Looking For Best Modification Options To Beat The Honda Supra Gtr 150

[aydy]

Hi All,

I currently own a 4-Speed Autoclutch SMX

I'd like to know how much I would need modify to beat the new Honda 150CC Supra in a drag race.

Can we beat it on these mods:

62mm bore
big carb
high lift cams
big valve heads / port 'n polish
Ignition Coil
RCDI
Irridium Spark Plugs
Aftermarket gearbox
change sprocket combi

 

[docgabby]

Hi All,

I currently own a 4-Speed Autoclutch SMX

I'd like to know how much I would need modify to beat the new Honda 150CC Supra in a drag race.

Can we beat it on these mods:

62mm bore
big carb
high lift cams
big valve heads / port 'n polish
Ignition Coil
RCDI
Irridium Spark Plugs
Aftermarket gearbox
change sprocket combi

whats your aftermarket gearbox ratio?

 

[aydy]

whats your aftermarket gearbox ratio?

No, I am asking for suggestions for the upgrades I would need.
Right now, Everything is on stock.

 

[docgabby]

with your mods are you going against a stock honda supra gtr 150cc??

 

[docgabby]

box stock the honda supra is heavier than the yamaha 150 mx king and the yamaha mx king is heavier than the classic 4 speed. supra: 122kgs. mx king: 115kgs. 4 speed classic: 103kgs.



weight wise you have the advantage. just have to work on power to have that power to weight advantage

 

[docgabby]

with a 62mm bore stock stroke of 58.7mm your displacement will be 177.29cc

 

[docgabby]

you can estimate horsepower based on online calculators. keep your bike's and rider's weight down and bigger, better breathing engine...big horsepower gains definitely.

 

[docgabby]

as far as box stock horsepower:
honda supra 150cc----------------15.4 hp @ 9,000 rpm
yamaha mx king 150cc------------15.2 hp @ 8,500 rpm
yamaha 135 4 speed classic-------11.975hp (8.93kw) @ 8500 rpm

you need to add hp to beat a box stock honda supra 150cc

some website state the max hp of the 4 speed at about 8.45kw to 8.93kw at 8500 rpm

 

[docgabby]

compression ratio is also higher with the honda supra 150cc which also gives it more power aside from the increase displacement.
honda supra gtr150cc----11.3:1
yamaha mx king 150cc---10.4:1
yamaha lc135 4 speed----10.9:1

 

[docgabby]

There is a simple rule when talking about power/torque output which goes: There is no replacement for displacement.
There is a rule of thumb which says, to get greater torque, you increase the displacement. To increase the horsepower, you make your engine spin higher. Torque gets you moving, horsepower keeps you moving.

that said your increase in displacement will give you better torque......

box stock torque: honda supra 150cc--------13.5Nm at 65oo rpm.
yamaha mx king 150cc----13.8Nm at 7000 rpm.
yamaha lc135 4 speed-----11.79Nm at 5,500 rpm.

why does the 4 speed lc 135 produces lower torque at lower rpm? its because of the lower displacement and heavier counterweight..

that said you have to work on your rpm....

 

[aydy]

So Cylinder Head and Camshaft is where the optimization is at right?

Also, I think the 6 Speed Transmission is also an advantage for the Supra.
I know that It's asking a lot coming from a 4 Speed Auto clutch to beat a Dual Over Head Cam Supra which has crazy acceleration (I have ridden it, man that beast is fast)

So the question is, Can I beat it or at least keep up with it neck to neck if I can't overtake it?

MY VISION IS

- UMA RACING 62MM BLOCK KIT WITH SUPER-HEAD PACKAGE
- UMA RACING CARB 30mm / 34 mm
- UMA RACING HYPERCLUTCH
- ADJUSTABLE TIMING GEAR
- UMA RACING PLUG COIL
- UMA RACING CDI
- UMA RACING STATER MOTOR
- CJ IPOH OR UMA RACING BACK PRESSURE EXHAUST
- AFTERMARKET GEARBOX (Still haven't decided which gearbox to opt for with the lack of options for the 4speed A/C version)

I don't have any facilities here capable of lightening the Magneto and Flywheel.

What do you think about this setup?

Also, the 4th gear on my bike is almost useless, So there's that.

 

[docgabby]

six speed transmission keeps the power up due to the several gear changes but with the right four speed ratio you can go against the 6speed since its a drag race from starting start to 402 meters or less. the only problem with the auto clutch is the gear 1 shaft which is slightly longer than that with the hand clutch version. all the rest of the gears are the same. you dont want also to go too light on the magneto and counterweight because you also need the inertia to keep it spinning.

 

[docgabby]

i suggest the following gear changes:
stock gear ratio:
gear 1---34/12
gear 2---30/16
gear 3---23/17
gear 4---23/22

suggested gear ratio:
gear 1---32/12
gear 2---29/16
gear 3---25/18
gear 4---26/23

black are stock, red is racing.

how to get the gear 3 and gear 4 thru haen or hku racing. he can make you these custom gears.



this will tighten your gaps between gears so there will be no drop in rpm.

you wont have problems with your auto-clutch transmission since you will be retaining your gear 1-12T shaft which is longer than that of the hc version. gear 1 and gear 2 wont be a problem since there are alot of aftermarket sold..cms, faito, etc.

 

[aydy]

Thanks a lot for the detailed responses doc. Really appreciate it.

So changing my gearbox sprocket/tranny to what you suggested and upgrading to what I mentioned in my earlier post, It should be enough to catch up with a supra right?

 

[docgabby]

why play catch up when you can smoke em ....of course EFI offers a precise metering of air/fuel mixture for instant response and depending of how the ignition curve also is manipulated to retard or advance ignition timing.

 

[docgabby]

and of course reciprocating weight like lighter wheels...improve acceleration.

 

[docgabby]

http://www.automotiveforums.com/t325502-preferred_drag_racing_transmissions.html

http://www.badasscars.com/index.cfm...ct_id=442/category_id=13/mode=prod/prd442.htm

here are just a few of articles about 4 speed vs 5 speed or 6 speed for drag racing........

 

[aydy]

So beating the Supra on a drag race is not an issue with the gear ratio you suggested with the correct upgrades. But is this gear ratio good for daily driving? We don't have long roads here, about 2 Miles long with urban sharp twisties.

Also, with the UMA Setup what do you think about the stock Exciter 150 Exhaust? it should be enough right? or should I make the elbow a little bit bigger?

 

[docgabby]

So beating the Supra on a drag race is not an issue with the gear ratio you suggested with the correct upgrades. But is this gear ratio good for daily driving? We don't have long roads here, about 2 Miles long with urban sharp twisties.

Also, with the UMA Setup what do you think about the stock Exciter 150 Exhaust? it should be enough right? or should I make the elbow a little bit bigger?

it can be used as daily driver. just have to find the right sprocket combination for your rides. because the ratio is close it would love twisties or curves. all stock exhausts are heavy due to built in catalytic converter and restricted flow. i think it is still best to use aftermarket with less flow restriction though louder.

 

[aydy]

it can be used as daily driver. just have to find the right sprocket combination for your rides. because the ratio is close it would love twisties or curves. all stock exhausts are heavy due to built in catalytic converter and restricted flow. i think it is still best to use aftermarket with less flow restriction though louder.

Yeah I know, Which is why I am going to remove the catalytic converter.
We used to have open pipes here, But now rules changed and they won't allow anything except the stock exhaust. But we can still use a stock exhaust of another bike.

Also, What do you think about the fuel consumption compared to stock mileage?