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Discussion Starter #1
Just wondering which sensor dectects the octane that I put in my car... and do they go bad or report incorrectly?
 

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The knock sensor along with the ECU and I haven't seen one go bad in all my years (the knock sensor that is).
 

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Discussion Starter #3 (Edited)
Thanks yet again Joe. Only reason I am asking is because with all the boost issues that are still unresolved, my performance (8-9psi ftl) is still the same regardless of whether I put in 87, 89, 91, or 93, and 100 oct. Today with 15 miles left in the tank I decided to put in 4 gallons of E85. Well, after driving it for about 10 miles I floored it. I did not get a CEL.. Which I know usually happens with E85. I hit 12 psi 1st and 2nd gear. Did not get to try 3rd since I don't have the roads here to do it. All this time I could not get it above 9 psi and now it hit 12.. and it stayed... Car felt it had crazy top end... Usually it feels like I hit a wall around 5000 rpm and feels like its out of breath the rest of the way. So that's why I was asking. Trying to figure out what the heck is going on and maybe figure out if this is a clue I can use to fix the issue.
 

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Hmmm odd, did you reset the ECU after switching octanes? A fresh ECU reset along with 100octane juice really makes a huge difference probably similar to E85 but a ton safer.
 

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Discussion Starter #5
Hmmm odd, did you reset the ECU after switching octanes? A fresh ECU reset along with 100octane juice really makes a huge difference probably similar to E85 but a ton safer.
I did not do an ecu reset when I tried 100oct. But when I did have 100ct (5 gallons only in the tank with 25 miles worth of 93), the car did not pull hard low or top end and I would not pass 8 to 9 psi in 1st through 4th.. Regardless of the temps outside.
 

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Nothing "senses" octane. Higher octane fuel reduces the chance of spark knock. If there's less knock, the computer will be generous and allow a little more timing and perhaps boost. Your findings with E85 make sense. If you put straight 93 in, the octane will be lower than what it was with the E85 mix, and the computer will hear the knock associated with that and pull timing/boost accordingly.
 

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The ECU can calculated a projected octane rating based on timing strategy and knock ceiling detection, in older VADIS version it could actually show you the projected octane that was in the fuel at the moment.

If you're seeing consistently low boost perhaps your boost pressure sensor is drifting or failing... somewhat common on your model.
 

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Discussion Starter #9
Can you give a brief description of what youve tried as fixes?
oh boy.. compression test, new spark plugs, maf sensor, fmic kit, new fuel pressure sensor, HD TCV, snabb intake (incase the old tubing was cracked), new vac hoses... But at this point I am going to do a lot of data logging in the next couple of weeks and post those as well as put my old tcv back on. I don't want to waste any more of anyones time before I do that...
 

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Discussion Starter #10
The ECU can calculated a projected octane rating based on timing strategy and knock ceiling detection, in older VADIS version it could actually show you the projected octane that was in the fuel at the moment.

If you're seeing consistently low boost perhaps your boost pressure sensor is drifting or failing... somewhat common on your model.
hmm.. i may have to try vadis as well.
 

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I know there was a mystery about those HD TCVs (from IPD)...I remember when I installed mine a few years ago I had an issue with boost. It developed after a few miles...wouldn't hold any boost. Put my old TCV back in without an ECU reset and car was all good. I thought I read a few people have issues with them...not sure tho.

yeah maybe the boost pres sensor?
 

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Discussion Starter #12
Yeah I will be putting the stock one back on, and just in case the stock is bad too I will order the phuzzy. I also plan on rechecking all my tubing. BPS is always a possibility as well.. But ill get into all this after some data logging.. :)
 

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Replaced my IPD TCV with the stock one last week. Much smoother response.
 
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