[cjperformance]

No leaks. Still going to be paranoid for a while. Put a couple gallons in it in the garage while checking for leaks. Couple of short drives... check it, put in some more blah blah. For now at least it isn't leaking with a half tank. Really not impressed with the tap the tank thing though. With the way it sits, all I need is to run over the wrong thing on the highway and it would prob rip it out.

Just figured I'd throw out the reality of things in case someone else is thinking of going this way. If I had to do it over, and wasn't planning on needing the addl fuel pressure capacity overhead... I prob would have dropped the tank and put an in-tank one in.

Anyhow... the good news. It's mostly working and it's not leaking.

I had my battery disconnected for around 48 hours or so. I took the following log today, but didn't notice until I got back that my wideband went AWOL. The gauge in the car was still working, so didn't dawn on me to check it was showing up in HPTuners. Hopefully I just need to rediscover it and add it back in. No time to addl run today.

This was a mostly expected issue with fuel pressure, where the two fuel pumps are duking it out over what each thinks is the right fuel pressure. What I found unusual is that while accelerating in 2rd gear, the low side fuel would go up to 70-80 psi, then around 5800 RPM it would crash really low. Lower than I've ever seen it without the addl pump... as low as 20 PSI. But after the 2-3 shift, in 3rd, it would come up and stay up until the 3-4 shift.

I haven't had much time to read up on this yet, but I imagine I need to tell the FSCM not to back off the in-tank pump to try to account for the aux pump.

[cjperformance]

Another showing a dip in 2nd gear, but not a "crash" in this case, FP was staying upwards of 50 PSI, but dipped down from the 80 psi it was at seconds earlier. Once again, only in 2nd gear. In 3rd, it maintained more than 70 psi the whole time.

Reading this link over and over trying to correlate what it talks about with my own system. Seems like the table ids are not correct, but some of the names match up: https://dsxtuning.com/blogs/dsx-tech

[Trochoidal]

Do you think your fuel pressure dropping had anything to do with a low fuel level? Maybe your 2nd gear acceleration and low fuel are related.

[cjperformance]

Originally Posted by Trochoidal

Do you think your fuel pressure dropping had anything to do with a low fuel level? Maybe your 2nd gear acceleration and low fuel are related.

No, for that run i had 1/2 tank. Im sure it has to do with the tune. The low side fuel press is prob exceecing some predefined value and causing the in tank pump to lower or cut output. The dsx link i posted earlier speaks to a lot of this, just need to filter through the info better when i have time. Or someone whos done this before can provide some insight.

[wnta1ss]

FSCM 6994 is there if you can read and license your FSCM. Below is a screenshot of an FSCM 'read' on my 2017 SS. My understanding is that we cannot actually read the module, and what we're actually getting is a generic from HPT. Screenshot of FSCM 6994 below.

[cjperformance]

Originally Posted by wnta1ss

FSCM 6994 is there if you can read and license your FSCM. Below is a screenshot of an FSCM 'read' on my 2017 SS. My understanding is that we cannot actually read the module, and what we're actually getting is a generic from HPT. Screenshot of FSCM 6994 below.


Attachment 1081682

Nice! Thank you. Still digesting the complexity of this system. Every bit of addl info helps. Esp from working examples.

Also reading up on some articles. Havent tried anything yet but this one seems to have some good info, particularly from user random84 about halfway down. Makes logical sense. Unfortunately its going to be rain rain rain here for the next week, so might not get a chance to try any of this.

https://forum.hptuners.com/showthrea...38-fpcm-tuning

Honestly, in the last log i posted above where i show the "dip not a crash" and it goes up to 80, then back to 60 psi... i dont think thats bad necessarily. Im thinking i dont need 70+ psi if high side pressure is correct at 2300. So thinking i will need to log more.... esp with the params mentioned in the link above. I might drive it a few more times too. I thought id given enough time for air to get out of the system, but maybe there was still air in the fuel line.

I want to keep an eye on the low side pressure increase after i let off throttle. Looks like it comes up to 90 psi and hangs for a few seconds.

[wnta1ss]

Side note, when you have the FSCM licensed the HPT warns about brickable. I don't know if this is just because the 'read' is generic, which means if you flash it, you'd write over any changes previously done to the module?


Another thought, if the fuel flow rate is not actually measured from the lpfp but calculated like the DSX article seems to say, then you might be going over the 381 column? ZL1 ecm file shows 444 lb/hr as it's top flow rate, so not sure if rescaling should be done for your setup (no experience with aux pump on this car myself)? Check ECM 6975 in the ZL1 file that I sent and you'll see that higher flow rate.

[cjperformance]

Originally Posted by wnta1ss

Side note, when you have the FSCM licensed the HPT warns about brickable. I don't know if this is just because the 'read' is generic, which means if you flash it, you'd write over any changes previously done to the module?


Another thought, if the fuel flow rate is not actually measured from the lpfp but calculated like the DSX article seems to say, then you might be going over the 381 column? ZL1 ecm file shows 444 lb/hr as it's top flow rate, so not sure if rescaling should be done for your setup (no experience with aux pump on this car myself)? Check ECM 6975 in the ZL1 file that I sent and you'll see that higher flow rate.

Yeah sounds scary but sounds like people mod the fscm all the time. In any case good to have the forewarning.

Also... need to weed through articles that are talking about gen iv vs gen v. Im sure what applies to one may or may not apply to the other.

Next time im out ill log the params mentioned and see if it exceeds that table.

[KingLT1]

Originally Posted by cjperformance

Its in... mostly... waiting for the overnight curing before i put gas in. Tapping the tank did not inspire me with confidence. The line that attaches to the tank fitting wants to tweak the fitting in a weird way. It leaked a little the first couple of tries. Thats with hardly any gas in it. Im about 50/50 whether its going to leak when i put gas in tomorrow. I did what i could... we'll see what happens.

This is why I prefer the Cordes low side as it uses a bulk head that attaches to the tank. You might look it up and see if you can get that part to integrate with your DSX setup if it gives you any issues. That being said the DSX setup has proven to be pretty reliable so I think you will be ok.

Far as tuning your FSCM needs licensed.

Desired Fuel pressure:

Normal - 50.8psi
High Flow - 72.5psi
Low Flow - 76.1 psi
Cold Engine - 58 psi
Default - 72.5 psi
Fail - 72.5 psi

Fuel Control Module:

Max Desired Pressure- Set 0.0 - 154.8 lb/hr to 81.2psi and 166.7 - 381lb/hr to 81.6 psi


You will have to click on the units and change them from KPA to PSI, but I believe 500kpa is around 72.5psi and 560kpa is around 81psi.

[cjperformance]

Originally Posted by KingLT1

This is why I prefer the Cordes low side as it uses a bulk head that attaches to the tank. You might look it up and see if you can get that part to integrate with your DSX setup if it gives you any issues. That being said the DSX setup has proven to be pretty reliable so I think you will be ok.

Yeah, I'd even be willing to drop the tank and install a bulkhead fitting for peace of mind. Good info. Will add to the list of winter mods planned.

[cjperformance]

Originally Posted by KingLT1

Desired Fuel pressure:

Normal - 50.8psi
High Flow - 72.5psi
Low Flow - 76.1 psi
Cold Engine - 58 psi
Default - 72.5 psi
Fail - 72.5 psi

Fuel Control Module:

Max Desired Pressure- Set 0.0 - 154.8 lb/hr to 81.2psi and 166.7 - 381lb/hr to 81.6 psi


You will have to click on the units and change them from KPA to PSI, but I believe 500kpa is around 72.5psi and 560kpa is around 81psi.

Fantastic info as always!

So... since I can't tune in the rain was doing some math to validate my understanding.

In the vicinity of the low pressure crash, my air lbs/min was approx 63-72 lbs/min. So... if my air lbs/min was 72 then air lbs per hour is 4320 lbs/hr.
Stoich AFR = 14.7 with PE at (approx) .8 that's a 11.76:1 afr

So afr is by weight, so 4320/11.76 = 367.35 lbs/hr fuel.

Looking at my stock "max desired pressure" table I see the flow rates are fairly linear (see image below) dwindling from 79.8 psi down to 47.6. I assume it goes down and not up because the engineers know that as fuel flow increases, pressure will drop on the stock system. Unclear why this is a "max desired pressure table" instead of just "desired pressure", but in any case, my understanding is that the "crash" and "drop" scenarios I'm seeing are because the actual fuel pressure is exceeding this table at the given flow rate and the stock fuel pump is working to lower that, or just working to NOT increase it? By increasing the "max desired pressure" table as King mentioned, it will not try to dial back the pressure.

In the scenarios above, the crash is right around the 63 lbs/min air flow rate which would be around 321 lbs/hr fuel. I would imagine that with the fueling algorithms in the system, there's some kind of gradual taper off or other functionality that is trying to correct things with the in-tank pump, so there's not an obvious correlation to that particular value... but based on my log it looks like the low side fp is attempting to be tapered off... and I'm guessing the algorithm gets to a panic point where it just shuts off the in tank pump completely or goes to some kind of ultra-low flow, thus the crash.

Still trying to figure out what's going on after the 2-3 shift and why I dont see the same thing. Maybe ripping through the RPMs in second gear vs the slower rise in 3rd gear changes the algo.

Maybe logging the requested fuel flow rate on my next few runs will help pull things together. Cant wait to try the changes above. High hopes.

[cjperformance]

Low side fixed! Thanks KingLT1!

Comes up and stays up. A couple of edge cases where the inj pw exceeds 6.0, but much less with the low side staying up. I have everything to replace the high side with LT4 fueling except one fuel pipe, which should get here this week, so that should be fixed soon.

Still got my eye on that little bit of KR that is registering. It's consistently inconsistent. Just thought I'd mention that before someone points it out. Looks like a lot, but the max on that graph is 1. Tried backing off timing by 5-8 degrees. It's less, like .2 instead of .4, but still there, so decided I'm not going to stress over anything less than .5 degree KR and consider it false. I haven't tuned down the sensor sensitivity, just because I'm not 100% its false and want to see if anything changes to make it better or worse.

Some more MAF tuning needed in a couple spots. Prob will wait until high side fuel is done. I'm guessing that's going to throw things off anyway. It's not that far off right now, so not too concerned.

Weather forecast looks like garbage for the whole week. I'd be comfortable doing another 1/4 mile pass at this point. It survived the canned procharger tune at the track, it sure as hell can survive what I've got it doing now.

Looking back at my earlier logs with the procharger tune and I'm absolutely horrified I ran it that way.

[cjperformance]

Fixing the KR was much easier with fueling sorted out. Backing off timing a couple of degrees in spots fixed the issue this time... Pretty much non-existent KR now except for a couple of random one-off spots.

[cjperformance]

Ok, so i guess the high side is going in this weekend. Next week looks nice for doing some lunch break tuning runs.

Do i NEED a lash cap on the hpfp? Or is that just if im trying to eek out every last tidbit of travel?