Intake Manifolds and mpg

[MChrist]

Regarding the intake horn... have you seen some of the magazine articles that have these high hp 5. 9 cummins that are used for sled pulls and a few of them still use the original intake horn?
I have the CFM + intake horn because it rated highest in hp on a recent dyno article, and because it had the threaded ports on the side. I can't honestly say I noticed any difference in power or mpg. Too many variables. I think if somebody swapped the aftermarket horn for the stock one and didn't tell me, I wouldn't notice the difference. That's my "rule of thumb".

 

[EDankievitch]

Diesel power had done a very goodtest on intakes they proved that there is not much if any added bennifit at stock levels. They showed that the increased flow only started to show at higher RPMs and Hp levels. They had used a dyno and also some programing through out the test, but if you read the charts closely it's all there. My own testing has proven much the same the engine does seem to be "Not held back at RPMs after 2900, the tourq seems to stay there longer. " At normal driving RPMs there is no change from stock. Tdr did a write p on intake air boxes (cool air kits) a while back and they also proved that the stock air box was a very good match for a stock Hp engine. They had used flow rate meeter to show what the box could do and temp sensors to check the actual air temp. They proved that some of the aftermarket boxes actually let in more hot air than the stock box did. I'm not knocking the aftermarket or it's products I run a Banks dual exaust and a Banks intake o my 05, but on my almost stock (ok ya caught me I've got Dynomite diesel's stage 1 injectors) the Banks just looks good did nothing for my MPG or preformance. Cummins did a awesome job making the engine and the Hp/ tourq it makes it's going to take alot more than just some smooth pipe to improve on that. At stock levels.

 

[ENafziger]

From wikipedia:

Engines using the Diesel cycle are usually more efficient, although the Diesel cycle itself is less efficient at equal compression ratios. Since diesel engines use much higher compression ratios (the heat of compression is used to ignite the slow-burning diesel fuel), that higher ratio more than compensates for the lower intrinsic cycle efficiency, and allows the diesel engine to be more efficient. The most efficient type, direct injection Diesels, are able to reach an efficiency of about 40% in the engine speed range of idle to about 1,800 rpm. Beyond this speed, efficiency begins to decline due to air pumping losses within the engine.

 

[JLEONARD]

The engine has no need to ingest more air, only to use greater boost to make the air more dense

There's some double talk.



You can buffalo the 3rd gen guys but not the 1st gen crowd.

 

[HBarlow]

The engine has no need to ingest more air, only to use greater boost to make the air more dense

There's some double talk.

You can buffalo the 3rd gen guys but not the 1st gen crowd.

I'm sorry you don't understand it.

Some folks simply will not allow facts and new information to intrude on their deeply held beliefs, even when they can easily be proven wrong.

Each to his own.

 

[Flexiheep]

I'm sorry you don't understand it.



Some folks simply will not allow facts and new information to intrude on their deeply held beliefs, even when they can easily be proven wrong.



Each to his own.

Sorry, even if you understand what your saying, you are not comunicating in a way that anyone else can comprehend.



Chemical reactions are based on mass not volume, if you "increase the density" of the air in the cylinder you would have to decrease the volume of the air to have the same mass present. Since we are filling a known volume (the combustion chamber) if we increase the pressure we will increase the mass of air available.



If you want to please explain to me a similar situation:

How can I increase the pressure in my car tire (keeping the temperature the same) with an air pump but not add any air to the tire?



I believe the proper forum for uninformed posts is the Political forum, your "facts" and personal theory go against even the most basic scientific principals.

 

[HBarlow]

Some of you guys are comical but it is sad that you own and drive Cummins diesels and know nothing about how they work.

A Cummins diesel engine has all the air flow potential it needs from idle to redline rpm as it is built at Columbus, IN. In OEM stock condition it is fully capable of flowing all the air it needs until horsepower output reaches level of around 450 hp. Gimmicks such as aftermarket boost elbows, air boxes, filters, or none at all do not and will not make additional horsepower or torque. If you drive a highly modified engine with significantly greater fueling and boost that produces upwards of 450 hp modifications to air intake and exhaust output will begin to show improvements. Under 450 hp you are only spending your money and dreaming.

If you understand the most basic concept of a diesel engine you must surely know that it has no carburetor and no throttle blade that controls air intake. The intake is open from air filter to piston top.

So if additional air flow makes power how do you control air intake to increase rpm? You don't.

How do you increase power to increase engine speed from idle to redline? You add more fuel. Additional air flow occurs naturally as the engine rpm increases.

The poster above attempted to pretend that he knows something about science to insult me. TDR editor Joe Donnelly knows a little science. He holds a Ph. D. in chemistry. Have any of you ever read the articles including the detailed and objective test results he has reported in the TDR magazine on intake air components? If you believe I don't know what I'm talking about perhaps you can understand that Joe does?

A gasoline engine has a throttle blade. Power output and engine rpm in a gas engine is increased by opening the throttle increasing the flow of incoming air with the proper 14:1 air to fuel mixture. Because a gas engine is an air pump it can develop greater hp with more air, more fuel, and greater rpm. Not true with a diesel.

Others have tried to tell you guys the same thihgs.

 

[JLEONARD]

Some folks simply will not allow facts and new information to intrude on their deeply held beliefs, even when they can easily be proven wrong

One of my main reference books is "Diesel Engine Reference Book" last updated in 1986 so that is pretty "current" as it applies to a early mechanical Cummins. Actually it's appropriate up to the newer CR engines I suspect.



4. 3. 8 (for example) discusses air utilization and how important getting air into the engine is as an important design consideration. I am not going to type the text here.

There are also articles on the net that discuss this, you can find them easy enough if you look.

So if additional air flow makes power how do you control air intake to increase rpm? You don't.

You don't. You "control" air by adding fuel (or subtracting) that you can combust with the amount of fuel you can deliver. Once you reach the point where you can no longer burn the fuel you get black smoke. So the key is to get more air and it must flow to get where it needs to be (or extend the event by advancing timing but that's not the subject here). So you can try to get air to the cylinders thru a 1 inch pipe or a 3 inch pipe. Whatever the PSI is, it still has to pass thru a pipe.

I think that's the point here.

 

[HBarlow]

Some folks simply will not allow facts and new information to intrude on their deeply held beliefs, even when they can easily be proven wrong

One of my main reference books is "Diesel Engine Reference Book" last updated in 1986 so that is pretty "current" as it applies to a early mechanical Cummins. Actually it's appropriate up to the newer CR engines I suspect.

4. 3. 8 (for example) discusses air utilization and how important getting air into the engine is as an important design consideration. I am not going to type the text here.
There are also articles on the net that discuss this, you can find them easy enough if you look.

So if additional air flow makes power how do you control air intake to increase rpm? You don't.

You don't. You "control" air by adding fuel (or subtracting) that you can combust with the amount of fuel you can deliver. Once you reach the point where you can no longer burn the fuel you get black smoke. So the key is to get more air and it must flow to get where it needs to be (or extend the event by advancing timing but that's not the subject here). So you can try to get air to the cylinders thru a 1 inch pipe or a 3 inch pipe. Whatever the PSI is, it still has to pass thru a pipe.
I think that's the point here.

Now you are thinking!

Let's take your explanation of the paragraph above a step farther. "Once you reach the point where you can no longer burn the fuel you get black smoke. " That is very true. So how do you get more air?

Not by changing the boost elbow, air box, or air filter. You add more air with more boost. The turbo pumps in more air making the air moe dense before it is compressed by the piston upstroke or compression stroke. Modifying the intake system will do nothing to improve combustion, reduce black smoke, or improve power.

The engine naturally aspirates all the air it needs to make up to about 450 hp as is. The OEM Cummins intake tract is not restrictive and does not reduce air flow. Fuel and boost make power.

I'm not an engineer and don't claim to be an expert on diesel (or gasoline) internal combustion engines. I can't glibly roll complex technical explanations and discussions of engine technology off the tip of my tongue. I do understand the basics and I'm only trying to tell some that spending their hard earned money on fancy intake and exhaust parts for a stock or near stock engine won't do squat for them. Just because some aftermarket manufacturer/retailer provides inflated or false figures and claims their fancy parts will improve their performance, fuel economy, or sex life does not make it so.

 

[TWorline]

Exceptionally slow in the 3rd gen section I guess. :-laf

X2 :-laf:-laf

 

[cerberusiam]

Not by changing the boost elbow, air box, or air filter. You add more air with more boost. The turbo pumps in more air making the air moe dense before it is compressed by the piston upstroke or compression stroke. Modifying the intake system will do nothing to improve combustion, reduce black smoke, or improve power.

Now THAT statement is blatantly wrong from both an engineering aspect and a practical application.



NONE of these truck, let me say it again NONE of these trucks, has an optimized ait flow system. They are intenttionally restricted to meet emissions. All modern diesel engines run air lean and fuel rich. Since there is no throttle plate to control it restricting the air flow is the cheapest most effective way to meet the specs.



All the way from the air box, thru the CAC, to the intake elbow they are sized to cut down the air flow to keep the stoich where it is designed.



Boost is nothing but a factor of the restriction in flow. Reduce the restriction and at the SAME boost flow and density increase. Works the same in the filter area. If the turbo is drawing 4 inches of vacuum to make 20 lbs of boost reducing the suction vacuum will increase either the boost or the density of the air at the same boost level.



In other words, more power can be made at less boost when the air density is increased by removing restrictions to flow. hats not engineering, only simple high school physics.

The engine naturally aspirates all the air it needs to make up to about 450 hp as is. The OEM Cummins intake tract is not restrictive and does not reduce air flow. Fuel and boost make power.

None of these engines will make a clean 450 HP with arestricted air flow in the OE intake systems, 12V all the way to the CR's. Once you go above factory ratings a relatively small percentage it shows. The 1st gens are the most restrictive because they literally have the most to gain in the power arena. Its relatively easy to support double the factory rated HP but not with a factory filter. An addition of a better CAC and intake elbow also helps a lot.



That is easy to prove on a dyno once the restirction is contributing to power loss. Start replacing the pieces and the power starts coming up and the smoke reducing. The thing that keeps getting ignored in all these discussions is air density and oxygen content is the key, not boost pressure. Boost is just the cheap way to override the inefficiencies designed into the engine and air delivery systems to meet regs.



Reducing restriction in the air filter, CAC, and manifold will make more power to the point the fuel is completely burned, or stoich is reached. The problem is measuing the difference. The common modes of measurement are usually not sensitive enough to validate the concept so all we have is the math to prove it. The fact that 5000 BTU's is greater than 4000 BTU's is all we need to verify the concept is correct.



Comparing gas engines to diesels is just a fail because the AFR's are not the same to accomplish the same thing. Gasoline needs a stable AFR to function, diesels only need enough fuel to get the job done and that will vary from 15 to 1 all the way to 40 to 1 depending on load.





In essence a diesel engine is a big air pump with fuel added to keep the pumping going.

 

[HBarlow]

cerberusiam,

You are probably an excellent mechanic. I know from some of your posts on other subjects you know what you are talking about . . . but you do not know what you are talking about here.

The intake tract of a Cummins is not restrictive until performance upgrades ie boost and fueling push power up to or beyond 450 hp.

There is NO precise mixture of fuel and air in a diesel like in a gasoline engine. If there was you would not be able to increase engine speed from idle to redline by adding more fuel.

Sorry but you're blowing smoke here just like you were the time you were trying to tell me that a Cummins diesel produced peak torque at 2500 rpm or whatever you were claiming at the time.

Again, I offer as proof the testing reported in the TDR magazine. What do YOU offer as proof of the bs you wrote above?

 

[Paychk]

I sure miss the days when all the friction on this site was in the 2/3/4 gen and political forums.

I third the motion "slow in 3rd gen land"

Barlow maybe you would have more pull with this crowd if you drove a 1st gen.

BTW I don't see Joe down here trying to edjumakat the ignorant 1st Gener's either . :-laf

 

[HBarlow]

Paychk,

Do you think that a Cummins engine in a GenI truck operates any differently than any other turbocharged Cummins engine?

By the way. Why do you guys think Cummins installs turbochargers and intercoolers on their engines if all you have to do to improve performance is install a bhaf or a different air box?

Or, are you saying you guys in this forum prefer to remain ignorant?

I honestly don't give a hoot what you guys believe or how you spend your money. If memory serves correctly I saw a new thread under the "New Posts" heading a few days ago where a TDR member asked if changing the intake system would improve power output and fuel efficiency. Another member told him it would.

I know that to be untrue and inaccurate and hated to see the man who asked an honest question told to spend his money on something that would give him nothing in return besides shiny parts and bragging rights.

You are correct. Joe Donnelly doesn't waste his time here trying to teach some of you anything. He is probably too smart and too busy to waste his time on you. He probably knows that many of you never open the magazine and never read his educated and informed objective test reporting but prefer instead to read and believe the bs printed on shiny paper in one page paid advertisements by companies who sell the fancy junk.

Maybe I should just take a lesson from Joe and go away and forget about you. It doesn't cost me a cent when you guys spend your hard earned money buying junk.

I think some of you are like the guys who buy the products advertised on late night television that will regrow hair on the head of a bald man, make him vigorous, and make the sexy young girls love him.

 

[HBarlow]

I just ran across this post. Nick Isaacs did a great job of explaining exactly what I've been trying to tell some of you who are hung up on modifying air intake and exhaust. Yes, he is specifically talking about a 24 valve or HPCR engine but the basic principles of fueling and boost are identical.

TRat, to answer your question. On a computer controlled engine you need the EZ or a "boost fooler" to add more fuel, as in larger injectors. The EZ has a boost fooler built in, so if you un-hook it and add injectors, the extra fuel will just add heat with very little power increase. The extra fuel needs more air, as in more boost, that the EZ provides. Without the EZ, the computer will not allow the boost needed for the larger injectors.

The EZ works good on it's own, however it works great with a set of mild injectors. If you want to know about gauges, just ask

Nick

 

[MChrist]

I think the turmoil here is caused by a misunderstanding. Harvey, I agree with you that intake exhaust modifications to a stock motor are pretty pointless. However, you are in the minority when it comes to modifications on this forum. So, since most everybody here has modified the mighty Cummins to fuel more, then intake and exhaust seem more important and useful.
I still go back to the issue (wish I could find it) in one of the magazines that showed a high horsepower truck that pulls sleds competitively and still uses the stock intake horn. Since the horn is one of the least expensive and easiest modifications to make, surely he considered changing it.
My CFM+ intake horn is rated very high, if not the highest, yet I wouldn't notice if you swapped it for stock by my seat of the pants dyno.
I also believe that intake exhaust may make a SLIGHT difference, but not one that anybody is going to feel. So I would consider the difference, if any, so slight as to not be worth it.
Hope that's not too wishy-washy.

 

[ENafziger]

Well, I guess I disagree a little bit with everybody, but for good reason! :-laf

HBarlow, you are correct is asserting that changing an intake horn or exhaust on a stock 1st gen will not measureably effect mpg or power at stock power levels. Cummins engineers design things pretty well for stock, and somewhat beyond stock, power applications; this isn't to say that efficiencies can't be improved some, but the effect will be much less pronounced at stock fueling levels.

Flow improvements have been made with the later 3rd and 4th gen trucks as compared to 1st gen... and that only makes sense, as hp ratings have dramatically increased!

Cerberusium, you are mostly correct in what you say. However, a diesel does not run at stoichiometric A/F ratio much of the time. This is one of the reasons that fuel economy is better with compression ignition engine as opposed to spark ignition. An A/F of ~14. 7:1 is only reached when approaching full throttle on a modern diesel. Most of the time they are running MUCH leaner, up to 150:1 at idle, and typically in the range of 18:1 to 30:1 throughout much of a drive cycle.

HBarlow, you are correct in saying that increasing boost will increase airflow; this is correct only if the restriction in the air system is constant.

The way to make efficient power is NOT simply to increase boost and add more fuel. Boost is not the tell-all indication of the end result... it is simply one of the means to the end.

Increasing the mass flow of air through the engine is what is needed at higher power levels... and the more efficiently this is done, the better fuel economy, spool up, etc will be. I think you already know this if you think about it. In a 3rd gen reference, the HE351CW is not very efficient above 45 - 50 psi boost; in fact, pushing it much over 40 psi produces diminishing returns, as the air becomes very hot as it is being compressed out of its efficiency range. The hot air is much less dense, and as a result, the engine is not getting more air by pushing boost further.

The reason for going with a larger turbo (or twins) is to provide the engine with a higher mass flow of air... meaning cooler, denser, boosted air. With my '06 and the stock turbo, I foolishly hit 55 psi boost several times. I was very overfueled, and probably making ~475 hp. I now have a Helix 2 cam, AFE Bladerunner, 5" straight exhaust, 62/476 twins, aftermarket exhaust manifold, etc, all aimed at increasing the efficiency of airflow through the engine. Now at the same 55 psi, I have MUCH more air flowing into the engine, and can make a clean, not overfueled, 650 hp.

In summary, it's mass air flow that should be the concern. Boost is only ONE indicator of this, and may or may not be an accurate one. The stock components do fine at stockish power levels, and changing intakes, exhaust, etc at stock power levels isn't the best use of money if the goal is efficiency and power. More horsepower requires more mass flow of air to the engine, and that is accomplished in varying extremes as required.

--Eric

 

[cerberusiam]

The intake tract of a Cummins is not restrictive until performance upgrades ie boost and fueling push power up to or beyond 450 hp.

The 3rd gen system is much better at flowing air than the earlier ones, but, thats wrong that you cannot gain until you hit 450 hp. Gains will be seen with stock fueling by enhancing air flow to the filter box, removing the restrictions in the TQ tube, and changing intake. It shows on a dyno of 10-20 HP differences in the top number and a broadening of the TQ curve.



I did it in semi-controlled tests, others have done the same thing and we all posted the results.



Then again, if you don't believe the dyno sheets we post SHOWING the gains and where TQ peak really is, well, there ya go.



As for the 1st gens, stock air filter is very restrictive, stock muffler is necked down and the tail pipe crimped going over the rear axle. If you cannot understand how removing these restrictions would improve performance then its hopeless explaining the concept.

I agree with you that intake exhaust modifications to a stock motor are pretty pointless.

The point is they are NOT pointless. As you said gaining efficiencies is what will happen, but, if you gain efficiencies you gain power. The math tells us that even if we can't measure it.



A diesel is purely load sensitive and will only add enough fuel to get the job done. If you add less fuel to do the same job it took more fuel to do before the net effect is a power gain. You MUST take out the variables of load and run the calcs at a constant to make sense.



Again, the fact we can't adequately measure it cause the problem. Doesn't mean its not there just we cannot perceive it with our limited faculties.

 

[MChrist]

Hence "PRETTY MUCH pointless"...
The thing that most people don't take into consideration is that when you look at these dyno sheets, they are saying "5 or 10 hp increase". But that's usually at redline and full throttle. Those differences typically only shift the hp from down low to up high in the rpm range. You never hear that a product also usually LOSES "5 to 10 hp" down low, where you spend 99. 9% of your time. Just look at any dyno and chances are that's exactly what's going on.
The only thing on my truck that made a difference that I can feel by itself was the Smarty. When the twins went on, my 0-60 times didn't change a bit! It was only after switching from Smarty Jr to Smarty Elder that I increased power. Apparently, there wasn't enough fuel to light the second turbo, even though I was reading more boost with the twins and still using Jr.
So, in the interest of being less wishy-washy, I will say that intakes/exhausts don't make enough of a difference that you will actually feel, much less find worth spending $$$ on.

Has anybody here switched to a bigger single turbo and ran on the dyno or the dragstrip while using stock fueling before and after? I would find that to be interesting.

 

[cerberusiam]

Hence "PRETTY MUCH pointless"...

Now your taking HB's route of "I can't see it, feel it, measure it therefore it doesn't exists". :-laf



NOT true in any of these trucks from 89 all the way to 2011. Thats like saying 3 degrees is average temperature is pointless. You can't feel the difference but the ramifications are very obvious.

The thing that most people don't take into consideration is that when you look at these dyno sheets, they are saying "5 or 10 hp increase". But that's usually at redline and full throttle.

Again no, top number may not ever show a gain due to the inability to replicate loads. However, its quite possible to see the HP and TQ curves change in relationship. Its not "sexy" to brag about 10 HP at 2100 rpms but it is at 3200 rpms.





All the things you say you can feel the difference are much less effective when you don't do the things that you can't feel.



Then again, anybody with the money and basic skills can add HP to a CR and think they got it figured out. When you have to work at it, like on a 1st gen, then you understand the truth. :-laf