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ScaleAuto "Racing" Series 991

I already I took this Home Series ScaleAuto Porsche 911 GT

[Image: porsche1.jpg]
And gave it the bench tune treatment. - you can read the article HERE
Now I open up the "Racing" version of the same model of car.
[Image: porsche21.jpg]

[Image: porsche22.jpg]
So what is the difference, what do you get for that extra 10 quid or so.

The front hubs are press-on plastic as before, but the rears are alloy with M2 grubs. Both pairs of hubs
measure 17.2 x 8 mm at centre, and with original
tyres fitted, measure 19.65mm O.D.

[Image: porsche23.jpg]

This is a podded angle-winder powered by ScaleAuto's 20k standard FK-180 motor that has 285g/cm of
torque - which equates to about 14 watts power.

- As comparison the yellow can Flat-6 fitted to their GT and LMP cars is 21k with 200 g/cm,
torque for 10.5 watts; the standard NSR King is 14.4 watts,

- (21k but slightly less torque), and the Boxer-2 is 21.5k with 340 g/cm torque for 18.3 watts.
So it sits mid range among GT cars for overall power, and should be legal in most clubs GT classes
- do check your local rules.

[Image: porsche24.jpg]

I would describe the chassis as a "medium", not hard, but not super flexi like for plastic tracks.
The pod is rigid as needed for my
wood track racing.

The chassis exhibited a bit of end-to end bow ex the injection molding process; so I did the usual,
giving it a hot water bath on the magnet plate.

This only needed one pour of boiling water, as it came out pancake flat once the water cooled.
Gearing is 11:27, an in similar fashion to the Home Series
car, red grease had been applied to the
gears, and the motor either run, or turned manually to
distribute this.

[Image: porsche25.jpg]

There is a fair bit of substance in the pod design where the corner of the motor mount section flows
into the drive side axle bearing holder, and the motor is
fixed into the pod with screws both sides.
I am hopeful this will work well on high grip tracks without additional bracing.
I have removed the small magnet that
sits at rear of the pod below the axle, as it adds more
weight at the back of the car,  and angle-winders are already more tail heavy than is optimal on most

tracks for wood racing.

On plastic, you probably want to retain the magnet, as the motor is closed-can with almost nil
down-force (5 g/cm)
A light-weight stopper near right rear wheel the prevents lateral movement
and ensures the gear mesh doesn't alter once set. When unboxed, there was
about 0.5mm lateral
movement. When I saw Europeans setting up cars for plastic track I was told this is normal;
preventing anything locking up, and helps
with the cornering. - I don't like this arrangement for wood
tracl racing, I adjusted it to just free spinning, ie no lateral
movement at all.

The guide is "stock" similar size to those fitted to most other good hobby brand cars as standard.
Unlike the Home Series car, this had no axle height inserts.

Instead, it came with grub screws already fitted as per our more common tuning conventions.
The braid was that hard stuff for plastic track, so I replaced
that with soft 0.5mm braid.
This left almost a mm of naked guide out of the slot with the car viewed side on,
so I was able to raise the axle and drop the nose
by adjusting the grub screws so the guide sits full depth
in the slot.

Getting your guide as deep in the slot as possible helps both with cornering stability, and to counter the
"nose lift" which occurs when these more powerful
motors accelerate out of corners.
I have replaced the rear tyres with ScaleAuto SC-4728 "20 x 10" soft; which measure 20.2mm O.D.
when fitted, but after truing this dropped back to
about 20.0mm even. I need to knock this diameter back,
as I want to retain as much gap as possible between the tyres and inside of the wheel arch.

They are not edge-profiled on the outside edge. I will also do this while on the tyre lathe, to enable
more body float.

I will probably need 8 or more grams of weight near the guide to counter "lift" and to adjust the front
to rear balance closer to that magic 40:60 front/rear
balance that is always a good start point when tuning
a car for your track.   That weight can be added during track testing.

Note that these tyres are very low shore - less than A-shore 20 according to ScaleAuto, and the compound is
similar to F15 or NSR "Extreme".

That means if you overheat them by applying too much force resistance doing truing, they WILL ball up,
and WILL
turn to a sticky mess, proceed carefully.
The fronts themselves are reduced to about 19.4mm diameter after the glue and true process.
The splitter has only 0.5mm clearance.

[Image: porsche22.jpg]

Setting up one of these podded cars to go well without magnets is initially less work than a Home
Series car, but with the much higher powered motor,
they need to be done well, as higher motor power
exposes tuning faults very quickly.

Below is Circuito Bahia Vista; the same technical 20 metre layout as used in the article for testing the
ScaleAuto  Home Series Porsche
which achieved a respectable 6.8 lap.
This track is not as easy as it might look, a few home builder "tolerances" and some awkward reversals
of angle, mean the balance corner to corner is quite challenging.

[Image: bahiavista.jpg]

The all-comers lap record on this track is a 6.1, so keep that in mind as you read on.
I was keen to see how this "R" series car performed. But first I ran some fully tuned  Group 5 cars
from my own racing stable, which I know to be well set up and fast
on all tracks to warm myself up.

[Image: porsche26.jpg]

With the lower powered Group 5 ( orange bell), I eventually knocked over a high 6.5,
and for the other two, which both have easy handling
sidewinder setups with "red-Bell" 29k motors,
I managed 6.4s and 6.3s One of these cars placed 2nd overall in the New Zealand Group 5 proxy
four or five years back.

That BMW has since been further "improved" and was dominant in club racing just three weeks ago,
so how does our little Porsche fare first up?

[Image: porsche27.jpg]

I came away from home without any lead for weight tuning, so I had to improvise with just
2 grams of blu-tak I found in my mobile "kit".  Well it was pretty quiet, and seemed stable,
so I gave it some curry. Within five laps I laid down a low 6.3 WOW ! I didn't expect that.

In the end, despite my belief it had a 6.2 in it, I never went below this 6.32 time, but I managed
quite a lot of 6.3s and 6.4s That is better than 3 metres per
second average lap speed, for a very
technical circuit; and surprised me; having done no live tuning. I could easily run this in our GT3
class at club without
any further development. With that bit more weight in the nose, I think a 6.2
would have been easily achieved.

So my verdict is: These ScaleAuto "R" series cars can foot it against any of the other top makers
with just the usual tuning. Most pleasing was that it
showed no signs at all of shudder under heavy
load coming out of all the tight turns with a torquey FK-180 boxer type motor in angle-winder setup.

The pod stiffness with the motor screwed in to make a bracing element seems fine for high grip situations

I think ScaleAuto have done a very good job developing their new chassis and pods. Thank you Ivan.

As one customer put it after tuning his first ScaleAuto GT, which has the same pod and
running gear as this Porsche 911
“ Very pleased with Viper. Performance on par with NSR C6 Corvette.”
[+] 4 members Like slotloco's post

Thanks for the report 'loco. I have one of this range and am looking forward to teaching myself the finer points of tuning with it! 

In that regard, I don't often read tuning reviews where exact ballast weightings are quotes, so I was interested in your reference to it possibly needing  8g of front end lead. Also your reference to the 40/60 balance. it the case that I add the 8g weight at the front, get the scales out to check the front/rear balance, and then add some weight at the back to get 40/60? With that being my baseline for starting on-track testing. Or should I be on-track (scalextric sport) testing right from the start before adding lead? 

Apologies for all the questions, but I am using your two 991 reviews as reference points, along with other thread based tuning tips, as they are the model I have so feel more relevant.

Many thanks.

Hi Jeremy

the 40/60 weight balance thing has been around for probably decades. I don't follow it closely, but it isn't a bad place to start with weight tuning.
I am fortunate in having my own 65 foot track for depth testing, and race weekly around a group of 6 or so wood tracks in all, so I get plenty of opportunities to experiment.
As the guys in the basic tuning thread mentioned - it is more like a multi-way split of different things to experiment with, rather than a linear process.
But if the car is sidewinder OR angle-winder, I always begin my weighting process with a few grams to hold down the nose, as the car is probably 30/70 or thereabouts.

I guess I first make sure it is flat/square, 4 wheels on track, guide full depth, all wheels glued and trued.
As I begin to drive I am looking for undesirable behaviour - eg a saloon, or even sport GT like this which rolls over, it needs low weight.
If it deslots without rolling over, I am asking myself, which end, and how?
If it lifts the nose out of the slot when starting, or coming out of tight turns, I am checking the braid is set as low and flat as possible, then weighting the nose or tail as required
For podded cars, I am checking the amount of pod float is even all around, and that nothing is catching, and asking myself if the pod might be flexing, - motor screws help with that, as they turn the motor into a stiffening element.

If the body is heavy, I am asking whether I want weight in the pod itself, or on the main chassis plate, to make the whole thing more stable under cornering load (and sometimes I end up with more pod weight, other times sod's law comes into play and I add more to the chassis and have quite a light pod and drive-train.

If it sounds or feels tight, or seems a little unpredictable - I am really looking at possible chassis/body interferences, chassis/pod interferences; or of wheels inside the arch touching the body during corners.......

Sometimes think I am a top 1% tuner, and other days I think I am an utterly useless plonker when I cannot sort a behaviour issue on a car.
[+] 3 members Like slotloco's post

Absolutely what I was after. 

Thanks for sharing.

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