Journal: Wilbur Engelsma's Journal
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There are 51 entries in this Journal. Status: Silver Member  Location:  Broomfield, CO, USA |
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Gearing
Created on 2007-11-13 12:02:04
Since there is a lot of discussion on the V8 board about rear end ratios, I have done some research and calculations on the vehicle my motor/trans came from as well as the stock MGB.
First the stock MGB 1.8l engine and 4 speed OD trans:
1st: 3.333
2nd: 2.217
3rd: 1.382
4th: 1.000
OD: .802
Reverse: 3.095
Rear Axle: 3.909
This results is a final drive ratio of 13.029 in first gear and 3.135 in overdrive.
The 2.0l engine and 4 speed OD automatic trans came from a NISSAN Silvia (Japanese Domestic Market), with the following specs:
1st: 2.785
2nd: 1.545
3rd: 1.000
4th: .694
Reverse: 2.272
Rear axle: 3.916
This results in a final drive ratio of 10.906 in first gear and 2.718 in overdrive.
I am keeping the existing MGB axle with it's 3.909 gear ratio and will be running 205/65R-15 tires; This should be indistinguishable from the NISSAN axle ratio of 3.916. In addition, the MGB weight of 2200 lb is 600 lb less than the NISSAN Silvia weight of 2800 lb. Finally, the stock NISSAN motor is 205 HP, and the upgraded turbo, injectors, intercooler and intake should yield 250+ HP, which is definitely more than the stock MGB motor. The result should be very similar shift points and even better acceleration than the donor vehicle, and a huge improvement over the MG drivetrain that was removed.
Some other points of interest:
*1st gear is not as deep as the stock MG, which is a good thing
*In overdrive, 75 MPH will be about 2700 rpm.
*The 7500 rpm redline, when coupled to this transmission and rear end, should yield a theoretical top end of 202 MPH (aerodynamics and drivetrain ineffeciencies will prevent that of course, if my fear of death doesn't). Here is a site with speed calculator: http://www.car-videos.net/tools/speedrpm.asp
First the stock MGB 1.8l engine and 4 speed OD trans:
1st: 3.333
2nd: 2.217
3rd: 1.382
4th: 1.000
OD: .802
Reverse: 3.095
Rear Axle: 3.909
This results is a final drive ratio of 13.029 in first gear and 3.135 in overdrive.
The 2.0l engine and 4 speed OD automatic trans came from a NISSAN Silvia (Japanese Domestic Market), with the following specs:
1st: 2.785
2nd: 1.545
3rd: 1.000
4th: .694
Reverse: 2.272
Rear axle: 3.916
This results in a final drive ratio of 10.906 in first gear and 2.718 in overdrive.
I am keeping the existing MGB axle with it's 3.909 gear ratio and will be running 205/65R-15 tires; This should be indistinguishable from the NISSAN axle ratio of 3.916. In addition, the MGB weight of 2200 lb is 600 lb less than the NISSAN Silvia weight of 2800 lb. Finally, the stock NISSAN motor is 205 HP, and the upgraded turbo, injectors, intercooler and intake should yield 250+ HP, which is definitely more than the stock MGB motor. The result should be very similar shift points and even better acceleration than the donor vehicle, and a huge improvement over the MG drivetrain that was removed.
Some other points of interest:
*1st gear is not as deep as the stock MG, which is a good thing
*In overdrive, 75 MPH will be about 2700 rpm.
*The 7500 rpm redline, when coupled to this transmission and rear end, should yield a theoretical top end of 202 MPH (aerodynamics and drivetrain ineffeciencies will prevent that of course, if my fear of death doesn't). Here is a site with speed calculator: http://www.car-videos.net/tools/speedrpm.asp
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Summary of Previous Journal Entries
Showing previous 10 journal entries:
| Title | Date | #Pic | #Cmt | Excerpt |
|---|---|---|---|---|
| Seat Installation | 2007-11-01 | 4 | I have read a few postings about installing the Fiero seats in MGBs, and want to make sure these go in essy. I'm doing all the mods prior to recovering the seats, just in case ther... | |
| Seats | 2007-11-01 | 3 | Although the seats that came with the were way cool (two tone diamond tuck), I am replacing them with a set of Fiero seats. The seats I found are pretty trashed, but since I will b... | |
| Kick Panel Speakers | 2007-10-20 | 8 | Now that the existing holes in the kick panels are patched, it's time to cut holes in them. I have 4 Soundstream Reference speaker systems to install in the car (2 front, 2 rear), ... | |
| Tail Lights | 2007-09-12 | 6 | 3 | Since I filled in the backup light holes in the rear panel, I need to add backup lights somewhere to keep things legal. I found some info that others had put them in the tail light... |
| Fuel Tank Modifications | 2007-08-12 | 6 | I've started modifying the fuel tank. First I sealed up the existing filler tube, vent tube and the sender opening by welding a patch over each spot. I have a filler tube f... | |
| Gas Tank Internals | 2007-07-23 | 6 | I found a Datsun Roadster website where the SR20DET and other fuel injected conversions are explored at length, and found information on converting the fuel tank to an internal sum... | |
| Gas Tank | 2007-07-20 | 3 | Since I am replacing the old gas tank I thought I would cut the old one apart and see what baffles are in the stock tank. Also, I'm curious what the inside looks like after 35 year... | |
| Speaker Cutout Repair | 2007-07-16 | 5 | The previous owner had cut a couple jagged holes for 6X9 speakers in the inner kick panels. These allowed moisture into the interior and destroyed the speakers that were installed ... | |
| Bodywork | 2007-07-10 | 12 | 2 | (July 2007) I finally got a handle on the bodywork. I actually took the entire week off from work, and finished the body work from the doors back. I still need to work on the fron... |
| Gas Door | 2007-07-08 | 10 | (July 2007) So I can never leave anything alone if I can modify it- I guess it's the mechanical engineering training. My latest modification is adding a remote opening gas filler d... |
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This page last modified December 01 2007 20:50:32 pm
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