Discussion
It's possible, but as ever the devil is in the detail. An AFM is a simple sensor, so you could easily sum two of them with a circuit. How would you deal with balancing the two plenums? Then you start to think - should one AFM be used to drive 1 bank of injectors, and the other one drive the 2nd bank? Then you get to the point of having 2 14CUXs in the car... 
BTW I do have a twin chamber plenum setup on my Griff, and have found it runs very well like it. (Although it's managed by an aftermarket ECU.)
BTW I do have a twin chamber plenum setup on my Griff, and have found it runs very well like it. (Although it's managed by an aftermarket ECU.)
It would be difficult- the AFM response is far from linear, so by reducing the airflow the part of the response curve changes, so you cant simply sum the two inputs together. You would have to digitally remap the AFM output or remap the ECU, and id suspect you would loose some low airspeed calibration in the process.
Not without loosing resolution again- one AFM will go from .8 volts to 5 volts say on a 5 ltr. Halve the airflow and it might go from .8 to 3 volts, so you loose the previously available 3-5 volt mapping range. Also the air draw over 8 cylinders will be less pulsed that that of 4 if you split the plenum. This might produce pulses the AFM will pick up at low speed, instead of averaging the airflow out for a basic load point requirement, but Ive not tested it- It would be much easier just to draw the air through one bigger AMF with a y piece.
leerdam23 said:
Stupid Question... How easy would it be to splice together 2 AFM's to feed the 14cux, each AFM feeding a separate plenum, ie there are 2 plenums on the engine, each feeding 4 cylinders.
Why bother??Just take the engine from your Tuscan racer and pop-it-in the Griff? That's almost as easy as swopping the Loom & ECU to go with it?
Sounds like you are missing the Tuscan's ooumph even before you've got to Rockingham......
CU at Gurston?
Trev
Weird thing that - it looks er, home made and also looks like it weighs a ton. And why go to the trouble of bending intake pipes when you're still bolting them onto the standard intake manifold (lenghtening the intake tracts in the process - great, even more low down torque at cost of the higher rpm range, just what we need for an RV8...)?
Great idea -, execution, er, not sure about that one. If keeping the standard manifold, I'd have preferred two narrowish plenums right on top with the trottle body/ies in front - like the one Else (IIRC) has been doing and very similar to the engine that was in the Morgan Plus 8 BPR racer back then...
Great idea -, execution, er, not sure about that one. If keeping the standard manifold, I'd have preferred two narrowish plenums right on top with the trottle body/ies in front - like the one Else (IIRC) has been doing and very similar to the engine that was in the Morgan Plus 8 BPR racer back then...
I've had this one for a few years now: (Mine's obviously the original )
It works well and isn't heavy. (Made from folded Al sheet, so a bit lighter than a standard cast plenum) It doesn't collect up too much low down torque, makes the car smooth to drive and it gets pretty good top end power. I got around the AFM issue by using a speed-density ECU.
There's no problem in theory at least with rescaling the AFM calibration of two smaller units. The output is proportional to the square of airflow, so it's not hard to work out a best guess calibration to put in the ECU that you can refine over time. Agree that you'd lose resolution unless you choke the AFM tubes or use smaller AFMs.
I still like the silly idea of running one engine with 2 ECUs.
)It works well and isn't heavy. (Made from folded Al sheet, so a bit lighter than a standard cast plenum) It doesn't collect up too much low down torque, makes the car smooth to drive and it gets pretty good top end power. I got around the AFM issue by using a speed-density ECU.
There's no problem in theory at least with rescaling the AFM calibration of two smaller units. The output is proportional to the square of airflow, so it's not hard to work out a best guess calibration to put in the ECU that you can refine over time. Agree that you'd lose resolution unless you choke the AFM tubes or use smaller AFMs.
I still like the silly idea of running one engine with 2 ECUs.
blitzracing said:
Not without loosing resolution
dnb said:
Agree that you'd lose resolution unless you choke the AFM tubes or use smaller AFMs.
Although we now have a lot of flexibility with the 14CUX AFM scalar I do take your point about reducing the resolution, half the resolution and you half the accuracy and that could be critical with the AFM.robertf03 said:
Quote from Instructions to change fuel maps on 14CUX
The vacuum gauge and the load row were surprisingly close.
Now Robert has proved a vacuum gauge and the load row in RoverGauge are surprisingly close could we replace the AFM with a 0-5v vacuum sensor. I realise the 0-5v would have to be reversed as least air flow would mean max vacuum and max air flow would mean least vacuum. The vacuum gauge and the load row were surprisingly close.
Sorry it’s only a random thought or more like wishful thinking.
Not a daft idea at all. But you really need to consider more sensors than just vacuum.
The idea was played with years ago when I was in to Impreza tuning. Here's one of the old websites:
http://www.teamcarr.pwp.blueyonder.co.uk/MAFSIM/
For the sake of defining the TLAs:
MAF = Mass Airflow Sensor (ie an AFM)
MAP = Manifold Absolute Pressure (sensor reads the right way round for us)
The idea was played with years ago when I was in to Impreza tuning. Here's one of the old websites:
http://www.teamcarr.pwp.blueyonder.co.uk/MAFSIM/
For the sake of defining the TLAs:
MAF = Mass Airflow Sensor (ie an AFM)
MAP = Manifold Absolute Pressure (sensor reads the right way round for us)
Edited by dnb on Thursday 13th March 23:52
Edited by dnb on Thursday 13th March 23:54
Mark Adams sells a unit which can combine the signals or two AFMs which he uses on the JE Crossover Manifolds. I believe he has used this on both 14CUX and GEMS
Details in this thread:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Details in this thread:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Interesting, but he does say its an expensive aftermarket part- it could have been the 14.7 fuel controller I played with that allows you to fully remap and AFM with both voltage in to voltage out and in RPM bands as well. Technically its was brilliant (microprocessor controlled) as to what it could do, but horribly unreliable, as it kept locking up, and worse it would randomly rewrite is lookup tables. Luckily when it failed the good old 14cux dropped back into get you home mode, so at least I was not standed at the road side. Its now with all the other "did not work" bits in the shed.
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