guys with 20+" rims
10-05-2009, 09:35 PM
#13
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has any one run a turbo set up with lower gears? yea i know taller gears help load the turbo but these trucks are heavy turds to begin with. i tried to get danny to experiment on his turbo set up. if a guy can cut a 1.7-1.8 60ft with a 3k stall and 4.10s, even with a turbo truck with the same stall and same 4.30s while building boost off the line shouldnt he be able to cut the same if not better 60ft..just throwing ideas.. id just like to see some one experiment once..
10-05-2009, 09:42 PM
#15
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lol i have 4.10, but they were a previous mod. I also have the 80e with a dead first gear.
Spoolin highly recommended the 3.73's over the 4.10 for loading the turbo. I agree that the lower gear you can get away with the better. but i dunno
Spoolin highly recommended the 3.73's over the 4.10 for loading the turbo. I agree that the lower gear you can get away with the better. but i dunno
10-05-2009, 10:15 PM
#17
I'm running 285/50-20's (31"), and I have the factory 3.73's. It's great on the highway...can't remember what I cruise at when I'm doing 65-75, but IIRC it's less than 2k at 65 and just at 2kish at 75...can't remember, haven't driven my truck in almost a year.
With that being said, I wish I had 4.10's for that extra dig off the line and around town. I figure if the SS's came with 4.10's from the factory, and about a 32" tire, that it would be perfect for my setup. As it is, I have a nice "touring" truck lol...when it moves ha ha.
With that being said, I wish I had 4.10's for that extra dig off the line and around town. I figure if the SS's came with 4.10's from the factory, and about a 32" tire, that it would be perfect for my setup. As it is, I have a nice "touring" truck lol...when it moves ha ha.
10-05-2009, 11:16 PM
#18
what do you guys think of this?
Think about this for a sec. Exhaust energy (enthalpy) and mass flow are what spool up a turbo.
The energy is a function of temperature. EGT is the same at low rpm and high rpm, so the gear doesn't affect it.
Mass flow is a function of rpm and throttle angle. You get more mass flow at higher rpm. So, the sooner you can get an engine to a high rpm, the more mass flow you're going to supply to the turbo, the quicker it will spool up. I used to have a sloppy-loose torque converter in my car. The turbo spooled up really quick because the converter allowed the engine to reach 4000 rpm as soon as you hit it. Of course, with boost it would blow right through it, but that's a topic for another day. . .
Taller gears may SEEM like you get boost sooner, but it's only because you get it at an earlier rpm, not in less time. Heck, if you have a 6-spd and start out in 6th gear, you might get boost at 2000 rpm, but you're better off starting off in 1st and not getting boost until 4000 rpm. I assure you 4000 rpm in 1st will come sooner than 2000 in 6th.
The energy is a function of temperature. EGT is the same at low rpm and high rpm, so the gear doesn't affect it.
Mass flow is a function of rpm and throttle angle. You get more mass flow at higher rpm. So, the sooner you can get an engine to a high rpm, the more mass flow you're going to supply to the turbo, the quicker it will spool up. I used to have a sloppy-loose torque converter in my car. The turbo spooled up really quick because the converter allowed the engine to reach 4000 rpm as soon as you hit it. Of course, with boost it would blow right through it, but that's a topic for another day. . .
Taller gears may SEEM like you get boost sooner, but it's only because you get it at an earlier rpm, not in less time. Heck, if you have a 6-spd and start out in 6th gear, you might get boost at 2000 rpm, but you're better off starting off in 1st and not getting boost until 4000 rpm. I assure you 4000 rpm in 1st will come sooner than 2000 in 6th.
