The Alchemist
March 31st, 2012, 01:31 PM
Hi people, been busy getting a demo car ready for our local Holden Dealer. A brand new L77 VE V8 2012 Auto trans.
Mods to engine include AFM Delete kit the big Texas Speed LS3 camshaft, FAST intake manifold, supporting Valvetrain mods, Airspeed OTR Mafless, the large X-force full exhaust twin 3 inch.
In an effort to produce a car with drivibility near to standard yet have a good cold start, good cold running, excellant "car park" manners, good fuel economy, good overrun characteristics etc I've been spending more time road tuning than I have dyno tuning :)
I would like to share a few "discoveries" I've made and a few questions to ponder and perhaps get a few answers back.
Info on these settings in the thread title has been hard to find in the E38 section. Some of you may already know the information below some may not.
Point 1:
I have found that "desired coastdown speed" appears to be the same as the desired idle speed in gear. Important to know to be able to set coastdown spark table, coastdown high and low spark tables and most importantly Minimum Idle Airflow which is essentially minimum blade angle on initial throttle pedal return.
Point 2:
The e38 is very clever in its idle and coastdown strategies and easily learns between a maximum and a minimum blade angle. As long as there is a broad enough range the targets can be met. Observation on overrun of ETC TP , RPM and spark from 100km/hr in 6th gear down to 6km/hr in 1st gear had allowed me to first dial in the minimum idle airflow table. The idea seems to be to get the rpm to return to as close to target idle rpm as you can. If its too high the spark will show this by learning down as far as it can set by Coastdown spark table high. But only when NOT in DCFO. So in 6th and 5th gear I've gone for about 1200rpm coasting in DCFO and -5 degrees. Set this rpm by simply reducing minimum idle airflow in 6th gear until you reach the rpm that feels right to you the driver. Reduce by 1g/s lots until you get close then by 0.5g/s after that. You will see the ETC TP getting smaller on overrun each time.
Point 3:
In 4th, 3rd, 2nd & 1st gears you dial it in via your idle RPM target watching spark learning. If spark's lower the the desired spark in the coast down table you need to keep lowering minimum idle airflow in the appropriate gear until you see the spark learning up towards desired spark . I've set this desired spark at about 14deg but you could change this for your application. I can run this car up a slight incline driveway at 6km/hr cold with foot off pedal with NO Surge. Blew me away really.
Now the other thing to remember is that the ECT TP will start to learn upwards from the minimum together with spark learning once you are close to target so don't worry about that when you see it happening. All this happens in the background giving a uniform feel to the overrun in each gear but can be set up through tuning to suit any application/combination of engine specs.
Point 4:
Because 6th & 5th gear provide more glide the minimum idle airflow in these gears ends up being much lower than the other 4 gears and you can end up with quite a different "looking" table to the factory Holden one.
Low speed surge is addressed here too. Coastdown spark is the target spark when driving in car parks, up driveways etc so you need to dial in this table to achieve an idle spark of between 14 to 18. The ETC TP will have learned up from minimum by this stage so minimum idle airflow 1st gear doesn't come into it unless you are miles out. Set up rows 600 & 400 rpm with higher settings like 20 then up to 30 at row 400rpm . This acts like a back stop and ups coastdown spark instantly should it dip below target for any reason. This technique works really well.
Point 5:
The feel of the down change on overun is affected by minimum idle airflow as well. In particular 4th 5th 6th gear, when a down change occurs the minimum idle airflow sets ECT TP for the next gear. The feel of the down change can vary from jerky to barely perceivable by adjusting these settings. Setting the next gear down to run more or less ECT TP on minimum idle airflow.
Point 6:
DCFO only stays on with the torque convertor locked (just like in a LS1) once it unlocks DCFO turns off ( I didn't know that )
Point 7:
Observing IPW during DCFO and as you exit DCFO in search of fuel economy I've noticed that:
>With DCFO "on" IPW does not equal "minimum pulse width" as defined in the tables. I assumed it did.
>STFT's go to zero.
>That when DFCO turns "off" the IPW actually decreases as STFT trims the fuel back ( I tune the VVE table slightly rich like most people do )
>So I'm actually using less fuel with DCFO off than I am on... :)
Which leads me to the question > when in DCFO does it just run with the VVE table with no fuel trims? It certainly does not appear to be turning off the injectors or going to some defined ms pulse width.
Any comments welcome.......
thankyou.
Mike
Mods to engine include AFM Delete kit the big Texas Speed LS3 camshaft, FAST intake manifold, supporting Valvetrain mods, Airspeed OTR Mafless, the large X-force full exhaust twin 3 inch.
In an effort to produce a car with drivibility near to standard yet have a good cold start, good cold running, excellant "car park" manners, good fuel economy, good overrun characteristics etc I've been spending more time road tuning than I have dyno tuning :)
I would like to share a few "discoveries" I've made and a few questions to ponder and perhaps get a few answers back.
Info on these settings in the thread title has been hard to find in the E38 section. Some of you may already know the information below some may not.
Point 1:
I have found that "desired coastdown speed" appears to be the same as the desired idle speed in gear. Important to know to be able to set coastdown spark table, coastdown high and low spark tables and most importantly Minimum Idle Airflow which is essentially minimum blade angle on initial throttle pedal return.
Point 2:
The e38 is very clever in its idle and coastdown strategies and easily learns between a maximum and a minimum blade angle. As long as there is a broad enough range the targets can be met. Observation on overrun of ETC TP , RPM and spark from 100km/hr in 6th gear down to 6km/hr in 1st gear had allowed me to first dial in the minimum idle airflow table. The idea seems to be to get the rpm to return to as close to target idle rpm as you can. If its too high the spark will show this by learning down as far as it can set by Coastdown spark table high. But only when NOT in DCFO. So in 6th and 5th gear I've gone for about 1200rpm coasting in DCFO and -5 degrees. Set this rpm by simply reducing minimum idle airflow in 6th gear until you reach the rpm that feels right to you the driver. Reduce by 1g/s lots until you get close then by 0.5g/s after that. You will see the ETC TP getting smaller on overrun each time.
Point 3:
In 4th, 3rd, 2nd & 1st gears you dial it in via your idle RPM target watching spark learning. If spark's lower the the desired spark in the coast down table you need to keep lowering minimum idle airflow in the appropriate gear until you see the spark learning up towards desired spark . I've set this desired spark at about 14deg but you could change this for your application. I can run this car up a slight incline driveway at 6km/hr cold with foot off pedal with NO Surge. Blew me away really.
Now the other thing to remember is that the ECT TP will start to learn upwards from the minimum together with spark learning once you are close to target so don't worry about that when you see it happening. All this happens in the background giving a uniform feel to the overrun in each gear but can be set up through tuning to suit any application/combination of engine specs.
Point 4:
Because 6th & 5th gear provide more glide the minimum idle airflow in these gears ends up being much lower than the other 4 gears and you can end up with quite a different "looking" table to the factory Holden one.
Low speed surge is addressed here too. Coastdown spark is the target spark when driving in car parks, up driveways etc so you need to dial in this table to achieve an idle spark of between 14 to 18. The ETC TP will have learned up from minimum by this stage so minimum idle airflow 1st gear doesn't come into it unless you are miles out. Set up rows 600 & 400 rpm with higher settings like 20 then up to 30 at row 400rpm . This acts like a back stop and ups coastdown spark instantly should it dip below target for any reason. This technique works really well.
Point 5:
The feel of the down change on overun is affected by minimum idle airflow as well. In particular 4th 5th 6th gear, when a down change occurs the minimum idle airflow sets ECT TP for the next gear. The feel of the down change can vary from jerky to barely perceivable by adjusting these settings. Setting the next gear down to run more or less ECT TP on minimum idle airflow.
Point 6:
DCFO only stays on with the torque convertor locked (just like in a LS1) once it unlocks DCFO turns off ( I didn't know that )
Point 7:
Observing IPW during DCFO and as you exit DCFO in search of fuel economy I've noticed that:
>With DCFO "on" IPW does not equal "minimum pulse width" as defined in the tables. I assumed it did.
>STFT's go to zero.
>That when DFCO turns "off" the IPW actually decreases as STFT trims the fuel back ( I tune the VVE table slightly rich like most people do )
>So I'm actually using less fuel with DCFO off than I am on... :)
Which leads me to the question > when in DCFO does it just run with the VVE table with no fuel trims? It certainly does not appear to be turning off the injectors or going to some defined ms pulse width.
Any comments welcome.......
thankyou.
Mike