L29 454 Vortec with 0411 swap - Timing at WOT

I spent a year building a 7.4L vortec for my 97 K3500 dually. I worked on the heads for a couple months. I ported and cc matched the ports (flowed 295 cfm on intakes), chambers were cc matched and polished, and the manifold was matched and ported. I put in a comp cams 08-411 cam (212/218 at .050), built my own stainless headers, put in 36 lb/hr Bosch injectors from 5-0 racing, and swapped to a 0411 ecm. I bought the ecm on ebay and had it loaded with the L31 350 van tune for a starting point. I made several posts on this board in the last few years with questions about buying an HP setup and tuning it myself. I decided it was too much to take on from ground zero, so I sent it to Black Bear performance for tuning.

My question has to do with efi wot timing. What is factory timing in the 98-06 gen 3 era? By normal wedge-head engine building, you use 34-36 degrees wot advance, all in by 3500-4000 rpm. And that's with a carb and conventional distributor. The vortec direct port injection will have perfect fuel distribution compared to a carb, plus less spark wander than a conventional distributor. There should be far less tendency for any one cylinder to approach detonation before the others.

When the 0411 first came back from Black Bear, there was only 22 deg at wot. Cruise timing was way low too, mid 20's rather than mid 30's. I sent it back with the data logs and asked for more timing. They did add cruise timing, but wot is still 22.0. For the record there is no trace of knock. I wrote back and asked why they didn't add wot timing, and they say 22 is what it should be. Am I wrong here? Do efi engines need that much less? Won't the knock sensors immediately pull timing if there is knock?

It should take at least 28 degrees up to 34ish maybe more but that would be a good range to start in.

The stock express van tunes are neutered really badly. They want to make them bullet proof for people abusing those vans.

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Originally Posted by Scott-m

I decided it was too much to take on from ground zero, so I sent it to Black Bear performance for tuning.

When the 0411 first came back from Black Bear, there was only 22 deg at wot.

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You'll end up tuning it anyway if you want the most out of it. You did all those cool mods, but don't expect one of their cookie-cutter tunes will take advantage of them.

I do plan to buy an HP setup and play with it til the cows come home. What is stock timing? Is it really that low? If so it must be related to emissions, maybe to reduce NOx.

To recap, my 0411 ecm had been to Black Bear 3 times, once for an initial tune then twice more for adjustments. It had only 22 deg advance at wot the first time, still only 22 degrees after first adjustment and still only 22 after the second adjustment. They said that's what it should be and any more was risking 'destruction'. I said nonsense, any chevy v8 and for that matter any wedge-head v8 engine wants 34-36 deg at wot. Low timing in a stock tune is to reduce NOx, not to protect the engine from destruction. So I sent it up for a 4th time. I said I want the wot advance curve to be 20 deg at 2000, 30 deg at 3000, and a very conservative total of 32 by 3500 and up. I even included this timing advance graph from MSD distributors. So it comes back again and guy said they advanced the spark tables 'as I requested'. I don't really know what that means, but now it pings at part throttle. I requested more timing only at wot. Is it not possible to add timing only at wot? It has to go up across the board? I don't believe it. The 0411 is supposed to be a very capable ecm. How can it be less tunable than the advance curve in a distributor?


Attachment 143674

Timing is adjust based off predicted air flow.
So yes it can be adjusted at "WOT" only.

Ok what do I tell them to get what I want?

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Originally Posted by Scott-m

Ok what do I tell them to get what I want?

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Don't tell them anything. If they don't know I wouldn't want them tap tappy tappin in my PCM. Tell them send it back and buy your own HPT or pay someone who has some big block experience.

Also, you aren't sending them any data logs, correct? I wouldn't even make changes to it even at your request if I was unable to look at data logs.

PCM exchange programs aren't intended to dial a vehicle in. They're intended to get one running, that's it. If it starts and runs their job should be done.

Retarding timing way more than optimum will typically increase emissions as it's incredibly inefficient. NOX may drop but HCs will go through the roof.

As Alvin said that motor will need every bit of 30 degrees of WOT timing.

I am recording and sending them log files.

I bought the 0411 on ebay and had them load it with a stock tune from a 2001 L31 350 van tune. That tune allegedly had only 16 deg at wot, and someone on another forum said that's because the factory is trying to protect the tranies on abused fleet vans.

I finally made some data logs on the latest tune, including wide open. They did finally add wot timing alright, all the way from 22 to 34. Well 34 is too much. It was pinging and knock retard was kicking in. So I will send it up and have them dial it back to 28 max. The injector duty cycle is only 50% at wot and 4,200 rpm. Does that mean the injectors are way too big?

Stock 7.4L injectors are only 22 lb. If your IDC is that low it might not be entering PE. There are huge PE delays GM put in their calibrations to go along with their low stock timing.

Do they offer email tuning? The mailing back and forth is a pain.

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Originally Posted by Scott-m

I am recording and sending them log files.

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Then why are you having to physically send your PCM to them? Seems like an unneeded step.

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Originally Posted by edcmat-l1

Then why are you having to physically send your PCM to them? Seems like an unneeded step.

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"I do plan to buy an HP setup"

It's been a frustrating process sending it back and forth a million times, but I wasn't ready to take on tuning from scratch. Where do you recommend buying the HP from? Direct or an ebay seller with the extra credits?

Direct from HPT in case there is a problem. Should be the same price.

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Originally Posted by Scott-m

It's been a frustrating process sending it back and forth a million times, but I wasn't ready to take on tuning from scratch. Where do you recommend buying the HP from? Direct or an ebay seller with the extra credits?

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I'M an HPtuners dealer I sell the interfaces as well as a tuning service.

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Originally Posted by edcmat-l1

I'M an HPtuners dealer I sell the interfaces as well as a tuning service.

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In Joey Tribbiani voice, "How YOU doin?"

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Originally Posted by Alvin

It should take at least 28 degrees up to 34ish maybe more but that would be a good range to start in.

The stock express van tunes are neutered really badly. They want to make them bullet proof for people abusing those vans.

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Guess you have not done much tuning on a 454 with those heads or an 8.1L for that matter. 24-26 is pushing the limits on 91 much less 87 octane. My personal 8.1L in my 99 Tahoe made peak power on 26, but I ended up pulling it back to 24 because it had random knock retard in hot weather. 8.1L from a van, HO marine cam, long tubes and a 4" air intake. 7.4L vortec and 8.1L basically share the same combustion chamber design. With the stock 7.4 and 8.1 truck manifolds have to pull a few degrees of timing near peak torque like a TPI small block as well because of the manifolds added VE in that area.

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Originally Posted by Scott-m

I finally made some data logs on the latest tune, including wide open. They did finally add wot timing alright, all the way from 22 to 34. Well 34 is too much. It was pinging and knock retard was kicking in. So I will send it up and have them dial it back to 28 max. The injector duty cycle is only 50% at wot and 4,200 rpm. Does that mean the injectors are way too big?

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I still feel like 28 is too much even on 91+ octane. 24-26 is about as much as I would dare on 91. No more than 22 on 87. Curve can be a little quicker at lower rpm and the negative values brought up to about 4-6*, but definitely needs a 4-6* dip near peak torque compared to timing at say 2,400-3,000 and over peak torque.

Why hasn't the tune been posted?

He doesn’t own hpt and has been mailing his ECM off for updates.

This thread is a giant circle jerk.

K dooosh. Being a diik gets you nowhere. Maybe my 44 years of race engine building could have helped you with something.

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Originally Posted by Fast4.7

I still feel like 28 is too much even on 91+ octane. 24-26 is about as much as I would dare on 91. No more than 22 on 87. Curve can be a little quicker at lower rpm and the negative values brought up to about 4-6*, but definitely needs a 4-6* dip near peak torque compared to timing at say 2,400-3,000 and over peak torque.

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OK thanks, this is great info. The heads are ported and flow matched (295 cfm). I even flowed them with the manifold on. The chambers are unshrouded, polished, and cc matched (105 cc +- .2 after an .020 flat mill). The valves are mirror polished. Block decked .010 and compression heights are within +- .001 inch. Static compression is 9.08:1. The sharp chamber edges and protruding plug threads and other preignition points are gone. Does this suggest it will want more timing or less? Normally that kind of work lets you run more timing on a conventional chevy. Also I never saw even a trace of knock retard until they shot the timing up to 34. Then it was retarding 3-4 deg. What kind of timing would you expect at moderate part throttle, say 8 inches manifold vac? At light part throttle cruise its getting 30-35 deg at 2,000-2,400 with no knock. I will in fact buy an hp setup now that I'm coming to understand the tuning parameters.

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Originally Posted by Scott-m

K dooosh. Being a diik gets you nowhere. Maybe my 44 years of race engine building could have helped you with something.

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Yeah ok then why are you asking about the timing curve on a BBC? I already told you.

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Originally Posted by SiriusC1024

You'll end up tuning it anyway if you want the most out of it. You did all those cool mods, but don't expect one of their cookie-cutter tunes will take advantage of them.

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Guessing at WOT spark without a log is completely idiotic. Is AFR correct? What cylinder airmass? Knock sensors working? Well we can't tell without a tune and log. Buy HPT and start putting in work. Come back when you get serious.

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Originally Posted by Scott-m

OK thanks, this is great info. The heads are ported and flow matched (295 cfm). I even flowed them with the manifold on. The chambers are unshrouded, polished, and cc matched (105 cc +- .2 after an .020 flat mill). The valves are mirror polished. Block decked .010 and compression heights are within +- .001 inch. Static compression is 9.08:1. The sharp chamber edges and protruding plug threads and other preignition points are gone. Does this suggest it will want more timing or less? Normally that kind of work lets you run more timing on a conventional chevy. Also I never saw even a trace of knock retard until they shot the timing up to 34. Then it was retarding 3-4 deg. What kind of timing would you expect at moderate part throttle, say 8 inches manifold vac? At light part throttle cruise its getting 30-35 deg at 2,000-2,400 with no knock. I will in fact buy an hp setup now that I'm coming to understand the tuning parameters.

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Scott,

I would say at 8 in/hg vacuum, maybe 20-24* if it is over 3,000 rpm, like part throttle kickdown, running uphill kind of scenario. If its lower rpm, like 2,000 maybe as little as 16* Remember almost every vacuum advance can is down near zero by the time the manifold vacuum is down at 7-8 in/hg. Usually those start advancing about there and are full in 16* by maybe 12-14 in/hg. Stock Chevy distributor mechanical curves are also assymetrical, more advance rate at low rpm and tapers off at higher rpm. 22* HEI mechanical advance that is typical (GMPP HEI which is practically identical to the truck smog era stuff) is something like 0 @ 1,200, 12 @ 2,200, 18 @ 3,000 and 22 @ 4,000. Then add your initial to that, basic 454 was something like 4* initial for 26 total and that was on a 454 peanut port head engine with less than 8:1 compression. Keep in mind a higher compression engine, in a heavy truck, with a long runner EFI intake, using fast burn style chambers is not going to want as much timing by general rule of thumb. Personally for an 0411 or P59, I would start with the 8.1L timing tables and make small changes from there. The 8.1L has basically the same chamber design, better head flow and more compression, the cylinder pressure developed with the 8.1Ls greater VE is going to be a fairly decent match in my opinon to a 7.4L with head/intake porting, cam upgrade and more compression.

The 2nd issue if datalogs were not made, it is impossible to know where your engine is operating at a given point in the spark timing map. A stock engine may see a cylinder load of 0.64 gm/cyl at peak torque and taper off to 0.54 gm/cyl at high rpm. Mild engine may see 0.78 gm/cyl at peak torque and taper off to 0.64 gm/cyl. An engine like my 383 sees over 1.00 gm/cyl at peak torque. That number is very close to a VE%. It is a basically a real time measurement of VE based off dynamic airflow from the MAF and VE table that is being used as a load reference for the spark map. The OE timing curve was calibrated to run within the operating range of the OE engine. Once you exceed that GM merely dropped the advance numbers to extremely low values because they did not calibrate the whole table because the stock engine never ran there. A stock L31 Express tune sees about 24-26* total timing at WOT when it is in PE. Assuming IATs are under 90F and the CTS is under 194F. With IATs in the 180F range and CTS in the 210F range they often see in hot weather, PCM pulls as much as 10* of that timing out.

Thanks fast4.7! I am making data logs and sending them to black bear. I tried to post pictures of the graphs but apparently the pic files were too big to upload. I can still upload the dot efi files, but it's irrelevant now until the new adjustment comes back.

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Originally Posted by Scott-m

Thanks fast4.7! I am making data logs and sending them to black bear. I tried to post pictures of the graphs but apparently the pic files were too big to upload. I can still upload the dot efi files, but it's irrelevant now until the new adjustment comes back.

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So you/they are tuning in EFI Live?

They are using efi live, and they loaned me a V2 data cable (with my cc of course). I email the logs and send the ecm up for adjustments. Here are a couple screenshots of the most recent tune. My phone takes pics that are too big to upload, so these are with my old cannon with permanent water marks on the lens. First one shows a half throttle run through the gears, no trace of knock with 28-30 deg timing. Second shows a wot run through 2nd and 3rd, with advance jumping to 33-34 and knock retard kicking in, especially in 3rd gear. Obviously more timing at wot than at half throttle is wrong, but it is my fault for asking for too much at wot.

I’m not sure that anyone is going to be able to do much with screen shots. But what is going on in the middle of the screens with o2 voltage (500 on time scale of first screen?

Right, I know no one here can help until I get the hp myself. Yeah they glitch out, often right after a wot run. And it's right when spart timing drops to zero too, if there is any connection. I don't know if it's really happening or not. There are glitches with the map numbers and afr too.

Scott,

I am also going off first hand experience tuning that engine in everything from a 26K motor home to a friends 99 K3500 dually towing a large travel trailer. If you are ever towing with it, hitch the trailer to it and datalog. You will run into detonation a bit earlier towing than you will running empty, especially on a hot day. I actually have 2 tunes for the 383 in my Express and can change tunes in about 60 seconds, I have a hot tune for running the van itself around town and long distance and a tune that required about 4-8* less advance under load for towing 8K. After you elimonate the detonation currently found in your tune, if you are going to tow anything long distance, hook up to the trailer, then datalog the truck for 30 minutes or more and head uphill with a hot engine to make sure it is not detonating when towing. The knock sensors and low octane timing table are meant to protect the engine but I loathe relying on that system to save a hard working engine. I tune the engine for the maximum load it will see and retain the knock detection and low octane spark stuff for a tank of bad gas or the like.

With the old TBI systems I had a couple of switching boards that held multiple EPROMs or Memcals depending on the year model and had a rotary dial on it in the dash board. I had about 4 different tunes for my L31 TPI 383 and 4L60E combination. One that was optimized for highway fuel mileage, one that was great for running around town that locked out overdrive, one that was optimized for power and another that was setup for towing as well as an anti-theft position that would not even start and run.

Thanks Fast. I do tow a trailer and in the AZ heat. The old black box in the 97 would kill power down to nothing in hot weather, like barely able to climb highway hills in second gear. My 1982 454 carb'd rv could pull my trailer better than the stock 97. I think the ecm was killing off power due to trans temp. But how would it cut power? By backing off timing? That would put a lot of unburned fuel into the exhaust. And coincidentally, I found a ton of burned wiring when I swapped engines and did the 0411 rewire. Everything within 6 inches of the exhaust was crispy. BB says the new tune will not do that. This pic is from June last year.

Anyway I'm suprised they want so little timing. Now I'm feeling stupid about demanding more from BB. I thought I read somewhere the 0411 can use multiple spark tables.