i wanted to know what an SD was cause some guy was talking about replacing his maf with an sd and i just wanted to know what they were an how much they were

 

SD is short for "Speed Density". Its a method of calculating proper Air Fuel ratio. SD computers use a MAP (vacuum) sensor and a TPS (throttle position) and RPM to ASSUME what the engine is doing, and what it will need fuel wise.

MAF systems use an air flow meter (MAF) to measure actual incoming air to know how much fuel to add.

Each system has it pros and cons.

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ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

 

As usual, GMTech gave you a pretty good explanation. I'm sure he can provide you with much useful information if you ever decide to do the swap yourself, as he has converted his T/A to SD TPI.

I would just like to add one thing. SD TPI also uses and Intake Air Temperature sensor (IAT) to determine intake air temperature, and adjust for air density as necessary.

MAF systems are more accurate in that they measure intake air by the gram, rather than hypothesizing intake air by taking into account different engine parameters such as:

-IAT
-RPM/Load
-Manifold Vacuum
-TPS
-calculated vacuum leaks including IAC

HTH

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-Jason M. 1991 Camaro Z28
"Shampoo is better, I go on first and clean the hair."

 

well what do i need and where could i get it to change to an sd

 

Try street and performance. That is where I got mine from. I don't know their phone number off the top of my head but it should be on their internet address. www.tunedportinjection.com
I believe that's it.
bsa

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"If they do not run, Then they will die." - Stonewall Jackson

'87 IROC, 355 TPI, Converted to SD, 700R4, B&M Megashifter, 3.42, Trick Flow Twisted Wedge Heads, Comp Cam, Comp 1.6 Rockers, Lucas 23# injectors, Edelbrock headers, Flowmaster 3'' exhaust, gutted cat, Mallory coil, Mallory HyFire IV ignition box, Mallory Sidewinder 8mm wires, Autolite platinum plugs, K&N filters, Transgo Performance Shift Kit, Corvette Servo, 2,000 Stall Torque Converter

 

http://www.tunedport.com/

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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
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Thats great, but if your poor like me, you can buy used parts. I have been collecting parts for 6 months untill I decided I was ready to do the "swap". I bought a TPI assembly off of ebay along with the Painless Wiring wiring harness (don't use this by the way). I bought the computer from the junkyard, fuel lines/sender from thirdgenparts.com, fuel pump new, the sensors that didn't come w/ the TPI I bought new (reliability) and some other stuff. It was to expensive to do all at once, so I collected a little here and there.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE