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Discussion Starter #1
I know that other makes want Speed Density over Mass air with turbo set ups yet in the Mustang Universe Air Mass Air rules. Is it possible to run Speed Density with a turbo and if so how? I know that some people run the megasquirt, but after reading some of it, I am a little afraid of getting in computer programing and tuning.

Thanks for any assistance,

Hunter
 

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You will need an aftermarket computer to run SD.

The AEM plugs right into factory harness but is kind of expensive.
 

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I seem to recall someone on here awhile back actually getting the factory speed density working with his turbo setup. I highly doubt it ran near as good as the factory mass air would have treated him but maybe I am wrong. My outlook on it matches r.barn's. You could search around and maybe find a used setup, there are quite a few out there to pick from. Unless however you plan on making a ton of power I'd stick with the factory stuff, it seems to work good for most people.
 

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I have an article in MM&FF where they installed 2 t-3's on a factory SD 1986 Mustang and it went [email protected] 19lb injectors, Cartech FMU, stock 2.3 turbos, Ported 289 big valve heads, E-303, 155lph pump, stock intake, stock 87 spec short block.

I argued like a mofo it was impossible till someone posted the article and I had to apologize for being an ignorant ass.
 

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you can run a turbo setup on sd...there is a guy on nloc.net running a pt76 on a 357w with stock lightning sd using a tweecer.
the truck is a full weight truck and a dd,ran 10.9x last i heard with 15 psi.
 

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If the tune is for speed density there is no reason sd would not work well. Even though the tune is critical for all turbo setup cars, it is even more critical to speed density. And leaks will be more significant to how it runs.
 

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Mass Air is great because it is more accurate and can compensate for minor modifications and what not ... but if you have major modifications, you will need a full tune anyway. There's no reason you can't tune in your Speed Density system just as well. However, if you make minor tweaks to your setup, you may have to retune.
 

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Mass Air is great because it is more accurate and can compensate for minor modifications and what not ... but if you have major modifications, you will need a full tune anyway. There's no reason you can't tune in your Speed Density system just as well. However, if you make minor tweaks to your setup, you may have to retune.
not only that sd cnt compensate for altitude or major temprature changes.

ie....it goes from 70* to 45 one night at the track...your tune suddenly becomes overly lean.the oppsite happens with it being hot.

mass air is better in some many ways but, sd can be made to work.
 

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SD can compensate for altitude and temp changes, thats the whole advantage of EFI, if it couldnt do that then its no better than a carburetor.

i like to look at SD and MAF as the same thing but SD has an extra step involved which is calculating the mass of the air charge.

on a SD setup the EEC, it takes a manifold pressure reading (MAP sensor), engine speed, and air temp. engine speed vs engine size is used to get an idea of how much air would move through the engine, pressure and temperatue are take (2 things that affect density) then calculate and then the air mass in figure out, then its a simple matter of injecting the corresponding amount of fuel to match the air to achieve a desired AFR. increased air temps means less density so less fuel is needed, all those factors are taken in to determine the air mass. same with pressure, less pressure = less mass.

the MAF setup is the same way but instead of having to go through the trouble of calculating the mass, the MAF reads mass itself so it just gets a reading from the maf and then shoots the fuel to match, the MAP sensor isnt used in the maf setup, insteads its used as a BAP (barometric) and it is used to change spark tables as you go up in altitude, thats as far as i have seen thats its used for, in stock tunes.

the ACT is still used in MAF setup to compensate for spark for higher ACTs, higher charge air temp leads to detonation so if you can pull spark or add fuel that will act as a safety net for you.

ive never personally tuned on a SD setup, but AFAIK its slightly more involved to get it tuned. MAF is simpler to tune.

the reason stock SD mustang run into problems when modding then is you change the manifold pressures during idle and other operation, which is more or less the main feedback for the SD system. most cammed up non tuned SD mustangs run like crap, AFAIK they should run the same at WOT, since manifold pressure goes roughly to 100 kpa or 14.6ish psi absolute under atmospheric N/A conditions. so the EEC should be reading from the same cells in the fuel table as it was before. where at idle where vacuum is usually reduced with a cam change. you EEC goes off a different cell which mostly likely will be wrong.

most standalone EFI setups use SD setups, but AFAIK you can use a MAF if you desire ( i know AEM can use a MAF) AEM also has start up tunes for a mustangs, that makes things easier. but megasquirt and others, not so much afaik, they are alot more involve in that you dont have anything to start with, so you build a tune from scratch.

IMO SD would actually be a better EFI to use, that way you can get rid of the MAF in the intake tract, to simplify intake tubes to maximize airlfow into the engine. for a boosted application i see it being slightly better since your dealing with manifold pressures and can more easily determine boost levels, where with a MAF you deal in air mass or kg/hr, so its harder to tell what is boost unless you calculate the theoretical air mass you engine can flow n/a, then anything over that is boost, or you can also log boost, but still SD makes it easier to have compensation referencing directly from boost (absolute pressures higher than that of atmospheric)

i myself have been tuning with a tweecer, using a stock EEC and a maf setup like stock does. works awesome. all the same EFI principles apply to nearly any EFI setup. i'd like to get a nice aftermarket EFI setup to better control things.

on 5.0 mustangs, the MAF setup will be able to operate great with performance upgrades, the cam wont affect anything since the EEC is reading air mass, if the cam changes air mass intake at idle, the EEC simply sees that a a change in air mass and just shoots in more or less fuel, whatever it needs. IMO the only time you run into cam problems is when you get such a large cam the car wont idle at the stock eec is trying to make it idle at, forcing you open the TB with the set screw which doesnt make anything better.

then when you start changing MAFs and injectors things can go haywire fast, with those mods, the EECs assumption of how to control things are wrong, some maf come "calibrated" to work with stock untuned computers but all that does is lie to the EEC, may get you the fuel closer to correct but spark is affect due to the lower load reading the EEC is calulating now, so optimal spark in the driving range is affected. the affect isnt as bad with small injector upgrades like to 24s, but when you start trying to run blown cars with 42s or bigger, with calibrated mafs and no tune, my car and others i have messed with have done nothing but like like crap and nothing was close to right, i am not saying there are some people who has had luck doing things like that, but i never have.

when you get to the point of MAF and injector upgrades and blowers or turbo, your to the point where you need some sort of tuning done for reliability and power and better driving manners.

i'm no expert but thats just how i have gathered things.
sorry for the novel i just wrote lol.
 

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i dunno jack about mustnag sd...i assume it is like the 93-95 lightnings. on my truck with the tweecer,once you set the injectors and all up, there is no way to make the calculated chage in air mass to make the ecm read air change correctly with any injector over say 30#s. thus why i stated the tune differnce.the whole base table needs to be changed when you go bigger than 30s.this is the exact reason im switching my truck over to a a9p to get better control of my turbo setup, and stop this annoying changes in my tune every few hours when i m at the track.
 

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twin turbo

hello...i dont have a mustang but i drive a volvo 244.. with a 88.mod 302 ho engine.. with speed denisty ... i run 2 garret t-3 turbos.. . 44mm waste gate.. 8:1 comp.. ported stock heads..1,7rr.. stock cam.. o ringed block.. 1/2" studs for the heads.. 3" exhaust.. i run 16 psi boost.. 8 xstra injectors on bost control.. 4 at 5 psi and the next 4 at 8 psi ... then a water alcohol injection also at 8 psi.. 2-1 fuel pressure regulator..msd digital 6 ignition.. blaster3 coil.. i run only 98 octane pump gasoline.. i have no idea how mutch horsepower it puts out but its fast.... to fool the map sensor i use a one way walve on the hose from the manifoil..

i run a stock bw t-5 gear box and stock volvo rearend .. with 3,54 and a lock right..
215/45-17 tires.. i raced this summer but its hopless to get traction with those skinny tires.. he he .. full wheelspin in 3 gear..

im gona post some pictures...

jan erik norway:rolleyes:
 
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