Which is better? 4.4lsd or 4.785lsd?
- Thread starter Wanggot
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- Apr 18, 2006
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here's a gear chart of two tire sizes running the same ratios, but with different FD.
as you can see from the speed at 8000 rpm, the speeds are almost similar. Tire expansion is a factor, but let's assume they are similar models with similar expansion rates, just with different sizes. but in truth, different tire sizes offer different expansion rates, so even gear calculators can't be 100% accurate to real life (of course, they don't mention this)
In short, if you were using 195/50R15 before with stock Y21 and 4.4 FD, simply by swapping tire sizes to 195/55R15 you can actually gain the effect of near +/-0.1FD ratio, depending on which tire you started out with.
notice the speeds at 8K RPM being very close, even with tire swap, because it is offset by a different FD.
in fact, if you wanted to get a feel of what 4.2 FD feels like, you can run 215/50R16 and achieve near 4.266FD ratio, as the chart below shows. That is, if you can get enough fender clearance to fit 215/50R16, he he.
Another factor in play is tire rotation resistance. more surface contact and more softer compound will make the car feel heavier or not, depending on if your engine has enough torque to offset that resistance. A 195/55R15 semi slick is way more heavy to rotate that a similar street compound 195/55R15 tire. Same with 205/50R15, which is wider. Don't forget the weight as well, though the bulk of the weight is usually the sidewalls and tread material, so this may vary, and sizes can't be an accurate measurement.
The reasons FDs are available in a multitude of sizes is because not all tire sizes can fit in the car.
Last edited:
- Apr 18, 2006
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don't have to look at all the numbers.
The only pertinent numbers are the speed vs. RPM
With 4.4+ FD, top speed per gear is reduced, but get more acceleration
With less than 4.4 FD, top speed per gear is increased, but with less acceleration.
The point of the earlier post is to state that minor FD changes can be done by tire size changes.
like for example, if you are using 195/55R15, then to get a similar effect of using 195/55R15 + 4.5+FD, you can use 195/50R15 instead.
The main idea FD manipulates top speed per gear. Additionally by doing this, it also keep the the revs in a certain RPM range.
Like most small cc high rpm engines, best torque is always around the 7-9K range, because the small cc cannot generate torque at low rpms. But torque is always less than a comparable big cc engine like B20, so the additional RPM capability is best compensated with a bigger than 4.4 FD for purposes of torque multiplication.
That is probably why for most B20B owners swapping from B16 feels the 1st and 2nd (occasionally even the third) gear being too short, but not so with the 3rd, 4th, or 5th, while the B16A owners feel that the 3rd, 4th and 5th gears being too long. It's all in the amount of torque generated on each engine, and where.
The only pertinent numbers are the speed vs. RPM
With 4.4+ FD, top speed per gear is reduced, but get more acceleration
With less than 4.4 FD, top speed per gear is increased, but with less acceleration.
The point of the earlier post is to state that minor FD changes can be done by tire size changes.
like for example, if you are using 195/55R15, then to get a similar effect of using 195/55R15 + 4.5+FD, you can use 195/50R15 instead.
The main idea FD manipulates top speed per gear. Additionally by doing this, it also keep the the revs in a certain RPM range.
Like most small cc high rpm engines, best torque is always around the 7-9K range, because the small cc cannot generate torque at low rpms. But torque is always less than a comparable big cc engine like B20, so the additional RPM capability is best compensated with a bigger than 4.4 FD for purposes of torque multiplication.
That is probably why for most B20B owners swapping from B16 feels the 1st and 2nd (occasionally even the third) gear being too short, but not so with the 3rd, 4th, or 5th, while the B16A owners feel that the 3rd, 4th and 5th gears being too long. It's all in the amount of torque generated on each engine, and where.
Last edited:
- Apr 18, 2006
- 3,677
- 170
- 1,663
yaka 4.2 bro dc_vtec.. heheheim using 4.2. cannot joining discussion..
on hiway looks like 4.9 ja..
bwhahahaha just a figure of speech, shiro. i m trying to understand or at least i think i do. but pls dun test me
- Oct 29, 2008
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mr.shiro,
recently i used my 16a gbox n addin the LSD...
b4 addin this LSD, my rpm around 3k is about 90km/h....
now after plonking the LSD, whenever cruisin around rpm 3k.. it goes 95++km/h...
why ar??? Is there anything had been kacau??
Bump: mr.shiro,
recently i used my 16a gbox n addin the LSD...
b4 addin this LSD, my rpm around 3k is about 90km/h....
now after plonking the LSD, whenever cruisin around rpm 3k.. it goes 95++km/h...
why ar??? Is there anything had been kacau??
recently i used my 16a gbox n addin the LSD...
b4 addin this LSD, my rpm around 3k is about 90km/h....
now after plonking the LSD, whenever cruisin around rpm 3k.. it goes 95++km/h...
why ar??? Is there anything had been kacau??
Bump: mr.shiro,
recently i used my 16a gbox n addin the LSD...
b4 addin this LSD, my rpm around 3k is about 90km/h....
now after plonking the LSD, whenever cruisin around rpm 3k.. it goes 95++km/h...
why ar??? Is there anything had been kacau??
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