Different Compression with Eco Reflash - Tuning Forum

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Different Compression with Eco Reflash
Sunday, October 29, 2006 8:00 PM
I was just wondering something...

Could the Ecotec Reflash account for pistons having different compressions?

Meaning, could I swap from the 10:1 compression to a 8.9:1 or 11:1 compression pistons without any problems?




Re: Different Compression with Eco Reflash
Monday, October 30, 2006 6:05 AM
The ECU can't dynamically adjust for piston compression, if you go higher you'll need to run higher octane to control knock, if you go lower then you should be fine.





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Re: Different Compression with Eco Reflash
Monday, October 30, 2006 8:20 AM
Right now, I run 93 octane anyway because of the supercharger.

So you're saying that upping the compression and using 93 octane I would be fine.

What about dropping the compression and instead of using 93 octane, using 89? Not saying I want to, just wondering.

How would a different bore affect the ecu?



Re: Different Compression with Eco Reflash
Monday, October 30, 2006 9:04 AM
The ECU cannot compesate for any internal chages in the motor other than airflow.



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Re: Different Compression with Eco Reflash
Wednesday, November 01, 2006 8:49 AM
well technicly that is partially true , the pcm doesnt know what the compression is


but it does know " knock " , and higher compression will be more prone to knocking , then lower compression , and the pcm will adjust for it

but with the s/c you want to keep the off boost tq , and that requires a little compression , since you need it to help with the load from the s/c

where a turbo doesnt eat any power , the loss of tq from the lower compression wont hurt as bad on off boost driving

all of this is provided you dont get any knock


and from what ive talked with others about when gm says to use premimum fuel , 91 isnt it , and 93 or 94 are usually what the car needs









Re: Different Compression with Eco Reflash
Wednesday, November 01, 2006 9:25 AM
^ The knock sensor is a symptom adjustment, not a pre-adjustment type thing. The ECU compensates for knock AFTER it happens, that means that if you get a couple good knocks at higher RPM, the ECU won't adjust for it until after the knock occurs, at that point, it may be too late. Never EVER rely on the ECU's knock-learn to save your motor, or to adjust for lack-of-tuning.





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Re: Different Compression with Eco Reflash
Wednesday, November 01, 2006 10:21 PM
thank you for adding that

i was at work , so i didnt get to type out everything i wanteded to say








Re: Different Compression with Eco Reflash
Wednesday, November 01, 2006 11:16 PM
Shifted wrote:^ The knock sensor is a symptom adjustment, not a pre-adjustment type thing. The ECU compensates for knock AFTER it happens, that means that if you get a couple good knocks at higher RPM, the ECU won't adjust for it until after the knock occurs, at that point, it may be too late. Never EVER rely on the ECU's knock-learn to save your motor, or to adjust for lack-of-tuning.


Can the ecu remember what conditions cause knock? When they begin to occur can it automatically pull timing before it happens?



Re: Different Compression with Eco Reflash
Thursday, November 02, 2006 6:51 AM
No it doesn't





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Re: Different Compression with Eco Reflash
Thursday, November 02, 2006 3:01 PM
Admiral Jedi wrote:
Can the ecu remember what conditions cause knock? When they begin to occur can it automatically pull timing before it happens?


the ecu is reactive, so no





Re: Different Compression with Eco Reflash
Wednesday, November 08, 2006 4:21 PM
At least the ECU used in the cavvy is reactive only.


--------------------------------------------------
'96 Cavalier Good ol' Pushrod 2.2
-24X,000 miles on factory build
-Some oil loss between changes, me thinks it be rings.

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