PE - Power enrichment table

[uk_hsv]

Hi
This is my first tuning post here so please understand if I state the obvious some times

I drive a HSV Clubsport R8 (VT11) and have just logged my first Dyno run (see below)

My first action after the run was to turn off "cat protection" and to change my PE Table as the car is running very rich......

My question is the PE table says it is calculated using stoich AFR Divided by the table figure, so at 2500rpm it should be 14.62857/1.151 = 12.7094 BUT the Wideband reads A/F @ 2500rpm of 11.39........

So what other tables affect the PE to change this figure.

[MNR-0]

The O2s are usually off by a fair bit - its normal. On mine its off by 1.2 AFR from the PE values. That said, if I set my PE to be 13.5 its actually 12.3. I can work with that...

[MNR-0]

You are running rich as with that AFR plot. Its also all over the place. I woudl suggest getting your fuel trims stable at -4% then doing another run. My AFR plot is ruler flat from 4000RPM onwards.

[uk_hsv]

Ah Fuel Trims...........I am just ttying to understand them now.

Here are is a short log that I am using to try and get a handle on Trims......

Any pointers??

[uk_hsv]

I have scaled the PE Table (see below) it was between 1 and 2.39 out on the A/F......

I have logged a run on the road and it shows some Knock at 4200rpm upto 5500.......

My action is to add more fuel to cool the knock! is that the correct way to go?

As for Fuel Trims it is not looking to easy!! is there a explanation of what tables effect what other tables.

Thanks in advance for any help................

[Dirk_Diggler]

use the vet able to get the LTFT histogram Green or close to 0 as possible. Once the ve table is dialed in your commanded pe AFR will match the WB AFR. Looks like you got the pimp version of the Suite

[jimmyblue]

Ideal situation is that the "model" of the engine's air
and fuel delivery is accurate, and you get an actual
AFR that matches your commanded AFR. Like a 1.15
value in the PE table should give you 12.8:1 on the
wideband.

Over-rich can come from an error in the air flow (MAF,
at WOT, usually) or the fuel flow tables; it can also come
from fuel trims. Because the MAF accuracy changes over
the airflow range, a positive trim applied due to being
lean down low, may be inappropriate up top. Thus the
advice to get small negative trims, preventing any WOT
up-trimming.

If you have stock injectors and a stock injector table
then you should leave that alone. However people get
advised sometimes, to mess around the IFR table in
pursuit of some effect or other. In my opinion this is a
bad move except when you know there is a fuel model
discrepancy (like from injector swap, different regulator
or pump, etc. stepped you off from factory).

Your AFR is not only low, it's "notchy" and declining.
Indicating you want a fading-rate PE/RPM table with
less enrichment up top. Don't know why the AFR
reading is so lumpy, other than resolution limits on
the sensor / calculation.

Before you try too hard there, though, be sure your
Open Loop Fuel/Air vs ECT vs MAP table has values in
the proper-ECT columns, that are less than what you
have in the PE table. Otherwise you can adjust PE
downward all you like, to no effect.

Anyway, first consider the air and fuel metering / model
discrepancies that might be present in the hardware.
True those up and you should get the AFR you command
(bearing in mind the multiple "bosses" there can be).

[uk_hsv]

Thanks for the info (some of it i don't understand yet!!) I will post my progress and please feel free comment.....

[uk_hsv]

I have looked at the "Open Loop Fuel/Air vs ECT vs MAP table" and the range I am operating in shows 1.00 in all the ECT columns.... which I understand means no addition is made... so I have produced a PE table which is graded up at the higher RPM for a short term fix...

[uk_hsv]

can some one give me some pointers on how to achive this advice.......

Over-rich can come from an error in the air flow (MAF,
at WOT, usually) or the fuel flow tables; it can also come
from fuel trims. Because the MAF accuracy changes over
the airflow range, a positive trim applied due to being
lean down low, may be inappropriate up top. Thus the
advice to get small negative trims, preventing any WOT
up-trimming.

My main problem is finding out what action is required to change a table ie. do I add divide or multiply figures.

Any help is gratefully receved.......

[uk_hsv]

Sorry more questions.........

I have a log file showing various cells with 5 and more when viewed as an average.........(see above)

now if I find the same cell in the VE table it shows 93 am I correct in thinking that I need to replace the 93 with 84 so I get a avarege of -4......

Is this the correct way to "trim the LTFT"????

I also assume that you keep doing logs until you get a spread of -4 across the board....

OR have I got it all wrong..................

[marc_w]

If you have stock injectors and a stock injector table
then you should leave that alone. However people get
advised sometimes, to mess around the IFR table in
pursuit of some effect or other. In my opinion this is a
bad move except when you know there is a fuel model
discrepancy (like from injector swap, different regulator
or pump, etc. stepped you off from factory).

I hate being a pain in the neck with this IFR/VE stuff, but there is no other way to move LTFT's in my vehicle than to modify the IFR table.

I'm quoting screamn03 from another thread here:

If you make changes to the VE table with the MAF still plugged in it won't make a difference in the average LTFTs but it will affect idle, low speed, and throttle response to a certain degree.

It seems like a catch-22......

[Dirk_Diggler]

Sorry more questions.........

I have a log file showing various cells with 5 and more when viewed as an average.........(see above)

now if I find the same cell in the VE table it shows 93 am I correct in thinking that I need to replace the 93 with 84 so I get a avarege of -4......

Is this the correct way to "trim the LTFT"????

I also assume that you keep doing logs until you get a spread of -4 across the board....

OR have I got it all wrong..................

The trims is the percentage you are off. If you see +5 then you need to move the ve table at that location by 1.05

93*1.05=97.65

or if it were -5 and you wanted to lean it out

93*.95=88.XX

[uk_hsv]

Thanks for that...........

Just to make sure I am doing this right, this is the process I am using shown below.....

Origional VE shows 87 at 100k/Pa-4000rpm and the log shows an average of -7 (red box) so the change should be

87 x .93 = 80.91

[distortion]

I am new, and this is actually my first time reading this forum. I also have no experience in tuning.

However, it appears to me as though that value is positive? And the above mentioned post said you would multiply the table to add that percentage. Therefor you would want to add 7% onto the existing table. Therefor you would multiply by 1.07. Which would be 87 x 1.07 = 93.09 .. This would mean that the it would no longer be 7% positive. That it should be "0". Although, I have a hard time believing that it would be perfect.. I guess that would probably put you at least closer to where you want to be.

Good Luck,
Josh

[Keith@HPTuners]

Red boxes are + numbers, not - so you need to go up in VE not down.

The #'s are red because the PCM is adding fuel to be happy. If you go lower in the VE you will be removing fuel and thus puting the AFR even further away from the PCM's happy place.

Do not modify the WOT VE cells. Those are fixed at + #'s because your part throttle LT's are +. You need to adjust your part throttle LT's closer to 0 and low - #'s and then your WOT LT's will also be inline.

[uk_hsv]

Cool ...I am starting to get the idea.....thanks

So my action for this sample cell should be...

87 x 1.07 = 93.09 (or 87 x 1.10 = 95.70 if I am trying to get negitive numbers across the table)

"Keith" you say not to change the WOT VE cells, which cells are they?

[uk_hsv]

Now I am on a roll with questions...here is another.

If in the future I move to a MAF Less set up am I right in thinking that it is the secondary VE table that I make the changes to?

[Dirk_Diggler]

Only if you have a secondary table....

There is really no real way to tell you what WOT cells are. This is denoted by FTC 22 adn certain conditions have to be met in order to hit WOT. Best thing to do is try to log best you can without having the car go into PE or WOT. This will better help get you closer but needs to be verified via a WB (Wide band)

[uk_hsv]

Thanks "Dirk Diggler" for you help

Looking at my data log of the Dyno session WOT seems to be above .60 gcyl @ fuel trim cell 22 so I will avoid making changes in and above this area.

here is my Dyno log http://www.hsvdriversclub.co.uk/tuning/v650epn.xls

To continue on this Mafless topic I have just been out with a guy with a 500hp+ HSV (Supercharged) and his LTFT show -12 to -14 accross the table............that sounds very rich??