Miatapower List Archive

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

Quotes from piggy-back manual:

ACCEL: (Z16-Z19) Simulates the accelerator pump on a carburetor by
increasing the amount of fuel upon sudden throttle opening. The zones
affect the following RPM ranges:
Z16: 0 to 2000 RPM
Z17: 2001 to 4000 RPM
Z18: 4001 to 6000 RPM
Z19: 6001 to 8000 RPM

ACCEL DECAY: (Z20) Controls the decay time of the accelerator pump fuel.
Lower numbers offer faster decay. These numbers are not seconds.

SETUP:
The ECU has an accelerator pump feature. When the throttle is moving
down the ECU adds fuel to the engine. If you see the air/fuel ratio go lean
as the throttle goes down then come back to normal, add more fuel to the
acceleration zone. If the air/fuel ratio stay rich, but dips lean before
stabilizing, then lengthen the acceleration decay time.

(end quotes)

Questions:
1. "Simulates the accelerator pump on a carburetor by
increasing the amount of fuel upon sudden throttle opening."
Does "sudden throttle opening" refer to going WOT?

2. "When the throttle is moving down the ECU adds fuel to the
engine." Does "throttle is moving down" refer to WOT?

3. "If you see the air/fuel ratio go lean as the throttle goes down
then come back to normal, add more fuel to the acceleration zone."
Can someone clarify this? If you're at idle or cruising along you
are already lean? Correct? What is "normal"? At cruise 'lean' is
normal. At WOT 'rich' is normal. Would the following be correct?
'If you see the air/fuel ratio stays lean as the throttle goes down
then goes rich, add more fuel to the acceleration zone.'

4. "If the air/fuel ratio stay rich, but dips lean before
stabilizing, then lengthen the acceleration decay time."
Does "stay rich" mean 'goes rich'? Would the following be correct?
'If the air/fuel ratio goes rich, but dips lean before
stabilizing, then lengthen the acceleration decay time.'

Sorry to be such a nit-pick, but I'm really struggling to
understand how to tune the ACCEL & DECAY.
Any tips, suggestions, and comments much appreciated.

Thanks,
Jim in Tucson

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

It includes any downward motion of the loud pedal, whether it ends up at =
wot or not.
----- Original Message -----=20
From: (email redacted)=20


1. "Simulates the accelerator pump on a carburetor by=20
increasing the amount of fuel upon sudden throttle opening."=20
Does "sudden throttle opening" refer to going WOT?=20

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


Does Jim's synopsis hold true for the full Link as well?

Thanks,
Robert
_________________________________________________________________
Get your FREE download of MSN Explorer at explorer.msn.com

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

Based on my experience with the piggyback:

With zero or too little accel fuel, you will get "lean tip-in". What this
means is, that you can be cruising along with the A/F cycling around stoich,
then you push your right foot down, and the A/F goes lean for a short
period, before going rich. The "short period" may be half a second or less,
hard to say how long really; how it looks on the gauge depends in part on
the responsiveness of the O2 sensor and of the A/F gauge. If you're seeing
that, turn up the appropriate accel value (appropriate RPM range). You'll
know when you've gone too far, because a couple bad things will start to
happen if you do: you'll get a short bog or mis-fire on tip-in, and misses
and stumbling after brief "pokes" of the throttle (the latter esp if decay
is too high). Just try to dial it in so that you get the best throttle
response you can.

BTW, I was never able to entirely eliminate lean tip-in with the piggyback,
both with and without the O2 clamp installed, but even so, I couldn't detect
any knocking on throttle tip-in. OK from an "engine safety" viewpoint, less
than ideal in terms of absolute throttle response.

Hope that helps. -Ed
-----Original Message-----
From: (email redacted)
[mailto:(email redacted)]On Behalf Of (email redacted)
Sent: Monday, July 16, 2001 1:22 AM
To: (email redacted)
Subject: Accel & Decay - Piggy-back


Quotes from piggy-back manual:

ACCEL: (Z16-Z19) Simulates the accelerator pump on a carburetor by
increasing the amount of fuel upon sudden throttle opening. The zones
affect the following RPM ranges:
Z16: 0 to 2000 RPM
Z17: 2001 to 4000 RPM
Z18: 4001 to 6000 RPM
Z19: 6001 to 8000 RPM

ACCEL DECAY: (Z20) Controls the decay time of the accelerator pump fuel.
Lower numbers offer faster decay. These numbers are not seconds.

SETUP:
The ECU has an accelerator pump feature. When the throttle is moving
down the ECU adds fuel to the engine. If you see the air/fuel ratio go
lean
as the throttle goes down then come back to normal, add more fuel to the
acceleration zone. If the air/fuel ratio stay rich, but dips lean before
stabilizing, then lengthen the acceleration decay time.

(end quotes)

Questions:
1. "Simulates the accelerator pump on a carburetor by
increasing the amount of fuel upon sudden throttle opening."
Does "sudden throttle opening" refer to going WOT?

2. "When the throttle is moving down the ECU adds fuel to the
engine." Does "throttle is moving down" refer to WOT?

3. "If you see the air/fuel ratio go lean as the throttle goes down
then come back to normal, add more fuel to the acceleration zone."
Can someone clarify this? If you're at idle or cruising along you
are already lean? Correct? What is "normal"? At cruise 'lean' is
normal. At WOT 'rich' is normal. Would the following be correct?
'If you see the air/fuel ratio stays lean as the throttle goes down
then goes rich, add more fuel to the acceleration zone.'

4. "If the air/fuel ratio stay rich, but dips lean before
stabilizing, then lengthen the acceleration decay time."
Does "stay rich" mean 'goes rich'? Would the following be correct?
'If the air/fuel ratio goes rich, but dips lean before
stabilizing, then lengthen the acceleration decay time.'

Sorry to be such a nit-pick, but I'm really struggling to
understand how to tune the ACCEL & DECAY.
Any tips, suggestions, and comments much appreciated.

Thanks,
Jim in Tucson

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


Yes, except that the decay is preset for FM2 setups.

----- Original Message -----
From: "Robert Mangas" <(email redacted)>
To: <(email redacted)>; <(email redacted)>
Sent: Monday, July 16, 2001 3:14 PM
Subject: Re: Accel & Decay - Piggy-back


>
> Does Jim's synopsis hold true for the full Link as well?
>
> Thanks,
> Robert
> _________________________________________________________________
> Get your FREE download of MSN Explorer at explorer.msn.com
>
>

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

Ed,

Good observations. Keep in mind it is possible to open the throttle slowly
enough to not trigger the ACCEL fuel. I have done this during tuning runs.

The responsiveness of the air/fuel gauge is a touch delayed. When tuning
pay attention to how the car feels as well as the gauge. If you have a
moment of leanness without knock or hesitation you are in good shape. A bog
on acceleration always means too much fuel.


Ken Hill
Flyin' Miata
1-800-FLYMX5S orders
1-970-242-3800 tech onfo
(email redacted)
www.flyinmiata.com

-----Original Message-----
From: Ed Cheal [mailto:(email redacted)]
Sent: Monday, July 16, 2001 9:49 AM
To: (email redacted); MiataPower
Subject: RE: Accel & Decay - Piggy-back


Based on my experience with the piggyback:

With zero or too little accel fuel, you will get "lean tip-in". What this
means is, that you can be cruising along with the A/F cycling around stoich,
then you push your right foot down, and the A/F goes lean for a short
period, before going rich. The "short period" may be half a second or less,
hard to say how long really; how it looks on the gauge depends in part on
the responsiveness of the O2 sensor and of the A/F gauge. If you're seeing
that, turn up the appropriate accel value (appropriate RPM range). You'll
know when you've gone too far, because a couple bad things will start to
happen if you do: you'll get a short bog or mis-fire on tip-in, and misses
and stumbling after brief "pokes" of the throttle (the latter esp if decay
is too high). Just try to dial it in so that you get the best throttle
response you can.

BTW, I was never able to entirely eliminate lean tip-in with the piggyback,
both with and without the O2 clamp installed, but even so, I couldn't detect
any knocking on throttle tip-in. OK from an "engine safety" viewpoint, less
than ideal in terms of absolute throttle response.

Hope that helps. -Ed

-----Original Message-----
From: (email redacted) [mailto:(email redacted)]On
Behalf Of (email redacted)
Sent: Monday, July 16, 2001 1:22 AM
To: (email redacted)
Subject: Accel & Decay - Piggy-back


Quotes from piggy-back manual:

ACCEL: (Z16-Z19) Simulates the accelerator pump on a carburetor by
increasing the amount of fuel upon sudden throttle opening. The zones
affect the following RPM ranges:
Z16: 0 to 2000 RPM
Z17: 2001 to 4000 RPM
Z18: 4001 to 6000 RPM
Z19: 6001 to 8000 RPM

ACCEL DECAY: (Z20) Controls the decay time of the accelerator pump fuel.
Lower numbers offer faster decay. These numbers are not seconds.

SETUP:
The ECU has an accelerator pump feature. When the throttle is moving
down the ECU adds fuel to the engine. If you see the air/fuel ratio go lean
as the throttle goes down then come back to normal, add more fuel to the
acceleration zone. If the air/fuel ratio stay rich, but dips lean before
stabilizing, then lengthen the acceleration decay time.

(end quotes)

Questions:
1. "Simulates the accelerator pump on a carburetor by
increasing the amount of fuel upon sudden throttle opening."
Does "sudden throttle opening" refer to going WOT?

2. "When the throttle is moving down the ECU adds fuel to the
engine." Does "throttle is moving down" refer to WOT?

3. "If you see the air/fuel ratio go lean as the throttle goes down
then come back to normal, add more fuel to the acceleration zone."
Can someone clarify this? If you're at idle or cruising along you
are already lean? Correct? What is "normal"? At cruise 'lean' is
normal. At WOT 'rich' is normal. Would the following be correct?
'If you see the air/fuel ratio stays lean as the throttle goes down
then goes rich, add more fuel to the acceleration zone.'

4. "If the air/fuel ratio stay rich, but dips lean before
stabilizing, then lengthen the acceleration decay time."
Does "stay rich" mean 'goes rich'? Would the following be correct?
'If the air/fuel ratio goes rich, but dips lean before
stabilizing, then lengthen the acceleration decay time.'

Sorry to be such a nit-pick, but I'm really struggling to
understand how to tune the ACCEL & DECAY.
Any tips, suggestions, and comments much appreciated.

Thanks,
Jim in Tucson

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

Thanks Ken,
I think I'm getting a better understanding of how the piggyback is trying to
work.

It appears to me that the ECU tries very hard to maintain stoich
A/F ratio and only goes open loop in two instances: (1) if rpms are
above 4K rpm, or (2) rpms are less that 4K rpm and go peddle is WOT.

Whether tuning the rows or adding ACCEL fuel below 4K rpm, the ECU
appears to try its best to pull out fuel as fast as I can add fuel.
This means that if I turn ACCEL way up to override the ECU, so to speak,
to get a richer condition at partial throttle, then at WOT there is way too
much fuel and engine gags and sputters.

There is also a trouble spot at exactly 4K rpm, where there is a sudden
change of condition from lean (or at least leaner than desired) to rich, when
the ECU suddenly goes open loop. This happens so quickly that it often causes
an engine cough in the higher gears.

I have not figured out how to effect any change in any of this, but I at
least can change my driving habits accordingly. In in-town traffic with
brisk acceleration I used to short shift at about 4K+ rpm which then
dropped the revs to about 3,700 on the up-shift. So I was constantly
driving 'through' the 4K rpm trouble spot. Now I simply adjust my driving
to avoid passing through 4K rpm in the higher gears when accelerating.

Has anyone else seen anything similar with their M2?

Jim in Tucson



In a message dated 7/16/01 8:41:30 AM US Mountain Standard Time,
(email redacted) writes:
>
>
> Since I wrote the manual, perhaps I would be the best person to explain
> what is says. See my comments below.
>
> Ken Hill
> Flyin' Miata
> 1-800-FLYMX5S orders
> 1-970-242-3800 tech onfo
> (email redacted)
> www.flyinmiata.com
>
> >> -----Original Message-----
>> From: (email redacted) [mailto:(email redacted)]
>> Sent: Sunday, July 15, 2001 11:22 PM
>> To: (email redacted)
>> Subject: Accel & Decay - Piggy-back
>>
>>
>> Quotes from piggy-back manual:
>>
>> ACCEL: (Z16-Z19) Simulates the accelerator pump on a carburetor by
>> increasing the amount of fuel upon sudden throttle opening. The zones
>> affect the following RPM ranges:
>> Z16: 0 to 2000 RPM
>> Z17: 2001 to 4000 RPM
>> Z18: 4001 to 6000 RPM
>> Z19: 6001 to 8000 RPM
>>
>> ACCEL DECAY: (Z20) Controls the decay time of the accelerator pump fuel.
>> Lower numbers offer faster decay. These numbers are not seconds.
>>
>> SETUP:
>> The ECU has an accelerator pump feature. When the throttle is moving
>> down the ECU adds fuel to the engine. If you see the air/fuel ratio go
>> lean
>> as the throttle goes down then come back to normal, add more fuel to the
>> acceleration zone. If the air/fuel ratio stay rich, but dips lean before
>> stabilizing, then lengthen the acceleration decay time.
>>
>> (end quotes)
>>
>> Questions:
>> 1. "Simulates the accelerator pump on a carburetor by
>> increasing the amount of fuel upon sudden throttle opening."
>> Does "sudden throttle opening" refer to going WOT?
>>
>> 2. "When the throttle is moving down the ECU adds fuel to the
>> engine." Does "throttle is moving down" refer to WOT?
>>
>> [Ken] Both statements mean the same thing; when the throttle is moved
>> down. This has no bearing on weather you open the throttle completely
>> open or stop somewhere short of wide open. When the Link ECU sees a rise
>> in MAP above a certain value in a certain time (i.e. the throttle opening
>> quickly) the ACCEL fuel in added to the engine.
>>
>> 3. "If you see the air/fuel ratio go lean as the throttle goes down
>> then come back to normal, add more fuel to the acceleration zone."
>> Can someone clarify this? If you're at idle or cruising along you
>> are already lean? Correct? What is "normal"? At cruise 'lean' is
>> normal. At WOT 'rich' is normal. Would the following be correct?
>> 'If you see the air/fuel ratio stays lean as the throttle goes down
>> then goes rich, add more fuel to the acceleration zone.'
>>
>> [Ken] When you are cruising along in row 2 then the car is running quite
>> lean. Opening the throttle to about 4-5psi (Row 4) should bring the
>> air/fuel reading up to the first green LED and stay there. If you open
>> the throttle and stay in row 2 or three then the air/fuel should not
>> increase much because you are not entering a boosted row.
>>
>> 4. "If the air/fuel ratio stay rich, but dips lean before
>> stabilizing, then lengthen the acceleration decay time."
>> Does "stay rich" mean 'goes rich'? Would the following be correct?
>> 'If the air/fuel ratio goes rich, but dips lean before
>> stabilizing, then lengthen the acceleration decay time.'
>>
>> [Ken] Yes, your statement is correct.
>>
>> Sorry to be such a nit-pick, but I'm really struggling to
>> understand how to tune the ACCEL & DECAY.
>> Any tips, suggestions, and comments much appreciated.
>>
>> Thanks,
>> Jim in Tucson
>>
>>
>>
>
>
>
>
>

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

The part about the ECU going from closed loop to open loop sounds basically
right, but I don't think WOT (foot-to-the-floor) is required, exactly, below
4k rpm, maybe only 3/4 throttle? Actually I think required throttle position
(for ECU to go open loop) is a more complex function of rpm. I seem to
recall Bill C. saying something definitive about this (I'd suggest searching
the archives, *if* search is working these days).

You do realize that the extra fuel added by the ACCEL funtion is very
transient, something like 0.25 to 0.5 secs, depending on the DECAY setting,
right? I'm sure Ken could be more definitive here. My advice is that if you
are getting transient misses ("gags and sputters") when you fully step into
it (i.e. push foot to the floor), that clears up after a sec or two of your
foot reaching the floor, and that reducing the ACCEL setting makes this go
away, then reduce the ACCEL setting to make this go away. Sorry if that
seems a bit too obvious. And when you do that, are you getting any
perceptible knocking that occurs transiently (i.e. for a sec or less), when
you step on the go pedal? If not, life is good (at least as far as the ACCEL
setting goes). BTW, if the "gags and sputters" don't clear up after a sec or
two when going WOT, then the problem isn't ACCEL, and you should look
elsewhere (fuel map, timing, spark plugs, wires, plug gap, etc).

As far as dealing with the open loop to closed loop transitions, this is an
issue that is inherent to the piggyback setup. But frankly, I found it to be
quite acceptable, if you get your pb settings dialed in OK. ONSET, the ACCEL
settings, and the 300 row (probably in that order) are most important for
getting good throttle response, and for dealing with the ECU closed loop to
open loop transitions. Of course the upper rows are important too, just not
the topic here.

And I never had the "engine cough" at 4k rpm that you describe, so I'm not
sure what's causing that for you. This happens in the middle of an
accelleration run, when you pass through 4k rpm? If so, its not related to
ACCEL, and sounds more like a problem with your fuel and/or timing there.
Does it happen at partial throttle runs, full throttle runs, or all of the
above (in other words, does it happen in the 300 row, 400 row, 500 row, all
three, or what)? From my experience, I could observe the open loop to closed
loop transition, but that (in and of itself) wouldn't cause my engine
miss-fire. I'd guess you have something else going on there.

Good luck, it sounds like you're making progress. -Ed

-----Original Message-----
From: (email redacted)
[mailto:(email redacted)]On Behalf Of (email redacted)
Sent: Tuesday, July 17, 2001 1:41 AM
To: (email redacted); (email redacted)
Subject: Re: Accel & Decay - Piggy-back


Thanks Ken,
I think I'm getting a better understanding of how the piggyback is trying
to
work.

It appears to me that the ECU tries very hard to maintain stoich
A/F ratio and only goes open loop in two instances: (1) if rpms are
above 4K rpm, or (2) rpms are less that 4K rpm and go peddle is WOT.

Whether tuning the rows or adding ACCEL fuel below 4K rpm, the ECU
appears to try its best to pull out fuel as fast as I can add fuel.
This means that if I turn ACCEL way up to override the ECU, so to speak,
to get a richer condition at partial throttle, then at WOT there is way
too
much fuel and engine gags and sputters.

There is also a trouble spot at exactly 4K rpm, where there is a sudden
change of condition from lean (or at least leaner than desired) to rich,
when
the ECU suddenly goes open loop. This happens so quickly that it often
causes
an engine cough in the higher gears.

I have not figured out how to effect any change in any of this, but I at
least can change my driving habits accordingly. In in-town traffic with
brisk acceleration I used to short shift at about 4K+ rpm which then
dropped the revs to about 3,700 on the up-shift. So I was constantly
driving 'through' the 4K rpm trouble spot. Now I simply adjust my driving
to avoid passing through 4K rpm in the higher gears when accelerating.

Has anyone else seen anything similar with their M2?

Jim in Tucson



In a message dated 7/16/01 8:41:30 AM US Mountain Standard Time,
(email redacted) writes:



Since I wrote the manual, perhaps I would be the best person to explain
what is says. See my comments below.

Ken Hill
Flyin' Miata
1-800-FLYMX5S orders
1-970-242-3800 tech onfo
(email redacted)
www.flyinmiata.com


-----Original Message-----
From: (email redacted) [mailto:(email redacted)]
Sent: Sunday, July 15, 2001 11:22 PM
To: (email redacted)
Subject: Accel & Decay - Piggy-back


Quotes from piggy-back manual:

ACCEL: (Z16-Z19) Simulates the accelerator pump on a carburetor by
increasing the amount of fuel upon sudden throttle opening. The zones
affect the following RPM ranges:
Z16: 0 to 2000 RPM
Z17: 2001 to 4000 RPM
Z18: 4001 to 6000 RPM
Z19: 6001 to 8000 RPM

ACCEL DECAY: (Z20) Controls the decay time of the accelerator pump
fuel.
Lower numbers offer faster decay. These numbers are not seconds.

SETUP:
The ECU has an accelerator pump feature. When the throttle is moving
down the ECU adds fuel to the engine. If you see the air/fuel ratio go
lean
as the throttle goes down then come back to normal, add more fuel to
the
acceleration zone. If the air/fuel ratio stay rich, but dips lean
before
stabilizing, then lengthen the acceleration decay time.

(end quotes)

Questions:
1. "Simulates the accelerator pump on a carburetor by
increasing the amount of fuel upon sudden throttle opening."
Does "sudden throttle opening" refer to going WOT?

2. "When the throttle is moving down the ECU adds fuel to the
engine." Does "throttle is moving down" refer to WOT?

[Ken] Both statements mean the same thing; when the throttle is moved
down. This has no bearing on weather you open the throttle completely
open or stop somewhere short of wide open. When the Link ECU sees a
rise
in MAP above a certain value in a certain time (i.e. the throttle
opening
quickly) the ACCEL fuel in added to the engine.

3. "If you see the air/fuel ratio go lean as the throttle goes down
then come back to normal, add more fuel to the acceleration zone."
Can someone clarify this? If you're at idle or cruising along you
are already lean? Correct? What is "normal"? At cruise 'lean' is
normal. At WOT 'rich' is normal. Would the following be correct?
'If you see the air/fuel ratio stays lean as the throttle goes down
then goes rich, add more fuel to the acceleration zone.'

[Ken] When you are cruising along in row 2 then the car is running
quite
lean. Opening the throttle to about 4-5psi (Row 4) should bring the
air/fuel reading up to the first green LED and stay there. If you
open
the throttle and stay in row 2 or three then the air/fuel should not
increase much because you are not entering a boosted row.

4. "If the air/fuel ratio stay rich, but dips lean before
stabilizing, then lengthen the acceleration decay time."
Does "stay rich" mean 'goes rich'? Would the following be correct?
'If the air/fuel ratio goes rich, but dips lean before
stabilizing, then lengthen the acceleration decay time.'

[Ken] Yes, your statement is correct.

Sorry to be such a nit-pick, but I'm really struggling to
understand how to tune the ACCEL & DECAY.
Any tips, suggestions, and comments much appreciated.

Thanks,
Jim in Tucson

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

>From watching the obdii monitor, looks like it takes about 75% tps to go
open loop below 4k, only 15-17% to go open above 4k. I'm with Ed on not
being able to feel that transition, maybe plug gaps or something else
unrelated to the poor piggy.


Bill Cardell
(email redacted)
Flyin' Miata
flyinmiata.com <flyinmiata.com/>
200mphmiata.net <200mphmiata.net/>
1-800-FLY-MX5S (orders only)
1-970-242-3800 (tech)


-----Original Message-----
From: Ed Cheal [mailto:(email redacted)]
Sent: Tuesday, July 17, 2001 9:20 AM
To: (email redacted); MiataPower
Subject: RE: Accel & Decay - Piggy-back


The part about the ECU going from closed loop to open loop sounds basically
right, but I don't think WOT (foot-to-the-floor) is required, exactly, below
4k rpm, maybe only 3/4 throttle? Actually I think required throttle position
(for ECU to go open loop) is a more complex function of rpm. I seem to
recall Bill C. saying something definitive about this (I'd suggest searching
the archives, *if* search is working these days).

You do realize that the extra fuel added by the ACCEL funtion is very
transient, something like 0.25 to 0.5 secs, depending on the DECAY setting,
right? I'm sure Ken could be more definitive here. My advice is that if you
are getting transient misses ("gags and sputters") when you fully step into
it (i.e. push foot to the floor), that clears up after a sec or two of your
foot reaching the floor, and that reducing the ACCEL setting makes this go
away, then reduce the ACCEL setting to make this go away. Sorry if that
seems a bit too obvious. And when you do that, are you getting any
perceptible knocking that occurs transiently (i.e. for a sec or less), when
you step on the go pedal? If not, life is good (at least as far as the ACCEL
setting goes). BTW, if the "gags and sputters" don't clear up after a sec or
two when going WOT, then the problem isn't ACCEL, and you should look
elsewhere (fuel map, timing, spark plugs, wires, plug gap, etc).

As far as dealing with the open loop to closed loop transitions, this is an
issue that is inherent to the piggyback setup. But frankly, I found it to be
quite acceptable, if you get your pb settings dialed in OK. ONSET, the ACCEL
settings, and the 300 row (probably in that order) are most important for
getting good throttle response, and for dealing with the ECU closed loop to
open loop transitions. Of course the upper rows are important too, just not
the topic here.

And I never had the "engine cough" at 4k rpm that you describe, so I'm not
sure what's causing that for you. This happens in the middle of an
accelleration run, when you pass through 4k rpm? If so, its not related to
ACCEL, and sounds more like a problem with your fuel and/or timing there.
Does it happen at partial throttle runs, full throttle runs, or all of the
above (in other words, does it happen in the 300 row, 400 row, 500 row, all
three, or what)? From my experience, I could observe the open loop to closed
loop transition, but that (in and of itself) wouldn't cause my engine
miss-fire. I'd guess you have something else going on there.

Good luck, it sounds like you're making progress. -Ed


-----Original Message-----
From: (email redacted) [mailto:(email redacted)]On
Behalf Of (email redacted)
Sent: Tuesday, July 17, 2001 1:41 AM
To: (email redacted); (email redacted)
Subject: Re: Accel & Decay - Piggy-back


Thanks Ken,
I think I'm getting a better understanding of how the piggyback is trying to

work.

It appears to me that the ECU tries very hard to maintain stoich
A/F ratio and only goes open loop in two instances: (1) if rpms are
above 4K rpm, or (2) rpms are less that 4K rpm and go peddle is WOT.

Whether tuning the rows or adding ACCEL fuel below 4K rpm, the ECU
appears to try its best to pull out fuel as fast as I can add fuel.
This means that if I turn ACCEL way up to override the ECU, so to speak,
to get a richer condition at partial throttle, then at WOT there is way too
much fuel and engine gags and sputters.

There is also a trouble spot at exactly 4K rpm, where there is a sudden
change of condition from lean (or at least leaner than desired) to rich,
when
the ECU suddenly goes open loop. This happens so quickly that it often
causes
an engine cough in the higher gears.

I have not figured out how to effect any change in any of this, but I at
least can change my driving habits accordingly. In in-town traffic with
brisk acceleration I used to short shift at about 4K+ rpm which then
dropped the revs to about 3,700 on the up-shift. So I was constantly
driving 'through' the 4K rpm trouble spot. Now I simply adjust my driving
to avoid passing through 4K rpm in the higher gears when accelerating.

Has anyone else seen anything similar with their M2?

Jim in Tucson



In a message dated 7/16/01 8:41:30 AM US Mountain Standard Time,
(email redacted) writes:




Since I wrote the manual, perhaps I would be the best person to explain
what is says. See my comments below.

Ken Hill
Flyin' Miata
1-800-FLYMX5S orders
1-970-242-3800 tech onfo
(email redacted)
www.flyinmiata.com



-----Original Message-----
From: (email redacted) [mailto:(email redacted)]
Sent: Sunday, July 15, 2001 11:22 PM
To: (email redacted)
Subject: Accel & Decay - Piggy-back


Quotes from piggy-back manual:

ACCEL: (Z16-Z19) Simulates the accelerator pump on a carburetor by
increasing the amount of fuel upon sudden throttle opening. The zones
affect the following RPM ranges:
Z16: 0 to 2000 RPM
Z17: 2001 to 4000 RPM
Z18: 4001 to 6000 RPM
Z19: 6001 to 8000 RPM

ACCEL DECAY: (Z20) Controls the decay time of the accelerator pump fuel.
Lower numbers offer faster decay. These numbers are not seconds.

SETUP:
The ECU has an accelerator pump feature. When the throttle is moving
down the ECU adds fuel to the engine. If you see the air/fuel ratio go
lean
as the throttle goes down then come back to normal, add more fuel to the
acceleration zone. If the air/fuel ratio stay rich, but dips lean before
stabilizing, then lengthen the acceleration decay time.

(end quotes)

Questions:
1. "Simulates the accelerator pump on a carburetor by
increasing the amount of fuel upon sudden throttle opening."
Does "sudden throttle opening" refer to going WOT?

2. "When the throttle is moving down the ECU adds fuel to the
engine." Does "throttle is moving down" refer to WOT?

[Ken] Both statements mean the same thing; when the throttle is moved
down. This has no bearing on weather you open the throttle completely
open or stop somewhere short of wide open. When the Link ECU sees a rise
in MAP above a certain value in a certain time (i.e. the throttle opening
quickly) the ACCEL fuel in added to the engine.

3. "If you see the air/fuel ratio go lean as the throttle goes down
then come back to normal, add more fuel to the acceleration zone."
Can someone clarify this? If you're at idle or cruising along you
are already lean? Correct? What is "normal"? At cruise 'lean' is
normal. At WOT 'rich' is normal. Would the following be correct?
'If you see the air/fuel ratio stays lean as the throttle goes down
then goes rich, add more fuel to the acceleration zone.'

[Ken] When you are cruising along in row 2 then the car is running quite
lean. Opening the throttle to about 4-5psi (Row 4) should bring the
air/fuel reading up to the first green LED and stay there. If you open
the throttle and stay in row 2 or three then the air/fuel should not
increase much because you are not entering a boosted row.

4. "If the air/fuel ratio stay rich, but dips lean before
stabilizing, then lengthen the acceleration decay time."
Does "stay rich" mean 'goes rich'? Would the following be correct?
'If the air/fuel ratio goes rich, but dips lean before
stabilizing, then lengthen the acceleration decay time.'

[Ken] Yes, your statement is correct.

Sorry to be such a nit-pick, but I'm really struggling to
understand how to tune the ACCEL & DECAY.
Any tips, suggestions, and comments much appreciated.

Thanks,
Jim in Tucson