MFI for a Type 4, Any interst? Options

[ClayPerrine]

QUOTE (lapuwali @ Jun 23 2005, 11:36 AM)

Pure speculation here, but I suppose if you sprung the pump rack so it was normally at full lean, then provided some control pressure (perhaps just plumb into the oil system and use oil pressure) then used two servo valves, one to add pressure, one to release it (both closed to hold the rack at one position), you could get pretty good control. You could also use one valve you make yourself: a rotary valve with drilled passages that either allowed oil in from the pressure side, drained oil from the rack side, or closed it off, then the servo itself wouldn't have to be all that fast or accurate. It just has to spin the valve to one of three positions. The open questions at that point is could full oil pressure pin the rack against the spring to full open with sufficient speed? You'd also want to close the feedback loop by having a way to measure the pump rack's position, so you just add or drain pressure until the rack is in the right place. This would require a pretty high precision method of measuring the rack's position in real time. I'd probably use something like a magnet and a pair of Hall Effect sensors.

Why do you need a way to measure the rack position? Just use the O2 sensor and temp sensors for feedback. It doesn't have to be as precise as you describe. A fixed mixture curve until the O2 sensor comes online, and then read the O2 sensor to adjust the rack. As for accelleration enrichment, reverse the spring to drive the rack full rich (you would need this for startup anyway)and all you need is to dump the control pressure (i.e. change the frequency of the valve) briefly, and the rack would move via spring pressure. After the initial accelleration, the pressure comes back up, and the mixture returns to normal.

I wonder if the control rack spring can be compressed with 10 psi?

Now I am going to be doodling on the back of a piece of paper the rest of the afternoon.

[michel richard]

QUOTE (ClayPerrine @ Jun 23 2005, 07:37 AM)

QUOTE (michel richard @ Jun 23 2005, 09:31 AM) QUOTE (ClayPerrine @ Jun 23 2005, 07:19 AM) The only real question I have is... what do I do for control pressure?  The electric pump on an MFI system only supplies 10 PSI. The high pressure is supplied by the cam followers when they are compressed. Not sure why fuel pressure is an issue. Electric pump supplies 10 pounds to the injection pump and the latter takes it to 300 pounds, or whatever, to go through the hard lines to the injectors. If fuel pressure is an issue, I must be missing something. There is a fuel pressure regulating thingy inside the electric fuel pump, as well as inside the big fuel filter assembly, I believe. Michel In a CIS system, the fuel is used as hydraulic fluid for control pressure. The control pressure opposes the Air pushing up the air flow meter. the higher the control pressure, the leaner the mixture. But it takes 70 PSI to run the CIS system due to the control pressure. In an MFI system, the injection pump takes the 10 PIS from the electric pump and when one of the cam lobes in the injection pump comes up, the fuel is pushed out at about 3000 psi. Becasue the pressure is only 10 psi until it's injected, I can't use it for control pressure.

I was, indeed, missing something (ain't being civil fun !). Using CIS parts sounds very complicated to me. If I understand correctly, you would still be using big chunks of an MFI injection pump, so that the wide availability of CIS parts would not be big help from a system wide perspective i.e. you would still need to find an MFI pump to implement the system. Still, if you meet some success, I'll be very interested to hear about it.

As far as accuracy of rack positionning is concerned I figured the following eyeball estimation in the case where the warmup regulator actuation lever is used: if 3/8th of an inch is 3 points of mixture (from say, 11 to 14) , and you aim to adjust mixture to within 1/10 of a point, you need resolution of about 12 thou. Not sure if that estimation has any relevance when considering a system that acts directly on the main rack.

If you then have 4 to 1 leverage, mechanically, you need approximately 50 thou of resolution. I think that should be achievable.

In any event, I'll try my best case scenario for controlling a servo motor using Megasquirt over the weekend. If I'm successful, I will certainly let you know.

Michel

[rick 918-S]

well this rapidly excellerated way beyond my ability... (IMG:http://www.914world.com/bbs2/html/emoticons/wacko.gif) I nominate this for classic thread status. I need more time to read this stuff than my fast speed reading will allow. (IMG:http://www.914world.com/bbs2/html/emoticons/monkeydance.gif) Some good and interesting info. Keep it going. (IMG:http://www.914world.com/bbs2/html/emoticons/clap.gif)

[redshift]

I tried to figure out how I could do this a couple years ago, and I got stuck at trying to figure out where my cam tower is.

(IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)


M

[lapuwali]

QUOTE (ClayPerrine @ Jun 23 2005, 09:55 AM)

QUOTE (lapuwali @ Jun 23 2005, 11:36 AM) Pure speculation here, but I suppose if you sprung the pump rack so it was normally at full lean, then provided some control pressure (perhaps just plumb into the oil system and use oil pressure) then used two servo valves, one to add pressure, one to release it (both closed to hold the rack at one position), you could get pretty good control.  You could also use one valve you make yourself: a rotary valve with drilled passages that either allowed oil in from the pressure side, drained oil from the rack side, or closed it off, then the servo itself wouldn't have to be all that fast or accurate.  It just has to spin the valve to one of three positions.  The open questions at that point is could full oil pressure pin the rack against the spring to full open with sufficient speed?  You'd also want to close the feedback loop by having a way to measure the pump rack's position, so you just add or drain pressure until the rack is in the right place.  This would require a pretty high precision method of measuring the rack's position in real time.  I'd probably use something like a magnet and a pair of Hall Effect sensors. Why do you need a way to measure the rack position? Just use the O2 sensor and temp sensors for feedback. It doesn't have to be as precise as you describe. A fixed mixture curve until the O2 sensor comes online, and then read the O2 sensor to adjust the rack. As for accelleration enrichment, reverse the spring to drive the rack full rich (you would need this for startup anyway)and all you need is to dump the control pressure (i.e. change the frequency of the valve) briefly, and the rack would move via spring pressure. After the initial accelleration, the pressure comes back up, and the mixture returns to normal. I wonder if the control rack spring can be compressed with 10 psi? Now I am going to be doodling on the back of a piece of paper the rest of the afternoon.

Response time. If you measure O2, you've now got a delay between the time the rack position affects the mixture and the time you read the new mixture, based on the distance between the exhaust port and the O2 sensor. This means the rack will now be set to too rich, requiring you to reverse the rack, which will overshoot on the other side, and back and forth. Closed loop O2 sensing only "adjusts" the mixture even on OEM systems, it's not the only measure, and it's not the only control mechanism. At WOT, the O2 sensor is completely ignored. Narrow-band sensors also only allow you to control the mixture very close to 14.7:1, which is too lean high engine loads on any engine, let alone an air-cooled engine.

A wideband sensor can be used to fix that, but you still have the delay. Again, this is all speculation on my part. I have no idea if the delay is significant, nor do I have any idea if you'd need the complication of a hydraulic actuator over a simple stepper motor. Until there's actual data on how the pump rack moves in the real world with the real logic section, there's no knowing what's necessary. If you build a measurement device to log what the rack does just to choose an actuator strategy, then you can use the same device to control the actuator once you're doing that.

One thing that's always stopped me from doing this is that it probably wouldn't actually make any difference, or not enough difference to make the effort worthwhile. A staged injector EFI system could be much more easily devised to test if full sequential operation made any real difference under heavy loads (I strongly suspect it doesn't). The vaporization benefits are, I expect, primarily in the realm of emissions, which wouldn't be a bad thing at all, but you'd clean up the emissions dramatically on a Type IV by just fitting a catalytic convertor for a lot less money and effort. It would be a fun project, but it isn't my thing to build something for huge effort that's no better than something else that's cheaper and easier to do. Guess I'm really too much of an engineer that way: always pursuing the best efficiency in all ways, including time and money spent.

Lots of fun to think about, though.

[Katmanken]

Not sure that MFI will give you a big boost in power...

Dad had a 1973 Alfa 1750 Berlina with the Alfa Spica MFI...

A bug could beat it off the line, (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif)

But at about 50, that sucker would blow the doors off almost anything else..... (IMG:http://www.914world.com/bbs2/html/emoticons/happy11.gif)

Loved the line in the handbook .... "Kindly do not exceed 132 mph in 4th gear....." (IMG:http://www.914world.com/bbs2/html/emoticons/driving.gif)

Then you go for 5th..... (IMG:http://www.914world.com/bbs2/html/emoticons/blink.gif)


Ken

[bd1308]

my dad said he rode in a tricked out austin healey (sp check) and the driver was doing some 170 in it....in 4th gear. getting close to redline and so he reached down and flicked on the electric overdrive....and back down to 2000RPM(UPM in our cars (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif) ) ready to go even faster....

I would have crapped my pants.

[lapuwali]

QUOTE (kwales @ Jun 23 2005, 06:29 PM)

Not sure that MFI will give you a big boost in power... Dad had a 1973 Alfa 1750 Berlina with the Alfa Spica MFI... A bug could beat it off the line, (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif) But at about 50, that sucker would blow the doors off almost anything else..... (IMG:http://www.914world.com/bbs2/html/emoticons/happy11.gif) Loved the line in the handbook .... "Kindly do not exceed 132 mph in 4th gear....." (IMG:http://www.914world.com/bbs2/html/emoticons/driving.gif) Then you go for 5th..... (IMG:http://www.914world.com/bbs2/html/emoticons/blink.gif) Ken

I think you're misremembering something. The '73 Berlina had a 2000 engine, not a 1750. The 1750 was '69 and '71 only (there was no US '70 model). On both the 1750 and the 2000, switching to Euro cams makes a HUGE difference. The US 1750 only made 105hp, where the Euro version made 130. On the 2000, it was 115 v. 150hp. There's a guy in TX that has a 1750 engine in his car with re-tuned SPICA, Euro cams, and some mild porting, and it makes 165hp at the wheels.

I had a '73 2000 Berlina just 3-4 years ago. Exactly the same drivetrain as the GTV and Spider, just a wheelbase that was 2" longer. Despite it's smog-choked stock tune, it would still out-drag my 1.7. A hot Bug probably would, too...

[J P Stein]

Wyane Baker ran MFI on his 220hp, 2.2L, t-4 race car.
BMW Kultznswiner (I could be wrong with the speeling (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) )

[Dave_Darling]

I think that is the car that Mistak has now--or had, back when I first met him.

Yeah yeah yeah, Kugelfischer Kugelfischer Kugelfischer.

--DD

[Katmanken]

James,

I guess we both misremember. The 1750 ended in 72 and had 115 hp. Still was slow, 0-60 was 10.3 sec for the 1750 and 9.7 for the 2000.

I meant dad bought the 1750 in 73. Iit had 18,000 miles on it and He paid $1450 for it. Some lady had just inherited a big house and a big car and didn't want the "little" car anymore......

I'm still waiting for my deal like that...

Ken

[lapuwali]

QUOTE (kwales @ Jun 24 2005, 08:00 PM)

James, I guess we both misremember. The 1750 ended in 72 and had 115 hp. Still was slow, 0-60 was 10.3 sec for the 1750 and 9.7 for the 2000. I meant dad bought the 1750 in 73. Iit had 18,000 miles on it and He paid $1450 for it. Some lady had just inherited a big house and a big car and didn't want the "little" car anymore...... I'm still waiting for my deal like that... Ken

Oh, Berlinas are a dime a dozen. I got mine for $500 and gave it away a year or so later to someone who needed parts off it more than I needed the car. An absolutely cherry car is maybe $3000. There's a guy in Berkeley that trades them often, and could (and would happily) tell you where many of the Berlinas still on the road are, and where you could get one for a good price. I'd personally hold out for a Giulia Super, but they're over $8K in nice shape now.

btw, in 1973, a 0-60 time of under 10 seconds wasn't slow. Checked out the 0-60 of a '72 2.0 914 sometime? 9.7sec was a good bit better than average. A Bug certainly couldn't do anything like that.

In any case, we've drifted off track. Alfas with the SPICA system and US cam tuning were substantially faster than the same cars with dual Webers fitted, a common thing when a pair of Webers cost less than a SPICA pump rebuild (no longer true). Fit Euro cams with the Webers, and you picked up a lot of power. Retune the SPICA for the hot cam, though (hard to do until recently), and you'd blow away the Weber'd car again. Call up Wes Ingram and ask, if you like. He probably has dyno sheets to pass on.