DFI Question..?

[UR50SLO]

We have two FAST systems. I am unfortunatly going to start off with a Old DFI.
The DFI I have looks very similar to the stock ECM. So i'm sure it's faily old. What Injectors could I use with that system>? 65lb/hr+?
I'm running a 3.8L block with Champion ported heads solid camshaft with a 72 turbo. Thanks for your help, Scott~

 

[64duece]

It's been debated

The unit was not designed for low impedance injectors like your #65's, but I've heard people have run them without toasting the driver. They said something about not running the injector near static but, it really comes down to how long the driver will handle the increased current before it cooks. Otherwise, you could play it safe and by an Accel Variable injector controller (VIC) that has the auxillery driver needed. It's like $400. Good Luck

 

[UR50SLO]

Thanks!

Thanks.. There's two reasons why I think I'd like to start off with the DFI. First I've never tuned one and I need to get some time working with the old systems. I am definatly going to run this set of 65lb/hr Inj on the system. The guy I bought it off of said that it would handle any inj. that I wanted to put with it..
Second reason is the wiring harness that go's with the system is not the stock harness. It's a very nice harness that gives the engine a clean and unclutterd look.

I'll need some tuning advice when I get closer to running this year.

Lance/Craig did a great job of helping all of us at the last FAST event~ Hope we can get somthing scheduled again this spring!

Thanks, Scott

 

[Reggie West]

The 65s will work with the DFI. From what I have been told, you wont run into problems until you are using 70 pound injectors.

Your problem will be lack of fuel. That 72 turbo will flow more air than what the 65s can put out in terms of fuel. Which means detonation on the top end. Trust me on this. My dad has found out the hard way about this.

He is running a Stage 2 motor, 72 turbo and 84 pound injectors. We had been using a DFI batch fire box for everything. You will need the VIC to drive the bigger injectors. 70 pound injectors will work OK but anything above that you really need one driver for each injector and that is what the VIC does.

The other half of this equation will be the fuel pump. Make sure you have a very good pump to handle the amount of flow that turbo requires. You will see detonation around 19 psi and above using race gas and timing of 16 degrees on the top end of the ignition map.

If you need a good program let me know I can send you a copy of the current race program my Dad is using on his.

 

[UR50SLO]

GRRRRREAT!!!

Excellent. I would like to have a start up program. Who should I call to the the unit to allow bigger inj? I'd realy like to run the right amount of inj for the job. I hate cranking the FP to obtain the fuel needed. done it before though..

Thanks for the help I realy appreciate it!

Scott~

 

[KendallF]

The ECM's driver doesn't know what size the injector is. Low impedance injectors are low impedance injectors. Many people are running low Z injectors using DFI without a VIC with no problem; there's no cutoff at 70 lb/hr or whatever.

If it's a batch fire box, you may have idle quality issues if you go to 84+ lb/hr injectors due to poor low pulsewidth control. The VIC has a nice side benefit of allowing individual cylinder fuel control.

I don't understand why you want to start with the DFI...you can get a nice looking aftermarket harness with the FAST also. It's like beating yourself in the head with a hammer because it feels so good when you stop!

 

[Reggie West]

Kendall is right, the ECM does not know any difference between 50 pounders and 70s.

Give me a day or two and I will send you a program. I would use this as a base and tune it from there.

I know Ken Dutweiler will sell you the VIC and all the harness and goodies that come with it. It does require you putting it in. If you dont feel comfortable with it take it to a shop and have them do it.

I am not sure who is in your area but that is easily remedied.

Good luck

 

[quickt]

DFI batch will work with any injector but anything larger than 72s is very hard to idle. I have many start up programs give me a call or an e-mail and I will e-mail a couple to you.

 

[UR50SLO]

Hey Lonnie....!

This is actualy your system. I bought it off of Chris..
I'll be attempting to use it on my S-10 that I am now putting the Buick Motor in. That would be great if you would send me the program for the largest Inj I can get and what lb/hr it is for.
Thanks!! Scott Klepinger.

 

[UR50SLO]

Kend,Reg..

I love using the FAST systems. It will be next year before I go and spend 25-3000 on a fast system and harness. I'd also like to look into building a stage engine for more stabilty by then too. I'll get whatever Injectors I can run and Idle. 72s sound like the best choice for me now. Hopefully I won't have to crank the FP up to the moon to supply me with fuel. Hopefully I'll not be pounding my head with a hammer too long

Thanks guys... ~Scott

 

[turbodave231]

Hey wait a minute, Some of us like pounding ourselves with hammers..........and some of us like our DFI's too!!!

Harry at Precision told me that a batch fire box only has 4 peak and hold drivers. We only use 3 in a V6 configuration. That is OK as long as you have high impedance injectors. Harry told me that the Batch box will work for awhile with low ohm injectors but will eventually fail a driver.

I opted to buy a VIC to use with my 72's and keep the box alive.

Smaller capacity low ohm injectors (like 55's) will pull more current than larger low ohm injectors (72's or 83's) because the pulse width (on time) must be higher to deliver the same amount of fuel. Right?

Dave

 

[TurboBob]

DFI questions........

The DFI batchfire unit has 4 4amp drivers, 4 amp drivers are intended
for 1.2 ohm injectors. Most of our port-style injectors are 2.4 ohm.
put 2 in parallel and you get 1.2 ohms...... (that's the way they are wired)

So, with 2.4 ohm injectors you are operating the DFI THE WAY IT WAS DESIGNED
TO BE USED . It will be FINE, no problems.

It is true that very large injectors will have idle issues, but that's the way it goes.

The DFI can be used for high impedance injectors also.

TurboBob

 

[UR50SLO]

Which one...?

Low. High. Imp..... Which exact manufacture of Inj should I go with? I'd realy not like to buy the box because im going to buy a speed pro system next year. Thanks for your help guys Scott

 

[TurboBob]

Injectors

How fast do you want to go? those 65's should do fine to about
128 mph or so.....

Bob

 

[UR50SLO]

More more

Here's my setup see what you think.


Stock block,CNC Ported Champion heads,Solid lifter camshaft,Steel caps with girdle, Wiesco pistons,Stock crank,rods, Front mount IC, 66-72mm turbo,Bracket to run just the Alt/waterpump,stock lower intake with hemco plenum and 70mm TB, THDP3"

Trans: TH400 with Trans brake and 38-4000stall

Rear end 3:89 w/detroit locker 9" ford with 10.5slick

Body 10pt Xbrace cage certf to 7.50 does have interior truck should weigh 2700lbs with me in it possibly less. Ladder bar with coil over style rear susp. 90/10s in front and springs.

I'm expecting to run mid 9's with out much trouble with good gas and mid 20's boost. (crossing fingers)

Thanks again for your input, Scott~

 

[turbodave231]

If you want to run 9.50's with a 2700# car you will need at least 622 RWHP. According to Joe Lubrant's chart you need:

69#/hr of fuel at 80% duty cycle
61#/hr at 90%
55#/hr at 100%
and 53 gal/hr pump output

this all assumes a BSFC of .5 which should be close for our engines.

I talked at length with Harry at Precision and the Tech guys at Accel before I bought the VIC to run low ohm injectors. They both said the batch ECU could handle the low ohm injectors for a period of time but that a driver failure could occur.

Dave

 

[turbodave231]

To answer TurboBob's reply: Quoted from Accel's EMIC training manual (installer's training course)

"A standard 015013 ECU incorporates 4 4/1 drivers and has the ability to fire 8 low impedance injectors for short periods of time. Due to the drivers used in this ECU, long duty cycles in conjunction with the fact that it is simultaneous double fire coded will cause overheating of the ECU (see tuning section for further explanation). The ACCEL sequential fired ECU uses 8 individual drivers and has no current ar duty cycle constraints."

You can use low impedance injectors with a batch fire box if you want.....it will work......for awhile. I'll stick with my VIC

DR

 

[JDEstill]

In regards to Dave's suggestion, I'd be a little more conservative...

It's one thing to push injectors you've got as far as you can, but when you are buying something new do it right and make sure it is big enough the first time. Don't risk buying injectors and finding out they are a little too small and then having to crutch things (or upgrade the injectors again).

So, I'd suggest that when looking at Joe L's spreadsheet, remember that his injector size calculation is based on the rear wheel hp that comes from the weight/mph you are looking at. You will need more flywheel hp to run that number due to drivetrain losses, and therefore need more fuel and injector than what the spreadsheet says. How much more depends on the amount of drivetrain loss, could be a little, could be a lot, I dunno, just take it into account.

Also, I'd suggest using 0.6 BSFC instead of 0.5. If you size the inj for 0.6 and then achieve 0.5 then great, you've got plenty of injector, but if you size for 0.5 and can only get 0.6 for some reason then guess what? You're buying injectors again. Be on the safe side (ie the conservative side)! Too large (within reason of course) beats too small hands down. IMHO anyway

John

 

[turbodave231]

John,

I couldn't agree more!! The numbers I posted came right out of the calculations and don't give any room for loss or error. If I were choosing injectors for this application I would go #84's which would give some room for tuning and future upgrades.

I have run injectors at 100% duty cycle and I have lost a few head gaskets when I came too close to the edge.

For what its worth.......

Dave

 

[UR50SLO]

84s..

Alright .. .so I'll run a set of 84's Are they the low imp injectors?


Makes me think I should just put this on the wifes car and get a FAST system now! Humm.. Maby that's just what I'll do. This is becoming too much of a Pain in the Butt. Especialy when I realy don't want to use the DFI anyway.
The wife's car is just a basic built budjet motor with decent parts 11's would suit her fine.

I realy don't want to "Tune" my truck with a unfamilar setup. I'd proably lean it out and hurt it just from inexperience with the DFI and then have to spend more money repairing the engine with money I Could have used to buy the right system the first time. I've only got 300.00 in the DFI so I'll toss that onto her car and learn with it. I'm glad this was such a debatable topic.. it's been a learning experience. Thanks guys~~ FAST system bound..~Scott