Mythbusters.

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Abnormal
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Re: Mythbusters.

Post by Abnormal » Thu Jan 05, 2017 4:23 pm

So forget leverage,
So lets say the friction is constant because its the same size of pad and caliper and brake booster and brake fluid friction in the lines and leg muscles.
For a standard disc of 239mm the circumference is 1501mm
Now for a larger disc of 280mm the circumference is 1759mm

Given that the same frictional force is being applied to the disc constantly in each case (friction)
with the standard disc you will be applying the force over a distance of 1501mm x (friction)
with the 280mm disc you will be applying the force over a distance of 1759mm x (friction) for each rotation of the wheel.
a difference of 258 (friction) per wheel rotation.


Maybe you need to fit a set and check out the placebo effect for yourself. :)
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Re: Mythbusters.

Post by Golfdriver » Thu Jan 05, 2017 4:34 pm

Lets forget about the fact that the mass is higher and the friction is constant regardless of the diameter and just say 'I give up"
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Re: Mythbusters.

Post by Abnormal » Thu Jan 05, 2017 4:53 pm

Let us know after you have done an actual test to confirm your maths. (Do a test with a bicycle wheel even)

I opened my textbook Work done = force x distance.

You need to realise that you are stopping the whole car not just the disc, the increase in mass is negligible here.
(the extra weight wont benefit the handling though).

Friction between the pad and the disc is constant.
Since the friction will be constant and it will be applied over a greater area for each rotation of the wheel there will be an effect on
friction between the Tyre and the road (assuming you have not hit the limit yet)

Golfdriver wrote:Lets forget about the fact that the mass is higher and the friction is constant regardless of the diameter and just say 'I give up"
So now what if your bigger discs that are lighter? ( alloy hats)
Manufacturers must be nuts to put bigger discs on the faster cars then, or maybe its just marketing gimmicks?
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Re: Mythbusters.

Post by Golfdriver » Thu Jan 05, 2017 5:04 pm

The lighter the disc the quicker the same friction will act on it. This we agree on. This is the only reason that carbon discs are used in top formula racing in dry conditions. For the rest, you win. I am beaten. I know this because I feel beat. And if my engineering professor was still alive I would go and tell him what an idiot he is based on your irrefutable conclusions.
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Mythbusters.

Post by Neuk » Thu Jan 05, 2017 6:09 pm

Abnormal wrote:So forget leverage,
So lets say the friction is constant because its the same size of pad and caliper and brake booster and brake fluid friction in the lines and leg muscles.
For a standard disc of 239mm the circumference is 1501mm
Now for a larger disc of 280mm the circumference is 1759mm

Given that the same frictional force is being applied to the disc constantly in each case (friction)
with the standard disc you will be applying the force over a distance of 1501mm x (friction)
with the 280mm disc you will be applying the force over a distance of 1759mm x (friction) for each rotation of the wheel.
a difference of 258 (friction) per wheel rotation.


Maybe you need to fit a set and check out the placebo effect for yourself. :)
How can you simply forget leverage?

The calculation you have started, relates to the potential work that can be done by the braking system and not the instantaneous rotational force or torque that it can apply.

In order to calculate the torque applied by the braking system you have to take the caliper distance from the centre of rotation in to account. I'll make my argument as simple as possible by posing a question, is it easier to open a door closer to or farther away from the hinge of the door?

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Re: Mythbusters.

Post by Abnormal » Thu Jan 05, 2017 7:33 pm

I agree less force is required to open the door at the outer edge.

Said let's forget about it as golf driver said it's not a factor in the equation.
Yip it was work done.
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Re: Mythbusters.

Post by Neuk » Fri Jan 06, 2017 8:29 am

Abnormal wrote:I agree less force is required to open the door at the outer edge.

Said let's forget about it as golf driver said it's not a factor in the equation.
Yip it was work done.
Sorry, I was replying on my phone and thought that the post you made was made by Golfdriver :oops:
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Re: Mythbusters.

Post by missioner » Fri Jan 06, 2017 6:11 pm

Myth: mothballs will boost the octane rating of your fuel.
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Re: Mythbusters.

Post by Abnormal » Fri Jan 06, 2017 6:23 pm

missioner wrote:Myth: mothballs will boost the octane rating of your fuel.
Depends on date of manufacure

:troll:



Apparently some would burn but I don't know if they could actually inrease the octane rating.

Edit
http://mythresults.com/episode15
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Re: RE: Re: Mythbusters.

Post by missioner » Fri Jan 06, 2017 7:34 pm

Abnormal wrote:
missioner wrote:Myth: mothballs will boost the octane rating of your fuel.
Depends on date of manufacure

:troll:



Apparently some would burn but I don't know if they could actually inrease the octane rating.

Edit
http://mythresults.com/episode15
When I was a kid the ballies would brag about racing their Cortinas with moth balls in the tank, my neighbourhood was predominantly Post Office, NPA and Spoorweg employees. So as you can imagine there was a lot of Fords and Klippies.

What I was wondering was if there was any validity to their statements and if the same is true today, or has the chemical composition of the naphthalene balls been altered to reduce their flammability?
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Re: Mythbusters.

Post by dubz-on-drugz » Tue Aug 29, 2017 4:00 pm

I love this thread !!! So many myth I have believed till now

What I believed !

1) moth balls in tank
2)vr6 tb makes more power
3 ) 20 % tol and xyl makes a higher octane .
4) knocking the Fpr for higher pressure .

What I also heard


X) exhaust that is too big will make u lose power
X) 8valve long intake makes more torque
X) 2e crank is better used for turbo vs ady as 2e is a steel crank ?
X) there is always a mk1 faster then u ...lol

Nice one panic !!!



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Re: Mythbusters.

Post by DJ7 » Fri Nov 17, 2017 3:46 pm

One of the best threads I have read in a while on any forum.
Current:
His: '05 VW Golf 5 2.0 TDI Sportline
Her's: '13 Audi Sportback 1.2 TFSI Attraction
Ex: '97 Astra Estate 200i
Ex: '00 Corsa 200 GSI 16v
'96 Astra 200i E 16v
'02 Corsa 160 GSI
'93 Ballade 160e
'95 Astra 200i E 16v
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Re: Mythbusters.

Post by Smok3X » Thu Jan 04, 2018 8:43 am

But where is Panic Mechanic...

We need his input!

Mythbuster thread is not the same without PM
Current:
Leon CUPRA - 2.0TFSi K04--> Rides Thread
[email protected] Artz - Stock
[email protected] Artz - RevO 2+

Ex:
Ibiza CUPRA - 1.8 20V - Hybrid Turbo-->Rides Thread
Revo:182KW and [email protected]
ABF Citi Golf - 2.0L 16V--->Rides Thread
FRC - 124KW and [email protected] Trix
1/4 Mile:14.61s
1ST Place - 4AF2 Margate 31st Oct 2010

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Re: Mythbusters.

Post by Stu » Fri Jan 05, 2018 7:37 am

Smok3X wrote:But where is Panic Mechanic...

We need his input!

Mythbuster thread is not the same without PM
hopefully working on my car :D
Polo 20VBigT - The Redhead
Kia Sportage - The Silver Surfer
C63 507 Edition - The Dragon
Rustler Bakkie - Good Old Jimmy

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Re: Mythbusters.

Post by The Gti Guy » Wed Jan 24, 2018 9:46 am

Hi, Guys

I live all the way down in the Mother City. I will post specs and power figures then you guys can let me know if its about right.
2.0 8v
Ady stock bottom end
X-Flow Head, ported and flowed
Rowland 43mm x-flow intake
Toyota 43mm rsi throttlebodies
282 estas cam + vernier
57mm 2 box powerflow exhaust
Dicktator Std Management
Surge Tank
New Fuel Pump
FPR

Car made 120kw and 201nm these are flywheel figures. To me they seem about right. However I have encountered another golf and argue with this guy to the day that his figures is impossible. Here is is list:
1.8 carb 8v
Angle cut swirled valved
Head is ported and flowed
282 estas + vernier
36dcd carb jetted by Rowland
50 into 57mm exhaust

His car made 109 wheel kilowatts and 225nm that is converted to flywheel kilowatts is 126kw even more then me I am saying its impossible yet he still argues. Whats your take on this?
Note: Cars was tuned at different places.

Now we knows what performs best hahaha

Kind Regards
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Re: Mythbusters.

Post by Neuk » Wed Jan 24, 2018 9:57 am

What were the power figures ATW? ATF readings are notoriously useless.
Nic

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Re: Mythbusters.

Post by missioner » Thu Jan 25, 2018 7:05 pm

With the right head work and fueling a 1.8l carb motor can be pretty strong.

There was a Toppie I lived down the road from as a teen, he had a MK2 Jetta rally car. The engine was a stock (ish) 1.8l bottom end with a ported Kjet head bolted to it. It had a Shrick cam (Deg unknown) and 3 angle valves with some other tricks. He said the valves were swirled, not sure what that entails.

Fuel was delivered via Weber sidedraught carbs, apparently built by Pat Duckham (Google him). The exhaust was also built by another old timer exhaust fabricator that had retired by then, it was a hand bent, heat treated steel branch with a one box 54mm system.

The car running battled to idle under 1500rpm and revved up like a Suzuki GSX. He took me for a drive in the thing and it accelerated like few cars I've ever been in.

I won't ruin my story by guessing how many killerwatts this car made, but I will say that I believed that car could and did give many bigger engined cars a proper hiding.

Moral of the story is don't disbelieve a smaller capacity engine making nice numbers on a dyno, it's very possible.
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Re: Mythbusters.

Post by PoloMike » Mon Jun 18, 2018 1:13 pm

panic-mechanic wrote:
Tue Jan 05, 2010 8:04 am
Right - first off - cross drilled discks. YES they do work - what happens with pads meant for street use is that when they are abused and get vey hot they basically give off a gas which in effect gets trapped between the pad and the rotor. Having the holes in them allows this gas to escape and effectively improve the braking(it doesn't cool the rotor more). Same reason for slotted.
BUT the problem is that drilled after being cast rotors always tend to crack around the now drilled holes. Slotted rotors last better but they eat pads because the slot basically acts like a skimming machine blade evertime it passes the pad.
So the best answer is - it you want to race - fit racing pads and a rotor big enough to dissapte the heat - the problem with those is they don't work when they are cold - so the first time you have to brake they are pretty much uneffective.

Good flat pad filters will allow better breathing - this normally means more power which rarely means better consumption. These do come with a warning though - I don't like using the freeflow type filters(they are all cotton pad with oil) on cars that have a hot wire MAF. These filters do allow some of the oil and fine dust through and more problematic - water vapour and all of those items are not good for MAF longevity. My advise is - Hot wire MAF - leave you paper filter and stock airbox alone...

The only time a BIG throttle body is going to give more HP is if the current one is too small. That rarely happens and all you achieve is basically having the engine get it's full throttle air in by the time you have opened the throttle partially. There are 'some' merit in running a bigger TB when you are running a turbo car and have sufficiently large airflow. But that basically means all your plumbing from the cooler etc. also have to be big enough. Putting a VR throttle body on a 1.4i will not score you even half a HP. If you want better flow concentrate that work on the cylinder head and around the valves.
A couple years late but none the less, with regards to the big throttle theory, an N/A motor will only pull the same amount of air through a throttle body equivalent to the size of the intake valve. You can have a 35mm intake valve and a 100mm(exaggerated) throttle body, the valve will only allow 35mm.
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Re: Mythbusters.

Post by Xavier » Thu Jul 12, 2018 10:50 pm

Need help my 1.4i velociti
Starts but when warm it’s cuts out when pushing the gas.
Their fuel and spark
I replaced the fuel pump
Checked the ecu
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Re: Mythbusters.

Post by Yakuza Racer » Tue Jul 31, 2018 3:52 pm

Xavier wrote:
Thu Jul 12, 2018 10:50 pm
Need help my 1.4i velociti
Starts but when warm it’s cuts out when pushing the gas.
Their fuel and spark
I replaced the fuel pump
Checked the ecu
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Please post here:
https://www.vwclub.co.za/forum/viewforum.php?f=3
Mine: Jetta 6 TDi
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Re: Mythbusters.

Post by Dub rox » Sat Sep 22, 2018 8:49 pm

missioner wrote:With the right head work and fueling a 1.8l carb motor can be pretty strong.

There was a Toppie I lived down the road from as a teen, he had a MK2 Jetta rally car. The engine was a stock (ish) 1.8l bottom end with a ported Kjet head bolted to it. It had a Shrick cam (Deg unknown) and 3 angle valves with some other tricks. He said the valves were swirled, not sure what that entails.

Fuel was delivered via Weber sidedraught carbs, apparently built by Pat Duckham (Google him). The exhaust was also built by another old timer exhaust fabricator that had retired by then, it was a hand bent, heat treated steel branch with a one box 54mm system.

The car running battled to idle under 1500rpm and revved up like a Suzuki GSX. He took me for a drive in the thing and it accelerated like few cars I've ever been in.

I won't ruin my story by guessing how many killerwatts this car made, but I will say that I believed that car could and did give many bigger engined cars a proper hiding.

Moral of the story is don't disbelieve a smaller capacity engine making nice numbers on a dyno, it's very possible.
Swirl pollished valvesImage

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Re: Mythbusters.

Post by missioner » Sun Sep 23, 2018 6:55 am

Thank you. Those look nice.
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Re: Mythbusters.

Post by Dub rox » Tue Sep 25, 2018 12:36 pm

missioner wrote:Thank you. Those look nice.
No problem. As to what the advantages this has as to polliched or plated and flowed valves is a mistory. Guess opinions differ...

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