My 2L B-Series N/A Project

[shiroitenshi]

As far as i know and tested, FD does not affect rpm drop on each gear. FD just alter the entire gear ratio speed per gear.

It is the gear ratio that affect each indivual rpm drop and speed.

Stock EK9

3rd-1.458 3rd-4th rpm drop 2050rpm
4th-1.107 4th-5th rpm drop 2000rpm
5th-0.848

Hmm.. actually it does in my head.. at least in theory it does, after all, looking at the speed vs rpm chart here, its obvious that as speed climbs, rev drops become more exaggerated. Naturally we won't see much difference on 8-9K rpm engines, but I think it should be quite apparent on an 11K spoon engine.

Edit.. I think i interpret it wrong, I think you're right that FD does not affect rev drop points, but rather how high the engine is revving that affects the rev drop points. Opps on my part... :P

Which reminds me of something, that on low speed shifts, the 3rd gear rev drop is only like 1K? So in a way, how high the rpm during the point of shifting affects how much rpm drop.

Chart for a Y21 g/box if the car has enough torque to actually push the gears up to those speeds.

Of course, this is theory, and in my head, I also think that drag co-efficiency (Cd) and momentum would play a part in affecting real life rev drop points, which is why as speed climbs, there are differences in theory and practical applications.

During off throttle/shifting time, does the car still accelerate due to momentum, or does it start to decrease speed due to drag?

Man, got my head in a bind there.

 

[evoX2]

bro shiro, after checking with the gear calc, i also found that final drive wont affect rpm drop during gear change, only the top speed of each gear. how come higher fd give lower top speed for each gear, then mind to explain why 4.75 is better than 4.4 fd? i'm confuss.... thx.....

 

[shiroitenshi]

bro shiro, after checking with the gear calc, i also found that final drive wont affect rpm drop during gear change, only the top speed of each gear. how come higher fd give lower top speed for each gear, then mind to explain why 4.75 is better than 4.4 fd? i'm confuss.... thx.....

Yeah.. I noticed it when I put in the numbers as well.. I remembered last time I noticed that rev drop numbers were different depending gearsets, and I thought it was the FD, but apparently it isn't. It's where the engine rpm is at that affects it.. I make a mistake on this one.

Anyway, the 4.75 is better than 4.4 fd in terms of torque multiplication.

I think I explained to you earlier about using FD to reduce top speed, but get better torque. In a way, you reach that speed earlier, because what the FD does is doing torque multiplication. If you have a mountain bike, motorbike or geared bicycle, I think easiest to show this point. The rear sprocket, in this case, is your final drive. the bigger the rear sprocket is, the lighter to pedal/faster acceleration, but you sacrifice the top speed achievable on each gear.. To get around it, you either pedal faster or rev it higher on the motorbike (more rpm).

Try it, and it should be clear to you.

 

[chris2000]

Shiro you are right with rev drops as rpm change climb.

My info provided were all based on a 8500rpm limit gearchange where most road cars will go or higher cc race engine.

So for the very close Spoon ratio, at 8500rpm limit the rev drop was indeed about 1600rpm. But if you take the rev up on a B16B like how Spoon does it at 11krpm, the rpm drop on gear change is 2150rpm. And we all know not many locally build engine can take it to 11k rpm and the highest i ever heard in malaysia was 10.5k rpm and the result was a complete overhaul after every race or spin a bearing at 10.5k rpm!!

So thats why i'm toying around the idea of searching a ratio that have rpm drop in the region of 1900-2000rpm on a 8500rpm and 2000-2100rpm drop on 9000rpm and 2100-2200rpm drop on 9500rpm which is about where most cars can rev to and rpm drop is at the level where Spoon intended it to be at 11k rpm. :)

 

[evoX2]

ok, i get what u mean now. but will a 4.75fd be harder to launch comparing to a 4.4fd due to the extra torque?

 

[shiroitenshi]

ok, i get what u mean now. but will a 4.75fd be harder to launch comparing to a 4.4fd due to the extra torque?

Lauching, you have to ask hattech.. he's a consistent launcher. Even after making a mistake doesn't kill his tempo. :P I saw him launch his car last time, and he can do it consistently.. chalk it up to his experience.

I don't think 4.75fd will be harder to launch.. afterall, the ITR g/box with the 4.785 ratio also uses the same 1st gear ratio your car is using. It increases torque, but not too extreme, futhermore your 2nd is 1.9, as opposed to the stock ITR at 2.105

But like my friend told you, it is cheaper in the long run to buy a ITR with a 4.785, since you get the ratio and the LSD for a price that's significantly lower than putting in the parts one by one.

 

[shiroitenshi]

Shiro you are right with rev drops as rpm change climb.

My info provided were all based on a 8500rpm limit gearchange where most road cars will go or higher cc race engine.

So for the very close Spoon ratio, at 8500rpm limit the rev drop was indeed about 1600rpm. But if you take the rev up on a B16B like how Spoon does it at 11krpm, the rpm drop on gear change is 2150rpm. And we all know not many locally build engine can take it to 11k rpm and the highest i ever heard in malaysia was 10.5k rpm and the result was a complete overhaul after every race or spin a bearing at 10.5k rpm!!

So thats why i'm toying around the idea of searching a ratio that have rpm drop in the region of 1900-2000rpm on a 8500rpm and 2000-2100rpm drop on 9000rpm and 2100-2200rpm drop on 9500rpm which is about where most cars can rev to and rpm drop is at the level where Spoon intended it to be at 11k rpm. :)

Well.. in that case, I'm thinking of mixing oem gear ratios.

I wonder if the layshaft on the Y1 would fit in a Y21? The gearbox is rare though so I'm probably dumping the idea.

I'll post the rest later.. makan hour, after this work, and after that work. not going to be in front of the computer for the rest of the day. Post the rest later. Got some questions about my planned ratios.

 

[Blue Little Lorry]

Chris2000, Where did you get the DC sports 4-1 from and how much is it ?

 

[hattech-v]

chris, u rite spoon ratio is closer compared to ats/kaaz
actually what make it closer is the closer the number from each individual gear will make the rpm drop lesser...
for me, gear ratio combination is the most important thing for drag or even for track....
fd does not effect the individual ratio/rpm instead the speed for individual gear...
about what final drive can help u is all about the torque multiplication...
u can find lots of info here...

Gearing I: Torque multiplication and Final Drives - Team Integra

 

[evoX2]

chris, u rite spoon ratio is closer compared to ats/kaaz
actually what make it closer is the closer the number from each individual gear will make the rpm drop lesser...
for me, gear ratio combination is the most important thing for drag or even for track....
fd does not effect the individual ratio/rpm instead the speed for individual gear...
about what final drive can help u is all about the torque multiplication...
u can find lots of info here...

Gearing I: Torque multiplication and Final Drives - Team Integra

thanks for the info. now i understand why final drive is so important. :_:

hattech, will it be harder to launch with the extra torque?

 

[hattech-v]

that one very subjective depen on how many times u practise... hehe
as long as u know how to control the pedal then any torque oso u can handle..

in other word, practise make perfect... but sometime oso can make defect.. haha

 

[evoX2]

heard u r master of launch, must get some tips from u....hehe...

btw, u got any used 16" semi slick for sale?

 

[hattech-v]

i think got. a048. but with my fren now.
i'm not master.. oso still learning... always kantoi launching jugak... haha

 

[dcloo]

i think got. a048. but with my fren now.
i'm not master.. oso still learning... always kantoi launching jugak... haha

celaka a048 also dun wan tell me
i go bought brigstone
faster ask ur fren bring to ur shop
i come n collect it tomorrow

 

[hattech-v]

hahhaha... i tot u dun wan... long2 time ago offer u tapi u tak mau...
aiyaaa....