Miatapower List Archive

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Mail From: "Shiv S. Pathak" <(email redacted)>

Espen Tandberg wrote:
>
> > Can the 500 rpm steps of the Link be felt in daily driving? I am most
> > concerned with daily driving and of course driveability is much more
> > elusive than power. I should add that I have no experience with
> > aftermarket ecus, only what I've read.
> > Can the 500 rpm steps of the Link be felt in daily driving? I am most
> > concerned with daily driving and of course driveability is much more
> > elusive than power. I should add that I have no experience with
> > aftermarket ecus, only what I've read.
>
> FWIW, I think the Link is just as smooth, or smoother then the stock ECU in
> terms of drivability. Remember that even though the Link is only user
> adjustable in steps of 500rpm, the ECU interpolates between these steps...
> The TEC II is surly the better ECU, but it's hardly a plug & play unit and I
> don't think the "daily driving kind of guy" would draw too much benefit from
> it. But then again I really don't know anything but the fact that I'm very
> happy with my FM ECU... and now that it comes with boost controll I like it
> even more...
>
> Espen

This is a good thread.

Unlike Barry, I really never thought about the user definable zone as being an advantage
until now. 500rpm is a wide band to cover. As a few have discovered, some engines have
v.e.s/fuel requirments/etc,. than can change suddenly. Fixed xones make it dificult to
tune for this situation unless the situation occurs *right* on that breakpoint.
Extrapolation is there, but it only draws a straight line between the two breakpoints.
This only works if the fuel requirements ar linear between the two zones. But again, as
some have seen, optimal fuel demand is not perfectly linear with respect to rpm. Now
throw in fluctuations of manifold pressure and things start to get more hairy. The
explanation is pretty oversimplified, but an explanation, nonetheless...

Smoothness is a often misunderstood quality too. A car which runs overly rich or blurs
transients by running to rich (I'm NOT directing that at FM cars) will be smooooth-- in
fact, it will be smoother than stock. I spent a lot of time driving stock Miatas when I
was tuning my car. The throttle response on a stock Miata is laggy, no doubt due to all
that intake mess (can be fixed with a JRCAI or, better yet, FM sidedrafts). However, the
power response (whatever little it has) is *immediate*-- almost jumpy. There is a sense
of immediacy that a NA car exhibites which takes a while to get used to. Once you get
used to it, it provides very tactile feedback to the driver. I believe this is partly
what makes a Miata so enjoyable. Sure, it's short on power, but it does provide a very
real link between the driver foot and the rear wheels. Some stock cars don't have that
quality, but the Miata does. It's a very hard thing to describe, but that's my best
effort. And that's just ONE aspect of what makes a car feel right.

Tuning for this is pointless unless you have a ECU that responds smartly and quickly
(again, I'm not pointing fingers). Mazda spent millions of dollars in tuning to get it
right. I'm led to believe it involves a carefully tuned relationship between
enrichments, enleanments (both TPS and manifold pressure triggered) and a firm grip on
min. injector pulse widths (somewhere around 1.07ms in my particular car)-- long enough
so the engine doesn't stall on coast down and short enough that it doesn't run rich and
fat during on and off load transitions.). There problably more areas of importance, but
that's another story which requires me to hit the books so I don't say something stupid.

Smoothness, however, is a good thing when you are talking about engine performance under
steady state conditions (idle or load). Engines which feel "less smooth" often exhibit
slight (to slight to be obvious) misfire. How many of you guys thought your car was
running just fine-- then in scheduled maintenence, you changed your plugs and plug wires,
and said "damn, this runs a lot smoother now." Purely an ingition related condition that
wasn't appearant until you made a change. Now imagine the ingition requirments when the
cylinder is jamed with fuel from a wide-open 500cc injector and pressurized to 15lbs of
boost. For example, the RX-7 tt's stock ignition system won't permit more than
310-320rwhp, while the turbos and fuel are good (although fuel supply is at its ragged
edge) for somewhere around 360rwhp. Not only does a crane ignition upgrade increase hp
in this situation, it also smoothens the engine at idle and cruise. Why don't I have
one? Because I don't want to chance running lean on 92 CA octane gas. Misfire is better
than knock.

Turbo matching, of course, is another important consideration. I drove my brothers Miata
(as well as Jimmy C's car), both equipped with TECs and Garret turbo #3. Both cars are
in their infancy stage right now, so nothing is certain. At this point, power is good,
however things take a bit too long to get up to boil. Lost is a good deal of immediacy
in power delivery that many (including myself) prefer. Neither have had their boost
controllers optimized (or even functional), so that judgement is very premature. If this
turns out to be the case, I would opt for a turbo with a smaller exhaust side. Sure,
theoretical peak power wont be as high, but it'll give me what I want (all the time) and
take away something I *won't* notice 80% of the time. Since tuning a car involves
juggling a few performance compromises, there is some merit to the idea of be
uncompromised in places where you can be uncompromised.

The only compromise then, is how much time you can invest learning/playing during the
initial tuning process (very important-- if you don't want to invest time and effort to
learn what a certain ECU can do, don't get it and don't expect too much on-line help
either-- it just takes experience). The beauty of the Link is that Bill supports it far
better than anyone supports the Haltec or TEC-II. One tuned, the TEC is never touched
again. But getting to that state of tune requires a lot more than dyno testing. In
fact, unless you have experience in tuning them, I would suggest spending a few months
getting it working close to optimally. The TEC work at 85% just minutes after firing it
up for the first time. The last 15% (the fun part, in my opinion) takes a lot longer. I
don't like reading the manual so it took me nearly 6 months before I felt I could tune it
close to optimally.

In my situation, a good interface and a powerful, adaptable ecu (temps and altitudes
won't phase it) can be very welcome. To others, ease of installation, dealer support,
and ease of removal are understandably more important.

To remove a TEC you would have to swap in original injectors, plug in the stock
ecu/wiring harnesses (assuming I didn't throw them away), unbolt the TEC from the
firewall, install the MAF sensor, hide TEC wiring harness, and remove visiable sensors
(temp, MAP, clt, TPS). Not fun. However, if I was ever faced with a reason to remove
the TEC (visual emmissions inspection, for example), chances are, I would have to remove
the turbo as well (which takes far longer).

Frank Mowry writes:

> I think given a properly tuned Link and a properly tuned TEC on the same
> car, you wouldn't be able to tell the difference.

I've driven many examples of both and I not sure I agree. We'll get some more opinions
at the Dyno day. But yes, properly tuned is a key. Now, drive both cars to 3000ft
altitude or wait till nightfall when the temp drops 30 degrees. Now compare. A very
real situation if you live in CA and are lucky enought drive up and down mountains and
put up with a weather system that changes by 30 degrees during 20 mile drive. This is
what is meant by an adaptable ecu.

> Granted the keypad leaves
> a little to be desired, but once it's tuned, unless I'm spending every
> weekend on a dyno, I don't really need to touch it after that. The biggest
> shortcoming is the software. I think a proffessionally done Windows program
> that shows the timing, tach, fuel injector cylce, O2 reading etc. all on one
> easy to read screen is a must.

More important than an interface is an ecu that offers good "resolution." Of course,
resolution is relative so let's leave it at that. Resolution is also an abstract,
hard-to-define term, esp. coming from a technically impaired tweaker like me. In this
respect, I feel the TEC offers more than the FM. Much like the way a MOTEC should offer
more than a TEC. The chain is endless. Pick where you want to get off and be happy that
you made a careful and educated decision.

Shiv
Project RX-7
w/remapped stock ecu
12psi

This read-only message was archived from a public mail list.
Mail From: Douglas Hagerman <(email redacted)>

Can you expand on these two things a bit? ("throttle response" versus
"power response", and the value of improving the RX-7 (3) ignition)

Thanks.

Doug.


> The throttle response on a stock Miata
> is laggy, no doubt due to all
> that intake mess (can be fixed with a JRCAI or, better yet,
> FM sidedrafts). However, the
> power response (whatever little it has) is *immediate*--
> almost jumpy. There is a sense
> of immediacy that a NA car exhibites which takes a while to
> get used to.


> For example, the RX-7 tt's stock ignition system
> won't permit more than
> 310-320rwhp, while the turbos and fuel are good (although
> fuel supply is at its ragged
> edge) for somewhere around 360rwhp. Not only does a crane
> ignition upgrade increase hp
> in this situation, it also smoothens the engine at idle and
> cruise. Why don't I have
> one? Because I don't want to chance running lean on 92 CA
> octane gas. Misfire is better
> than knock.