0-100

Jon Addison · Post by **Jon Addison** » Sun Jul 17, 2005 4:05 pm

Food for thought: It's been interesting tracking the comments about
mods that cut 0.5s off the MX-5's 0-100km/h or quarter mile times.
As far as the 0-100km/h time goes, 0.5s is well within the range of
variation one driver will achieve over three or four attempts. I've
seen "professional" times ranging from 8.8s to 9.9s for 1989 1.6
manuals with similar spec.
From the same era, a VN Commodore 3.8V6 (1334kg) with 125kW was timed
at 7.7s, while a 5.0V8 (1377kg) with 165kW managed just 0.4s quicker at 7.3s.
It seems unlikely that shaving a flywheel or changing an air intake
would have a measurable effect on 0-100 times. Cutting 0.5s would
probably need +10kW or a 100kg weight reduction. Or new red paint.
In the opposite direction, modern wider "sticky" tyres with a higher
rolling resistance will probably increase 0-100 more than shaving a
flywheel will reduce it. With more rubber the car will corner faster
without sliding - bugger!
Jon Addison

Mike Jolley · Post by **Mike Jolley** » Sun Jul 17, 2005 7:47 pm

At meremere in my 1600cc mx5 and over 12 runs on one day(basically same
track conditions)i was less than 0.5 sec
different over allruns. Mike

Mikkels · Post by **Mikkels** » Mon Jul 18, 2005 11:58 am

What were your times Mike?

I'm interested to know because I have put a 1.8 in my 1.6
and would like to know how much (if any) it has improved the
performance. It certainly feels quicker but you are
fighting the placebo effect.

Also one must apply statristics to the question. Do at
least five, but the more the merrier, runs and take the
mean. This will increase the statistical power of any
observed differnces once changes are made. If the change is
likely to only make a very small difference (14 degree
timeing for instance) then you need more runs before and
after to pick a difference. Also quarter mile times will be
more reliable than 0 - 100 as the percentage difference the
launch makes decreases as a fraction of the total time.

I'm going to Meremere before I install the flywheel and
after and I plan to do 10 runs each time if I can fit that
many in. Also want to match the other factors like track
conditions and tyres etc to get as good a match as I can.

Cheers

Don

Don

[...]

Ian · Post by **Ian** » Mon Jul 18, 2005 1:36 pm

Another method, and way less susseptable to the variables you speak of, is
to find a deserted stretch of straight, flat road on a windless day (I know,
near Wellington this may ot work!)...bring the car up to 80kph in say 4th
gear, and stop watch in hand, floor the accelerator! Stop the watch when you
hit 130kpk . Record your time...do several runs if possible to get an
average. Use this time as a baseline to measure the effectiveness of all
modifications. Try to have the car carrying the same weight on future runs,
eg a markedly different fuel load and/or passenger will introduce unwanted
variables, as will travelling in the opposite direction, if the road is not
perfectly flat...

This is a far easier/more accurate way (not to mention cheaper and kinder on
the car) of measuring the effects of many performance modifications...
Granted, going to the drags is a heap more fun!!

Ian

Mikkels · Post by **Mikkels** » Mon Jul 18, 2005 3:44 pm

Good idea but no good for the lightened flywheel as the most
impact is in 1st gear and deminishing as the gearing
changes.

the drags it is.

Don

[...]

Mike Jolley · Post by **Mike Jolley** » Mon Jul 18, 2005 4:52 pm

Yes warm vs cold track at Meremere makes difference in traction.On my Modern
and Vintage Motorbikes i lighten fly wheels from Radiacal to mild=better
pick up and a little less engine braking.On some bikes you add flywheel
weight for down low bite to help smooth out the power band.. I see some
alloy flywheels for mx are only 8 LB,damn there must be away to go lighter
says the engine builder with in me(while that damn common sence side nags
this is probably tried and true.)

mike

From: <mikkels@ihug.co.nz>
To: "MX5List" <mx5list@mx5club.org.nz>
Sent: Monday, July 18, 2005 11:58 AM
Subject: Re: 0-100

[...]

Ian · Post by **Ian** » Mon Jul 18, 2005 5:34 pm

Well, without wanting to start an argument, my suggestion could be adapted
to utilize say 1st and 2nd gears, using a rolling start and coming up with
some predetermined starting and terminal speeds. What I am suggesting
overcomes a critical variable - the amount of wheelspin (or lack of it), not
to mention several gear changes...

But what would I know?

Rex Johnston · Post by **Rex Johnston** » Mon Jul 18, 2005 6:21 pm

Karl Mowatt-Wilson wrote:

I can lend you
one if required (but it will entail me writing some new software to
make it work - old software runs under DOS/Windows, but now the
laptop runs Linux).

Dosemu. Failing that Bochs.

Cheers, Rex

Post by **simple** » Mon Jul 18, 2005 6:24 pm

Bearing in mind that I know diddly-squat about engines...

Well, without wanting to start an argument, my suggestion could be
adapted to utilize say 1st and 2nd gears, using a rolling start and
coming up with some predetermined starting and terminal speeds. What I
am suggesting overcomes a critical variable - the amount of wheelspin
(or lack of it), not to mention several gear changes...

I suspect that this technique, whilst a fine way of measuring various
aspects of engine performance, is not relevant to measuring the
effect of flywheel changes.

As I understand it, the main benefit sought in lightening a flywheel
is the quicker spin-up (and down) of the *unloaded* engine when
performing *gear-changes*. So, if your test technique does not
involve changing gear, then you might have a hard time observing the
benefit.

Don: if it is of interest for you to borrow, I have an interface for
the IG signal from the engine-bay diagnostic connector. It needs to
be connected to a laptop to do the actual logging - I can lend you
one if required (but it will entail me writing some new software to
make it work - old software runs under DOS/Windows, but now the
laptop runs Linux). From this, one can easily plot exact engine rpm
vs time. I built the interface before Fletcher got his Link, and we
wanted a way to try to measure his engine performance (with the
rolling start, 2nd gear method).

If it were me, I'd be inclined to do a bunch of logging of gear
changes before and after the flywheel mods, to see what difference it
made to things. Ideally, one would have an accelerometer tied in as
well, but those sensors are still in the box they came in (been
waiting a number of years, so far).

Karl.

Ian · Post by **Ian** » Mon Jul 18, 2005 7:33 pm

Hi Karl...

No, in my view, the principal reason to lighten the flywhel is to allow the
'car to accelerate quicker', and it does this for reasons more eloquently
explained by others...(less rotating mass etc etc)

Cheers, Ian

Mikkels · Post by **Mikkels** » Mon Jul 18, 2005 8:07 pm

Karl

Thanks very much for the offer. I'm hoping that the
difference will be able to be felt by the bum-ometer and
verified by quarter mile times.

Otherwise benefits able to be seen on paper but not felt in
the pants are just not worth it.

Interesting bit of software though and one could think of
other uses for sure.

Cheers

Don

[...]

Mike Jolley · Post by **Mike Jolley** » Tue Jul 19, 2005 5:16 pm

17.3 to 17.5 consistantly
bog std, 14 degree timing and pod filter
my start reaction time quicker than most pro's ( upset my son in turbo
skyline)
beat a lot of cars to half way(power to lite weight) then they would go past
like you were standing still at top end.
Adjust my suspension ,different rear wheel/tyre height,and exhaust could go
lower 16s.
still a lot of fun in dial your own knock out runs,
Mike

Mikkels · Post by **Mikkels** » Tue Jul 19, 2005 7:48 pm

Anybody done this in a standard 1.8? It would be good to hear what is
achievable. My son ran his stock 1990 VTEC Integra to 16.0. Damn good
those Honda VTECs

Don

Jon Addison · Post by **Jon Addison** » Tue Jul 19, 2005 8:15 pm

Australian Motor magazine Nov 1989 averaged 16.73s in both directions
with a best of 16.35. Figures on Correvit equipment, presumably
eliminating driver's reaction time by starting from actual initial
movement of the car. Tyre pressures may have been "track" and the car
would have been very fresh.
Jon

On 19/07/2005, at 5:16 PM, Mike Jolley wrote:

[...]

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