How can you tell if a car is SD or MAF? I have a 92 camaro rs 305 tbi auto, actually now has a 383 but still the stock tbi until I get the holley. I was reading some old posts and a guy said that speed density is alot harder to get the numbers just right when burning the custom chip than it would be if you had a mass air flow car. Since I'm about to put on the new holley and go and get my chip burned(by a company that knows how to do this) do i need to switch to MAF to ensure my car runs smoothly? Thanks Danny

 

You have speed density. I dont think there's a computer out there that is tbi/maf and if there was im sure it wouldnt be pretty

 

Actually you have neither.

A speed density system and mass air flow system both monitor the amount of air that enters the engine. We don't have that luxury.

What we have is a MAP sensor (Manifold Absolute Pressure). It measures the pressure drop at the intake manifold to guesstimate how much air is flowing into the engine.

Another problem we have with MAP, is mods we do to the motor. If the MAP always reads a low or high pressure, then the computer goes goofy, and gets worried something is wrong.

The SD and MAF systems are better because if you increase airflow into/through the engine, the ECM says "OK. Cool" and automatically adjusts for it. Well....... to an extreme anyway.

AJ

 

SD uses a map sensor. Thats how it works.

 

So what you guys are telling me is with the 383 i now have and the holley 502-6 I am about to get, I'm still going to have computer problems even after I have a chip burned to match all of my specs? What would you guys do in my situation cuz right now I am about to buy that holley cuz my engine is running all wierd sometimes. I know I have to have bigger injectors for sure, but what else am I going to have to do w/o sacrificing the TBI which I want to stay with? Any help would be appreciated. Thanks guys

 

Really? I thought TPI was the only FI that got SD?

Well does that mean that TBI is SD? I didn't know that.

AJ

 

Yup... here's some info on it...... sorry.
http://www.eecis.udel.edu/~davis/z28/ecm_swap_730/

I guess that I've only heard about SD mentioned with TPI so I ***-u-me-d that it was only on TPI.

AJ

 

tpi, tbi, and cfi all where speed density. I really hate speed density systems when the egine starts to go south and doesnt make good vacuum. My 4.3 never ran right once with the cpi injection system, always ran terrible from the various ailments that it would always develop. Things would break faster then i could fix them. Speed density also sucks when it comes to cam selection. Big, lumpy, low erratic vacuum cam=angry computer.

 

So I am still not sure what you guys are telling me. Do I need to scrap the TBI setup on my new 383 and go to a carb setup? I really want to stay with TBI but I am so afraid after I spend all the money on the new TBI, ship, and tuning I am still going to have problems. Should I go to a carb setup? Please let me know. Thanks guys

 

if you tune it and set everyhting up properly, you wont have any problems.

 

I ran a 383 with the 670 holley tbi and 85pph injectors.
I tune my own chips and it ran perfect.
But since

"...and get my chip burned(by a company that knows how to do this)"

they will probably screw it up.

Oh yeah all tbi's are speed density and speed density=MAP.

 

I would burn my own chips but I have no idea how to interpret the data and understand what it means. I am afraid will screw it up. I have no idea what my engine and everything for my engine is supposed to be tuned to so I figure I should take it to someone who knows more than me. Thanks for your help guys. Danny