BZZRPM seems to have no effect (GUFB)

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Chucko
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BZZRPM seems to have no effect (GUFB)

Post by Chucko » Thu Jun 20, 2019 1:52 am

Long time no post... I still have an '89 Mustang with a mild 302 and a stick. I've been using BE and the Quarterhorse for years. But I've never figured this out.

I can change BZZRPM and BZZTM all I want, but they never seem to have any effect on the target idle speed coming out of crank.

The EEC is an A3M1 (GUFB). I'm using cgrey's GUFB defs v. 98.

Anyone else have this problem? Any ideas? I see that guy from New Orleans has moved on.
'89 LX 5.0, Crane 2040, Pro-M 75mm Bullet, 65 mm TB, ported stock intake & E7TE heads, 24 lb injs., JBA shortys, cat X-pipe, A3M1 (GUFB strategy) w/Moates Quarterhorse, BE & EA, close ratio T5Z, 3.55 rear

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Re: BZZRPM seems to have no effect (GUFB)

Post by cgrey8 » Thu Jun 20, 2019 6:47 am

According to the GUFB doc, it's a buzz-up RPM adder that's only in effect for the BZZTM time period (usually 3 seconds) after startup. I don't recall that I've ever used that scalar or even attempted to. Although looking at my tune, I see that my BZZTM is set to 5 (stock for both A9L & X3Z is 10). If I had to guess, the algorithm that this is attempting to influence is either not in effect or is simply over-powered by other aspects of the tune. If you are trying to manage startup idle RPM, there are far more effective controls than those scalars.

I've always controlled startup idle RPM (both cold and warm) from the ISC Startup Multipler table (FN1861) which allows you to increase the airflow to the engine based on ECT and time. I've found that FAR more effective at managing and controlling idle startup RPM. The intent of the table is to compensate for cold engines requiring more air to run than warm engines. However I use it purely to control startup RPM. In fact, I lowered it in the cold areas because the stock tune was "buzzing-up" the engine far higher than I thought was necessary. So I backed down those numbers. My suspicion is a lot of the stock values were driven by emissions requirements. Running the engine a little higher in the RPMs when near freezing cold burned more fuel which warmed the engine exhaust and CAT(s) up quicker which is probably why Ford set the values the way they did. Being I don't have that constraint, I manage the engine's startup RPMs far lower since the engine seems perfectly fine with that...and it saves gas. Comparing my tune to A9L and X3Z, my values in the warmer areas of the tune are actually higher than stock.

Another interesting thing I see I did as I look at my tune, the very bottom row is lower than the row above it. When I was tuning startup, the engine would buzz-up fairly high right off crank. But then 2-3 seconds after crank, it hesitated to nearly conking out. But then it'd catch itself and run fine from that point on. I never figured out what that was, but I compensated for that in this table too. First I rescaled the rows to 0,1,5,13,22,30. The first row is whatever values I found worked best to keep the buzz-up immediately after crank to a minimum. Then on the second row, which is 1 second into crank, I increase the ISC about 15% above what the line below is to compensate for the hesitation before it even begins. The third row is where I start pulling the ISC back, immediately after the hesitation-zone has passed. With the tune I run today, you'd never know that hesitation thing existed. It cranks controlled, smooth, and hesitation-free...warm or cold.

There's also an ISC Cranking PW function (FN884) that controls how far open the ISC is held during crank, before the engine actually turns over on its own power. I lowered those values by roughly 1/2 stock values to minimize the buzz-up. I found a lot of buzz-up comes from what the ISC is doing during this time period which makes sense given how big Ford upper intake plenums are. If I ever were to run E85, which takes noticeably more revolutions during cold-crank for the engine to catch, I might would have to revisit this function. But with pump gas, the engine is just barely beginning to lower the plenum vacuum by the time the first cylinder fires.

If anybody is aware of the startup-hesitation I'm describing and knows what causes that, I'd be really interested in understanding why the engine does that. Don't get me wrong, I'm happy with my compensation technique. It's quite effective. But I'd still like to understand the technicals that explain why the engine behaves this way.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

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Re: BZZRPM seems to have no effect (GUFB)

Post by Chucko » Thu Jun 20, 2019 10:12 pm

cgrey8 wrote:
Thu Jun 20, 2019 6:47 am
According to the GUFB doc, it's a buzz-up RPM adder that's only in effect for the BZZTM time period (usually 3 seconds) after startup. I don't recall that I've ever used that scalar or even attempted to. Although looking at my tune, I see that my BZZTM is set to 5 (stock for both A9L & X3Z is 10). If I had to guess, the algorithm that this is attempting to influence is either not in effect or is simply over-powered by other aspects of the tune. If you are trying to manage startup idle RPM, there are far more effective controls than those scalars.
In the GUFB strategy doc, it's not conditional - it's always supposed to apply immediately after crank. The page it's on is marked GUFA. The stated purpose is to burn off some of the excess fuel from crank phase.

It would be really useful, if it worked. Anyone got a stock Fox V8 to compare it to? (Yeah, I know, silly question around here.)

I may ask about this at decipha's forum.
cgrey8 wrote: I've always controlled startup idle RPM (both cold and warm) from the ISC Startup Multipler table (FN1861) which allows you to increase the airflow to the engine based on ECT and time. I've found that FAR more effective at managing and controlling idle startup RPM. The intent of the table is to compensate for cold engines requiring more air to run than warm engines. However I use it purely to control startup RPM. In fact, I lowered it in the cold areas because the stock tune was "buzzing-up" the engine far higher than I thought was necessary. So I backed down those numbers. My suspicion is a lot of the stock values were driven by emissions requirements. Running the engine a little higher in the RPMs when near freezing cold burned more fuel which warmed the engine exhaust and CAT(s) up quicker which is probably why Ford set the values the way they did. Being I don't have that constraint, I manage the engine's startup RPMs far lower since the engine seems perfectly fine with that...and it saves gas. Comparing my tune to A9L and X3Z, my values in the warmer areas of the tune are actually higher than stock.
I've actually changed my FN1861 quite a lot - through laboriously logging IPSIBR over a range of cold start temps. The factory settings were way conservative; I added quite a lot to most of the early or cold entries. With that dialed in, the idle RPM adders work the way they're intended. BZZRPM is the only exception. And if I could get that working, I wouldn't need any other hacks.
cgrey8 wrote: When I was tuning startup, the engine would buzz-up fairly high right off crank. But then 2-3 seconds after crank, it hesitated to nearly conking out. But then it'd catch itself and run fine from that point on. I never figured out what that was, but I compensated for that in this table too.
That stumble you describe is a lean-out, and it goes away if you add startup fuel in that region. I recently experienced it again after making big MAF curve changes in the idle region without clearing KAM.
cgrey8 wrote: There's also an ISC Cranking PW function (FN884) that controls how far open the ISC is held during crank, before the engine actually turns over on its own power. I lowered those values by roughly 1/2 stock values to minimize the buzz-up. I found a lot of buzz-up comes from what the ISC is doing during this time period which makes sense given how big Ford upper intake plenums are.
Yes, I've done something similar for the same reasons.
'89 LX 5.0, Crane 2040, Pro-M 75mm Bullet, 65 mm TB, ported stock intake & E7TE heads, 24 lb injs., JBA shortys, cat X-pipe, A3M1 (GUFB strategy) w/Moates Quarterhorse, BE & EA, close ratio T5Z, 3.55 rear

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Re: BZZRPM seems to have no effect (GUFB)

Post by Chucko » Mon Jul 22, 2019 9:40 pm

By going over the disassembled A9L listing, I figured out what the issue is.

BZZRPM and BZZTM are in fact working. It's just that we have the wrong scale factor for BZZTM - it's in seconds, not 1/8 seconds.

The factory value is 80 seconds, not 10 as we thought it was. So it's unlikely any of us waited around long enough to notice!

I set it to a more reasonable 5 seconds and get exactly the behavior I expected.
'89 LX 5.0, Crane 2040, Pro-M 75mm Bullet, 65 mm TB, ported stock intake & E7TE heads, 24 lb injs., JBA shortys, cat X-pipe, A3M1 (GUFB strategy) w/Moates Quarterhorse, BE & EA, close ratio T5Z, 3.55 rear

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Re: BZZRPM seems to have no effect (GUFB)

Post by cgrey8 » Tue Jul 23, 2019 6:17 am

This is an update needed to the def file? I'll try to remember to get that incorporated sometime this week. The GUFx defs hadn't been updated in quite some time, so it'll be nice to finally get v99 out into the wild.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

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Re: BZZRPM seems to have no effect (GUFB)

Post by EDS50 » Tue Jul 23, 2019 4:48 pm

The PIP Legend defines BZZTM Unit as seconds in the GUFB. Factory default is 10 seconds for A9L. I do see in the GUFB98 Excel that the equation is X/8. BZZRPM and many other idle scaler equations are also X/8. So if the disassembly shows a value of 80 then the 10 second default in the a9l is correct since the equation in the GUFB Excel is X/8 (80/8 = 10) which would mean that BZZRPM would be added for 10 seconds to idle at startup before expiring. Am I wrong in my thoughts?
1992 LX - 25.1c Chassis, Vortech Blown Dart 332, Lentech Trans, TRZ Backhalf, A9L, Moates QH/SL v1.9, BE, EA, TunerView

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Re: BZZRPM seems to have no effect (GUFB)

Post by Chucko » Tue Jul 23, 2019 10:06 pm

EDS50 wrote:
Tue Jul 23, 2019 4:48 pm
The PIP Legend defines BZZTM Unit as seconds in the GUFB. Factory default is 10 seconds for A9L. I do see in the GUFB98 Excel that the equation is X/8. BZZRPM and many other idle scaler equations are also X/8. So if the disassembly shows a value of 80 then the 10 second default in the a9l is correct since the equation in the GUFB Excel is X/8 (80/8 = 10) which would mean that BZZRPM would be added for 10 seconds to idle at startup before expiring. Am I wrong in my thoughts?
The GUFB document doesn't always specify the units of time precisely. It does always distinguish between seconds, background loops, and IO Timer ticks. But sometimes you have to go to the code to figure out if "seconds" means whole seconds, 1/8 seconds, or milliseconds.

The code that checks BZZTM in the A9L disassembly is based on ATMR1, which increments every second after exiting crank mode. I am absolutely certain of this. Any other disassembly hackers, feel free to double-check my work.

It seems kinda silly to add 64 RPM over the first 80 seconds after startup. But that's the value in the A9L and A3M1 binaries. Go figure.

Chris, if you were looking for an excuse to crank out GUFB v99, here you go.
'89 LX 5.0, Crane 2040, Pro-M 75mm Bullet, 65 mm TB, ported stock intake & E7TE heads, 24 lb injs., JBA shortys, cat X-pipe, A3M1 (GUFB strategy) w/Moates Quarterhorse, BE & EA, close ratio T5Z, 3.55 rear

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Re: BZZRPM seems to have no effect (GUFB)

Post by EDS50 » Tue Jul 23, 2019 10:10 pm

Thanks for the clarification, I like learning new things. From my experience; I had better luck using BZZRPM with my stick car but not so much with the aod car. The stick car idle was so much more temperamental.
1992 LX - 25.1c Chassis, Vortech Blown Dart 332, Lentech Trans, TRZ Backhalf, A9L, Moates QH/SL v1.9, BE, EA, TunerView

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