Check your AFM boys and girls (re. hi rpm miss)

#39

[quote=“Ranger” post=65204]You should be able to tell if it’s working or not using the test that the 944 website talked about. It’s getting one that hasn’t had it’s spring adjuster dicked with that’s the trick. I wish I had one that I knew for a fact was never dicked with. I think that getting the spring adjuster back to it’s orig position would be hard. What we need to do is to get out hands on a new one and see if there is a way to positively identify the OEM location of the spring adjuster wheel.

I think that the Palacios have new AFMs. At CMP next month I’ll ask them if I can’t pop the top off of one and look at the adjuster wheel. There’s a little tab that holds the spring in place. By noting the location of that tab we might ID where the adjusting wheel is set at the factory.[/quote]

I bought the reman units that Pelican sells (over a year ago…). I think they’re rebuilt by Python. Lower cost if you send a core back so keep yours if you go that route. We haven’t touched the covers, they’re still sealed with silicon.

#40

[quote=“tpr jules” post=65218][quote=“Ranger” post=65204]You should be able to tell if it’s working or not using the test that the 944 website talked about. It’s getting one that hasn’t had it’s spring adjuster dicked with that’s the trick. I wish I had one that I knew for a fact was never dicked with. I think that getting the spring adjuster back to it’s orig position would be hard. What we need to do is to get out hands on a new one and see if there is a way to positively identify the OEM location of the spring adjuster wheel.

I think that the Palacios have new AFMs. At CMP next month I’ll ask them if I can’t pop the top off of one and look at the adjuster wheel. There’s a little tab that holds the spring in place. By noting the location of that tab we might ID where the adjusting wheel is set at the factory.[/quote]

I bought the reman units that Pelican sells (over a year ago…). I think they’re rebuilt by Python. Lower cost if you send a core back so keep yours if you go that route. We haven’t touched the covers, they’re still sealed with silicon.[/quote]
I just reread the AFM page on the 944 website and if that guy is right then it won’t do us any good to check the OEM position of the wheel. He says that the AFM’s circuit board is calibrated to the specific spring wheel setting on that AFM. That being said, if you buy my theory that started this thread, then a lean mixture at high rpm would indicate that the spring is set too loose. With a bit of trial and error, one could get their AFM spring adjuster dial in the right ballpark if they had F/A ratio info and gave the DME time to adjust fuel trim after each change to the spring adjuster.

Of course getting F/A data for most folks means multiple trips to the dyno. Or, if you’re looking for a project, you could copy my F/A meter-on-the-dash goodness.

#41

Given what we know about how these AFMs are calibrated at the factory after assembly using a laser to etch the circuit board, can we have confidence that the reman units are properly calibrated? I would sure hope that they are since these surely aren’t being made anymore.

The process of a laser etching the circuit board in order to calibrate the resistance relative to the force on the flapper might have seemed to be cutting edge when the process was no doubt designed around 1980, but by today’s standards it’s a joke. Maybe that 944 guy has some thoughts on this. Hmm.

#42

My well intentioned dyno “expert” changed my spring wheel to richen up the mixture. Before changing he did paint mark the original position. I have since adjusted back to that psoition. Can I assume that the AFM is calibrated back to the stock position? Or am I missing something here?

#43

I think you’re good.

Subject change: I came up with a scheme that might allow a person to get their AFM back to something approximating the factory calibration. I’m going to bounce the idea off of the 944 AFM guy before I take the idea any farther tho.

#44

OOOh! I smell a cottage industry!

#45

So, new member here, not a specE30 guy but I race my E30 325i in ITS with Midwestern Council…

I’ve been tracing a high RPM WOT throttle condition for quite sometime - I have just finnaly installed a in vehicle fuel pressure gauge to monitor that this upcoming weekend.

I came upon this thread as for the last year in between every race I spend hours scouring the internet looking for something that might solve my problem.

So I decided to test my AFM - both ways… resistance, and the 944guys way.

Upon popping my cover I noticed 4 grooves so that tells me this AFM has been tampered with before. There was also a very sad looking mess towards the WOT throttle side of the circuit board where a lot of the material had been removed.

While doing the voltage test I had a very smooth rise that was repeatable, however towards the very end of the sweep (just entering into this heavily worn area) the voltage spiked from the ~7V to ~8V and then flat lined. (I was using a 9V battery so the output is different then the 0-5V like the DME sees.

So I thought what the heck, I’ll try checking resistance to see if I have the same pattern everyone on here described.

I had a steady linear increase across the range until the “bad spot” again. When entering the bad area with resistance, I instantly popped to 1, and then back down to a linear data point that made sense, and then as others had seen I dropped right at the end back down to a resistance value that matched partially open throttle.

So I think I have located a potentially bad spot in my AFM circuit board in the last 1/16-1/8" of sweep.

That said I have gone and purchased a reman unit from Advanced Auto parts produced by Borg Warner - they also have one from A1 Cardone (massive reman company) but I have a bit more faith in the BWD electronics.

Total cost is 117 if I dont return my core, - 72 bucks with exchange.

I will report back on my findings after testing that unit, as well as running the car this weekend at Blackhawk Farms.

Good luck guys!

#46

That’s all great, but what do I have to do to get you to run some SE30 with us?!:evil:

#47

[quote=“tschreyer” post=65482]So,
That said I have gone and purchased a reman unit from Advanced Auto parts produced by Borg Warner - they also have one from A1 Cardone (massive reman company) but I have a bit more faith in the BWD electronics.

Total cost is 117 if I dont return my core, - 72 bucks with exchange.

I will report back on my findings after testing that unit, as well as running the car this weekend at Blackhawk Farms.
[/quote]
That’s by far the best price I’ve ever heard, thanks for sharing.

#48

Tell ya what, I’ll come run with you in SE30, you just can’t tech or dyno my car :whistle:

#49

That sounds like a great price for a reman AFM. I might get one before my next trip to the dyno.

#50

Tell ya what, I’ll come run with you in SE30, you just can’t tech or dyno my car :whistle:[/quote]

Tell ya what, I’ll give you the winter to sort out your tech problems, but in the meantime, come on out and see the fun we’re having!!

#51

The invitation of course goes both ways… but you guys can come run ITS legally any day :stuck_out_tongue:

Ask Tom Tiede about our group, I’m sure its equally as fun as the NASA Midwest folks… I really do hope to get out and enjoy a NASA event sometime this summer.

Great shot attached of the start of what seems like an E30 that got in the wrong run group… thats my lone E30 trying to get thru the pack of Mia’s and Tia’s

Photo courtesy of Larry Best of Chicagoland Sports Car Club.

#52

I’m very familiear with you guys, just can’t fit you in the schedule. How competitive would a SE30 be in ITS anyways?

I’m sure our paths will cross soon.

#53

In the midwest I would think the car would be fairly competitive… in the Southeast and Northeast where IT is crazy fast and you have ARRC cars to contend with, I’m doubtful of a SE30’s competitiveness.

Unfortunately ITS only sees 5-7 cars on average here in the midwest.

ITA usually has a large car count as the spec miata guys run dual classes and thats where their car fits.

That holds true for MCSCC or SCCA.

#54

Update: I installed the new Borg Warner reman piece for this weekends sprint races at Blackhawk Farms. Car ran great - no high RPM misfire and pulled excellant all the way to the rev limiter (7000RPM on my MarkD chip).

The new piece bench tested correctly as per the 944guy’s proceedure, and it also showed a loss in the resistance as others have discovered.

Attached is a photo of the old piece showing the strange spot on the end of the AFM circuit board. As the pickup swept into this range it started to do odd things with both voltage and resistance (see earlier post for details)

#55

When we experience issues like these the first thing we do is swap a known good AFM off one of our other cars onto the trouble maker.

If the issue is resolved we’ll normally try a re-man unit; but lately I’ve taken to buying new in box Bosch Units (via the Bosch Pn: 0 280 202 082) from BMA; they were $350-400 from memory, supplied in genuine Bosch box with genuine Bosch plastic bag. Clean, never opened.

Bolted them on and the cars run perfectly. Problem solved.

#56

[quote=“djs325” post=65992]When we experience issues like these the first thing we do is swap a known good AFM off one of our other cars onto the trouble maker.

If the issue is resolved we’ll normally try a re-man unit; but lately I’ve taken to buying new in box Bosch Units (via the Bosch Pn: 0 280 202 082) from BMA; they were $350-400 from memory, supplied in genuine Bosch box with genuine Bosch plastic bag. Clean, never opened.

Bolted them on and the cars run perfectly. Problem solved.[/quote]
Do you perceive the re-man units to be properly calibrated? It would be easy to imagine some outfit disassembling old AFMs, cleaning the housings, slapping in new parts but not doing the careful laser-etch calibrating that Bosch did.

#57

That is the kicker isn’t it - with a reman unit you can never have quite the same faith. The units sourced direct from Bosch have been bolt-in & leave. If you need to fine tune for A/F ratio then so be it; but no other adjustment or fiddling required!

[quote=“Ranger” post=66005][quote=“djs325” post=65992]When we experience issues like these the first thing we do is swap a known good AFM off one of our other cars onto the trouble maker.

If the issue is resolved we’ll normally try a re-man unit; but lately I’ve taken to buying new in box Bosch Units (via the Bosch Pn: 0 280 202 082) from BMA; they were $350-400 from memory, supplied in genuine Bosch box with genuine Bosch plastic bag. Clean, never opened.

Bolted them on and the cars run perfectly. Problem solved.[/quote]
Do you perceive the re-man units to be properly calibrated? It would be easy to imagine some outfit disassembling old AFMs, cleaning the housings, slapping in new parts but not doing the careful laser-etch calibrating that Bosch did.[/quote]

#58

[quote=“djs325” post=66324]That is the kicker isn’t it - with a reman unit you can never have quite the same faith. The units sourced direct from Bosch have been bolt-in & leave. If you need to fine tune for A/F ratio then so be it; but no other adjustment or fiddling required!
[/quote]
The problem is that it’s the well-intended attempts to tweak the AFM in order to fine tune the A/F that screws them up. Once the AFM’s spring tension has been screwed with, there’s no way to be sure of getting it back to the factory calibration.