Timing Table

[Roadknee]

I'm missing something then. I assumed that 100% VE was each engines particular ability to move the maximum about of air volume for its given combination of parts. 100% being the most air that engine could pump regardless of the actual volume of air. If that's wrong please explain.

VE is the ratio of the amount of air an engine actually passes divided by its displacement. A 4-cycle engine fills and empties its cylinder(s) once every two revolutions. If a 350 CI engine passes 350 CI of air every two revolutions it is achieving 100% VE if it only passes 315 CI it is achieving 90% VE. 385 CI is 110% VE.

[steveo]

100% volumetric efficiency is an engine taking in its full cylinder's displacement of air each intake stroke.

it's very rare and very difficult to achieve. most engines dont exceed 100%. that studebaker engine with 114% VE is a pure race engine that is tuned to the max.

exceeding VE is an air velocity kind of thing. scavenging, valve timing, intake charge resonance, bunch of crazy stuff combined have to happen.

if you DO exceed 100% VE, unless it's a really hardcore engine, it's usually like 101% or 102%, and a 1-2% error in the VE table is probably no big deal anyway...?

[Roadknee]

and a 1-2% error in the VE table is probably no big deal anyway...?

Agreed. Certainly is not a big deal to me. I have a really good tune in my truck right now. I could double the cylinder displacement and half the VE tables and it would run the same. Both would be very wrong, but the engine would run the same. I could half the VE tables and the injector constant and the engine would run the same. Point here is I don't really care (nor does the engine) if those values are accurate or not. I am only concerned if in the end of its calculation the ECM determines the injector pulse width that delivers the correct amount of fuel to the engine.

[steveo]

also worthy of note that its going to be at -rediculously- high MAP and RPM that it happens. generally you're in power enrichment at that point anyway. since you have a fuel modifier that is multiplying against VE or whatever, you can just make up the difference there.

[brian617]

Now that I understand VE completely and that 100% VE is hard to achieve, anything over 100% is really hard to achieve, why are you cheating the table? It really seems no different to me than increasing fuel pressure, with out changing the VE table or am I still missing something?

[Roadknee]

also worthy of note that its going to be at -rediculously- high MAP and RPM that it happens. generally you're in power enrichment at that point anyway. since you have a fuel modifier that is multiplying against VE or whatever, you can just make up the difference there.

High MAP, yes, but peak VE occurs around peak torque rpm, not peak HP rpm. Agreed you can use the fuel modifier to deliver the necessary fuel; comes down to personal preference.

[Roadknee]

Now that I understand VE completely and that 100% VE is hard to achieve, anything over 100% is really hard to achieve, why are you cheating the table? It really seems no different to me than increasing fuel pressure, with out changing the VE table or am I still missing something?

Let's say we want 12.5:1 WOT AFR. Our injectors flow-tested 84 lb/hr at 22 psi. We're running 22 psi and set injector constant to 84. VE table is in good shape with BLM's mostly around 128. VE table values in many of the 90+ MAP cells are maxed out at 99 or 100 (note: this is not necessarily the true VE of the engine, but what we have extrapolated from lower cells with BLM data as what will be necessary to achieve stoich AFR). We set PE AFR to 12.5. We install a wideband and go for a WOT run and our AFR is, say, 13.2 instead of 12.5. We need more fuel. The VE table won't accept higher values. Four options are available to deliver the required fuel to the engine : (1) increase fuel pressure and retune VE tables, (2) decrease injector constant and VE table values by same percentage, (3) decrease target PE AFR to something less than 12.5, and (4) increase cylinder volume and decrease VE table values by the same percentage. What method you use to provide the engine the required fuel is a matter of personal preference.

[brian617]

Let's say we want 12.5:1 WOT AFR. Our injectors flow-tested 84 lb/hr at 22 psi. We're running 22 psi and set injector constant to 84. VE table is in good shape with BLM's mostly around 128. VE table values in many of the 90+ MAP cells are maxed out at 99 or 100 (note: this is not necessarily the true VE of the engine, but what we have extrapolated from lower cells with BLM data as what will be necessary to achieve stoich AFR). We set PE AFR to 12.5. We install a wideband and go for a WOT run and our AFR is, say, 13.2 instead of 12.5. We need more fuel. The VE table won't accept higher values. Four options are available to deliver the required fuel to the engine : (1) increase fuel pressure and retune VE tables, (2) decrease injector constant and VE table values by same percentage, (3) decrease target PE AFR to something less than 12.5, and (4) increase cylinder volume and decrease VE table values by the same percentage. What method you use to provide the engine the required fuel is a matter of personal preference.

If your VE table is maxed out and you cannot achieve commanded AFR then you have in affect miscalculated PPH or miscalculated your engines fuel requirement. When you change the injector constant you are as I said earlier robbing Peter to pay Paul. In my opinion increasing fuel pressure is the logical approach. At some point fudging injector constant will only help until your injectors go static. I noticed in Barry's log even after you changed the constant the DC% was still pretty high.

[BLG355]

Does the injector constant change anything with the AE vs TPS and AE vs MAP adjustments? I'm going to post my bin, if anyone wants to criticize it, please do! The only settings I have changes since I changed to the 7.4 TB has been the fuel table and the injector constant. Everything else before was working wonderful, or at least as wonderful as it can until I make a change and realize just how it wasn't as great as I thought it was lol. I've only been messing with tuning EFI for the past year, and it has only been on one vehicle. So I am open to all input from anyone who wants to offer any. I love learning and being around people who are great at teaching, one of the reasons I love this board.

BLG

[Roadknee]

Does the injector constant change anything with the AE vs TPS and AE vs MAP adjustments? I'm going to post my bin, if anyone wants to criticize it, please do! The only settings I have changes since I changed to the 7.4 TB has been the fuel table and the injector constant. Everything else before was working wonderful, or at least as wonderful as it can until I make a change and realize just how it wasn't as great as I thought it was lol. I've only been messing with tuning EFI for the past year, and it has only been on one vehicle. So I am open to all input from anyone who wants to offer any. I love learning and being around people who are great at teaching, one of the reasons I love this board.

BLG

It won't. those tables just add to the pulse width. I think your Bin looks really good, which isn't surprising given that Eaglemark originally set it up :) VE table could use some fine-tuning. Try to collect some high MAP (80-90 kpa) BLM data. You either have to find a long hill, or be willing to apply a little pressure to the brakes while going down the road.

I am really surprised the 454 TB doesn't need more TPS AE. I didn't see any major lean areas in the log after throttle tip-in.

What are the build specs for your trans? I ask because the shift pressure profiling in the Bin is all factory original, and the 1-2 shift of your trans looks pretty firm in the log.

[BLG355]

It won't. those tables just add to the pulse width. I think your Bin looks really good, which isn't surprising given that Eaglemark originally set it up :) VE table could use some fine-tuning. Try to collect some high MAP (80-90 kpa) BLM data. You either have to find a long hill, or be willing to apply a little pressure to the brakes while going down the road.

I am really surprised the 454 TB doesn't need more TPS AE. I didn't see any major lean areas in the log after throttle tip-in.

What are the build specs for your trans? I ask because the shift pressure profiling in the Bin is all factory original, and the 1-2 shift of your trans looks pretty firm in the log.

I actually have all the AE backed way off vs factory settings, even from where mark had them too. It would stumble when cold when hitting the throttle and between shifts, so I back the TPS AE off a little, lowered the AE vs TPS vs Temp and lowered the 20kpa amount. I messed with it a lot based on feel. If it felt good, I'd go a little more until it felt off again then back it up again.

The trans has some goodies in it. I upgraded to a 13 vane pump, stock was ten. The valve body has a trans-go shift kit and their modified separator plate, also installed the .500" boost valve in pump. I made dowels on the lathe to lock the 3-4 accumulator in place, all accumulator pistons replaced with aluminum ones. I used the Sonnax Smart Shell due to the fact that this has rear planetary bearing value, which that addresses. It has a new GM reverse input drum and I used the Red Eagle Wide Power Band, replaced all bushings, bearings, and seals. I also upgraded to the corvette servo. I am happy with it overall. It does have a 3-2 downshift issue, it seems to bind/slip or a second before kicking down. until I get time to dig into it, I avoid 3-2 downshifts or do it manually, which then it is fine. I recently (6 months ago) got a 454 from a 98 pickup, rod bearing bad, but he sold the good 4L80e 4wd trans with it for $300. I grabbed a TBI intake from a junk yard cause it was $15, not intending on using it, but I have it now. But the trans I want to swap the 4L60e out for the 4L80e, eventually. I see some people are doing the swap, until I get extra time or the 4L60e breaks again, I'm just going to keep running it.

BLG

[Fast355]

I noticed the same thing bringing in timing earlier on the Vortec head engines I have tuned.

All this mention of injector size vs VE tables has brought forth a personal opinon. It really does not matter where the pulsewidth comes from controlling the injectors as long as it holds the injectors at a reasonable duty cycle and the engine is getting the fuel it needs. I ended up lying the PCM in my Express van after adding in the 85mm MAF. With the smaller 3.5" MAF it would read closer to 300 GMS/SEC airflow. I also had VE tables that were reaching the 120-130% range. That much airflow put the cylinder air gms/cyl readings in the 0411 nearer the bottem of the scale, retarded the ignition timing and cause the 4L80E to turn into a race car transmission. When I swapped to the larger MAF I simply lied to the PCM that the injectors were smaller and then made tweaks to the MAF table to get the fueling where I wanted it. Works well for me, the MAF reads in the stock 200-240 gms/sec range and the VE table now tops out at 100-102% and the transmission shifts much more smoothly. Also on a side note the timing map I am running that I posted above is still working great. A newish 5.3 Tahoe that was dualed out was not having it when I was trying to pass him coming back from the shop last night while datalogging. I gave it WOT at about 75 mph, was passing him by the time I hit 3rd at 90 MPH and by the time I let off the throttle he was seeing nothing but Express van tailights. 27* of timing in the 5.7 pulling against a lock conveter in 3rd gear and ZERO knock.