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Discussion Starter #1
forgive my low post count, long time member of modfords. making the move here since it is a ghost town over there..

put a hellion single turbo kit on my 01 2v with the 3650 a few months ago. currently running a 3.73 on 295/35/18's on 8psi, but trying to figure out if i want to go back to stock gear before i start cranking the boost up. car doesnt really start pulling boost until 2nd gear as of now, which may be a good thing for traction purposes.

interested in what others are running.

thanks!
 

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2V mod w/ 3.27's with 28' tall tire.

ks
 

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Currently have 3.73, 28" tire, but I'm built 4R. May be stepping down to 3.55 or 3.27 once I can finish it up
 

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Discussion Starter #5
strictly street, being a vert i would have to cage it or get thrown off the track on the first pass. I'm not one to launch the car hard or spin the tires on leave, i usually roll into it, especially now that i have to worry about smoking the trans or torque boxes.
 

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Currently I have a 3.73 with a 4v/ with Powerglide. Back when I had 2v w/ 3650 I ran a 3.55. When I had a 2v w/ th400 I ran a 3.27. All these combos were with a 28" tire.
 

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The gear someone else runs has nothing to do with the gear you need. The optimum gear is dependent on what you do with the car and a dozen other details.

Don't swallow the popular bologna about a turbo needing a tall gear to "spool".

If you primarily drag race the optimum gear is almost always the gear that puts you across the stripe at peak RPM, and obviously that would vary with maximum RPM, tire diameter, converter slip, and MPH. I run a 4.10 with 28 tires and trap at 7800. My car slows down and is harder to manage with a 3.73 or 3.55, and it goes too high RPM with a 4.56

If I ran mostly on the street with a engine that liked to be at 2K rpm, I would gear it to be 2K on the street at my common cruise speed for my converter and tire diameter. Mine works out to be about 2K RPM at 45 or so on 28's

Figure out what you want to do, including the tire size and cam, and then pick the gear for your combo.
 
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for a street car with a stockish size tire and a stock 3650, I'd go to a 3.08-3.27. For a track car, basically what Tom said above (optimum finish line RPM). On the street I prefer not to shift 4 times from 0-20mph and my stuff works well at low RPM on the highway. idk about 2v mod motors as much though. May like a tad more RPM on the highway.
 

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TomR put it best. I run Ford racing gears, my ratio isn't important. What is ideal for my car, may be less than ideal on yours.
 

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Discussion Starter #14
well im still torn between gears.. but now im wondering if i go ahead and crank the boost up and tune with the 3.73's, will i need to re-tune if i decide to go back to a 3.27 later? Im not talking about the obvious speedometer issue, but more so would the turbo load up differently throwing off the fuel mapping?
 

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well im still torn between gears.. but now im wondering if i go ahead and crank the boost up and tune with the 3.73's, will i need to re-tune if i decide to go back to a 3.27 later? Im not talking about the obvious speedometer issue, but more so would the turbo load up differently throwing off the fuel mapping?
The fuel in a proper system is based entirely on engine air flow. This is why mixture does not change off target mixture in a proper system when you shift gears.

Changing rear gears is significantly less different than just shifting a transmission. Why would anyone expect changing a rear gear 13-14% would require a "retune" when changing a transmission gear 30-70% does not?

Also, don't buy into that silly "load the turbo" to go faster folklore. While it is true an engine under load generates more exhaust and the extra exhaust can "spool" a large housing big turbine better, reducing the numeric gear ratio directly reduces wheel torque for a given crankshaft torque. You typically wind up with more "spool" on a large system with high load, but the reduction in ratio reduces torque more than the faster spool recovers.

With a static gate dome CO2 pressure of 18 psi and a 6 pound spring, my car makes 21 psi in low and 23 psi in high. That extra 2 psi after the shift is worth about 5% more torque. The gear ratio loss is from a 1.69 to a 1:1 or about 40% torque loss at the tires. Although the shift increases boost by increasing turbine pressure resulting in 5% more torque, the shift also reduces gear ratio. The reduced gear ratio causes a net torque reduction of 35%. Having more boost from "loading the engine" doesn't even come remotely close to undoing the loss caused by the gear change.

For racing I use as much gear ratio as possible unless the car doesn't have enough traction to use the extra gear, or unless more gear runs the engine out of RPM at the end.
 

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Discussion Starter #16
Awesome, Thanks Tom. Im still very new to the aftermarket turbo scene, this helps a lot.
 

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gear

forgive my low post count, long time member of modfords. making the move here since it is a ghost town over there..

put a hellion single turbo kit on my 01 2v with the 3650 a few months ago. currently running a 3.73 on 295/35/18's on 8psi, but trying to figure out if i want to go back to stock gear before i start cranking the boost up. car doesnt really start pulling boost until 2nd gear as of now, which may be a good thing for traction purposes.

interested in what others are running.

thanks!
Borrow a set of 28" tall tires, that will be close to running a 3.45 gear. Make a pass on each and see how your car likes it. If you are running a really mild combo compared to a radical combo the gear requirements can be radically different. My friend's former '03 2v GT had a 66mm turbo,stock cams,built 4R70W. Ran great with 3.73, but liked the 3.27 better. Memory is fuzzy but it did pick up ET and MPH.
Anybody remember the yellow fox coupe on the cover of 5.0 magazine 1991 Ford Mustang - Turbocharged Street Sleeper - 5.0 Mustang & Super Fords Magazine Guy I know bought it and went from a 4r70 and 3.27 to a glide and 3.73 and totally slowed down.
Determine a HP and ET goal and gear to match YOUR combo.
 

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If someone slowed with a glide he just had the wrong converter. A three speed is less sensitive to converter errors. A glide or any 2 speed trans is more dependent on the converter being correct.
 

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....

If someone slowed with a glide he just had the wrong converter. A three speed is less sensitive to converter errors. A glide or any 2 speed trans is more dependent on the converter being correct.
I was making the point of having the correct combo. The glide did killer 60ft's due to trans brake and the converter was built for his combo but they missed the mark. The 1/8th was quicker but the 1/4 mph and et fell off. I believe it was driving over the converter.
That's why I suggested the taller tire,if it helps or hurts ET he can us that info and make the right choice for his combo.
 

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But us talking autos and converters is not of use to OP since he has a manual trans..:smile2: He will probably do better working on the tune to make it spool better and a 2 step with timing retard for track launches.
 
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