I hear some saying SD can make power, how? What are the limitations? Why can't it be tuned to work with bigger cubes and higher HP?

MAF Why is it better, can it overcome the above limitations?

Is there still room for carbs? After doing a lot of searching to attempt to educate myself on the Fords EFI Im starting to think a carb and stand alone tranny controler are cheaper and more reliable.


Not pissing in anyones pocket, just would like to see some real discussion, maybe we could make it a sticky.

If this was covered in another thread (That I could not find) please delete this and point me to it.

 

kinda dissapointed there hasn't been any replies yet, I agree this would make a good discussion.

SD- measures air-flow by comparing engine vacuum to throttle position, and pulling a number from a chart. it is simple and it works very well on what it was designed for. HOWEVER... once you change something that changes how much air your engine flows, the "chart" that the factory computer uses is no longer correct and your A/F ratio will not be correct. the factory computer can compensate a little because it has adaptive programming (to a limit) so that it can keep the engine in tune as it goes through its wear cycle. however it only has so far that it can adapt- and if your mods max this feature out there will be no more "adaptive tuning"

It is tunable though, but it requires reflashing (re-programming) of the computer to what the new values are, to do this correctly requires use of a dyno so it naturally ends up being rather expensive.


Mass-Air: uses a different computer, some extra wiring and a MAF sensor in the intake duct before the throttle body. it uses a tiny heated wire that varies in resistance according to how much airflow flows past it (because more air cools the wire more) since it actually measures the airflow it can send the correct amount of fuel to the engine, overcoming the biggest problem with speed density. however it is still limited to the factory timing curves. (although an external ignition could be used)

Carbs: simple, cheap, easily fixed, but realistically require more maintenance. easy to understand basics but there is both a science and an art in tuning them correctly. Even with the advancements that have been made in carb technology, at the core they are just a controlled fuel leak.

I have done both an EFI to carb conversion and I am in the middle of a carb to EFI conversion and believe me, the latter is much easier. cheaper for sure, but consider the maintenance difference between vehicles of years past. a well built efi can easily outpace a carb in the long run. and is well worth it for a daily driver

Alot of people claim that they can make better power and do better on fuel, and don't get me wrong, its nothing personal against them or carburetors, but i'm gonna finish my megasquirted bronco and prove them wrong...

 

I prefer a carb anyday. I had MAF, but there was a issue with it that no one could figure out. I swapped to a carb and the prob is no more. It runs a lot better now, has more power, but fuel mileage is horrable.

 

A camshaft, set of heads, and a set of Longtube headers are your choices for SD power....Along with advancing the distributor timing a fuzz...

Camshafts can't beyond a certain point of lift; After that threshold is crossed, the computer is no longer able to adapt, then the engine will run HORRIBLE....Causes vaccum issues; Hence the MAP sensor...(Manifold Absolute Pressure)......Beyond the given values, the computer is completely lost as to how to tell the injectors, etc to fire, and whatnot...

And IIRC the SD adaptability is roughly ~10-15%...Anything more, and the computer will crap bricks....And freak dead out...

As to tuning, a Dynometer is the BEST way (You get power readings too!)
But a TwEECer unit, or a Moates' Quarterhorse unit will also do the trick...(Check for a thread on adapting the J3 port of your ECM for a prestated unit to plug into and tune on the fly from a laptop)
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MAF on the otherhand, utilizing a real time air sensor that measures air flow coming into the intake, which in turn tells the computer how to compensate with the appropriate timing, injector firing, etc...

So automatically it's easier to adapt higher lift cams to work in the engine....

And as to the standalone tranny computer remark....They are around $700 IIRC......Baumann makes one.....Not sure on the current prices though...

So that knocks a carb, outta the ballpark as a economy swap....

 

It's not at all cheap to convert one of these EFI trucks to carb especially if you have a computer controlled automatic transmission, besides the carb itself you need an intake, distributor, ignition system, a fuel pump and low pressure regulator, and a trans controller. In comparison all you need for a MAF swap is the computer and MAF meter and some extra wiring... all of which can be sourced from a junkyard or the used market.

SD and MAF computers can be "programmed" to work with more cubes but there isn't a large following that does this with SD Ford trucks outside the Lightning crowd so you won't find much info on it or many places that can do it. There is a hugh tuner base for MAF vehicles however with everything from the 4cyl turbo motors to the 5.0 Mustang and MAF trucks being supported, and the tuner system itself isn't that expensive as long as you already have a laptop to use with it. With a tuner in place there is literally no limit to what you can do to the motor but the catch is you have to learn how the Ford EFI system works and how to tune it.

 

GREAT INFO!

Allow me to play Devils Advocate for a moment,
On my ONLY ford build ever, I took a 85' f250 2wd auto c6 351 Ho from 9 mpg to 14 and gobs of power with an edelbrock perf and 625 cfm ele choke edelbrock carb, and long tube headers. I spent less than $500 back then and could easily outpull any BB's or diesels of the time. Add $100 for inflation and $700 for the trans controller and we're at about $1200. I left out rebuild and cam because its the same either way.

 

Then the highjacker says: How did I get here? I clicked "reply to thread", and was suddenly in the middle of Sidewinder's post! Anyway, what they said is all true. I would add that while MAF systems can adapt to greater changes in airflow than SD systems, the MAF sensor is a high-failure-rate part that costs big$$$ and can be ruined by a little dirt in the air stream. So SD or carburetors may be more economical as to component replacment but carbs will use more gas because they don't do things like decel fuel cut and feedback controlled mixture. Still, atmospheric pressure and gravity are free while high pressure pumps and injectors cost money. They all have their place.

 

OK i'll bite. You can convert your '91 2wd F250 to MAF with about $200 in junkyard parts, add longtubes and the Crane 444232 and it'll match or beat your '85 build in power and get better highway fuel milage.

 

Good point, should have better manners to.

But lets go a step farther. That truck might be getting a 4" crank during rebuild. The heads will get ported and the carb might be E85. I'm looking at a 400 HP low rpm hauler. Could I do this with Ford efi?

 

Yep no problem once you have a tuner.

 

The stock intakes, TB's and injectors will supply that much?

 

Everything but the injectors...After a certain point they become the first weak link...

 

I'm still impressed, I never would've imagined the stock air delivery could handle the cfm.

Will SD do this?

 

with my bronco's megasquirt I can hook up a factory "bio-fuel level sensor" and tune it to automatically compensate for the E85 (without the tuning restrictions OEM's have) its only downfall would be lack of compression ratio. not sure if it can be done with tweecer or quaterhorse can, I have room to add circuits! It is also wired for wide band o2 sensor, which increases drivability and mileage even more. along with that, DIS means no recurving dizzy's, no cap & rotor, and a really good spark...

I think that the big problem with accepting fuel injection comes from people not wanting to learn the technology.

over-oiled air filters have been known to cause MAF failures.

also, with FI you can better engineer the airflow in the intake.

 

How much does a MS system run?

And Joe...SD will do this....