extremely unlikely that it would effect the force that the starter could turn the engine over using the battery. really points to battery and possibly bad cables.

edit: im a dummy.

 

Why are you a dummy

 

I initially said alternator when I meant starter. I already edited the post though. haha I was think if you should check our alternator at all when I was writing my post and ended up typing it. but yeah, still think it's the battery or if you have an amp installed, that would be worth looking into.

 

Start troubleshooting when and why the car cranks slowly.
If the battery or the connections are bad there will be a big voltage drop while cranking and this will affect everything.
If the ecu, coils, injectors etc only sees 7-8V while cranking it's going to be very hard to start.
More heat means higher resistance, so check all battery connections and make sure they all are good.

 

i have been dealing with a similar issue. like you aem v1, battery in trunk (ran with 1gauge welding ground wire and hard to start when warm. it doesnt always do it but does it more often than not. if i let the car idle for 5 minutes before i shut it down it seems to start just fine. battery and alternator are new, voltage is fine and should have enough to start. before the alternator swap i was getting voltage drop at wide open throttle. the starter started getting sticky so i was going to swap out for the bnib starter i have sitting here. i didnt have this issue till mid summer and the whole setup (save for new battery and alt) were installed last winter. it also seems to slowly be going flat, if i measure the battery after it sits for a week it got like 12.5v and wont start the car. next idea was to try finding a potentially weak ground and check all my connections from the battery relocation. if during the no hot restart issue i jump it or use a jump box it fires right up, for me it seems to be a hot voltage issue. i'll be following along with this thread to see if any good pointers come up, i already see a few things to check for. i'll update if i find an issue

 

the alternator cutting out at wide open throttle is by design if im recalling correctly.

 

really, i think i was dropping to like low 12v at wide open throttle, id have to go back and check logs to know exactly. either way it failed at oriellys and i got a free replacement

 

yes. I have to references pulled up that show that the ECU does it intentionally. the 12 volts is your battery voltage with the car on or "under load" as most electronics guys call it. If you weren't getting flashing dash lights it was probably fine. Aftermarket alternators for our cars suck. They weren't made to be on a car that revs this high.

I'm out at lunch. I'll post the references in a bit if i remember.

edit: here's some stuff to read on it. Not explicit references but should show that the ecu does tell it to cut out at WOT. I remember reading about it when I was doing all my flashpro tuning years ago but cant find the exact reference.
https://www.hondata.com/help/smanage...parameters.htm
https://ls1tech.com/forums/general-m...-drop-wot.html

 

alternator rectifier is most likely shot.... replace it.

 

Don’t rule out serpentine belt-slip at higher RPM causing voltage drop.

Also, slow crank suggests resistance, bad ground, tired battery and so much more. This isn’t easy to pinpoint or help you with.

From the tune standpoint, I know you’re adamant about it not being the cause however at extreme heat soak you might need additional fuel, a good amount. Ask your tuner to bump comp tables at heat soak temps and see if that fixes the issue. Also, it’s not pulling crazy timing due to ignition comp tables is it? Check ign trim tables at heat soak state crank (when it doesn’t start).