[Robert Haas]

the LT stuff is all direct injected. trucks cars all of it. before the v-8's it started with the v-6 group first. I linked the below article because it had the best picture I could quickly fornd of the chamber showing the layout of the injector to valve and sparlk plug.
The Direct Injection Flow Path - Porting Factory LT1 DI Heads (enginelabs.com)

Thank you for helping me with this. My mistake is referring to the LS variants as LT's I am sort of an idiot so forgive me.

 

[stoveboltgeek]

Thank you for helping me with this. My mistake is referring to the LS variants as LT's I am sort of an idiot so forgive me.

The way I see it, trifive.com is about sharing knowledge. Sometimes we give it, and sometimes we receive it.

 

[angs1957]

The way I see it, trifive.com is about sharing knowledge. Sometimes we give it, and sometimes we receive it.

Right on Ted

 

[Murph]

As a matter of physics the ram jet was a great advancement but never produced the theoretical improvements expected. Smokey Yunich stumbled on the a probable but controversial remedy. He thought (Rightly so) that introducing cold fuel to the air flow had an adverse effect on velocity and density. He wanted to increase pressure and temperature to the fuel but slammed into the pre-ignition quandary where the charge would not achieve proper cylinder pressure before it would spontaneously self ignite. So he built a cylinder injected engine that injected fuel directly into the combustion chamber like many 2 stroke diesels of the time. He built a mechanical timed injection system and then began experimenting with elevating the fuel temperature and increasing cylinder pressure with a turbo charger. This test mule made it all the way into a running car that Smokey claimed achieved over 50 MPG in the early 1970's

Robert, do you remember the multipage write up in Hot Rod in the early 80s, where he ran the mixture, after the carb, through a heated chamber, so the mixture was burning as it went in the cylinders? He was getting up and mileage increases that were eye opening. Never saw anything about it after that article.

 

[Robert Haas]

Robert, do you remember the multipage write up in Hot Rod in the early 80s, where he ran the mixture, after the carb, through a heated chamber, so the mixture was burning as it went in the cylinders? He was getting up and mileage increases that were eye opening. Never saw anything about it after that article.

yes, He was doing the weirdest stuff. Most of it seemed counter to everything I thought I knew.

He said that heat is energy and if you have to use a radiator you are throwing away energy. He said that someday we would see glass engines. Porcelain maybe.

 

[Murph]

(supposed to be getting HP and mileage increases...)

 

[stoveboltgeek]

yes, He was doing the weirdest stuff. Most of it seemed counter to everything I thought I knew.

He said that heat is energy and if you have to use a radiator you are throwing away energy.

He's right, you know. Heat is actually kind of the default form of energy.

You probably never thought of it this way, but a gasoline engine really doesn't run on gasoline. Gasoline is simply the means to the end.

The heat of the combustion of the gasoline rapidly raises the temperature of the air in the combustion chamber. This temperature rise in turn raises the pressure of the air in the chamber (ideal gas law in action). That increased pressure is what forces the piston downward.

If, instead of gasoline, we could put an electric heating element in the combustion chamber and heat the air to the same temperature in a few milliseconds, the engine would run equally as well, and produce no hydrocarbon emissions. NOx emissions might still be a problem, but that's another story.

The heat put into the radiator and exhaust pipe could still do useful work, if it could be effectively captured and used.

Now, I'm hopelessly unqualified to give an impromptu seminar on thermodynamics but that's it in a nutshell.

 

[BO185]

Direct injection is a misnomer. Injecting fuel directly into the combustion chamber would be the accurate definition of "Direct injection" Except for many Diesel designs it is not done with gasoline engines in mass.

All Gen V motors are direct injection so every GM Gen V V8 since 2014 is DI in mass. Alot of newer cars have DI too in 4cly. I believe ford as this on Eco boost too (not a ford guy through). Now the issue with LT is modification you run out of injector or high pressure fuel pump. So GM runs Direct injection and port injection on the LT5 as it needs extra fuel on the top end.

The down side to DI is the intake valves get dirty and create flow issues from the PCV system putting oil in the intake. So companies have added port injection just to a a way to clean them and will run on the ports to clean then back to DI. Some car companies you have to walnut shell the valves or run a valve clearer. But its the biggest issues with DI

Not all Diesel were DI alot were indirect. Main issue was injector pressure being able to over come compression pressure at time of injections with new higher fuel pressures this wasn't an issue.

Actually, injecting gasoline directly into the combustion chamber is exactly what is being done on many late model engines. This is how they can run 10:1 to 11:1 compression and add a turbo and still (in some cases) run on 87 octane gas. My posing the question of "how can they do that?" is what precipitated the 3 way phone conversation I mentioned above.

They do this as you can control the actual fuel injection event. The time and amount of fuel injected exactly WAY more precise then port injection or carb. So will run fine on 87. BUT... give it 93 or E85 and it really shines.

Diesels do this as well. They do split shots or parcel shots of fuel. This is to reduce emission and reduce noise. The "diesel" noise you here when older ones are running at idle is actually knock. As the fuel injection event is not as metered at idle they detonate. When running off idle it goes away. People didn't like this so they have spent millions reducing this noise in modern trucks and cars. And they are very quiet at idle.

 

[BO185]

yes, He was doing the weirdest stuff. Most of it seemed counter to everything I thought I knew.

He said that heat is energy and if you have to use a radiator you are throwing away energy. He said that someday we would see glass engines. Porcelain maybe.

He's right, you know. Heat is actually kind of the default form of energy.

You probably never thought of it this way, but a gasoline engine really doesn't run on gasoline. Gasoline is simply the means to the end.

The heat of the combustion of the gasoline rapidly raises the temperature of the air in the combustion chamber. This temperature rise in turn raises the pressure of the air in the chamber (ideal gas law in action). That increased pressure is what forces the piston downward.

If, instead of gasoline, we could put an electric heating element in the combustion chamber and heat the air to the same temperature in a few milliseconds, the engine would run equally as well, and produce no hydrocarbon emissions. NOx emissions might still be a problem, but that's another story.

The heat put into the radiator and exhaust pipe could still do useful work, if it could be effectively captured and used.

Now, I'm hopelessly unqualified to give an impromptu seminar on thermodynamics but that's it in a nutshell.

Most early diesels were air cooled. So as they ran cooler but retained heat and used that to do more work with the fuel uses basically. Even water cooled diesel don't need alot of cooling. Look at any big rig running up north in winter and they block the rad completely is temps are low and run fine.

Now they have been working on a compression cycle gasoline engine. Where there is no spark plug. This runs like a diesel and fires on compression. Its more efficient and uses more of the heat from the fuel for work.

(supposed to be getting HP and mileage increases...)

This is why diesels get better MPG and more power vs gas. They use the fuel more effectively and the fuel has more BTU (heat content) then gas lb for lb.

 

[BO185]

What is interesting to me is if you take an stock LS3 put a carb intake and correct size carb it will make more power then an EFI intake. Which is all do to intake design and air flow the carb unit flows more. I think the biggest pictures guys make is they put to large of a carb on a given motor.

I see this all the time on IH's their V8's flow horribly and are designed or torque not HP and redline at 3800. Most flow 350-400cfm max. Guys toss a 650 carb on it and actually lose power and wonder way it will not run right. IH did use 4 barrels but were for the larger 392 and designed to run at WOT for hours on end at redline.

There are some good youtube channels with flow benches were they will flow carbs and intakes. And show the actual numbers. Interesting stuff. My local performance shop as a flow bench and they flow there heads but would like to get my hands on it to play with.

 

[wayne82748]

Interesting...very interesting. I too was under the impression that direct injection is just that, injection directly in to the cylinder as hotrod describes and have recently looked at a DI motor on the stand at Bay Speed in Green Bay. Yes, directly into the cylinder. That brings up the condition that Eco-Boost engines are experiencing, and maybe others. With no fuel flow past the intake valves, and with valve-overlap (read up on that yourself if you like) there is a problem with the intake valves "carboning up". The only solution recommended by Ford is to pull the valves and media blast them. Some misguided people have decided to drill a hole into the intake manifold and fire in some sort of de-carbon cleaner, but Ford says, "Don't do it." Toyota seems to have a mid-ground solution. Many of their engines use manifold feed at low rpms. and then fuel delivery switches to DI at higher rpms. Clean intake valves and the performance/economy of DI. In regard to the Ramjet system, is it possible that GM was over-hyping horsepower gains, and conveniently forgot to mention how troublesome the Ram Jet system could be? How about a Holley FI system...but of course that would mean adding an ECU. I think tuning the 4Jet is the most logical direction. The absolute plus on that is, I have one in my hands and I'm not looking to start experimenting with a replacement carburetor, be it Holley, Edelbrock or anything else. I'm already overbudget. My cousin recently installed the Holley FI system on a Stage II and he now is tinkering with tuning software to get the system to work properly. I love my Bel, but I'm not interested in creating a new career involving FI tuning. As you might have noticed a retired English teacher tends to be verbose (long-winded).

 

[stoveboltgeek]

Wayne, you've asked numerous questions requiring numerous responses. Now, as a retired English teacher, you should have broken these questions into separate paragraphs but let's not worry about that.

Direct injection intake valves - if you go to YouTube, you'll see many videos on this topic. Volkswagen and Audi seem to be among the worst. The problem seems to be blowby and other random vapors and gunk from the PCV system not getting washed off the intake valves.

I've seen discussion of Toyota's hybrid injection solution (The Car Care Nut on YouTube discussed this). Honda forums indicate Honda DI solves the problem by pointing the injector so the intake valve gets a little soaking on the intake stroke.

On the Ramjet - I do believe GM had the best of intentions. See my brief mention of Dean's paper while a college student in 1962 on the Ramjet. https://www.trifive.com/threads/book-on-how-carburetors-really-work.250128/page-2 To me, it looks like GM looked at the Hilborn FI - a successful FI, but suitable only for racing - and said, "how can we make something similar that can be sold to the general public on their daily drivers?". Given the complete lack of electronic management, that turned out to be more difficult to make work reliably than anticipated. About 20 years after giving up on it, electronically controlled port injection was a reality and pretty reliable.

GM published dynamometer test results for the '57 FI on pages 49 and 50 of Site Maintenance . To say they overhyped the performance is to say they fudged the data. I've never observed an independently run dyno test on a '57 FI, so I can neither confirm nor refute the data.

The Holley Sniper is a throttle body system designed to replace the carburetor. Unlike port and direct injection, throttle body injection replaces the carburetor and adds the appropriate sensors and controllers to make it work. While TBI has a feedback loop to keep the air/fuel mixture where it should be, it still has intake manifold issues/tradeoffs just like a carburetor.

By far, the cheapest solution is to address any problems with your 4GC. Rebuild kits are dirt cheap compared to a Sniper.

FYI - some years back, I fought a stumble problem with my 4GC. https://www.trifive.com/threads/geekin-out-on-carburetors.104566/ The stumble mostly happened after sitting at a stop sign or traffic light for a minute or two on a day when it was about 90 degrees or more. Now, at the time, I was using E10 gas. It wasn't until after I changed to a WCFB that I started using ethanol free gas, and that made a world of difference. So, among other things, I recommend using only ethanol free on a carbureted engine, especially with a 4GC.

That said, I think you'll find the discussion interesting. Note carefully the issues of the mounting gasket (4GCs really dislike vacuum leaks). Also note the discussion of using full manifold vacuum on the distributor advance.

All that said - I do think a 4GC can be made to run properly, but you need to work carefully.

 

[stoveboltgeek]

What is interesting to me is if you take an stock LS3 put a carb intake and correct size carb it will make more power then an EFI intake. Which is all do to intake design and air flow the carb unit flows more. I think the biggest pictures guys make is they put to large of a carb on a given motor.

I see this all the time on IH's their V8's flow horribly and are designed or torque not HP and redline at 3800. Most flow 350-400cfm max. Guys toss a 650 carb on it and actually lose power and wonder way it will not run right. IH did use 4 barrels but were for the larger 392 and designed to run at WOT for hours on end at redline.

There are some good youtube channels with flow benches were they will flow carbs and intakes. And show the actual numbers. Interesting stuff. My local performance shop as a flow bench and they flow there heads but would like to get my hands on it to play with.

You bring up an interesting point, especially about the International engines.

Carbureted intake manifolds have to be tuned for the desired application. If you deliberately design the manifold with small runners, that keeps the air speed high at low RPMs. This is ideal for that band - high air speeds keep the atomized fuel suspended in the air instead of dropping out and being deposited on the walls and low spots in the runner. That means you're getting almost all the fuel into the combustion chamber, which means good power at low RPMs. Of course, that also turns into an airflow restriction at high RPMs.

If you design with really big runners, you have the opposite situation - good high RPM power but lots of fuel dropping out of the air stream at low RPMs.

IH designed the engines to start pulling strong right above idle, and to deliver decent fuel economy at the same time. When you're not turning an average sized V8 over 3800 RPM, you don't need more than 400 CFM.

 

[55 Tony]

Actually, injecting gasoline directly into the combustion chamber is exactly what is being done on many late model engines. This is how they can run 10:1 to 11:1 compression and add a turbo and still (in some cases) run on 87 octane gas. My posing the question of "how can they do that?" is what precipitated the 3 way phone conversation I mentioned above.

I am curious about what fuel pressure it takes/they use for direct injection.

 

[BO185]

Interesting...very interesting. I too was under the impression that direct injection is just that, injection directly in to the cylinder as hotrod describes and have recently looked at a DI motor on the stand at Bay Speed in Green Bay. Yes, directly into the cylinder. That brings up the condition that Eco-Boost engines are experiencing, and maybe others. With no fuel flow past the intake valves, and with valve-overlap (read up on that yourself if you like) there is a problem with the intake valves "carboning up". The only solution recommended by Ford is to pull the valves and media blast them. Some misguided people have decided to drill a hole into the intake manifold and fire in some sort of de-carbon cleaner, but Ford says, "Don't do it." Toyota seems to have a mid-ground solution. Many of their engines use manifold feed at low rpms. and then fuel delivery switches to DI at higher rpms. Clean intake valves and the performance/economy of DI.

There are other ways as I mentioned above to do this in post #28. One is to add a port injector to each port. Ford has done this to the ecoboost. The port injector will clean the valve it doesn't run all the time. GM usually says to run a cleaner though the intake to clean the valves. BMW and VW will remove the intake and walnut shell the intake ports and valves. There is advantages to DI. But in max HP effort the port injection works better. There are LT guys plugging the DI and running port injection on max effort engines. Some have even used LT heads on LS motors as they flow really well with DI ports blocked. As I stated before The limitation of DI is fuel flow. They don't design the system with extra capacity to increase fuel to DI injectors. So that is the limit on LT motors.

In regard to the Ramjet system, is it possible that GM was over-hyping horsepower gains, and conveniently forgot to mention how troublesome the Ram Jet system could be? How about a Holley FI system...but of course that would mean adding an ECU. I think tuning the 4Jet is the most logical direction. The absolute plus on that is, I have one in my hands and I'm not looking to start experimenting with a replacement carburetor, be it Holley, Edelbrock or anything else. I'm already overbudget. My cousin recently installed the Holley FI system on a Stage II and he now is tinkering with tuning software to get the system to work properly. I love my Bel, but I'm not interested in creating a new career involving FI tuning. As you might have noticed a retired English teacher tends to be verbose (long-winded).

There are two system port injection and Throttle body EFI. Port injection is better in the fact the fuel isn't in the intake till at the valve. On Holley Sniper its like a carb were fuel is in the intake to mix as it goes and has issue same with a carb of fuel separation. Yes there are gains in intake flow but also need correct intake as stovebolt mentioned to get the fuel to the valve still in the air correctly.

Direct injection intake valves - if you go to YouTube, you'll see many videos on this topic. Volkswagen and Audi seem to be among the worst. The problem seems to be blowby and other random vapors and gunk from the PCV system not getting washed off the intake valves.

The PCV system is the issue its letting oil into intake and gumming up the valves. GM spent Millons on RD just for the PCV system for the LT motors and they still have issues. I tell every one if you buy a new LT based car or truck install a catch can ASAP.

On the Ramjet - I do believe GM had the best of intentions. See my brief mention of Dean's paper while a college student in 1962 on the Ramjet. https://www.trifive.com/threads/book-on-how-carburetors-really-work.250128/page-2 To me, it looks like GM looked at the Hilborn FI - a successful FI, but suitable only for racing - and said, "how can we make something similar that can be sold to the general public on their daily drivers?". Given the complete lack of electronic management, that turned out to be more difficult to make work reliably than anticipated. About 20 years after giving up on it, electronically controlled port injection was a reality and pretty reliable.

GM published dynamometer test results for the '57 FI on pages 49 and 50 of Site Maintenance . To say they overhyped the performance is to say they fudged the data. I've never observed an independently run dyno test on a '57 FI, so I can neither confirm nor refute the data.

I wonder if they flowed the intake on a bench or just made one and ran on dyno. Either way they would have to cast alot on units to weed out the ones that worked. Now its all done on computer modeled. Then 3D printed flow tested in plastic then casted and tested.

You bring up an interesting point, especially about the International engines.

Carbureted intake manifolds have to be tuned for the desired application. If you deliberately design the manifold with small runners, that keeps the air speed high at low RPMs. This is ideal for that band - high air speeds keep the atomized fuel suspended in the air instead of dropping out and being deposited on the walls and low spots in the runner. That means you're getting almost all the fuel into the combustion chamber, which means good power at low RPMs. Of course, that also turns into an airflow restriction at high RPMs.


If you design with really big runners, you have the opposite situation - good high RPM power but lots of fuel dropping out of the air stream at low RPMs.

IH designed the engines to start pulling strong right above idle, and to deliver decent fuel economy at the same time. When you're not turning an average sized V8 over 3800 RPM, you don't need more than 400 CFM.

The IH runners are small and make alot of turns the heads are horrible as well. I seen guys port the heads and make sheet metal intakes and still only get 300-350 hp out of them but that spinning them to 5k. Some have even added port injection to the stock intakes. My 392 stock with 4bbl intake a GM TBI system made 180hp and 400ft/lb or torque at 2500 rpms's at the wheels.

Main issue with the IH motors is vapor lock they are BAD about it.

 

[BO185]

I am curious about what fuel pressure it takes/they use for direct injection.

For gas engines. GM LT is 2000-2900 psi usually. Higher pressure are used on boosted motors to get the injectors to flow more under boost.

Direct injection diesels can be as high as 29,000 PSI! Yes 29k. That is needed to force fuel in as the compression is higher as well as boost on them.

 

[55 Tony]

He said that heat is energy and if you have to use a radiator you are throwing away energy.

So true. That also goes for every single btu of heat from the exhaust system and the exhaust itself. If it's releasing heat into the air, it's wasted energy. As far as if it uses a radiator, air cooled engines are included also.

 

[stoveboltgeek]

I am curious about what fuel pressure it takes/they use for direct injection.

For gas engines. GM LT is 2000-2900 psi usually. Higher pressure are used on boosted motors to get the injectors to flow more under boost.

Direct injection diesels can be as high as 29,000 PSI! Yes 29k. That is needed to force fuel in as the compression is higher as well as boost on them.

Yep, that sounds about right. I've been told they can run as high as 3000-5000 PSI by a retired GM engineer (a friend and former employee of my friend Dean, who wrote software to run the FI).

In contrast - post-WW II carburetors typically run 4-7 PSI. Throttle body FI is about 10-15 PSI, and port FI is about 40-50 PSI.

 

[stoveboltgeek]

There are other ways as I mentioned above to do this in post #28. One is to add a port injector to each port. Ford has done this to the ecoboost. The port injector will clean the valve it doesn't run all the time. GM usually says to run a cleaner though the intake to clean the valves. BMW and VW will remove the intake and walnut shell the intake ports and valves. There is advantages to DI. But in max HP effort the port injection works better. There are LT guys plugging the DI and running port injection on max effort engines. Some have even used LT heads on LS motors as they flow really well with DI ports blocked. As I stated before The limitation of DI is fuel flow. They don't design the system with extra capacity to increase fuel to DI injectors. So that is the limit on LT motors.

There are two system port injection and Throttle body EFI. Port injection is better in the fact the fuel isn't in the intake till at the valve. On Holley Sniper its like a carb were fuel is in the intake to mix as it goes and has issue same with a carb of fuel separation. Yes there are gains in intake flow but also need correct intake as stovebolt mentioned to get the fuel to the valve still in the air correctly.







The PCV system is the issue its letting oil into intake and gumming up the valves. GM spent Millons on RD just for the PCV system for the LT motors and they still have issues. I tell every one if you buy a new LT based car or truck install a catch can ASAP.



I wonder if they flowed the intake on a bench or just made one and ran on dyno. Either way they would have to cast alot on units to weed out the ones that worked. Now its all done on computer modeled. Then 3D printed flow tested in plastic then casted and tested.





The IH runners are small and make alot of turns the heads are horrible as well. I seen guys port the heads and make sheet metal intakes and still only get 300-350 hp out of them but that spinning them to 5k. Some have even added port injection to the stock intakes. My 392 stock with 4bbl intake a GM TBI system made 180hp and 400ft/lb or torque at 2500 rpms's at the wheels.

Main issue with the IH motors is vapor lock they are BAD about it.

A crude analogy: They recently ran the Kentucky Derby. They're also talking about announcing the NFL football schedule for this fall. Now, a jockey would make a pretty bad football player, and vice-versa.

Given what you've told us, IH designed their gasoline engines to operate almost like diesel engines. Low end torque out the wazoo, very low redline, small runners, long stroke for extra torque, etc. - it all adds up. They're truck engines designed for hard use in commercial applications, so limiting the RPM by choking off maximum airflow helps keep careless drivers from overrevving the engines while hurrying to get through the day's work. It's almost like the engine has a governor built into its design (in addition to any governor that might be built into the carburetor).

OTOH, the 302 used in early Z-28 Camaros was designed to wind up to high RPMs.

Different applications, different customer expectations, different design strategies.

 

[wayne82748]

This has gone beyond interesting to fascinating. First, Stovebolt is correct. I should have broken my post into paragraphs, following the rule "change in topic requires a new paragraph". I retired from teaching 20 years ago and I am "slipping" but I will correct that. No offense taken. I read and reread every post. I have learned more than I thought possible in such a brief discussion.
First, I missed on the source of dirty intake valves. I understand now it is a PCV related problem, and have learned that other companies, besides Toyota, have added some port injection to clean the valves.
The information that applies to my situation comes from Stovebolt in regard to the lack of a bowl vent on the 4GC and the possibility of the fuel line routing being a problem. His comment in regard to insulating the fuel line is an issue I have never considered but it makes sense. Remember the days of carbureted drag racers using a "cool can" or packing the intake with ice between runs? If have to dig very deeply into the slotted gasket scenario also, as a possible cure for the lack of a vent on the 4GC.
But, most helpful is the discussion of idle mixture. That is something I have to "trial and error" my way through after a rebuild on the 4 Jet. Of course, throttle response is affected by the idle mixture. "Loading up" at idle, or coming off a lean condition will give me the "stumble" condition. (We gearheads in the North always called it a "bog", but I understand).
To say that I have tapped into a "wealth of knowledge" is a huge understatement. I'm anxious to learn more. Lastly, I recently received a copy of Dean Tryon's book "Fundamental Carburetion" that Stovebolt mentioned. This is the first in depth information I've gotten on carburetors that is written in laymen's terms. It's nearly impossible to simplify the concepts concerning caburetion, but Dean has done that. This publication has it all: Easy on the eyes font size, excellent graphics, and Dean is excellent at converting complicated data to digestible material. He would have made a great teacher if he had chosen a different career path. Thanks to all of you for your contributions.