do i need to chang speed density to mass air

[pdr]

i modifyied my 87 t-top,to a 306 24 injectors E303cam they say i need to change my speed density into a mass air flow is that true,and why?

[Jeff Chambers]

SD isn't very accomodating to changes. A mass air conversion will open up many doors in terms of future upgrades and the tunability of the combination.

[richs347]

On the SD cars, the computer runs off a set of pre-made fuel and timing tables. It's very limited to what it can change based on your additions. So, if you're adding heads, intake, etc... you're substantially adding more air, which needs more fuel... and the computer isn't able to compensate.

On the mass air cars, the meter reads the amount of incoming air and the computer is designed to read that amount and adjust the timing and fuel curves. The newer computers also use adaptive control and have the ability to learn and design new tables based on what it sees through the 02's in closed loop. It's a much better system to use when making modifications on the car. With a NA car, until you get to about 42 lb injectors you can just tune the car with timing and fuel pressure adjustments and the computer will usually work with you. (As long as fuel injectors are matched to the mass air meter and are the right size for the application).

[Unit 5302]

Glad to see the speed density boogie man is still running around in full force.

Speed density tables are significantly more adaptable than MAF tables will ever be because they can't read the amount of incoming air. Depending on modifications, a speed density system may not be able to compensate, but there are members of this site who have successfully used the E303 on SD EECs (88workcar to name one). One of my old friends had 24lb/hr injectors in his 87 GT for a good 2 years even without an AFPR without signficant problems (he did have some idle surge issues from time to time that he needed to tune up).

24lb/hr injectors are unnecessary for virtually any NA EFI E303 cammed 5.0.

[Jeff Chambers]

Originally Posted by Unit 5302

24lb/hr injectors are unnecessary for virtually any NA EFI E303 cammed 5.0.

Do you actually believe this? If so, I've got a real nice bridge in NYC that I'm looking to sell. You can PM me here for more details on the bridge.

[Dark_5.0]

You cant run bigger injectors with speed density so yeah its time for mass air.

[1989GT]

If all you have is a 306 with an E cam(stock heads and intake) then I would just put the 19 lb injectors back in and drive it, until you mod it some more and have a real need for mass air. Or just skip mass air and go stand alone.

[~The Jester~]

Me thinks that this thread is about to get interesting.....

[richs347]

Some stand alone systems are based on a speed density set-up - and they work great... However, with a 306 and an e-cam, I don't think that level requires you to fork up the cash for a stand alone system yet. However, they run about $1200 and up + tuning time / or dyno (unless you're willing to learn), and it will take $300 - $500 to convert to mass air. ...One of those pocket book issues. If you want to play for many years to come, it won't hurt to splurge now. Just remember though, that as your engine mods grow, so does the need for supporting hardware (injectors, fuel pumps, lines, meter, TB, ...axles, brakes, new tires, etc...)

[1989GT]

Not all stand alone's are $1200+, check out mega squirt, it's speed density or Alpha-N which ever you choose. They have a complete forum set up for support. It's the ultimate in DIY. If I had a speed density car that I had modified beyond what the ford ECU could handle I wouldn't even bother with mass air, I'd use mega squirt and have complete control over the engine. Add a wide band O2 and you can tune it on the street, which is what many people do.

http://www.diyautotune.com/catalog/index.php

http://www.megasquirt.info/

[pdr]

thanks for the help, i did lower down to 19inj and still converted to maf and its working good .thanks !!!!

[Jeff Chambers]

I've done a few megasquirt cars. It is a fairly tunable system, but it is nowhere near the sophistication of FAST, Edelbrock Pro-flow or some of the other established systems. One thing that I don't like about it is that it 'hangs' occasionally, requiring that you disconnect the unit to get it to reboot. This means that the unit always has to be accessible...a real pain in a daily driver. It lives up to the old adage "You get what you pay for." If you want to stick with the factory electronics and want your own control over tuning, then I'd recommend getting SCT's Pro Racer Package. It will give you all the control over your processor that a professional tuner has when he/she is tuning it.

[Unit 5302]

Jeff, if this was the racetrack, I'd bow to you on the wisdom. This isn't the racetrack and members of this site have run the combo. I've personally seen 24lb/hr injectors run on a 306 block 1987 Mustang GT T-Top car that was otherwise stock for over 2years. If I hadn't had first hand knowledge, I wouldn't have said it.

By the way, you need to do more research on speed density systems or real world tuning with injector swaps between SD and MAF systems in order to quote what will and will not work. I know you don't have first hand knowledge of this, otherwise you wouldn't be quoting what you were. Anyway, I'm not saying that the overall application of speed density can handle more modifications than a MAF car. That's ludicrious as there are finite limits as to the SD tables. That being said, the tables themselves are far more adaptable than the MAF tables. There is no MAF equipped 5.0 that would be drivable using 24lb/hr injectors without being calibrated for them, period. I've seen speed density handle it, like I said, first hand for over 2 years. The only problem my friend had was with idle surge which required him to reset the computer about once a month and it would clear up.

I don't know what would happen if you slapped 24lb/hr injectors onto an SD engine with a cam.

[Jeff Chambers]

Put you glasses back on and read what I said. I was commenting on your quote that 24# injectors aren't needed on ANY 306 based NA combination. That's a might broad statement on your part....one that's wrong. I maxed 19# injectors out on one of my combinations long ago. So much so, that even 24# were marginal at best. That was with a 306ci motor with unported P-heads and an E303 cam. That car went 11.97 with a T5 at 3200#.

I've tuned more than 250 cars since I opened the shop 18-months ago. I think my experience far outweighs yours. I think I've seen enough to stand by my original statement that SD (Ford EEC versions) isn't as accomodating as MAF-based (Ford EEC versions) is. Unless you've got Mike Wesley in your back pocket, you're going to be pretty much out of luck in terms of tuning the SD system for changes such as cams, heads, blowers, etc. Slap a FAST SD system on it an you've got a different situation...primarily because FAST has carried the programming and user interface onward. You won't find this is the case for EEC-IV SD systems. Autologic is almost non-existent any more, SCT has very few SD box codes available, and Diablo doesn't handle it at all (to the best of my knowledge). So if PDR has big plans on down the road, a MAS conversion should be in those plans somewhere. 'nuff said.

[Dark_5.0]

You have to have one very serious set-up before it is even feasable to go to a stand alone set-up.

I have ran every combonation of parts you can imagine on my 5.0. I am speaking from real world dyno proven experience here. You dont "need" to go to mass air until you outgrow the 19# injectors. I have worked on cars that put 450 to the wheels with the stock A9L, 30# injectors and C&L mass air meter.

I currently have a 255 lph fuel pump, A9L, 24# injectors and a C&L meter and my car puts out roughly 315 to the wheels. I will take this same set-up and put it on my 331 stroker this Winter with no worries.

Dont make things over complicated its really simple.

[Jeff Chambers]

Originally Posted by Dark_5.0

Dont make things over complicated its really simple.

Agreed. The MAS conversion is cheap and simple....and opens up so many more possibilities in terms of modifying the vehicle in the future.

[richs347]

I ran my 347 for 10 yrs without a stand alone system (255 intank, 30lb inj, NA 350hp 360tq rw). I only had to add the PMS when I added my supercharger.

[Jeff Chambers]

I recently tuned a 1999GT with single turbo kit making nearly 700RWHP with nothing but the stock G3GZ computer and an SCT XCal2. Some shops are reporting more than 1100 RWHP out of Ford GT's with the stock computer system and SCT tuning. I don't think anyone is saying that PDR needs a standalone system at this point. The point that I was attempting to make is that the stock EEC-IV SD system has limited tuning opportunities in today's world and that if he's dead-set on staying SD, that there are SD-based systems out there that are more than capable.....although at quite a cost.

I was looking at the DA1 box code last night (87-88 SD Mustangs) in my SCT software. It can be tuned through the VE table, however there is little else in the base files that will let the tuner address the driveability factors. It does give access to the base fuel, VE, basic spark and injector values though. This would be enough to hammer out a basic tune but it would be difficult and time consuming to tune it for the most of the driveability characteristics that people have the most problem with. The hardest part would be tuning each cell of the VE table (10 rpm cells x 8 MAP cells) without having the benefit of a data logger. That's where systems like FAST really shine through. You can head out on the road (or on a loaded dyno) and hit nearly all the cells capturing commanded vs. actual data, then drop the results right over the top of your base tables for immediate correction. A FAST XFI system runs pretty close to $3k though.

[Unit 5302]

Originally Posted by Jeff Chambers

Put you glasses back on and read what I said. I was commenting on your quote that 24# injectors aren't needed on ANY 306 based NA combination. That's a might broad statement on your part....one that's wrong. I maxed 19# injectors out on one of my combinations long ago. So much so, that even 24# were marginal at best. That was with a 306ci motor with unported P-heads and an E303 cam. That car went 11.97 with a T5 at 3200#.

I've tuned more than 250 cars since I opened the shop 18-months ago. I think my experience far outweighs yours. I think I've seen enough to stand by my original statement that SD (Ford EEC versions) isn't as accomodating as MAF-based (Ford EEC versions) is. Unless you've got Mike Wesley in your back pocket, you're going to be pretty much out of luck in terms of tuning the SD system for changes such as cams, heads, blowers, etc. Slap a FAST SD system on it an you've got a different situation...primarily because FAST has carried the programming and user interface onward. You won't find this is the case for EEC-IV SD systems. Autologic is almost non-existent any more, SCT has very few SD box codes available, and Diablo doesn't handle it at all (to the best of my knowledge). So if PDR has big plans on down the road, a MAS conversion should be in those plans somewhere. 'nuff said.

Jeff, if you were talking about my comment regarding 19lb/hr injectors, you need to re-read what I wrote as well. I said 19lb/hr injectors are enough for "virtually" any N/A EFI 5.0. Your engines haven't fallen into the category "virtually" as they have been serious race setups running thousands more rpms than the stock engines see, and put together with custom tuned components designed with all out performance within the rules of your class. You'd be hard pressed to find a more powerful NA EFI 5.0 than what has resided under your hood, as your multiple world records might attest to. There just aren't a lot of NA EFI 302s making over 330-340hp, where the reasonable NA limits of the 19lb/hr injectors are reached. Certainly a VERY few that are running an E cam.