91dime

Ok im kinda new to the accel dfi systems, Im planning on getting one for my 4.3 in my s10. I know this is a fbody site, but you guys are all farmilair with these systems so im asking for any help. Does anyone know any links to a site that would explain what needs to be done, and maybe how to set up a mpfi on my 4.3? Also what system should i go with? I was thinking accel #77025U-3, thats the 3 bar one, what do the bars mean? Any help would be greatly appreciated, thanks.

Toehead

The bars are the resolution of the MAP sensor. A 3 bar map sensor can read boost over a 3 bar range... up to 28 psi of positive pressure. You shouldnt worry about that unless you are going to turbo it. A 2 bar would be fine.

I don't know anything about the accel systems however.

91dime

Well actually im turboing it, so do the bars read the intake pressure? What would a 3 bar read? Do you know any sites tha i could read up on this more? Thanks alot for the reply

Toehead

Yes, a bar is a unit of pressure. It reads the manifold pressure in order to determine how much fuel to inject, using the speed-density algorithm. From this algorithm, the ECU can figure out the density of the air in the manifold at that instant. When combined with the engine displacement, RPM, and volumetric efficiency (Basicall the efficiency of the engine's ability to pump the air at that specific rpm), the computer can calculate the mass flow rate of the air. Once the mass flow rate is known, the computer injects the correct amount of fuel for a stoichiometric burn at cruise, or a rich burn for WOT.


The three bar map sensor can read up to 28 PSI of boost. If you want to go higher, the 4 bar can read 44psi of boost.

91dime

Ok Im taking a guess here, but do the bars pretty much tell the injector when to fire and how long it injects or how much fuel to inject? If i run a 1000cfm accel throtle body or a 58mm fbody throtle body and a aftermarket dfi system will the system require a map sensore? or do the bars pretty much do what a map sensor does?

Toehead

the map sensor is just a pressure gauge.
The bar designation just tells you how much pressure range it can measure.

The MAP sensor takes the place of the MAF in most fuel injection setup.

91dime

The bars tell me the range of how much pressure the MAP sensor can measure? Sorry about all the questions, Im just trying to figure this out. And I should look for a 3 bar system becouse im turboing it? I really apreciate the help, thanks

Toehead

right. A bar is a unit of pressure, much like psi.
1 bar= 14.5 PSI.
a three bar MAP sensor has a useful range of 3 bars of pressure.
remember that the sensor also reads vacuum, so that range includes some vacuum.


A three bar MAP should be enough. How much boost do you plan to run? You won't need more then a 3 bar unless you do some serious bottom and top end upgrades to go along with that turbo.

91dime

I dont plan on running more than 15 psi 20 if i decide to build the bottom end up.DO i need a 3 bar, becouse wouldnt a 2 bar be able to measure up to 29 psi? or do i have to figure in atomspheric pressure?

aDFIguy

You need to figure in the vacuum range (where your engine operates at less than wide open throttle). 1 Bar vacuum + 2 Bars (~29 pounds) boost = 3 Bars total measurement range of the 3-BAR MAP sensor.

The ECM uses Engine Speed and MAP reading to look up a ton of functional values when it is running your engine. In the case of an ACCEL system, it looks up Target Air:Fuel ratio, Ignition Advance, Base Volumetric Efficiency, and a bunch of other stuff against MAP and RPM in order to generate the correct fueling and ignition values needed by the engine at any given point in time.

You seem to be on the right track with the 77025U-3 system. Your best bet is to talk to a dealer about exactly what you need, they'll be able to answer specific questions for you. Let me know what area you are from, and I can probably direct you to someone (somewhat) local to you.

91dime

Im from Moundsville WV 26041, there arent many local places i know. Im only planning a turbo that will deliver 12 psi max, i dont really think the bottom end will handle more. I got the pdf instructions from holleys site for their commander 950-101. I uderstand that a open loop system uses the map sensor and tps sensor, as well as all the temp sensors to calculate how much fuel to deliver. I dont think i should run a closed loop system.Im between the holley commander system and a accel system. Will the accel 77025U-3 system run a V6? Do you think the accel or the holley would be better?

aDFIguy

Any DFI system is capable of running a V6. The whole system is software configurable so that one ECM can be programmed to run a wide range of 4-8 cylinder engines. It's mainly the supplied calibration and wiring that varies from kit to kit.

If you're planning on a max of 12 psi, go with a 2 Bar MAP sensor. The tuning resolution will be much better, and it can support up to about 14.5 psi.

The DFI system is quite a bit more flexible than the Holley system. I'm a little biased in offering opinions on that subject, but basically, you get what you pay for as far as the cost/features/capability of the 2 systems. As you try to do more with each system, the differences become very apparent.

Here's the email address for a dealer in Virginia. Please let me know if he is helpful or not.

replace the[:AT:] with @

one94ta2try[:AT:]aol.com

91dime

ok thanks alot for the help, so i can still get a new accel dfi that will wor
k with my system? I was kinda looking for a dfi 6, but they dont make it anymore, they have the dfi 7. Which system would you prefer?

91dime

im between the accel dfi universal 6 cyl kit #77025U-2, or the holley commander 950, # 950-101.

aDFIguy

Get the Gen 7, don't even consider wasting your time on an older Gen 6 model.

The Holley system is somewhere between the DFI Gen 7 and Gen 6 boxes. Kind of an updated Gen 6 with a few modern features. Like the Gen 6, it's becoming a pretty dated system that operates using much older and much less flexible control strategies than are found in current ECMs.

91dime

i emailed that guy in VA, do you know any online dealers? Im either going with an accel gen 7 or the holley commander. I hate to say this but its pretty much whatever i can get a better deal on. I shouldnt cheap out but theres going to be alot of money involved. thanks alot for the help. also i have xp on my lap top are both systems compatable with xp?

aDFIguy

Both should work fine with XP. You may have to get a USB to Serial adapter if you don't have a 9-pin serial port on your computer.

bluegoose

I have the GEN VII and once I got it tuned, I thought I went to heaven. I just love the GEN VII.

hey there DFI Guy.. hope thinks are good for you, my car is running sweet!!!

91dime

yeah i think im going with the gen VII to run my 2.8

91dime

Ok I finally decided on a engine. Im going to use a buick 3.8 and set up a mpfi system for it.I wanted to use a dual plane intake because of its rpm range, but i was told that the dual planes are good for low rpm because they atomize air better at lower rpms, and single planes to better at higher rpms because of more air flow at the higher engine speeds, witch helps atomize the fuel. And if using a mpfi system, the injectors atomize the fuel, so a single plane is fine for low rpms. Is that correct? This is the intake I would like to go with http://store.summitracing.com/partde...?part=WND-7541
And use a dfi management system. The turbo buicks used a crank trigger with coil packs, but im going with a distributor because of the simpleness. Does this sound like a good idea?

aDFIguy

Sounds like a pretty good plan. You'll be a little better off with the distributor vs. coil packs if you plan on using the rev limiters built into the DFI controller. Due to the way it works, the Buick ignition module doesn't offer a really good way of letting an ECM rev limit the engine by dropping cylinders. A distributor solves that problem nicely.

91dime

Yeah I didnt understand how that would work if I used the coil packs, doesnt accel make a ECM for the GN engines. I figured It would be much easier to just do a mpfi and distributor. I was looking at a BBK throtle body, what do you think about them?

aDFIguy

The 77025 kit is for the GN v6 engine, and comes with a 2 Bar MAP sensor. You'll have to check around to find a distributor for that kit, it's pre-wired to work with the GN ignition module. Once you find a distributor, wiring it in and configuring the ECM is very easy.