Its like riding a bike, tall gears are more difficult to pedal, you have find the easiest gear to maintain speed without too much effort, all depends on hills, wind and energy.
My crazy diff ratio change idea
- Thread starter RRMaximus
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Hicap phill
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You forgot skin tight Lycra.
Plus on a bike you don’t stop for traffic lights
P38Seb
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Do you reckon OP will be wearing Lycra while doing this? Might help his crazy diff change idea
Datatek
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Do not forget to notify your insurers of your non homologated modification. Insurers just love mods they have not been advised about because in the event of an accident it lets them off the hook.
So true, if the 8 speed did not have the 2.76 ratio differential that I was considering using.
So the 2.76 ratio differential is ok in the 8 speed where the second highest gear is 1:1 ratio but not ok in my 5 speed where the second highest gear is 1:1 ratio?
You literally proved my whole point.
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Sure if I was towing a horse float and I was desperately concerned about accelerating up every hill, but in a car that is designed to tow 140% of its weight, that will have just one man, three dogs and some clothes in it this will not be an actual real world problem.Not the reason, do you have the final drive overall ratio?
Thats not what he said. anybody with a technical knowledge would know that.
That is correct. But the brick needs to be pushed through the air at a speed that suits you,you move the RPM range for a given speed in 5th suddenly you are in the limit area of the torque available for that being possible. Which is were we get to the requirment of the thorttle pedal at the slightest incline,. Yes the European motorways are better than the UKs but they are far from level. Slightest incline or headwind and you could find that holding 5th is not possible.
Bit techy I know but heyho.
J
I don't know how many times I have explained the situation but no one seems to understand that my engine will be operating well within its tolerance and will not suffer in this situation as you describe, because it does not relate.
Otherwise every time any car went up a slight incline or there was any headwind you would immediately shift it down a gear and no one does that because it's not necessary.
If you want to maintain a speed you put you foot down a bit, not change down a gear because you are within the design torque curve of the car to maintain.
If you ask for to much more torque in an auto it will change down a gear, you won’t actually go any quicker.
J
Totally. You cannot even put different wheels on the car without them adding a premium to the insurance price. Any modification versus how my car arrived from the dealer 23 years ago is considered a modified vehicle.
Yes of course, and given my car's engine an d gearbox operating range this will not happen.
Everyone here seems to think that this minor changed to the differential ratio will suddenly cause me to be driving around at 500 RPM on the highway, having to slam down my throttle just to get up a slight incline.
I don't know how many times I have explained that this will not happen but everyone comes back here with another justification why it will not work based on this same ludicrous idea.
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Good to know that you are imagining me wearing Lycra, and not helping to solve my simple engineering question.
There is a word for people like you.
What is that word again, I forgot?
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P38Seb
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Is that some homophobia I detect?
badfluffy
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but what are the 5th and 8th gear ratios
The attached image is from RRPhil on another forum where he has been helping me to understand the actual situation not the hysterical made up irrelevant situation.
According to his calculations without the modification at 75 mph I will be doing 75/39.8x1,000 RPM = 2,542 RPM.
According to his calculations without the modification at 75 mph I will be doing 75/29.5x1,000 RPM = 1,884 RPM.
Do the people here think my engine will struggle at 1,884 RPM and start lugging and will not lock up the torque converter at 75mph and be totally out of its usable torque range?
Do they think that my gearbox will decide to stay in fourth gear at this RPM level?
Do they think that I will need to shift down a gear or mash my foot to the floor if there is a slight incline or a headwind at 1,884 RPM?
At that RPM my engine produces about 350 Nm of torque so it will not be struggling given that my car will be at its lowest weight.
My car is designed to tow up to 140% of its weight, meaning it can happily move 240% of the total weight that I will be moving.
I have explained all of this before but hopefully this will be the last time that I will have to explain it, although it might be a little bit technical for some of the people here.
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No I was thinking something like juvenile or childish or 12 year-old girl mentality.
I never said you would be driving at 500rpm. I took you initially posted numbers as if you had done some calculations.
Or the need for acceleration.
And anybody that does pose a serious engineering question is Pooh poohed anyway what’s the diff?
J
P38Seb
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On the flip side.. this is your shortest post so well done on that
badfluffy
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so do the swap then
Obviously something a bit below 1:1.
But obviously the next lowest gear is the same and that is all you need to know.
If you absolutely have to know the answer to the question then I suggest you look it up on Google because this is a complete waste of time and a dead end.
If I was changing the final drive ratio by 50% and I was towing a horse float then any of these discussions would make sense.
I am not doing that which is why these discussions are a complete waste of time.
The operating margins of my engine are well inside the variation that I would be making to the final drive ratio.
This is why we are on 20+ pages of dribble, because everybody just keeps talking about an unrealistic situation that does not exist in my real world scenario, and they cannot get their mind around the fact that I will not bend over and take their hysteria as fact.
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