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Discussion Starter #1 (Edited)
I did a search and incorrectly started some posts related to Split Second in another thread (not dedicated to the subject of Split Second and their signal conversion and MAF/MAS-conversion products.)

In order not to hijack that thread (actually related to another engine management alternative), I'll post my findings here after meeting with Split Second today (as well as hopefully further details on the conversion - once I go through with it!)

The goal is to get rid of the small and restrictive OEM flapper/crapper AFM and install a hot-wire MAS-type pass through air meter AND to have it function stand-alone and fully independent (pushing the correct signals/voltage/resistance) for a no-fault operation and no CEL light activation on the stock Bosch Motronic ECU in my 3.45 litre 24 valve 164.
 

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Yes, do post. I have been reading their site and don't really understand the difference between their ARC2-A and PSC1-004. I was interested in the minimum needed to get rid of the AFM. I already have already purchased a Bosch MAF that is 3" diameter so I don't want to get their whole kit.
 

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Discussion Starter #3
From talking with them today, it sounds like the -004 is the one that we would both need! The thing for me (and you) to go and do now is to verify the voltage output of the particular MAS meters that we purchased... Where did you get your unit from? What brand/make/model did you get.

Mine came from some guys in England off of fleaBay - some name like Pinnacle??? maybe...?

They will likely be 0-5 volts (just like the OEM AFMs), but just check. We would then use the PSC 1 units for calibration.

349 dollars each.
 

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G'Day Guys,

Can it handle the 'burn off' pulse required by a hot wire sensor? Why not use a hot film sensor?

Let me know the part no. of your MAF sensor, if it's Bosch I might have the specs.
 

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Mine comes from a SAAB and is part number 0 280 213 012. I got it used locally for $40. Here is a pic with a cell phone camera. It's grainy, but many Bosch MAFs look identical.

Did you get an explanation from them what exactly is the difference between the two? Is it something you can explain here? What about connectors, would it be plug in, or do we have to find some connectors and do some splicing/wire colors to-from, etc?
 

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The burn off will not happen with anything but the motronic ECU. So you may risk the chance of deposits sticking on the wire. But if you can periodically clean the wire without destroying it, that should be fine too.
 

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So a Motronic ECU system with a flapper AFM is capable of supplying the burnoff cycle if converted to a MAF? How would it know to do that? I understand we would be fooling the ECU. It won't know the AFM is replaced. I would think the signal conversion/conditioning section would have to supply that. Am I wrong?
 

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Hot film

Hi all

There is a general consensus that hot film MAFs are more reliable than hot wire MAFs and don't require burn off. Not that I have any direct knowledge either way. They are just as inexpensive, or expensive if you buy them at the dealership. Watch out for the Asian junk, especially on ePay. Spec sheet is attached.

I'm told that the PSC1-004 is highly tunable and very reliable, although may be best sited outside the engine compartment to avoid heat and electrical interference. With the PSC1, you don't have to worry about which specific model of MAF you are using, however there is still the debatable issue of how best to measure air inflow temp. If someone has a working solution for that, I'd love to hear about it.

Regards
Simon
 

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Thanks Craig. Mine appears to be #3 on the spec sheet. Of particular note is that it doesn't appear to have the idle potentiometer circuit like #1 and #2. I wonder how important that is. My AFM has an adjustment but I don't know much about it. My twin spark is the first EFI I've owned.

It also appears to be a 5V signal, which is consistant with the AFM signal. The signal conditioner should be usable with this MAF.
 

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however there is still the debatable issue of how best to measure air inflow temp.
Ah, this is an interesting one.

The way I see it:

First off, you don't need to measure the temperature during engine operation as this is already done in the MAF. The ECU requires the temperature when using an AFM as the AFM only provides the volume of air not how much oxygen is in that volume. To calculate how much oxygen the ECU needs the temperature to calculate the density of the air, which with the volume, the ECU can calculate the density and mass then how much oxygen.

Since the output from a MAF (hot film or hot wire) IS mass, the ECU does not need to know the current temperature BUT because the calculation will still be made it needs a fixed value for temperature.

But what fixed value? That is the question.

Probably the current air temperature when calibrating your signal conditioner.

But then it might be something like the ISA 15°C or it might be some value Bosch picked. :confused:
 

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From the hot film MAF specs above, some appear to have a temp sensor and output. Would chosing one of those make the discussion moot?
 

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I don't think so, it's listed as an additional sensor.

Temperature has already been taken into consideration in the air mass calculation by the MAF. It cannot be re-used by the ECU.

Unless the signal conditioner actually converts mass to flow (which would also require the temperature).

Again, just the way I see it.
 

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Temp sensor

Hi Stefano

You are probably right, but the calibration of the temp sensor may differ between AFM and MAF. I simply don't know and haven't been able find out. As Craig says, it may not be important anyway, but an ambient air temp change from 10 - 40 deg celcius makes about a 10% difference in total measured oxygen supply.

The R4 software from Split Second doesn't account for that variable in a 3D map.

Can someone help on this?
Regards

Simon
 

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Ok, I actually went to the Split Second site and had a little read up on these devices ( ARC2-A and PSC1-004).

1/ Neither provides a burn off pulse for hot wire MAF's.

2/ Both devices provide a "temperature" output to the ECU (the installation note for the PSC1-004 state "it will tell the ECU that it is a constant 70°F". This is not the complete story though because it also mentions using a temp sensor for better cold start performance. This is a bit strange as we know that the ECU will vary the mixture based on what it sees at the air temp input. I don't get it.

Wait, a temperature sensor would allow the ECU to use it's cold start sequence.

But it would stuff up the other calculations?

I still don't get it.
 

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Hey John (jungle),

Do you copy this? Will you have another conversation with the folks at Split Second? The AFM of BMW that they are aiming at must have the same ECU or a small variation of it. There must be a logical explanation from them.

I don't mind losing the MAF I bought, it's a used unit I found locally. Well I could use it for a while; it probably will work untill the wire gets too dirty. Then I would have to go through another calibration process, but I would certainly learn a lot about these maps and stuff.

I'm really thinking of trying it soon, in the next few months. I had been in contact with a local BMW guy here that was working on one he claimed would be a low cost conversion. He was eager to try it out on an Alfa when I emailed him about my ECU. I was estimating he would sell his low cost unit for $200-400. He hasn't returned my emails in 8 months and this one is $339.

Say it all can be resolved - one should be able to buy

1) PSC1-004
1) Male pigtail to connect to the MAF and splice to the PSC1-004
1) Bosch Female pigtail to connect to the AFM connector on our harness

The picture of the unit doesn't show the ends of the wires, so I'm assuming they are bare.
 

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temp sensor

Hey, I'm just doing some brainstorming. Could a separate temp sensor be installed somewhere on the intake tract and wired to the the AFM pigtail? This means more parts and more wiring and would defeat some of the plug-n-play aspect of the Split Second attraction.

There is a kit for $30 at the bottom of the page here:

MiataRoadster : Engine Management
 
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