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  #16  
Old 07-29-2006, 01:06 AM
ForcedInduction
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Quote:
Originally Posted by Brian Carlton
If the IAT climbs by 100°F. due to a boost increase (with no additional fuel) and the EGT climbs by 75°F.
ANY increase in EGT's without an increase in fuel rate is not desirable.

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  #17  
Old 07-29-2006, 01:10 AM
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Quote:
Originally Posted by ForcedInduction
ANY increase in EGT's without an increase in fuel rate is not desirable.
I'll give him the benefit of the doubt here.

If the EGT's increase at a slower rate than the IAT's, the engine is more efficient with the additional air.

Why are you concerned with the higher EGT's.......unless they get dangerous??
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  #18  
Old 07-29-2006, 01:16 AM
ForcedInduction
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Quote:
Originally Posted by Brian Carlton
Why are you concerned with the higher EGT's.......unless they get dangerous??
I can already get 1400*+ without any IP changes.
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  #19  
Old 07-29-2006, 01:28 AM
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Quote:
Originally Posted by ForcedInduction
I can already get 1400*+ without any IP changes.

............yep.........that's dangerous.........

I really have to dial mine back into the 12's..........I'm probably up there myself..........
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  #20  
Old 07-29-2006, 10:05 AM
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Brian
I've read all you responses and there is some error on my part. (I misunderstood the max psi for this engine and did not realize I was way past the safe limits of the turbo)
I'll defer to my experimenting with my 2LT Toyota diesel, as Connclark eluded to this is what I found....
1. I'd add fuel via the FLS (Fuel limit screw) this adds fuel thru the entire rpm range, (I assumed that the alda also enriched the fuel thru out the rpm range as well, no matter as it would be easy to prove if it does or not)
2. After adding fuel I'd get awesome power increase but I'd see dangerous EGTs, so I'd increase the boost a couple PSI and the EGT's would drop back into the safe range, and the power gain was drastically increased
3. so I'd increase fuel again until I hit dangerous egt and increase boost to drop it.
Finally I added a intercooler,(that dropped EGT's) and again it could handle more fuel
4. I never measured IAT's during my playtime with the 2LT, as I was only really interested in keeping the EGt's under control, I never looked for a relationship between the IAT's and EGT's, I understand Higher IAT's will not net as much power as the cooler dense air will, and the cold air helps drop EGT as well
This whole process was done in small increments..in the end I had more power than a 2LT came with and EGT's that stayed under 1000F and boost that was running 14psi (stock setting was 7-8)
If you’re already punching high EGT just for fun increase your boost 3-4 psi and see how much if any Your EGT drops. This would give you proof in the pudding so to speak
A fact as I know it is, that higher boost never killed my engine, it was the too high EGTs that did, and the fact the engines are known to drop pre-cups, mine were heat cracked and because of it one broke and fell on top of the piston.( I posted the story on toyotadiesel, basically I was stranded 160kms from home in dead of winter(-30C) with the family in the car and had to keep driving with IP bolts sheared off and the egts were pinned to 1400F plus for 1.5 hrs)
Another way to look at is adding more fuel creates more heat (EGT) and you can destroy an engine very quickly with extra fuel. A diesel is exactly opposite of a gas engine, the leaner it runs (air fuel ratio) the cooler it runs (EGT wise)
Again my two cents
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  #21  
Old 07-29-2006, 10:44 AM
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Quote:
Originally Posted by nickg
1. I'd add fuel via the FLS (Fuel limit screw) this adds fuel thru the entire rpm range, (I assumed that the alda also enriched the fuel thru out the rpm range as well, no matter as it would be easy to prove if it does or not)
2. After adding fuel I'd get awesome power increase but I'd see dangerous EGTs, so I'd increase the boost a couple PSI and the EGT's would drop back into the safe range, and the power gain was drastically increased
3. so I'd increase fuel again until I hit dangerous egt and increase boost to drop it.
What begs the question in this phenomenon is why didn't the factory run more fuel and more boost if they could safely control the EGT's under all conditions?

There has to be a piece of the puzzle missing here. If additional horsepower was available from that engine.......without damage......why is not provided from the factory?

My guess is that your testing procedures are not all encompassing. There must be a point in the operating range where you are seriously high on EGT's...........or the factory is simply incompetant............???

But, it's noted that you did get a reduction in EGT's from additional boost...........I'm still not fully grasping that bit of data..........my only guess is that you overfueled the engine by the addition of more fuel and the additional air was required to burn it.

In the case of the SD, the fuel is constant........no adjustment from the factory setting. So, we can be relatively assured that it's not overfueled. In this case, I'd have a very hard time believing that the EGT's will drop from additional boost. You are adding hotter air to the engine which already has sufficient air to burn all available fuel.

How is this going to result in lower EGT's??

Like I mentioned.........I'd like to see some data.

In you case, I would have liked to see the boost added before the fuel. If the EGT's go down.........I'd be amazed.
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  #22  
Old 07-29-2006, 12:19 PM
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What if Wastegate Wasn't Working?

I'd like to ask an aside question here.

3 weeks ago I purchased an '87 300D turbo, 134K miles. Over tha past 3 weeks of going over it and prepping it for being a daily driver, I discovered that the pressure hose to the wastegate actuator was rotted off at the fitting on the turbo housing. I've since replaced it with some available 1/4" thick wall fuel injection hose.

The drive home from the dealer was 80 miles on the interstate, 65 and 70 mph on cruise control mostly, no romping or gunning it, rpm never saw 3000 for the whole trip. When I arrived home, I topped off the tank and it took less than 2 gallons, approaching 40 mpg for the trip.

Also, there was an excessive amount of oil in the intake boot from the CCV/breather connection. So much there was liquid oil in the boot, and had run down the turbo and side of the engine over time and made it look like there was a significant oil leak on the engine itself, and even backed up into the flapper box upstream of the boot. OIl and crud was built up at least 1/4" thick on the underside of the boot and front of the turbo.

My theory on the oil - excessive boost on output means excessive vacuum on inlet, and it was literally sucking oil vapor out thru the breather hose at a rate the oil separator in the valve cover couldn't handle.

Any feel for what boost levels might have gotten to, given the engine wasn't revved over 3000 rpm, if the wastegate wasn't working?

Given the discussion so far, if the turbo was putting out higher than normal boost due to a nonfunctioning wastegate, and the overboost circuit was keeping the engine defueled to "normally aspirated" levels, could that explain why the beast gave every indication of getting close to 40 mpg on the trip home?

Thirdly, what would you recommend I check to ensure that this didn't do any damage to the engine over time?
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  #23  
Old 07-29-2006, 12:31 PM
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Quote:
Originally Posted by retmil46
My theory on the oil - excessive boost on output means excessive vacuum on inlet, and it was literally sucking oil vapor out thru the breather hose at a rate the oil separator in the valve cover couldn't handle.
A diesel doesn't run with any vacuum, it runs with pressure in the manifold......especially on boost. The engine takes whatever oil vapor is delivered by the crankcase. This is strictly a function of blowby. If the engine has significant blowby.........there will be more oil for the breather to dispose of. Sometimes it does leak from that hose.

Quote:
Originally Posted by retmil46

Any feel for what boost levels might have gotten to, given the engine wasn't revved over 3000 rpm, if the wastegate wasn't working?
The overboost protection valve will limit the boost to 15 psi........if it's properly connected and working.

Quote:
Originally Posted by retmil46

Given the discussion so far, if the turbo was putting out higher than normal boost due to a nonfunctioning wastegate, and the overboost circuit was keeping the engine defueled to "normally aspirated" levels, could that explain why the beast gave every indication of getting close to 40 mpg on the trip home?
The overboost circuit will limit the boost to 15 psi........it won't reduce it to zero.

Fuel economy cannot be measured with one tank. Keep a running log and average five tanks or more. Then, if you still get 40.......better start a new thread........that's practically unbelievable.

Quote:
Originally Posted by retmil46

Thirdly, what would you recommend I check to ensure that this didn't do any damage to the engine over time?
Nothing. If the overboost circuit was properly working, you could not have done any damage.
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  #24  
Old 07-29-2006, 12:37 PM
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Quote:
Originally Posted by Brian Carlton
What begs the question in this phenomenon is why didn't the factory run more fuel and more boost if they could safely control the EGT's under all conditions?

There has to be a piece of the puzzle missing here. If additional horsepower was available from that engine.......without damage......why is not provided from the factory?
I'd think that Mercedes built their engines to survive in the most extreme condidtions. They know that the USA is alot hotter in many places than Europe so they held back the fuel. Melting engines on our 110*f days is not good for PR after all.
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  #25  
Old 07-29-2006, 12:40 PM
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Quote:
Originally Posted by Brian Carlton
Nothing. If the overboost circuit was properly working, you could not have done any damage.
15psi is still quite alot of boost without an intercooler.

If the overboost is working, you should feel the car bucking back-and-forth as the pressure signal to the ALDA is interrupted.
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  #26  
Old 07-29-2006, 12:44 PM
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Quote:
Originally Posted by ForcedInduction
I'd think that Mercedes built their engines to survive in the most extreme condidtions. They know that the USA is alot hotter in many places than Europe so they held back the fuel. Melting engines on our 110*f days is not good for PR after all.
He's referring to a 2LT Toyota diesel. Of course, you could apply the same logic........the engine has a significant reserve for the application of more boost and more fuel..........but.........your own results with EGT's seem to point otherwise.
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  #27  
Old 07-29-2006, 12:47 PM
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Quote:
Originally Posted by ForcedInduction
15psi is still quite alot of boost without an intercooler.

If the overboost is working, you should feel the car bucking back-and-forth as the pressure signal to the ALDA is interrupted.
Agreed

and agreed.


But, he won't do any damage at 15 psi unless it was on continuously.........upgrade.........for a looong time..........

Quote:

I'd think that Mercedes built their engines to survive in the most extreme condidtions. They know that the USA is alot hotter in many places than Europe so they held back the fuel. Melting engines on our 110*f days is not good for PR after all.
Now, who said that..............????
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  #28  
Old 07-29-2006, 01:02 PM
ForcedInduction
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Quote:
Originally Posted by Brian Carlton
Now, who said that..............????
Well, I guess I'm in my own little world where I think Mercedes was *nearly* perfect.
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  #29  
Old 07-29-2006, 07:36 PM
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Brandon314159 had data from when he blew out a hose on his intercooler. His egts went up with no boost. Think about it, at sea level under 11psi at 5000 rpm your engine sucks in 18.01 lbs of air at 95 degrees C. At sea level at 13.5 psi of boost your engine sucks in 19.19 lbs of air at 106 degrees C. If have to raise the temperature of two different air masses using the same amount of energy, the larger mass will have a cooler temperature. If your raising the temperature to over 600 degrees C, the 11 degree C IAT increase becomes insignifigant compared to the difference due to having to heat the extra pound of air.


Calculations made using turbo calculator
http://www.not2fast.com/turbo/glossary/turbo_calc.shtml?FeetASL=0&Tamb=21&Bore=90.9&Stroke=92.4&nCyl=5&RPM=5000&VE=65&Boost=13.5&Ec=70&Eic=0&PdropIC=0&TambIC=21&wiPercentMethanol=50&wiRate=100&wiTemp=21&SFC=0.49&AFR=13.3&maxInjectorDutyCycle=85

Increasing the specific heat ratio by as little as 0.03 can result in as much as 7.5% more power assuming an ideal diesel cycle. Do the calculations yourself or have a computer do it for you. Sch uman automotive link http://tinyurl.com/kzfcc
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  #30  
Old 07-29-2006, 07:57 PM
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Quote:
Originally Posted by ConnClark
Brandon314159 had data from when he blew out a hose on his intercooler. His egts went up with no boost.
No surprise there. Without the boost, he was overfueled.

I'd like to see an engine such as my SD, reflect a drop in EGT's if the boost is increased..........stock fuel settings.

Brandon's data is not valid due to his increased fuel.

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