Should i have been faster with Mfactory straight cut?

[MFactory]

It all comes down to efficiency i.e gearing your car to the application. Gearing that is too long is detrimental, as is gearing that is too short. At the end of the day, short of custom ratios for a specific setup on a specific track, everything is a compromise of some sort.

Besides, gearing is not all about being "short" (we have longer gears available as well, not just short); the other main advantage being "close" i.e less rpm drop upon shifting and staying within the powerband.

Stephank: Yes, the straight cut gears decrease the parasitic losses slightly.

 

[Kozy]

Totally agree, gearing needs to be matched for your specific requirements. My reply was based on the OP stating his expectations of having fitted the gearing to a fairly stock car.

To be honest with you all , i thought upgrading to straight cut gears ould increase the Hp on the wheels , therefore other stock ek9's would be "easy pray" in a street race

 

[Stakis]

so how you can be slower in 1/4 run if you finish the strip with 5th redline? as i understand by your explanations, in such case my powerband is used by maximum possible way. so i get maximum horsepower and maximum torque for the 1/4 run, so how i can be slower?? please explain the things in more detail.

because now i finish the 1/4 track in 4th gear near redline with my oem s80, 4,785 transmission. i have 240bhp engine. my best 1/4 mile run was 13,56 with complete interior etc (this is about 1100kg with me inside).

So if i put short gears: 3,07, 2,105,1,625, 1,313 and 1,118. I still will reach about 175km/h, but i will be slower?

thanks

 

[jugbugz]

Sports cat + remap would be a very good next step. Imho I wouldn't invest much more in the engine. You could also consider swapping for a B18C. Thing with B16B and B18C is that Honda has already gotten so much out of them that it will be expensive to make big step in power. This week I read about a guy who had spent 7000pounds on a high comp B18C build and got t 241bhp...everyone his own, but imho madness. Imho the way forward would be: B16b -> B18C -> B18C with bolt-ons + remap -> turbo / K20 swap. I think these steps get you the most bang for the buck in terms of powerband, torque and (therefor) power.

Theres still a lot of power to be found on the B16B and B18C. Honda made a very good base engine.

Its not always how much 1 person spends on the engine but how they spend it. If the combination of parts don't work well, it becomes an expensive build. Sometimes, stock type Rs would accelerate faster than lightly modified type Rs in a 1/4 mile race. We've seen it.

Theres + and - for each route whether you choose B16B, B18C, Turbo or K. Nothing is cheap, but a high comp beast B18 or turboed motor would not have the longevity of the B16B and the K. In the end, its all money.

 

[jugbugz]

so how you can be slower in 1/4 run if you finish the strip with 5th redline? as i understand by your explanations, in such case my powerband is used by maximum possible way. so i get maximum horsepower and maximum torque for the 1/4 run, so how i can be slower?? please explain the things in more detail.

because now i finish the 1/4 track in 4th gear near redline with my oem s80, 4,785 transmission. i have 240bhp engine. my best 1/4 mile run was 13,56 with complete interior etc (this is about 1100kg with me inside).

So if i put short gears: 3,07, 2,105,1,625, 1,313 and 1,118. I still will reach about 175km/h, but i will be slower?

thanks

Theres a couple of things.

1 clear thing is weight.

Even if you have short gears that put your revs in the top end, did you think from where abouts your engine makes its peak power and where it starts dropping off? And if your friends power and gearing is match well, then thats 2 more negative reasons for your loss.

Gearing is also modified to match your engine powerband which is where it would make a SIGNIFICANT difference in a drag race!

My EK9 B16B benefits from shorter gearing since its tuned to make peak power at 9000rpm. But my DC5 K24/20 is an absolute monster at mid range where it makes its peak torque. So my DC5 benefits from Taller gearing to make use of its power because 1st gear on the K24 is practically unusable, the tyres just spin its shits off.

But you get the idea?

 

[BuddyClubctr]

Skills show in the corner, not on the straight Can imagine you might have expected otherwise, but I wouldn't worry about it too much

iu totally disagree a skillfull driver can make 2-3 cars difference despite the fast his car might have the same or less power!! its a fact for me and i have tested it a lot of times

 

[jugbugz]

iu totally disagree a skillfull driver can make 2-3 cars difference despite the fast his car might have the same or less power!! its a fact for me and i have tested it a lot of times

Yes thats true. Ive seen basic bolt ons + tuned dc5r running 13.4sec 1/4 mile. Stock internals but with slicks

 

[Kozy]

Pasted from another thread.

Just to add a better explanation on the end of this, let's have a look at two gearing setups, stock, and the popular 1.695, 1.384, 1.13 setup.

This is apparently adds 14%, 20% and 24% wheel torque in 3rd, 4th and 5th. Sounds great!

Lets break that down into actual road speeds though:

0-60mph, 1st and 2nd gear, no difference.
60-74mph, both in 3rd gear, short box has a 14% advantage for 14mph.
74-86mph, the short box has had to change up to 4th while stock is still in third. That is then 12mph at a 5% disadvantage.
86-91mph, stock box changes up to 4th, short box is back in the game with a 20% advantage, for all of 5mph.
At 91mph the short box changes into 5th, and from there it spends 20mph at a 1.2% disadvantage until the 111mph limiter. Stock box carries on to 113mph in 4th and onwards still in 5th.

Add aero drag which will amplify the disadvantages and reduce the gains as the speeds increase and you can kind of see how the overall gains get cancelled out.

Here's a similar break down on final drives:

Two identical cars, assume 150lbft of torque, one with 4.266 FD, one with 5.15.

Car A:
Top speeds and wheel torque in each gear for a 4.266:
1st - 41mph - 1751lb/ft
2nd - 65mph - 1114lb/ft
3rd - 91mph - 789lb/ft
4th - 126mph - 571lb/ft
5th - 155mph - 463lb/ft

Car B:
Top speeds in each gear for a 5.15: Wheel torque improved by 17.2%!
1st - 34mph - 2114lb/ft
2nd - 54mph - 1345lb/ft
3rd - 76mph - 953lb/ft
4th - 105mph - 689lb/ft
5th - 129mph - 560lb/ft

0-34mph Both in 1st - Car B has a 17.2% advantage
34-41mph, Car B is into 2nd, Car A still in 1st. Car B at a 30.2% disadvantage
41-54mph, Both in 2nd - Car B once again has a 17.2% advantage
54-65mph, Car B is into 3rd, Car A still in 2nd - Car B at a 16.9% disadvantage
65-76mph, Both in 3rd - Car B at a 17.2% advantage
76-91mph, Car B into 4th, Car A still in 3rd - Car B at a 14.6% disadvantage
91-105mph, Both in 4th, Car B at a 17.2% advantage.

Obviously there are other factors at play here, but you can see that once rolling over about 40mph the gains are negligible as the longer geared car can claw back ground while it stays in the lower gear. Your advantage is mainly focussed on that initial launch, so 0-60ft times at the strip would be improved and this will carry throughout the run to give you your improved times.

In gear acceleration is a different matter and is clearly improved significantly, but that's not making the car faster necessarily.

 

[jugbugz]

Yes, good example of 1 matter. Then theres so many other factors involved when you have 2 differently modified cars with different engine power curve, driver skill, suspension, ride height, rim/tyre size and weight, clutch type, car weight, aerodynamics etc etc.

Increasing a cars performance without a traded loss of performance requires careful planning and trial and error. Theres so many rides where people pour money into thinking it would make their car faster, when sometimes the result is opposite. It happens to everyone at some point, but thats the reality. Doesn't hurt to try different things. It just shows that combination is so important.

 

[Stakis]

can you please compare oem jdm itr (4,785) and m factory geared car (3,070 ; 2,105 ; 1,625 ; 1,313 ; 1,118 with 4,785 fd) in 1000kg car with 2,0 150ft torque and 240bhp@8500rpm car (redline 8600).

How and when each of them can be faster when accelerating?

I am just wondering if i will put oem vti 4th and 5th gears into 4,785 s80 transmission i will have quite good overall gearbox. Or if i will combine the chaged vti gears with 4,9 fd when I think i will have much more gain than m factory gearred trans.

Thank you for detailed explanations as I am lost in this gearbox world

 

[689R]

The 4.7 S80 with EK9 or 96 Spec 4th and 5th gear's is the best OEM combination gearbox IMO.

 

[Stakis]

i know this and never doubt. But would like to get soe advices what gains or loss i can have with m factory gearred trans. thank you

 

[MFactory]

It really just depends on what you want/need out of your transmission?

Are you racing your car? Are you driving on the street?

 

[Kozy]

can you please compare oem jdm itr (4,785) and m factory geared car (3,070 ; 2,105 ; 1,625 ; 1,313 ; 1,118 with 4,785 fd) in 1000kg car with 2,0 150ft torque and 240bhp@8500rpm car (redline 8600).

How and when each of them can be faster when accelerating?

Looks like you will gain maybe 5 meters on the stock car between 40-100mph, but then it'll come pissing past you when you top out at 107mph.

I am just wondering if i will put oem vti 4th and 5th gears into 4,785 s80 transmission i will have quite good overall gearbox. Or if i will combine the chaged vti gears with 4,9 fd when I think i will have much more gain than m factory gearred trans.

VTi 4th and 5th with the S80 is a good setup, it'll be a bit quicker past 80mph without being too short that it hits the limiter prematurely.

The 4.9 may make a small gain again on this from a standing start, but cross gear it wont make any significant gains in a 40-100mph sprint, and might border on being too short with a 240bhp 2 litre engine in such a light car.

 

[MFactory]

You will gain nothing on the stock boxed car, and it'll come pissing past you when you top out at 107mph.

VTi 4th and 5th with the S80 is a good setup, it'll be a bit quicker past 80mph. The 4.9 may make a small gain again on this from a standing start, but might border on being too short with a 240bhp 2 litre engine in such a light car.

Again, you can't make assumptions without knowing what his application is.

All of your "assumptions" are based upon "distance" rather than "speed". Yes, on a freeway, "distance" is what matters and yes, a longer geared transmission would have an advantage ultimately.

But these gears were designed for racing where distance is limited, hence the requirement to achieve maximum speed within the set distances.

A shorter geared transmission will reach any desired mph faster than the oem transmission and that is what matters on a closed circuit, especially one with a lot of turns.

This is why a race car with a pre-determined 120mph top speed using a transmission geared for 120mph is more efficient on a race track than a transmission geared for 150mph.

It all comes down to application

 

[Kozy]

Who said it was about distance? I'm pretty sure all my 'assumptions' are speed and distance based.

 

[Kozy]

This is why a race car with a pre-determined 120mph top speed using a transmission geared for 120mph is more efficient on a race track than a transmission geared for 150mph.

Are you saying a car power/aero limited to 120mph is better off with a 120mph box than a 150mph box? Yes, no doubt. Over-gearing a car is going to harm it's performance.

Is a car power/aero limited to 150mph better off with a 120mph box though? Under-gearing is open to debate, but I'd be inclined to say no, pretty much regardless of application.

 

[MFactory]

There is a difference been "can" do 150mph, and "able" to do 150mph. OEM ITR can do 146mph. How many owners have actually done this?

Hence why you shouldn't conclude your "assumptions" without knowing the application.

Not trying to argue with you. Again, it all comes down to application

 

[Kozy]

What application is there to know? He's stated the weight, torque, power and rev limit. The only detail missing is tyre profile, otherwise there's generally enough there to calculate the top speed and a nicely spaced set of gears to make use of it, which is what I did.

 

[MFactory]

Have you ever designed a custom set of ratios for a race car based on the circuits that it will be racing on? If not, please don't tell me that there aren't any other details missing. There are a lot of variables involved.

Again, not trying to argue with you. Doing so is pointless. We are all friends here on EK9.org