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Discussion Starter · #1 ·
than 1-3-2-4 in cruise mode. Or so most people say right? And the back 4 are richer than the front at WOT.

I think, just maybe, it's because the primaries are forward of manifold and valve group centerline, and the secondaries are aft. The back 4 primary runner length is a bit longer than the front 4.

So, if that's right, what to do?



:cheers: :cheers: :cheers:

I actually have a better answer, but I'm not ready to discuss my manifold design just yet.
 

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AlwaysWave said:
I actually have a better answer, but I'm not ready to discuss my manifold design just yet.
You are killing me with this Top Secret design of yours!
 

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AlwaysWave said:
than 1-3-2-4 in cruise mode. Or so most people say right? And the back 4 are richer than the front at WOT.

I think, just maybe, it's because the primaries are forward of manifold and valve group centerline, and the secondaries are aft. The back 4 primary runner length is a bit longer than the front 4.

So, if that's right, what to do?

I actually have a better answer, but I'm not ready to discuss my manifold design just yet.
According to the Corvette Fuel Injection and Engine Control Managaement System Handbook for 1982-2001 that phenomenon is characteristic of carbureted engines. In order to provide, at a minimum, the stoichiometric fuel ratio of 14.7:1 to all cylinders, some cylinders will run richer (and depending on load, spark advance, and manifold vacuum, sometimes leaner).

According to the book, fuel injection became standard on all Corvettes because of emissions requirements. Using an oxygen sensor in the exhaust, and Seqential Port fuel Injection, the Engine Control Management Module can vary the amount of fuel injected to each cylinder individually. You can't do that with Multiport injection because it supplies fuel to a ganged-group of injectors (typically one bank) and older fuel injection systems supply fuel to a regular intake manifold. The O2 sensor can also detect whether you are using oxygenated fuel and change the stoichiometric fuel ratio to 14.2 to account for the extra oxygen in the fuel.

You might want to pick up a copy of the book as it goes into great detail (but in English, not engineer-speak) on the behavior of carbureted engines, especially intake manifolds. The section is short, since the book is devoted to fuel injected engines, but is none-the-less a fascinating and informative read. The book also goes into great detail (with pin-outs, schematics, and trouble shooting charts) on the operation of the ECM and related microporcessor-based systems and sensors in the Corvette.

Ray
 

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took the words right out of my mouth,and i have that book,it's priceless.:thumbsup: :smokin:
 

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Discussion Starter · #5 ·
Where might I find this book?
"Corvette Fuel Injection and Engine Control Managaement System Handbook for 1982-2001"
 

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my friend has it right now,(common :laughing: )or i would put the publishers web-site.i think mine came from Borders books.it was a gift.if someone doesn't post,i will find out tomorrow.the book has LT4 & LT-5 also.:thumbsup:
 

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AlwaysWave said:
Where might I find this book?
"Corvette Fuel Injection and Engine Control Managaement System Handbook for 1982-2001"
Barnes & Noble, Borders, Amazon.com.

The ISBN number is 0-8376-0861-9. It is $34.95 (if you have a Barnes & Noble Reader's Advantage Card you get 10% off but it only pays to buy one if you buy a lot of books).

The author is Charles O. Probst, who unfortunately died in 2000 one week after sending in the final changes for the book. It's sad to lose someone whose writing is so lucid and expository.

For someone who modifies engines as extensively as you do this book would be very useful, even if all you wanted was the theoretical knowledge and not the hands-on trouble-shooting.

As I mentioned in my original post, the book is primarily concerned with FI and the ECM and sensors. But it offers a very good explanation of topics such as ram air effect, intake manifold runner length and its effect on torque production, spark advance, etc.

Ray
 

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he was also on many of the fuel injection corvette design teams.which really helps.theres little stories in there to.like the rumor that G.M. corvette OBD 2 computers had two modes-performance and smog.when you went to get the car smogged,the inspector would open the hood,and a switch would be wired the hood light.then the computer would go into a preset emissions setting from the factory,thought that was very funny.

good info on the book numbers. :thumbsup: :smokin:
 

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Discussion Starter · #9 ·
Thanks for the info guys:thumbsup: :cheers:

I'll be hunting down and buying that book.
 
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