BACKYARD EFI

[deuce_454]

the old style TPI arent really digitaly controlled so you have a very narrow range of tuning on the MAF unit.. the later ones are speed density, which can be as acurate (and have less intake restriction) but to achieve the hich accuracy requires either tuning every engine individually.. or having a manufacturing practice that ecsures every engine is sufficiently alike to run the same program.... (or as GM did, have adapitve learning to "tune" the engine to the car)

so as to why the MAF-TPI is being ditched for the speed density TPI.. it allows you to run cams and such... and the computer that apparantly allows for most tuning is the one with the cold start injector.... the runners are to the best of my knowledge the same.. but if they arent.. that is an even better reason to run the cold start unit over the other

if you ar erunning a megasquirt, you will be lightyears ahead of all the OEM crap. and you need to focus on an intake with the best dry flow.. (forget what you know about carb intakes, and get one with long BIG runners) an accell super ram is a good bet, or the PP single plane and just mount a junk-yard/ebay throttle body from somthing like an LS1 or whatever you can find with a big blade, cable operation and a TPS.... all you require si a plate to adapt the two.. and that should not be a biggie to fabricate...

 

[JP86SS]

The MAF vs SD thing goes both ways.
You can make either system run good with proper tuning.
In a nutshell,
the MAF system provides fuel based on the actual airflow measurement.
This allows you to make moderate changes to the intake or exhaust system without having to really get a new chip made.
The downside of MAF is that it doesn't see fast transitions like when stomping from idle to full throttle.
MAFs also run out of resolution or measuring range once you hit a certain airflow.
The fuel runs on constants at that point forward.
Early MAF setups up to 88 IIRC used a cold start injector to get the motor started.
Later years just made the injectors pulse more for the startup enrichment. 89' up
Stay away from 1985 setups if you have a choice. Very early in the implementation of EFI and is a 1 off control setup.

Speed density or MAP based systems use the air pressure to calculate the airflow.
This is based on assumptions (displacement size, injector size, etc) and is not forgiving when modifications are made.
The tune must be adjusted to compensate for the way the engine is setup.
Adding headers would cause the engine to breath beter and the automatic fuel adjustment would run out of range because the values in the calibration to calculate the air/fuel ratio would now be incorrect for that setup.

Megasquirt is a decent system from what I've heard, The GM stock computers can run the engine just as good.
The stock GM code has been reversed and many tuning packages for software and chip adapters are available.
I made my own harness and rewired my car to a 90-92 SD setup running a 1227730 GM stock computer. Runs customized GM code with many additions for WB o2, expanded tables, knock indicator light, etc.
I'm happy with how it works and have full control over spark, fuel and other fuctions. Would never go back to a carb at this point.

In any case, with ANY FI application there is tuning involved.
You can get a setup to do it yourself or pay someone to do it for you.
Mail order chips don't work well because they do not drive your car.
You will never be happy with it in day to day driving.
The only thing you'll get is WOT (If they get that right and it will probably take 2-3 times on that)
IMO, You'll be able to buy all the stuff to DIY it with the cost of 1 bought chip.

Having a dyno shop do it works ok but there could still be nagging issues with stop and go traffic.
There is no correcting this unless you go back to them to correct it.
If you had the ability to burn a chip, it could be adjusted in seconds.
The learning curve on the GM stuff is a bit steep and requires reading alot of info to get a good grasp of all the little things.
The aftermarket stuff appears easier to get running but comes with a high price tag.
I actually ripped out an Accell DFI setup in favor of my GM because everytime I called for help they acted like they never made the product because it was the last version, not the latest. Screw them, I was on my own anyway.

In closing this book, You will need to understand how the "System" works as well as what each part of it does.
That is the only way to make it work effectivly and correctly.
Parts changing style of troubleshooting when there is a problem doesn't usaually work with Fi until you've replaced everything.
The datalogging will indicate what is wrong most of the time.
HTH,
Jp

 

[StreetBu]

I'm comfortable around efi, enough that I wouldnt be afraid to jump in and start tuning one. I know what they're supposed to need and what they actually need to run at given good sensor readings. I guess like everyone else I just want the best i can get for the minum amount of $. :lol: As fas as burning chips, I do not want to go that way. Too time consuming, cost etc. I would much rather have a laptop, adjust it and save it to an on-board computer. I seems as though the plethora of factory ecm's in the junk yards, someone would've cracked one to dump all the info, and be able to put whatever you want on it. I can get a factory pcm from a 96-2003 Blazer for $15. All it would take is a to make a wiring harness, I'm not scared of that, I actually enjoy wiring, and then the software to be dumped in and start tuning away. I just hate to spend $2,500 and up for something the factory did fine the first time and you get a piece of software too. Too bad that software wont work on a factory pcm :x

 

[crd89stang]

the easiest way in my eyes is ford efi you could use a mass air computer etc buy the prof products intake and rails and use all ford electronics only problem is some fab on the distributor . still gets expensive with fuel pumps injectors etc the stock injectors 19 lbs are close to there limit at 300 but used ford injectors and maf sensors are a dime a dozen if going on the cheap you could use a 190 or 255 in tank pump use the stock delivery line and just run a return line . like someone else said you can use a throttle body fom whatever you can find with a big enough blade chevy has a pretty big one from what i can remember this is basically the kit u see in the mags

 

[StreetBu]

But with the Ford system your into burning chips again, so thats a no go for me.

 

[crd89stang]

no with maf the meter compensates for differences as long as meter is calibrated to the injectors i have done this with a bbc chevy before

 

[JP86SS]

"Burning" chips or saving to the emulator is basically the same thing.
Emulators are the way to go for tuning but when you are done do you want to leave the $200 device in there or a $5 chip on a $15 adapter.
Tuning overall is worth the effort, MAF can only use the preprogrammed limits to adjust for the amount of fuel based on the airflow reading.
It can't correct or adjust for spark any better than an SD system can. That's where the power is at.
Eventually you will want to adjust something if you want optimal performance/drivability.
PCMs are still expensive to program, The older ECMs have good functionality and are fully researched for source code.
Modifications to add WB, EGT or any other function are possible. Guys are running NA and boosted apps on the same hardware (7730s or 749s)
WB fueling IIRC is already in the $59 code with other enhancements. Just need to dig a bit to find how to use it.
I only wish the nerw stuff was documented as well (for less than the cost of a kidney!)
jp

 

[Doober]

I'm kind of in the same boat for EFI. I put a set of Vortec heads on last year (have to yank everything back out for rings :roll, and was thinking about Vortec injection. I'm on http://www.fullsizechevy.com and asked over there, but either a)nobody knows, or b)nobody cares enough to answer the question... besides the obvious stuff (crank sensor, different distributor/intake/injection), I don't know if I can even convert my motor ('88 block) over, partially because I don't know what I need, partially whether or not it will fit, and partially whether or not it will run with my cam.

 

[starfire350]

the injection system would be easy to bolt on, programing is the catch and if the injectors could keep up with your fuel needs. not alot of options for those injectors.

 

[jrdrag]

It would take an aftermarket computer to make it easy to swap injectors. Most injectors will fit in the holes as long as you have the correct hardware to control them properly.