Total effect of boring throttle body and changing final drive ratio?

[Milgram]

Bro, you did both throttle body boring and changing your FD? Can share the specific effects please? Thanks!

[Milgram]

Not sure about the FDR for AT version. Will definitely let you know if I change it

[Seanboi]

Sis u blur liao?

[Turbonetics]

Will altering the FD affect Speedo and Odometer reading?

 

altering the FD will still give you the correct readings on the odometer and speedometer,no calibration is needed.

but changing the FD will change the rpm at certain speed which was explained by "Icekitten".

[Slayer]

bigger TB means the same pressure to the accelerator, a bit more air is let into the intake manifold. thus the 'better' response (u get more air into the system given the same throttle pressure). that doesn't change the variables inside of the combustion chamber. for bigger combustion chamber, more air need and there for a bigger throttle body to cater for the increased flow rate.

 

at highend, imagine the engine is drawing large amount of air into the chamber, bigger throttle body may help , but the question is, is the TB a bottleneck? most of the time, it is the cam action that is the bottleneck :)

 

Final drive has a lot to do with the gears and engine. the factory setting was good for stock. i don't think it is necessary if u are not increasing the output of the engine. :)

 

 

Please correct me if I'm wrong.

 

I understand that a bored throttle body will improve low-end torque (and therefore increase FC) whilst changing your final drive ratio will improve your high-end torque (and therefore decrease FC).

 

If I were to do these two mods together, what's the final effect? Will I have both improved low- and high-end torque? Or will these be cancelled out? Also, what will happen to my FC? An overall increase, decrease or no change?

 

Thanks!

 

By Boring your throttle body, you might get a better response. More Air + More Fuel = Better horsepower. But there is a limit to how much you can bored.

 

Final Drive only impacts on the gears, nothing to do with the engine. Like one bro has already explained

 

BTW what are you trying to do? Increase performance and fuel economy at the same time? Remember "With GREAT POWER, comes GREAT FUEL consumption"

[Hannson]

However, the your car ECU may be a closed loop system which might detect more Air and may offset this with lesser fuel even!

hmmm.. if it's in closed loop (most likely cruising).. it will try to hit for 14.7:1 stoich AFR.

 

If it's detecting more Air, wouldn't it pump more Fuel to keep @ 14.7:1?

 

Otherwise, if it detectes more Air and pumps less Fuel, wouldn't it lean out to higher than 14.7? And if leans out in a closed loop system, I would think that the ECU will pump more petrol to push it back to stoich AFR..

 

However, it's not in closed loop (example acceleration or high load), then it will most likely do a lookup on the base fueling table and provide whatever fuel is programmed given rpm and load.. which will usually equate a little more power.. and worse FC...

 

So unless other parts of the ECU maps are changed, you should get more power but maybe FC will suffer...

 

IMHO though.. i may be wrong....

 

Interesting discussion though....

[Seanboi]

Ok. Found the Ratios liao.

 

1st (MT) (AT)

3.545 2.847

2nd

1.904 1.552

3rd

1.310 1.000

4th

0.969 0.700

5th

0.815 -

 

Reverse

3.250 2.343

 

Final Gear Ratio 4.312 4.237

 

 

Btw there are 2 sets of TRD FDR rite? One with 4.0 and the other 3.7

Edited June 8, 2007 by Seanboi

[Hannson]

hmmm.. it's good to know the individual gears.. if ratios are closer.. you can keep in the same power band during gear shifts :)

Edited June 8, 2007 by Hannson

[Icetrap]

I understand what you meant. I agree with you! A 1.6 litre engine will always be 1.6 litres. But remember Turbo a 1.6 litre can increase the power by 30-40%

 

That is why people who mod their cars change their injectors to have more fuel injected into the same engine.

 

However, our Sg cars are usually running rich. Having a Little more air may have a slight improvement, maybe 1%?

[Hannson]

Hi Icetrap,

 

Do you mean that we should use engine management to lean the cars a little? but wouldn't that mean the engine will run hotter.. and also a leaner AFR won't necessary equate more power right? Maybe timing changes could be better.

[Ericang69]

Hi Bro a bit confuse with yr tech theory, why when engine running lean will get hotter ------- wat theory is this?

 

Can enlighten - cheers

[Hannson]

Hi Ericang69 :)

 

It's thermal physics. Increasing fuelling does cool the engine, since the volatile fuel droplets will consume heat in order to evaporate, and this is a reason why lean mixtures (decreasing fuelling holding air constant, or increasing air holding fuellin constant) might cause an engine to run hotter :)

Edited June 8, 2007 by Hannson

[Ericang69]

Sound Chim to me, is this really apply inside the combustion chamber?

 

Wat i know is more fuel = more power = more rpm = more work for engine = more heat generated (for a given constant cooling capacity)

[Seanboi]

hmmm.. it's good to know the individual gears.. if ratios are closer.. you can keep in the same power band during gear shifts :)

 

Would prefer to have a higher final gear for cruising.

[Furrynadz]

.....

[Icekitten]

Will altering the FD affect Speedo and Odometer reading?

 

altering the FD will still give you the correct readings on the odometer and speedometer,no calibration is needed.

but changing the FD will change the rpm at certain speed which was explained by "Icekitten".

 

Bro, then how come the Final Gear Set posted by EventH includes a speedo calibration line too? I would also like to know.

[Turbonetics]

eh,iam not sure leh.

maybe the installiing process will affect the reading thus need to adjust.

[Turbonetics]

Bro, I just add on to your post for TS's info.

 

[reply]

if we compare two same cars one with a lower FD and the other with a higher FD,the one with the higher FD(bigger number) will reach 0-100km/hr in a shorter time though their power are the same.

 

This is due to the gears having a closer ratio, thus less power loss between shifting of gears ie. the rpm drops lesser between shifting of gears that's why it takes a shorter time to reach a certain speed as compared to the one with a higher FD, thus making it a smoother drive as well.

------------------------------------------------------------------------------------------------------------------------------------------- for close ratio,the rpm goes up faster compare to normal gearings,and this helps for better pick-up. but when you change gear,it will also drop faster then normal gearings. so you need to practice quick shift for optimal effect of the close ratio.