Black magic Mk5 GTI track car

[danishmkvgti]

Fuscobal since you are going back to stock; are you considering selling the car?
 

[xht20]

Jake, i'm 100% sure that he is not selling the car. He is just transforming it into a dedicated track weapon :D

[fuscobal]

I removed the audio system to loose some weight and because I didn't listen to it anyway since the car began to be used only for track days after the little Polo GTI arrived. 2 years ago, my car had about 1680Kg with me inside and a full tank of gas. Now, it will have about 1450Kg wich is a huge 230kg of weight loss !

[fuscobal]

Time for some updates. The car is at my mechanic since the last track day (5 months ago) and still not working. Afterresurfacing the engine block and installing the JE pistons & IE rods (10.5:1 & 83mm bore) everything seemed fine. All water plastic pipes were replaced with new OEM ones and the rubber with the Forge silicone kit. Unfortunately, Forge only replaced the upper lines (the ones that can be seen) like they are for cosmetic purposes, not better performance. For the lower ones I had to use new OEM ones. I've also replaced all gaskets and the important bolts. As for the gearbox that was having a 4-5mm play on the input shaft, we added 2 spacers and the play was gone. After all was put back together, the gearbox was making a terrible noise so we had to open it up again. We found that the new input shaft bearing that was just installed was defective from the factory and we also removed one spacer because the position of the pinions was changed. The gearbox was put back onthe car and the noise dissapeared and it seemed to change fine under normal driving. However, strange noises on the engine this time, made us open the engine again. We found out that the cylinder head was also deformed and the valves were leaking on 3 cylinders. I've sent the cylinder head for resurfacing, replacing the guides and reworking the seats. The cylinder head is ready now and will be put on the car next week. Hopefully it will all be fine this time. I have some worries regarding the valve seats and guides. Since new guides cannot be ordered separately from the cylinder head (wich would cost a fortune), the guy that took care of the cylinder head had to use guides from another VAG car. Don't know what car and if Vw uses the same alloy for guides on 60HP cars as well as on 200HP cars. I don't know how well the new guides will take the heat ! He said all VW guides fail in time, no matter the power of the car but I'm not sure if it's like this. Anyone knows what influences guides failure on these cars most ? (by failure I don't mean they break but the develop play so they won't guide the valves well)

[fuscobal]

Time for some updates. Took the car from my mechanic abouth 1 month ago and it's working fine, except for the same rough idle who seems to never go away. There's some sort of a cyclic noise at idle and don't know why but while on the road the car behaves normally. Didn't have the change to WOT it yet but will do it after installing the wing....wich reminds me of the second update :)

The custom Reverie wing came and it's very well manufactured. After talking to Reverie guys, they advised me to go for the smaller 150mm profile instead of the 225mm one. They said it should be enough for a FWD car and that a larger one would ruin the balance of the car unless I also have a large splitter in front. The wing was made with a span of 1300mm and a 515mm distance between the drop tabs. After speaking to the guy designing the mounts, he said we can't use the car's hinges of the trunk lid so I've distanced the tabs 50mm from the hinges on each side. Didn't weigh the wing yet but it seems to be about 7-800grams only !!!



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By interpolating between 1245 si 1400mm, at an AOA of 10deg, we get about 43kg@100mph. From an older post over here, the wind tunnel says the OEM GTI has -2kg on front si -37kg on rear @ 200kmh. Those values mean the car has lift at high speeds(but then again most street car have lift). Knowing I'm lowered about 1'' and I have the VWR front air-dam, the real values on my car might be a little better, say +5kg on front and -30kg on rear. In order to compare the downforce brought by the wing and the values we have for the OEM car, we need to calculate the wing's value @  200kmh. 43kg*(200kmh2/160kmh^2)^ = 67kg . So, at 200kmh, the car should have about 0 to 5kg of downforce on front and 30-35kg on rear (67-30 = 37 but I'm considering less because the wing's data has been acquired under freestream and not disturbed air like on the car) !
 
PS : For those wanting to compare the downforce level of a track-prepped street car and an F1 car, at 200kmh I would have about 1450kg and 40kg of downforce (2.8% of the car's mass) and a formula 1 car would have about 700kg and 1400kg of downforce (200% of the car's mass !!!). I think it's easy to understand how an F1 car can generate such tremendous downforce levels, knowing that the downforce does not generate inertia !

[rex]

That rear wing is very, very sexy  .
I wish I had no engine problems so that one of these would be in my garage right now...
I am curios to see how you make the mounting points.
Keep up the good work!

[the bruce]

 

Agree with your calculations and estimations.

Hope it works well and the engine does too.

 

[fuscobal]

Will come back with pics once everything is ready ! As for the engine I'll have to do another check to see what's with the rough idle. Don't want to risk anything after what happened to me on Hungaroring. BTW, it seems the Evoms heat shield was touching the plastic water T-piece that broke so I had to cut a little bit from the shield to clear the pipe !

[fuscobal]

Because I wasn't inspired to measure the distances and diameters of the holes on the drop tabs of the wings, I had to approximate them by measuring on the computer's screen and suipposing the 3 small holes have 6mm in diameter. At first I did not understand how can the 3 inclined holes pass through the same point on the mount tabs while rotating the wing around the elongated hole. After making a quick drawing in Acad, I understood that if you rotate and translate the wing around the elongated hole, it is actually possible >



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From the pic it can be seen that it's possible for 2 fixed points found at a distance X one from each other on the mount tab that I will manufacture to be on every one of the 3 inclined holes if the axxis between them will rotate and translate at the same time (the 3 values are different because of the way I've measured the distances on the computer's screen instead of on the wing itself). By measuring the angles between them, one can see that between the min and max position there's about 5 deg. At first, I told the guy to install the wing in such a manner that the min position is 0 deg for street driving and no drag. However, after drawing, I realised that a min of 0 would mean a max of 5deg wich is too little. Thus, I will establish the min position at 4-5deg so that the max can be 9deg. (the drag and absorbed power for this wing is not something too scary  > about 3kg and 2HP)

[the bruce]

the drag and absorbed power for this wing is not something too scary  > about 3kg and 2HP

Indeed nothing to worry about.

When you do the invest in such a wing the main point is you get the downforce to want on track. 

Increasing fuel consumption by 0.1 or 0.2 l per 100 km - 

Nevertheless in turbulent air things are quite complex. Promises and estimations are hard to make.

[the bruce]

Any news already?

I'm currently about to read this book - maybe it's somthing for you as well:

http://www.bentleypublishers.com/automotive-reference/engineering-and-motorsports/race-car-aerodynamics.html

You might also get some inspiration from in this:

http://www.mk5golfgti.co.uk/forum/index.php/topic,59674.msg669054.html#msg669054

[fuscobal]

Sent the car to have the wing mounted in nov but didn't hurry too much because I don't use the car during winter. The guys first removed the OEM plastic add-on of the trunk lid (the add on can only be found on GTI, not on the regular Golf 5) and it weighed in at 2.2Kg. Knowing the wing is only 0.95Kg at wich the aluminium mounts will be added, I'd say at the end I might end up with the same weight as before. Some pics with my newest calculations :

1) Cross-sectional area of the wing + drop tab > made this to find out the relationship (angles) between the holes on the tab and the median line of the wing profile in order to know how I need to establish the holes on the mounts in oredfer to get the desired angle



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2) First option with the 2 holes parralel to the ground wich ensure a setting of the wing relative to the airflow of 4.9 to 10.2deg at max position



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3) Second option with the rear hole 3mm higher than the fron hole ensures another 2 deg, so 6.9 to 12.2deg (at more than 14deg stall occures so I should stay here for best downforce/drag compromise)



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[fuscobal]

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[fuscobal]

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[fuscobal]

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