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#Post#: 6525--------------------------------------------------
Tuning the GX200
DIR By: Adrian
Date: April 25, 2022, 12:13 pm
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First post coming soon, (page just crashed).
#Post#: 6597--------------------------------------------------
Re: Tuning the GX200
DIR By: Adrian
Date: May 2, 2022, 12:48 pm
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Setting a Standard?
In France, all Cyclekarts must use standard, out of the box
engines.
Nice and simple, every car the same.
In the USA, it’s clearly different since they seem to be more
focused on speed.
In the UK most people have already tweaked their engine to some
degree or other but nobody really knows how powerful they are
but remember that there is only one reason for tuning an engine
and that is to make your CycleKart go faster.
In the UK we have a generally accepted limit of 10h.p., but we
cannot know what has been done to an engine and so we rely on
the integrity of the owner.
That’s a pretty loose ‘standard’ and as such is almost useless.
What does it tell you?
Looking on the GX Tuning Store’s website it’s clear that a lot
can be done to these engines to quite dramatically improve their
performance.
I, no doubt like you, want to be competitive and not get left
behind in the dust when we do speed events on go-kart tracks or
demonstration runs.
In the UK, we do not run organised races with multiple cars on
the track at the same time but we have fun on the track when two
or three drivers might find they are having a bit of fun with
each other. We often have little tussles on the track but just
fun/practice stuff.
My cyclekart (the 1906 Renault) is heavy and using a stock
engine is outpaced all the time.
What can I do to help it along a bit, so that it can keep up
with the faster Cyclekarts?
Remember, these faster CycleKarts will have been tuned to some
degree or other as well. So, I have to tweak my engine in an
effort to make up for it’s 100 kilo weight handicap.
I imagine this means more h.p. is required.
Well, if I am going to work on the engine, I need to investigate
how the engine can be modified and what modifications give what
increase in h.p.
Imagine there was such a list.
You could look down it and decide which items to pick in order
to achieve your goal of 10h.p., delivered as you think best.
You could decide that quicker acceleration or high top speed was
your goal.
Picking items off the list would enable you to tune your engine
for the sort of performance you want but, just to complicate
things a little, you will need to decide on the transmission you
are going to use (clutch or CVT for example) and what if
anything, can be done to it to improve its performance. Remember
that there are no tweaking restrictions at all on the
transmission. :>)
This suggest picking some items off list in order to get the
full 10 h.p.
The question is how do you know your engine is not producing
more than 10 h.p. and how would a scrutineer (which we don’t
have) ever know you were playing fair? We don’t have a portable
Dyno!
In my humble view, the only answer is to limit the performance
parts you can use to those on a published list. Using some would
give as much as 15 h.p. but that would be against the rules.
When you have done, you must sign a document which (in good
Faith) lists the choices you have made.
Of course, if everyone was using all the same parts it would
have the same effect on the pastime as the French rules have on
theirs. We would all be equal albeit that bit quicker.
Honda produce this so that it delivers 6.5 h.p. no more, no
less. It has the perfect crankshaft, piston, con-rod, cam-shaft,
flywheel etc. etc. for its need with every bit of the engine
fully satisfying the demands placed on it at the lowest cost
possible.
Just keep that last bit in mind.
If we want to take the 6.5 h.p. up to 10 h.p. we need to do it
as cheaply as possible.
Let’s look at what is needed to produce this increase of 3.5
h.p.
This example will result in an engine very close to the maximum
power allowed, 10h.p. and at the lowest cost to you.
1.
2.
the emulsion tube to a size 140.
3.
4.
5.
You’re up to 9 h.p. now so what about the tenth?
We go back to our list and pick another item that gives just a 1
h.p. benefit and then do that.
For example you could open out the inlet and exhaust ports in
the cylinder head to match their manifolds and polish them.
Now your up to 10h.p. so you have to stop there.
An alternative 1 h.p. gain could be to radius the back of the
inlet valve, narrowing the valve/seat contact area.
Doing this effectively increases the valves diameter and lessens
resistance to the incoming fuel/air mixture.
A new stage 1 cylinder head from GX Tuning cost about £250.
They do the following to it:
1.
ratio and match and polished ports.
2.
just the one at 45°
3.
their lower mass reduces valve bounce.
4.
5.
secure fixing at higher r.p.m.
All the above with the standard carb and exhaust being used.
There are other ways of tuning the engine of course.
In my opinion fitting a free-flow tuned exhaust is the first
thing you should do.
It gives an immediate benefit by itself.
With the tuned pipe in place, a bigger carb can be used
providing more power at a higher r.p.m.
A Billet flywheel and a billet con-rod are nice to look at but
for our needs are pointless. They are not tuning bits as such
but stronger components to cope with the stresses that further
tuning (and higher rpm) will bring.
The heart of these engines is in the cylinder head. Concentrate
your thoughts on the heart of the engine, the combustion bit,
carb, inlet and exhaust.
Why am I saying all this when we are limited to 10hp. Well, lets
take a look at what I am doing to the Renault (and for that
matter, the Wee Beastie too though that has a dry clutch
fitted).
With the Renault more power is need to keep up with everybody
else but I don’t need that additional power for top speed. What
I really need is not more ‘top end’ but more bottom end speed,
more Torque.
Speed out of the corners and off the line is what’s needed so
more h.p. is required to give me more useable engine rpm. With
that I can lower the final drive/engine ratio for the improved
acceleration I need but without a loss in top end speed.
So for me it’s a tuned exhaust, a Makuni 22mm card (re-jetted),
a 4° offset woodruff key to advancing the timing, higher lift
rocker arms (1.3:1) and 18lb valve springs.
That’s it as far as the engine is concerned. I think I will be
within limit.
The Renault has a torque converter fitted and to help me utilise
my new additional rpm I am modifying the clutch by cutting the
weights in half and increasing the keeper spring rate so that
the clutch engages at a much higher rpm which will help to
prevent the engine from being ‘pulled down’ when trying to
accelerate from slow corners or off the start line.
So, to achieve the 10hp from your standard engine, take your
pick.
Be careful, this is where tuning balance steps in. Start with
the easiest to do, the exhaust and see how you get on.
P.S.
Just for your information, the following might be of interest.
Petrol engines run on a mixture of petrol and air and the ideal
ratio of petrol to air is around 14.7:1.
Wiki says:
The stoichiometric mixture for a gasoline engine is the ideal
ratio of air to fuel that burns all the fuel with no excess air.
For gasoline fuel, the stoichiometric air–fuel mixture is about
14.7:1 i.e. for every gram of fuel burned, 14.7 grams of air are
required to burn it.
It's worth noting that our engines probably won’t start from
cold on such a thin mixture. Putting the choke on, reduces this
ratio a lot, maybe to 8:1 or less so that the charge in the
cylinder will fire. Once the charge has fired the fuel/air ratio
can be returned to 14.7:1. as the engine reaches it’s normal
operating temperature.
Hope I haven’t bored the pants off you.
:>)
#Post#: 6599--------------------------------------------------
Re: Tuning the GX200
DIR By: Mark Under
Date: May 2, 2022, 1:44 pm
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I have tried my kart in a very small car park with an untuned
Honda and it is in need of tuning so I will be going with carb,
exhaust, valve springs, etc etc until it reaches a more exciting
speed.
Please don’t restrict engines too much as I for one would like
to go as fast as possible, although my kart has a long way to go
before it could be considered fast!
#Post#: 6600--------------------------------------------------
Re: Tuning the GX200
DIR By: Ian F
Date: May 2, 2022, 2:57 pm
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Engine modifications are very difficult to control without
stripping them down and measuring parts. There are also many
ways of developing an engine and before you know it you end up
in an expensive arms race spending ever increasing amounts of
money for ever decreasing improvements. I thought the aim of
the Cyclekarts was to have some great fun at a reasonably low
cost. Probably one of the biggest performance limitations is
the varying degrees of weight regarding the driver,
consequently for differing combinations of driver and karts some
karts may require more power. I just hope this can remain a fun
pastime and not a wallet emptying exercise. Suffice to say in
just the few weeks I have been building the CK, I have been
offered a 12 BHP engine and a 15 BHP engine! However, my plan
was simply to use a Cadet kart engine that pushes out around 9
or 10 bhp which seem to be widely available. For those that
want to get into "competition" there is a vast array of
championships to get involved in. I would also suggest that
beyond a certain sensible performance, CKs can become hazardous.
#Post#: 6612--------------------------------------------------
Re: Tuning the GX200
DIR By: Graham Hill
Date: May 3, 2022, 5:52 am
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I am personally keen to restrict CycleKarts to 10hp maximum.
That's accepted as stage one tuning of the GX200. Anybody
considering tuning their CK further for speed has not understood
the ethos of CycleKarting. The weight of the CycleKart or
driver is irrelevant.
The tuning of the GX200 has been historically documented on many
platforms, achieving 24hp in some instances. For CycleKarting my
understanding and experience is ..... Stage One ... 10hp max.
I have arranged events at Stretton Circuit since 2018 and will
make it known early that all CycleKarts are welcome on 24th,
but any vehicle tuned over 10hp will be restricted to a static
display only. All new-builds and existing-modified will be
subject to peer-scrutiny before being allowed on track.
The guidelines have been available on the website for some time.
However as a committee member I can advise that we have given
much serious thought to this area of the build guidelines and
they are to be confirmed and published imminently.
#Post#: 6613--------------------------------------------------
Re: Tuning the GX200
DIR By: Mark Under
Date: May 3, 2022, 6:54 am
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I am only putting the stage 1 mods on my kart, hopefully taking
it nearer 10/than 6.5hp.
Hopefully the parts ordered, carb, exhaust, valve springs and
timing key will take it up a bit.
I agree that to take it beyond this limit would get expensive
and probably not add to the fun much.
It would be a shame to be restricted to a bog standard engine as
I think the French are, part of the fun is tuning the engine and
getting the kart to go as fast as possible.
#Post#: 6614--------------------------------------------------
Re: Tuning the GX200
DIR By: TheGiantTribble
Date: May 3, 2022, 8:04 am
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A couple of thoughts...
The fun isn't in the speed...I know counter intuitive but that's
typical of CK's!
Mark, feel free to have a go in mine, I'm sorry to say all it
has is a tuned exhaust (to up the torque slightly) and the oil
sensor disconnected, and despite that's all it's got is still
manages to be rather sprightly.
Ian...as soon as a CK is moving it indeed has become hazardous.
Graham, given how difficult some of these tuned engines are for
people to start, could we introduce Le Mans style starts? ;D
;D ;D Please ;D
#Post#: 6615--------------------------------------------------
Re: Tuning the GX200
DIR By: Graham Hill
Date: May 3, 2022, 8:13 am
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Are you suggesting any handicap for inside leg measurement?
#Post#: 6616--------------------------------------------------
Re: Tuning the GX200
DIR By: Ian F
Date: May 3, 2022, 8:50 am
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Also think 10BHP is a sensible maximum guideline. Thats enough
to pull at least three rice pudding skins off ;) and to stop
them bogging down too much in tight corners. Going as fast as
possible will probably introduce additional hazaeds due to the
limitations of the other aspects of Cyclekarts, surely the fun
is to have a sensible working overall package.
#Post#: 6617--------------------------------------------------
Re: Tuning the GX200
DIR By: TheGiantTribble
Date: May 3, 2022, 9:51 am
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--- Quote from: Graham Hill link ---
>
> Are you suggesting any handicap for inside leg measurement?
>
--- End Quote ---
I think we could easily even it out for those of us who don't
have the legs of a Gazelle...everyone just stand 12 paces away
from their CK...I recons that's anywhere from 3 foot for you, to
20 meters for the likes of Adrian and Stephan!!! (sorry Adrian
and Stephan)
Hay if you make rice pudding properly a Lambo shouldn't be able
to pull a skin off let alone three!!!
Although that's now got me wondering if we couldn't add our own
version of tractor pulling to our contest's???
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