one answer to the OP's question. It is so dependent upon tire size, final drive ratio, traction, car weight, engine cubes, compression ratio, exhaust size, and sizing of both parts of the turbo, etc. etc. . There are many ways to skin this cat. The simplest generality, which has limited use, is that turbos seem to be more for torque than RPM. But, you need RPM to get the things spinning. Sam |
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| Author: | Charrlie_S [ Sun Dec 12, 2010 6:21 am ] |
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Quote: dont know about a slant, but the 4cyl turbo dodge cars like my 86 charger have a slightly higher gear than the non turbo, supposedly to help them spool quicker
I don't think it is to help the turbo spool faster. More then likely, since the turbo motor puts out more torque/power, the taller gear is to improve economy, and still be quicker then the NA motor. Just like a six cyl car will normally have a shorter rear gear the the same car with a v-8.
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| Author: | 1974duster kev [ Sun Dec 12, 2010 3:36 pm ] |
| Post subject: | |
I'm running 3.73's right now and still plan on running them with the turbo motor it's a street car and i plan on putting a t56 behind it shortly down the road anyway so i think the 6 speed will have plenty of gears to not run out of steam. Those quicktime bell housing out yet? Tom, and Ryan have timeslips to prove the stock gear worked better for them et and mph wise but they both run auto's so i think I'd rather have the 3.73 to help me off the line with the 4 spd, the od gear spacing loads the motor now so i'm sure it will spool the turbo pretty good. Kev |
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| Author: | turboram [ Mon Dec 13, 2010 5:28 pm ] |
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Thanks for the imput im still not shure what ill do. if things get better ill keep the valiant and race it! what I have is a dana 60 with 4.56 gears the proper gearing for a 3 speed is 3:08 and the lowest gear that can be installed is 3:55 and the rear end is already set up with ladder bars so changing is will be a pain in the rear end (pun intended) |
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