65 Fuel Injection

[Jerry G.]

Any recommendations on books or articles pertaining to 65 injection operations? I'm a novice when it comes to fuelies, but I purchased a car with a 65 unit and I need to know the basic operations. It runs fine other than at cold idle. I know the fast idle cam needs a little tweaking. It does not set as it should when cold. It surges up and down when idling. Vaccum leak? Opinions? Thanks.

[Greg M.]

Re: 65 Fuel Injection

You may want to check out Jerry Bramlett! He has a great website and is very good with the fuel injection units! He rebuilt mine for my 1960 a few years ago and is a true pleasure to work with. #1 in my book!

http://www.jerrybramlett.net/

Greg
60 Corvette

[Jim L.]

Re: 65 Fuel Injection

Any recommendations on books or articles pertaining to 65 injection operations?

To gain an understanding of how fuel injection works, and I mean how it really, really works, I suggest the following:

Find a shop manual and study the technical description of the operation of the unit. Have your FI unit nearby for a visual reference as you read what each sub assembly does. Repeat this several times.

THEN....

Find a copy of the 1957 SAE paper titled "The General Motors Fuel Injection System" presented by Dolza, Duntov, and Kehoe. Absorb what these three gentlemen wrote.

You'll notice subtle differences in the description of air and fuel metering between what the shop manuals all say and what these gentlemen say. Pay attention to the words of these three gentlemen!

Once the words of the original developers of the FI system "sink in", you'll know how your unit works and it'll never again be mysterious.

Good luck,

Jim

[Joel F.]

Re: 65 Fuel Injection

I'll second everything Jim wrote (he also happens to be very knowledgeable about fuelers!).

I have found the ST-12 manual to be particularly helpful and well written when it comes to understanding the theory of Rochester FI. Before you do anything, I'd try to find a very basic article called "The ABC's of Fuel Injection" written by Rochester to give people an overview of the theory of how fuel injection works.

Good luck! I'd become very comfortable with the things mentioned here before you turn a single screw or adjust anything.

Joel

[John D.]

Re: 65 Fuel Injection

Jerry,I agree with the above suggestions on how to learn about your 65 FI unit.
Here's the problem and why the mechanics had so much trouble fixing the midyear units. The manuals they were told to use were poor at best. The 63 shop manual shows nothing about the typical high pressure pump used from 57 to 65. All it tells you about is the wobble pump. Jerry your car has a gear pump. The 63 manual was written using a sand cast prototype unit.
You need an extensive library to really learn the theory behind what makes a fuel injection tick. Then if you are like me you need to read and reread the theory.
My favorite fuel injection manual for the 58 to 65's is "The Corvette Servicing Guide" also known as the ST-12 manual.
Then of course you need the 63 shop manual.
Last manual you need to refer to is your 65 supplement although it only has about 1/4 page of info on starting. But this is very important.
Also refer to your owners manual on how to start the car.
All those manuals are available from NCRS,etc.

Here's a old story. Back in 1961-1962 I was a student at the GM Training center. United Delco courses. My sponsor was Grabiak Chevrolet.
Anyhow one of the courses I signed up for was the ABC's of fuel injection. That may not be the correct title but it was the fuel injection course.
The instructor was Paul Glagola. So I took a big test one day and flunked it. Paul hollered at me in front of all the old guys in class. I was the youngest one there. He said DeGregory you didn't listen to me at all. He said you don't know **** about theory as all you wanted to learn was how to turn the screw driver. Paul said any idiot (his exact words) can learn how to do that. It's the theory that counts. If you don't know the theory then you don't know anything.
I never forgot that even though it was almost 50 years ago. JD

[Bruce B.]

Re: 65 Fuel Injection

Jerry,
With my limited experience with Rochester fuel injection I have learned one thing.
That is, if it runs well don't try to improve it.
Tinkeritis can be your enemy.
Learn the theroy, get it running properly and drive it.

[William C.]

Re: 65 Fuel Injection

I have a PDF file in black and white of the "ABC's" presentation. It is too large to manage here (approx 3+Mb) but if someone want's a copy, drop me an email to: "Wclupper@neo.rr.com" and I'll see if my mail server can handle the file.

[Duke W.]

Re: 65 Fuel Injection

To gain an understanding of how fuel injection works, and I mean how it really, really works, I suggest the following:

Find a shop manual and study the technical description of the operation of the unit. Have your FI unit nearby for a visual reference as you read what each sub assembly does. Repeat this several times.

THEN....

Find a copy of the 1957 SAE paper titled "The General Motors Fuel Injection System" presented by Dolza, Duntov, and Kehoe. Absorb what these three gentlemen wrote.

You'll notice subtle differences in the description of air and fuel metering between what the shop manuals all say and what these gentlemen say. Pay attention to the words of these three gentlemen!

Once the words of the original developers of the FI system "sink in", you'll know how your unit works and it'll never again be mysterious.

Good luck,

Jim

The basic operating theory of the Rochester mechanical speed density fuel injection system is relatively simple, but some parts of the implementation are a little complicated. The shop manual referred to above with a detailed FI explanation is the 1963 Corvette Shop Manual, which is a basic manual for your entire car, and you'll also need the 1965 Supplement. Just remember that the "wobble pump" described in the '63 shop manual writeup was a short lived failure, and '63 units quickly returned to the gear pump.

The '65 Supplement covers changes from '63 including the cold start system that eliminated the problematic cranking signal valve.

The SAE paper is still available from SAE, but it's fairly expensive for non-members. NCRS should add it to their available pubs for sale.

Duke

[Jim L.]

Re: 65 Fuel Injection

The basic operating theory of the Rochester mechanical speed density fuel injection system is relatively simple, but some parts of the implementation are a little complicated.

Not to pick nits, but the Rochester FI doesn't use speed/density air flow metering. It uses mass air flow metering.

Therein lies the beauty of the system. Once calibrated for a particular engine, it's virtually immune to changes in air density, whether caused by atmospheric conditions or operation at different altitudes.

The SAE paper is still available from SAE, but it's fairly expensive for non-members. NCRS should add it to their available pubs for sale.

It shows up once in a while on EBay and that's where I found the original copy I have.

Jim

[Duke W.]

Re: 65 Fuel Injection

Not to pick nits, but the Rochester FI doesn't use speed/density air flow metering. It uses mass air flow metering.

Jim

My "speed-density" characterization was incorrect, but not for the reason you describe.

The air meter does not measure mass flow. Like a carburetor, it only measures volume flow, so there is no correction for air density variation due to ambient temperature and pressure (including altitude.)

Most modern cars use "hot wire anemometers" to measure mass flow, and some earlier FI system like Bosck K and L-Jetronic used "momentum valves". The Bosch D-Jetronic was a speed density system. The primary inputs to the ECU were manifold temperature and pressure, which the analog ECU used to continuously compute manifold air density using Boyle's Law. Add input from the speed sensor and you have a speed-density system.

Duke

[Jim L.]

Re: 65 Fuel Injection

My "speed-density" characterization was incorrect, but not for the reason you describe.

The air meter does not measure mass flow. Like a carburetor, it only measures volume flow, so there is no correction for air density variation due to ambient temperature and pressure (including altitude.)

I'm not a degreed mechanical engineer like you, Duke. I'm but a simple EE. So I can't debate fluid mechanics with you.

I defer, instead, to John Dolza the inventor of Rochester FI who, in the 1957 SAE paper wrote:

"The control method selected for our injection system is based on mass flow metering in which venturi throat depression is related mechanically to fuel pressure."

and

"The air velocity through the venturi causes a depression signal related to the mass air flow."

That sure doesn't sound like volume flow to me.

Jim

[Duke W.]

Re: 65 Fuel Injection

A venturi only measures volume flow, not mass flow. I discussed this paper with one of my professors as an undergraduate, and he was as perplexed with the "mass flow" claim as I was. All we could assume was that their "mass flow" claim was based on volume flow at some "standard" air density like standard sea level conditions.

IIRC the paper states that the air meter flows 24 lbs/min (If you have the paper handy, maybe you can verify this number.), but does not state density or test depression. I wanted to compare the flow rate with contemporaneous carburetors, but without stating the depression, it was impossible. I suspected that the incomplete data was meant to disguise the system's actual performance from the competition.

If I assume 1.5" Hg, which was/is "industry standard" for measuring four barrel carburetors then the ('57 vintage) air meter flowed equivalent to a 300 CFM four-barrel carb, which seems deficient. Later air meters flow more. GM never updated the paper, but others have flow tested the '63 to '65 air meter and it flows about 600 CFM at 1.5" and can be improved to about 750.

Like a carburetor, the FI air meter measures volume flow.

At a given depression, volume flow can be measured and it will be the same at sea level or 5000 feet in Denver, but the Denver mass flow will be less due to lower air density.

Duke