Switch Barn door L-jet for LH MAF?
12-03-2002, 08:03 PM
#1
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Switch Barn door L-jet for LH MAF?
Hey guys.
GOing DTA on the 89S4 when I get the 81 back together. The LH hotwire maf is JUST sitting there, so I was thinking.....
Can I put the hotwire MAF on the 81 with some tweaking? Any idea how? The 944 guys do this all the time, but that is because they use a really pricy box with ***** on it that tricks there "DME" into thinking its the barn door.\\
Any ideas?
Brendan
GOing DTA on the 89S4 when I get the 81 back together. The LH hotwire maf is JUST sitting there, so I was thinking.....
Can I put the hotwire MAF on the 81 with some tweaking? Any idea how? The 944 guys do this all the time, but that is because they use a really pricy box with ***** on it that tricks there "DME" into thinking its the barn door.\\
Any ideas?
Brendan
12-03-2002, 08:52 PM
#2
Nordschleife Master
What would you gain?
You can't reprogram the analog computer, so your not going to get any better mixture control.
You also wouldn't switch out the narrow ?US intake for the larger LH system.
I put up a post about switching the whole system. Brain, intake pendlum, and MAS, and how much that would invlove. No body bit, so I don't know.
Anyone know what all would need to be switched out to get an advantage?
You can't reprogram the analog computer, so your not going to get any better mixture control.
You also wouldn't switch out the narrow ?US intake for the larger LH system.
I put up a post about switching the whole system. Brain, intake pendlum, and MAS, and how much that would invlove. No body bit, so I don't know.
Anyone know what all would need to be switched out to get an advantage?
12-03-2002, 09:32 PM
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The removal of a massive intake restriction is an excellent reason to get the bastard barn door out of there; it's pretty well documented that the AFM is a big cork in the bottle. The MAF may also provide a more precise output than a mechanical resistance sweep.
It seems to me that you'd need to know what range of resistance the L-Jet expects to receive from the AFM, the output range of the new MAF, and then use some kind of electronic intermediary, a la the magic boxe$$$ the 944 guys use. The same box may work for us; dunno. You'd be a god if you could find a way to do this with just a few pots, resistors, and a pcb.
You'd also need to find a way to interpolate the air temp data from the MAF to correspond with what the L-Jet is expecting from the air temp sensor inside of the AFM.
More? Well, you'd have to power the sucker...and doesn't the hotwire have a "burn-off" cycle to self-clean? PITA...
Really interesting proposition!
It seems to me that you'd need to know what range of resistance the L-Jet expects to receive from the AFM, the output range of the new MAF, and then use some kind of electronic intermediary, a la the magic boxe$$$ the 944 guys use. The same box may work for us; dunno. You'd be a god if you could find a way to do this with just a few pots, resistors, and a pcb.
You'd also need to find a way to interpolate the air temp data from the MAF to correspond with what the L-Jet is expecting from the air temp sensor inside of the AFM.
More? Well, you'd have to power the sucker...and doesn't the hotwire have a "burn-off" cycle to self-clean? PITA...
Really interesting proposition!
12-03-2002, 09:59 PM
#4
I'll bite.....
Jim has a good start on fundamental needs.
We did something similar in college. We took a Dodge minivan and converted it to propane. The trick was: We had to retain the stock computer and build interfaces between the sensors and the computer. You should see what propane will do to knock an O2 sensor out of range.....Talk about some work.
Here's what one needs to know:
1) Resistance range of barn door potentiometer
2) Amperage through potentiometer
3) Voltage range from potentiometer to brain
4) Voltage range or resistance range from air temp sensor in L-Jet
The interface would be a simple level shifter that can consist of an op-amp and possibly external transistors..... Very simple.
Anybody have access to the 944 black box? Maybe some reverse engineering would be in order.
This begs the question..... Where does the 3-wire 02 sensor fit into the equation and is it necesssary for "clean and proper" operation with
the L-Jet.
I hate the L-Jet barn door....... This idea interests me greatly.
Scott
Jim has a good start on fundamental needs.
We did something similar in college. We took a Dodge minivan and converted it to propane. The trick was: We had to retain the stock computer and build interfaces between the sensors and the computer. You should see what propane will do to knock an O2 sensor out of range.....Talk about some work.
Here's what one needs to know:
1) Resistance range of barn door potentiometer
2) Amperage through potentiometer
3) Voltage range from potentiometer to brain
4) Voltage range or resistance range from air temp sensor in L-Jet
The interface would be a simple level shifter that can consist of an op-amp and possibly external transistors..... Very simple.
Anybody have access to the 944 black box? Maybe some reverse engineering would be in order.
This begs the question..... Where does the 3-wire 02 sensor fit into the equation and is it necesssary for "clean and proper" operation with
the L-Jet.
I hate the L-Jet barn door....... This idea interests me greatly.
Scott
12-03-2002, 10:10 PM
#5
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I've been looking at this which is about $300:
<a href="http://www.splitsec.com/products/psc1/PSC1009.htm" target="_blank">Link: Programmable MAF converter</a>
Possibly using a 95 Mustang MAF, which is cheap, about $150, and has a square flange.
Some background from the site above (highlighting by me):
[quote] Universal MAF kits can be used to replace an air flow meter with a mass air flow (MAF) sensor. Kits are available with either the MAF 3.0 sensor or the MAF 3.5 sensor. There are also two choices for calibration electronics. The ARC2-A calibrator has front panel controls and is on-the-fly adjustable from the driver’s seat. It is easy to tune and can be set up in a short period of time. The PSC1-004 is the other calibrator that is available. It is laptop programmed and capable of much more accurate calibration. See the ARC2-A and PSC1-004 data sheets for more information.
In general the universal kits are compatible with most Motronic air flow meter systems. The kits do not work with L-Jetronic systems because of their higher operating voltage range. To make sure that your car is compatible with the universal kit, you can measure the air flow signal from your stock sensor. Measure the voltage with the ignition on and move the flapper over its entire range of travel. If the signal stays within the range of zero to 5V, your system is compatible with the universal kits. If your air flow signal goes above 5V, we may be able to offer a solution using the PSC1-009 calibrator. <hr></blockquote>
It seems you need a separate temp sensor with the MAF conversion.
Has anyone measured/have specs for the voltage range on the 928 AFM?
<a href="http://www.splitsec.com/products/psc1/PSC1009.htm" target="_blank">Link: Programmable MAF converter</a>
Possibly using a 95 Mustang MAF, which is cheap, about $150, and has a square flange.
Some background from the site above (highlighting by me):
[quote] Universal MAF kits can be used to replace an air flow meter with a mass air flow (MAF) sensor. Kits are available with either the MAF 3.0 sensor or the MAF 3.5 sensor. There are also two choices for calibration electronics. The ARC2-A calibrator has front panel controls and is on-the-fly adjustable from the driver’s seat. It is easy to tune and can be set up in a short period of time. The PSC1-004 is the other calibrator that is available. It is laptop programmed and capable of much more accurate calibration. See the ARC2-A and PSC1-004 data sheets for more information.
In general the universal kits are compatible with most Motronic air flow meter systems. The kits do not work with L-Jetronic systems because of their higher operating voltage range. To make sure that your car is compatible with the universal kit, you can measure the air flow signal from your stock sensor. Measure the voltage with the ignition on and move the flapper over its entire range of travel. If the signal stays within the range of zero to 5V, your system is compatible with the universal kits. If your air flow signal goes above 5V, we may be able to offer a solution using the PSC1-009 calibrator. <hr></blockquote>
It seems you need a separate temp sensor with the MAF conversion.
Has anyone measured/have specs for the voltage range on the 928 AFM?
12-03-2002, 10:45 PM
#6
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Virubusunits-man-with-a-confusing-handle....
Well, maybe not much? But I have one, and nobody wants it when I try to sell it, so I may as well try and use it....
James, Scott and PorKen:
That 944 black box is the Arc2 Many, Many 944 guys use it and love it. I do remember when doing this research on the 924S (944 with skinny body), that the voltage was different, and that was why you couldn't just unplug and plug and play.
I would just use the LH and EZK computer and MAF from the 89 for this, but the LH died, the EZK is sold, and I need to either sell the MAF, or use it for something. I will eventually simply DTA the 81 as well, but it the mean time, this seemed an interesting idea....
Well, maybe not much? But I have one, and nobody wants it when I try to sell it, so I may as well try and use it....
James, Scott and PorKen:
That 944 black box is the Arc2 Many, Many 944 guys use it and love it. I do remember when doing this research on the 924S (944 with skinny body), that the voltage was different, and that was why you couldn't just unplug and plug and play.
I would just use the LH and EZK computer and MAF from the 89 for this, but the LH died, the EZK is sold, and I need to either sell the MAF, or use it for something. I will eventually simply DTA the 81 as well, but it the mean time, this seemed an interesting idea....
12-03-2002, 11:57 PM
#7
Nordschleife Master
Thats cool.
I hope it works out. You may end up needing a EE to figure it out though. Not my department.
Viribus Units was the name of a World War I battleship built by the Austrian-Hungaryian Empire. It is a very powerful looking battleship. Something about it's class just looked "right". It's a unique name, easy for me to rember, so I use it alought.
I hope it works out. You may end up needing a EE to figure it out though. Not my department.
Viribus Units was the name of a World War I battleship built by the Austrian-Hungaryian Empire. It is a very powerful looking battleship. Something about it's class just looked "right". It's a unique name, easy for me to rember, so I use it alought.
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12-04-2002, 12:39 AM
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Digging through the big binders of collected info...I believe this is correct, but I disclaim responsibility for any magic smoke or burnt ECUs based on the below 
and certainly welcome corrections.
-Voltage range for the actual AFM pot, at pin 7 (return/modified voltage to ECU), should be at 3.7V +/- .1V with flap closed, transitioning to 1.6V +/- .1V at maximum deflection. I do not know if 3.7V is the full input voltage or is modified. Can't figure the current until the resistances are known...y'know, that Ohm guy and all...and no measurements are available.
Resistance range for pin 27, the NTC temp sensor, ranges as follows (all values doubled for meters stamped with mfg. date 042). Resistance is inversely proportional to temperature.
-10c = 8.26 to 10.56 Kohms
+20c = 2 to 3 Kohms
+50c = 760 to 910 ohms
Potential range from infinite resistance to dead short? Dunno.
Wonder how this specs out vs. the '44 meter? PorKen's link seems promising, and Split Second's ARC2A, (the ARC2 is NLA) seems to have a compatible voltage range and enough tweakability to theoretically put it in the usable range...after adding a TPS...
Oh well. It's fun to think about the conversion.
and certainly welcome corrections. -Voltage range for the actual AFM pot, at pin 7 (return/modified voltage to ECU), should be at 3.7V +/- .1V with flap closed, transitioning to 1.6V +/- .1V at maximum deflection. I do not know if 3.7V is the full input voltage or is modified. Can't figure the current until the resistances are known...y'know, that Ohm guy and all...and no measurements are available.
Resistance range for pin 27, the NTC temp sensor, ranges as follows (all values doubled for meters stamped with mfg. date 042). Resistance is inversely proportional to temperature.
-10c = 8.26 to 10.56 Kohms
+20c = 2 to 3 Kohms
+50c = 760 to 910 ohms
Potential range from infinite resistance to dead short? Dunno.
Wonder how this specs out vs. the '44 meter? PorKen's link seems promising, and Split Second's ARC2A, (the ARC2 is NLA) seems to have a compatible voltage range and enough tweakability to theoretically put it in the usable range...after adding a TPS...
Oh well. It's fun to think about the conversion.
12-04-2002, 11:42 PM
#9
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You know, I'll point out a few facts:
The Euro S made 300 hp from 4.7 liters with L-Jetronic. The S2 made 310 hp from the same displacement, and higher compression. The difference between the two engines? L vrs. LH Jetronic...
10 hp?
I should point out that your '81 makes 234 hp, so if you change this AND up your compression an according amount, you get 244 hp. I mean, after all that hassle...10 hp doesn't seem worth it.
To fully take advantage of this increased air flow, you should port/polish the heads, then add headers and a good exhaust.
N!
The Euro S made 300 hp from 4.7 liters with L-Jetronic. The S2 made 310 hp from the same displacement, and higher compression. The difference between the two engines? L vrs. LH Jetronic...
10 hp?
I should point out that your '81 makes 234 hp, so if you change this AND up your compression an according amount, you get 244 hp. I mean, after all that hassle...10 hp doesn't seem worth it.
To fully take advantage of this increased air flow, you should port/polish the heads, then add headers and a good exhaust.
N!
12-05-2002, 12:31 AM
#10
Nordschleife Master
Not exactly.
The Euro S went from K-jetronic, to LH-jetronic. It compleatly skiped the L-jetronic. In the process they also went from 10:1 compression to 10.4:1 compression. From that it gained 10 hp, and 28 ft/lbs of torque.
The US S used the L-jetronic, a restrictive intake, lower compression and less agressive cams. Switching to LH-jetronic would give small gains. Switching to the 84 EuroS intake would help alought. Switching to Euro cams would be nice. New headers would help.
With that combo, I'm guessing maybe 290 hp. Not the whole EuroS, but a decent improvement.
If you could add a supercharger aka the FAST kit, things would be even better.
Price tag, 5k or so before the blower?
The Euro S went from K-jetronic, to LH-jetronic. It compleatly skiped the L-jetronic. In the process they also went from 10:1 compression to 10.4:1 compression. From that it gained 10 hp, and 28 ft/lbs of torque.
The US S used the L-jetronic, a restrictive intake, lower compression and less agressive cams. Switching to LH-jetronic would give small gains. Switching to the 84 EuroS intake would help alought. Switching to Euro cams would be nice. New headers would help.
With that combo, I'm guessing maybe 290 hp. Not the whole EuroS, but a decent improvement.
If you could add a supercharger aka the FAST kit, things would be even better.
Price tag, 5k or so before the blower?
12-05-2002, 01:25 AM
#11
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Thread Starter
Normy....
I am actually installing headers and removing the Cat. The intake will eventually be worked on, but see....I already HAVE an LH MAF from my 89 SITTING there....So I was thinking of some ways to use it. If I could get 225 for that MAF, then I would drop this whole thing and spend the money on some drop links for the front of the car from 928Spec or Louie Ott. Or actually, I would spend that money on getting a really nice Y merge from Dr. Gas for the MSDS headers I have.
All this electronics stuff looks like I would eventually figure it out. The Arc2 is a great idea, and they are available all the time for 250 or so used. BUT, my wife drives this car. This is HER driver. So I can't have a system where she has to turn a few clicks here or there if it gets too chily out in San Diego after a night with the girls.
Anyway, I appreciate all those posts here. I HATE that barn door. Its works just fine though. Iwill eventually go DTA with this car as well, (www.dtafast.co.uk), and I won't have to worry about any of this.
Thanks again. Why did PorKen pull all of his posts?
I am actually installing headers and removing the Cat. The intake will eventually be worked on, but see....I already HAVE an LH MAF from my 89 SITTING there....So I was thinking of some ways to use it. If I could get 225 for that MAF, then I would drop this whole thing and spend the money on some drop links for the front of the car from 928Spec or Louie Ott. Or actually, I would spend that money on getting a really nice Y merge from Dr. Gas for the MSDS headers I have.
All this electronics stuff looks like I would eventually figure it out. The Arc2 is a great idea, and they are available all the time for 250 or so used. BUT, my wife drives this car. This is HER driver. So I can't have a system where she has to turn a few clicks here or there if it gets too chily out in San Diego after a night with the girls.
Anyway, I appreciate all those posts here. I HATE that barn door. Its works just fine though. Iwill eventually go DTA with this car as well, (www.dtafast.co.uk), and I won't have to worry about any of this.
Thanks again. Why did PorKen pull all of his posts?
12-05-2002, 01:54 AM
#12
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Just seeing if you were paying attention...
Actually I get carried away with the edit feature - my dumb questions, unanswered, deleted.
Which DTA are you looking at? The P8Pro?
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
Actually I get carried away with the edit feature - my dumb questions, unanswered, deleted.
Which DTA are you looking at? The P8Pro?
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
12-05-2002, 02:10 AM
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Brendan-
I like the notion of the DTA, but since you've been here a while, I'm sure you know how I feel about removing the cats~
I bet you're looking at more hassle than it is worth to make that MAF work with your car. But then again, I have so little time away from my friggin job these days that anything other than an oil change seems excessive...so maybe it is not such a hassle to you.
VIRIBIS [kewl screen name by the way-], if he has a flap type sensor, then he has the L-jetronic. This makes this a US version with 234 hp.
-In my VW days, I remember reading on a website and in literature that a standard VW 1.8 liter four cylinder's K or KE-jetronic had enough fueling capability for TWICE the power it developed...many people in California in the late '70's and early '80's bolted turbochargers to Rabbits, and via an Audi warm up regulator, fed adequate fuel to their now 180 hp engines.
Just make sure you hold the steering wheel firmly...!
It occurs to me however, that if Porsche could gain a large amount of power by substituting a MAF sensor for a flap type, then they would have done this when the L-jetronic appeared on 928's. There is something to gain for sure, but my point is that unless he has upgraded both the exhaust and intake [to include the long duration cams and big valve head of the Euro/ROW cars], then it is like opening wide all the doors linking sections of a long hall but one...airflow basically is decided by the weakest member.
N-
I like the notion of the DTA, but since you've been here a while, I'm sure you know how I feel about removing the cats~
I bet you're looking at more hassle than it is worth to make that MAF work with your car. But then again, I have so little time away from my friggin job these days that anything other than an oil change seems excessive...so maybe it is not such a hassle to you.
VIRIBIS [kewl screen name by the way-], if he has a flap type sensor, then he has the L-jetronic. This makes this a US version with 234 hp.
-In my VW days, I remember reading on a website and in literature that a standard VW 1.8 liter four cylinder's K or KE-jetronic had enough fueling capability for TWICE the power it developed...many people in California in the late '70's and early '80's bolted turbochargers to Rabbits, and via an Audi warm up regulator, fed adequate fuel to their now 180 hp engines.
Just make sure you hold the steering wheel firmly...!
It occurs to me however, that if Porsche could gain a large amount of power by substituting a MAF sensor for a flap type, then they would have done this when the L-jetronic appeared on 928's. There is something to gain for sure, but my point is that unless he has upgraded both the exhaust and intake [to include the long duration cams and big valve head of the Euro/ROW cars], then it is like opening wide all the doors linking sections of a long hall but one...airflow basically is decided by the weakest member.
N-
12-05-2002, 01:08 PM
#14
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Viribus, if/when you become a Rennlist Member you can use your namesake as your custom Avatar:
<a href="http://homepages.fh-giessen.de/~hg6339/Photos/ah/gBB_ViribUnitis.htm" target="_blank">http://homepages.fh-giessen.de/~hg6339/Photos/ah/gBB_ViribUnitis.htm</a>
Unfortunately, if you want to be historically accurate you will need to change your Forum name to 'Viribus Unitis'- the actual name of that Battleship.
Hey, do us a favour a put your real name in your signature - I think we can be on a first-name basis by now, don't you?
<a href="http://homepages.fh-giessen.de/~hg6339/Photos/ah/gBB_ViribUnitis.htm" target="_blank">http://homepages.fh-giessen.de/~hg6339/Photos/ah/gBB_ViribUnitis.htm</a>
Unfortunately, if you want to be historically accurate you will need to change your Forum name to 'Viribus Unitis'- the actual name of that Battleship.
Hey, do us a favour a put your real name in your signature - I think we can be on a first-name basis by now, don't you?
12-05-2002, 02:31 PM
#15
Nordschleife Master
Hay Randy.
Your correct the actual ships name was the K.u.K Viribus Unitis
Unforhcantly the board wouldn't accept spaces for some reason. That plus I forgot an I in the second part of the name. I called close enough close enough, and left it like that.
I could use it as my avator, assumeing I payed the fee. I hate fees, and am feeling awful broke. I just got informed that the christmass pressent I bought my girl freind last year wasn't enough to placate her parants. Which means that anytime I'm not around, she gets to hear them complain to her. Clearly this can't be allowed to continue. That combined with a few suprises on my 928, and the price of college, has left me in the red.
Maybe after Christmass?
The name's . I'm in Houston.
Your correct the actual ships name was the K.u.K Viribus Unitis
Unforhcantly the board wouldn't accept spaces for some reason. That plus I forgot an I in the second part of the name. I called close enough close enough, and left it like that.
I could use it as my avator, assumeing I payed the fee. I hate fees, and am feeling awful broke. I just got informed that the christmass pressent I bought my girl freind last year wasn't enough to placate her parants. Which means that anytime I'm not around, she gets to hear them complain to her. Clearly this can't be allowed to continue. That combined with a few suprises on my 928, and the price of college, has left me in the red.
Maybe after Christmass?
The name's . I'm in Houston.
Last edited by ViribusUnits; 02-18-2004 at 11:58 PM.