[Diy_efi] inertial vs brake

[Adam Wade]

--- A6intruder <A6intruder at adelphia.net> wrote:

> I think it's great that you guys are comparing the
> merits of the two types of dynos but for most of us
> we have to do most of our tuning on the street
> and then use the dyno for verification and bragging
> rights.

One of the things about an eddy current or other
brake-type dyno is that, if you have real-time tuning
software, it doesn't take much longer to do a tune on
the dyno than it does to simply do a run to gather
data.  That's something that people might want to keep
in mind when choosing a dyno.

There's nothing wrong with ANY method used to tune. 
Some will give better data than others, some cost less
than others, some are quicker than others.  Everyone
has to find a combination that works best for them. 
For me, I have found that my time is valuable enough
that I am willing to spend a little money to save a
lot of it.  My experience has led me to my own
conclusions, and thus YMMV, as well as your choices.

> The "street" portion of the tune takes time because
> I have to let the EEC have miles to add it's own
> corrections, then I make more changes to close the
> gap.

Driving the car around, it takes a lot more time to
hit more of the load/speed sites, whereas on a brake
dyno, you can manually "put" the vehicle at any one of
those sites you choose.  If you have the tools to
gather data from load/speed sites from driving, and
are broke, or are using this to learn more about how
real vehicles in the real world use what's in the map,
then that's great, and I applaud you.  It's a useful
learning tool, for certain.  If you want to get the
car very close in a few hours, there's no substitute
for a good dyno.

I'd also note that some load/speed sites are not hit
very often in the real world, and thus getting a
complete map that's good under all conditions may be
more difficult using street tuning.

> On the street they frown on sustained
> high RPM cruise...too bad.

Hehe.  ;)  That's one reason I definitely recommend an
inertial dyno to someone that has no other tools.  For
WOT fueling, it beats going to jail.  :D

> I think my local guy is fairly reasonable at
> $60-80/hr but I am not going back until I have the
> MAF curve nailed.

Indeed.  And honestly, if you can find someone with a
good brake dyno, see if their rates are competitive. 
I believe you will get a lot more data that way, and
may even use it as a real-time tuning tool.

> Then I will show up with several files ready
> changing the WOT A/F on each file.  My use of the
> dyno would be to see the difference A/F makes at
> each part of the RPM curve, then another
> series of files to see the effect of timing changes.

That's a pretty good way of doing WOT on an inertial.

> I have considered mapping the A/F effects by just
> measuring the change of acceleration (from data log)
> on the same piece of road at the same weight
> within minutes of each run.  This could show
> relative change to help select the optimum A/F.

It's a great way to tune acceleration maps, for sure.

> But in the end I will want that nice dyno produced
HP
> curve printed out for bragging rights.

I hear you.  ;)  One thing to consider, too, is that
an inertial dyno (DynoJet in particular) will read
about 18% higher than a corresponding eddy current
dyno.  While the numbers from the eddy current are not
only more repeatable, but more accurate as well, you
get better bragging rights with a DynoJet,
particularly if you can find one that reads higher
than the oens all your buddies use.  ;)

=====
| Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
|   http://y42.photos.yahoo.com/bc/espresso_doppio/lst?.dir=/   |
| "It was like an emergency ward after a great catastrophe; it  |
|   didn't matter what race or class the victims belonged to.   |
|  They were all given the same miracle drug, which was coffee. |
|   The catastrophe in this case, of course, was that the sun   |
|     had come up again."                    -Kurt Vonnegut     |

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