Franken_7
New Member
Hello everyone.
I’m laying out my plans to swap an early 1uz-non VVTI into my 1976 Triumph TR7 and wanted to run some thoughts across the collective brain trust here. Let me start off with yes, I know the 1uz/3uz vvti make more hp and torque. Yes, I know the 1uz non-vvti ECU isn’t really tunable and either a piggyback or aftermarket will be required. Yes, I know the Chevy LS makes more hp, is more tunable, and would be an easier option. While the 1uz/3uz is probably an all around better engine, I think it just looks like most every other V8 out there. The early non-vvti is unique looking as is the TR7. I want a daily driver with quick acceleration and a smooth, fairly quiet cruising attitude. 200-225 rwhp is more than enough for a 2500 lb / 1130kg car. And really anything over 250 rwhp is overkill and would be in a range that I will probably never really get into.
My initial thoughts are on the rear end and transmission gearing I am thinking about. I think I have the information correct.
1uz non-VVTI
Rated at 256-261 hp. (Probably closer to 230-235) and approximately 260 lb-ft of torque.
Stock rear end gearing 3.76
Stock tire size 245/45-18 (26.70 inches / 67.8 cm)
A340 automatic transmission gears 2.80 / 1.53 / 1.00 / 0.75
Using the formula RPM = [ MPH x (Transmission gear) x (Rear end gear) x 336 ] / Tire dia. in inches gives me about 2,600 rpm at 55mph in 4th gear and 2480 rpm at 70mph. This seems a little high to me. I would have thought cruising rpm’s would be closer to 2000-2100.
The TR7 has rather small tires. 205/50-15 (23 inch / 58.4 cm). Using the stock auto and an equivalent rear gear (the IRS isn’t really adaptable to the TR7) would make the rpm’s even higher at the same cruising speeds. Using a Ford 8.8 with 3.27 gears and the smaller tires bring the cruising rpm’s back in line with the stock numbers.
The first question is…does my math seem correct with everyone’s real world experiences?
The second question is…will the non-vvti cruise for hours at 1900-2100rpm or would that be lugging the engine?
The reason I ask about the lower cruising rpm’s is that I want to swap in a T-56 6-speed and the dual overdrive options bring the cruising rpm’s down to those level depending on which gear set I choose. I will have the options for 5th/6th gears of .84/.57 or .80/.63 or .74/.50
With the smaller tires (lighter rotational mass and smaller diameter tires accelerating faster) and the light weight of the car, I think the 3.27 will still be quick from a dead stop. A slight bump in the rear gear like a 3.31 from a Mustang may be just a hair quicker and only a slight rise in cruising rpm’s, but a more difficult job in shortening it for the TR7.
The only other question is again, because of the smaller tires and light vehicle weight, my first gear options are either a 2.97 or a 2.66. With the A340 having a 2.80 first gear I’m leaning towards the 2.66 but if the 2.97 won’t be too hard to control (I don’t want a bunch of wheel spin and fishtailing) it does give me more overdrive options.
Any thoughts?
I’m laying out my plans to swap an early 1uz-non VVTI into my 1976 Triumph TR7 and wanted to run some thoughts across the collective brain trust here. Let me start off with yes, I know the 1uz/3uz vvti make more hp and torque. Yes, I know the 1uz non-vvti ECU isn’t really tunable and either a piggyback or aftermarket will be required. Yes, I know the Chevy LS makes more hp, is more tunable, and would be an easier option. While the 1uz/3uz is probably an all around better engine, I think it just looks like most every other V8 out there. The early non-vvti is unique looking as is the TR7. I want a daily driver with quick acceleration and a smooth, fairly quiet cruising attitude. 200-225 rwhp is more than enough for a 2500 lb / 1130kg car. And really anything over 250 rwhp is overkill and would be in a range that I will probably never really get into.
My initial thoughts are on the rear end and transmission gearing I am thinking about. I think I have the information correct.
1uz non-VVTI
Rated at 256-261 hp. (Probably closer to 230-235) and approximately 260 lb-ft of torque.
Stock rear end gearing 3.76
Stock tire size 245/45-18 (26.70 inches / 67.8 cm)
A340 automatic transmission gears 2.80 / 1.53 / 1.00 / 0.75
Using the formula RPM = [ MPH x (Transmission gear) x (Rear end gear) x 336 ] / Tire dia. in inches gives me about 2,600 rpm at 55mph in 4th gear and 2480 rpm at 70mph. This seems a little high to me. I would have thought cruising rpm’s would be closer to 2000-2100.
The TR7 has rather small tires. 205/50-15 (23 inch / 58.4 cm). Using the stock auto and an equivalent rear gear (the IRS isn’t really adaptable to the TR7) would make the rpm’s even higher at the same cruising speeds. Using a Ford 8.8 with 3.27 gears and the smaller tires bring the cruising rpm’s back in line with the stock numbers.
The first question is…does my math seem correct with everyone’s real world experiences?
The second question is…will the non-vvti cruise for hours at 1900-2100rpm or would that be lugging the engine?
The reason I ask about the lower cruising rpm’s is that I want to swap in a T-56 6-speed and the dual overdrive options bring the cruising rpm’s down to those level depending on which gear set I choose. I will have the options for 5th/6th gears of .84/.57 or .80/.63 or .74/.50
With the smaller tires (lighter rotational mass and smaller diameter tires accelerating faster) and the light weight of the car, I think the 3.27 will still be quick from a dead stop. A slight bump in the rear gear like a 3.31 from a Mustang may be just a hair quicker and only a slight rise in cruising rpm’s, but a more difficult job in shortening it for the TR7.
The only other question is again, because of the smaller tires and light vehicle weight, my first gear options are either a 2.97 or a 2.66. With the A340 having a 2.80 first gear I’m leaning towards the 2.66 but if the 2.97 won’t be too hard to control (I don’t want a bunch of wheel spin and fishtailing) it does give me more overdrive options.
Any thoughts?
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