Never Finished

Has anyone installed either one of these units, a Holley 950 series or Edelbrock 3500 series port fuel injection unit? Will either fit with the stock air cleaner and small block hood? Are they relatively easy to tune in? Likes/dislikes?

PatsLs1vette

Well welcome to the forum first of all,and i had the holley setup awhile back didnt like it had problems with it after a while,air cleaner fit on it.Im not sure on the edelbrock setup.,somebody else will chime in im sure and express there oppinions as well,theres always someone on here that has tried something.I like the look of the edlebrock better.I also had the older holley setup ,thats why i had problems.


[Modified by patsnitrovette, 5:58 PM 1/30/2003]


[Modified by patsnitrovette, 6:26 PM 1/30/2003]

zwede

I have the Holley 950 on my 454. I like the system. Very flexible. Lack of flexibility was the main reason I didn't go with the Edlebrock. It still uses a chip, and then you can fine tune it with a hand held controller. The 950 is completely tuned by a lap top and no chips.

The edelbrock will also not let you run closed loop below 1800 rpm, which I didn't like. My 454 is mild enough that I can run closed loop all the way down to idle.

VetteNut72

I am running the Edelbrock ProFlo EFI and two of the reasons I bought it are the fact that it comes with a base chip tailored around your engine and that you do not need a laptop to adjust it. A baseline setup can be appreciated when spending time trying to work out fuel and spark map baselines on an unprogrammed system and spend even more time fine tuning those baseline maps. I also do not own a laptop and did not want to buy one just for the car. Most of the adjustments that can be made to the base calibration are +- 50% which lends a great deal of flexability to EFI calibration off baseline.

Also, there is an individual who has completely reverse engineered the entire system and all technical data is available including EFI computer code, display/adjust unit code and communication protocols. The interface to the computer is a basic RS232 interface and can be adapted to the serial port on a PC. He also did not like the fact that the system would not close loop below 1800 rpm so he modified the code to allow it.

Here is a link to the information mentioned http://www.sonic.net/~mikebr/efi/main.html




[Modified by VetteNut72, 5:24 PM 1/30/2003]

Never Finished

Thanks for noticing I'm a new member. It will be awhile before I know the ropes. Thanks for the info, too. The picture of your Vette shows a TPI. Are you pleased with it? What is it? How did you choose it? I bought a couple of books on TPI, but I can't find one that tells me how to select one, what parts to buy, and what to expect in the installation. Any suggestions? I'm sure you could write a term paper on this, but a little direction is all I'm looking for.

Never Finished

That is one fine web site. It will take a while to digest it all. I don't have FI now, consequently, this may sound dumb: what does closed loop mean and why is it better for idle?

BigBadRed

Closed loop refers to the presense of an oxygen sensor. The computer uses the reading to decide wether or not the engine is running rich or lean and then adjusts the fuel map accordingly. A perfect fuel map would not need one, but that is basically impossible so that is why the o2 sensor is used. An Open loop system is when an 02 sensor is NOT used and the computer makes its decisions mainly on throttle postion and vacum.


I have holley projection, and a 3rd party software to make it easier to program. It takes a LONG time to program it right with lots of learning curve. Since this is the C3 forum, I will assume you have a c-3. Running the new fuel lines will be critical or you will not be able to adjust the fuel pressue correctly. keep this in mind, as it is not an easy job, and may require gas tank mods.
--marc

VetteNut72

Quote:
______
Running the new fuel lines will be critical or you will not be able to adjust the fuel pressue correctly. keep this in mind, as it is not an easy job, and may require gas tank mods.
______
:iagree:

I'm in the process of correcting my fuel line and tank problems now. These things are critical to satisfy the high pressure (50-60psi) that the MPFI requires. Adequate return line size is an equally vital component to alleviate fuel rail pressure buildup.

Harry74

I added the Edelbrock system to my '74 about two years ago, and I ahve to say it was one of the best projects I've done. I am not sure how far back the archives go, but if you search on my name you might find the threads I wrote documenting the install proceedure.

The fuel line was one of the tough parts, the second piece was locating the computer. I choose to put it in the compartment behind the passenger seat and that required extending the wiring harness and running it thru the bulkhead.

If you do decide to go this route, feel free to drop me a line with questions and I'll be happy to answer them, as time permits.

Best regards,
-harry

69stingray

Great discussion. Harry, not being a "close-loop" system, have you noticed any draw backs? I was leaning towards Edelbrock system, but there is a lot a talk about not being adjustable. I kinda like the fact I don't need a computer to run it. Currently I am thinking TPI but you have to fine a used unit with the harness, pro-flo intake and runners to make up some higher RPM torque, then the "tuning".

How is the low RPM torque? It is a single-plane manifold isn't it?

Here is a webpage with a dyno of an engine with the Edelbrock system:
http://www.geocities.com/MotorCity/7610/dyno.htm
Here is someone else's swap:
http://www.sonic.net/~mikebr/efi/main.html

Harry74

The system is only "open loop" during idle, once you get over 2000rpm and a certain vacuum (ie: at cruise speed) it can be used as an open or closed system, there is an option on the control panel to decide how you want it to act. On my highway paramaeter set I go into closed loop, in my hotrodding set I leave it in open loop.

I would not say that the system is not programmable, you can store three sets of parameters on the handheld control panel and each of these has a decent range on the spark and fuel maps, not to mention idle speed, etc. The maps are not as granular as on some of the high end systems, but to tell you the truth it took me months to really fine tune the unit as it is, I would not have wanted it to be much more granular. Now if I was running a blower and nitrous and switched cams every couple of weeks, this would not be the system I would choose. But my engine is pretty set the way it is and so this system works great.

The knock against the Edelbrock has been that you have to order a baseline chip that matches your displacement/cam configuration. But you really can do a lot of fine tuning above the baseline that the chip provides. I actually have three sets of parameters set on mine, one for everyday driving, one for hotrodding, and one for passing emmisions, which the car has now done twice :blueangel: .

The one thing I didn't like about the system was that no one made a "sniffer" for it. When I was tuning it, it would have been great to be able to get a read out of timing, fuel pulses, and emissions in real time. From the post above it sounds like someone has come up with a way to sync the Pro-Flo to a laptop. I might have to dig a bit deeper into that :cool: .

Oh you asked about torque :D , to quote one of my favorites, "it gets bent out of shape, and it's hard to steer, but I get rubber in all 4 gears" Seriously, there is no shortage of umph and I am running a fairly stout cam. I do have fun letting the idle drop down to where you can really hear the lope in the cam and then running it up to 6500rpm. Remember, for port injection there is not much benifit to a duel plain manifold, the reason you use one on a throttle body or carb setup is to get around the fluid dynamics of the air/fuel mixture, with sequential port injection you are just moving air thru the manifold. And before anyone flames me, tuned port is a horse of a different color, there you are trying to match harmonics for each cylinder and stuff as much air at low rpms as you can, and remember the trade off is you loose all high rpm power.

Wow, fun to be back!
-harry

SmokedTires

You have mail :) And welcome to the forum, lots of good Corvette knowledge here :cheers:

69stingray

Good information. I think I am leaning back toward the Edelborck system. Does anyone know the injection size on the Edelbrock unit? I need a 30 lb/hr injector.

Here is a good tech article on injectors:

http://www.holley.com/HiOctn/TechSer...l/Artcl07.html

groovyjay

I'm also in favour of the Edelbrock EFI. I have it on my BB 454 and I had it fine tuned on dyno before the engine went back in the car. I got the numbers that Edelbrock says it does, so I was pretty pleased with it. As for clearence it doesn't clear BB C3 with small block hood! :cheers:

69stingray

Harry, searched for some of your old posts but I think they were to old. Just for curiously, how is your engine setup? Cam, heads, compression, etc.

Thanks.

Harry74

Bummer, I did a fairly good job documenting the process I went thru.

The motor started life as the "numbers match" 350 punched out to 355. The bottom end was done by "The Machine Shop" here in the Chicagoland area. It is your basic balanced and blueprinted lower end. To that I added all the standard stuff, 10.5:1 Keith Black pistons, dual roller timing chain, high volume oil pump, arp studs and bolts, etc. Then I topped it all of with the Edelbrock RPM package; RPM 2.02 aluminum heads & RPM cam. This is tied to a standard 4 speed. The exhaust runs out a set of coated headers ( don't remember whose right now) and a full length 2.5" chambered exhaust.

I changed cams after flattening a lobe on the RPM with the wrong size pushrods. I went a with a little milder CompCam, I'd have to look up the specs again. If I end up keeping the car for another season I am thinking about going back to the RPM cam or possibly a solid roller lifter cam, I like driving in the upper RPM range :D The RPM cam was just barely drivable with a carb on it, with the FI it should be a snap to tune in. Plus my current cam is close enough to the RPM that the chip I have in the FI will work with either cam!

I found this link showing the mods I had to make to the tach drive distributor, this may help someone. http://www.corvetteforum.net/c3/harr...n/DistFull.jpg
I'll have to see if I can find any others.

-harry

mountainshark76

Use neither, GM fuel injection is as good as it gets. cheeper. and when you need to service it. Its off the shelf stuff, Checker, Autozone. ect. :lurk:

69stingray

I asked Edelbrock what the injector size was and the fundamental differences between the #3500 and the #3503 units (besides manifold and 750 cfm vs. 1000 cfm). Here is their response:

"The injectors on the Pro-Flo are 29lb/hr units and can support about 475HP as delivered.

The only difference is the throttle body and manifold type, both can support about the same HP.
The #3503 may make just a little more low speed torque."

Since I am after low to mid-range torque, the 750 cfm #3503 may be better suited.

#3503:

#3500:

69stingray

The stock air cleaner should fit fine. Not sure if it would fit under the hood with a stock air cleaner. I have done some measurments and the Edelbrock unit SHOULD fit under my stock '69 hood with the Edelbrock 14" air cleaner and a 2.5" element.

Harry74

On my '74, the stock air cleaner housing was about 3/8" too tall to fit under the hood with the Edelbrock Pro-Flo RPM unit. The element was way too tall. Also, to clear the AIC valve you would need to make an indentation on the air cleaner housing in front of the indentation for the distributor. Since I have a correct '74 L-82 dual snorkle air cleaner I have been really hesitent to "modify" it to fit. Instead I ended up with one of those chrome three cornered Edelbrock air cleaners. When the sun is low on the horizon behind me I can see it gleaming under the hood, looks very cool, but it does not rma any air in there under speed. :(

-harry


[Modified by Harry74, 9:09 PM 2/9/2003]