2011 CTS-V Hot Start Issues

[Colder2012]

Hi fellas, first off I want to say thank you to all the contributors to this forum, you guys have taught me so much over the last 4-5 years.

I have a customer that has a 2011 CTS-V and we are trying to figure out some intermittent hot start issues. I would appreciate any input as I feel like I have exhausted every avenue that my knowledge will allow. The car was built and tuned by a very reputable shop (I know this means absolutely nothing), but figured it may be valuable info to some. The car will crank and idle fine every time when cold, as the car idles for 15-20 minutes, the engine gets heat soaked and will not start.

Mod List:

- Ported Blower
- Ported Snout
- Flex Fuel Kit
- Upper Pulley
- 127lb 1200cc Fuel Injector Connection Injectors

The car has 100% stock returnless fuel system, aside from the injectors. The issues that we are experiencing seem to be very IAT dependent and seem to be more prominent on gasoline over E-85. I have noticed that there are a few IAT injector tables, but I'm trying to avoid messing with any injector tables that could possibly throw the whole tune off as the customer just needs the car fixed to get it sold - at least until I can rule out all possible mechanical issues. Customer says that he did not have this issue last summer, so this leads me to believe that there is something going on with the hardware.

I found a vacuum leak at the injector o-rings, so I replaced all of them and the leak has been mitigated. Car is still having hot start issues, but fuel trims are much better. Fuel pressure is a consistent 58psi at idle.

Are these injectors too large for the returnless fuel system? My theory is that the extremely hot fuel rail is building up too much pressure in the rail and the injectors will not open with that much head pressure. The fuel pressure will rise to around 70 with the engine off key on and seems to be boiling within the rail when I relieve pressure. I personally have used 80lb injectors on other CTSV's and they had plenty of fuel on e85 with similar modifications.

Any input would be greatly appreciated.

Tune file Harry Gunner 11 CTSV Base.hpt

[cadillactech]

Can you monitor fuel pressure with a gauge during hot soak and during the crank no start? Just to see what is happening in the rail while the no start happens.

Can you grab a data log while it happens?

Vapor lock could be an issue for sure.

[Colder2012]

I believe i got the problem figured out. I added fuel to the cranking fueling tables and the issue seems to be gone

[C6ZRJUAN]

I had a similar issue on my ZR1. The fuel pressure would climb up to almost 100 psi after I shut off the car. It wouldn't start unless I bled off pressure from the fuel rail, then it would start right up. Fuel injector Connection ended up sending me different fuel injectors, the problem never happened again.

[Speedmaster747]

fuel vapor lock
I just did a test on a CTSV that had 102psi on the rail with the car off, and full running temps 210 F.
Pouredthe contents of a cold water bottler on the fuel rails, and saw the pressure drop all the way down to 62 psi
car starts right up.
It wont start on 100+psi fuel pressure.

[sgod1100]

One that stuck out to me that isn't related to your problem is your injector offset vs. injector temp table has been zeroed out which isn't good. This table can be found in Fuel>General> offset vs. inj temp. If you are heat soaked you run the risk of going lean with this table zeroed. Also, in my experience talking with some smart guys on here, you flex fuel spark should be REMOVING a few degrees of timing at light load. It looks like you are just adding in timing from 3k on up in the high cyl. airmass areas

[JayRolla]

One that stuck out to me that isn't related to your problem is your injector offset vs. injector temp table has been zeroed out which isn't good. This table can be found in Fuel>General> offset vs. inj temp. If you are heat soaked you run the risk of going lean with this table zeroed. Also, in my experience talking with some smart guys on here, you flex fuel spark should be REMOVING a few degrees of timing at light load. It looks like you are just adding in timing from 3k on up in the high cyl. airmass areas

I always keep that table zeroed out because of the rich after flash issue since it takes time to correct. Never ran into a lean condition so far.

[Alvin]

Injector temp table can be zeroed out.. Most trucks are zeroed from factory.

[sgod1100]

I always keep that table zeroed out because of the rich after flash issue since it takes time to correct. Never ran into a lean condition so far.

There is a long post on it on here talking about how on our cars it shouldn't be zeroed out. Rather have it turned down if you have larger injectors. I think Ghuggins can shed some light on that.

[sgod1100]

https://forum.hptuners.com/showthrea...ip-Temperature

[sgod1100]

Injector temp table can be zeroed out.. Most trucks are zeroed from factory.

Yeah, but are they compensating for heat soak somewhere else in the tune?

[Alvin]

There is a long post on it on here talking about how on our cars it shouldn't be zeroed out. Rather have it turned down if you have larger injectors. I think Ghuggins can shed some light on that.

There are a lot of people that disagree with that.

[GHuggins]

Yes and there are a lot of people who complain about hot restarts being lean that have it zeroed out such as after filling up at the pumps. You want fueling right at all temps and all times it should be dialed in

[sgod1100]

There are a lot of people that disagree with that.

well I could see it with my ID1050s...SUPER rich when heat soaked with the stock ITT table. Lean when heat soaked with the table zeroed out...and who are these "people"? I'm genuinely asking and not being a smart ass

[GHuggins]

Yeah especially since SO MANY people chimed in on how it was correcting issues they had years ago.

Scott was the original person who discovered this table when we were digging and having hpt add tables in years ago for everyone. His formula for anyone who wants to dial this table in correctly is posted in this original thread on the second post in his post (jslic) -

https://forum.hptuners.com/showthrea...p+temp+formula

[Alvin]

Respectfully, I'm not going to argue with you Ghugg but there is another big tuner on the first page of that thread disagreeing with you.

Maybe there is something off with how you tune vs how I tune where I don't get these lean or rich hot starts. Don't you think with the volume I do if I had a issue I would be looking for it? I mean rationally.. do you really think I have a issue like that? That I'm just letting cars go with a lean restart or whatever it is you think this fixes?

And what about trucks.. Practically NO trucks use this table. I've already proved to you that isn't a old/new calibration thing.. up to 2013 they are like this. They are zeroed from the factory.

Injector offsets are not tuneable items. You get offset data from the manufacturer

[Alvin]

well I could see it with my ID1050s...SUPER rich when heat soaked with the stock ITT table. Lean when heat soaked with the table zeroed out...and who are these "people"? I'm genuinely asking and not being a smart ass

As a professional there are is a cohort of others that I talk to.

I think generally there is a misconception on target OL fueling, after start, etc. And what should the wide band read like in those conditions.. A simple example.. the OL tables can target something as rich as say 10:1 while cold. The wideband should NOT match that. Only vaporized fuel is burned.. cold engines do not evaporate the fuel like a hot engine does so the engine is purposely rich so that what did evaporate did burn and make it out the tail pipe near stoich.


Also just generally.. people seem to go after all sorts of odd tables when in reality when the fundamentals of the tune is setup properly things start falling inline. The biggest culprit is idle tuning stuff. So many people just go ham on throttle follower, cracker, airflow integral and proportional tables... when all or most of it can be avoided if the airflow models are spot on first.

[sgod1100]

As a professional there are is a cohort of others that I talk to.

I think generally there is a misconception on target OL fueling, after start, etc. And what should the wide band read like in those conditions.. A simple example.. the OL tables can target something as rich as say 10:1 while cold. The wideband should NOT match that. Only vaporized fuel is burned.. cold engines do not evaporate the fuel like a hot engine does so the engine is purposely rich so that what did evaporate did burn and make it out the tail pipe near stoich.


Also just generally.. people seem to go after all sorts of odd tables when in reality when the fundamentals of the tune is setup properly things start falling inline. The biggest culprit is idle tuning stuff. So many people just go ham on throttle follower, cracker, airflow integral and proportional tables... when all or most of it can be avoided if the airflow models are spot on first.

So why is that table populated in a stock ctsv tune? Also, when you change injectors (to larger) there's no mention of zeroing that table out when putting in the injector data? Again, serious questions because I honestly don't know

[Alvin]

Why is it not in trucks? Are they doomed to have lean restarts?

Has ID, FIC, deatschwerks, etc ever offered injector tip temp offset data?

[sgod1100]

Why is it not in trucks? Are they doomed to have lean restarts?

Has ID, FIC, deatschwerks, etc ever offered injector tip temp offset data?

I have no clue why it's not in trucks....No they haven't, but they also don't say to zero that table out either