I thought about putting this in the boost forum - but its not for a j-body so I thought this might be more appropriate.
Alright I know what to do to turbocharge a speed-density engine (like everything in a j-body), but I just came across an 88 olds cutlas ciera(3.8L SFI) and I was wondering what needs to be different on a car with a mass air sensor(one I already replaced with a 85mm sensor BTW - since the old tiny factory one was bad anyways). I imagine I want the blow off valve on the charge pipe before the MAF no doubt, but I was wondering how the ECU takes boost since it has the MAF sensor to show additional airflow. Will the computer try to adjust for boost with additional fuel?(up to the limit of the injectors of course) Or am I gonna need to do basically the same stuff as I would on a speed-density engine? Do I still need check-valves etc?
Since this is a semi-rare car I'm sure I'm gonna need to make custom turbo headers etc. Anyone with experience on boosting an older 3.8(different engine than the 3800) would be especially appreciated.
I've never heard of this "part throttle" before. Does it just bolt on?
put the MAF in front of the turbo, and don't use a blowoff valve. recirculate it back into the system after the MAF but before the turbo. I think that's about it.
MAF/AFM before the turbocharger.
You can use an open vented BOV (rather than a closed recirculating) with a MAF/AFM system too, it'll just cause a momentary rich condition upon purge. Whether this affects you in a negative fashion, that's only going to be figured out by trying it.
Just use a diverter valve instead of a blow off valve. Hell mine and a few other people I know's DV is louder than alot of blow off valves anyway.
Alright thanks - but why does the MAF need to be before the turbocharger? Just seems odd too me. Is it's reading intended to be based off of regular atmospheric pressure or something?
I've never heard of this "part throttle" before. Does it just bolt on?
The air is going into the charger, doesn't matter if its compressed or not, the flow will be the same, but it's not designed to be pressurized, so it goes before.
DSMs use a MAF. It's easy, just behint the filter, before the turbo. Us a 1G DSM BOV and route it's output back to the intake, after the MAF, in front of the turbo. No problem. If you vent to air, you will run rich, like said above. If this is a drag car, that will hurt your times, if it's a street car, no big deal, 100ths don't usually matter on the street.
You may need to tune your MAF a bit, but it's really quite easy. To me, it's much easier than a MAP sensor equipped engine.
MAF sensors do not care about pressure except that they weren't designed for it. They measure air mass by couting vortexes in the flow (desity in patches). They work better when in before the turbo because they are more accurate with higher velocity air and the fact that they may blow apart if pressurized. They also don't care about temp. that, to me, is why they are better suited to turbo apps, but that's just me.
You will need to worry about plumbing (exhaust manifolds, intake pipeing), but more troublesome than that is the fuel issue. You non-turbo ECU is likely not going to deal with the high flow rates and may get into what is called "MAF overrun". I would suggest right now that you start saving your pennies for a good AFC, or maybe a stand alone system. You'll likely need bigger injectors, and a higher flowing fuel pump as well.
You could get some tips from other DSM tuners as we all use MAF sensors. We can get into MAF overrun with a turbo upgrade even though the ECU is designed for a turbo app.
PAX
Hahahaha wrote:DSMs use a MAF. It's easy, just behint the filter, before the turbo. Us a 1G DSM BOV and route it's output back to the intake, after the MAF, in front of the turbo. No problem. If you vent to air, you will run rich, like said above. If this is a drag car, that will hurt your times, if it's a street car, no big deal, 100ths don't usually matter on the street.
You may need to tune your MAF a bit, but it's really quite easy. To me, it's much easier than a MAP sensor equipped engine.
MAF sensors do not care about pressure except that they weren't designed for it. They measure air mass by couting vortexes in the flow (desity in patches). They work better when in before the turbo because they are more accurate with higher velocity air and the fact that they may blow apart if pressurized. They also don't care about temp. that, to me, is why they are better suited to turbo apps, but that's just me.
You will need to worry about plumbing (exhaust manifolds, intake pipeing), but more troublesome than that is the fuel issue. You non-turbo ECU is likely not going to deal with the high flow rates and may get into what is called "MAF overrun". I would suggest right now that you start saving your pennies for a good AFC, or maybe a stand alone system. You'll likely need bigger injectors, and a higher flowing fuel pump as well.
You could get some tips from other DSM tuners as we all use MAF sensors. We can get into MAF overrun with a turbo upgrade even though the ECU is designed for a turbo app.
PAX
Since this is an older vehicle, he should be able to get a chip burned to his specs for what he'll have done also
just build a megasquirt. only 250 unassembled....
