Another 411 swap

[Jay@HAP]

I have this 97 Chevy truck in the shop. Someone else did the swap and someone else provided the base tune. This is first 411 swapped vehicle I've tuned. Fixed a bunch of problems with the truck, broken valve springs, 02's, etc.

It's a 383 with an unknown cam, LT headers. Stock spider intake.

This is the 1st vehicle I've ever had to drill a hole in the T/B to get enough air to idle properly. Started out idling at 75 kpa. Played with fueling, didn't help. I tried opening the T/B blade first like usual but it needed more air. Slowly increased the hole in the TB and now it's idling at 49kpa. IAC counts are decent, will probably have to mess with the Effective IAC Area table now.

Anyhow, trims are decent at idle, as soon as you get off idle it's adding a ridiculous amount of fuel. The VE table is just a base and normally have to take fuel out. There is no way this needs that high of VE at part throttle and cruise.

I changed the cylinder litres to a 383(it was still for a 350)and that didn't make any difference. I looked at the injector data and compared it to some of the tunes in the other 411 thread and they seem to be OK.
I verified fuel pressure and it's good. I checked the cam offset angle and found the dist. was a tooth off. I fixed that, now it's .5-1.0 degree.

Can someone take a look at the tune and see what I have over looked?

[Area47]

taking a shot in the dark here. were the transient tables changed for the SBC vs ls1?

[Jay@HAP]

that is a very good question for which I don't have the answer for at the moment. I will check.

[Oleblu]

More than likely an express van tune. So transient should be setup for the 5.7. Curious what's the wideband showing you?

I havnt checked the tune file so I might be making an idiot of myself.

[Jay@HAP]

Tune shows its from a 01 Savanna 3500 OS is 12208322

I don't have a WB on it yet. I started out doing some drivability first on the street using STFT

I also have a pretty big fuel trim split from bank to bank.

[Jay@HAP]

Well this thing is still kicking my ass. I found the truck had the wrong headers on it and the ports were way to big for the head and had blown the gasket out on #1. I thought this would fix my Bank ! problem. Wrong.

1st time I started it, Bank 1 02 sensor went all the way lean like before. But when it hit C/L Bank 1 was pulling out 5% or so and Bank 2 was pulling out 25%.

2nd time I started it Bank 1 and Bank 2 are split buy 10-15% just like before.

I didn't build the base tune for this and honestly I don't know if the injector data is correct or not. I've compared it to several other 411 swap tunes I've seen and for the most part it's close.

If someone has time to look at the tune and the two logs I would greatly appreciate it. This thing is flat out kicking my ass.

Compression on all cylinders is 210, did a relative compression test with the scope and looks good. Looked at the header tubes with a thermal heat image gun and all are the same temp.

[Fast4.7]

I have this 97 Chevy truck in the shop. Someone else did the swap and someone else provided the base tune. This is first 411 swapped vehicle I've tuned. Fixed a bunch of problems with the truck, broken valve springs, 02's, etc.

It's a 383 with an unknown cam, LT headers. Stock spider intake.

This is the 1st vehicle I've ever had to drill a hole in the T/B to get enough air to idle properly. Started out idling at 75 kpa. Played with fueling, didn't help. I tried opening the T/B blade first like usual but it needed more air. Slowly increased the hole in the TB and now it's idling at 49kpa. IAC counts are decent, will probably have to mess with the Effective IAC Area table now.

Anyhow, trims are decent at idle, as soon as you get off idle it's adding a ridiculous amount of fuel. The VE table is just a base and normally have to take fuel out. There is no way this needs that high of VE at part throttle and cruise.

I changed the cylinder litres to a 383(it was still for a 350)and that didn't make any difference. I looked at the injector data and compared it to some of the tunes in the other 411 thread and they seem to be OK.
I verified fuel pressure and it's good. I checked the cam offset angle and found the dist. was a tooth off. I fixed that, now it's .5-1.0 degree.

Can someone take a look at the tune and see what I have over looked?

You would be very suprised how much VE I had to add for a factory 350 with both a LT1 F-car cam and a different 350 with the 395' Marine cam. Both had headers and a decent exhaust too. I also tuned a STOCK 5.7 in an Express chassis van with only Thorley Tri-Y headers. Headers alone required me to add 10-15% across the whole curve both part-throttle and WOT.

[Obsolete489]

Well this thing is still kicking my ass. I found the truck had the wrong headers on it and the ports were way to big for the head and had blown the gasket out on #1. I thought this would fix my Bank ! problem. Wrong.

1st time I started it, Bank 1 02 sensor went all the way lean like before. But when it hit C/L Bank 1 was pulling out 5% or so and Bank 2 was pulling out 25%.

2nd time I started it Bank 1 and Bank 2 are split buy 10-15% just like before.

I didn't build the base tune for this and honestly I don't know if the injector data is correct or not. I've compared it to several other 411 swap tunes I've seen and for the most part it's close.

If someone has time to look at the tune and the two logs I would greatly appreciate it. This thing is flat out kicking my ass.

Compression on all cylinders is 210, did a relative compression test with the scope and looks good. Looked at the header tubes with a thermal heat image gun and all are the same temp.

You're sure there isn't a dead plug or bad wire? I know if I have a misfire from a bad wire it'll show up lean by about 15% on one bank. Though looking at the log, that doesn't seem likely, they follow each other well - almost too well.

This has to be some sort of physical issue, not tune related in my opinion. Have you tried swapping the o2 sensors back and forth to see if the trims change? Does the engine run smoothly?

[Jay@HAP]

You're sure there isn't a dead plug or bad wire? I know if I have a misfire from a bad wire it'll show up lean by about 15% on one bank. Though looking at the log, that doesn't seem likely, they follow each other well - almost too well.

This has to be some sort of physical issue, not tune related in my opinion. Have you tried swapping the o2 sensors back and forth to see if the trims change? Does the engine run smoothly?

Thank you for the reply. I just now saw it. The truck has freakin straight pipes so it's really hard to say how good it's running. Looking at it with a thermal imager all the headers tubes look the same.

I agree that I don't think it's in the tune but I won't rule anything out at this point. I spend this afternoon going through the pinouts on the ECU for the injectors and they are correct.

I haven't swapped the 02 sensors to see if the problem follows which is a good idea. I don't know if the harness is long enough to do that. I will have to look into that.

This thing is kicking my ass. Dislike the truck......very much I do.

Thank you for the replies.

[Obsolete489]

I mean swap the sensors, not the connectors, just to see if one of the sensors has an issue.

[Jay@HAP]

I had swapped the sensors before which made no change. I swapped connectors and Bank2(which is really Bank 1)showed the same thing so that kinda rules out a wiring issue. Could there be that much reversion in that stock CFI intake with the aftermarket cam?

Off idle the trims are still split though.

[Obsolete489]

Seems unlikely to me since it is so consistent? Really don't know.

What about the injectors, you said they were stock right? Maybe one of them has an issue?

[Jay@HAP]

They were updated to the newer style MPFI style. When I pulled the intake I found several of them were leaking. This problem was still present then. Even after fixing everything I found wrong, I still have the same issue. I really thought when I found the #1 exhaust gasket blown out because it had the wrong headers on it would fix the issue.

[Jay@HAP]

Here's a log I took earlier after swapping the 02 connectors back to the same side. I didn't give it throttle till the end of the log where the trims are split at higher rpms.

[Obsolete489]

Just because its new, it doesn't necessarily mean its not the problem, unfortunately. Since the trims get closer together when you give it throttle it about has to either be an injector issue, or a small vacuum leak..