Bigger AFM ..... need part No ...
Discussion
starmist said:
I understand you can't fit the Bosch one without a Mark Adams chip - it's incompatible with the standard chip!
Not knowing a great deal about these particular AFM's,
it is possible that the 5AM standard AFM gives out an analoque signal whereas the Bosch AFM will be digital hence the need for a wiring and chip change which would be done before the remap(what i said earlier).
The chip does not need to be a Mark Adams one either.
HarryW said:
AFAIK the 20AM is still analogue however it doesn't have the trim pot so one is put in the loom acrossthe wires to provide that signal for the ECU. The scaling (voltage output for volume of air in) is different hence the re-map.
Harry
Yes Harry just like the 5AM but the 20AM is different to the Bosch unit. Anything put across the wires to a 20AM unit will be to stop the power surges.
Had 3 that failed within a few hundred miles of each other, not funny at £300 a go, then Mark Adams wired up a small box of tricks for me to fit in line with the AFM.Problem solved, then John Eales told me that the standard AFM was better for top end power.
Mine is a 20AM, it was supplied by Mark Adams complete with a fitting kit and instructions. Not particularly hard to fit but not a plug-in replacement. As Harry says, the calibration is different so a different map is required, and it also has an external calibration resister instead of an external one.
The retail of £180 for the Bosch is actually quite good, the margin from trade price is very small, but i understand why you might question paying that for a piece of plastic, typical automotive issue, they probably only cost a couple of quid to make .
My general advise is: only fit a meter if the car is going to be mapped properly otherwise the benefits might be negligable, when properly mapped they benefit the whole rev range, i wouldn't bother on a 4.0L though.
Tim
My general advise is: only fit a meter if the car is going to be mapped properly otherwise the benefits might be negligable, when properly mapped they benefit the whole rev range, i wouldn't bother on a 4.0L though.
Tim
Aaron C. Reskew said:
...... then John Eales told me that the standard AFM was better for top end power.
I understood that the main adavntage of the 20AM over the 5AM is that it can handle a great volume of air mass.
The 5AM is topped out i.e. the analogue scaled output can be saturated at high rpm with the bigger engines. The 5AM on mine maxes out(5V) just before peak power, the scaling above that point can be extrapolated by the likes of MA in the ECU Air mass (load) against rpm map
. Any engine much bigger i.e. a tuned 5ltr will top it out a lot sooner, therefore more of the map has to be 'extrapolated' (educated guessing 
). I also understood the 20AM physically flowed more air by virtue of its bigger bore.
Harry
Aaron C. Reskew said:
I know the 20AM unit is not as good as the Bosch one.
Just see what the tuners are using at the moment for your answer.
what is that then , the bosche equivilent to the 5AM . seriously if you have na inside line let me know, if there are reasonable gains to be had I'll have them
. Harry
For the cost of bigger this and electric add-on that and remap, why not just junk the afm and fit a load v revs aftermarket ecu with mapped ignition aswell? you guys seem to do stuff the hard way to me .. it'll work out cheaper in the end aswell cos if yuo go very wild on your engine yuo'd want mapped ignition anyway and the faithful old clockwork lucas doesn't give you that, you currently have to buy an add-on omex or similar and have that mapped anyway! It just all makes no sense at all.
junk the lot, go full omex, dta, emerald, even megasquirt if you like getting your eyes full of solder.
junk the lot, go full omex, dta, emerald, even megasquirt if you like getting your eyes full of solder.
Amazing the debates you can spark with a simple request ...
For the record .... I am keeping an original plenum, just increasing the throttle size to 72mm, I will upgrade the trumpet base in addition to this along with a smooth bore induction hose ..... ACT doing well out of me so far.
To make the most of these I will need to stump up for MA's chip and remap, and then the bigger restriction in the induction side is the AFM ... hence looking for the part number, at the moment I am collecting bits at a time until I am ready financially and time wise to put it all together .....
I do not want a wild engine, don't want the carbon as I want to keep the car looking vaguely standard with it being an SE, fully programmable ECU would be great if I were running 404 cam, triple plenum etc etc .... but all I'm trying to do is improve on the original, without going to far ...
... For the record .... I am keeping an original plenum, just increasing the throttle size to 72mm, I will upgrade the trumpet base in addition to this along with a smooth bore induction hose ..... ACT doing well out of me so far.
To make the most of these I will need to stump up for MA's chip and remap, and then the bigger restriction in the induction side is the AFM ... hence looking for the part number, at the moment I am collecting bits at a time until I am ready financially and time wise to put it all together .....
I do not want a wild engine, don't want the carbon as I want to keep the car looking vaguely standard with it being an SE, fully programmable ECU would be great if I were running 404 cam, triple plenum etc etc .... but all I'm trying to do is improve on the original, without going to far ...
It would be interesting to hear what Mark Adams has to say about this. I know he's got a vested interest because he runs a business mapping and tuning hotwire ECUs, but he's somebody I would trust to be impartial.
From what I remember of previous discussions with him, the MAP based systems are much less sophisticated in terms of metering compared to a true MAF based system. I'm not sure whether this means the end result will be a less tractible engine, or just that it will take more work to set up and be affected more by future engine changes. The fact that production EFI systems tend to use the MAF approach suggests to me that it is indeed a superior solution.
And that makes sense to me. At the end of the day you want to add fuel in proportion to air, so it seems obvious to measure the amount of air, and add fuel to match.
The relationship between manifold pressure and mass air flow is a very indirect one. You *can* work out roughly how much air is going in if you've measured the engine previously under identical conditions, but it seems to be making life unecessarily difficult, and is not a very robust solution (in that small changes to the engine will make a significant impact to the tune).
From what I remember of previous discussions with him, the MAP based systems are much less sophisticated in terms of metering compared to a true MAF based system. I'm not sure whether this means the end result will be a less tractible engine, or just that it will take more work to set up and be affected more by future engine changes. The fact that production EFI systems tend to use the MAF approach suggests to me that it is indeed a superior solution.
And that makes sense to me. At the end of the day you want to add fuel in proportion to air, so it seems obvious to measure the amount of air, and add fuel to match.
The relationship between manifold pressure and mass air flow is a very indirect one. You *can* work out roughly how much air is going in if you've measured the engine previously under identical conditions, but it seems to be making life unecessarily difficult, and is not a very robust solution (in that small changes to the engine will make a significant impact to the tune).
HarryW said:
I know the 20AM unit is not as good as the Bosch one.
Just see what the tuners are using at the moment for your answer.
seriously if you have na inside line let me know, if there are reasonable gains to be had I'll have them
Harry
The 20AM AFM is made by Sagem and fitted as standard kit to 4.6 GEMS Range Rovers. Bosch (mind the spelling) is Bosch and from what i've heard from Mark Adams, it is better than the Sagem one.
joospeed said:
For the cost of bigger this and electric add-on that and remap, why not just junk the afm and fit a load v revs aftermarket ecu with mapped ignition aswell? you guys seem to do stuff the hard way to me .. it'll work out cheaper in the end aswell cos if yuo go very wild on your engine yuo'd want mapped ignition anyway and the faithful old clockwork lucas doesn't give you that, you currently have to buy an add-on omex or similar and have that mapped anyway! It just all makes no sense at all.
junk the lot, go full omex, dta, emerald, even megasquirt if you like getting your eyes full of solder.
My thoughts entirely if you are going for all out performance. (Joolz did you get that email?).
The only trouble is fitting and mapping say an Emerald or DTA etc for example will mean lots of wire chopping and more time on the rollers.
Mark has lots of experience with the RV8 and has chips pre mapped for most of the work he needs to do on a particular engine. For the most part the result is quite satisfactory for most people.
I think the only way you can do it cheaper or even equivalent in cost, is to have a mappable ECU from whoever it might be and have loom connector adaptor plugs and an assortment of part finished chips at the ready.This means spending a lot of time to start with on whatever engine(s) you intend to work on.
With the way mappable ECU's are going i would think that there might come a day when engines will map themselves to a point as the number and complexity of sensors is increasing.
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