Help with tuning with HPTuners

930 Views 65 Replies 2 Participants Last post by dezldave961, 23 d ago

Turbogn

Discussion Starter · 2 mo ago

I have a 1988 Fiero GT with an L32. I took it out for its first run this spring and I'm showing 4-5 degrees of KR & running a little lean at 105 Kpa manifold pressure and at different points I'm also seeing super rich values. I have been at the HP Tuners forum for help but I'm just getting the feeling that if it's not an LS then they're not interested.
I've been getting responses like;

1) "3800 computers are super basic, there is almost no tables on those computers.
Anything you see on youtube that uses a LS based V8 computer will have 10x the amount of tables. The 3800's are MAF based and very simple."

2) "those ecm's do not offer an custom operating systems, what you see under the tabs is what you get for these older ecms. "

3) "speed density custom operating systems have absolutely nothing to do with adjusting for knock retard and fueling. "
My main question is, How are people tuning their 3800's if HP Tuners is useless for it according to HP Tuners?

1 - 20 of 66 Posts

dezldave961

· #2 · 2 mo ago

Most people who actually do 3800 tuning are no longer actively posting online. The basic adjustments getting into boost are under Acceleration Enrichment and the Power Enrichment enabling throttle. There are a few tables that will add modifiers to your PE A/F based on time, coolant temp, air temp, etc. that you might see while in there.

They're right in that it doesn't require many tables, and once you have the basic setup tweaks taken care of, you'll just be doing minor adjustments to your MAF curve. Scanning it with your Long Term Fuel Trims to know the %diff across a longer scan for each MAF cell range will provide information to adjust the tune (a spreadsheet or their built-in tools on HPT may help). For boost (PE engaged, open loop fueling), you'll want to compare commanded AFR to actual from a wideband (using the stock narrowband isn't optimal for this effort).

As you learn what it likes, you'll make it more reliable and predictable for long term comfort.

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Turbogn

Discussion Starter · #3 · 2 mo ago

dezldave961 said:
Most people who actually do 3800 tuning are no longer actively posting online. The basic adjustments getting into boost are under Acceleration Enrichment and the Power Enrichment enabling throttle. There are a few tables that will add modifiers to your PE A/F based on time, coolant temp, air temp, etc. that you might see while in there.

They're right in that it doesn't require many tables, and once you have the basic setup tweaks taken care of, you'll just be doing minor adjustments to your MAF curve. Scanning it with your Long Term Fuel Trims to know the %diff across a longer scan for each MAF cell range will provide information to adjust the tune (a spreadsheet or their built-in tools on HPT may help). For boost (PE engaged, open loop fueling), you'll want to compare commanded AFR to actual from a wideband (using the stock narrowband isn't optimal for this effort).

As you learn what it likes, you'll make it more reliable and predictable for long term comfort.

Thank you very much for the information. Being new to HPTuners I'm finding it hard to get information on where and what to change to achieve the results I'm looking for.

Turbogn

Discussion Starter · #4 · 2 mo ago

One problem I noticed is the MAP sensor seems to be reading incorrectly. In the data I see it thinks I'm at 20 - 28 psi under WOT but my boost gauge is showing a max of 11 psi.

dezldave961

· #5 · 2 mo ago

Do you have the standard settings for scaling? These PCM's aren't able to get tuned enough to change the MAP range, so you can either run an N/A tune with the 1-bar MAP, or S/C tune with a 2-bar. People who dug deep for a few years during the 3800 peak had tried to do 3-bar swaps, but it's not thorough enough to cover all the tables that get it right, aside from the rare person who went well beyond consumer-level access.

Turbogn

Discussion Starter · #6 · 2 mo ago

dezldave961 said:
Do you have the standard settings for scaling? These PCM's aren't able to get tuned enough to change the MAP range, so you can either run an N/A tune with the 1-bar MAP, or S/C tune with a 2-bar. People who dug deep for a few years during the 3800 peak had tried to do 3-bar swaps, but it's not thorough enough to cover all the tables that get it right, aside from the rare person who went well beyond consumer-level access.

I don't even know. I had to replace the MAP sensor last fall and bought a stock one.

dezldave961

· #7 · 2 mo ago

Wondering if you got an N/A one that's confusing your S/C tune.

Turbogn

Discussion Starter · #8 · 2 mo ago

dezldave961 said:
Wondering if you got an N/A one that's confusing your S/C tune.

It's possible. When I looked for one none of the stores agree on what to use. I would check the part number and only one store would say it fits. I would check another one and same deal, only one place would say it fits, the other ones would say "does not fit". Even GM doesn't seem to know what to use.
I also replaced my vacuum hose going to up to it and that didn't change anything.

dezldave961

· #9 · 2 mo ago

Stores aren't equipped to decipher small nuances between engines of the same overall type. Best bet is to snag one at a junkyard. MAP sensors don't tend to go bad, and non-OEM sensors of all types usually have a shorter lifespan.

Turbogn

Discussion Starter · #10 · 2 mo ago

dezldave961 said:
Stores aren't equipped to decipher small nuances between engines of the same overall type. Best bet is to snag one at a junkyard. MAP sensors don't tend to go bad, and non-OEM sensors of all types usually have a shorter lifespan.

Ok, Thanks.

Turbogn

Discussion Starter · #11 · 2 mo ago

Off hand do you know what lb/hr the stock injectors are?

dezldave961

· #12 · 2 mo ago

They're 36# for L67 and 33# for L32, I believe. I'd have to dig for exact figures on some servicing and sales sites like witchhunter or racetronix, but OEM tables should be available from stock files floating around (I should probably browse this forum from my laptop rather than phone for situations like this).

Turbogn

Discussion Starter · #13 · 2 mo ago

dezldave961 said:
They're 36# for L67 and 33# for L32, I believe. I'd have to dig for exact figures on some servicing and sales sites like witchhunter or racetronix, but OEM tables should be available from stock files floating around (I should probably browse this forum from my laptop rather than phone for situations like this).

The only figure I could find was in g/min and when I converted it to lb/hr it came out to be 34.4. The tuner had the flow rate set for 38# by the looks of it, not sure why when the tune is even listed as stock injectors.

dezldave961

· #14 · 2 mo ago

That's about right. It'll work for how much adjustment gets applied by the rest of the fueling calculations from the MAF table for most running conditions.

Fuel trims have ±16-22% adjustment in both directions, although it's best to target single digits on LTFT's for most of your time, once the Closed Loop (idle/cruise/normal driving) is set. Note that STFT's are the instantaneous reaction to MAF/O2 readings to try getting to 14.7:1 AFR, which the LTFT's will slowly average in over time at that cell, if it needs to remain at that number to stay happy (and STFT's will drop to ~0 if it's content with the LTFT value after a while).

Moving into boost is another thing, where you want your MAF curve to drive things, because LTFT's lock at whatever they're at when you enter PE/boost. Big reason to A) have them as low as possible, or B) turn off LTFT's for this mode, but you'll want a wideband to monitor better.

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Turbogn

Discussion Starter · #15 · 2 mo ago

dezldave961 said:
That's about right. It'll work for how much adjustment gets applied by the rest of the fueling calculations from the MAF table for most running conditions.

Fuel trims have ±16-22% adjustment in both directions, although it's best to target single digits on LTFT's for most of your time, once the Closed Loop (idle/cruise/normal driving) is set. Note that STFT's are the instantaneous reaction to MAF/O2 readings to try getting to 14.7:1 AFR, which the LTFT's will slowly average in over time at that cell, if it needs to remain at that number to stay happy (and STFT's will drop to ~0 if it's content with the LTFT value after a while).

Moving into boost is another thing, where you want your MAF curve to drive things, because LTFT's lock at whatever they're at when you enter PE/boost. Big reason to A) have them as low as possible, or B) turn off LTFT's for this mode, but you'll want a wideband to monitor better.

Where is the best place to start making adjustments to get the LTFT's down to single digits?

dezldave961

· #16 · 2 mo ago

MAF table tweaks, based on logging the %diff in the ranges between 1500-5000-ish. After that, keep the transition smooth to the boosted area of the curve.

Turbogn

Discussion Starter · #17 · 2 mo ago

dezldave961 said:
MAF table tweaks, based on logging the %diff in the ranges between 1500-5000-ish. After that, keep the transition smooth to the boosted area of the curve.

Thanks for the help.

Turbogn

Discussion Starter · #18 · 2 mo ago

dezldave961 said:
MAF table tweaks, based on logging the %diff in the ranges between 1500-5000-ish. After that, keep the transition smooth to the boosted area of the curve.

I've been tweaking the MAF table today and nothing seems to work right. If I go up on the values that should be adding more fuel, correct?
I can get the MAF error down, but then the fuel trims are way out at -20 or so.
If I go by the AFR and get that close, then it barely wants to run.
It's like everything is fighting each other.
I set the MAF back to the Northstar table and then did a log with a few revs. I was going to upload it but it keeps coming up with "not an allowed extension".

dezldave961

· #19 · 2 mo ago

Unless you're scanning with a WB, don't worry about changing AFR settings at this point, as that only comes into play for boost, which you should be avoiding until crawl/walk are taken care of. The LTFT's should be telling you the reaction it wants for getting towards 14.7:1 (the NB O2 is good at that).

You also need to make sure you're dealing with a healthy engine (no vac/exhaust leaks, etc.), or you'll chase your tail to the moon.

Can't help with the extension thing, sounds like something simple getting done wrong. Don't feel too attached to MAF tables standardized for anything, because the point of the tuning is to tailor it to your car's demands.

Turbogn

Discussion Starter · #20 · 2 mo ago

Looks like I have idle and cruise pretty close, no KR and WB is close to 14.7.
Now when I tune for boost and WOT is it the same procedure, or tuning different tables?

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