[Diy_efi] RE: Diy_efi digest, Vol 1 #413 - 12 msgs

[Ioannis Andrianakis]

Concerning the point of tuning on the road being better than tuning with a
steady state dyno I would like to ask some questions based on my
observations.
When trying to get the best performance by road tuning, which gear ratio do
you optimise for? I know that if I optimise fuel and ignition for 2nd gear,
the performance of 4th gear will be far from optimum. Do you let the car
cool down between runs? Stationary or by low load cruising?So you come to
the same point as using a dyno that you have to compromise between the
different needs of the engine at same rpm and throttle oppenings but
different acceleration ratios and history. Unless your car is a racecar and
you have an ecu that can be mapped for every gear and a dyno to simulate the
whole race and datalogging to check you performance then your tune is not
ideal, its close but not ideal. The more experience and data you have the
closer you can get. I have found that using a brake dyno(dynapack) and
steady state tuning to get the map close and fixed acceleration ratio ramp
tests(approximating road acceleration ratios) to optimise, I can get close.
That is championship winning close. But still I dont know how far from ideal
I am. Wish I had more time,money and tools to achive a better tune.
Regards,
Ioannis Andrianakis
----- Original Message -----
From: "Shannen Durphey" <shannen at grolen.com>
To: <diy_efi at diy-efi.org>
Sent: Wednesday, December 18, 2002 7:34 AM
Subject: Re: [Diy_efi] RE: Diy_efi digest, Vol 1 #413 - 12 msgs


>
>
> Adam Wade wrote:
> >
> > --- Shannen Durphey <shannen at grolen.com> wrote:
>
> > > A lightweight car with a high power to weight ratio
> > > would typically never see the same load and duration
> > > that can be applied with a brake type dyno.
> >
> > How do you figure?
> Easy.  Using the dyno, I can apply enough load to keep a 200hp Honda at
> 1500 rpm indefinitely.  Unless it's hooked to a trailer full of horses,
> there's no way that Honda will see the same load for the same amount of
> time on the street.  It only passes through that point in a fraction of a
> second on its way to "somehwere else."
>
> > All that power goes into
> > overcoming aerodynamic drag, and either you accelerate
> > with it, or you reach a steady state where the power
> > produced is equal to the load from drag.  If you can
> > add more braking with a brake, the rpms drop.  With an
> > eddy current brake, anyway, you hold a certain rpm
> > with a certain throttle position, and map for that
> > load.  Max load given by the brake should be WOT at
> > best horsepower; no more.  One can certainly expect
> > the vehicle to obtain that loading condition at some
> > point in its life.
>
> Are you considering time?  It's the "at some point" that makes the
> difference.  As a wild example, consider the dyno load causing the engine
> to take 5 minutes to reach 1500 rpm vs the same engine getting to 1500 rpm
> in a second on the street.  There's going to be a lot more heat produced
> during the 5 minute pull than the one  second run.  The longer the
engine's
> exposed to heat, the more the heads will heat up, the cooling system will
> heat up, radiator, engine comp't...  After 5 minutes of dyno run time you
> can bet engine conditions aren't the same as the "real world."
>
> A different example:  Set the brake to maintain a specific rpm.  We can
> accelerate to close to that rpm with minimal effort, and we can stab the
> throttle right as we get to that rpm.  The perfect dyno will hold exactly
> enough brake to maintain that rpm.  So now you're running at the desired
> rpm.  You have to take readings, maybe change settings.  How long does
this
> take?  10 seconds?  5? 2?  How does this time compare to the time the enge
> spends at that rpm and load when it's not tied down?  How much more do you
> heat the engine?
>
> >
> > > Running up to a specific rpm and holding that rpm
> > > while fuel and spark are tuned in will tend to heat
> > > parts more than they would be heated in "normal"
> > > operation.
> >
> > I disagree.  Unless you're talking about a
> > grocery-getter.  And in any case, you will get the
> > conditions in component heating in the real world that
> > you would on the dyno (give or take a small margin),
> No, give or take a large margin.
>
> How about a different example. If we can think of a vehicle as a dyno,
then
> we can consider the difference between a heavy, loaded truck and a
> lightweight car with the same engine.  The truck spends more time at WOT
> with rpm changing less.  It builds more heat in the chambers, at  the
> plugs, in the cooling system.  If we are tuning this truck, then we see
> that as heat increases the tendency for detonation increases.  We both
know
> there are ways to fix this.  We can adjust spark and fuel to prevent the
> heating/detonation from occurring.  And when we're done, the calibration
we
> end up with is safe for the vehicle.
>
> The problem occurs if the engine is taken from the heavily loaded truck
and
> placed into the lighter car.  There are few clues to tell you the
> calibration could be better.  There's certainly little sign that fueling
or
> spark is wrong.  Depending on when you look, you might catch clues from
the
> plugs. But fuel and spark are not really "wrong."  It's just that they
> could be better.
>
> > assuming you have adequate cooling in the dyno room;
>
> Cooling is a big part of the issue.  Maybe this will help.  Compared to a
> bike, you could think of a car as having inadequate cooling on the street,
> and usually less in the dyno room.
>
> > > The consequences can be more fuel/ less spark than
> > > optimal get dialed into the final tune.
> >
> > Again, a number of years of fairly constant
> > dyno-tuning experience with motorcycles disagrees with
> > that assessment.   Again, though, the dyno rooms I was
> > using were either outdoors with very hugh-flow fans
> > and ducting, or with exceptional exhaust fans indoors.
> Consider the mass of the engines you're tuning.  Think of the airflow
> around the engine, the size of the cooling system versus the size of the
> engine, the materials the engine is made from.  I'm not going to say this
> is fact, but I'd bet it's a far cry easier to remove heat from a finned
> head, relatively open chassis bike engine than from a car's or truck's
> engine.
>
>
> >  Temperatures are constantly checked while tuning, and
> > are almost exclusively found to be normal operating
> > temperatures.  Very few real-world tuning changes need
> > to be made after leaving the dyno
>
> Not trying to be a prick, but how do you know?  What I mean is, are you
> looking for signs that something is wrong, or signs that something is
> right?  It's awful hard to find a clue that things are performing at their
> best.  Even the top dawgs know their stuff is only working better than the
> guy at #2.
>
> >
> > > The inertial loads alone provide more than enough
> > > resistance to provide an acceptable street and
> > > competition tune for these vehicles.
> >
> > I suppose it depends on what you consider
> > "acceptable".
> Point taken.
>
> > At the AMA Superbike races, losing
> > isn't considered acceptable, which is why even teams
> > sponsored by Dynojet often get their bikes tuned on
> > eddy-curent dynos trackside.
>
> Ok, but racers are paranoid.  Smokey Yunick once said something like "If I
> showed up at the track one week with dog turd on my hood, next week
> everyone would have dog turd on their hoods."  To be fair, if I wanted to
> make changes to my car on Race Day, and I'd found that an eddy current
> dyno, or an inertial dyno, or a bag of angry cats tied to the fuel cell
> gave me results that I trusted, then that's what I'd use at the track.
The
> game is different on race day.
>
>
>
> > My experience has been
> > that any motorcycle tuned by anyone on a Dynojet dyno
> > can be tuned better on an eddy-current dyno, and I've
> > yet to see that belief disproven.
> Are you saying that you've back to back tuned between different types of
> dynos, or are you comparing stories with other people, or are you judging
> by bikes that others have tuned which you're retuning?
>
> I plead no contest to this example.  I can't prove true or not true.  But
> for the general implication that a tune will be better on a specific type
> of braking dyno because of the type of dyno, I say there are  exceptions.
>
> >
> > ...time, energy and money wasted, IMHO.
> Agreed, 100%
>
>
> > Well, so far in this thread we've had one person with
> > experience explain that changing the ignition timing
> > can change the reading on a WBO2 sensor, without
> > changing the fueling.
>
> Now you have two people with experience saying it's true.  But it's
> important to understand why and when this will happen.  Changing timing
> changes the start of the burn and affects the end of the burn.  You can
> easily push some of the reaction into the exhaust pipes by playing with
> timing.  Since the O2 sensor measures oxygen between the exhaust and the
> fresh air, it will "see" an increase in the amount of oxygen in the
exhaust
> as a change in AFR.  The closer the sensor is to the exhaust ports, the
> more oxygen it will see, and the more it will be affected by timing
> changes.  At the end of a street car exhaust, all this "outside"
combustion
> is done.  I've actually heard one guy claim that changing from 100 octane
> race fuel to street fuel richened his mixture.  It seemed less of a
miracle
> after I checked O2 sensor location.
>
>
> > And it's pretty well-known that
> > plug chops tell you if you have the right heat range
> > plug for the engine and fueling, and nothing more.
> > You CANNOT use plug chops for effective tuning unless
> > you ALREADY KNOW that you have the optimal heat range
> > for your engine.  THEN they can tell you something.
>
> I don't agree with that.  If you pick a plug, and run it, and it shows
> lean, you can add fuel.  If the car's speed/response/power falls, you can
> add timing.  By doing this you will find the optimum fuel and spark for
> that plug.  Switch to a colder or hotter plug and try again.  When you're
> done, you will have found the optimum fuel/spark for each plug, and the
> trend of times/ speeds will point to one or two plugs as optimum.  It does
> work, but it's slow.  My point was that it's a tool just like the WB.
>
> > Er, who said anything to that effect?  IF you're
> > assigning those ideas to me, you've significantly
> > misread what I was saying.
>
> My apologies.  You were advocating moving the wideband closer to the ports
> to reduce delays in sensor readings.  I thought you were saying that the
> delay was a "bad thing."
>
> >
> > > For many, many street cars, WB + inertial dyno +
> > > competent tuner is very satisfactory.
> >
>
> > Would I rather spend my money on an eddy current dyno
> > with a four-gas?  Absolutely.
> There ya go.
>
> I did my own comparison years ago between inertial dynos and braking
dynos,
> and braking won.  I also have issues with the Dynojet user interface, but
> that's a different story.  But I think it's important to make the
> distinction (and you have) between bench racing dynos and the general
> usefuleness of any type of dyno.  Every step forward is a good one, and
the
> more "the consumer" becomes aware of what it takes to make a good
> calibration, the less likely he will be to support vendors that sell junk.
> Getting guys onto a dyno is a big step toward furthering that
> understanding.
>
> Shannen
>
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