[Biff85ta]

I am in the beginnning stages of planning a 355 build for my 85 TA. It is a TPI car but 85 used a one year only slow ECM. I will be doing an ecm swap but am having trouble deciding if I should go with the 165 maf ecm or the 730 speed density ecm. Anyone got any suggestions or reasons for why to do one or the other.

 

[Red Devil]

Hell, don't you have to repin the harness either way? What is the specs on the build? If not too radical I'd say MAF, if really warmed over going to radical I'd say SD.

 

[Biff85ta]

Yeah I have to repin either way. I am kinda leaning towards speed density just because around here the ECM is easier to find. (727 weatherpack ecm's are all over the yards here) The specs on the build are not yet sorted out as I am building/buying parts as I can afford them. I just scored a set of LT1 PM rods over the weekend and an LT1 crank. I am considering building a stout bottom end and set of vortecs or something else low cost to get it up and running and then swapping in a better H/C combo later.

 

[Red Devil]

Then you should probably go with the SD stuff. Easier to find, and more support online as far as burning your own stuff too.

 

[Kenwood]

Speed density... Ill actually be selling a whole setup with plugs etc here in a couple of weeks...Ive got a 7730 ecu weartherpack plugs, and a gm map sensor..all you would need is a chip and carrier...

But no matter whose stuff you get> speed density all the way...the chip burning alone makes it worth it..

I had that POFS slow 85 computer in my vette>>>what a mess...sooo slow the diacom had to be slowed down for it to read right...LOL...

 

[C Murda]

Speed Density is the way to go if you're planning on keeping the factory style ECM. and if you say theyre easier to find where you are then what do you have to loose?

 

[PearlZ]

SD all the way

 

[Gregg1LE]

SD all the way

Gotta agree.

 

[talover111]

id go with maf myself

 

[five7kid]

MAF has the advantage of being able to accommodate changes without whining.

SD has the advantage of being able to handle higher power levels.

 

[89gta383]

I didn't pick up any power with my maf-sd swap.

The only thing you will gain is running a bigger tube to the throttle body which will get you a little more power. I am using a 4" tube now, and the maf would only let you use a 3"(or 4" necked down to the maf sensor then back to 4"). You will have to spend lots of time tuning either, so that's a wash.

It's still worth the swap to get rid of the maf and burnoff relays and the sensor though.:werd:

 

[five7kid]

I said SD is "able to handle handle higher power levels", not "makes" more power. No difference until other mods take you to MAF's limit.

 

[TPI PARTS]

Wanted to point out something that I often hear regarding the 1985 870 ECM. Slow just refers to the rate at which it sends diagnostic data. It doesn't refer to the speed at which the ECM itself operates, or that increasing the ECM's processor speed will be better.

By the way, if you are running a stock or aftermarket TPI setup, there really isn't many instances where running MAF would be a HP restriction as opposed to SD. If I remember correctly, the stock MAF with screens flows about 500 CFM.

Assume a best case scenario: 383 TPI engine, at 4800 RPM, operating at 100% volumetric efficiency.... it will consume 498.6 CFM of air. Increasing RPM on a TPI engine from this point on will lower volumetric efficiency, as power drops off.

However, if you had an aftermarket port injection intake like a Holley Stealthram, Miniram, or Superram, then yes, you would be limited at around 500 CFM with the factory MAF sensor, whereas SD would not be.