Interesting observation..........
GM incorrectly reports cyl vol on 05-06' GTO, vettes, etc. Several of the forum moderators indicate they replace this with the correct value when tuning.
I reflashed the stock calibration with ONLY this change and was surprised to find this really firmed up the shifts.
Flea
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2006 GTO
Kooks LTs, NGK WB
12.96 @109.12
hmm.. this shouldn't happen really, trans should go off airflow and airflow should get calculated from VE, and the new VE doesn't need the cylinder volume to be specified. do you have any before/after logs?
cylinder volume would directly effect Shifts because it directly effects the VE table and calcs...Originally Posted by redhardsupra
its like when people put a 408ci in a 346ci stock vehicle...and they have a VE of like 130% in some spots...
then they change their cyl vol to reflect 408 and their ve return to a more normal range of values
Last edited by S2H; 03-18-2007 at 01:11 PM.
-Scott -
shouldn't have an effect, the cylinder volume is not used in the main parts of the airflow/fueling calculations.
more than likely resetting the PCM caused a few learned things to reset that made things feel better...
I count sheep in hex...
Chris read my mind... Of course he posted first.
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The car will bark the tires on the 1-2 at about 20% ETC (15 mph). I'm going to reflash and see if I still have the same thing going on. I have compared the file to the stock calibration just to make sure I didn't overlook anything. The only difference is the cyl vol. No DTC's reported either.
Very strange which is why I posted.
As an aside: what calculations is the cyl vol used for (if not the airflow/fueling)?
Flea
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2006 GTO
Kooks LTs, NGK WB
12.96 @109.12
Did another write with only the cyl volume change again. Still barks the tires on the 1-2 at about 20% ETC with very slow throttle apply. Definitely something interesting going on here (not necessarily bad).
As an aside: what calculations is the cyl vol used for (if not the airflow/fueling)?
Flea
--------------
2006 GTO
Kooks LTs, NGK WB
12.96 @109.12
usually used for misfire code and setting max limits for the airflow learn (not directly used since the VE table is absolute and not scaled by cylinder volume).
If you flash the stock file in does it do the same or only when you flash the one with the cyl vol changed.
I count sheep in hex...
I have noticed this discrepancy too in Cylinder Volume setting between the '05 and [06 & 07] vettes. So today, after stumbling on to this post last night, I changed the value to the 'correct' setting, and am noticing a difference in the feel. I'll comment more about this after things settle in.... I want to make sure this is not my imagination. I have a 2005 M6 Z51.
Why not put the stock tune back and see if the behavior changes back?
OK. I've been driving around with this change over the weekend and am convinced it is responsible for the improvement I'm experiencing. The engine feels as though it revs more effortlessly; this is true of the acceleration as well. I'm not a 1/4 mile guy but I would say the car is faster.
This is based on the stock tune (with the change). When I initially installed the change on top of a tune I had been using, it felt like I lost a little driveabilty. That's when I switch to the stock tune (with Cyl vol change). I'm going to have to tweak my tunes for this change.
To sum things up: The stock Cylinder Vol. setting being used for the 05 Vette is for the 5.7 liter motor which is "0.70819". The 06 & 07 Vettes with the 6.0 liter motor have the correct setting which is "0.75000".
Thank you to all who share their knowledge on this board.
If i change this Parameter, would it mess my tune at all ? i just noticed today my 06 GTO also have 5.7L value
I saw Chris said this value is not used for VE caluclations, but i just wonder if something else might get screwed if i change the parameter. Also, would it do anything in terms of performance ?
Changing the setting does not have much of an effect on the fuel trims that I noticed. You may have to tweak your timing though.
I have improvment in power delivery and throttle response in the low and midrange band especially. I'm also noticing the engine does not have as much of a braking effect when I let off the gas.
Try it. You will not likely hurt anything.
I wouldn't be scared to try the change if i had a bone stock car, but i have some mods already, and i've spent a crazy amount of time tuning what i have.
Makes me wonder about the pros/cons of doing this change, it doesn't affect VE in the LS2 as it was already state by Chris, but do i really want to mess with the misfire code and setting max limits for the airflow learn as also stated by Chris ?
I'd like to see some answers from the people that actually look inside the PCM, Chris or anybody else from @hptuners, maybe is nothing important, but since i'm still a newbie when it comes to tuning, i'll rather ask and make sure.
I sea Flea never posted back, and the mods didn't really say anything more on the topic.
I used the search buttom, and i couldn't find anything else regarding this change. i also checked the EFIlive forum, and only one post, same issue, they just have a different number for the Cylinder Volume parameter.
The quick check is to make the change, drive it, change it back, drive it. If you still notice the change it's real otherwise, it's PCM reset.
Always Support Our Troops!
I changed the parameter on my car yesterday, and i'm seen an increase of 1 g/cyl across the band. don't know if this was related to a change i did where i disabled my LTFT's and did some minor timing tweaking. i did 3-4 WOT runs yesterday, and drove to work today. no driveability problems so far, my fueling seems about ok, again, i'm still doing some minor tweaks to the MAF, and noticed the car running a tad rich from between today and yesterday. the only changes were in the timing. so i'm pretty sure that affected my fuel rather than cyl vol parameter. so far so good.
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