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I've got no frame of reference, no basis for comparison - but I can say the following after having completed several lengthy (2000-4000 miles) road trips in my Spyder:
  • 3500-4500 RPM all day long is no cause for concern
  • Altitude and low-octane gas has little to no effect on performance
  • No appreciable difference in MPG after installing larger wheels
I've kept track of every penny I have spent on this car, fuel, new top, lug nuts, everything. Here's the fuel analysis for my trip from Atlanta GA to Durango, CO on stock wheels, completely stock car all the way around:
74697


And here's the fuel analysis for my trip to Arkansas on 17 inch rims and all new suspension, etc:
74699


I would have to guess that running at 400 RPM lower during these long trips would be more efficient, but I haven't seen any problems whatsoever running my engine at what I consider to be high RPM for extended periods.

The fuel mileage would have to be better, so that's something. I wonder if I'd have to grab 4th gear in order to pass somebody at 80mph though? Right now I've got just enough passing power at 80mph / 4000 RPM. If I was doing 80 at 3600 RPM I feel like I might have to spin it up to get where I need to be.
 

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Going from the OEM 5 speed to a Euro 6 on our Spyder speed lowered highway RPM, but had no measurable change to MPG. The lowered RPM does make for a more relaxed drive on the highway. Sometimes we do downshift to 5th to pass, but not often
 

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On the way to Los Angeles I got 37.94 MPG, did 384 miles from Santa Cruz to Mission Viejo with fuel to spare. Could have made it from SF but I did spend the night in Santa Cruz and filled up there.

205/45R16 320tw Sport Comp 2s on 16x7 Gram Lights 57c (not actually that light) and a Euro 6 speed with lightweight flywheel.
 

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I've got no frame of reference, no basis for comparison - but I can say the following after having completed several lengthy (2000-4000 miles) road trips in my Spyder:
  • 3500-4500 RPM all day long is no cause for concern
  • Altitude and low-octane gas has little to no effect on performance
  • No appreciable difference in MPG after installing larger wheels
I've kept track of every penny I have spent on this car, fuel, new top, lug nuts, everything. Here's the fuel analysis for my trip from Atlanta GA to Durango, CO on stock wheels, completely stock car all the way around:
View attachment 74697

And here's the fuel analysis for my trip to Arkansas on 17 inch rims and all new suspension, etc:
View attachment 74699

I would have to guess that running at 400 RPM lower during these long trips would be more efficient, but I haven't seen any problems whatsoever running my engine at what I consider to be high RPM for extended periods.

The fuel mileage would have to be better, so that's something. I wonder if I'd have to grab 4th gear in order to pass somebody at 80mph though? Right now I've got just enough passing power at 80mph / 4000 RPM. If I was doing 80 at 3600 RPM I feel like I might have to spin it up to get where I need to be.
That is what I like about the 5sp doing 75 - 80. If you need to move just push the pedal a bit more, the engine is near peak torque and you just move along. I have been testing acceleration starting at lower speeds and it might be fine staying in 6th and pressing the pedal. Noise is lower at 3300 rpm which is nice but there is still lots of wind noise which is a good thing. If I am a bit easy on the pedal I get 34 mpg easy though it is not easy to be easy on the pedal.
 

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On the way to Los Angeles I got 37.94 MPG, did 384 miles from Santa Cruz to Mission Viejo with fuel to spare. Could have made it from SF but I did spend the night in Santa Cruz and filled up there.

205/45R16 320tw Sport Comp 2s on 16x7 Gram Lights 57c (not actually that light) and a Euro 6 speed with lightweight flywheel.
I own a 5 speed and seems perfect for the hilly conditions I mainly drive on but makes sense to own a Euro 6 speed for quieter cruising even if MPG is the same.
Do you think that MPG figure would be the same with a heavier flywheel? It would be interesting to see in such a light car with decent but higher modern twin cam 16v torque peak zones if a light flywheel is better than a heavier one for overall Hwy and Urban MPG figures.
 

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On the way to Los Angeles I got 37.94 MPG, did 384 miles from Santa Cruz to Mission Viejo with fuel to spare. Could have made it from SF but I did spend the night in Santa Cruz and filled up there.

205/45R16 320tw Sport Comp 2s on 16x7 Gram Lights 57c (not actually that light) and a Euro 6 speed with lightweight flywheel.
I doubt the flywheel has anything to do with the mileage, but 37.94 mpg is enough of an improvement to make me consider getting the 6th gear more seriously.
 

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... if a light flywheel is better than a heavier one for overall Hwy and Urban MPG figures.
The effect of flywheel mass on vehicle performance is scaled by the square of the gear ratio. So, it might have a significant effect on 1st gear acceleration and urban mpg. On the highway, I predict no measurable effect.
 

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Did you adjust the odometer reading for your different tire circumference?
According to my GPS logs, the odometer is more accurate now than it was with the stock wheels. To answer the question, no I didn't change anything.
 

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My point is, you did get a change in MPG, equal to the change of wheel circumference. Whether or not that would count as appreciable I do not know.
Agreed. I'm not sure exactly how much the circumference changed in the rear, since my stock 16's had higher profile (55) tires on them, while the 17's have much lower profile (40) tires mounted.
 

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The effect of flywheel mass on vehicle performance is scaled by the square of the gear ratio. So, it might have a significant effect on 1st gear acceleration and urban mpg. On the highway, I predict no measurable effect.
I found the that the only significant results from urban mpg was only made on older engines with lower torque peaks than modern engines such as the 1zz with higher torque peaks.

There are so many factors but the MR-S is a light car to start with and when going to bigger engine and v6 in your case? all that extra torque and weight added would likely be better by lightening the flywheel and its moving parts as the torque/hp is way more than the MR-S came with. Stored energy is not such a problem with bigger engine swaps but the 1zz would not benefit with lighter flywheel mass for a daily commuter including hilly urban commutes.

I dont see improved MPG for the 1zz on hwy with taller final gearing using larger diameter tyres or transmission changes but less engine noise at cruising speeds for long trips provides a significant change to your ears! :).

v6 or bigger than stock engines with more torque will be great candidates for lighter energy storage requirements and overall reciprocating parts than on a stock engine where torque peak is quite high vs older 2 valve style heads.
 

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I do mostly highway daily driving and while I do not in any way try to hypermile I did see a 3-4 mpg gain and if I actually could hypermile I could probably get close to 40 mpg. My reason was the lower rpm while on the freeway mainly. Did I actually slow down though... ? No. Drive faster more than not. LOL

My set up from before the tranny swap was the same as after the swap for mileage difference.

(Start at Sept. fill up) http://www.fuelly.com/car/toyota/mr2_spyder/2002/vipfreak/452537/log
 
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