best lightened flywheel weight, and mpg query

[dub-gti]

as title, getting hot golf to run me a flywheel down on a lathe, but reading some posts across different boards, some think having a lightened flywheel ruins drivablity other then on full throttle, now i drive sensibly when my kids are in the car, and then a bit more sprited on the back roads (70mph roads) so what weight is going to be best to go down too? i cant off the top my head remember the correct weights but iirc its 5.5kg stock and 3.5kg is safest reduction. so with me planning a 268 cam, enlarged tb (to max size possible) will i run in to trouble with drivability?


also as a side question, since putting a induction kit on im running as low as 11mpg, and looks to be running 14/18mpg when full throttle and then it says 24 when i drive with a feather foot. now when i got the car it was 34mpg and 25 full throttle, should i go back to the box with a panel filter? i quite enjoy the induction noise. would a vagcom bring any thing up??? only things other then the filter is the pipe coming from the inlet is let to air and i moved (what i believe to be the air temp sender) up a little towards the tb, about 6 inches from original position.
bit confused

[VW BUSH]

Std box is best with free flow filter and proper air feed mods.
Drilled box sounds good but lowers mpg and power through high air temps under the bonnet so no holes imo
Why not go half way on the flywheel and only lower mass by 1kg, best of both worlds

[danny_p]

02A flywheel, take all the weight you can off it, they weight nearly 10 KG,  took the one in my mk2 down to 5.5 - 6 kg  and would have gone lighter if i chould have.  drivablity is fine

[Stirring Moose]

Basically I would think you will lose some drivability with the combination of cam, TB mod and flywheel but not absolutely sure how bad. 268 cam doesn't sound too mental so that shouldn't give too much hassle. Not sure about TB. As for flywheel, a mate of mine did a beautiful one-off aluminium one for a 2.5 N/A Scooby. That spun up like a superbike and was a bit edgy to drive, but that 'wheel was right down at 2.8kg including the ring gear. 3.5kg shouldn't be too terrible.

On the fuel consumption side, those figures sound weird. Have you actually done a "manual" mpg check i.e. brim it, note milage, drive it for a while then brim again and check fuel used against miles done? If the computer's right, your car is now using twice the amount of fuel it was and thus either running heroically rich or if it isn't, it must be successfully burning it all and producing truly epic amounts of power. If it's doing neither of these things I would smell a (possibly electronic) rat, maybe due to the moving of the sensor.

S.M.

[dub-gti]

o2a? i have a abf engine. im not to fussed on idle, just dont want what ive been reading, ie loss of drivability, i dont mind having to shift quicker, or changing my style of driving to compensate the lighter fw when pulling away.

infact i had a honda civic, the square back 1.5 vtec ones, and that had a lightened flywheel and i stalled it a few times when i first got it back got over it and never caused me a problem after i got used to it!

[dub-gti]

On the fuel consumption side, those figures sound weird. Have you actually done a "manual" mpg check i.e. brim it, note milage, drive it for a while then brim again and check fuel used against miles done? If the computer's right, your car is now using twice the amount of fuel it was and thus either running heroically rich or if it isn't, it must be successfully burning it all and producing truly epic amounts of power. If it's doing neither of these things I would smell a (possibly electronic) rat, maybe due to the moving of the sensor.

S.M.

well. with the filter on it does pull stronger 0.5k sooner, i did think to my self maybe as its sucking more air and being less restrictive its buring more fuel. but being over double consumption ill have to get back to that, tomorrow im going to brim it again, drive around till friday and then do so again. then ill get the numbers and find out.

i know my driving style and the condition i drive causes low mpg any way, my work is under a mile away, kids school is 2 miles, and tesco being about 4 miles, then my dads, and wifes mums house about 6 miles each away. so in all my car never really goes further then 15 miles in one day, maybe 30 miles if im busy but not constant driving, i never go on a motorway and if im on my own will have my foot down 1st and half of 2nd gear 50% of the time, so i know thats killing mpg.

also what i need to observe from today is the fact my rear tyres were some how 9psi, with one front being 13psi. now im sure i checked the pressure the other week so i dont know how long theyve been on those pressures or if some c**t let them down but only noticed this morning!

so going to need to see, at one point it stated 7mpg!!!!! so i think something is fooked some were.

now i want to get this mpg sorted before getting a lightened fw or cams!

what sensors predict mpg? has the one fitted to the airbox got any correlation or is this just a air temp sender?

[thai-wronghorse]

It's no wonder its drinking petrol with tyre pressures that low, that coupled with all those short journeys and flooring it in first gear.
For starters get those tyres pumped up correctly, then check to see if the engine is warming up properly (gauge sitting at 90), next get it tested using Vagcom to see if any fault codes spring up as those mpg figures are appaling and would suggest a problem somewhere.
When was it last serviced as well?

[tshirt2k]

You need to say what gearbox you have. That determines flywheel weight. An 02a will get down to around 5.5kg but an 020 will go lower at below 4kg.

It won't affect it much apart from from making it rev quicker.

[Seanl]

I had my 020 lightened by hotgolf. Pretty much the same weights as the 02a ones above, was over 10kg before, and 5.1kg when I got it back iirc. I hadnt been driving it for about 2 months prior to refitting it all, so it made absolutely zero difference in feeling etc to me! Its just like driving a different car, when you first get into it, you have 5 minutes adapting to the way it drives. After that, its second nature. Did seem to rev more freely, and though it made absolutely no difference in torque low down. 

[dennis10]

I had my 020 lightened by hotgolf. Pretty much the same weights as the 02a ones above, was over 10kg before, and 5.1kg when I got it back iirc. I hadnt been driving it for about 2 months prior to refitting it all, so it made absolutely zero difference in feeling etc to me! Its just like driving a different car, when you first get into it, you have 5 minutes adapting to the way it drives. After that, its second nature. Did seem to rev more freely, and though it made absolutely no difference in torque low down. 

I second exactly this.

Had mine done about 6 months ago, best mod I've ever had done.  There isn't a downside to it.  As Seanl said, it takes about 5 mins to get used to it, then you carry on like nothings happened.  Mine was about 10kg before and 5.5kg after, so a hefty chunk taken off.

In a bit more detail, the differences I noticed were quicker engine braking, meaning less use of the actual brakes, so I can take my foot off the brake and it loses momentum much quicker, which isnt a bad thing when you want to coast.  This has improved my mpg.  I have to keep my foot on the acccelerator pedal a bit more to maintain momentum when cruising, but this has no real effect on mpg.  Overall my miles to a tank havent changed, but the way in which I gain and lose the mpg has.

Of course acceleration is much improved, which is what we all do it for isnt it?    Get it done, VR6 clutch at the same time and think no more of it.  It should be like this from factory in my opinion.