Need expert help very specific question about cranking fuel and doubled AFR

its been a long time coming, but she runs and can even restart, however the restart is rough it cranks over and over when its warm, no issues cranking, but it takes almost 6 or 7seconds of cranking before it begins to fire a little, and then i give it some pedal and she fires on up like an old school muscle car.

c6 z06 twin turbo, big cam, speed density 3 bar. and methanol. she runs fine but the restart when its warmed up is terrible
cold start is fine although i feel it could be better.

here is my question
I had to double my afr in order to scale my injectors properly. I believe my car is starving for gas once its warmed up.

When you double the injectors afr, do I need to double/or cut in half the cranking fuel (FA multi stage1 vs Time)???

I have attached my current tune, and my warm start.

all help is greatly appreciated.

Attachment 124132
Attachment 124133

double the stoich and halve ifr cancels out itself in allowing the bigger scale so it dosnt really affect anything alse, make sure u have also halved ivt terms, hot starts u may have to adjust the injector tip temp offset since u have changed injectors and should not be zeroed, as a start put in factory settings and see what its like if better, startup airflow is low compared to the min airflow can be doubled as test to see if it helps

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Originally Posted by Gpargament

its been a long time coming, but she runs and can even restart, however the restart is rough it cranks over and over when its warm, no issues cranking, but it takes almost 6 or 7seconds of cranking before it begins to fire a little, and then i give it some pedal and she fires on up like an old school muscle car.

c6 z06 twin turbo, big cam, speed density 3 bar. and methanol. she runs fine but the restart when its warmed up is terrible
cold start is fine although i feel it could be better.

here is my question
I had to double my afr in order to scale my injectors properly. I believe my car is starving for gas once its warmed up.

When you double the injectors afr, do I need to double/or cut in half the cranking fuel (FA multi stage1 vs Time)???

I have attached my current tune, and my warm start.

all help is greatly appreciated.

Attachment 124132
Attachment 124133

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You shouldn't have to do that. Have you checked to make sure it's got fuel pressure on these hot restarts?

This sounds like Startup Airflow is what your looking for.

i really appreciate the advice, i will adjust the airflow and go back to stock for injector tip temp. I really appreciate the help and fast reply

Attachment 124147

give this a shot

Thank you very much I have never had anyone kind enough to make the edits in my tune so i could see what was needed. i really appreciate it!
I drove it earlier after raising startup airflow, it started really good with cold start and struggled but started better when hot. I have now added your values from the startup airflow table, your numbers were smoother than mine, a lil higher, and i trust yours more. I have also made the other two changes you showed, with relation to max map and ve vs map tables. I have also stolen the values from the c6 zr1 for injector flow rate vs iat, as my car runs a lil lean when its fully warmed up and right on when its cold and warming up.

I will post tomorrow the results of incorporating your changes, and again greatly appreciated.

if this all works and she can restart without issues, ill take her for the WOT run and post the results.

inj flow rate v iat should IMO be set to all 1.0 and only used if really needed, u will get the same affect from the inj tip offset but it wont affect the normal running area in high iat all the time, the tip temp works more on heat soak as it follows toward ect when engine is off

Very much appreciated all the help. I suffer from both running a Lil lean after warm, and trouble restarting with heat soak. I was hoping my matching of the zr1 flow rate vs iat will add that little bit of gas for cruising. But after reading your post it sounds like I need to also adjust my injector tip offset. Could you point me in the right direction for injector tip offset. I'm struggling to start when hot, should I slightly raise or lower the numbers in the injector tip offset table?

Thank you again for so much help, I still can't believe it actually runs 🤣🤣

log the injector tip temp and see where its at for normal driving around, those cells should be zero, it is a PW adder so it just adds a constant to the normal fueling PW, see what the tip temp reads when u hot start and if u need to adjust that cell higher until its good and see what its like when it idles and follows back to its normal temp it sits at, can be alot of trial and error but see how it goes

sounds like i might be playing with that for a minute. and thankyou. i have uploaded the adjustments provided, she almost cranks immediately when warm now, im pretty sure i can mess with startup af to get the rest, or possibly injector tip temp if needed. I decided to give her full pedal from 3500 to 5000 and it felt good, thank you all again for the help. Here is my small wot run as promised. I target a very low afr and low spark only 10 spark and 10.8-11.2 afr. i also spray methanol, i know there is power on the table i could go up 4 degrees in spark if not more easily, and definitely target 11.8, but i decided to target where the stock GM engineers targeted for AFR, and i fear any knock, hence the methanol and very low spark. its violently fast, the 12 inch wide tires do nothing after 4k rpms, this run has no traction from 4k-5k unfortunately.

if there are any other suggestions or recommendations for either my wot run or startup tuning please let me know and i greatly appreciate the community and help

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Ok i finally figured out why the car had such hard time starting when it was hot, and it was not my tune, it turns out it was my 1000cc snake eater injectors. I tried everything and nothing made sense, and for some reason, i had the wild idea to throw the stock injectors in the car, change the fueling maps back to match last time i used stock injectors, and boom instant beautiful start, over and over again at any temperature. Next time I will go with Injector Dynamics injectors or some other expensive injector, thank you all for the help, sorry for chasing something that was physical.

throw them in the trash

I ran into the exact same issue with SEP 1000s. I had to lower the fuel pressure to even get them to spray. But we still had wildly inconsistent afr readings at low pulse widths. We ditched the SEP injectors and went with ID1050x injectors. The owner said it already runs better and we haven?t actually tuned the truck for them yet. I don?t see how so many people run the SEP injectors and claim to have no issues. We have had nothing but issues with them.

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