LS4 / F40 swap - fieroguru (Page 82/216)
Trinten JUN 01, 02:20 PM
Is there not a load-based dyno shop anywhere near you that might let you do a couple cheap pulls/cruises to log data? (just last weekend I learned the difference of load-based/"brake operated" dynos and the "common" dynos. Had no idea such differences existed!)
Kemp3 JUN 01, 02:59 PM

quote
Originally posted by fieroguru:

Last night I took a more detailed look into the EOIT values to find the best offset to use at idle. My car already runs open loop at idle, so after the car was up to temp, I let it idle for 3.5 minutes per offset value while logging the data. I did this for 20, 30, 35, 40, 45, 50, 55, 60, 100 and 150 degree delay in injector timing just to see the trend and to find the ideal offset value at idle.

I was supposed to have seen the A/F ratio go rich on the wideband as the injector timing became more beneficial, but the max/min of the entire range was 15.49 to 15.93. Without any injector offset, I was at 15.51, at 20 it dipped to 15.49, but from there on it was a small but constant increase to the lean side. There is only about 3% difference between the max/min, so I started to look at some of the other data I logged.

Delivered Torque is a calculated number from several sensors/inputs/calculations (air flow, fuel, ignition timing, etc). When I compared these values, the min was 31.41 (at zero offset) and it peaked at 34.83 @ 55 degrees of offset, then gradually decreased to 34.24 at 100 and 33.09 at 150 This shows a 10.8% increase in calculated delivered torque at the 55 degree setting. So that is where I have decided to set the offset at idle.

Finding the ideal offset values for the rest of the RPM range (idle to 4100 RPM) is difficult w/o a load based dyno. So to get something "closer" I looked at the LS7 tables as that is the highest revving factory LS(x) based engine and I figure GM did their work to find the ideal values for it (especially since they are actually using the RPM based table - LS4/LS2 have no RPM based offsets used). At idle the LS7 injector offset is 32.5 (vs. stock LS4) and gradually increases to 93 at 4100 RPM. So for my table, I started with 55, then used a similar gain rate as the LS7 to end up with 112.5 offset at 4100. My starting offset is 22.5 higher (more aggressive camshaft) and the ending offset is 19.5 higher... this should be better than no RPM based gain and should be in a beneficial range w/o going too far. Time will tell.

The downside to making this adjustment, is it requires going back and retuning the MAF/VE tables slightly, but if it helps with MPG and low rpm torque, then it will be worth it.




Your description on idle EOI tuning makes me wonder, does the GM computer have some type of ego correction ? Is there something trying to always hold a set AFR ? If so it sounds as if that needs to be disabled for the test.

fieroguru JUN 01, 03:59 PM

quote
Originally posted by Trinten:
Is there not a load-based dyno shop anywhere near you that might let you do a couple cheap pulls/cruises to log data? (just last weekend I learned the difference of load-based/"brake operated" dynos and the "common" dynos. Had no idea such differences existed!)



There is a dynojet drum dyno about 30 miles away that costs 100 for the 1st hour and 5 pulls, then $75/hr and unlimited pulls after that. But it isn't the load based one that would be handy. In reality it isn't that big of an issue or worth spending a $100+ to get perfect. Maybe if I get DoD working, I will come back and revisit it on a dyno. If I don't get DoD working, I will probably upgrade to another camshaft.



quote
Originally posted by Kemp3:
Your description on idle EOI tuning makes me wonder, does the GM computer have some type of ego correction ? Is there something trying to always hold a set AFR ? If so it sounds as if that needs to be disabled for the test.



It has short/long term fuel trims that will adjust the fueling, but I have those disabled below 1000 rpm, so there is no a/f correction going on. My guess is the issue is I am running 100% MAF, not SD so if I put more air into the engine, more fuel is automatically added... I think this is the cause, which is why I looked at delivered torque (and cylinder airmass) to find the most benefit. For grins when I get more time I will switch over to SD and do the tests again to see if both methods key in on the same offset value.

Rest of the afternoon I am welding up a couple sets of lateral link relocation brackets.

[This message has been edited by fieroguru (edited 06-01-2013).]

F355spider JUN 02, 11:19 AM

quote
Originally posted by fieroguru:


It has short/long term fuel trims that will adjust the fueling, but I have those disabled below 1000 rpm, so there is no a/f correction going on. My guess is the issue is I am running 100% MAF, not SD so if I put more air into the engine, more fuel is automatically added... I think this is the cause, which is why I looked at delivered torque (and cylinder airmass) to find the most benefit. For grins when I get more time I will switch over to SD and do the tests again to see if both methods key in on the same offset value.

Rest of the afternoon I am welding up a couple sets of lateral link relocation brackets.



Is that for a dyno tune? I was qouted like 400 to 500 here.
fieroguru JUN 02, 11:50 AM

quote
Originally posted by F355spider:

Is that for a dyno tune? I was qouted like 400 to 500 here.



That is just to use the dyno. They are not setup to do any EFI tuning as they cater to the hotrods, race cars, and pulling truck (carb) market, but they are close.
I am responsible for doing all tuning. When I tuned my SBC/Getrag swap, I did 18 pulls/tune tweaks in 2 hrs for $175. With the wideband in the LS4/F40 I should have almost everything dialed in before I take it to the dyno so the initial 5 pulls should be OK.

Kemp3 JUN 02, 12:16 PM
I am curious how does the GM computer deal with a overrun fuel cut. what parameters have to be met before that event occurs ? I was using ORFC but seems like my motor doesn't really like it, may just be that I need to finish breaking the motor in as it sat for 3 years and had 1500 miles on it.

If you have access to a Load dyno that would be best, the inertia dyno lets you safely tune WOT so its better than nothing. I am in the same boat unfortunately ..... Load dyno 4-5 hours away . An inertia dyno 30 mins away just the operator is a flake :/

[This message has been edited by Kemp3 (edited 06-02-2013).]

fieroguru JUN 02, 02:40 PM

quote
Originally posted by Kemp3:

I am curious how does the GM computer deal with a overrun fuel cut. what parameters have to be met before that event occurs ? I was using ORFC but seems like my motor doesn't really like it, may just be that I need to finish breaking the motor in as it sat for 3 years and had 1500 miles on it.




The E67 ECM can limit maximum engine RPM via Fuel, Spark, or ETC (electronic throttle control). Each one has an enable/disable option. The main parameter you set is the RPM for Extreme Cutoff and Extreme Resume. There are not any tables to dial in how quick or slow it tries to limit RPM, like % fuel reduction for RPM beyond limit, or spark reduction... or at least I haven't found them. For the auto guys there is also the ability to have different rev limit for each individual transmission gear, but they all have to be at or lower than the Extreme Cutoff value.

Mine is set for ETC so the ecm will just close the throttle blade to avoid overrun, but to be honest I haven't hit it yet (mine is set at 7000 rpm), so I do not know how smoothly the ETC method works. I need to upgrade to a better tach that is scaled out to 7500 rpm and accurate... Every time I take it about 1/2" past the 6500 mark on the tack I end up short and only reaching 6800ish RPM and the laptop is too far away and in the wrong direction to watch it during a WOT run.

F355spider JUN 02, 03:56 PM

quote
Originally posted by fieroguru:


That is just to use the dyno. They are not setup to do any EFI tuning as they cater to the hotrods, race cars, and pulling truck (carb) market, but they are close.
I am responsible for doing all tuning. When I tuned my SBC/Getrag swap, I did 18 pulls/tune tweaks in 2 hrs for $175. With the wideband in the LS4/F40 I should have almost everything dialed in before I take it to the dyno so the initial 5 pulls should be OK.



Gotcha, I was worried they were trying to shaft me.
dobey JUN 03, 12:02 PM

quote
Originally posted by fieroguru:
Mine is set for ETC so the ecm will just close the throttle blade to avoid overrun, but to be honest I haven't hit it yet (mine is set at 7000 rpm), so I do not know how smoothly the ETC method works. I need to upgrade to a better tach that is scaled out to 7500 rpm and accurate... Every time I take it about 1/2" past the 6500 mark on the tack I end up short and only reaching 6800ish RPM and the laptop is too far away and in the wrong direction to watch it during a WOT run.



I'm not sure exactly which method the Cruze 1.4 turbo setup uses, but I do know that when you hit that RPM the cutoff is abrupt. I hit it a few times when I had the Cruze Eco, and every time it felt like I had just hit something. Not a good feeling, but it does kind of force you to lift off the gas and shift. :P
Kemp3 JUN 08, 02:23 PM
I am sorry I used terminology from my ecm, for a GM ECM I believe they call it Decel Fuel Cut (DFC) . Off throttle coasting in gear

Is that something that you are using ? that is what I am curious about in terms how GM implements it.