Fuel Consumption Issues - TIER 3 ENGINES 1

[KBasson]

Good Day All

It will be appreciated if anyone could shed some light on a specific problem I am currently experiencing with the fuel consumption of TIER 3 engines as opposed to TIER 2 type engines. I operate a number of drill rigs within the mining industry in South Africa and with the introduction of the TIER 3 diesel engine technology, I have experienced a dramatic increase in specific fule consumption (32%). This is obviously not acceptable to me and I am sure that all will agree with me in this respect. Besides the environmental aspects/benefits, I am not achieving any benefit by using these types of engines within my fleet from a commercial perspective. Can someone please explain to me why these new engines are running at far higher fuel consumptions as opposed to the older generation engines. The OEM cannot give me a detailed explanation from an engineering perspective as to why this is the case. Your insight into this regard will be highly appreciated.

Thank You

 

[GregLocock]

What duty cycle do you use? What power engine?

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[KBasson]

Hi Greg

The engine used on the drill rig is a QCC industrial engine (cummins) 280 BHP (209kW) @ 2200 RPM. The engine is running at a duty cycle of around 90%. Please note that both TIER 2 & TIER 3 engines are running exactly within the same application. The duty requirements has thus remained the same in terms of the application. The only difference is the fact that the fuel consumption has increased dramatically as a result of the design of the TIER 3 engine. I am thus trying to understand from an engine design point of view, why this would be the case.

Thank You

 

[mattsooty]

I can think of 2 possible reasons:-

1) Running less advanced injection timing to reduce NOx production, thus increasing BSFC

2) Using multishot injection to reduced noise & NOx production

MS

 

[GregLocock]

Well, yes, but at least on the John Deere site they claimed better fuel consumption for their Tier 3 engines vs the Tier 2 ones, for the ones I looked at.

The Cummins site didn't seem to be able to give me such a useful comparison.

K, do you have BSFC maps or graphs for the Tier 2 and Ter 3 engines? What absolute numbers are you getting? do they agree?





Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[romke]

32% is quite a lot and the end effect would be that you still generate as much pollution as you did with a tier2 engine with the same rating. that is not what the standards are meant to achieve, so there must be something definetely wrong. the more stringent regulation may mean that you have to aaccept a change in consumption of say up to 3%. but a tenfold value obviously is not what to expect. are you sure that the injection system is spot on?

 

[MikeHalloran]

I'm reminded of the early 70s, when SI engines got 'cleaner', but power went way down, fuel consumption went way up, and their exhaust would eat the chrome off a bumper. Computers, and the dynamic behaviors they could arrange, eventually brought back the performance that was lost, and then some, but it took two decades to learn what the computers had to do and teach them to do it.

Some mfgr's Diesels quietly gained 8..10 pct displacement in the jump from Tier2 to Tier3, suggesting that they are way down on specific power. Many, maybe all, of them already have computers, so maybe performance recovery will come in a single decade... or maybe never.



Mike Halloran
Pembroke Pines, FL, USA

 

[CCycle]

This 32% is about the same as seen with the new, over the road truck engines. I am not into trucking but have friends that have traded their nice new trucks for mid 90s trucks that have single turbochargers and do not use exhaust recirculation or filters. They rebuild the older trucks and pick up typically 2 to 2.5 mpg over the new rigs. With the miles they drive this is the difference between a nice return for their work and bust.

 

[dicer]

The elimination of O2 with EGR.
Less compression.
Cooler combustion.
Less heat means less power extracted from the fuel so more fuel is needed to do the same job.

I just wish a people would wake up to all the enviro/global warming lies.
Its just that simple.
Before answering think water melting on the planet Mars.
And hot spots in the middle of nowhere in California. And oil naturally bubbling forth from the earth and marine life eating it per a scientific american story years ago.

And Mike H, the milage and performace could even be higher if the emission thing was not an issue.

And this is why Caterpillar is leaving the truck engine business?

 

[CCycle]

Dicer writes:
The elimination of O2 with EGR.
Less compression.
Cooler combustion.
Less heat means less power extracted from the fuel so more fuel is needed to do the same job.

This is mostly right. The EGR reduces the percentage of O2 in the charge.
They may have less mechanical compression but the effective compression is the same or greater.
They do achieve cooler combustion and do have less overall fuel efficiency.

The new engines use dual turbochargers in series. Max boost is around 40 psi for the dual turboed engines and is about 30 psi for the older single turbo engines.

About 5% of the shaft power of the new engines is picked up from the exhaust. The turbos pressurize the intake charge which results in a small power stroke during intake. But even with this the engines are down on efficiency.

To my knowledge Cat is still in the engine business but their new engines use dual turbo/EGR techniques. Cat for several years fought the EGR thing but had to capitulate.

And, Dicer is unfortunately correct about the "enviro/global warming lies"
Environmentalists do not realize that what they are doing in trying to produce weather conditions of 200 years ago is ruining the world. We need the additional CO2 and NOx. The world is fed by photosynthesis which uses sunlight, CO2 and water to produce starch. This conversion is highly sensitive to CO2 level. The additional CO2 we have now is producing increased yields. NOx produces fixed nitrogen which is the most costly and energy intensive part of farming. If we are to feed the almost 7 billion people crawling on this earth we need all the help we can get. We certainly do not need less efficient engines.

 

[JSteve2]

KBasson,
32% fuel consumption increase is far outside the specification for Tier 3. It's a virtual certainty that one of the following has occurred: a) the engine is lower rated and therefore is operating at a higher consumption point to generate the same power, b) the application has changed in some way that you are not aware of, c) someone is stealing fuel from you (shock - it's happened before), and/or d) there is some maintenance problem or failure with the engine (any fault codes active, correct fuel being used, etc.??).

The OEM will not have the information you need. You should contact a Cummins dealer or a Cummins Application Engineer - if you are experiencing a real phenomenon they will no doubt be very interested in your situation.

 

[EdDanzer]

The primary problem is the new engine is not efficient at the RPM and load you are pulling. In 1999 we did some design work on a vehicle that need 200 hp continuous for about 4 hours per day. An engine that was rated at 275 hp would use enough less fuel at $2.00 per gallon to have a 1 year pay back on the increased cost.

It is almost impossible to get an accurate fuel map for any engine so you can make an intelligent choice. If you want to spend $15K+

http://www.swri.org/

can supply independent fuel economy information.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[dicer]

http://www.aednet.org/aednews/index_full_story.cfm?id=10923395

Caterpillar getting out of the truck engine business.

 

[catserveng]

CAT came into 2008 without a major US truck manufacturer offering their engines as standard. The worldwide equipment business has been good, and the challenges of meeting the next tier emissions were consuming a lot of resources. The proposed CAT truck is pretty application specific, and will likely be a slow starter in the US.

I left the CAT family early this year, to me it looks like they are pulling back to their roots and keeping the stock market happy. I worked mainly on the Electric Power side and have seen a lot of changes in the last few years.

On the fuel consumption issue, virtually all of the 2008 emissions certified product had higher fuel consumption than the previous certification years, for all of the reasons described above. The cost of squeezing lower NOx emissions out of these engines results in the fuel consumption penalty. When I worked for the dealer, in the truck and industrial side we saw bare engine fuel consumption rates go up from 4% to 12%, the effect of installed aftertreaments systems made that even worse. Add on top of that the fuel BTU content has also gone down as the newer low sulphur fuels also have a higher API number.

Overall the current emissions reduction strategies have had a pretty significant negative impact on fuel consumption for just about everyone's diesel engines. I think everyone would agree that the emissions reductions are needed, but they doesn't seem to be a balance between the amount of energy in and the work energy and emissions out that makes sense.

The 36% percent seems at the very top of the scale, but there are probably a lot of factors affecting the comparison of those numbers.

Just my two cents worth.