horrible time tuning big cam

[bjlindell]

I just rebuilt a 347ci NA 11.7:1 SCR and decided to install a 268/270 at .050" 108lsa cam

I first started off the car on E85 and went through attempting to drive it on E85, It would idle fine (sometimes) and not rev to well.
I would attempt to take off but it would "choke" and go lean. I would keep adding fuel when in SD to the VE table in the correct areas and it would still have that issue.

I am now attempting to run it off gas and am having the same issue.
I have a fuel pressure gauge on the car while its running and it reads steady at 58psi when the lean event would occur.

heres a log of whats happening and a tune file.

Was wondering if I can get some input on this.

Also running LS7 style MAF

Thanks!

[MMGT1]

Pic of the MAF installed please if you can...

[DAVECS1]

Get rid of the dip in your VE table from 75Kpa on up. All of your timing tables should match at the idle point, if not this causes stumble. Also your transitions from idle to run are extremely steep.

[bjlindell]

Pic of the MAF installed please if you can...

It is a Halltech Super Bee MF103mm intake for a C6 Z06 corvette.

This is how its fitted in my car

Get rid of the dip in your VE table from 75Kpa on up. All of your timing tables should match at the idle point, if not this causes stumble. Also your transitions from idle to run are extremely steep.

Transistions from idle to run for spark?

I have updated the file with your input. I am now having a big issue when taking off. It doesnt make sense to me at all, the commanded AF is 14.68 throughout the sweep on the one take-off in the log and my injector pulse widths still increases.. It pegs lean (18:1) and stumbles to no power, like if it had TCS. It will idle ok and that is about it.

heres a new log and updated tune file. Now strickly running SD.
Thanks for all your input.

[MMGT1]

Well, the MAF is installed properly, that's good. I've seen more than one have it installed the wrong way and you can imagine the results of that

[MMGT1]

I would set your MAF functions back to normal. The way you will get the best data for VE is under your "Airflow" Tab. Then under "Dynamic Airflow", "Steady State" you will see "Hi Map Delta", "Low TPS Delta" and "Hi TPS Delta". 0 each of those tables out, flash the car and now you are running strictly from your VE table. The other function works, but this way will give you the most acurate data for VE tuning. These settings will ensure the MAF is never referenced and will only draw information from the VE table. No need to fail or unplug the MAF when done this way

[bjlindell]

I would set your MAF functions back to normal. The way you will get the best data for VE is under your "Airflow" Tab. Then under "Dynamic Airflow", "Steady State" you will see "Hi Map Delta", "Low TPS Delta" and "Hi TPS Delta". 0 each of those tables out, flash the car and now you are running strictly from your VE table. The other function works, but this way will give you the most acurate data for VE tuning. These settings will ensure the MAF is never referenced and will only draw information from the VE table. No need to fail or unplug the MAF when done this way

Thanks for that helpful tip. I never knew about that.
I tried it again with that setup and im still having a hard time getting the car to move. It falls on its face when i start moving.
It seems like no matter what i do with fuel it will still have that issue. feels like im missing something major.

[MMGT1]

What is happening on the WB now when you try to pull from a stop? Still lean then stall? The new VE looks a hell of a lot better. Take the VE error and apply it your VE table for a couple of runs, see if it cleans up at all

[bjlindell]

What is happening on the WB now when you try to pull from a stop? Still lean then stall? The new VE looks a hell of a lot better. Take the VE error and apply it your VE table for a couple of runs, see if it cleans up at all

It still leans out and stalls when I pull from a stop.
It is still rich at idle (13:1) and with this cam i idle around 85kpa at around 1200rpms. When i take off from a stop it will rev up to about 1200rpms at 95kpa and peg lean. But looking at the VE table the numeric is about the same in that engine speed area.

its very frustrating at times.

Ill keep trying to apply VE error to my VE table after a couple runs and see where that gets me.

Thank you very much for your help.
ill let you know what happens

[DAVECS1]

If you idling around 85 Kpa I would check for a vacuum leak. I have seen 108 lsa cams in an LSx and even the wildest ones can manage 60 kpa. I have a fast 102 also and about a week ago I had to take it out and resell,the halves together with rtv and loctiting the bolts so they did not come loose again.

If it truly idles at 85kpa that leaves u about 6 cells t transition from idle to wot. Your timing tables and ve table will have to look vastly different with tons of pe

[MMGT1]

Dave is onto something there. A can of brake cleaner to check that manifold is a good idea

[zippy performance]

Your vacuum readings are in the ball park for that cam with that small of a motor. That is a tiny motor for that much cam. Before you ever go into turning the maf on you need to dial in the v.e. table. I have no idea how you plan to make it run on a maf properly. I can only see this working correctly with an SD Enhanced tune so you can tune with map and tps. I would recomend changing the open loop FA table to get more time in a 1.0 multiplier when warmed up. I would move your p.e. tps settings higher because right now almost any normal aceleration will put you in p.e. mode. You need alot more spark advance for part throttle also. You have a rev limiter for bad v.s.s. set higher than the resume which can cause issues also. There are many other changes to make, but those are the first to start with.

[DAVECS1]

Well if the ca, truly idles there. I am not sure runnin closed loop would buy anything. If one was to do closed loop I would do something like let it use the pe table for idle as an open loop and them let it transition to closed loop for the handful of cells it will use for cruise.

Looking at the pictures though, that is a cable tb. Looking at his tune, his base runnin airflow would not seem to support that tb with that cam. Leads me to believe the air is coming from somewhere else

[bjlindell]

If you idling around 85 Kpa I would check for a vacuum leak. I have seen 108 lsa cams in an LSx and even the wildest ones can manage 60 kpa. I have a fast 102 also and about a week ago I had to take it out and resell,the halves together with rtv and loctiting the bolts so they did not come loose again.

If it truly idles at 85kpa that leaves u about 6 cells t transition from idle to wot. Your timing tables and ve table will have to look vastly different with tons of pe

That is a good idea, I will probably check it for leaks with propane.

Dave is onto something there. A can of brake cleaner to check that manifold is a good idea

I believe so also, I will check it with brake cleaner/propane

Your vacuum readings are in the ball park for that cam with that small of a motor. That is a tiny motor for that much cam. Before you ever go into turning the maf on you need to dial in the v.e. table. I have no idea how you plan to make it run on a maf properly. I can only see this working correctly with an SD Enhanced tune so you can tune with map and tps. I would recomend changing the open loop FA table to get more time in a 1.0 multiplier when warmed up. I would move your p.e. tps settings higher because right now almost any normal aceleration will put you in p.e. mode. You need alot more spark advance for part throttle also. You have a rev limiter for bad v.s.s. set higher than the resume which can cause issues also. There are many other changes to make, but those are the first to start with.

Thank you for the tips I appreciate the help! I adjusted my open loop FA table to a 1.0 multiplier in the 122 to 230*F.

I moved my PE TPS higher from where it was and fixed the bad v.s.s. resume/cutoff.

How much more spark advance you think would need to be added for part throttle?

Well if the ca, truly idles there. I am not sure runnin closed loop would buy anything. If one was to do closed loop I would do something like let it use the pe table for idle as an open loop and them let it transition to closed loop for the handful of cells it will use for cruise.

Looking at the pictures though, that is a cable tb. Looking at his tune, his base runnin airflow would not seem to support that tb with that cam. Leads me to believe the air is coming from somewhere else

as a reference you think the RAF numbers are too low for the TB and cam?

[DAVECS1]

Yea I would think so. At 85 kpa your needing 60% of the required engine airflow just to keep the engine lit.

Also your Desired airflow max is set low which is probably limiting that overall adjustment electronically. If it is working you may just have the throttle blades cranked open manually. Why is there no airflow for P/N?

Also are you running a returnless fuel system> Your injector flow rate is setup as such. If not you are progressive leaning out the vehicle by specifying a larger flow rate with increase in vacuum

Your spark tables look much better. I would take the idle section from the Drive table and past it into the low and high octane, and then smooth the transition

[bjlindell]

Yea I would think so. At 85 kpa your needing 60% of the required engine airflow just to keep the engine lit.

Also your Desired airflow max is set low which is probably limiting that overall adjustment electronically. If it is working you may just have the throttle blades cranked open manually. Why is there no airflow for P/N?

Also are you running a returnless fuel system> Your injector flow rate is setup as such. If not you are progressive leaning out the vehicle by specifying a larger flow rate with increase in vacuum

Your spark tables look much better. I would take the idle section from the Drive table and past it into the low and high octane, and then smooth the transition

I raised the Desired Airflow Max to 64g/sec now. there is no P/N due to the stock tune file not filling that area since its a manual. I copied my Drive to P/N now for the RAF.

I am running a RETURN system. So i will just have to invert my IFR table? so that the 0kpa point will have to be a higher numeric than the 100kpa cell?

I replaced the idle area from the in drive spark tables to the high and low octane tables.

Will give that a try and let you know how it goes

Thank you very much for all your help so far. appreciate it!

[zippy performance]

With such a small motor you aren't going to need a big number in your base idle tables. You set your minimum idle by drilling a hole in the TB just as GM did from the factory. Bring the throttle blade as closed as you can get it without it being sticky and drill the blade until you are idling with the engine warm and the fans off with the IAC at around 20-40 counts. If you are running a return system with a vacuum line going to the regulator then you need your ifr table to be whatever the size of the injectors is. If you have no vacuum line running to it then you run the table as you would a returnless system (same as stock). If you are planning to run it on E85 you might as well switch it back over.

[bjlindell]

With such a small motor you aren't going to need a big number in your base idle tables. You set your minimum idle by drilling a hole in the TB just as GM did from the factory. Bring the throttle blade as closed as you can get it without it being sticky and drill the blade until you are idling with the engine warm and the fans off with the IAC at around 20-40 counts. If you are running a return system with a vacuum line going to the regulator then you need your ifr table to be whatever the size of the injectors is. If you have no vacuum line running to it then you run the table as you would a returnless system (same as stock). If you are planning to run it on E85 you might as well switch it back over.

Sounds good, ill follow those steps.
ill probably switch back over to E85 now since i know its doing the same thing on gas... Just wanted to prove it out.

[bjlindell]

Im thinking from when i switched from Gas to E85 originally i might have broken up old deposits from the gas in the tank and when i had E85 sitting in the tank for a will it cleaned up the tank a little and started clogging the fuel filter. Im going to check that out and see what comes of it...