Incorrect MPG (too high) displayed on DIC after SD re-tune

[mastersorbet]

Hello,

I recently had my car retuned to SD, and it runs very well?in fact, a lot better than it used to. The only thing I'm not excited about is getting the incorrect reading of MPGs on the DIC. I did a 300-mile round trip, and the DIC estimated a 33 mpg average, but in reality, after filling up, I calculated 21. I understand that the airflow and fuel injector flow are used to calculate that value?correct me if I'm wrong. The MAF has been deleted, so that is no longer being accounted for. I did notice that the injector flow rate versus KPA vac has lower numbers than before. That got me thinking, and I ran calculations and determined that if I take those values and multiply them by 1.39, I get the table values to the previous setting, which is closer to the Deka 60 table value. So I did, and that made the car run very lean. That got me thinking even more, so I went to the VE table and multiplied the values by the same number, and the car ran well afterward. I took it for a 15-minute drive, mostly highway, and got about 22 mpg on average. So my theory is correct. I didn't notice any difference in drivability either. Since those changes are not tested on a dyno, I decided to reload the previous values and hold on until I get a chance to talk directly to the tuner and use the dyno.

I have attached both files for reference. Car details are in my signature. I would like to get some input on it. I feel like I might be missing something. Please ignore the idle adjustments. Thank you in advance.

[SiriusC1024]

Have you thought about putting in the correct injector data, tuning with the narrowbands, re-enabling LTFT, and increasing the base spark to be what it was factory (except the high cylair areas)?

Promise the car is running like garbage compared to what it could be.

Here's Deka 60 data:
https://forum.hptuners.com/showthrea...pository/page2

You forgot P0103 to MIL on First Error.

[blindsquirrel]

Yes, it is just doing math based on what it's been told (it's not physically measuring fuel consumption) so if it has been lied to it will come up with the wrong answer. No, you can't after the fact go in and change injector data by itself without leaving behind the errors that got baked into the VE model.

[Alvin]

Hello,

I recently had my car retuned to SD, and it runs very well?in fact, a lot better than it used to. The only thing I'm not excited about is getting the incorrect reading of MPGs on the DIC. I did a 300-mile round trip, and the DIC estimated a 33 mpg average, but in reality, after filling up, I calculated 21. I understand that the airflow and fuel injector flow are used to calculate that value?correct me if I'm wrong. The MAF has been deleted, so that is no longer being accounted for. I did notice that the injector flow rate versus KPA vac has lower numbers than before. That got me thinking, and I ran calculations and determined that if I take those values and multiply them by 1.39, I get the table values to the previous setting, which is closer to the Deka 60 table value. So I did, and that made the car run very lean. That got me thinking even more, so I went to the VE table and multiplied the values by the same number, and the car ran well afterward. I took it for a 15-minute drive, mostly highway, and got about 22 mpg on average. So my theory is correct. I didn't notice any difference in drivability either. Since those changes are not tested on a dyno, I decided to reload the previous values and hold on until I get a chance to talk directly to the tuner and use the dyno.

I have attached both files for reference. Car details are in my signature. I would like to get some input on it. I feel like I might be missing something. Please ignore the idle adjustments. Thank you in advance.

Usually the MPG thing falls inline if the injector data and airflow models are correct.

It sounds like you got them back into shape with what you did.. Be aware though you are now in different spots in the timing table. Since you modified your VE table you will have the same % change in cyl airmass.

On some platforms you can change how the fuel mileage is calcuated. I don't think yours is one that you can do that to.. I could be wrong.

[mastersorbet]

Have you thought about putting in the correct injector data, tuning with the narrowbands, re-enabling LTFT, and increasing the base spark to be what it was factory (except the high cylair areas)?

Promise the car is running like garbage compared to what it could be.

Here's Deka 60 data:
https://forum.hptuners.com/showthrea...pository/page2

You forgot P0103 to MIL on First Error.

I get what your saying and I'll look at it. The one thing i'm confused about is the P0103 MIL on first error. Why would i need to switch it to that?

[SiriusC1024]

To fail the MAF in conjunction with MAF Fail Frequency High 0hz so it goes SD. Leave SES light unchecked.

[mastersorbet]

Usually the MPG thing falls inline if the injector data and airflow models are correct.

It sounds like you got them back into shape with what you did.. Be aware though you are now in different spots in the timing table. Since you modified your VE table you will have the same % change in cyl airmass.

On some platforms you can change how the fuel mileage is calcuated. I don't think yours is one that you can do that to.. I could be wrong.

I see what you're saying. It wuold change how the ignition timing would be controlled. So for now I'll leave it like my tuner set it. Thank you.

Unfortunatley i cannot find where the fuel mileage is calculated...so for now I'll just keep calculating manually.

[SiriusC1024]

Fuel mileage is calculated based on BSFC. That's calculated based on cylinder airmass and spark in relation to MBT.

All that is wrong. Like way wrong. IFR is set for 3 bar, for example. You're already 33% off just based on that. You need a new tuner.

Or we can show you how to do it right here if you'd like.

[SiriusC1024]

By the way. If you're running a higher flow pump:
https://aeromotiveinc.com/aeromotive...gulator-combo/

[mastersorbet]

Fuel mileage is calculated based on BSFC. That's calculated based on cylinder airmass and spark in relation to MBT.

All that is wrong. Like way wrong. IFR is set for 3 bar, for example. You're already 33% off just based on that. You need a new tuner.

Or we can show you how to do it right here if you'd like.

That's pretty gloomy, but I hear you loud and clear. I'm listening and ready to learn.

[edcmat-l1]

Another one that runs decent despite a whole gamut of incorrectness.

[SiriusC1024]

What's the fuel pump situation? Sure you don't want to get a new regulator first?

[mastersorbet]

What's the fuel pump situation? Sure you don't want to get a new regulator first?

I belive my 2004 does not have a regulator since the fuel system is similar to the C6, and i do not remember seeing one while i had the drivetrain off.

[SiriusC1024]

The filter is a regulator. Did you read the article?

[mastersorbet]

Another one that runs decent despite a whole gamut of incorrectness.

Yikes!!! Good to know. BTW, this is the previous tune i had before going to SD tune.2bar OS_MAF Enable_BTR Stage 1 Blower Cam_Novi1500_LT_60# Injectors Scaled 75%_v001.hpt

[mastersorbet]

The filter is a regulator. Did you read the article?

I did...and i have considered the stealth systems in the past, I am not at that level yet but will keep an eye on it. Thankfully i am mantaining a steady 58 psi fuel pressure per my pillar gauge. I definitley do not have that filter/regulator.
https://www.digitalcorvettes.com/thr...on-2004.31671/

[edcmat-l1]

Not pretty or impressive, either of them.

[mastersorbet]

Not pretty or impressive, either of them.

I think the biggest take I'm getting of this thread is where not to go. Both tunes are from different tuners. Not mentioning anyone...but sadly they have been the better two I've dealt with .

thank you for the input

[edcmat-l1]

I think the biggest take I'm getting of this thread is where not to go. Both tunes are from different tuners. Not mentioning anyone...but sadly they have been the better two I've dealt with .

thank you for the input

Unfortunately anyone with a few hundreds bucks and a laptop can be a "tooner". There are far more unqualified than qualified. It's difficult if not impossible to know sometimes. Especially if the vehicle ends up running decent.

[edcmat-l1]

Perfect example from just a few days ago.

https://forum.hptuners.com/showthrea...-changed-to-PE

You can't imagine the junk I've seen over the years.