ITBs, large cams, speed density and altitude change

[Grant]

Sprocket thanks for the detailed response.  You were very helpful when I got my first ITB 4AGE running on VEMS in 2008 or so! 

I'll be using your advice when we give TPS mode a try.

[Kamuto]

Also wanted to mention that some other systems allow blended maps for MAP low load/TPS high-load for ITB installs and people are happy with it.  We seem to only allow TPS low load/MAP high load, which is great for boosted cars.

it just seems your tps has dead zone or something, no problem at all with alpha-N

[VEMS]

Also wanted to mention that some other systems allow blended maps for MAP low load/TPS high-load for ITB installs and people are happy with it.  We seem to only allow TPS low load/MAP high load, which is great for boosted cars.

Many changes have been implemented since 1.1.44 firmware (that is firmware from many years ago), including allowing several combinations of axises and combinations of multiple maps for fuel and the other tables.

Best regards, Dave

[Grant]

I poked around with 1.2.10 and VemsTune 11-06-14 last week but I'll look more. Thanks!

[Grant]

We looked into using any-trim control do do what we wanted, but that won't work as I need to do scalling with respect to RPM.

I switched him over to alpha-n tonight, but now I'm seeing something weird - VE table and IGN table show TPS at 0 when the engine is off (TPS is calibrated) but with the engine idling TPS on VE shows 5 degrees and IGN shows 0 degrees. 

Both are set for alpha-n mode, and scale from 0-100%.  I looked through the settings but don't see anything obvious that would cause TPS value to change.

[MWfire]

check IAC aplha/n load compensation.

[Sprocket]

check IAC aplha/n load compensation.

Sounds about right.

This setting is in 'Idle Control General' menu at the very bottom

[Grant]

Ahh, I see.  So the purpose is to allow the use of IAC with TPS and add fuel based on IAC duty cycle or something right? 

[VEMS]

Correct Alpa-N Load axis (TPS) is compensated for IAC added load (/airflow), more info: http://vems.hu/vt/help/v3/v3_idle_settings.html

Best regards, Dave

[Grant]

Hi Guys,

We've been busy with personal stuff so only got as far as starting his car on Alpha-N. 

I noticed there's a new firmware 1.2.32 - says something about calculated load on y axis for Ign and Lamda tables.  Also somethingi about smoothing input for ITB's and turbos...

Anyone know where I can find details about this new version?  We think the best way for a street car with ITB and altitude changes is load (global) being calculated with external baro input offset built in, and also having blended alpha-n/map where it's SD for low load, TPS for high load like the megasquirt guys are doing. 

Just wondering if coincidentally there has been some development in this area that would benefit ITB cars?

Sorry to be such a pain in the arse.

[VEMS]

Hello Grant,

It seems you keep trying to reinvent the wheel here, you already know the proper way to map this car as per mine (and others) recommendation (Alpha-N with baro compensation).
Perhaps you did not know this but i also do most of the VEMS firmware development and let me assure you this change is not related and not helpful for mapping non ITB+Turbo cars.

We think the best way for a street car with ITB and altitude changes is load (global) being calculated with external baro input offset built in, and also having blended alpha-n/map where it's SD for low load, TPS for high load like the megasquirt guys are doing. 

In the low load area SD will actually have poorest load indication on an ITB+Large cam car, while pretty okay on high load/high rpm; TPS provides good load indication everywhere. I suspect you have applied reversed logic there :)

Take care 1.2.32 firmware is not released yet (marked: experimental, only for testing), normal users are recommended to stick to released versions

Best regards, Dave

[Grant]

Dave,

Thanks for helping me with insight on the firmware side. 

I will respect your input and try his car on alpha-n and let you know if I have any trouble.

Cheers!

[Sprocket]

Set up an engine today, FW1.2.31 on Alpha-N/ MAP compensation with Hybrid MAP/TPS threshold =110kpa. Once I set up the break points, it worked an absolute treat :D

[Grant]

Hi Sprocket,

What is the significance of the 110kpa theshold?  I think I had it set at 0.  Also any advice on how you set up the MAP compensation?  I'm not quite there yet but would be good to hear your input. 

We are having a strange issue with the engine bucking very badly when the coolant fan kicks on at idle, nothing else really changed other than switching to alpha-n.  I'm still investigating, will update later.

[Grant]

Should MAP sensor connection be Before or After throttle?