The gasserization of the Diesel engine -- PSD, DMX

[Hohn]

Seeing the threads on the PS Fords and the Duramax GMs, I feel that I have to comment on their power ratings, and therefore on HP in general. I will use some generalizations that there are, no doubt, many exceptions to.



The trend that GM and Ford are clearly following (if not leading) is towards a higher-rpm, more gasser-like diesel engine. Rumor has it that Mercedes is working on a diesel that revs easily to 4000 rpm as a passcar motor. That is also the trend in diesels in general as they look at ways to use a diesel in cars to increase efficiency.



The biggest obstacles to marketing a diesel engine are pretty easy to name: noise, smell, and power delivery characteristics. The latter I will term the "fun to drive" factor, based on the marketing dogma that higher rpm means more driver enjoyment.

Manufacturers have addressed the noise and smell, as modern diesels are cleaner than ever. Yet, the sales and demand just aren't there. To wit: the VW TDI. The TDi gets fantastic mileage and has pretty good durability, but sales are still lackluster. Why? It's because it revs slow, and not very high. That means it doesn't feel as much fun to drive (so the marketeers believe).



A dyno does NOT measure HP, it measure torque. Hp is calculated. Tq is what moves the load. How fast you can move it is HP. Said another way, Hp is related to time AND force, while torque is just force. Torque can be multiplied by gearing; HP cannot.



Look at is this way, if I could take the torque of my BONE STOCK ETH up to 4000 rpm, it would make 385 hp!! At 6000 rpm it would be 576 HP!! The only real test of “horsepower” is how fast something can accelerate a known load from pt A to pt B. No, the highest rated HP motor doesn’t always win. There is a flaw in the way HP is measured. By existing standards, you can “gain” hp just by using a lighter flywheel or doing something that lets the motor build revs faster.



Or consider this: if you bombed a 24v motor, and a 12v motor to the exact same HP level, the 12V would have more torque because it generally won't rev as high.



This is why the Diesels from Gm and Ford are V8s. Not only because they can market the 8cylinder engine as an advantage, but because having more cylinders of smaller individual displacement is more appropriate for higher rpm. This is why Formula 1 Engines often have 10 or 12 cylinders even though they are less than 3. 5 liters displacement. Those tiny pistons will rev forever into the 12K rpm range and up. BUT they have little power down low—launching the car is tricky without killing it.



A high-rpm, V8 diesel is a step in that direction, although not nearly as extreme. Unfortunately, as you move that direction, you give up some of the main benefits of a diesel to begin with—more low rpm grunt, etc. As Larry Widmer (best gasser engine man I know of—smokey yunick learns from him) likes to say RPM= Ruins People’s Motors.



The way I see it, Ford and Gm aren’t trying to build a better diesel. They are trying to build a better gasser, and using diesel technology to do it. A diesel excels when used on long stroke, big cylinder, lower rpm engine designs (think OTR diesels from Cat, Cummins, and others, as well as RR diesels). The PS and DM motors are running higher RPM and being whipped like a horse on the home stretch. They are moving towards being a racehorse/showhorse. I want a draft horse. The Cummins is just that. It can loaf all day doing the work that the others are giving 100% to do.



If you want to see performance, wait until they mate a high-torque diesel to an Electronic Continuously Variable Transmission (ECVT). It’s a transmission that has a high and low limit for gear ratios, but can achieve any ratio in between.



Until then, I keep my draft horse fed and groomed, knowing he will be good in the long haul.

HOHN





(PS-- I know I talk out my butt sometimes, and will admit wrong when corrected)

 

[JoeyD]

Isn't the new H. O. Cummins rated HP only 200 rpm lower than the GM or the Ford? Would this mean that the Cummins is also following this trend?

 

[Champane Flight]

Base and brake.

I forget, but the difference between Base hp and brake hp. A engine in a rig like the "Signature 600" is 600 hp, but is it base or brake?

 

[Joe G.]

There is another rating I've seen on comercial engines. A continous load horse power rating. That being the HP it delivers over a long period, not the short term maximum it can deliver on a dyno.

 

[WadePatton]

Yep, like trying to feed the masses--everything begins to taste like mush -bland and inoffensive to all.



I certainly understand trying to sell more product, but I often see products ruined by catering to whom they think will buy it. Design by those who don't know what they want rarely creates an excellent product. When they make light diesel trucks indistinguishible from gassers, we will have really lost something.



Cummins has taken one step in that direction with the girlie motor, but I have faith that they will not abandon the I-6.



Oh yeah, the F1 engines have pnuematic valvetrains-that's how they pull 16,000+ RPM without floating the valves. Back in the 80's they were making 700+HP(more for qualifying) with 1. 5 liter 4-cylinder, turbocharged engines.

 

[pkennedy]

One would read this thread and believe that this theory of gasserization may be true, on the other hand I have driven I6's and diesels since I was 16 years old and along with this gasserization has come comfort. Pick up trucks were only 30 years ago a tin can noisy and less than comfortable than most economy cars. We started to travel more with bigger loads and toys which cars with hitches could not handle, marketers began the truck revolution to where we are today. Barn yard Caddies with pulling power and we want more, now we expect to tow 10-20k trailers and follow cars at 75 mph with no smell,noise or discomfort. Then we expect good fuel milage and race car acceleration, I think the manufacturers have only supplied what we asked for because there is profit in it. I will agree they dont always get it right but then their parts market would also suffer if they did. The minority who drive vehicles like TDI's have their reasons which most enjoy without VR6 acceleration, look closer at the sales stats and you will find both VW and diesel trucks hold more pre-sold orders. The used diesel vehicle market also enjoys higher resale values and lower inventories than gassers. Footnote VW has reduced their gross rpm on diesels in 1978 from 6100 rpm to 4400 in the new cars while increasing performance levels respectfully. PK

 

[COBRAJET]

I don't understand the part about the PSD and the DMAX being flogged at 100% while the Cummins loafs. The PSD makes marginally more torque at a little higher peak RPM, but is still over 525Ftlbs where the Dodge peaks. It produces more HP than the Cummins at any given RPM above 2000. It is not straining. The DMAX performs about the same with slightly less power than the PSD or the Cummins. The higher revving is more for emissions. The 24V Cummins revs to 3300, the old 12 valve was closer to 2800. Consumers like acceleration and the V-8's will always outperform an inline in that regard. The PSD and the DMAX will out accelerate a Cummins all day long... many sources prove that on a monthly basis. Inlines simply do not rev quickly. The Cummins is a fantastic engine, but it has its hands full with the competition just as they do with it. It is definitely not loafing. I have owned several of each and they both have their advantages... ... . loafing while the other is at 100% is not one that either enjoys... . CJ

 

[baby.driver]

Don't forget Offenhauser was a four cylinder <160cid and 700+ HP

 

[Eric Kahn]

The VW TDI is not slow to accelerate like you think, a stock one will accelerate about equaly to the base 2. 0 gas engine in the US, it does alot better once you have reversed all the De-tuning that was done to meet US emmissions ( have not done that on mine yet, no cash now due to paying cash for Dodge PU) and its actual rev limit is 5200 (computer limited) the tach redline is 4400 but you usually do not get there, my stock one stops pulling as hard about 3500 and it is time to shift

VW also uses a 2 stage injection system on the rotary pump TDI's sold here, not sure what they are using on the PD diesels sold everywhere else, but what they are doing here (the US) has resulted in a very quiet diesel

the trend towards V engines has to do more with space than any other issue, it is simply easier to package a short V engine into a smaller vehicle without impacting interior room than in inline 6, and is you stick that engine in sideways and use FWD, you can have even more passenger room in your small car

the best example I can see of this is the current popularity of mini-vans, withour the sideways engine and FWD, I do not think they woulf be nearly as popular because most people do not want to deal with the wonderful interior engine hump that the RWD vans had, and if you put a longer hood on it to eliminate the hump, you now have an SUV, not a mini-van

another example i can think of is the first gen CTD dodge and how tight the engine is in the engine bay compared to the second and newer generation trucks which were designed with a longer bay (longer hood) just so it would fit better

Love my dodge, just wish it did not hold onto third gear so long

 

[Kernel]

HOHN,



What a great explaination and well thought out point of view on how the diesel engine has evolved. I am sure if you stated this to most of the PSD die-hards, you would get more than one look.



Like WadePatton said, and I agree, I don't blame anybody for wanting to change their product in such a way as to improve sells, give the masses what they think they want, or like COBRAJET mentioned, emissions.



Unfortunately it now seems like Dodge is following in what GM started and Ford perfected, a diesel that "performs like a gas engine. " (Thankfully GM got away from that gas engine conversion thing-I'm still a Chevy Man at heart).



What it all boils down to is sells, marketability, and making the consumer (within reason to the EPA) happy. Too many of the "new diesel generation" (my generation) have forgotten how a diesel is supposed to run. RPM's, peak torque in relation to horsepower, how nice of a curve it makes on the dyno is irrelevant IMHO. I guess that is due to my "old school" upbringing and farming experience. There were two basic categories, the gas tractors and the diesel tractors. When you had to operate for long periods of time, the only logical choice was the diesel. It ran cooler, used less fuel, and could run at lower RPM's with ease and got the job done better. To keep from rambling on more, basically if you want the RPM's and a diesel that "performs like a gas engine" then don't waste your time and just buy a gasser.



I hate to say it, but the days of the "real diesels" are coming to a close. Around here atleast, a diesel seems more like a status symbol than a workhorse. I am proud to say I got mine before I came here, and my truck has been used, I got the dents in the tailgate and stories of almost getting it stuck in the "back pasture" to prove it. I will leave those stories for another thread someday.



It will be a sad day when I say good-bye to my 12v'er, and then I will be left to wonder where the rattle went.



Scott

 

[Jeff H]

How can you compare these engines? None have the same cid. Bigger cid engine is will usually generate more horse. One reason the v8s can get up and go is do to there short stroke. Shorter stroke motors can really run some high rpm's The Navistar Power Stroke has a shorter stroke than the Cummins. So naturally the v8 diesel has a big advantage here. Then you add 2 more cyclinders to help you get that v 8 to move.

So here's my question? If the v8's are so great. Why is Dodge still using the measily little Cummins? Why are there people still buying these trucks? I thinks its for there reputation.

 

[Champane Flight]

Still

I kind of think we got off track. The gasserisation started with the V-8 IMHO. People have been sold on the V-8 since its conception early in the last century. It can develop more HP in less space in gas apps. It can out accelerate any other engine design. Now after years of V-8 sales we come upon the diesel P/U era. People are still thinking V-8, whether diesel or gas. They think "Well, my old V-8 would outrun my old inline six, soooo".



I still think inline when it comes to diesel. I come from a long line of truckers. When the V-8 diesels came out in the sixtys and seventys almost everyone went for them in the trucking industry, Including myself. But, as the inherit problems with the design came into veiw, we all began to bail.



They would accelerate hard, then at the first sign of a hill with an 80,000lbs weight, they would start to loose speed, until you were in the bottom side. Meanwhile the old Cummins inline would continue to hang on to this RPM and pass you about halfway up the mountain. The V-8s were a bear to work on, and had lower fuel mileage. The lifespan of the V-8 was shorter than the I-6. You could get 300,000 miles out of a detroit, but it took a good driver.



This is in rigs of course, I know some of you PS and DM drivers are saying "We drive P/Us, not rigs". But after driving V-8s for ten years and a million miles, I wouldn't ever want another in a diesel.



The gasserisation everyone is so concerned about is just progress and EPA. It is natural for companys to make engines with the "latest" technology. The new P/S is years and years of technology and progress. I have to hand it to International/Navistar for sticking with it, many other engine manufacters would have dumped the small V-8 years ago, when they were doing MAJOR catchup between 89 and 95.



Some of us buy a pickup for its hauling ability. But lets face it, most buy them for hauling grocerys from the store. It is kind of like four wheel drive, most people will buy it but only use it maybe two or three times in the vehicles lifetime. So why do they want a big diesel with fourwheel drive and a V-8? Because some have bought ONE brand for the last 40 years. And you NEVER know when you might need all that power and traction... ... ... ... ... Of course having enough money helps.



My old 95 12 valve will outlast me and then I will leave it to a good home in my will. I don't think many of the V-8 owners think that way, most sigs are of the 2000+ variety... ...

 

[D6Diesel]

A signifigant step towards " gasserisation" might include the addition of EGR and crankcase ventilation routing to the air stream. The TDI engine comes to mind. I'm trying to figure out how fowling the motor is a step forward for the EPA folks.

 

[Jeff H]

Champane Flight got it right! !

I've been to quite a few semi truck pulls now. One I especially like is the super modified rigs. Trucks running with detroit diesel v12's with quad turbos. They are quick off the line. But when they hit the 275 foot mark they lose there snort and usually drop down a gear. Then you have the guys running with minus 6 cyclinders from the v12. Were talking the I6's. Cummins really has this one covered. Lets throw a 1150 cid engine underneath with a quad turbo set up. They are a little slower at the start. But once the turbos are spooled up that engine will hang in till he loses traction. A full pull is quite a site too see.

 

[WadePatton]

Whoever it is that thinks v8 diesels are faster than I6's hain't been to the dragstrip or truck pull lately. I can send you a tape.



I don't care what kind of ET's Consumer Review can turn. I want to know what DD can do!

 

[COBRAJET]

I am perfectly aware of what a BOMBED Cummins will do... . I own one. I am also aware of what the public wants... STOCK acceleration... which the V-8's deliver. We also want four real doors... . CJ

 

[Jeff H]

If yer serious about the video tapes I'd like one. I'm sort of a tractor truck pulling junkie.

 

[JyRO]

Gasserization...

You can look at the trends of diesel engines as gasserization, or you could look at it as response to market demand. Response to market demand is all it is. The big 3 want to make money. To make money they got to sell trucks (vehicles). To sell trucks they have to try to make them more to what the masses want. The "masses" want it all. Quick acceleration, good top-end power, torque, fuel efficiency, etc.



Let's look at us Cummins guys, I'm a guilty one too. We buy our trucks and in stock form they won't out accelerate a PSD or DMax. And that in itself makes sense. Even if the Cummins made identical HP & TQ as the PSD and/or DMax, those V-8's would still out accelerate (traffic light to traffic light) the Cummins. Why? For one of the reasons we Cummins people like to brag about ----> Size of pistons, connector rods, bearings, etc. etc. etc. The Cummins is built way more massive than the V-8's. And that mass slows acceleration down. But helps with pulling grades. I prefer it that way myself. I didn't buy mine with the intention of racing PSD's and DMax's away from traffic lights. So we bomb them to get them to make more power, so we can race the PSD's and DMax's at the lights. Or to pull a 5'er more satisfactorily, which is why mine has a couple small things done to it.



Doesn't the fact that us Cummins guys bomb our trucks tell us something? Like, we want them to be able to get off the line quicker. Coming off the line quicker certainly wouldn't bother me. That's probably the greatest factor of why Ford and Chevy keep the V-8's. People like to get off the lines. Most don't want to get their hands dirty bombing their trucks, or even changing their own oil. They want a quick, quiet stock truck.



A lot of us Cummins guys brag about how long the Cummins will last before the first rebuild compared to the V-8's. But how many of us are willing to keep their truck for that long and that many miles? I'm guessing that percentage would be extremely low. There's a few around that will, I like to think I will. All I know is I'm keeping my truck for 10 years and how many ever miles that is. Most will trade their trucks at anywhere from 2 to 6 years. So, the longer lasting engine argument is irrelevant for most. This includes PSD's and DMax's. Sure, their motors won't last as long as a Cummins, but 99% of the owners won't even keep their trucks long enough to wear them out either. So most V-8 owners don't care that their engines won't last as long as a Cummins ... just as long as it will last until they are ready to trade it in. In that respect, most people don't care that their V-8's are not built as massivly as the Cummins.



I can see a trend coming with the Ram. Look at the weight of the Ram. Its heavy. That effectively gives the other 2 brands a payload advantage. Does that payload advantage mean much? I think it does. I'm about 400 lbs. over my GVWR when I tow. All else being equal with my truck, I wish it were 500 lbs. lighter so I'd be under my GVWR. I think the Ram will get lighter. One place to look is the engine. I think the future Cummins will get less massive, and it won't matter to most. It will accelerate quicker (have more power because the market demands it), may even be smaller displacement. Hey, Cummins has already made it quieter in response to the quiet DMax. That quietness is not all due to the new common rail, or emmissions related ... Cummins did extensive investigation to determine where the noise was coming from, and made changes to the engine, like the bottom of the block area, to make the engine quieter. Market demand driven changes.



The point to all this rambling is, I think I agree that diesels are getting gasserized. And I think its because the masses prefer the way a gasser drives and the squeaky wheel gets the grease. I don't care that my truck is slower off the line than the other 3. If that's all I was concerned about, I'd go get another $4000 crotch rocket and blow everbody off the road, or bomb my truck more heavily, or go get a PSD.



- JyRO

 

[WadePatton]

I got it from Diesel Horsepower- Chris and Allen Stoner. There's some of the big name pullers on it and some 1. 8 mile drags--mostly Fords. It's a home spun tape. I'll dig up their contact info. I don't have a way to duplicate it.

Originally posted by Jeff H

If yer serious about the video tapes I'd like one. I'm sort of a tractor truck pulling junkie.

 

[Joe G.]

JyRO makes some good points. I guess I'm one of those who will keep mine until it wears out or I wear out. Not interested in the 3rd gen trucks or in other brand trucks. Not interested in quiet diesel engines. I'm not going to buy any of them. The way I'm going and my truck is going I expect to leave it to my son. I bought this one because it has a Cummins inline six. The first time I saw a Dodge with one of these I thought it was a custom conversion. Then I had to have one. I'm still kind of amazed that this engine is available in a pickup truck.