Custom Gearbox Rebuild - Advice Needed

[VAG Fan]

I've just shown how much the flywheel contributes to total energy (2%) and total momentum (fraction of a %).

What hasn't been mentioned here: at constant speeds, the mass of the flywheel doesn't play any role at all. It only comes into play when the revs change quickly, e.g. blipping the throttle or racing through lower gears. But at a constant 120 km/h, the flywheel neither gives momentum to the car, nor does it take momentum from the car. So its mass is irrelevant.

In fact, the car as a whole will be a couple of kg lighter after the skimming, so you would require ever-so-slightly LESS than 50% throttle to get up the same hill.

[Trishen94]

Hi vag fan ...
So since we all entitled to our own opinions id just like to clarify i used the word EG in my comment which stands for EXAMPLE
And what i have noticed on many of my n/a cars is that after skimming the flywheel it does rev up much faster on the lower gears and lower revs but on the higher revs and higher gears up hills u will definitely need to drop a gear or accelerate harder compared to a standard flywheel ...think about it do u think if it only made 1% diff will they really go through all the hassle of manufacturing a larger more heavier part... i would rather just tweak the ecu which cost nothing for 1% rather than waste money on adding weight to the car to make it slower ... if u really compare a flywheel before and after skimming u can sometimes skim away close to 50% of it so in simpler terms for EG ...manufactures could have made 2 flywheels with 10kg of material instead of 1 which is a hell of a profit ...if u look at most modern cars even the sump is plastic just coz its cheaper , cost less and weighs less..
think about it to increase profits in any bussiness u gota decrease expense so for 1% power its financialy a very stupid decision ... so with science it is not actually what happens in real life ... or could be the formula is off i dont know but these are actual real life experiences that i have experienced and not done on paper with a pencil ...
No i did not do science but i can tell u that the little weight on the flywheel provides much much more momentum than the 1 or 2% that u talking about

[VAG Fan]

Hi Trishen94,

As you quite rightly say, we're all entitled to our own opinions, including the opinion that there is somehow a disconnect between science and "real life".

If what you do, works for you, that's great. Peace.

[Trishen94]

Hi Trishen94,

As you quite rightly say, we're all entitled to our own opinions, including the opinion that there is somehow a disconnect between science and "real life".

If what you do, works for you, that's great. Peace.

Cool bud

[jovann46]

Im again running on 13" wheels 185/60/R13 tyres. On those @ 7000rpm you will do 218kmh,remember this is using a gear calculator so only an indication. My caddy did 214kmh @7400rpm limiter, flowed u flow head and cross cut flowed mp9 intake manifold (sac) , 298h cam, mp9 with go-tech, balanced bottomend, knive edged crank and lightened std flywheel. Tried the lightened flywheel with the lightened crank an revved like a bike to 3rd gear, it was too light for my application or my compression too low as I have used that combo on a msth motor with good results. Big valve head lasted about 2 years before it dropped a valve, replaced head with stock valve sized abc mp9 head, again flowed by sac and it felt more responsive and quicker than the bigvalve head.Engine was a shortblock 2 liter. My 5cents.

[missioner]

Still so many people dont get it.

Your motor does nothing to top speed if all is even.

Gearing is finite and not adjustable. Only way is to change final drive ratio.

Tyre size does have a role as it affects the rolling circumference of the wheel. This doesn't have as much effect as one would think because the difference in circumference between a 155/80R13 and a 205/40R17 is negligible.

A 1.3l engine will have the same theoretical top speed as a 2l at the same rpm limit. The only difference the engine makes is how quickly or slowly one reaches that speed.

Modified engines can be faster if the *rev limit* is raised up from stock settings, thus the increased revs can increase top speed.

In an ideal world take 2 identical cars with the same engines, gearboxes, tune, tyres, etc. they would both achieve the same speed on a top speed run. Take one car and modify the engine for increased power and the other one change the gearbox for one more suited for high speed( longer final drive ratio). The stock engine will win due to the better gear ratios. Take the same 2 cars to a drag strip in their current state, the one with the improved engine will leave the other in the dust. Increased power improves acceleration and will result in quicker 400m times. The 2nd car will actually do worse on the drag strip than when it was stock.

Two types of races that measure different aspects of a car's performance, require very different kinds of changes to get the required results.

[mk2-phreak]

Now I've seen it all. Modified Flywheels affect rpm at a given speed and gear ratio

[chucker02]

Now I've seen it all. Modified Flywheels affect rpm at a given speed and gear ratio

[gt'79]

ended up taking 3 clutch plates to have it rebuilt.......all got oil on them...explains the change in ratios lol

anyways, will keep you guys posted in my build thread

[PapaJo]

ended up taking 3 clutch plates to have it rebuilt.......all got oil on them...explains the change in ratios lol

anyways, will keep you guys posted in my build thread

Do the oil seal on the gearbox input shaft and rod seal and brass insert now to prevent doing this job again.

[gt'79]

ended up taking 3 clutch plates to have it rebuilt.......all got oil on them...explains the change in ratios lol

anyways, will keep you guys posted in my build thread

Do the oil seal on the gearbox input shaft and rod seal and brass insert now to prevent doing this job again.

got myself the Elring seal kit.staying away from those cheap seals

[PapaJo]

Elring seal kit for crank side, yes. I mean do the brass bush, small seal on rod and input shaft seal on gearbox as well.