99 L29 454 build

[Supercharged111]

I'm on something like the 8th trip back up to the tuner. Besides still pinging at wot, it audibly and steadily pings at hway speed 55-65 climbing slight hills, when rolling into the throttle in 3rd and 4th gear, and at 30-40% throttle accelerating through the gears. So I asked them to reduce wot timing again, and make the cruise timing back off more effectively as map pressure goes up (Vac goes down), like conventional distributors have done pretty well for 80 years now.

This is the reply I got:

"MAP doesn't dictate timing on that platform, it is based on air density largely determined by MAF. The MAPxRPMxIAT calculation is largely just a sanity check against the MAF."

Does that sound right to you guys? Isn't map and manifold density essentially the same thing? I have trouble believing the powerful 0411 can NOT adjust timing based on manifold pressure/vacuum..

The 411 manages timing exactly as the response was worded. It's different than the blackbox which uses MAP, but it's a better way to do it. It takes some getting used to when tuning.

 

[L31MaxExpress]

The 0411/P59 both base timing off cylinder air charge in the same manner the older GM MAF systems used the LV8 value calculated from the MAF. It truly is a better way to do it.

Best suggestion I have is to use a stock 8100 tming maps. The one 7.4L I have tuned with an 0411 ran very well with it.

 

[BNielsen]

I think my 0411 has some 8.1L values and it ran pretty decent when it wasn't having so many issues; it's been so long since I've tinkered with it I can't remember the values and I can't find the tables on my new computer; I think @Mangonesailor and @Christian Steffen have copies of the current tune that's in my truck?

 

[Scottm]

Ok thanks. That's great as long as it can do the obvious, which is reduce timing as engine load and cylinder pressure goes up. I trust they will get it right this time. If not, can I send it to you L31?

I just thought of something. The egr is turned off in the tune. Could they be forgetting to compensate for that?

 

[L31MaxExpress]

Ok thanks. That's great as long as it can do the obvious, which is reduce timing as engine load and cylinder pressure goes up. I trust they will get it right this time. If not, can I send it to you L31?

I just thought of something. The egr is turned off in the tune. Could they be forgetting to compensate for that?

I can tune one. If the EGR is turned off there is nothing to compensate for although I do zero out the EGR tables.

 

[Mangonesailor]

Ok thanks. That's great as long as it can do the obvious, which is reduce timing as engine load and cylinder pressure goes up. I trust they will get it right this time. If not, can I send it to you L31?

I just thought of something. The egr is turned off in the tune. Could they be forgetting to compensate for that?

I find my truck as a lot of spark knock detected when it's hot, which just simply can be automatically compensated against based off of IAT readings. It's all that heat soak by that giant aluminum intake of ours.

It truly is difficult to make good power. I tried for a long long time to get a timing table worth a damn without PE that wouldn't spark knock like crazy, then I had to chase playing with timing as the fuel enrichment increased, then IAT and how it influenced it after punching it after being stopped. It was constantly something.

However I have a theory that some of my issue is the sensitivity of the 7.4 knock sensors is different and simply swapping in 8.1 knock sensor(s) would assist with this. I don't have audible ping, so I have desensitized them slightly, but after that change I have focused more on timing adjustment. Seriously if you look as some of my logs and changes you'd see a huge pit develop and I think it looks like hot garbage compared to most, but that out gets filled depending on what my fuel and intake is at.

Now, quick note, that whole MAPxRPMxIAT arrangement is "Speed density." That's what you wind up running with as a secondary method if the MAF fails. The MAF tells the engine how many grams per cylinder of air you have and with every charge of air it proportions out the fuel. That's verified by your O2 sensors. You have to tune the VE table (based off speed density) to get a good base... then you tune the MAF. Once those are done then typically you adjust the MAF as needed if you need to trim your AFR richer or leaner in PE mode. If your MAF fails then typically you're going to stop goofing around and you'll just run normal. Some folks like/need to use speed density when using forced induction. But anyway it think it is use MAF calc, fuel, check, adjust STFT, use MAF calc, fuel, check, check against MAP, STFT, and then it repeats. Eventually you'll wind up for a LTFT that will be referenced. Once you unplug an O2 sensor then you wind up on just the VE map anyway.

Newer versions of HP tuners won't let you turn off certain things (like EGR) unless you take an off-road only course thing through them (it's free though and online). I have an older version, so I can just click it on/off at will.

 

[Supercharged111]

I find my truck as a lot of spark knock detected when it's hot, which just simply can be automatically compensated against based off of IAT readings. It's all that heat soak by that giant aluminum intake of ours.

It truly is difficult to make good power. I tried for a long long time to get a timing table worth a damn without PE that wouldn't spark knock like crazy, then I had to chase playing with timing as the fuel enrichment increased, then IAT and how it influenced it after punching it after being stopped. It was constantly something.

However I have a theory that some of my issue is the sensitivity of the 7.4 knock sensors is different and simply swapping in 8.1 knock sensor(s) would assist with this. I don't have audible ping, so I have desensitized them slightly, but after that change I have focused more on timing adjustment. Seriously if you look as some of my logs and changes you'd see a huge pit develop and I think it looks like hot garbage compared to most, but that out gets filled depending on what my fuel and intake is at.

Now, quick note, that whole MAPxRPMxIAT arrangement is "Speed density." That's what you wind up running with as a secondary method if the MAF fails. The MAF tells the engine how many grams per cylinder of air you have and with every charge of air it proportions out the fuel. That's verified by your O2 sensors. You have to tune the VE table (based off speed density) to get a good base... then you tune the MAF. Once those are done then typically you adjust the MAF as needed if you need to trim your AFR richer or leaner in PE mode. If your MAF fails then typically you're going to stop goofing around and you'll just run normal. Some folks like/need to use speed density when using forced induction. But anyway it think it is use MAF calc, fuel, check, adjust STFT, use MAF calc, fuel, check, check against MAP, STFT, and then it repeats. Eventually you'll wind up for a LTFT that will be referenced. Once you unplug an O2 sensor then you wind up on just the VE map anyway.

Newer versions of HP tuners won't let you turn off certain things (like EGR) unless you take an off-road only course thing through them (it's free though and online). I have an older version, so I can just click it on/off at will.

Unplug an O2 and you're open loop, not speed density.

 

[Scottm]

I find my truck as a lot of spark knock detected when it's hot, which just simply can be automatically compensated against based off of IAT readings. It's all that heat soak by that giant aluminum intake of ours.

Thanks Mang! (See what I did there?)

That is so true about the intake. Go back to post 44 of this thread, where I drilled the manifold and put a thermocouple probe into the number 2 cylinder runner. Air going into the head was at the full temperature of the engine, 190+. More throttle didn't help either, as egr would heat the cooler air back up.

 

[Supercharged111]

Thanks Mang! (See what I did there?)

That is so true about the intake. Go back to post 44 of this thread, where I drilled the manifold and put a thermocouple probe into the number 2 cylinder runner. Air going into the head was at the full temperature of the engine, 190+. More throttle didn't help either, as egr would heat the cooler air back up.

I don't know to what extent, but theoretically the air under vacuum should be cooler than the air in front of the TB as it's dropping in pressure.

 

[BeXtreme]

I don't know to what extent, but theoretically the air under vacuum should be cooler than the air in front of the TB as it's dropping in pressure.

No, that's not how that works. You can see from the data that the Temperature isn't even remaining constant, you are actually pumping heat into the air the entire way into the cylinder. Also, technically pressure isn't dropping. You are actually increasing the pressure in the manifold from idle to full throttle. At no point is the pressure in the manifold less than the pressure in the ambient atmosphere, so you are technically taking air at a set pressure and volume(atmospheric) and dropping the pressure while raising the temperature. n and R are also constant because you aren't adding fuel or changing the gas composition, so the only thing that can happen to make it balance out is for the volume to increase.

This whole thing has actually got me thinking about a manifold based intercooler like they have been running on the supercharged LS motors. I wonder how rough it would be to modify one to go in between the upper and lower manifold and what the actual effect on drivability would be... maybe a fun experiment for the future, since I have plenty of room in the squarebody for it.