Toms RCR 40 Trackracer

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good info about the Quaife LSD, I was also thinking about such diff in my Hartge, but some diff builder says that my car deserves a good plate diff with strong internals and 6 plate sper (lsd) 40%...but the I said, yeah thats nice when you want to drift and slide but going around corners with power the car wants to go straight and so under-steer...
And I don't do drifting or sliding (only when it happens I make it a good one ;-)) so I guess I will be better of with a Quaife on a circuit, then with a 40% special sper(lsd) ? I hate under-steer :) and I guess a Quaife is faster and less under-steer around the corners.
 
For track purposes i ordered a set of light weight racing wheels. Initialy i wanted to go with BBS, but their uncertain 3-4 Months leadtime scared me off.
So i looked around for alternatives and finaly decided on a set o FIKSE WHEELS.
I contacted the sales rep Dany Goll. After clarifying the critical dimensions id decided for their Profil 13 wheel. The wheels where ordered and delivered five weeks after that.
I can only say the best about the service i received.

The dimensions are 12*17 rear and 9*17 front. Offset rear is the same as on my 15´s . On the front i let the additional 1" grow towards the center of the car.
The forged aluminium center is CNC milled and anodised in black, The wheels are very light, I wheel give a report about the difference in unsrpung weight as soon i have the tires mounted.
As the RCR40 is using C4 hubs the PCD is standard 4,75 * 5. THe wheels bolt right on the 5 studs after unbolting the central lock adapter. Even with the shortened studs i still have 14mm of thread to engage in the lug nuts.
Plan to go with gorilla black steel lug nuts. If anyone knows about other nice machined black lug nuts (m12*1,5) please tell me.

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Tires will be Nitto´s NT01´s 235/40/17 front and 315/35/17 rear

TOM
 
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Chuck

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Tom

This has nothing to do with wheels. But you sure did an excellent job fitting the body. Those seams look perfect. Excellent work.

Chuck
 
wow...those wheel lips are wide...looks nice,
but when you do hard cornering there will be a lot pressure on them me thinks.
 
Gtrene, I have a Quaife atb diff in my 40 and it is only driven to track, raced and then driven home. Compared to plate type LSD it is completely smooth and you can't even tell difference to an open diff. No understeer on turn in and fantastic corner exit traction even at full throttle in 2nd gear. No inside wheelspin at all. Does get some mid corner part throttle understeer however, but I still have only tried a couple of wheel alignment settings so far. Guaranteed for life, road or race too! Mine is in a Porsche 944 type trans not a g50, but should be similar behavior I think.

Tom, love your work!
 
Just started looking at your build.
A real engineer thats what I like to see.
Dont buy it make it yourself attitude, well done mate.
Love the colour , looks good with the black wheels, good choice.

Regards
Keith

Southern GT
Knight Racing Engines
ZFQ
 
Update:

Have managed to adjust the suspension more than just with the long ruler, which has been my current setup activities so far.
I build my self a rig for stringing the car. I will go to a full 3d suspension alignment shop later, but i wanted to learn about how the car reacts on adjustment first in my workshop.
I set up the strings parallel to each other and centerered and parallel to the chassis ( if you look into on of my first post in this threads you see that this was also the starting point of the build ). THe strings where set about 7 inches apart from the sill panels. With the Kite string i´m using i can go as exact as about 0,5mm.

The initial measurement of my rough build set up(with a long ruler and a big angle , with which i drove around for 500km was the following:
FRONT:
Toe in 2,5mm
Camber FL: -0,4°
Camber FR: -0,2°
CAster FL and FR: 5,5°
REAR:
Caster RR: 7,2° CAMBER 0° Toe in 3mm
Caster RL: 6,5° CAMBER 0° Toe out 1mm

Wheelbase ( measured rim to rim). 92,3 " right side; 92,2" left side;
Axel staggering front to rear < 2 mm

This was achieved by only counting rod joints thread during installing and making them the same both sides ( found out that i counted wrong on the rear, thus the difference in toe). That means in also that the chassis and all the related suspension components are done on a precision level which is realy amazing. My son works in a porsche dealership and does a lot of suspension alignements there. He reports that even on brand new porsches ( even top range GT cars) axle staggerings of about 5 mm is not seldom to see.

I did adjust the suspension to the following datas:
FRONT:
Toe out total: 1,5mm
Camber: -1,2° left and right
Caster: 5,5° left and right
REAR:
Toe in total 1mm
Camber: -1,0° left and right
Caster: right 7,2° left 6,5° ( didn´t dare to change this ,because on the rear the influence is not so big, but i will change it to the 6,5° value in the right side as well)

Still have not done anything with the swaybars. Front and rear are still adjusted to their softest position.

THe car behaved already pretty good with the initial setup, but it had to less feedback to me. With the new setup it is a complete different animal. Turns in where and when you want, it feels much more planted and predictible. stays straight in heavy braking. THis was the first time i felt i could go faster in that car as with my S-Line A4 on 18"´s. So i went to one of my favorite places where is one turn which i manage with my A4 with 115 - 120 km/h(according to speedometer) with oversteer on all 4 wheels. I tried it two times and at the second attempt i went through with the GT at 125-130 km/h(GPS verfied) with no issues at all. Probably would go through with another 5 -10 km/h faster, but a public street is not realy the place to try.

I also had for the first time set the rev limiter from 6000 to 7200 RPM. Have to do some carb tuning as it on the limit to be to lean at full rpm. so will increase main jets a bit. Having now roughly 750 km driven on the car i get a feeling for it more and more. BRakes are getting better and better, but i will change the masters from currently 1"(rear) and 7/8"(front) to 7/8"rear and 13/16 front to have a longer pedal travel and less force needed ( could go probably down to 13/16 and 3/4 as well, but like to do it step by step). With the EBC Bluestuff pads, they block whenever i want, but the pedal travel to achieve this is pretty short and as on my racebikes i like it a kind of longer travel with less force needed, to have more feel for it.

Also have changed the main crankshaft pulley to smaller one. went from a 4,5 " to a 80mm diameter. With this the waterpump is now 80% underdriven and also the alternator si not as stressed with the high RPM´s. As a result the engine runs an average of 15°F cooler than before. Not even goes to 195°F even in heavy traffic with and with the license plate blocking almost 25 of the opening in the front.
Will check the sensor once again to make shure that this is correct.


TOM
 
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Hi

I have changed my central muffler to 2 single ones. 4" diameter and 400m long each. I also fabricated endpipes which are incorporating baffled tubes, to take away a little of the agressive note.
before installing the mufflers i also mounted a heatshield towards the gearbox. This is one thing i strongly recommand. When i runned it without the gearbox cooler in automatic mode will kick in even after a smooth drive , means that oil gets at least 85°C ( if have a 85°C/75°C thermostatic switchin the diffhousing) . With the heat protection it does only kick in after some ambitous driving. The heatshield is a 2 layer aluminium product which can easily be cut with a pair of scissors, and also easily be formed. It is mounted with cable ties.
The mufflers itself are 2,5" units mounted with springs only. In the rear i have made u-shaped holds where the mufflers are just laid in and clamped with a springloaded band. THe mufflers are headerwrapped at that point to avoid scratching and allow for moving due to heatextension.
I opted for this kind of mufflers because they are lightweight and can be refilled.
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TOM
 

Randy V

Moderator-Admin
Staff member
Admin
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Nice work as usual Tom. How do you like the sound of the twin mufflers? Are they much louder than the single muffler was?
 
I have finished the installation of my doorboxes. Made a block off plates out of aluminium. Like the look, it matches the one of the center console.

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TOM
 
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