TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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OK, I'm confused on all of this speed density, maf, map, and all that stuff. I can't find an explanation about it all. Can anyone explain this to me? Are MAF and speed density different...if so, how can a speed density stealth ram work on a MAF car?
Speed density system is basically a calculated air/fuel mix based on rpm, temp, speed...etc based on a predetermined table. So if the car is at 60mph at 1800rpm and it's sucking in 80* air, the computer will tell the motor how much fuel to give. Speed Denisty isn't to tolerant of modifications without tuning.
In MAF, its more real time, with no predetermined table of calculations. The actual amount of air is measured and the computer tells how much fuel to give. It is what is is. MAF is more tolerant of modifications to an extent.
Basically, GM started to use SD to save production costs and it also saved owners a few hundred dollars because there isn't an epensive replacement when a MAF goes out.
In a nutshell, I'm sure someone else can chime in and correct me if I'm wrong.
__________________ 1994 TRANS AM GT: A4,3.23 / Cai / Borla Adj Catback / SFCs / Strano Springs / Koni Yellows
Speed density can make more power but the chip needs to be custom made, while mass-air can take more cams without modifications. SD cars use a programmed set of variables to deliver the fuel requirements of the car. It reads things like engine temp, throttle position, 02 sensor, etc and delivers a set fuel curve.
Mass air cars use the mass air meter to determine the amount of air entering the engine and adjusts the fuel curve accordingly.
__________________ 1986 Berlinetta-(1st car, 1st thirdgen, MX0, L44, hardtop) 1991 rs-medium quasar blue (L64, CC1,MM5, v-8 swap) 1991 rs-red (L64, MX0, hardtop) 1989 rs-gun metal grey (LO3, MX0,hardtop) 1991 z28-red(CC1, automatic LB9 TPI, MX0, D81) 1991 formula firebird- red (WS6, LO3, MX0 CC1) 1990 rs-black (project car, z-28 clone, hardtop: freshly rebuilt 5.7 L98, MAF TPI Automatic, Hedman Shorty Headers, 24lb LT1 injectors, SLP Loudmouth I, 16" Boyd Coddingtons, Dropzone 2" lowering springs, Smog delete, AC delete, Poly torque arm and trans mount)
OK, so the HSRs for sale always say "speed density" with them, so how do they work with a MAF car? This is what I don't understand. Do the HSRs just work on MAF cars, when the proms are messed with? I guess I don't understand why Holley specifies "speed density" with their stealth ram.
If you're looking at the $3000 stealth ram kit, that's a complete change over kit for a carb car. That includes their special ECM and wire harness which is a speed density setup. Otherwise, the MAF air intake and the speed density air intake both bolt up to the same throttle body on the front of the stealth ram, so I dunno what they're talking about.
I was able to run a 305 5-speed TPI speed density chip with a 350 engine, 22 lbs injectors, ZZ4 camshaft, headers, ported Corvette heads, etc with no problems. It wasnt until I switched to the LT4 hot cam that I needed a custom chip. Your mileage may vary. A MAF setup will need a custom chip at that point, too.
You searched for "MAF vs SD" and didnt find any good topics?
