c5 z06 question

Hey all,

So my c5z has had an issue since i purchased it a few months ago and i'm hoping someone in here can point me in the right direction. The car was built and tuned by the previous owner. Its a basic heads, cam, intake setup. The car runs and drives very well with the exception of that when i let off the gas or put it in neutral while coasting, the rpms dip past the target idle and the car almost stalls. It does catch itself before stalling, but i know that is not how it should be. It doesnt happen all the time either, but id say 80% of the time it does. For example, when i am slowing down from 45mph to turn into my driveway, it almost always dips to 350-400 rpms before catching itself and raising up to target idle of 850. I thought that maybe it was not getting enough fuel so i added a very small bit in the rpm range it occurs and it became more consistent. I don't want to pull too much fuel from the table and make the car run too lean when crusing in the low rpm/ map range. I feel that there might be a table that effects this perhaps. What tables should i be looking at to potentially correct this?

Attachment 158542

Attachment 158558

the issue occurs at the following intervals on the log:

21:02:00
21:02:24

and the car actually stalls for the 1st time at:
21:07:36

Common issue with a cam that may be difficult to get 100% in every scenario in all conditions but.... fuel, timing, idle airflow is where to start. No one will be able to offer much useful advice without the tune file and a log capturing the issue(s).

Post the .HPT and a .HPL file with the issue occurring. Has the fuel system been modified in any manner?

Quote:

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Originally Posted by abc

Post the .HPT and a .HPL file with the issue occurring. Has the fuel system been modified in any manner?

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I'll have to get a log of it doing it. All of the current ones i have are short as i was targeting other issues and havent seemed to capture it. But i'll upload the tune file for now. As for fueling, it just has ls2 injectors.

definitely makes sense. I'll post the tune file for now and upload a log later on when i can go and take one.

Another High RPM Disable - 400rpm trying to run a MAF only tune on a Gen 3. And the fact that all the P/N idle tables are populated with values on a Z06 that should have 0 values in those tables makes me think someone just copied another automatic Vette tune into this one. A lot of things in the idle tab should be put back to a stock Z06 settings. Stupid high P/N Idle airflow values that should be 0 on a Z06. Does this have 33 lb injectors? Which ones? Under speed over speed timing tables. You trying to make this thing chop them complain about an idle dip? The overall tune is bad.

Quote:

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Originally Posted by 2xLS1

Another High RPM Disable - 400rpm trying to run a MAF only tune on a Gen 3. And the fact that all the P/N idle tables are populated with values on a Z06 that should have 0 values in those tables makes me think someone just copied another automatic Vette tune into this one. A lot of things in the idle tab should be put back to a stock Z06 settings. Stupid high P/N Idle airflow values that should be 0 on a Z06. Does this have 33 lb injectors? Which ones? Under speed over speed timing tables. You trying to make this thing chop them complain about an idle dip? The overall tune is bad.

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The car was purchased this way. I didn't tune it at all. It was tuned by a reputable shop on long island that specializes in vettes supposedly. The car put down 468/434whp with what you saw in the file. The car is a frankenstein 2x heads, custom 22x/23x @ 113 with .620 lift, fast 102 manifold, nw103 throttle body, supposedly oem ls2 injectors, and arh long tubes. I don't really know much about these cars or the software honestly. Im more familiar with stand alone stuff like aem and haltech. I tried an oem zo6 file that i got off here and the car wouldnt even start. Ive been comparing the oem files VE and spark tables to the tuned one just to see how close or off they are. But i don't see how the oem z06 settings are going to work with a throttle body soo much bigger than oem. I am not trying to make anything chop, just trying to work out the bugs i was given. Figured if i could tune my 1153whp evo 8 with a sequential trans on a haltech elite 1500, hopefully i could take a stab at this. However, its very different then a haltech thats for sure. So here I am looking for some guidance

Edited my 1st post to include the log file and time stamps when it occurs. thanks for any insight and help everyone.

took the car out today for a 30 minute round trip drive and it only dipped in neutral once the entire time. anyone have any thoughts or insight?

Quote:

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Originally Posted by everkain

took the car out today for a 30 minute round trip drive and it only dipped in neutral once the entire time. anyone have any thoughts or insight?

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Quote:

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Originally Posted by 2xLS1

Another High RPM Disable - 400rpm trying to run a MAF only tune on a Gen 3. And the fact that all the P/N idle tables are populated with values on a Z06 that should have 0 values in those tables makes me think someone just copied another automatic Vette tune into this one. A lot of things in the idle tab should be put back to a stock Z06 settings. Stupid high P/N Idle airflow values that should be 0 on a Z06. Does this have 33 lb injectors? Which ones? Under speed over speed timing tables. You trying to make this thing chop them complain about an idle dip? The overall tune is bad.

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Sounds like this is a start ^^^^

Quote:

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Originally Posted by everkain

The car was purchased this way. I didn't tune it at all. It was tuned by a reputable shop on long island that specializes in vettes supposedly. The car put down 468/434whp with what you saw in the file. The car is a frankenstein 2x heads, custom 22x/23x @ 113 with .620 lift, fast 102 manifold, nw103 throttle body, supposedly oem ls2 injectors, and arh long tubes. I don't really know much about these cars or the software honestly. Im more familiar with stand alone stuff like aem and haltech. I tried an oem zo6 file that i got off here and the car wouldnt even start. Ive been comparing the oem files VE and spark tables to the tuned one just to see how close or off they are. But i don't see how the oem z06 settings are going to work with a throttle body soo much bigger than oem. I am not trying to make anything chop, just trying to work out the bugs i was given. Figured if i could tune my 1153whp evo 8 with a sequential trans on a haltech elite 1500, hopefully i could take a stab at this. However, its very different then a haltech thats for sure. So here I am looking for some guidance

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These are some of the things that need listed from the start. The biggest being different injectors and the throttle body. It's fairly easy for some of these guys to verify the injector data with a oem part number, so go ahead and post that also.

Your situation is similar to many others, you tune some of your own stuff and buddies on standalone aftermarket ECU's and eventually dive into/take a stab at the OEM stuff and realize it's not nearly as intuitive as the aftermarket. Once you learn the terminology and the general do's and dont's of the OEM's, it will get easier. In my experience, once you learn one of the basic aftermarket platforms, such as Holley, you can step into just about any Holley ECU and have a pretty good idea of what is going on. It's not quite that easy in the OEM stuff, each generation is unique and going from one OEM to another is more difficult than learning the basics of another aftermarket platform.

There are a lot of things not done well in this tune. It looks like the VE table was just smoothed a few times after just taking a wack at <1600 RPM.

Most OS's and I'll bet this one is included will have problems with more than 40 g/s in the BRAF table.

Does it have a stock throttle body on it?

Quote:

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Originally Posted by edcmat-l1

Sounds like this is a start ^^^^

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But it was tuned by a reputable shop.....

He said it has a NW103 TB on it, but iirc the ETC scalar was only slightly modified (can't remember exactly, looked last night), and also noticed the base running idle airflow table table was something like 113 or 133 lb/hr, while the desired idle airflow in the log is around 75 lb/hr. MAF and dynamic airflow was 80-90.... so something is wack there. In addition to other things mentioned (the basics like MAF and VE tables being set up properly), I would mess with the ETC scalar and base running idle tables and get things lined up.

Quote:

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Originally Posted by abc

These are some of the things that need listed from the start. The biggest being different injectors and the throttle body. It's fairly easy for some of these guys to verify the injector data with a oem part number, so go ahead and post that also.

Your situation is similar to many others, you tune some of your own stuff and buddies on standalone aftermarket ECU's and eventually dive into/take a stab at the OEM stuff and realize it's not nearly as intuitive as the aftermarket. Once you learn the terminology and the general do's and dont's of the OEM's, it will get easier. In my experience, once you learn one of the basic aftermarket platforms, such as Holley, you can step into just about any Holley ECU and have a pretty good idea of what is going on. It's not quite that easy in the OEM stuff, each generation is unique and going from one OEM to another is more difficult than learning the basics of another aftermarket platform.

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I agree with you. The terminology is a huge challenge for me right now. Also not knowing how to set up proper logging graphs in VCM scanner isnt helping. It makes it very hard for me to pinpoint exactly what is happening at those moments. Ulitmately, i might end up piggybacking a Haltech or Holley down the road just for the flex fuel simplicity vs swapping a P59 ecu in and trying to get the quirks worked out of all that.

I don't have the part number for the injectors, just have what i was told by the shop that built the car.

Quote:

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Originally Posted by Alvin

There are a lot of things not done well in this tune. It looks like the VE table was just smoothed a few times after just taking a wack at <1600 RPM.

Most OS's and I'll bet this one is included will have problems with more than 40 g/s in the BRAF table.

Does it have a stock throttle body on it?

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yeah, im sure there are. I had a feeling that it wasn't truely right. I'm sorry but im not familiar with the terminology yet. what is the BRAF table?

No, it has a Nick Williams 103mm throttle body

Quote:

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Originally Posted by aaronc7

He said it has a NW103 TB on it, but iirc the ETC scalar was only slightly modified (can't remember exactly, looked last night), and also noticed the base running idle airflow table table was something like 113 or 133 lb/hr, while the desired idle airflow in the log is around 75 lb/hr. MAF and dynamic airflow was 80-90.... so something is wack there. In addition to other things mentioned (the basics like MAF and VE tables being set up properly), I would mess with the ETC scalar and base running idle tables and get things lined up.

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thanks. i'll definitely look into those things

The new NW throttle bodies are supposed to use a stock ETC scalar.

Also, the new NW throttle bodies aren't 100% compatible with C5. You need to limit total travel to about 90% or so. There also seems to be an issue with them moving fast and setting a code for that.. NW said he was working on a back end patch for htat last we talked about this.. but that was maybe a year ago. Just keep that in mind.

ETC scalar was adjusted the wrong way for a larger throttle body. That's why the BRAF is so high. The cold temps it's insanely high. Idle airflow adapts are crazy high too.

Most of these if you get too high in total idle airflow it'll close the blade. I think it's 40 g/sec.

VE isn't right.

Dynamic is set so it's "MAF only" which totally does not work on these cars.

And like Alvin said not all of these GEN3 OS's get along well with the 102s. Some will work fine, others won't. I've had them where they'd work fine for a period of time then all of a sudden go into REP on a WOT pull.

Quote:

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Originally Posted by Alvin

The new NW throttle bodies are supposed to use a stock ETC scalar.

Also, the new NW throttle bodies aren't 100% compatible with C5. You need to limit total travel to about 90% or so. There also seems to be an issue with them moving fast and setting a code for that.. NW said he was working on a back end patch for htat last we talked about this.. but that was maybe a year ago. Just keep that in mind.

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thanks. i didn't know that they used the stock ETC scalar. Good to know. I know that sometimes the new ones don't play nice with the c5's but i had read through all the corvette forum pages that it was the nw102 that was the issue and the new 103s were much better.

really appreciate all the help.

Quote:

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Originally Posted by edcmat-l1

ETC scalar was adjusted the wrong way for a larger throttle body. That's why the BRAF is so high. The cold temps it's insanely high. Idle airflow adapts are crazy high too.

Most of these if you get too high in total idle airflow it'll close the blade. I think it's 40 g/sec.

VE isn't right.

Dynamic is set so it's "MAF only" which totally does not work on these cars.

And like Alvin said not all of these GEN3 OS's get along well with the 102s. Some will work fine, others won't. I've had them where they'd work fine for a period of time then all of a sudden go into REP on a WOT pull.

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Im sorry, but what is the BRAF? And could you explain the dynamic and MAF only? the only tab i see that has a dynamic subtab is under airflow, and then i don't see were it says MAF only. When comparing my Airflow-Dynamic tabs with an OEM 2002 z06 file, the only difference between them in all catagories is that my high rpm disable is 400 and the oem is 4000, otherwise, every single other value is the same.

To be honest, even in the other tabs, the are almost identical for values. Under the idle - airflow, everything is the same except the throttle cracker enable/ disable speeds and the adaptive idle airflow max/ min in gear values.

Dynamic disable @ 400 = 'MAF only'.

Below the Dynamic disable, it's in blended mode - a mix of both MAF and VE through some crazy equation. Above the Dynamic disable it uses MAF for steady state, and only refers back to VE for part of the also-complicated transient calculations. There is no switch to flip that is labeled 'MAF Only: Enabled/Disabled'. Your engine probably would not run at less than 400 RPM, and you sure wouldn't ever be there while driving.

BRAF is Base Running Air Flow.

Quote:

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Originally Posted by blindsquirrel

Dynamic disable @ 400 = 'MAF only'.

Below the Dynamic disable, it's in blended mode - a mix of both MAF and VE through some crazy equation. Above the Dynamic disable it uses MAF for steady state, and only refers back to VE for part of the also-complicated transient calculations. There is no switch to flip that is labeled 'MAF Only: Enabled/Disabled'. Your engine probably would not run at less than 400 RPM, and you sure wouldn't ever be there while driving.

BRAF is Base Running Air Flow.

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Thank you for the clarification.

Ok. So if i wanted to start from scratch, what is the order of operation? I am trying to take in what everyone is suggesting, but its alot of information to process. I feel like i am overcomplicating it as well and rhe best way to combat that is to do one task at a time.