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?

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Turbogn

Discussion Starter · #61 · 28 d ago

I did a few quick tests and It seems that it has the voltage it should, and changes with pressure change......but.....there is always a but. To get the MAP and BARO to read 14.8 psi key on engine off I had to bump the MAP sensor offset all the way up to 38.50 kpa. With it now reading correctly at key on engine off I got the following voltage readings.

MAP reference voltage: 4.98v
Key on Engine off: 1.59v @ 14.8 psi/BARO 14.9 psi
2.14v @ 18.0 psi

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dezldave961

· #62 · 28 d ago

That drastic of a change from known good stock settings should NOT be the direction you try to go. It could temporarily cover for the actual problem, which may arise as you hit parts of the chart away from this baseline, and a significant fueling issue may result. I would reset and seek out other anomalous things going on with the system.

The car should think atmospheric pressure is ~0psi or so, with a ~100 kPa MAP reading. Yes, the absolute pressure at sea level is ~1bar (14.7psi), but when you move to a gauge pressure, it can shift the reference point for baseline for the system's needs. Basically, the car will consider key-on-engine-off as the normal condition, so 0psi/100kPa, that way any vacuum or boost applied by the engine running is showing the differential value from that baseline for purposes of fueling properly.

The standard pcm output is usually in kPa, with the psi usually being a derived calculation from that (HPT may think people can't math good, so they use the more common units).

Anyway, keep working in this direction. I'll be able to plug into my car in a couple days to give some more updated scan info (I usually don't hit "record" until the car's already running, but I can switch it up next time).

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Turbogn

Discussion Starter · #63 · 27 d ago

dezldave961 said:
That drastic of a change from known good stock settings should NOT be the direction you try to go. It could temporarily cover for the actual problem, which may arise as you hit parts of the chart away from this baseline, and a significant fueling issue may result. I would reset and seek out other anomalous things going on with the system.

The car should think atmospheric pressure is ~0psi or so, with a ~100 kPa MAP reading. Yes, the absolute pressure at sea level is ~1bar (14.7psi), but when you move to a gauge pressure, it can shift the reference point for baseline for the system's needs. Basically, the car will consider key-on-engine-off as the normal condition, so 0psi/100kPa, that way any vacuum or boost applied by the engine running is showing the differential value from that baseline for purposes of fueling properly.

The standard pcm output is usually in kPa, with the psi usually being a derived calculation from that (HPT may think people can't math good, so they use the more common units).

Anyway, keep working in this direction. I'll be able to plug into my car in a couple days to give some more updated scan info (I usually don't hit "record" until the car's already running, but I can switch it up next time).

I did some testing with a small compressor and probing the MAP sensor with a multimeter and came up with the following data.

@0 psi 1.58v
@4 psi 1.78v
@5 psi 1.84v
@8 psi 1.99v

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dezldave961

· #64 · 27 d ago

Have you done this with multiple known good sensors? This is the issue with single frame of reference readings that many people do. A coworker freaked this spring about a reading they never knew was a normal value, despite me saying it had been that value for months, because they didn't pay attention until the day it caught their eye.

I'm away from home, or I'd offer some comparable readings to calm your nerves.

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Turbogn

Discussion Starter · #65 · 23 d ago

As a last ditch effort, I bought another 12615136 and made sure it was an ACDelco. I installed it and put the Linear and offset back to 200 and 7.99. Now it seems to be staying in spec at both ends and the car seems to be running better. Before buying this sensor, I did a lot of research and found out that almost all of these sensors are listed as either a replacement for each other or for one that is no longer made. While looking through the specs I found some are listed with different specs for the same part number and were advertised as 2, 2.5, and 3 bar. What a nightmare this has been, I now doubt half the people out there even have a MAP sensor that is correct, and working properly anymore.
Thank you for everyone's help with this.

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dezldave961

· #66 · 23 d ago

Good to hear. I think majority of sensors never get a 2nd thought and keep working, thankfully. Unfortunately, once you isolate a part that vary in the same exact casing, it can get sketchy to know if it's the range you think... not to mention the possibility of failing as an aging electronic sensor.

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