[steelborn1]

When should you start changing your settings for load? Asked another way, do the stock setting do okay for most N/A motors? Compared to stock, I would consider my motor pretty heavily modified. The airflow potential of my intake, heads, cam and exhaust far exceed stock components. Would I benefit from changing this table or should I leave it alone until I need to rescale for boost? Just asking for my own knoweledge. I am curious. Thanks guys.

[cgrey8]

When you say rescale Load, you you mean Load%? I think most people here have come to the conclusion that setting the scalar to make Load = Load% is the simplist thing to do vs trying to scale Load% to make it equate to 100% at all WOT RPMs.

[steelborn1]

I have already set them equal. I was just wondering if there is a general ballpark of when you need to change the table? The stock 5.0 makes 225hp but if I am now making over 400hp does this table need to be 'tweaked'? Since it has to do with volumetric efficiency, which has been greatly improved on my engine, do I need to change it to reflect that or not?

[Frit]

Best way to determine that is to log LOAD. If your only 5% above stock I don't think it would be a big concern to adjust things, but if your running 15% above stock.. then I would say its time to start tweaking.

Just my thoughts.

Frit

[steelborn1]

That sounds reasonable. Thanks for the input!

[mikenstang]

For what it is worth, I just did my sealevel load today with ea and it made a big difference. I was at about 150% load (loadX not actutal load) on my logs with a N/A engine.

I have been fighting a detonation problem and kept lowering my timing in my tables but it never got much better, and I had signifigant loss of power from lowering the timing so much.

I now have stock J4j1 timing tables and much less detonation. I will do some more timing adjustments this weekend to finish it up.

[Frit]

Speaking of load, I'm curious why some people say load really doesn't matter if your peaking out at 200% at WOT

I know in the older strategies spark is controlled by RPM at WOT, but LOAD is still used to control AFR?

Frit

[BobCat]

On a mild NA HCI combo you have nothing to gain by scaling load as you will never come close to 100%.

[Cougar5.0]

When you say rescale Load, you you mean Load%? I think most people here have come to the conclusion that setting the scalar to make Load = Load% is the simplist thing to do vs trying to scale Load% to make it equate to 100% at all WOT RPMs.

Hmmm, looks like I need to get to writing the Load vs. Load% write up. Along with making high and low slopes equal, these are two lazy ways of doing things that actually create more work.

Making Load = Load% screws up when the engine goes open loop at high load and misaligns the base OL fuel table unnecessarily and you need to adjust it to realign it.

Making slopes equal is a sure fire way to create lean tip-in problems as there is no way to use the breakpoint to keep from oversquirting at idle. Then you adjust offsets to compensate and viola! lean-out at heavy off-idle tip-ins. I had to reshape the off idle MAF curve when I did my "equal slopes" experiment which is just the wrong way to do things.

[sailorbob]

Making Load = Load% screws up when the engine goes open loop at high load and misaligns the base OL fuel table unnecessarily and you need to adjust it to realign it.

I disagree. Since you almost always are having to adjust the tables' LOAD% scaling because you have a modified engine that is capable of greater VE than stock then why not adjust for having LOAD = LOAD% at the same time. It makes tuning far more simpler when you have your spark and fuel tables showing the same values.

[steelborn1]

Well, that clears that up.LOL. Here's my logic. An engine displacing 302ci would reach a VE of 100% when it is producing 302hp, correct? So, if my little 5.0 is pushing close to 400hp, then wouldn't actual VE be closer to 133%? I may be completely wrong on this but it makes sense to me. If I am better off leaving the table stock that is great. I just wanted to clarify whether or not to mess with it right now. Thanks for the good discussion.

[cgrey8]

Well, that clears that up.LOL. Here's my logic. An engine displacing 302ci would reach a VE of 100% when it is producing 302hp, correct? ...

No, not really. The HP production is not directly proportional to the VE. They are related in that as VE goes up, HP goes up. But they certainly can't be expected to be a 1-to-1 ratio. You are at 100% VE when the amount of air you aspirate into the motor every revolution is equal to 1/2 the displacement. So when you aspirate 151cubic inches of air into the motor every revolution, you've hit 100% volumetric efficiency on a 302cid motor. The only way you could aspirate more is to force more in with some kind of forced induction. But since it is very difficult to hit 100% naturally aspirated due to inefficiencies in the plumbing, about the only way to hit 100% VE is with a boosted application or at best some passive positive pressure system like a cowl hood or ram-air setup.

Cougar5.0, I experimented with the equal slope thing too and I found I could get some fairly good results by setting them equal but by also lowering the Injector Offset curve to compensate. It wasn't perfect, I have to admit. Also now that the GUFx defs are corrected to datalog InjPW correctly, EA is calculating my slopes/bp much more intelligently. I can now enter values very close to what EA calculates and get great results. Keeping the modified InjOffset curve from my equal-slope experiment, my EA calculated low slope is VERY close to my high slope. And since it's easier to tweak the low slope than it is to monkey around with the InjOffset table AND EA gives intelligent values for slope/bp, I have taken full circle back around to not using equal slopes anymore. Before I lowered the InjOffset curve for the equal-slope experiment, I had to run 50s and 60s for a low slope or my idle and decels were BAD rich.

[steelborn1]

I will argue a little here. Not too much though. I have seen many engines achieve more than 100% VE in N/A form. When I lived in the Charlotte area I had several friends with access to dyno facilities. I got to participate in all kinds of dyno testing. Most of the 4.6 Cobra N/A motors run 100-105% VE at higher rpm. A well matched H/C/I combo on a 5.0 could do the same thing. Key phrase, WELL MATCHED. I had my heads and intake ported together up there and they are very well matched. So, I believe I could be achieving this too.

[cgrey8]

I guess it's possible tuned-port intakes have enough force in the reverberation that they can create a positive pressure on the ports to get just above 100%. Or it could be just error in the MAF curve resulting in a calculated Load value greater than 100%.

Also remember, people that don't know the difference easily could've been datalogging Load%, not Load, which is quite easy to get above 100% on a NA motor especially since the intention of Load% is to be at 100% at all WOT conditions. Load% is the percentage estimate of the motor. So if the best the motor can do is 80% Load at say 4000RPMs, then you'd want Load% to indicate 100%@4000RPMs.

[steelborn1]

Ahhh....That is good info. So, I want my max load to be 100% at my max rpm of say 5500-6000rpm? Then 80% around 4000rpm and so on. So, would I want my max load to be around my max hp rpm? I might actually be learning something this time!

[cougarnut281]

Another thing about hitting over 100% VE is that you can be overscavenging and pulling the air right out the exhaust. This will show a VE of greater than 100% but your actual trapped VE in the cylinder may not be that high.

Also max VE always occurs at peak torque NOT peak horsepower.

[cgrey8]

Lets take a more detailed scenario. Lets say at low RPMs, Load is only 70%. Well at that RPM, you'd want to modify the Load-to-Load% function to make Load% = 100%. As RPMs increased, lets say Load increased to 80% at 3000RPMs. Then you'd want the Load-to-Load% function setup so that Load% = 100% there too. And so on all the way up. A perfect setup would have ANY WOT condition with Load% = 100%.

Now as this correlates over to a boosted application, lets say 3000RPM had Load = 120%. You'd want the Load-to-Load% function scaled so Load% indicated you were at 100%...same thing, just in this case Load is higher than Load%.

But as you hopefully see now, Load% should always indicate at what percent of the motor's capability you are at for the current RPM.

At least this is my understanding of it.

[cgrey8]

Another thing about hitting over 100% VE is that you can be overscavenging and pulling the air right out the exhaust. This will show a VE of greater than 100% but your actual trapped VE in the cylinder may not be that high.

Also max VE always occurs at peak torque NOT peak horsepower.

Exactly right on all accounts...

[steelborn1]

Thats right, I meant torque not hp. All good info. This thread has really helped my understanding of load. Thanks for all the feedback. So, my max load should be roughly at my peak torque rpm?

[Cougar5.0]

Making Load = Load% screws up when the engine goes open loop at high load and misaligns the base OL fuel table unnecessarily and you need to adjust it to realign it.

I disagree. Since you almost always are having to adjust the tables' LOAD% scaling because you have a modified engine that is capable of greater VE than stock then why not adjust for having LOAD = LOAD% at the same time. It makes tuning far more simpler when you have your spark and fuel tables showing the same values.

NO! The real advantage to the scaling is at low RPM where you have more table rows to work with - otherwise if you have an engine that can achieve 150% load, you are stuck with just a few rows for normal loads & OL driving - i.e. during warm up or lugging!!! I see no advantage to having closed loop spark and OL fuel showing the same loads and I see no advantage to messing with the low RPM drivabilty more than necessary.

[steelborn1]

That makes it crystal Chris. I see what you mean about load & load % not always being equal. Thanks for the explanation.

[Cougar5.0]

Making Load = Load% screws up when the engine goes open loop at high load and misaligns the base OL fuel table unnecessarily and you need to adjust it to realign it.

I disagree. Since you almost always are having to adjust the tables' LOAD% scaling because you have a modified engine that is capable of greater VE than stock then why not adjust for having LOAD = LOAD% at the same time. It makes tuning far more simpler when you have your spark and fuel tables showing the same values.

Here's an example how changing the load switch can get you in trouble:

Load = 73%, ECT = 180F, 2000RPM lugging up a hill.

Stock Ford tune you are at 100% Load% and you go open loop as you are greater than 78% in FN320A. FN1307 (OL Fuel) will force AFR of about 12:1.

Now you change the load switch.

Load = Load% = 73%. You do NOT go open loop (<78% in FN320A) and bog and pop as ECU tries to stay closed loop. You can change the FN320A, but then you will still hit a different row in FN1307 which will be closer to 13:1 AFR. This may be OK, but there are conditions where you will go open loop and yet still be @ 14.64:1 (example - 57% Load = 78% load percent = O/L & 12.5 AFR, BUT if you change load switch and lower FN320A to 57% for O/L you now get 14.64 commanded AFR !!). You can adjust the table scaling or individual cells, but you will never be able to get back the advantage that a "normalizing" function gives you. Nobody will understand this so just keep screwing up your low RPM heavy load and complain about lean bogs - see if I care.

[sailorbob]

The real advantage to the scaling is at low RPM where you have more table rows to work with - otherwise if you have an engine that can achieve 150% load, you are stuck with just a few rows for normal loads & OL driving - i.e. during warm up or lugging!!!

This is not what is happening when you tune with LOAD = LOAD%. You can still bias your tables towards low loads and rpms for drivability. Just because the rows are now displaying the actual LOAD instead of LOAD% does not mean that you have lost any resolution. All FN035 is doing is rescaling LOAD to give a percentage of the maximum LOAD the engine is capable of for a given rpm. Let us say that FN035 did not exist and the fuel tables used LOAD / 2 for their row axis, this does not mean that the fuel table has lost or gained resolution, it just means you are simply seeing half the value of LOAD displayed. Only by changing the number of rows or columns in a table can you affect its resolution.

I see no advantage to having closed loop spark and OL fuel showing the same loads

We will have to agree to disagree here, it also means there is one less thing to datalog.

I see no advantage to messing with the low RPM drivabilty more than necessary.

As above, this is not happening.

[Cougar5.0]

Re-read my post just above yours - you do not understand a "normalizing" function and how you are losing resolution by removing it.

[sailorbob]

Re-read my post just above yours - you do not understand a "normalizing" function and how you are losing resolution by removing it.

Yes I do and you are not losing resolution. You are assuming that people will not make adjustments to parameters that use LOAD% after changing PRLDSW.

[Cougar5.0]

Think about it - it's actually more work to try to re-align the commanded AFR and O/L load levels after changing the load switch. Think about how this table (FN1307 - OL Fuel) is used during warm up. There is a reason that Ford engineers spent a lot of time and code space to implement this function.

[BobCat]

I"ve tuned 30 or more NA Cobras and I've never had a bolt on or even cam equipped NA 4V go over 100% load so I'm not sure what you are talking about.

Also the arbitrary 400hp number you keep quoting is off by a substantial amount for your combo.

To date i've never used Load % on any NA combo.....I'm not saying there wont be a case where it's necessary but I've yet to see any gains by doing so.

[cgrey8]

I'm not forced induction, but I retasked my Base OL table to rich values for a similar reason. I think the leanest value in the table is something like 14.18 and that's around 40% load. All other locations are much richer than they would be naturally aspirated. But the only time my engine ever see's OL cruising loads is during warmup, which I've shortened from 100 seconds to 32. From what I understand, that's not a realistic expectation for most engines, but mine seems to handle going CL after 30 seconds of crank just fine. So I set the Base OL table to never give me lean conditions and tweaked the Fuel Startup table accordingly to not over-enrich during startup.

I'm not denying that the normalized Load% has it's benefits for granularity at the lower RPM/Loads. And I'd also agree that the majority of the benefit of it is for driveability at the lower end. I think I see the resolution thing Cougar5.0 is talking about. At lower RPMs, a boosted engine's maximum load may be like 90% load, which resolves to 100% Load% (when setup right) and thus all rows of the fuel table can be used. However at 4000RPMs, the Load may be 150%, but the Load% only ranges to 100%. So that same 0-100% range that Load% represents is stretched which means each line of the Fuel table represents a wider Load range and thus less resolution in this area but tends not to matter in this RPM range...but the table resolution is preserved in the lower RPMs where Load doesn't go quite so high.

Contrast that with a setup where Load = Load%, now the tuner has to retask the Fuel table all the way up to 150% so at the lower RPMs, you basically have wasted cells on the table representing Loads the engine can't attain...hence the lost resolution Cougar5.0 is referring to that the normalized Load% can make use of. Cougar5.0, do I have that right?

But the concept of it is so difficult for most people to wrap their mind around, that I think most people just find other ways to handle the problems they may have at those lower RPMs.

[Cougar5.0]

Chris, yes - you have stated it about right. The "normalizing" function allows all of the 80 cells in FN1307 to be used at all RPMs & ECTs. Imagine that you are WOT off idle and you have changed the load switch, your AFR will follow the cells up and down the top 3 rows as load varies from 70% to 90% back to maybe 80% @ redline.

[Frit]

Don't seem to have a resolution problem with the SC's, and those are set to 1 at the factory so LOAD=LOAD% all the time.

It can't be all that bad to run that way, especially with forced induction, otherwise the factory wouldn't have used it.

Frit