2nd gen MAF questions...

[Shadowfax]

Okay, so I've used the VPC, I've used the MAFT in draw and blowthru- but this is my car which I was 100% GIVEN so I'm working on a NO MONEY setup- using old parts I've got to try and make things interesting.

the car is a 91 Laser FWD Turbo- I've rebuilt the head with cleaned valves, new stemseals, new headgasket, lifters, t-belt, tensioner, etc.. 180 thermostat, EGR and smog gone, basically the car has a K&N drop in and that's it- it was on the car when given to me. Oh and my stock 190lph pump from the Stealth TT.

So I know the path I'm going to run, I know I'm going to stop around 300HP- this is a daily driver, not an all out- I've still got my 92 stealth TT and my 67 Dart 440 for having fun in - so keep in mind I know my limits- and budget is the key.

I've got some 3" mandrel 90's and some straight pipe laying around- I'll make my own O2 back exhaust- I'm likely going to put in a 16G or a smaller T3 whichever I feel like when the time comes... small FMIC, better IC piping... and I've got an old Rebic III extra injector box sitting. So I can take care of fuel when the time comes- the problem is airflow.

i've got the stock 3/S MAF, and I can get a 2nd gen DSM maf (if there is an actual difference internally- I've not checked fully) - and I'm thinking for cheapness and low buck it may be the way to go. It would flow enough air for my needs, and the rebic would supply the extra fuel.

HOWEVER- until I put on a larger turbo- explain this to me- I've got a stock setup for fuel/turbo- 14B with 450's. Why would the 2nd gen MAF that is put on cars with 450's not run correctly with 450's in a first gen? I've heard they run lean- because they flow more air- but I'm under the impression that if they will run fine on a 2nd gen with 450's that a 1st gen with 450's should result in the same type of fuel curves- meaning that the ECU should be able to compensate the difference in air being drawn in by the larger turbo.

I guess it just doesn't make sense to me that 450's being the same injectors in either, why you'd need to adjust what the ecu sees? 450's supply enough fuel for a 14B at part throttle, the airflow the ECU sees may be slightly higher, but that shouldn't cause a LEAN condition- the ECU should adjust up... is the airflow at part throttle THAT much greater that the ECU's correction factor can't make up for it?

And lastly- if I upgrade to the 2nd gen MAF but leave my stock injectors and my 190lph pump as it is- no SAFC - how many people have done mostly daily driving that way and had no ill effects?

I'll also be datalogging on and off to verify I'm safe

 

[DSM90AWD]

HOWEVER- until I put on a larger turbo- explain this to me- I've got a stock setup for fuel/turbo- 14B with 450's. Why would the 2nd gen MAF that is put on cars with 450's not run correctly with 450's in a first gen? I've heard they run lean- because they flow more air- but I'm under the impression that if they will run fine on a 2nd gen with 450's that a 1st gen with 450's should result in the same type of fuel curves- meaning that the ECU should be able to compensate the difference in air being drawn in by the larger turbo.

The 2Gs ECUs are calibrated for the 2G MAS and a +3psi base fuel pressure.

And lastly- if I upgrade to the 2nd gen MAF but leave my stock injectors and my 190lph pump as it is- no SAFC - how many people have done mostly daily driving that way and had no ill effects?

will likely run lean on the trims.. but should be ok.
FYI... I was pegging 119 trims on my 1990 with 2G MAS before I got my 550s and S-AFC. Was fast as hell though

 

[Shadowfax]

The 2Gs ECUs are calibrated for the 2G MAS and a +3psi base fuel pressure.

That's what I don't see i guess- the 2nd gen ECU is calibrated for the ability to see more air, but there actually wouldn't be more air since the turbo is smaller and pretty much nothing flows as well on the 2nd gen intake side? However the base +3psi is a slight difference, perhaps enough that the 190lph hotwired pump could make up for it.

will likely run lean on the trims.. but should be ok.
FYI... I was pegging 119 trims on my 1990 with 2G MAS before I got my 550s and S-AFC. Was fast as hell though

119 trims don't sound wonderful, however I am not likely to do a lot of play until I get the rebic in anyway...

So I may be safe...

Then one more question I haven't found the answer to - the 3/S and 2nd Gen DSM maf are physically the same- how about internally. I have my stock 92 3/S TT sensor just sitting around... is it able to work, or do I need to find a 2nd gen dsm?

 

[DSM90AWD]

That's what I don't see i guess- the 2nd gen ECU is calibrated for the ability to see more air, but there actually wouldn't be more air since the turbo is smaller and pretty much nothing flows as well on the 2nd gen intake side? However the base +3psi is a slight difference, perhaps enough that the 190lph hotwired pump could make up for it.

I think you are overthinking this. If the 1G MAS and 2G MAS both output the same Kharman reading (say 1000Hz).. the actual airflow passing thru the 2G MAS notwitstanding any other factors (VE, Turbo..etc) will be ~20% greater. Remember the Kharman chambers on both units are a diff size as are the chambers that bypass it (i.e. not directly read).

This is why by adding 550 injectors (~20% larger than 450s) approx negates the extra air.

Another thing that can be done at the ECU level (via EPROM mod) is to change the Global Fuel varible so to add 20% more fuel accross the board to compensate for the larger MAS.

Then one more question I haven't found the answer to - the 3/S and 2nd Gen DSM maf are physically the same- how about internally. I have my stock 92 3/S TT sensor just sitting around... is it able to work, or do I need to find a 2nd gen dsm?

They're the same.

 

[Shadowfax]

I think you are overthinking this. If the 1G MAS and 2G MAS both output the same Kharman reading (say 1000Hz).. the actual airflow passing thru the 2G MAS notwitstanding any other factors (VE, Turbo..etc) will be ~20% greater. Remember the Kharman chambers on both units are a diff size as are the chambers that bypass it (i.e. not directly read).

Okay, that starts to make some sense... I've been on some light meds (just got wisdom teeth cut out) and so I figured it was understandable, but perhaps not quite by me

I pulled the 3/S MAF outta hiding yestreday, I guess I'll work on a tech article by installing it

I also installed a 2nd gen TB elbow - that's gotta help