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Author Topic: Tach RPM different from datalog RPM  (Read 5262 times)
RunninHorse
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« on: January 21, 2018, 12:06:34 am »

Posted this on EFIDynoTuning, but didn't get any replies.  Tuning is at a stand still until I can get this resolved.  Any help is appreciated.

I went for a drive to take some logs for dialing in FN035. The RPM (NE) in the log appears to be lower than actual RPM. I let off ~6500 and the highest WOT RPM my log shows is ~4900. My shift light did come on and it's probably set around 6500. The highest RPM in the log is 5100.

I took two logs and the RPM in both seems off.

What could cause the RPM to be understated and what impact would that have on the engine?
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I'm Rob.  Working on my '93 Reef Blue coupe.  Stock internal 302, 80 MAF, 75 TB, Victor 5.0, High Ports, 30# inj., B303, 1.6s, Tremec TKO 3550, Quicktime bell, Fidanza Al flywheel, stage 3 ceramic clutch, & 4.10s.  12.68 @ 111.69
'66 F100 shortbed, 352ci, 3 on the tree - on hold
'65 Coupe rolling chassis - on hold
Parts I'm selling: 
Hardened Push Rods - Trick Flow 6.2" .080 - $60
Misc. Fox Body Interior Pieces
347HO
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« Reply #1 on: January 21, 2018, 04:05:41 pm »

Is there a 4 - 6 - 8 cyl setting that may need review?
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... it was REALLY revving at like 4K...
If I saw that thing in my rear view Im pulling over to let you by, I be scared of that thing Huh? i dont know wich car is uglier ur or mine?
Javier
Ugly?  Easy now -- that's my baby and it's got lots of unique character!  When I drop that built 445" stroker in it you won't have any time to "pull over to let me pass" because I'll have already blown past you when you figure out what the hell was that loud noise behind you . . .  
RunninHorse
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« Reply #2 on: January 21, 2018, 11:28:22 pm »

Is there a 4 - 6 - 8 cyl setting that may need review?

Not exactly, but relevant settings have been reviewed.  If the EEC thought I had a 4/6 cylinder I’m sure I would have serious issues. 

Car is running great with the A9L2, but I need to dial in load before I can dial in fuel.  Shouldn’t really drive it until I can do all that, so this RPM mismatch sucks.
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I'm Rob.  Working on my '93 Reef Blue coupe.  Stock internal 302, 80 MAF, 75 TB, Victor 5.0, High Ports, 30# inj., B303, 1.6s, Tremec TKO 3550, Quicktime bell, Fidanza Al flywheel, stage 3 ceramic clutch, & 4.10s.  12.68 @ 111.69
'66 F100 shortbed, 352ci, 3 on the tree - on hold
'65 Coupe rolling chassis - on hold
Parts I'm selling: 
Hardened Push Rods - Trick Flow 6.2" .080 - $60
Misc. Fox Body Interior Pieces
347HO
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« Reply #3 on: January 22, 2018, 01:09:16 pm »

👆
Why you need that msd crank trigger....
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... it was REALLY revving at like 4K...
If I saw that thing in my rear view Im pulling over to let you by, I be scared of that thing Huh? i dont know wich car is uglier ur or mine?
Javier
Ugly?  Easy now -- that's my baby and it's got lots of unique character!  When I drop that built 445" stroker in it you won't have any time to "pull over to let me pass" because I'll have already blown past you when you figure out what the hell was that loud noise behind you . . .  
rob342
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« Reply #4 on: January 22, 2018, 03:52:38 pm »

Did you ask on eectuning yet?

This is from a thread where someone that was reading 16000 rpm on their datalog. I don't understand it but it makes me wonder if someone smart like decipha would just say "set this to xx"


* Screenshot_20180122-144503.png (259.57 KB, 1920x1080 - viewed 59 times.)
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have tw170's, systemax II, 75mm accufab, anderson n41, t5z, ford racing 23lb billet flywheel, and a quarterhorse sitting here. cam may change
mighty mouse
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« Reply #5 on: January 22, 2018, 05:53:58 pm »

How do you know which one is (mostly) correct?
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85_GT
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« Reply #6 on: January 22, 2018, 06:32:03 pm »

but I need to dial in load before I can dial in fuel.  Shouldn’t really drive it until I can do all that, so this RPM mismatch sucks.
You don't dial in load.  Load is what it is, if you didn't jack up the MAF curve too much.  FN035 is one of the last things you 'tweak'.  It's just used to 'determine how much pedal gets you to open loop'

As far as RPM, are you using BE or TunerPro?  Decipha's latest bin works best with TunerPro.  Are you looking at the right value.  RPM has always been N, and N byte for Tweecer users.  It would be odd for him to rename a strategy PID.
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RunninHorse
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« Reply #7 on: January 22, 2018, 10:58:27 pm »

👆
Why you need that msd crank trigger....
That's on my shopping list, but I don't think it would resolve this.  Not ready to change more stuff until I get this resolved.

Did you ask on eectuning yet?
This is from a thread where someone that was reading 16000 rpm on their datalog. I don't understand it but it makes me wonder if someone smart like decipha would just say "set this to xx"
Haven’t asked on EECTuning, but I did get a reply from Decipha.  Going to try what he suggests and see where that gets me.  Thanks for looking into it.

How do you know which one is (mostly) correct?
My bet would be that the two tachs are accurate, and the log is not.  When the tachs read 6500 it sure sounds like 6500, not less than 5200 like the log shows.

but I need to dial in load before I can dial in fuel.  Shouldn’t really drive it until I can do all that, so this RPM mismatch sucks.
You don't dial in load.  Load is what it is, if you didn't jack up the MAF curve too much.  FN035 is one of the last things you 'tweak'.  It's just used to 'determine how much pedal gets you to open loop'

As far as RPM, are you using BE or TunerPro?  Decipha's latest bin works best with TunerPro.  Are you looking at the right value.  RPM has always been N, and N byte for Tweecer users.  It would be odd for him to rename a strategy PID.
Dial in load was probably the wrong choice of phrase.  I mean tweak it like you said.  It’s the last step to set up the A9L2 base tune.
I’m using TunerPro and I think I have the right value.  I didn’t see any others that look like engine RPM.  I’ve asked Decipha to be sure.  We’ll see.  Thanks.
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I'm Rob.  Working on my '93 Reef Blue coupe.  Stock internal 302, 80 MAF, 75 TB, Victor 5.0, High Ports, 30# inj., B303, 1.6s, Tremec TKO 3550, Quicktime bell, Fidanza Al flywheel, stage 3 ceramic clutch, & 4.10s.  12.68 @ 111.69
'66 F100 shortbed, 352ci, 3 on the tree - on hold
'65 Coupe rolling chassis - on hold
Parts I'm selling: 
Hardened Push Rods - Trick Flow 6.2" .080 - $60
Misc. Fox Body Interior Pieces
RunninHorse
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« Reply #8 on: February 10, 2018, 07:22:26 pm »

Decipha modified the GUFX strategy and the new version logs RPM correctly.  I've adjusted FN035 and that completes the first steps for the A9L2 tune.

I've only driven the car a few times (haven't adjusted fuel yet) and it's running great!  I'm looking forward to dialing in fuel and getting back to the track.   Grin
Logged

I'm Rob.  Working on my '93 Reef Blue coupe.  Stock internal 302, 80 MAF, 75 TB, Victor 5.0, High Ports, 30# inj., B303, 1.6s, Tremec TKO 3550, Quicktime bell, Fidanza Al flywheel, stage 3 ceramic clutch, & 4.10s.  12.68 @ 111.69
'66 F100 shortbed, 352ci, 3 on the tree - on hold
'65 Coupe rolling chassis - on hold
Parts I'm selling: 
Hardened Push Rods - Trick Flow 6.2" .080 - $60
Misc. Fox Body Interior Pieces
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