Something Wrong With My Loved R33

[skyline girl]

Hey guys, I have a auto R33 gtst, it ran 8.22 sec. from 0 to 100km/h when I first bought it. Last two weeks, I have front mount, turbo back exhaust and manul boost control fitted, and it ran 6.85 sec. However, after I have changed my wheels form 235/45/17 front, 255/45/17 back to 245/35/19 ssa wheels, my car gone back to 7.85 sec. Dose any one has any idea what's wrong with my car?

Also, can anyone tell me how fast you R33 runs? (not GTR please, too shame to compare with GTR)

Edited March 29, 2006 by skyline girl

[Beeble]

Are you timing with a G-Tech device or just using a stopwatch and the speedo?

Anyways; two reasons:

1) Larger wheels = slower acceleration. This is why a lot of the top drag cars don't use massive diameter rims.

and,

2) if you are timing using a stopwatch and your speedometer - your new 19" wheels have a larger rolling diameter, so 100km/h on your speedo is really more like 110km/h in reality, and obviously it will take a fraction more time.

[Kaido_RR]

i get 0-100 in 6second flat (blitz power meter id3)

r33, 5spd

trust front pipe, hks cat-back, stock dump

airfilter, fmic, ebc (0.6bar)

its the auto i tell you :jk:

[skyline girl]

Well, I have timed it myself, where can I go and get it timed professtionally?

I know auto is about 1 sec. slower than man., but auto is all I can drive~~

I have to kill my bloody friend who get me into buying those bigger wheels and have my money wasted, it only look really nice. Why dose people put 20" wheels? Just for outlooking? I might go and get some cheaper and smaller wheels, like Advanti, what do you think? back to front 235/45/17 and back 255/45/17? or any suggestion?

[GTR_STEALTH]

Beeble wrote:

2) if you are timing using a stopwatch and your speedometer - your new 19" wheels have a larger rolling diameter, so 100km/h on your speedo is really more like 110km/h in reality, and obviously it will take a fraction more time.

Nah sorry dude that's incorrect...

Thats because even tho the rim size is bigger the OUTSIDE diamter is the same due to the profile of the tyre bein smaller...245/35/19 compared to the old 255/45/17

So ur speedo is not incorrect. It is still the same.

1) Larger wheels = slower acceleration.

Nah sorry dude thats incorrect also...

I could go into the technical reasons as to why but to keep things simple all i will say is: On ur mountain bike which gear do you select to accellerate faster? Answer: The bigger gear/the one with a bigger diameter.

This is why a lot of the top drag cars don't use massive diameter rims.

Again i could go into the technical side of things and start explaining centrifugal force etc etc, but to keep things really simple....In a setup with large rim low profile there is less flex in the walls. The amount of torque produced would make low profile tyres 'slip' as the energy is not 'absorpt' with too much transferred straight to the ground; and so traction is compromised.

The only reason i can think of here(assuming its not mechanical fault) is that the NEW rims are slipping due to a smaller contact surface with the road and so u are not getting good traction. 245/35/19 compared to the old 255/45/17. Also maybe the quality of the new tyres arent too good also?

Edited March 29, 2006 by R33_STEALTH

[Bobjones]

Stealth I think you have missed the point re drag cars and you have also omitted rotational mass in your calculations.

You are correct re the tyres however

[Fixxxer]

To give such a big difference in times I'd say the tyres would have to be slipping quite dramatically, to a point where I'm sure the driver would know. I'd say in the auto with that power, traction wouldn't be too much of a problem. SkylineGirl could answer that for us.

Do you have your old 17" wheels?? Were they light weight wheels? The difference in weight between the 17" and the 19" rims will play a part.

Also, if the new 19" rims are in fact "taller" (I couldn't be bothered working out the diameter, I'm at work) then this will also have a slight effect on the gearing. Effectively lowering your diff ratio. The slight increase in wheel diameter and wheel weight may be combining to make the car accelerate slower, especially from a standstill where torque is low. As we all know, the factor to getting a good elapsed time at the drags is a good launch/start. Every 0.1 sec better 60ft time equates to double that saving at the end of the 1/4mile.

Ohhh and you said you are timing it yourself, could be some slight errors there too.

Fixxxer

[mr_crust]

my r34 gts-t (auto) with fmic, pod, hiflo cat and catback exhaust on 9psi ran a 6.54 on stock wheels ....

ive got 18" on it now and i ran a 6.66 so its still the same, only a slight reaction time difference

[Ant97GTR]

R33 Stealth....The reason you gave for the larger wheels=slower accel (ie mountain bike-gearing) is completely wrong.

I ask you what would the effort be for the rider if he changed the rear wheel to a larger one with a bigger overall diameter in the same gear?? The answer is that it would require more effort and he/she would be slower getting up to speed as one rotation of the particular gear is moving a bigger wheel.

No question that bigger wheels (assuming the overall diameter is bigger) will tech slow your car down over a measured distance.

[GTR_STEALTH]

ant95GTR wrote:

R33 Stealth....The reason you gave for the larger wheels=slower accel (ie mountain bike-gearing) is completely wrong.

AHHHH My Bad, My Bad....

I had written something else but i went back and changed it for some stupid reason....I think i was half asleep :S

[ferni]

Heavier wheels (19" is prob heavier than 17") definatly doesnt help.

0-100 in about 3.7sec

[WiZardOz]

Old rear tyres - 255/45/17 = 661.3mm OD and 2076.6mm circumference

New rear tyres - 245/35/19 = 654.1mm OD and 2054.9mm circumference

100 kmh with old size rim/tyre is 99 kmh with new rim/tyre, so to get to 100km/h you will need a few extra rpm, but not enough extra that it's going to take 1 second

as you can see the new combination with the bigger rims is actually a smaller wheel overall (marginally), seems every1 is assuming you have changed to "bigger" wheels

[skyline girl]

Heavier wheels (19" is prob heavier than 17") definatly doesnt help.

0-100 in about 3.7sec

no **** man, you mean your one beats Porsche GT3? how much you have spend on your car man?

Edited March 31, 2006 by skyline girl

[R33S2]

2076.6mm circumference is 48.15 rotations for a km

2054.9mm circumference is 48.66 rotations for a km

If your speedo reads 100km traveled on the 2076.6 (old)wheels, they turned 4815 times to reach 100ks, if we multiply 4815 by the new Dia wheel the result is 98.94ks of actual travel (your speedo will read 100km)

So it seems to me that you would reach 100km/h faster than before.

(I hope I got that right! I deserve a flamin if not, its doing my head in)

It could be that the intercooler has created a bit of lag (lower power) which is common and unavoidable esp since its in the car now, the turbo now has a greater area to compress and it takes a bit longer to do it than before.

[OZ_Pomy]

unsprung weight is your enemy if your new rims and tryes are heavier than your old ones you now have more unsprung weight to deal with . more weight more energy to turn them

[skyline girl]

you guys know about xspeed? well i have me mods done there, i was thinking about change back to a smaller wheel, but i think i better get my car back in and have them check and advice me what to do. coz i still not 100% sure is the wheel or what. my old wheels are really heavy too, not quite sure how much these new one weight.

so i have full exhaust, dump pipe, hiflo cat, pod, fmic, a cheapy boost contorl fitted, what should i do next?

[jezzerrr]

Bigger wheels are heavier than smaller wheels, simple as that. if you get smaller wheels, then you need more tyre. there is an equilibrium point between tyre and wheel, where you reach the best tyre-wheel ratio, and also the best tyre compliance (complinmenting suspension, etc, for road based suspension design). This compromise for both properties is reached at the wheel diameter of 17-18 inches(for medium to large cars). Below and your tyre weights start going up, above and your wheel weights go up, and your suspension has to work harder. unless your new wheels are specifically designed to be light, the wheel/tyre combo will most likely be a higher weight than your 17's. you could always take a wheel off and weigh them, to confirm any suspicions.

To answer your questions, the only reason people buy big wheels is for bling. In theory, if your rolling diameter is actually slightly smaller (r33s2's calculations), all other things being equal, you would actually reach 100kph slightly quicker.

Next thing you should so is take it to a good tuner, so they can do the necessary adjustments for your mods and up your boost.