Understanding Cranking Tuning - How difficult should it be to start a mild cam build?

[evilstuie]

Hi All,

All my previous tuning and problem solving has been on a SBC 24x conversion which was working great but for some reliability and less oil leaks decided to move across to an LS1 5.7L.

The motor is stock bottom end, has a VCM710 cam, 232/234@110, 241 higgins ported heads, shaved down 30 thou, and a fabricated intake manifold (ebay ripoff of holley sniper).
Using stock injectors, 58psi fuel system with return line, 102mm TB, and trying to do a MAFless tune.
Cam: https://www.lsxperformanceparts.com....ance-camshaft/


My main question is, should it be so very difficult for this type of build to get started?
From a lot of videos I've looked at most people can put a different cam in and still get the car started after cranking for a bit.

I cranked for about 30 seconds with the engine popping and banging and almost starting but never got it to fire and run on its own.

I'm trying to understand and determine if I should be looking for electrical issues (wiring, grounds, power, sensors etc), or if I should be looking at the tune, or worse, mechanical issues.

Currently the motor has open headers, no o2 sensors installed, and MAF disconnected.

Question 1. With the motor specs I have, should I expect it would start without a significantly different base tune, or would this never start without changes?
Question 2. with the P0101, 102 & 103 disabled, will I be able to start the motor with maf disabled, or would this be half my problem?
Question 3. Should I install the MAF and get it tunes that way first, then look at MAF delete / SD only?
Question 4. Do I need the o2 sensors plugged in to get it started, or will it be ok until the PCM tries to switch to closed loop?


Current base tune attached (modified VY commodore LS1 manual with VATS removed, 4l60e selected, some changes to crank spark (+4degrees)and slight change to primary VE)
and the log of trying to start it.

Edit:
Also noticed the TPS is sitting at 0.11v but there's no way to adjust it like the old TPI ones, will have to drill out the screw holes or adjust via the TB adjustment but that might be a bit much to get to 0.48-0.52v

2nd Edit:
I'm not looking to get the complete tune done on this, just enough to start, idle and drive it easy 5kms to get the proper tune done.

[[email protected]]

answer 1: you should be able to pump the gas if the motor is running good like if you are to lean of if your base starting airflow is too low
9so if you have to little fuel pumping the gas should get you more fuel like this you can at least see if its just the tune /at the same token if its getting to much fuel you can do a flood clear basically anything after 85%tps i think may be 100% will stop the injectors from firing however if your stating popping that can be from ignition timing being to low or too much fuel i don't remember if the motor has a distributor but try to verify timing i have the same motor with the same pcm only difference is mine is a vortec and injectors

answer 2 :if these trouble codes are set the motor will reference the sd tune i would leave the maf connected and see what you getting just to get the dtc to turn off and create more issues but it should still run if maf fails it can read map and if those both fail then it switches to tps i believe

answer 3 i would leave the maf connected just to eliminate issues as stated above and personally i run a sd tune only remember that the ecm has complete different values in there it may barley run with the new set up if not at all, these things you have done to the motor rob vacuum and performance on the low end so it will need more air to just idle and not fall on its face so yes you would need a tune to get it going and then custom tuning to get it dialed in either street or dyno but if you dont have a wide band set up then the dyno my be good for you but if you want to tune yourself then you ill need your o2 sensors to get started with idle and cruising throttle and a wideband (i use a aem 03-300x) to look at values of pulls and power enrichment

answer 4 the car should still run with out o2 sensors but yuu will not have any way of identify how rich or lean you are so it may be hard to even get a base tune in and partial throttle and it shoulnt try to go into closed loop but you can shut that off

i tune on the side so lmk if you have any other questions you can shoot my a personal message or a email might be better its my name lol or if you need a base tune i can help you out and guide you from there

also you need to log your inj data so you can see the pulse with

[07GTS]

do not disable the maf codes u need them to fail first with no maf so it uses SD properly, the engine will not run closed loop without the 02's they are needed for it to be in closed loop, if they are unplugged it may cause issues u cant tune around u would be better for them to be in and not used then unplugged, u need to get a wideband that can be accurate so u know there fueling is otherwise its just guesswork as to where ur at

[evilstuie]

do not disable the maf codes u need them to fail first with no maf so it uses SD properly, the engine will not run closed loop without the 02's they are needed for it to be in closed loop, if they are unplugged it may cause issues u cant tune around u would be better for them to be in and not used then unplugged, u need to get a wideband that can be accurate so u know there fueling is otherwise its just guesswork as to where ur at

Yeah I've got them to set to MIL on 1st
I know the o2s are needed for closed loop but for the moment I don't have the exhaust connected up and just trying to get it to start, but i wasn't sure if the PCM needed to see them connected at least to start up.
I've got a wideband that I run off the EGR pin but again it's not connected because I thought it wouldn't be needed for initial fire up, only after it was running, but the cranking and open loop just works purely from the tune tables yeah?

[07GTS]

u may need to have the 02 at least plugged in as some wont like it and command richer no matter what for safety, even if u keep it in constant OL so the 02's arnt used just make sure they are plugged in, when in OL its only using the values in the VE table for fueling with whats commanded eqratio if ur not using the maf, so if they are right or not u wont know 100% till u have the wideband going

[evilstuie]

u may need to have the 02 at least plugged in as some wont like it and command richer no matter what for safety, even if u keep it in constant OL so the 02's arnt used just make sure they are plugged in, when in OL its only using the values in the VE table for fueling with whats commanded eqratio if ur not using the maf, so if they are right or not u wont know 100% till u have the wideband going

No worries, I'll give it a try this afternoon and see how it goes.
I'll modify the TPS sensor so I can make the adjustments to the voltage.

I'm still um'ing and ah'ing about drilling a hole in the throttle body blade.
Most similar cam builds need to do it, and it seems to be a better way of letting air in and keeping the ramp rate of the throttle blade opening from zero to WOT rather than opening it with the adjustment screw and resetting the TPS to 0%.

I just didn't want to drill it and then find out later I need to fill it in.

Thanks for the help guys

[crew chief]

The tune you have posted does not have the maf set to mil on first or was this one a work in progress

[2xLS1]

You don't need O2s plugged in to start and run.

[evilstuie]

The tune you have posted does not have the maf set to mil on first or was this one a work in progress

Yeah sorry, was work in progress.
I'll post the latest one this afternoon after my success/failure trying t start it

[evilstuie]

ok, so I drilled out the TPS screw holes as well as dremmeled off the plastic keyway so I could rotate the sensor slightly and now have the TPS voltage 0.45v at 0%.
I also drilled a 4.5mm hole in the opening.

The motor still seems to be struggling with turning over even with 13.6v so I've ordered a 4hp torque reduction starter to give a hand with that.

The engine seemed more willing to kick over and start but still didn't get there.
I tried plugging the MAF back in but didn't have a 102mm-95mm reducer to attach it on to actually read air flow so I'll grab one of them tomorrow.
I might also revert back to an earlier tune save and leave MAF enabled, just to see if it helps get it started.

In all honesty it only needs to start, idle and put down the road to the tuners, so SD tuning probably isn't required by me yeah?

[4wheelinls1]

This should start and run, all you need to do is pull 15-20% out of the VE table around idle 0-1400 RPM up to 80 kpa. Popping suggests a more serious issue, are the coils wired correctly? Do you have too longer push rods holding valves open, is the cam timing correct? I have done dozens and used to do support for VCM, even a totally stock tune would start and run, once the car goes into closed loop it would lean out with a fuel trim error around -20%.

[evilstuie]

Thanks. This is exactly what I was looking for.
With the 30 though saved off the heads the original pushrods were too long so I got slightly shorter ones and checked the piston clearance with putty.
It was a while ago I put the motor together but pretty confident I set the cam timing correctly.

rocker adjustment is probably my next thing to check if I'm chasing a mechanical issue.

Coils are stock, same as wiring harness so there's no chance they're around the wrong way. From memory LH and RH packs are interchangeable yes?

Any chance you'd have tune to suit this setup?
Otherwise I'll start from scratch and make the changes you suggested after checking the rockers and maybe inspection camera in the spark plug holes to check.

[akalshaikh]

are you sure cam sensor and crank sensor are good? do you get RPM reading during cranking???
it should run with minor changed for your mods and you dont need O2 sensor. I recently had the same issue with LS3 swapped firebird except it did not pop and bang. turned out to be clogged injectors and some grounds loose.

SD is not required to be honest but eventually you'll have to dial in your VE tables along side your MAF. if you doubt the MAF then you should fail the maf and force it into SD

EDIT: You did not fail the MAF properly in your tune file.
EDIT2: Go under idle > Airflow > Max Idle - Park/Neutral --- You have this set at 0 RPM, increase it back up to 1200 RPM.

If anything try this file

[evilstuie]

are you sure cam sensor and crank sensor are good? do you get RPM reading during cranking???
it should run with minor changed for your mods and you dont need O2 sensor. I recently had the same issue with LS3 swapped firebird except it did not pop and bang. turned out to be clogged injectors and some grounds loose.

SD is not required to be honest but eventually you'll have to dial in your VE tables along side your MAF. if you doubt the MAF then you should fail the maf and force it into SD

EDIT: You did not fail the MAF properly in your tune file.
EDIT2: Go under idle > Airflow > Max Idle - Park/Neutral --- You have this set at 0 RPM, increase it back up to 1200 RPM.

If anything try this file

RPMs are logging, so cam sensor is working, same as MAP
The only sensor I'm not sure on would be the crank sensor, not sure if there's a PID I can monitor for that.

I'll give the tune file a go and see if there's any change this afternoon.

[[email protected]]

RPMs are logging, so cam sensor is working, same as MAP
The only sensor I'm not sure on would be the crank sensor, not sure if there's a PID I can monitor for that.

I'll give the tune file a go and see if there's any change this afternoon.

i do not think you would be logging rpm id the crank sensor wasn't working ?

[evilstuie]

i do not think you would be logging rpm id the crank sensor wasn't working ?

Not sure. I'm pretty sure on the 24x conversion the cam sensor (vortec distributor) was what the rpm based on the 1x signal.
The 24x signal from the crank sensor was just for figuring out the compression/exhaust stroke.

Using the stock harness unaltered this time around instead of repinning for SBC I was hoping to avoid all these sort of problems.
The popping and backfiring when cranking if it's not a sensor then the most likely cause 4wheelinls mentioned I think.

I'll try to check the timing this afternoon as well and make sure I didn't do something stupid like set the timing to the exhaust valve or stroke when putting the motor together.

[evilstuie]

so without doing anything else yet to the tune, I did a bit of work on the exhaust joins and got that mocked up, tacked and in place.
The put the new 4hp starter motor on.
Now I can kick the ignition and split second later the engine starts.

Of course a split second after that it cuts out. But no bang or splutter so I think the starter was on its way out and just cranking so slow it was causing issues and fuel pooling etc. That's my guess anyway.
I'll try the tune file you uploaded and see if that gets it to keep running/idle and go from there, but I feel a bit better that I don't have to start ripping the motor apart looking for mechanical issues.

More to come after a trip to the shops....

[evilstuie]

Got back a bit late, but pretty sure akalshaikh nailed it with the 0rpm tables.

Apparently it's a common problem when you use a manual base tune with an auto.
I'll give it a try tomorrow.
I'll also try to find an auto base file just to make sure there's no other table issues

[akalshaikh]

Happy it helped

[evilstuie]

Happy it helped

Yeah its running now, a bit rough but I haven't got the Wideband wired in to the EGR pin yet so I'll get that done tomorrow and get teh new brake system bled then I can start to do some proper logging and tuning.
But the good news is it runs and stays running and nothing exploded or caught fire (yet)

Edit:
There was also a ground missing from the back of the motor. I found this out by jumping a ground to the ECU casing and it made it a lot easier to start, then traced the missing ground point.