Engine/Transmission (1994 - 1998) "lean Condition'

[hsmith]

I think this is the problem I am having. Being a gas mechanic, that is the best way to describe what is happening. With my recent install of new turbo, I now have a popping noise from the intake under heavy load and throttle. If I keep the boost below 30 psi, the problem isn't there. I can make it happen even empty in 5th over around 75 if I really push it.

I'm thinking with all the air I now have, I may need to adjust and get a little more fuel. I really think I have a lean fuel mix under extreme conditions.

When I did the 3k and lever adjustment earlier, I had to go back and move my #11 plate back to stock position to cut back on some of the power.

What do you diesel gurus think about pushing the plate . 030? That is where it was before I slid it back.

What will i get in egt's with the extra fuel? I'm thinking if I don't have the lean condition, the temp's may not be as much a problem.

I can control this with the right foot, but now cannot use full throttle, which is a real bummer.



OPEN FOR SOME EXPERIENCED INFO!!!!!!!!!!!!!!!!!!!!!

 

[blacksheepdiesel]

hsmith,



1. Compression ignition engines are completely different in theory and operation than spark ignition engines. A "gasser" has to have a specific fuel/air ratio to run properly. A diesel fuel/air ratio is variable over a wide range from about 75 - 1 to 20 - 1 (I THINK those are correct). The diesel can not run "lean" as a gasser does.



2. I do not know what your popping noise is.



3. It is possible that you can adjust the plate for more fuel and be able to burn it IF the new turbo is stuffing more air (boost) into the engine. Why did you move the plate back to stock? We all want more power, but sometimes have to adjust the plate to reduce egt's. With a new turbo (is it a replacement or an upgrade?) your egt's may be lower.



4. Which turbo do you now have?



5. Go into your profile and update your signature to include all current mods. This will help in trying to figure out what is going on.



Trent

 

[y-knot]

Air to fuel ratios of up to 200 to 1 are possible with many diesels, while ideling.

 

[hsmith]

Originally posted by redbadge

hsmith,



1. Compression ignition engines are completely different in theory and operation than spark ignition engines. A "gasser" has to have a specific fuel/air ratio to run properly. A diesel fuel/air ratio is variable over a wide range from about 75 - 1 to 20 - 1 (I THINK those are correct). The diesel can not run "lean" as a gasser does.



2. I do not know what your popping noise is.



3. It is possible that you can adjust the plate for more fuel and be able to burn it IF the new turbo is stuffing more air (boost) into the engine. Why did you move the plate back to stock? We all want more power, but sometimes have to adjust the plate to reduce egt's. With a new turbo (is it a replacement or an upgrade?) your egt's may be lower.



4. Which turbo do you now have?



5. Go into your profile and update your signature to include all current mods. This will help in trying to figure out what is going on.



Trent

Slid plate back to stock after 3k spring and gov lever adj because power was more than I needed, smoke was awesome, and egts easily got out of range.

New turbo is from piers. HX35. Changed my profile to include this, but not surprised if I may not have done it soon enough.

This problem was not there before the install. Hope it is a concidence, but when it happens, it will get your attention.

Will try to answer anymore questions to try to solve this situation.

Thanks, hsmith

 

[Rhondasway]

I really don't have a heck of a lot of knowledge, but I'd be thinking of checking your valves/ valve springs. If your springs compress too much, they can cause the valve to "flutter". That's why when most of us get into high horsepower, we get the stiffer valve springs.

Valve adjustments are also critical. I'd do a real careful adjustment to make sure you don't have something just a little off. They need to be done regularly too.

Just a thought... Good luck and please let us know if/what you find.

 

[bmoeller]

Have you checked the timing on the fuel injection pump? Since the engine is modified, call back to Peirs to see what he would recommend for a timing change, if needed.

 

[Rhondasway]

Originally posted by bmoeller

Have you checked the timing on the fuel injection pump? Since the engine is modified, call back to Peirs to see what he would recommend for a timing change, if needed.

Good point. The timing on the 12 valves can slip, and you could be actually lower than stock. That'll mess with ya for sure.

 

[britannic]

Timing, valve float and possibly some adjustment like the governor settings are all possibilities with this symptom.



Check this thread out: Popping noise

 

[tgbol]

Just out of curiosity have you changed you valve springs to the 60# ones. It is possible that at high boost the 30# springs are popping open allowing so compression to back back into the intake.

 

[DSiemens]

Valve float was what I was thinking too. Advancing the timing will help to lower EGT. If you slid the plate forward, EGTs will get worse. Call Piers he has forgotten more than most will know.

 

[mikel]

I don't know what kind of pressure it might take to make the valves float, but I have run 37-38 psi on occasion and have never heard anything like the "popping" that hsmith describes. I'm still running the stock valve springs on my truck.



Is it a rapid popping, kinda like a fart? Maybe a boost leak? I have heard several paoples trucks make odd popping or banging noises, but it's always been due to something like leting off the throttle real quick at high boost.



Good luck,

Mike

 

[bighammer]

I'd call Piers. I'm curious what his opinion would be. I don't get the valve float answer and maybe it IS timing. I think you CAN run too lean in a diesel. It's just not as common as the black slobery rich condition we see all too much.

 

[britannic]

You're right, you run too lean when the engine isn't getting enough fuel to idle any more - either because the shutoff engages on the pump, air/fuel starvation is in the system, or some other reason.



Diesel doesn't require an exact stoichometric air/fuel ratio to ignite and burn cleanly, because it's a compression heat ignition fuel. Properly timed injected fuel oil will ignite and burn using as much oxygen as it needs. On the other hand, when there isn't enough oxygen or the timings off, it won't oxidise completely and burns more slowly, resulting in black smoke - this is equivalent to being too rich in a gasser.

 

[JoshPeters]

Have you checked all your intercooler boots? I had a funny squeek under heavy foot on mine, my turbo to exhaust manifold was bad.





just a couple thoughts

Josh

 

[JGheen]

Originally posted by britannic

You're right, you run too lean when the engine isn't getting enough fuel to idle any more - either because the shutoff engages on the pump, air/fuel starvation is in the system, or some other reason.



Diesel doesn't require an exact stoichometric air/fuel ratio to ignite and burn cleanly, because it's a compression heat ignition fuel. Properly timed injected fuel oil will ignite and burn using as much oxygen as it needs. On the other hand, when there isn't enough oxygen or the timings off, it won't oxidise completely and burns more slowly, resulting in black smoke - this is equivalent to being too rich in a gasser.

When you say there isn't enough O2 or the timing is off and the fuel does not oxidize completely, burning more slowly, would this cause black smoke to be emitted throughout the entire rpm range, rather than just through the lower revs on quick accelerations?? I understand that the black smoke is just wasted fuel, but those who emit a lot of smoke, are their engines considered to be not oxidizing the fuel properly? I am sort of confused about when the engine is actually not oxidizing and burning all the fuel. Sorry if my question is not understandable.

 

[britannic]

Any time there's black smoke is a sign that it didn't burn properly. Another cause is deliberately injecting so much fuel that it's still burning on it's way out of the exhaust manifold and keeps the turbo spooled up. Injecting too late (retarded) can miss maximum compression heat and pressure, so the charge burns more slowly and therefore incompletely. Too early (advanced) can have a similar effect and cause black smoke.



Obviously "slow" is a relative term, since it all happens in fractions of a second.



The key is burn every drop of fuel and extract max power.

 

[hsmith]

Thanks to all for your input. That is one reason I use this site. Members are all so helpful with each others problems. Will be talking to piers soon I hope. Will also update my sig to include all mods.

 

[HEMI®Dart]

Here are some more threads with good info. You are not the first guy to have this happen.



https://www.turbodieselregister.com...howresults&searchid=121249&sortby=&sortorder=

 

[hsmith]

Talked with piers. He is sure the timing is retarded. Will do that check first. Will keep you all posted.

Thanks again, hsmith

 

[krs]

Timing sounds like about the only answer.



Valves float only at high revs if the springs are too weak to close them quickly - float has nothing to do with mixture or boost. Seems to me that if there's black smoke it'd be hard to think that the mixture is lean. Black smoke is too much fuel for the burn - in gassers and in diesels too.