I talked to the man who will be tuneing my new engine he was talking something about doing away with the maf and using speed density what do you think and is it better its a mild built ls6 n/a
Speed density is better if you intend to drive around in the same elevation, if you go into the mountains or something the car will not like it at all.
Speed Density systems accept input from sensors that measure engine speed (in rpm) and load (manifold vacuum in kPa), then the computer calculates airflow requirements by referring to a much larger (in comparison to an N Alpha system) preprogrammed lookup table, a map of thousands of values that equates to the engines volumetric efficiency (VE) under varying conditions of throttle position and engine speed. Engine rpm is provided via a tach signal, while vacuum is transmitted via an intake manifold-mounted Manifold Air Pressure (MAP) sensor. Since air density changes with air temperature, an intake manifold-mounted sensor is also used.
Production-based Speed Density computers also utilize an oxygen (O2) sensor mounted in the exhaust tract. The computer looks at the air/fuel ratio from the O2 sensor and corrects the fuel delivery for any errors. This helps compensate for wear and tear and production variables. Other sensors on a typical Speed Density system usually include an idle-air control motor to help regulate idle speed, a throttle-position sensor that transmits the percentage of throttle opening, a coolant-temperature sensor, and a knock sensor as a final fail-safe that hears detonation so the computer can retard timing as needed.
GMs Tuned Port Injection (TPI) set-ups used Speed Density metering from 90-’92, as did 91-’93 LT1 engines. All 86-’87 and 88 non-California Ford 5.0L-HO engines used Speed Density metering. Most Mopar fuel- injection systems have used Speed Density too.
Because a Speed Density system still has no sensors that directly measure engine airflow, all the fuel mapping points must be preprogrammed, so any significant change to the engine that alters its VE requires reprogramming the computer.
By contrast, Mass Air Flow (MAF) systems use a sensor mounted in front of the throttle body that directly measures the amount of air inducted into the engine. The most common type of mass-flow sensor is the hot wire design: Air flows past a heated wire thats part of a circuit that measures electrical current. Current flowing through the wire heats it to a temperature that is always held above the inlet air temperature by a fixed amount. Air flowing across the wire draws away some of the heat, so an increase in current flow is required to maintain its fixed temperature. The amount of current needed to heat the wire is proportional to the mass of air flowing across the wire. The mass-air meter also includes a temperature sensor that provides a correction for intake air temperature so the output signal is not affected by it.
The MAF sensors circuitry converts the current reading into a voltage signal for the computer, which in turn equates the voltage value to mass flow. Typical MAF systems also use additional sensors similar to those found in Speed Density systems. Once the electronic control module (ECM) knows the amount of air entering the engine, it looks at these other sensors to determine the engine’s current state of operation (idle, acceleration, cruise, deceleration, operating temperature, and so on), then refers to an electronic map to find the appropriate air/fuel ratio and select the fuel-injector pulse width required to match the input signals.
GM used MAF sensors on the turbo Buick V-6 Grand National, 85-’89 TPI, 94-’98 LT1, 96 LT4, and all LS1 engines. Ford has used MAF metering on 88 California 5.0L engines and all 89-and-later V-8 engines.
MAF systems are much more flexible in their ability to compensate for engine changes since they actually measure airflow instead of computing it based on preprogrammed assumptions. They are self-compensating for most reasonable upgrades, as well as extremely accurate under low-speed, part-throttle operation. On the other hand, the MAF meter, mounted as it is ahead of the throttle-body, can become an airflow restriction on high-horsepower engines. On nonstock engine retrofits or EFI conversions on engines never produced with fuel injection, it may be hard to package an MAF meter within the confines of the engine bay and available intake manifolding.
Which Is Best? In a perfect world, virtually all street-performance engines would use Mass Air, due to its superior accuracy and greater tolerance for engine changes. In the past there was a problem on high-horsepower engines because larger-capacity MAF sensors were scarce and prohibitively expensive. Nowadays, oversize MAF sensors are available from Pro-M, Granatelli Racing, and other sources that are compatible with Ford engines and computers. Custom MAF calibration keyed to the specific vehicle, engine, and injector size is also available. With a correctly calibrated oversize meter, reflashing the computer usually isn't required
Me you I would get some one else to tune your set up this guy seems to be an amateur and I have already had a run in with an amateur from the state of Texas that set me back an extra $4K on top of the $6K my wife gave him to do a job when I was deployed. Advice is free ignoring advice can get expensive.
I run SD on my car, trapped 90-91mph in the 8th with just bolt ons...so it must be doing something right.
Best advice is research the guy, talk to people he's tuned and see how they like the behavior of the car. Then decide for yourself, I dont think either tuning method will make a difference.
__________________ 2006 Trailblazer
1989 Toyota 4x4...covered in mud till it rains
2002 Camaro SS Blk/Blk 6spd
Bolt Ons|PatG Cam|TSP|HSW|NANO|Moser|UMI
Properly tuned MAF cars make much better consistant drivers. GM made these cars use a MAF for a reason. SD is easier to tune and IMHO most tuners wanting to do this are lazy. Only fairly wilder combos would make using a MAF hard or impossible in most circumstances.
__________________ 02 Z28, forged LQ4, built 4l60, current best of 11.08, but I haven't had this engine to the track yet
This question is like asking what's better, a spoon or a fork? It all depends on the application and the goal. On a stock car, you're going to get better/ consistent fueling with a MAF. However, on the same car you might make more horsepower with SD because the MAF can become a restriction.
Well I typed up a big long post to explain why a MAF sensor was important, but it was too detailed.
Basically the MAF measure the mass of air flowing into the engine. If you take the MAF, RPM, TPS, and MAP sensor reading you can predict load and not just calculate load. The way those three other sensors respond to the TPS changes can predict the changing load.
OK so what.
If you are not making a WOT run like 1/4 of a mile at a time and you are driving your car on the street you would want to predict the change in load.
Even some of the transmission function are base off of this, so with out the MAF the trans will not operate the same.
I would never leave home without it.
__________________ The answer man
GM World Class Technician
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I got an SD tune... runs great part or full throttle! All this discussion is doing is getting peoples opinions, which are always helpfull. Not to bash anyone but most or all of the people who tell you to get a MAF tune have never had, had experience with, or ever even seen an SD tuned car. There are drawbacks to an SD system like if you do any further eng mods you need to retune, but I would also retune a maf car. Anyway, I chose SD solely on the fact that I ran out of money at the time. In no way do I think it was a bad decision and will prob never put a MAF on it. Just trying to give you an UN-biased opinion. Both run great (depending on the tuner) but most people stick with what they know, which isn't allways a bad thing. Have fun deciding!
__________________ 99 Vette Ls1, Vararam, Borla Stingers, 25% udp, fast92, 90mm tb, lg pro lt's, g5x3 SD tune 422rwhp 396rwtq
I got an SD tune... runs great part or full throttle! All this discussion is doing is getting peoples opinions, which are always helpfull. Not to bash anyone but most or all of the people who tell you to get a MAF tune have never had, had experience with, or ever even seen an SD tuned car. There are drawbacks to an SD system like if you do any further eng mods you need to retune, but I would also retune a maf car. Anyway, I chose SD solely on the fact that I ran out of money at the time. In no way do I think it was a bad decision and will prob never put a MAF on it. Just trying to give you an UN-biased opinion. Both run great (depending on the tuner) but most people stick with what they know, which isn't allways a bad thing. Have fun deciding!
When a guy tells you off the bat to get Speed Density, does not even give you the choice, then there is something wrong there. Speed Density while I have had a few car (early 80's MustangsX2) I have found over the years that a MAF application is a lot easier to work with when tuning. With speed density it was an all day affair dialing a car in if I needed to change tunes just because of fuel compared to a 1/2 hour to an hour at the most for a MAF tune due to the same reason. While Speed Density is great once it is set there is no beating a MAF tune-ability for an every day driven car.
I am sure that all of that is not readily out of my head and thanks because last time i remember having to do a in text citation or a reference page was for college paper ill remember for next time. I my self have seen plenty of people write things (copy & paste) readily found on the net and never reference it and i did not get on them but apparently we have a scholar amongst us wrench turners.
02*c5 if you look at the op it doesn't say anywhere that he did not give him the option that he would only do it in SD. Therefore it sounds like the tuner was giving him an option or an opinion. Thats just how I read into it... Besides he may be the most badass SD tuner in the world..?? Maybe NOT.
__________________ 99 Vette Ls1, Vararam, Borla Stingers, 25% udp, fast92, 90mm tb, lg pro lt's, g5x3 SD tune 422rwhp 396rwtq
maf vs speed density 
