[urq] EFI + MAC-14 maxing ataround 5k RPM

[Cody Forbes]

>> What you refer to is known usually as 'Hybrid Alpha-N' which was
>> pioneered on the F40 IIRC. MS >can be run in speed desnity mode, MAF
>> mode, alpha-n mode and hybrid alpha-n mode, but most >run speed
>> density with only a very small handfull on either form of alpha-n.
>> Anyways, yeah Bens >setup is on MAP vs RPM with modifiers like air
>> temp, coolant temp, TPS accel enrichment (like >a carburettor accel
>> pump).      
> 
> It appears from below, that this setting is working, but I bet one
> has to become familiar with it using a 272 cam on a turbo audi.... 
> 

Mine has a 272 Blau cam and holds a nice steady even vacuum, speed density works fine.

> 
>> I just looked at a log file where Ben started the engine and slowly
>> let it run up to 5k. Duty cycle >is perfectly fine, never higher
>> then 50%. From what I'm seeing it looks like an ignition missfire.
>> >TPS stays perfectly still, but for one split second the vacuum goes
>> away and simultaneosly the >O2 reads lean, while the MS tried to
>> compensate for it and bounced the fuel up a bit. Everything >in the
>> settings looks good too, BTW. I call ignition problem, but I have no
>> suggestions for why :-(.       
> 
> That makes more sense to me, it sure appears fuel is there. 
> Ignition:  RPM signal falling out - weak signal, worn teeth, bad
> sensor, wiring issue...   Arc: in the wires, distr, and/or rotor. 
> Bad plug/s.  Incorrect IAT sender.   
> 

If it were a signal problem then it would show up in the MegaSquirt logs. Bens MS tach signal comes from the tach output of the MAC-14, so if if the signal to the MAC-14 faltered you would see matching odd-ness in the MS tach readings. Granted RPM did shift arround a bit, but I believe this was accurate due to the misfires.

Ben says he checked all of the secondary ignition components, but it is possible that something was missed. 

> 
> 
>> MAP reprogramming is not something most can do, this is assembler
>> language stuff burned on >the CPU and frankly should never need to
>> be edited.  
> 
> Isn't there a software adjustment for load value, or is that adjusted
> for in the VE tabling?  There has to be a way to trim the load values
> without a reburn, since that will vary as MS is installed on various
> motors.  Curiousity more than something that needs to be done, it
> certainly appears fuel isn't the focus anyhow.    

Yeah you adjust the fueling needs in the VE tables. There are other places things get adjusted, but primarily all tuning is done on the VE table. In reality the 'VE' table is not a proper name because very very few cases actually end up with it close to the VE. Really they should call it a fueling table or something.

Here are some screen shots of the software you could browse through if that curiosity still lingers:
http://jcforbes.com/jcfpics/album10 - Gallery of screen shots.
http://jcforbes.com/jcfpics/album10/Image43 - Fuel table tuning screen. MAP going up, RPM going to the right.
http://jcforbes.com/jcfpics/album10/Image24 - Basic settings.

-Cody Forbes
http://www.5000tq.com
'87 5ktq - Fast.
'87 5ktq QLCC'd plus some
'86 5ktqCD
'86 5k
'86 5k