Any feedback on alternative 5th gear ratio?
Discussion
Recently there has been talk of a few people swapping out the 5th gear on their G50 box for a PHII manufactured/supplied 0.68 ratio.
What I would like is some feedback:
How is this working out for general road use, are you having to change down to 4th to overtake on the motorway?
Does the engine bog down when changing into 5th when not pushing the car hard (ie close to the rev limit)?
I am looking at this change to give a higher top speed on track and lower revs when cruising on road, but worry slightly about general road use so any comments would be greatly appreciated.
What I would like is some feedback:
How is this working out for general road use, are you having to change down to 4th to overtake on the motorway?
Does the engine bog down when changing into 5th when not pushing the car hard (ie close to the rev limit)?
I am looking at this change to give a higher top speed on track and lower revs when cruising on road, but worry slightly about general road use so any comments would be greatly appreciated.
The top gear on my Ultima was 212mp @7k... the next gear down was 165mph so it had a huge gap.
For motorway driving this was excellent and there was no problem cruising around... the only time it ever felt lacking was when I did top speed run's but it still pulled hard and definatelly didn't dog... but mine was a 4speeder so I'd not expect a 5 speeder to have the same problem if you also change the 4th gear.
For motorway driving this was excellent and there was no problem cruising around... the only time it ever felt lacking was when I did top speed run's but it still pulled hard and definatelly didn't dog... but mine was a 4speeder so I'd not expect a 5 speeder to have the same problem if you also change the 4th gear.
Using the gear calculator I have and based on the ratios for a G50/50 or /52 and using the torque figures for my engine it gives the best shift points.
With existing 5th gear you will drop 1355rpm in the shift.
With new 5th gear you will drop 1893rpm in the shift.
The calc shows that the ideal shift with the new gear would be some 346rpm higher than the existing gears ratios which is why the shift points shown above do not seem very far apart.
If you have a dyno sheet for your engine you can find the ideal shift points for your engine/box combo.
Steve
With existing 5th gear you will drop 1355rpm in the shift.
With new 5th gear you will drop 1893rpm in the shift.
The calc shows that the ideal shift with the new gear would be some 346rpm higher than the existing gears ratios which is why the shift points shown above do not seem very far apart.
If you have a dyno sheet for your engine you can find the ideal shift points for your engine/box combo.
Steve
I have a full set of altered ratios from PH II in my G50/03 and although the 5th gear is .756 (2.604 overall), I must say that even though all was worked out on computer, I was a little apprehensive. Having actually used the car for several hundred miles so far, I can report that everything is bang on. @ 75mph the motor turns 2,300rpm and can accelerate with ease for overtaking. It may be worth bearing in mind however that although the motor
is making good power higher up in the revs, as a result, the peak torque figure also occurs higher up the rev range. I do not wish to sound condescending in any way but I would imagine that most motors out there, although are making less torque than my engine, are making it at lower rpm which I feel may be beneficial as if the final gear is yet more over driven, in theory the car should be nearer peak at lower mid gear overtaking speeds, doe's that make sense? In short, I think that it is not only the choice of ratio used that will be of importance but the engine spec too. I would advise you to try it for real rather than take some ones word as we all seem to have a different remit with regards to this conundrum.
is making good power higher up in the revs, as a result, the peak torque figure also occurs higher up the rev range. I do not wish to sound condescending in any way but I would imagine that most motors out there, although are making less torque than my engine, are making it at lower rpm which I feel may be beneficial as if the final gear is yet more over driven, in theory the car should be nearer peak at lower mid gear overtaking speeds, doe's that make sense? In short, I think that it is not only the choice of ratio used that will be of importance but the engine spec too. I would advise you to try it for real rather than take some ones word as we all seem to have a different remit with regards to this conundrum.
Edited by GTWayne on Friday 19th January 13:02
GTWayne said:
.......I think that it is not only the choice of ratio used that will be of importance but the engine spec too....
That's why I suggested that starting with the engines dyno sheet in the calculator was important. Dependant on where a given engine makes its best torque will determine the best ratios and best shift points.
Steve
My engine is back next week - so by March I'll give you all the feedback you need for a back to back G50 fourth and fifth gear swap to ration recommended by PHII to complement the OE 1, 2 and 3 gears, my 200mph ambition and the motorway cruising that I thought could come down by 1.5k or so.
Laters
Pete
Laters
Pete
I have been using a gear calculator, mainly to see what I too would need to break the 200mph barrier. I am currently hitting 172mph@6800rpm, with peak torque at 4200 and peak power at 6000. The 0.68 ratio is the only one that will get me past 200, with a slightly reduced rev limit for a margin of safety. The calculator shows that changing into 5th will put be back in my peak torque band (just) which will be fine when on track I guess. But what would it be like on road when I will not be using the full rev range, although the cruise engine speed at 80mph looks nice and relaxed.
Here are the analysis results:
Top Gear gives 32.354 MPH/1000 RPM and a top speed of 210.302 MPH at 6500 RPM
Engine speeds in top gear:-
30 MPH = 927 RPM 40 MPH = 1236 RPM 50 MPH = 1545 RPM 60 MPH = 1854 RPM
70 MPH = 2164 RPM 80 MPH = 2473 RPM 90 MPH = 2782 RPM 100 MPH = 3091 RPM
Top Speed in 1 gear = 40.859 MPH
And changes into 2 gear at 3824 RPM dropping 2676 RPM
Top Speed in 2 gear = 69.454 MPH
And changes into 3 gear at 4448 RPM dropping 2052 RPM
Top Speed in 3 gear = 101.494 MPH
And changes into 4 gear at 4955 RPM dropping 1545 RPM
Top Speed in 4 gear = 133.152 MPH
And changes into 5 gear at 4115 RPM dropping 2385 RPM
Top Speed in 5 gear = 210.302 MPH
Here are the analysis results:
Top Gear gives 32.354 MPH/1000 RPM and a top speed of 210.302 MPH at 6500 RPM
Engine speeds in top gear:-
30 MPH = 927 RPM 40 MPH = 1236 RPM 50 MPH = 1545 RPM 60 MPH = 1854 RPM
70 MPH = 2164 RPM 80 MPH = 2473 RPM 90 MPH = 2782 RPM 100 MPH = 3091 RPM
Top Speed in 1 gear = 40.859 MPH
And changes into 2 gear at 3824 RPM dropping 2676 RPM
Top Speed in 2 gear = 69.454 MPH
And changes into 3 gear at 4448 RPM dropping 2052 RPM
Top Speed in 3 gear = 101.494 MPH
And changes into 4 gear at 4955 RPM dropping 1545 RPM
Top Speed in 4 gear = 133.152 MPH
And changes into 5 gear at 4115 RPM dropping 2385 RPM
Top Speed in 5 gear = 210.302 MPH
pb3 said:
Top Speed in 4 gear = 133.152 MPH
And changes into 5 gear at 4115 RPM dropping 2385 RPM
Top Speed in 5 gear = 210.302 MPH
Personally, I would say that the gap between 4th and 5th is to large and therefore would recommend changing 4th also. Luckyp is correct in saying "watch this space" as he is in the process of doing just this.
pb3 said:
Trouble is I want to do this now really and changing 4th will significantly increase the costs. Although I do agree that 4th-5th is quite a big drop but will it effect the overall driveability greatly (in a bad way)?...
Have you thought about swapping your 5 for a 6 speed box? I did this about a year ago and was quite pleased with the results. If my memory serves me...1-5 was very similar but adding the 6th was like having an overdrive. I went from G50-03 to a G50-20.
Just a thought,
Brad Z
Phil
Why are you looking at changing up at such low revs?
If your max torque is 4200 then I would expect your changes to be much higher revs.
The calculator I am using is working out the torque at the wheels and indicates a shift at the point where the wheel torque is higher in the next gear than the current gear.
If you have your dyno figures and G50/?? box number I will punch in the numbers.
Steve
Why are you looking at changing up at such low revs?
If your max torque is 4200 then I would expect your changes to be much higher revs.
The calculator I am using is working out the torque at the wheels and indicates a shift at the point where the wheel torque is higher in the next gear than the current gear.
If you have your dyno figures and G50/?? box number I will punch in the numbers.
Steve
Steve, sorry for the delay, but when I found my dyno sheet it seems to start as 3115rpm so it is probably not that much use to you?!
This is what I have:
RPM Torque HP
3115 474.5 281.4
3353 471.4 301.0
3500 469.0 312.6
3700 481.2 339.0
4000 520.3 396.3
4200 533.5 426.7
4500 530.0 454.2
4700 518.1 463.6
5000 515.1 490.4
5200 509.6 504.5
5500 496.7 520.1
5700 481.1 522.2
6000 460.4 525.8
6200 433.2 511.4
6500 413.4 511.7
6700 392.2 500.4
6969 306.7 401.1
Rev limit 6500. Rolling circ. 2030mm. Standand G50/00 gearing.
Cheers
This is what I have:
RPM Torque HP
3115 474.5 281.4
3353 471.4 301.0
3500 469.0 312.6
3700 481.2 339.0
4000 520.3 396.3
4200 533.5 426.7
4500 530.0 454.2
4700 518.1 463.6
5000 515.1 490.4
5200 509.6 504.5
5500 496.7 520.1
5700 481.1 522.2
6000 460.4 525.8
6200 433.2 511.4
6500 413.4 511.7
6700 392.2 500.4
6969 306.7 401.1
Rev limit 6500. Rolling circ. 2030mm. Standand G50/00 gearing.
Cheers
pb3 said:
Steve, sorry for the delay, but when I found my dyno sheet it seems to start as 3115rpm so it is probably not that much use to you?!
This is what I have:
RPM Torque HP
3115 474.5 281.4
3353 471.4 301.0
3500 469.0 312.6
3700 481.2 339.0
4000 520.3 396.3
4200 533.5 426.7
4500 530.0 454.2
4700 518.1 463.6
5000 515.1 490.4
5200 509.6 504.5
5500 496.7 520.1
5700 481.1 522.2
6000 460.4 525.8
6200 433.2 511.4
6500 413.4 511.7
6700 392.2 500.4
6969 306.7 401.1
Rev limit 6500. Rolling circ. 2030mm. Standand G50/00 gearing.
Cheers
This is what I have:
RPM Torque HP
3115 474.5 281.4
3353 471.4 301.0
3500 469.0 312.6
3700 481.2 339.0
4000 520.3 396.3
4200 533.5 426.7
4500 530.0 454.2
4700 518.1 463.6
5000 515.1 490.4
5200 509.6 504.5
5500 496.7 520.1
5700 481.1 522.2
6000 460.4 525.8
6200 433.2 511.4
6500 413.4 511.7
6700 392.2 500.4
6969 306.7 401.1
Rev limit 6500. Rolling circ. 2030mm. Standand G50/00 gearing.
Cheers
Will play with those this evening.
Steve
ultimagtr-ger said:
Hello,
I have a G50-00.
I would like to have a longer gearing for every gear - but without changing all gears.
-> Is it possible to change the final drive ratio?
Any thoughts?
Regards
Oliver
I have a G50-00.
I would like to have a longer gearing for every gear - but without changing all gears.
-> Is it possible to change the final drive ratio?
Any thoughts?
Regards
Oliver
You are probably in a better position than most to find out the necessary info but I think I am correct in saying that there is very limited (if indeed any?) choice.
My requirement was much the same as yours but I changed every gear, the result: Absolutely the right thing to do, worth every penny.
Here are the analysis results:
Top Gear gives 29.6 MPH/1000 RPM and a top speed of 192 MPH at 6500 RPM
Engine speeds in top gear:-
30 MPH = 1013 RPM
40 MPH = 1351 RPM
50 MPH = 1689 RPM
60 MPH = 2027 RPM
70 MPH = 2365 RPM
80 MPH = 2703 RPM
90 MPH = 3040 RPM
100 MPH = 3378 RPM
Top Speed in 1 gear = 44 MPH
And changes into 2 gear at 6200 RPM dropping 2602 RPM
Top Speed in 2 gear =78MPH
And changes into 3 gear at 6238 RPM dropping 1756 RPM
Top Speed in 3 gear = 109 MPH
And changes into 4 gear at 6181 RPM dropping 1430 RPM
Top Speed in 4 gear = 144 MPH
And changes into 5 gear at 6219 RPM dropping 1321 RPM
Top Speed in 5 gear = 192 MPH
A change to the .688 5th gear ratio would give 211mph.
I don’t understand where your figures came from that showed 210 @ 6500.
My calculator uses tyre sizes (18”, 335, 30%) and gives a tyre diameter of 25.9” = circ 2067.56mm. If I use your figure of 2030mm the speeds are even lower.
To get 210mph @ 6500 you would need a tyre diameter of 28.3” = circ 2260.6mm.
Steve
Top Gear gives 29.6 MPH/1000 RPM and a top speed of 192 MPH at 6500 RPM
Engine speeds in top gear:-
30 MPH = 1013 RPM
40 MPH = 1351 RPM
50 MPH = 1689 RPM
60 MPH = 2027 RPM
70 MPH = 2365 RPM
80 MPH = 2703 RPM
90 MPH = 3040 RPM
100 MPH = 3378 RPM
Top Speed in 1 gear = 44 MPH
And changes into 2 gear at 6200 RPM dropping 2602 RPM
Top Speed in 2 gear =78MPH
And changes into 3 gear at 6238 RPM dropping 1756 RPM
Top Speed in 3 gear = 109 MPH
And changes into 4 gear at 6181 RPM dropping 1430 RPM
Top Speed in 4 gear = 144 MPH
And changes into 5 gear at 6219 RPM dropping 1321 RPM
Top Speed in 5 gear = 192 MPH
A change to the .688 5th gear ratio would give 211mph.
I don’t understand where your figures came from that showed 210 @ 6500.
My calculator uses tyre sizes (18”, 335, 30%) and gives a tyre diameter of 25.9” = circ 2067.56mm. If I use your figure of 2030mm the speeds are even lower.
To get 210mph @ 6500 you would need a tyre diameter of 28.3” = circ 2260.6mm.
Steve
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