164 24v stock ECU & ? other AFM

[jimmystratos]

Is there a way of replacing the flapper AFM and still using the Motronic ECU, or would I need to go for a full programmeable one?

[CorseChris]

Weren't the 24V ECUs all hot wire AFM Chris? Mind you, looking at the figures from my 12V RR session, the flapper maybe isn't as restrictive as we thought it might be. It didn't cross my mind until now, but I could have taken one along and fitted it temproaraily to see jsut how much difference it makes. I'll try(!) to remember to do this next time I take the car to the RR. We wouldn't have had the time at the last session anyway, but I can do it next time.

[AR4me]

Earlier 24v had flap AFM (like all US 24v models), while later 24v had hot wire AFM.
Jes

[jimmystratos]

Quote:

Originally Posted by CorseChris Weren't the 24V ECUs all hot wire AFM Chris? Mind you, looking at the figures from my 12V RR session, the flapper maybe isn't as restrictive as we thought it might be. It didn't cross my mind until now, but I could have taken one along and fitted it temproaraily to see jsut how much difference it makes. I'll try(!) to remember to do this next time I take the car to the RR. We wouldn't have had the time at the last session anyway, but I can do it next time.

[CorseChris]

Ah, OK - wasn't sure. What's the c.s.a. of an inlet runner compared to the AFM?? That'll be the limiting factor won't it?

If we can find some data on the 2 AFMs & ECUs, that might give us a clue if they would be interchangeable....I'll see what I can dig up....so, can anyone tell me definitively which ECU goes with which AFM type please?

[jimmystratos]

the inlet runners are going to be approx 1275sq.mm each. There'll be flow in more than just one at a time though.
Do you need some numbers off the ECUs?

[CorseChris]

True..it'll be more than 1 at a time, but not as much as we might think. Complicated, but it'll relate to cam overlap and durations. Wouldn't know where to start to work it out, but I will do that notion of putting a flappy AFM on my car next time it's on the rollers.

If you have ECU numbers for the early & later types, that would be a good start. The flappy AFM is simply a pot (with a few tweaks), the hot wire AFM is a more complex device, but could well have been designed to provide the same output signal to the ECU. I've never investigated this before.

[junglejustice]

I am working on that challenge right now for my US spec 1995 164 LS 24 valve - it still has the flapper AFM. I purchased a generic hot-wire pass-through MAS sensor tube and will be running the UniChip product from South Africa to deal with the added fuel and timing requirements of the 3.45 litre rebuild.

You need a converter box of sorts that will convert the digital frequency from the hot-wire to the analogue voltage that the stock AFM is going to be looking for. I thought about upgrading to the European-spec 164 Q4 all-wheel drive electronics since that runs a MAS tube (on Bosch version 3.7 I think it is), but the ECU is different, the harness pin-outs are different so I scrapped that idea.

The UniChip is a piggy-back and a seperate issue - worth mentioning though since it goes with the conversation about keeping Bosch Motronic's relatively smooth maps and cold-start programs, but gaining programmability. With the removal of the restrictive flapper AFM, it is conceivable that the motor could use a bit more fuel and you can always use a bit more timing.

Add some of our GTA Stage I or GTA Stage II cams, 44mm GTA/Q intake runners and now the UniChip becomes even more important. I don't sell the product, but I love it - it works. With the Stage I cams, the Q/GTA runners and the UniChip my otherwise stock standard 164 LS (Super) kicked out 212-213-214 horses at the wheels through an automatic slush-box and still with the flapper-crapper installed!

[jimmystratos]

I pass on the following from another Alfisti fiddler.

Quote:

I can say for certain that you cannot use the wrong type of flow meter with a standard ECU that was not meant for it. The newer (and much better) hot-wire types need a different supply and the output signal is not directly compatible with the potentiometer from a flap type. (The hot-wire types do not restrict the air flow like a flap does, but the signal is much harder to interpret.)

[junglejustice]

It is very do-able though! Just need somebody - better than me - with electronics...

[CorseChris]

Thanks JJ, Chris. Saves me some effort reinventing the wheel! Frequency to voltage is easy enough....but getting the right conversion law could be a tad tricky I suspect. Best way would be with a flow bench I suppose. Anyone got one handy along with a couple of AFMs?? Plot the relationships of flow to volts/frequency and I'll see if I can come up with a converter.

[jimmystratos]

I've got a spare flapper AFM that I can lend for the cause Chris. Sorry, no flow bench, and I can't think what medical equipment i could cannibalise either!

[CorseChris]

I've a surplus of flappy AFMs myself. Dont have a hot wire type, nor a flow bench. I know someone who does...but suspect they won't be interested in this particular topic. Another path might be manufacturers data for the devices?? Anyone??

[Barryh]

Guys,No need to re invent the wheel here..

www.mapecu.com

Been using it for years.

[jimmystratos]

Looks like hot wire AFMs are voltage too - easier to convert?
I wouldn't have thought that I need all the other gizmos these provide.