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Turbo 5.3 possible tune issues

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Old 05-16-2018, 01:28 PM
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Default Turbo 5.3 possible tune issues

Hey guys I am going to try and break this down to make it easier to understand.
The vehicle.
2001 Silverado p01 ecu
3 bar ls1 style map from efisource
Gen iv intake with 92mm the
4l80 (separate controller)
on3 7875 turbo with fmic

The issue.
I tuned this using hptuners and so far I am running 10psi according to my boost gauge. AFR looks like it's supposed to. It ran good for the first 9-10 pulls I made at the dig spot, drove it home smoothly no issues. The next weekend when I did the pull it felt a little weak in higher boost range. And when I let out it misfires hard until I free rev in neutral then it's fine unless I try and boost again.

What I've tried
New wires/plugs
Vcm logs look okay.
coils are all firing at idle

What I'm questioning.
At 10psi it reads 135kpa
At idle it reads 70kpa
Does that seem correct? Or do I have a bad out of the box map sensor. Linear and offset where provided by efisource.

Any suggestions? Tia
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Old 05-16-2018, 01:50 PM
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Originally Posted by bbowerman View Post
Hey guys I am going to try and break this down to make it easier to understand.
The vehicle.
2001 Silverado p01 ecu
3 bar ls1 style map from efisource
Gen iv intake with 92mm the
4l80 (separate controller)
on3 7875 turbo with fmic

The issue.
I tuned this using hptuners and so far I am running 10psi according to my boost gauge. AFR looks like it's supposed to. It ran good for the first 9-10 pulls I made at the dig spot, drove it home smoothly no issues. The next weekend when I did the pull it felt a little weak in higher boost range. And when I let out it misfires hard until I free rev in neutral then it's fine unless I try and boost again.

What I've tried
New wires/plugs
Vcm logs look okay.
coils are all firing at idle

What I'm questioning.
At 10psi it reads 135kpa
At idle it reads 70kpa
Does that seem correct? Or do I have a bad out of the box map sensor. Linear and offset where provided by efisource.

Any suggestions? Tia
​​​​​
​​​​​​
​​​
70kPa does not sound right at idle unless it has a massive cam. Your boost kPa doesn't look right either since 100kPa is atmosphere, so you're only making about 5psi according to the computer/map, but your gauge shows 10 psi.
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Old 05-16-2018, 02:01 PM
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That's what I was thinking. The cam is a .585/.585 cam. The numbers didn't add up to me. 35kpa doesn't equal 10 psi but my gauge reads 10 psi. The fueling is fine but I may have it scaled around that issue. And if I don't hit boost this truck is really smooth. I can upload a log and the tune file when I get home if that would help.
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Old 05-16-2018, 02:07 PM
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I would look to see if you're hitting some kind of cut out or something. Posting a log/tune would help.
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Old 05-16-2018, 02:12 PM
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I attached a log and a tune. This tune RAF was off but I have since redone it. Everything else is almost identical.
Attached Files
File Type: hpl
road log 5-14-18.hpl (331.7 KB, 16 views)
File Type: hpt
newest rescale of ve OL.hpt (270.8 KB, 16 views)
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Old 05-16-2018, 03:17 PM
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For 1 your high and low octane tables don't match, 2 your shift tables for the trans are all wack. PE tps is way too high and you have PE delay on 2k as well. Spark seems to be really low in your cruising area as well.
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Old 05-16-2018, 03:25 PM
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High and low octane maps are the same now. that was the last tune I had although my new one is almost the same. And trans tables are null it has an aftermarket controller that does that.
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Old 05-16-2018, 03:26 PM
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70kPa at Idle? So youre boosting at idle?

If you meant -70kPa you have a vacuum leak.

If you truly meant 70kPa, your MAP sensor is probably fucked, or the calibration for it is fucked. If youre MAP says youre boosting 130 and your boost gauge says 10psi, youre probably dumping too much fuel, which explains the power loss and backfiring.
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Old 05-16-2018, 03:27 PM
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Yea man it's odd it says 70kpa at idle has ever since the new map sensor with vendor supplied values. Has me scratching my head. I have a good 2 bar map I may try just to see what it shows.
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Old 05-16-2018, 03:29 PM
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Originally Posted by bbowerman View Post
Yea man it's odd it says 70kpa at idle has ever since the new map sensor with vendor supplied values. Has me scratching my head. I have a good 2 bar map I may try just to see what it shows.
You probably need to change the calibration within the PCM for the 3 bar.
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Old 05-16-2018, 03:30 PM
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Originally Posted by Fuhnortoner View Post
You probably need to change the calibration within the PCM for the 3 bar.
Linear and offset? They are from the supplier.
Sorry I'm fairly new at this and learning as I go.
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Old 05-16-2018, 03:32 PM
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Originally Posted by bbowerman View Post
Linear and offset? They are from the supplier.
Sorry I'm fairly new at this and learning as I go.
I have zero experience messing with GM PCMs. Ive only messed with haltech. sorry man.
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Old 05-16-2018, 03:37 PM
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Old 05-16-2018, 03:40 PM
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He is speaking of the linear and offset value which I got from the manufacturer. But it's a good read nonetheless. I believe those are all hptuners uses, but it is very possible I'm wrong.
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Old 05-16-2018, 03:46 PM
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I did see them talking of a maf pid I could have missed. May look into that when I'm off work.

Last edited by bbowerman; 05-16-2018 at 04:10 PM.
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Old 05-16-2018, 05:03 PM
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MAF is set to fail at 0hz so it's SD tune only. I assembly this bypasses your rpm threshold for airflow cause above 2400rpms it's set to read MAF only. None of the other spark or trans comments explain why it's fine at cruise and misfires at WOT. And 70kpa is vacuum, not boost. 100kpa is normally NA WOT. You could have a bum sensor or and offset and linearity issue as stated.
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Old 05-16-2018, 05:39 PM
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Originally Posted by ddnspider View Post
MAF is set to fail at 0hz so it's SD tune only. I assembly this bypasses your rpm threshold for airflow cause above 2400rpms it's set to read MAF only. None of the other spark or trans comments explain why it's fine at cruise and misfires at WOT. And 70kpa is vacuum, not boost. 100kpa is normally NA WOT. You could have a bum sensor or and offset and linearity issue as stated.
Im confused. Do you subtract atmospheric pressure or something?

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Old 05-16-2018, 05:42 PM
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Atmospheric is also known as 15 PSI.
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Old 05-16-2018, 05:43 PM
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Originally Posted by G Atsma View Post
Atmospheric is also known as 15 PSI.
Depends on your altitude....
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Old 05-16-2018, 05:46 PM
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Sorry. I forgot to say at sea level. My bad...
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