Diesel Noise

[joecool911]

Where does the diesel noise come from? I was thinking lifters, but when coasting there is no noise. I started adding 2 cycle oil and no reduction noted. Could it be the injectors? Pretty noisy clicking when going uphill at low speeds especially in the morning before operating temps reached. 161,800 and don't know if the valves have ever been adjusted? Only owned it for 20k miles.

[Rogan]

Not 100% of what you're talking about..In a general sense, "diesel noise" comes from the inherent design of "detonation". When you're coasting, fuel is (in essence) shut off, so there's no detonation or combustion.It will be more noisy in cooler operation temperatures (like before it's completely warmed up) due to the inefficiency of combustion until the engine gets warmed up.I'd still suggest a valve adjustment, if nothing more than for preventative maintenance/servicing.

[joecool911]

Valve adjustment is high on my list of projects. Figured I'd do the breather mod at the same time.

[drscott]

I had only had a diesel for a month now and I was going to post a very similar question. To me there are two noises that are different from gas engines. There is the "clatter" which I think is the detonation and there is the "whistle" that I am guessing is the turbo. Whatever it is I like it - sometimes I turn the radio down when I am on the highway just to listen to the engine.

[joecool911]

What makes the newer diesels quieter?

[ISX]

What makes the newer diesels quieter?

The pre-injection! The entire knock of a diesel is derived from the sudden explosion of the fuel being injected. If you can spray in just a little bit, you can get the fire going with very little noise, once it is going you can throw in the main injection and since the fire is already going it transitions very smoothly with no noise. IFFF they did not have a preinjection, they would knock louder than a VP44 truck because the pressure is instant. Mechanical pumps have a "wave" where the pressure starts, peaks, and falls back down. Because of this, it starts off with low volume which produces less knock, then peaks and falls back down. VP44 trucks have higher pressures so they knock more than 12V's. People will debate that but I have thought bolts were falling off my truck when the 24V next to me was running without me knowing. Because common rails ALWAYS have peak pressure (though it is variable), the injection is instantly at that pressure, no ramping up or anything, so that instant injection of fuel would be a very loud knock so they added the preinjection to fix it.

The more instantaneously the fuel can be injected and ignited/burned, the more efficient that particular process is. If you have fuel ramping up to peak and ramping back down then part of the fuel is in a crappy region, hopefully the peak injection is in the best timing region and then it ramps back down. That is why common rails inject it instantly and can go up to very high pressures, it is more efficient. We know that 15* ATDC is the best point so if you can get all the power out of the fuel at that point, the better it will be.

In this pic you see the pressures and how the CR is very steep and the ppump/vp is gradual. The baseline is injector opening pressure so it's right on the edge of opening at the baseline. Ignore the red lines, that is unit injector and post injection crap (emissions).

1. Pre injection

3. CR Main Injection Start

7. CR Main Injection End

5. Regular injection pump (P7100, VP44) Injection start

6. Regular injection pump injection end.

[JOHNFAK]

Isx said what I was going to say - hahahahahahshshahahThat stuff

[Mopar1973Man]

ISX got the mechanical part of it nailed. But now why does the 2 cycle oil effect it? Simple because the more you reduce cetane the slower the fuel ignites and burns so instead of a violent knock (explosion) you get more of a strong push. Also remember the more your reduce the cetane towards 40 the more BTU's are in the fuel.

From the ATSM testing labs...

[ABennin]

Not trying to derail but I got a question. Since the cam install I have been told on more than one occasion that my truck sounds like a 12 valve. There is a noticable difference at idle especially. Not so rattlely and more mellow I guess you could say. So I am thinking the cam must be part of mix. Please do tell I would like to know more on why, this has been very interesting to read. Edit: I have a Colt Stage 2.

[ISX]

Not trying to derail but I got a question. Since the cam install I have been told on more than one occasion that my truck sounds like a 12 valve. There is a noticable difference at idle especially. Not so rattlely and more mellow I guess you could say. So I am thinking the cam must be part of mix. Please do tell I would like to know more on why, this has been very interesting to read. Edit: I have a Colt Stage 2.

I knew AH64ID had some info on this and I dug up this thread. Says it is smoother at low boost because of more air, and that was with just a stage 1 colt. I am not sure if the power is smoother or if the noise is smoother though, maybe he will see this and confirm. At idle I would expect the engine to be going so slow that there wouldn't really be any air flow issues and the engine already runs very lean. Your experiences seem to say otherwise and I'd like to dig up some more info. Do you have the lift specs on it?

[ABennin]

I have a Carter pump located as close to the fuel tank as I can get. That was the first thing I put on the truck after buying it 7 years ago. Looking into a fass due to the age of the pump in the future. When warm I see 15 idle and 13 cruising, cold substract 1 each. I know I am on low part of the pressure for the VP but the darn thing is still working.What AH64ID said about his cam I can say about mine except the noise. The truck pulls harder in the lower rpms and noticed a bump in fuel economy.

[adamey1000]

ISX got the mechanical part of it nailed. But now why does the 2 cycle oil effect it? Simple because the more you reduce cetane the slower the fuel ignites and burns so instead of a violent knock (explosion) you get more of a strong push. Also remember the more your reduce the cetane towards 40 the more BTU's are in the fuel. From the ATSM testing labs...

So if I understand that cetane is bad then why are cetane boosters sold as fuel additives?

[diesel4life]

Cetane is essential for proper detonation, too low and you will have hard starts and smoking when the engine is under load. So they add cetane to prevent this along with sludging of fuel. But like Mike stated too much is not necessarily a good thing either. Most of the time time cetane additives arent necessary unless fuel has been sitting for a while or perhaps in extreme cold weather

[dorkweed]

High revving diesels.........like in Europe require a higher cetane rating.........so all the fuel is ignited and burned before the exhaust stroke.In the winter/cold weather, higher cetane is beneficial for starting and extended idling(not recommended)!!!:smart:Our Cummins recommend a cetane rating of 40-45 IIRC. In Europe, the diesel sold there is usually 50+ in rating.Cetane is inversely proportional to Octane. Cetane rating is a system developed to chart the fuels ability to self ignite...........Octane rating is a system developed to chart the fuels ability to RESIST self ignition.

[Mopar1973Man]

Dorkweed and diesel4life are right. Colder the weather the higher the cetane is required. Then higher revving the engine the higher the cetane is required. But that's why racing diesel use 55 cetane is to get a complete burn but then overfuel the engine to gain back the lost BTU's in the high cetane this why all racing diesel smoke like freight train. But like my self I drive at 1,200 to 1,800 RPM's normally so I don't need high cetane fuel but lower cetane. Every winter Idaho diesel fuel is 50-55 cetane on average but MPG are reduced. But come summer time when cetane is reduced to 40-45 then the MPG jump back up again. Then for fun I was at a dyno event and watch then dyno a 12V Cummins truck on normal sumer fuel, then dyno on cetane booster, then on 2 cycle oil. This truck was nothing more that a street machine nothing fancy. With the cetane he lost HP by about 20 HP and with 2 cycle oil at 128:1 he was about 5 HP over the normal summer fuel. Depends on your application of what your going to use you truck for on what type of fuel to use.

[adamey1000]

Thanks guys for all of the great information! So two cycle oil is the additive that you would recommend? I read an article somewhere that highly recommended power service diesel clean. That is what I have been running but I really don't notice any difference in mpg or power

[Mopar1973Man]

Thanks guys for all of the great information! So two cycle oil is the additive that you would recommend? I read an article somewhere that highly recommended power service diesel clean. That is what I have been running but I really don't notice any difference in mpg or power

I got something you can try. Pull all your injectors out and put then in a bowl. Then fill the bowl with injectors submerged in Power Service or any fuel additive you wish. Then wait 24 hours worth of soaking. 99.9% of the time nothing happens the injectors are still filthy and have coked up fuel internally and carbon coated nozzles. The only way to clean a injector is to disassemble and physically clean by hand.

So if soaking 100% injector cleaner does nothing then happens when you mix it at 400:1 ratio as suggested by PowerService? Which is 4,480 ounces (35 gallons) at 400:1 ratio is 11.2 ounces in 4,4480 ounces of fuel. I hardly doubt that mixture is going to do anything thing if a 100% didn't do anything...

[ISX]

I did put an injector in injector cleaner for 24 hours and pulled it out and scrubbed it and nothing changed. I talked to a chemist and he said that stuff has to move to slowly clean the injectors. Kinda like we can throw a brillo pad on top of the injector and wait 24 hours and it will still be sitting on top of a dirty injector.. So I don't know how true this is and obviously some long term use of injector cleaner would have to be administered to see if it works. I also don't know if we are actually seeing the true results. Injector cleaners aren't going to wrap around and hit the nozzle tip, they are only going to clean the internals. I always have some very light fuel coking on the needle seat face but I don't run injector cleaner so until I do, I can't say anything. When I take the injectors out, they always work fine. I have one that leaks but I cleaned it and took it apart a million times and nothing changed. One guy on here said he did the same thing with the same results and chopped it up to the injector physically being "worn out". Makes sense to me. Question is; is running injector cleaner to keep the injectors clean worth the added wear from the actual cleaner? Mike has shown countless times that all of this cleaner is just paint thinner. On VP44 trucks, that means the same paint thinner is also going through the precious VP44 which is lubed by fuel, but the injectors are also lubed by fuel. To me, the cost of taking them apart and cleaning them is nothing but your time. The cost of poor lubricity can be much higher. Injectors don't just clog up, they clog up only if your fuel filter isn't doing it's job. That being said, the injectors seem to have a certain amount of coking they accumulate, but this accumulation isn't much if everything is set right. Running WMO and other crap like that is not what these things are designed for because it is too thick and the cetane is too low and it doesn't burn as good or as clean. HUGE marine engines are designed for that crap, but not ours. So if everything is set right, we only get so much crap on the injectors. I clean mine every 5-10k because I find it addicting but they always look just like they did when I pulled them after 300k.. The coking on the injector nozzle might be thicker (barely), but for the most part it barely gets any accumulation on an engine with everything set up right. Over time, there are some places where very fine particles may wander into, but this takes a very very long time (probably 100k miles for it to accumulate enough to even see) to get into and the places it wanders really don't matter. Coking on the needle seat face is something as it is very precise though comparing my 300k to my 5k changes, it seems to accumulate instantly and then just kinda stops. But it probably accumulates more on a microscopic scale that might make a difference in injector function so all in all injectors should probably be cleaned every 100k miles to keep them perfect. One time I cleaned the injectors, threw them in, ran the engine for a while, and took them back out. All I did was idle. The injectors had surface carbon on it that wiped right off. But it just shows how instantly it gets on there, but it doesn't really accumulate. It might coke on there over time, but it doesn't seem to ever get thick. The injector holes are the only real concern as if they get coke over them even a little, then the spray patter will be off. On WMO injectors, the coking layers up and probably has this effect. At 300k miles before I had ever pulled them, I was still getting the same mileage I do today and it ran perfect.. Further proving that an engine set up properly will not have any issues. I know Mike has had some rough idle issues and has to clean them to fix it but for the most part, they are self maintaining, though its so fun to clean them so why not.In the end my personal advice is to clean them every 100k to keep everything (no matter how minimum) happy and use lube rather than injector cleaner.

[adamey1000]

So the power service is a cleaner? I was under the impression that it is just a general lube additive and cetane booster... I am new to diesels though and don't want to jeopardize that new vp-44! I know that I would never run carb cleaner in every tank of gasoline though so that makes sense.

[Mopar1973Man]

So the power service is a cleaner?

Yes.

I was under the impression that it is just a general lube additive and cetane booster...

Cetane booster yes. Lubricant, No. PowerService Failed the HFRR testing. Bosch requires HFRR 450 score or less.