Tune Help Needed

low_boost

New Member
Aug 13, 2023
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Hey, everyone! I'm new here, I was hoping I could get some better advice than the Facebook groups, they are useless for actual tuning info!

Anyways I purchased a tune from a tuner that won't be named, and I'm having some issues I need help uncovering.

I am getting consistent timing corrections at a specific rpm and load range. Up to -8° in some cases, this seems to have gone down to -5° since vanos changes.

I will get multiple timing corrections across cylinders at 2500 rpm, at around 40-45 load. The instances occur in sort of a bell curve between 2000-3000 rpm, with the majority at 2500.

I have adjusted timing in the area, not much luck there. I have also played with vanos by reducing overlap in the area which has seemed to help, but not fully correct the issue.

My theory initially was the exhaust gasses from overlap would induce knock in that area specifically. I used the v8 bait spreadsheet to verify overlap.

Hardware:
-new N55 plugs gapped at .018" (I tried stock down to this range with no appreciable change)
-eldor coils (swapping between quiet and loud cylinders makes no difference)
-450 lpfp
-index 12s
-new decouplers and seals.
-17ts
-170-180psi compression across the board
-walnut blasting 2k miles ago
-external high and low pcv

Any ideas?
 

Jeffman

Major
Jan 7, 2017
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Maybe an electrical issue. Check for loose or frayed wiring among the sensors. Make sure you have a healthy battery. The wires entering my TMAP once got frayed from rubbing by the wire bundles and power line laying across it which started to cause unexpected problems, and I think timing corrections, IIRC.
 
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Jeffman

Major
Jan 7, 2017
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Also what fuel is it tuned for? Check fuel quality. If using pump fuel and you have access to E85, throw in a gallon or two of E85. This usually quieted down my timing corrections when I was playing with advanced timing. Ethanol is amazing stuff for literally quieting down knock. So if ethanol helps, then reducing your timing in the indicated load range should hopefully reduce your timing corrections.
 

carabuser

Lieutenant
Oct 2, 2019
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For the corrections during cruise I would alter the exhaust VANOS in the 40-50 load area to be -90~.

Even the stock maps struggle with corrections in that area, seems to be a compromise for emissions purposes.

What do your VANOS tables currently look like?
 

low_boost

New Member
Aug 13, 2023
7
3
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Also what fuel is it tuned for? Check fuel quality. If using pump fuel and you have access to E85, throw in a gallon or two of E85. This usually quieted down my timing corrections when I was playing with advanced timing. Ethanol is amazing stuff for literally quieting down knock. So if ethanol helps, then reducing your timing in the indicated load range should hopefully reduce your timing corrections.
I tried 2 gallons of e85 with almost no change. Very surprised by this!
 

low_boost

New Member
Aug 13, 2023
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For the corrections during cruise I would alter the exhaust VANOS in the 40-50 load area to be -90~.

Even the stock maps struggle with corrections in that area, seems to be a compromise for emissions purposes.

What do your VANOS tables currently look like?
Thanks for the reply, carabuser.

I changed the exhaust vanos to around -100 in that area for a resultant LSA of 90-95.
I was hoping to reduce the EGR effect but it's possible that the increased dynamic compression offset the reduction in heat.

Intake vanos was left close to stock.
 

low_boost

New Member
Aug 13, 2023
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UPDATE:

I think my loudest cylinder was pretty much silent before swapping plugs 2 months ago, it has been progressively getting louder.

I'm going to swap plugs between 3 and 4. Maybe I got a knock off set of plugs or something.

Cylinder 1 was the loudest before, now 2 and 4 seem to be problematic. Wish me luck!
 

low_boost

New Member
Aug 13, 2023
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I was running .018" gap

It seems like the corrections have gone down slightly opening them up to .022"

Unfortunately they persist for the most part.
 

Jeffman

Major
Jan 7, 2017
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Unless you’re WOT, do you actually feel the corrections while cruising around town? It’s usually corrections during WOT pulls that we Spoolstreeters tend to worry the most about. 0-60; 60-100, etc.
 
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low_boost

New Member
Aug 13, 2023
7
3
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Unless you’re WOT, do you actually feel the corrections while cruising around town? It’s usually corrections during WOT pulls that we Spoolstreeters tend to worry the most about. 0-60; 60-100, etc.
Jeffman, thanks for the response.

The corrections are primarily in the areas I mentioned, sometimes they cary into a wot pull but eventually subside. For instance if I start the pull in the problem area I may have corrections that are induced that continue for a moment. From what I know about knock, is it can be hard to stop once it starts.

Corrections rarely pop up if I start a WOT run at 3200+ rpm.

My concern is when cruising my corrections look like pop-rocks as soon as I give it any gas.