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Old 03-24-2005, 09:28 PM   #1
dt311
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Default retune when bored out?

If you have your engine rebuilt and bored out do you need to get it retuned. I have a UTEC and my car is a stage 4 setup. Or doesn't it make that much of a difference.

Thanks
Joe
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Old 03-24-2005, 09:47 PM   #2
serendipity
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Yes, retune it.
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Old 03-25-2005, 04:49 AM   #3
Bill
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I just put a 2.5L block in my car, but kept everything else pretty much stock. We are breaking it in without the the UTEC and stuff first. And we have had no trouble with the car... idles well, no check engine lights, etc. A quick road test with a GPS data logger says 215 to 220 wheel horse power. I'm sure I'm leaving alot of power un-tapped, but the stock ecu seems remarkably flexible.
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Old 03-25-2005, 09:38 AM   #4
Need4Boost
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I would retune it.
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Old 03-25-2005, 10:26 AM   #5
jimmyd
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Quote:
Originally Posted by dt311
If you have your engine rebuilt and bored out do you need to get it retuned. I have a UTEC and my car is a stage 4 setup. Or doesn't it make that much of a difference.
Depends on how big you went. If you just cleaned up the cylinders (.010 over) I would think that (unless your tuned on the raged edge) you'd be ok. With a 25% increase in displacement (like the post above) I would definetly retune!
Jimmyd
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Old 03-25-2005, 01:15 PM   #6
tmarcel
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Yeah what did you do exactly? You could get away with not touching anything if you; 1.) honed and replaced or 2.) went oversized by say .010. If you went .020 over you would probably want to retune and you would absolutely have to retune for a 2.5L over the 2L.

The above is assuming that you weren't at the edge of safety. Even going with a rebuild and resurfacing the cylinder walls and new rings could change the way your engine behaives, especially if you had a problem on your last engine at the time of tuning.

Todd
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Old 03-27-2005, 12:31 AM   #7
antimullet
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If you are increasing the displacement, with the same ecu you'd be altering the volumetric efficiency that the ECU thinks it would see right? So you should need to tune fuel and timing as a minimum. Need more air to fill the chambers, means ya need more fuel too.
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Old 03-28-2005, 11:59 AM   #8
ride5000
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Quote:
Originally Posted by antimullet
Need more air to fill the chambers, means ya need more fuel too.
that's why we have a maf sensor. maf-based systems do NOT require retunes to correct for VE changes.

the real issue is that you're using different load sites... probably ones you have never previously used, and therefore you don't really have any idea how the car is going to react.

folks, the change in charge air mass / rev for a 20 thou overbore is TINY... probably less than taking off the oem axleback.
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Old 03-28-2005, 02:28 PM   #9
tmarcel
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It's to my understanding that the MAF sensor adds or subtracts timing on the the air flow as well.
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Old 03-28-2005, 05:07 PM   #10
dt311
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thanks for all the input guys. The engine was only bored .010. So I guess from what I hear it shouldn't be that much of a difference.
Thanks
Joe
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Old 03-28-2005, 05:56 PM   #11
ride5000
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Quote:
Originally Posted by tmarcel
It's to my understanding that the MAF sensor adds or subtracts timing on the the air flow as well.
yes, on the oem ecu the load cell is calculated from charge air per cylinder. if that changes, then target afr and ignition timing MAY be changed. that's the thing about different load sites.

the utec, however, doesn't change timing on anything but MAP and RPM. so far at least...
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