Universal 5432 air intake upgrade

Hello All,
A while back someone here was asking questions about air filters on Universal engines. At the time I figured that whatever Universal thought appropriate to install on my 5432 was fine. Upon inspection, I have reconsidered that position. The factory air intake "horn" is a funny looking teardrop shaped chunk of metal that I never really looked at.

The intake is quite small @ only 1" X 1 1/2" and it has a coarse metal screen riveted over the opening. Mine was about half plugged with muck. The intake manifold itself it just shy of 2" round so even thats larger than the opening in the horn. Since it was pointing down I never looked at it.... While I realize that these engines are not large displacement they do need as much air as possible to do their job well. A diesel will smoke as well as run high coolant and exhaust temps if the intake is overly restrictive, especially at high power levels.

So I went looking and I think I found a nice upgrade. http://www.knfilters.com/search/product.aspx?Prod=RA-0470 I purchased one of these ra-0470 filters and installed it. It has a nice port on the backside for the breather tube to insert into and the base is offset to clear the rest of the engine/accessories. I tried sucking through the factory air horn, for testing purposes only, and could easily feel the restriction in my breathing. Breathing through the K&N was as if it wasn't there. So whats this mean? I have a hunch that the engine was starved for air at higher rpm. The K&N should fix this issue and maybe help out on the hot running problem I had last season. I have test run only at the dock so far and the results seem favorable so far. I will try to get a pic of the setup up this weekend.

RT

So this filter fits in place of the horn? Sounds good. I took my horn apart and cleaned it adding a foam sponge like element from Torreson marine that was listed as a filter for the 5432. Please keep us posted on this project as I have similar issues with my 5432.

http://shop.torresen.com/ships_store/index.php?p=details&mfc=Universal&sku=301049

Ted,
How did you take the horn apart? My horn is a one-piece deal with the coarse screen riveted on the intake end. Where does that foam filter go on yours? Yes, the K&N just clamps on to the intake manifold inlet in place of the horn. Very simple. RT

Finally got pics, crappy ones, of the K&N setup I have installed on my E38. FWIW, RT

Rob,

Looks like a very reasonable installation. Any report on whether you're running any cooler with less restricted airflow?

Rob,
Is there a 'thinner' filter than the one that you have - more like the stock filter? I think that the one in the photo wouldn't fit on my 38-200 since my engine box cover sort of slopes aft and would foul on that thicker filter. Your engine cover looks fairly vertical. Nice install though!

Craig,
The engine runs MUCH cooler than last season. Even motoring for 3.5hrs at 2400-2500rpm into steep chop and a 25kt headwind it never got above 165*F....
BUT....
I also replaced the heat exchanger, thermostat, new impeller last winter and also did the "bypass" mod to the water heater last season. So I certainly can't credit the air filter directly for the difference. I will say the engine seems much happier and there is no smoke visible even when pushing her hard. Seems much more willing to rev up and sounds better. Subjective for sure but I like the perceived difference.

John,
Regarding the size of the filter, K&N make many, many sizes and styles. www.knfilters.com has all the product online. Mine is a "universal" size. They have all the dimensions there so you can choose what will fit best. Is it possible to install a 90* elbow and then the filter to turn it to where you have more clearance? I would be happy to raft up with you sometime and you can try my filter for fit if you like..... btw, got the stickers, thanks!
RT

Rob,
Did you happen to ask K&N about the higher-airflow requirements of a diesel? Their web site talks about only "fuel," as far as I can tell.
Obviously it works for you and should be fine for any of the rest of us, but knowing that a diesel gulps a lot more air than a gas engine got me to thinking (always a dangerous thing!).

Thanks again for the narrative and the photos are a great help also.

Loren
(M25XP, 3 cylinder 23 hp)

Hi Loren,

If you do a vehicle search on the K&N website, you'll find listings for diesel models. In addition, given their great improvements in flow over traditional elements, you can pretty much count on a K&N beating most anyone's stock air filter. Diesel air needs should be OK.
Deposit .02 now, please

The statement that diesels "gulp huge amounts of air" is misleading. A diesel "inhales" the same amount of air at idle as it does wide open, in theory. Actually a naturally aspirated diesel takes in less air as rpm increases due to restriction increases as intake air velocity increases. The result is diesels take in as much air at idle as a gasser uses at full throttle.

The K&N filter in my application will definitely flow more air than the stock air horn thingy. Just looking at it will tell anyone that. I don't always recommend K&N's as they don't filter as well as a paper filter, allow more dust, etc. On a boat, this is a non-issue, especially in my case since there is no factory filter on my engine. Regarding sizing the filter simply figuring an equal surface area or more in the K&N should suffice.

RT

I think the idea of the diesel using more air is related to the old Detroit 2 stroke diesel. It needed a blower on the side just to run. And yes, they gobbled a lot of air. The four stroke diesel is quite similar to a four stroke gas, and the air consumption is more a product of bore and stroke and rpm. Have you noticed any noise reduction with the K&N ?
Harold

Actually the blower on the Detroit two cycles is to scavenge the cylinders. Since there is no dedicated exhaust stroke to clear the cylinder of exhaust gases the blower does it. When the piston is close to BDC the blower is actually moving air into the cylinder and pushing the exhaust gases out. The "supercharging" effect is not the primary reason for the blower. Thats why the high output Detroits commonly have one or two turbochargers feeding into a large liquid-to-air intercooler and then into the blower. I've been in an engine room with two 8V71's setup like this and running at full power. Kinda makes you want to thump your chest and grunt like Tim the Toolman Taylor.....

Four stroke diesels are very similar to four stroke gasoline engines with one glaring omission. Gasoline engines have throttle assemblies and engine speed is governed by restriction of air via the throttle. Four stroke diesels lack a throttle assembly* Diesel engines are controlled with fuel. More fuel, more power, more rpm. Gasoline engines are controlled with air. More air, more fuel, more power, more rpm. This is an important distinction. Gasoline engines operate with vacuum present in the intake system in all but wide open throttle situations. This accounts for why gassers use far less air at idle than a diesel. In the old days of carburetors the air rushing through the venturi creates the vacuum and is what caused the fuel to flow into the airstream and be vaporised. In a diesel none of this occurs. The injection pump controls the fuel injected directly into the combustion chambers. There is always plenty of air for the fuel to burn-unless there is a restriction in the air intake system.

A diesel fuel system, the injection pump specifically, is calibrated to inject "X" amount of fuel for a given RPM and load for each point in the rpm scale. This is based on the air intake capacity of the engine. Restrictions in the intake system due to clogged air filters, etc. will result in less than the required air being in the combustion chamber when the fuel is injected. Diesel combustion chamber temperature increases as fueling increases. (This is the OPPOSITE to gasoline engines combustion chamber temperatures which generally run cooler if overfueled) It is fairly easy to push a diesel into "overfueling" with a restricted intake system when under load. Not many people realize that overfueling brought on by any number of reasons can produce combustion chamber temperatures high enough to melt pistons. This is one of the reasons why most modern diesels have a little intake restriction meter in the airbox to alert the operator that the air filter needs servicing. Overfueling is usually accompanied by excessive black smoke from the exhaust.

* Some diesels do in fact have a throttle assembly but it is usually emissions related....

RT

Good discussion - that explanation of the difference between gas and diesel speed control was nice and compact. One thing that seems obvious is that the diesel and the gas engine have to maintain the proper fuel/air mixture to keep running. So for both types of engines, the required air volume per SECOND increases with RPM increases. On a given engine, the air volume per intake STROKE (cycle?) remains approximately the same as RPM increases (displacement governs this).

Finally, to my point. If there's no exhaust smoke on the diesel throughout the RPM range, then the air-fuel is probably adjusted properly for whatever airflow is getting to the engine, would that be correct? If that is correct, then an increase in airflow caused by removing a restriction may be significant enough to require an adjustment to the fuel injection system? There's probably a tolerance band for every engine with respect to that.

How can you tell if too much air is getting to a diesel?

Air Volume thoughts

footrope said:

Finally, to my point. If there's no exhaust smoke on the diesel throughout the RPM range, then the air-fuel is probably adjusted properly for whatever airflow is getting to the engine, would that be correct? If that is correct, then an increase in airflow caused by removing a restriction may be significant enough to require an adjustment to the fuel injection system? There's probably a tolerance band for every engine with respect to that.

How can you tell if too much air is getting to a diesel?

Click to expand...

My SWAG on this is that, for a naturally-asperated engine, the cross sectional area of the intake pipe will always limit the maximum flow of air that enters the manifold. You could restrict this air with a clogged or inappropriate filter, but not increase it beyond the cross sectional area available. So, "too much" should not be a concern...

Add a compressor, and all this changes. :nerd:

I am no way a mechanic, but I operate a naturally asperated 23 hp Universal on the boat, and a turbo-charged 150 hp John Deere on the club dredge -- and do some routine maint. on both.

Loren

Think of your engine as a pump. In simple terms (not thinking of ram effect, scavenge etc.) the ultimate air flow (on a naturally aspirated engine) is limited by the pumping (suction) of the piston going down on the induction stroke. Too much air really shouldn't be a problem as long as the fuel system is supplying what it should.

My old M-25

My old M-25 has been running a K&N now for 6 seasons with NO problems. The current owner loves the upgrade!

Loren Beach said:

My SWAG on this is that, for a naturally-asperated engine, the cross sectional area of the intake pipe will always limit the maximum flow of air that enters the manifold. You could restrict this air with a clogged or inappropriate filter, but not increase it beyond the cross sectional area available. So, "too much" should not be a concern...

Click to expand...

Emerald said:

Think of your engine as a pump. In simple terms (not thinking of ram effect, scavenge etc.) the ultimate air flow (on a naturally aspirated engine) is limited by the pumping (suction) of the piston going down on the induction stroke. Too much air really shouldn't be a problem as long as the fuel system is supplying what it should.

Click to expand...

That all makes sense to me. I'll forego Rob's mouth suction test and add this to the mod list. The horn with the screen and no filter (my configuration) is less than half of the cross-sectional area of the 2" tube. I'm curious about the increased airflow effect on the crankcase vent, but I'm not concerned enough to mention it.

There is no such thing as too much air for a diesel. There is also no such thing as a "correct" air-to-fuel ratio with a diesel either. This is gasser thinking. Gasoline engines operate at 14.7-to-1 "stoichiometric" IIRC ratio when running correctly, at all throttle settings, idle to WOT*. Diesels operate at widely varying air to fuel ratios, 100 to 125-to-1 at idle and 20 to 25-to-1 at full power. The thing to remember is the FUEL controls the engine speed/power, not the air! Say you have a diesel engine that is turbocharged and running excessive EGT's (exhaust gas temperatures) under full load. There are two solutions. Back off the power. Less fuel=less heat. Downshift, change props, etc. and the EGT's will drop as the load is reduced. The other option is add an intercooler. The intercooler reduces intake charge temperatures by HUNDREDS of degrees. Compressor outlet temps can exceed 400*F at full load. A well designed air-to-air intercooler can reduce temps to 30-40*f above ambient temps. Air-to-liquid intercoolers can reduce it much lower still. Cooler intake air means cooler exhaust temps without reducing load or fueling. Alternatively a smaller engine can safely burn more fuel and produce more power with intercooling. If we are talking about reducing the EGT's in a NA (naturally aspirated) diesel then there are fewer options. Reduce power/load and make very sure the engine is getting as much air as possible and the air is as cool as possible. Yes, I am a diesel-head. RT

*Gasoline engines actually make peak power at about 12-to-1 AF ratio but that is all-out maximum effort racing applications. Your vehicle cruising down the interstate is at 14.7-to-1 or maybe just a bit leaner.

Sometimes a thread has good information that newer site members might miss, so it seems worthy of a "bump". Like this thread.
The combustion and relationship of fuel to air is helpful to read over. ( Despite good intentions, I never did convert my old Universal to a K&N, and the new Betamarine has a factory 'paper' enclosed filter element. )

Update: I replaced my 40 year old Universal 5432 original old oil clogged air filter with the K&N RA-0470 today and it’s a perfect fit. Comes with backside knockout and fitting for the crankcase valve cover breather thingy hose. I’m happy with the new filter and the old girl breaths easy now. See pics.