Converting to speed density?

[REX-RACER]

Been reading up on tuning and just finished a section on MAF sensors vs MAP sensors. Frankly it seems like MAP sensors are a lot easier to work w/ and you don't have worry possible intake restrictions of the MAF housing, the ever present possibility of "pegging" the MAF in hi-po applications necessitating the need to look for bigger MAFs at $200+ dollars a pop or mess around w/ MAF extenders.

Just curious if anyone has every tried or successfully to switch over one of the 96+ mod motors to run speed/density instead of mass/air?

 

[01yellercobra]

I think you'll have to switch over to a stand alone system like FAST in order to switch to speed density. I did some light reading on tuning speed density and it seems like more of a pain. You have more tables to tune since the computer doesn't actually know how much air the engine is ingesting. It "guesses" by throttle position and rpm.

 

[REX-RACER]

I think you'll have to switch over to a stand alone system like FAST in order to switch to speed density. I did some light reading on tuning speed density and it seems like more of a pain. You have more tables to tune since the computer doesn't actually know how much air the engine is ingesting. It "guesses" by throttle position and rpm.

Thanks for the response! :thumbsup:


Yeah, I think a new ecu is a given if you make this kinda switch, but that seems no more outlandish to me those handful of folks who have converted mod motors to run w/ carbs. It just seems to me this might be a viable alternative say like if you were doing a motor swap into a Fox body and were gonna have to come up w/ an ecu anyways?

As far as how complicated tuning speed/density goes I'm not well versed in it as I haven't really finished the book yet . . . :-D

 

[HotStart]

Been reading up on tuning and just finished a section on MAF sensors vs MAP sensors. Frankly it seems like MAP sensors are a lot easier to work w/ and you don't have worry possible intake restrictions of the MAF housing, the ever present possibility of "pegging" the MAF in hi-po applications necessitating the need to look for bigger MAFs at $200+ dollars a pop or mess around w/ MAF extenders.

Just curious if anyone has every tried or successfully to switch over one of the 96+ mod motors to run speed/density instead of mass/air?

Both have their pros and cons, but the cost of running a SD standalone is much greater than buying a properly sized mass air meter.

You have more tables to tune since the computer doesn't actually know how much air the engine is ingesting. It "guesses" by throttle position and rpm.

You're describing an Alpha-N air model. A Speed Density system does not use throttle position any differently than a Mass Air system. Speed Density knows the mass of air using the PV=nRT formula.

 

[REX-RACER]

Both have their pros and cons, but the cost of running a SD standalone is much greater than buying a properly sized mass air meter.

Thanks for the response.

I get that "switching" from M/A to S/D probably has a lot of unnecessary costs and burdens, but what if you were doing a crate motor swap and had to come w/ a new ECU, wiring harness and tuning solution from scratch anyways? Would the costs of fashioning an S/D system for a mod motor really be any greater than starting from scratch w/ a M/A set up? Are the inherent draw backs of S/D any more detrimental than a M/A set up if you're going from scratch?

 

[HotStart]

Thanks for the response.

I get that "switching" from M/A to S/D probably has a lot of unnecessary costs and burdens, but what if you were doing a crate motor swap and had to come w/ a new ECU, wiring harness and tuning solution from scratch anyways? Would the costs of fashioning an S/D system for a mod motor really be any greater than starting from scratch w/ a M/A set up? Are the inherent draw backs of S/D any more detrimental than a M/A set up if you're going from scratch?

The whole cost debate really depends on the individual setups. You can spend $4000+ on a mid-high end stand alone, or you could be doing a megasquirt system for under $1000. Same thing with a mass air system. To buy a complete DBW ecu/harness and mass air system for a new, high hp build could be pretty expensive. To buy a used harness/ecu/meter from a foxbody will be inexpensive.

Probably the biggest advantage SD has comes from not worrying about MAF turbulence from bends/ BOV recurculation. If I am not tuning the car on a loaded dyno (ie the street or most dynojets), then I would rather tune a mass air system because it can be near impossible to dial in every cell in a VE chart without load control. In the end, you'll find that since both air models will do the job provided they are setup correctly, choosing an ECU setup for a new build usually comes down to you budget and the capability of the ECU itself, rather than choosing to have speed density or mass air.

 

[REX-RACER]

The whole cost debate really depends on the individual setups. You can spend $4000+ on a mid-high end stand alone, or you could be doing a megasquirt system for under $1000. Same thing with a mass air system. To buy a complete DBW ecu/harness and mass air system for a new, high hp build could be pretty expensive. To buy a used harness/ecu/meter from a foxbody will be inexpensive.

Probably the biggest advantage SD has comes from not worrying about MAF turbulence from bends/ BOV recurculation. If I am not tuning the car on a loaded dyno (ie the street or most dynojets), then I would rather tune a mass air system because it can be near impossible to dial in every cell in a VE chart without load control. In the end, you'll find that since both air models will do the job provided they are setup correctly, choosing an ECU setup for a new build usually comes down to you budget and the capability of the ECU itself, rather than choosing to have speed density or mass air.

Good points, thanx! :thumbsup: