2008 E38 Speed Density Tune for E85, Supercharged 950 rwhp LS3 Corvette....lean sp

[mowton]

This is a followup to a previous question on E38 Speed Density tuning and transient fuel tables. Have tried pretty much everything in the Impact/EVAP as well as stomp and airflow but just can't seem to cure the PE activation and the WOT shift lean events. I have found that the Impact table can be used to richen up the fueling, but unfortunately it appears to ocurr after the lean spot (see attached log).

I am looking for any idea's or lessons learned that anyone has relative to MAFLESS, SD tuning on the E38 PCM using a manual transmission.

Thanks and I look forward to idea's, discussion or even just a well wish.

1351313514

[swingtan]

Looking at that log, I see no "significant" lean spikes. Can you list the log frame range that your are trying to deal with?

FWIW, Dynamics won't really change PE activation, you may want to rethink how you are controlling PE mode. It looks like you are using pretty stock settings for PE activation, which I've never been a fan of. Just for a test, try the following....

{B0157} set to 75kPA
{B0156} set all to 2%

PE mode is set by a number of "enablers" all of which must be met before PE mode activates. In the stock tune, the MAP setting is pretty much always set (15kPA) but the TPS ( throttle position ), prevents PE activation till a very high throttle opening. in the tune above, it's set to 19% in the tune which relates to about 52% actual throttle opening as logged with the ETCTP PID. So anything under 50% throttle and you will never, ever have PE mode activating, even if the engine load sees the MAP go to 185kPA.

Changing the PE mode enables to have the MAP set at 75kPA and the TPS set to 2% ( about 19% on ETCTP ) means that PE mode will activate as soon as the engine load sees the MAP go over 75kPA and there's more than 20% throttle.

I've posted about this before and not every one agrees with me, but tuning a manual is not the same as tuning an auto. The dynamics play much more importance in the manual, as you've found, especially between gears.

Oh, and what's with the messed up VVE ? it doesn't look like it's been dialed in very well with the dip at 95kPA.

Also, is it running a boost referenced fuel pressure regulator? The more I look at the tune, the more questions about the cars setup I have.

Finally, what's the go with the spark tables?

Simon.

[mowton]

Looking at that log, I see no "significant" lean spikes. Can you list the log frame range that your are trying to deal with?

FWIW, Dynamics won't really change PE activation, you may want to rethink how you are controlling PE mode. It looks like you are using pretty stock settings for PE activation, which I've never been a fan of. Just for a test, try the following....

{B0157} set to 75kPA
{B0156} set all to 2%

PE mode is set by a number of "enablers" all of which must be met before PE mode activates. In the stock tune, the MAP setting is pretty much always set (15kPA) but the TPS ( throttle position ), prevents PE activation till a very high throttle opening. in the tune above, it's set to 19% in the tune which relates to about 52% actual throttle opening as logged with the ETCTP PID. So anything under 50% throttle and you will never, ever have PE mode activating, even if the engine load sees the MAP go to 185kPA.

Changing the PE mode enables to have the MAP set at 75kPA and the TPS set to 2% ( about 19% on ETCTP ) means that PE mode will activate as soon as the engine load sees the MAP go over 75kPA and there's more than 20% throttle.

I've posted about this before and not every one agrees with me, but tuning a manual is not the same as tuning an auto. The dynamics play much more importance in the manual, as you've found, especially between gears.

Oh, and what's with the messed up VVE ? it doesn't look like it's been dialed in very well with the dip at 95kPA.

Also, is it running a boost referenced fuel pressure regulator? The more I look at the tune, the more questions about the cars setup I have.

Finally, what's the go with the spark tables?

Simon.

Simon, thank you for your response. By reading and learning from too many threads to count on this forum over the years, I have learned you are one of the more knowlegable and greatly respect your skills and insight.

The car is setup with a custom high flow fuel system (non-referenced and has been checked over all loads) and set to the stock 58 PSI. The injectors are from FIC (127 lb/hr) and the tune has been scaled by 60%. The VVE has been established through some preliminary Dyno and street work, but has not been fully developed over the entire 2.5 Bar area's. Same basically for the timing table, which I scalled, but in relooking I see the table some how got reloaded back to unscaled version so I need to get that straightened out on Monday :mad: . Will finish both once we get this lean condition straightened out. The car is putting out about 18 pounds of boost in the current setup.

Understand about the PE entry and will give that a shot this week.

As far as the log, my bad, I posted the wrong log.....sorry. Attached is the correct log. starting at 13:08:37 is the entry into PE during the 3rd gear pull and then the shift lean event to fourth. I only address the PE because it seems whenever there is a need for additional fueling, the AFR goes lean for 300-400 ms dependant entirely on the magnatude of the delta change. I see the same situation as I cruise at one TPS % and then press and hold to 20% greater. This from what I have learned tuning LS1 PCM setups is correctable in the Transient fuel tables.

Again, I appreciate your insight to this and look forward to any ideas or sugesstions you have.

13515

Ed M

Update -- This actually is the starting timing table that should be in the tune -- 13516

[swingtan]

LOL!!

Have a think about this......


In a manual, the ECM will set a gear selection of "Neutral" when you press the clutch in. ( it's used for DFCO as well as a number of other things ).

You have set the rev limiter control to cut fuel when an over rev occurs.

You have set the rev limiter in Neutral to 3500 RPM.



Look up, do you see a light bulb floating above your head?

I'd do the following...


{B5205} = no
{B5206} = no
{B5207} = Yes
{B5201} = Set all about 100 RPM below your desired "peak" RPM


If you want to "fine tune" the limiter, set a lower than desired RPM limit and use {B5208} to get the ECM to react fast enough to stop an over rev. Once done, reset {B5201} to your desired RPM limits.


Simon

[mowton]

LOL!!

Have a think about this......


In a manual, the ECM will set a gear selection of "Neutral" when you press the clutch in. ( it's used for DFCO as well as a number of other things ).

You have set the rev limiter control to cut fuel when an over rev occurs.

You have set the rev limiter in Neutral to 3500 RPM.



Look up, do you see a light bulb floating above your head?

I'd do the following...


{B5205} = no
{B5206} = no
{B5207} = Yes
{B5201} = Set all about 100 RPM below your desired "peak" RPM


If you want to "fine tune" the limiter, set a lower than desired RPM limit and use {B5208} to get the ECM to react fast enough to stop an over rev. Once done, reset {B5201} to your desired RPM limits.


Simon

Simon,

Interesting approach (including the PE) for sure. Will give it a shot tomorrow. Way to think out of the box :good: Safer solution to power shifting (or an automatic) as I have read is a way to counter this phenominum. Thanks again for your time and patience.

Ed M

[mowton]

Heat, rain and priorities have prevented us from getting any real data on these changes, but based on feel, this seems to have reduced greatly the "flat spot" during wide open shifts. I have a question though on the change from Fuel to ETC interaction for rev limiting. While in neutral (clutch-in) I see no problem, what about for in gear events. Will the protection be the same as with fuel cut-off?

Thanks and will post the detail info as soon as we can get the car back out.

Thanks

Ed M

[swingtan]

I only use throttle control for the rev limiter. My view is....


Cutting fuel at peak RPM and WOT results in a massive lean out condition where you really don't want it. Peak RPM lean outs are what we try and avoid as they damage the motor. Now remember you're running boost, so why on earth would you want to cut fuel when you are at full song and up on boost?
Sure, you could use a fuel cut combined with spark cut to try and save the motor from a massive lean out. But the rapid change in timing will probably result in backfires in the exhaust, possibly damaging cats and or mufflers. Not to mention O2 sensors.
The ETC is very fast. When I was playing with the "valet mode" a few years ago, it was like hitting a wall when you hit the speed limiter at WOT. It's fast enough to be used as a shift rev limiter.
Fuel and spark cut was fine for cable throttles, it's not really needed with ETC as you can close the throttle.


All that being said, the fastest shifts I've done in my manual, were done with the throttle rev limiter and CFCO enabled. With a fair bit of work, I was able to near flat shift without significant over revving. But normal driving was harsh and felt abrupt, ETC as the rev limiter is perfectly safe, providing you "tune" the limiter to close the throttle enough before you over rev the motor.

Simon.

[mowton]

13555

Simon,

Your changes significantly increased the relationship between the APP% and the ETCTP% which has greatly improved the response between shifts. The attached log shows that improvement from the previous log. We logged (18:38:59) with an LM2 that was set to 14.2 AFR so the BEN error isn't accurate (Stoich in tune is 9.85) but we still have the large lean event? Will continue to play this week and again thanks for all your help.

Ed M

[swingtan]

OK, that's great news. That last bit of a lean spot could be a number of things, but given the shape of the VVE, I'm going to guess the injector data is just plain wrong.

The 127lb/Hr injectors will flow 16gm/Sec at 4bar (58PSI). I went looking for the rest of the injector data but the FIC web site is pretty bad when it comes to finding specific data. Even the flow rate stuff I got from LS1Tech!

Anyway, the flow rate of 16gm/Sec is at an injector pressure delta of 4bar or let's say 400 kPA. Your tune has the flow rate set to 6.325gm/Sec at that point, which is pretty close to 40% of the actual flow. Assuming you are working on a scale factor of "reducing the VVE by 60%", then it's close to correct.

What we don't have is the flow characteristics for any other delta pressures. As you don't run a boost referenced fuel pressure regulator, the injector delta pressure will change all the time, requiring accurate data to get the fueling right. This would normally only be available from the manufacturer, or if you flow benched the injectors to see what the change in flow rate was. Looking at the log data, you get up to 200kPA on the MAP, so the injector delta is going to be only 200kPA, not 400kPA. If things were perfect, then you might see a corresponding 50% drop in flow to match the 50% drop in delta pressure, but it's probably not going to work like that. in a similar fashion, on over run you have a MAP of 20kPA, so the injector delta is going to rise to 480 kpa or a 20% increase with a corresponding rise in flow rate. But again, we don;t have the real data (at least I don't......)

I'm going through all this because the ECM is commanding a very low injector pulse width during gear changes. The one big lean spike shows an IBPW of just over 2mS, something I'd normally expect to see at idle. So you need to work out why you have such a low IBPW during the shifts. As mentioned, I think it could be the injector data.

Simon