Forum Discussion
- Good d lord that chevy is awful.... Woof
FishOnOne wrote:
As for the high fuel pressure I agree it helps with reducing emissions so HP can be increased, but you said that higher compression ratio increases an engines efficiency which makes perfect sense. I'm wondering if the reduced compression ratio is more about improving emissions while supporting more HP, at the expense of efficiency.
Yes you are correct that they had to decrease compression ratio in order to increase power while meeting emissions, but htis can be negated some with increased fuel pressure. This is why only the high output Cummins with the Aisin has the lower 16.2:1 ratio while the standard output with the 68RFE has actually increased its compression ratio to 19:1 compared to previous years. I bet you would get great fuel mileage if you tuned and deleted the 68RFE version of the 6.7L. And all the power that could be had if you removed all of the stock de-tuning just to meet NOx emissions.FishOnOne wrote:
ShinerBock wrote:
FishOnOne wrote:
This conversation should be about the Duramax L5P and the current cummins with the CP4 and reduced compression. I'm hearing reports that the latest cummins is making less fuel mileage than the previous generation and maybe requiring more turbo boost now to make equivalent power.
Can you please post any links where you have been hearing these reports? I would love to read them because some new Cummins owners like Lavon Miller at Firepunk diesel has been doing video blogs about his new 2019 Cummins he just bought with dyno and others tests comparing it to his 2017 stating otherwise.
Also, reduced compression is likely due to the increase in fuel pressure coming from the CP4.
No official links but my cousin mentioned that the service department has received several complaints on fuel economy on the '19 trucks are noticeably lower when either pulling or running empty. Also I spoke with a hot shotter who I know that handles a lot of our material handling between our sites reported lower fuel economy compared to his 4 gen. It maybe a bit too early but it sounds like something is going on.
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:R :R :RIdaD wrote:
I'm kinda maxed out on how many times I can watch some fat guys drive up a hill.
I am dying. :B :DShinerBock wrote:
FishOnOne wrote:
If this new cummins HP is understated then one can say that about the Duramax used in this test.
Not exactly. There is nothing in the rule books saying that you can report lower power numbers than the SAE test. There is, however, rules stating you cannot advertise above it. We seen this during the 90's and early 2000's when all of the Japanese car makers had a "gentlemen's agreement" not to advertise their cars over 276 hp even though many of their sports cars were making well over that. - Japan Dumps 276-hp Pact
A manufacture can add additional stipulations to their power ratings such as altitude which will lower advertised ratings. There is also the factor that not all turbochargers are alike. Some may loose more power at higher elevations than others depending on their efficiency map. I know Cummins made the HE351VE on the small side specifically to work well in high elevations which reduces max power allowed and is a big restriction for someone at sea level like me, but it is a huge plus for those at live at higher altitude because it is not so laggy and you don't loose as much power. I don't know enough about the PSD or DMAX turbos to comment on them.FishOnOne wrote:
How could a lower compression engine make the same fuel economy?
By increasing fuel pressure. Higher fuel pressure means greater atomization of fuel for a better/cleaner burn to get more out of each drop of fuel. Basically smaller droplets under pressure will mix with the air better. It also allows you to inject more fuel withing a given amount of time for more power. You are only given a certain amount of time to inject fuel and the higher the pressure you have, the more an open injector can inject within that window. This is why increasing fuel pressure will generally allow you to increase power in a diesel.
That's why I said the Duramax torque maybe understated.
As for the high fuel pressure I agree it helps with reducing emissions so HP can be increased, but you said that higher compression ratio increases an engines efficiency which makes perfect sense. I'm wondering if the reduced compression ratio is more about improving emissions while supporting more HP, at the expense of efficiency.
Maybe these new engines need some more break in time... Time will tell!
Having said that I do recall TFL fuel economy tests have a Power Stroke, Duramax, and a Cummins at one time or another perform the best.RCMAN46 wrote:
The gear ratios you used are for the GM 10L80.
I have doubts that the GM 10L1000 will have the same ratios. I base this on the statement in one of the GM videos that you will be able to skip 1st gear when running with no load. This implies a much lower first gear than 4.70 with the 3.42 rear gear.
I have not been able to find published gear ratios for the 10L1000. I suspect they may be close to the Allison TC10.
You are correct. I want back to the GM news letter those numbers came from and it was the gasser 10 speed.FishOnOne wrote:
If this new cummins HP is understated then one can say that about the Duramax used in this test.
Not exactly. There is nothing in the rule books saying that you can report lower power numbers than the SAE test. There is, however, rules stating you cannot advertise above it. We seen this during the 90's and early 2000's when all of the Japanese car makers had a "gentlemen's agreement" not to advertise their cars over 276 hp even though many of their sports cars were making well over that. - Japan Dumps 276-hp Pact
A manufacture can add additional stipulations to their power ratings such as altitude which will lower advertised ratings. There is also the factor that not all turbochargers are alike. Some may loose more power at higher elevations than others depending on their efficiency map. I know Cummins made the HE351VE on the small side specifically to work well in high elevations which reduces max power allowed and is a big restriction for someone at sea level like me, but it is a huge plus for those at live at higher altitude because it is not so laggy and you don't loose as much power. I don't know enough about the PSD or DMAX turbos to comment on them.FishOnOne wrote:
How could a lower compression engine make the same fuel economy?
By increasing fuel pressure. Higher fuel pressure means greater atomization of fuel for a better/cleaner burn to get more out of each drop of fuel. Basically smaller droplets under pressure will mix with the air better. It also allows you to inject more fuel withing a given amount of time for more power. You are only given a certain amount of time to inject fuel and the higher the pressure you have, the more an open injector can inject within that window. This is why increasing fuel pressure will generally allow you to increase power in a diesel.ShinerBock wrote:
Torque multiplication of the Ram Aisin 6-speed w/ 4.10
1st- 3.75 x 4.10 x 1,000 lb-ft= 11,275 lb-ft
2nd- 2.00 x 4.10 x 1,000 lb-ft= 8,200 lb-ft
3rd- 1.34 x 4.10 x 1,000 lb-ft= 5,494 lb-ft
4th- 1.00 x 4.10 x 1,000 lb-ft= 4,100 lb-ft
5th- .77 x 4.10 x 1,000 lb-ft= 3,157 lb-ft
6th- .63 x 4.10 x 1,000 lb-ft= 2.583 lb-ft
1-3rd are under-drive gears, 4th is direct, and 5-6 are overdrive.
Torque multiplication of the GM Allison 10-speed w/3.42
1st- 4.70 x 3.42 x 910= 14,627 lb-ft
2nd- 2.99 x 3.42 x 910= 9,305 lb-ft
3rd- 2.15 x 3.42 x 910= 6,691 lb-ft
4th- 1.80 x 3.42 x 910= 5,602 lb-ft
5th- 1.52 x 3.42 x 910= 4,731 lb-ft
6th- 1.28 x 3.42 x 910= 3,984 lb-ft
7th- 1.00 x 3.42 x 910= 3,112 lb-ft
8th- .85 x 3.42 x 910= 2,645 lb-ft
9th- .69 x 3.42 x 910= 2,147 lb-ft
10th- .64 x 3.42 x 910= 1,992 lb-ft
1-6 are under-drive, 7th is direct, and 8-10 are overdrive.
The Duramax was winning the torque to the wheels battle even with a 3.42 and it was also winning the horsepower battle according to the manufacturers ratings.
The gear ratios you used are for the GM 10L80.
I have doubts that the GM 10L1000 will have the same ratios. I base this on the statement in one of the GM videos that you will be able to skip 1st gear when running with no load. This implies a much lower first gear than 4.70 with the 3.42 rear gear.
I have not been able to find published gear ratios for the 10L1000. I suspect they may be close to the Allison TC10.ib516 wrote:
FishOnOne wrote:
If this new cummins HP is understated then one can say that about the Duramax used in this test.
I don't follow your logic. :?
The Duramax is rated at 445 hp, the Cummins is rated at 400 hp. The Cummins had about 700# more weight and lower hp and made the same time.
IB,
I was thinking along the lines that torque on the Duramax was at a advertised less torque than the Cummins. I should have been more specific.FishOnOne wrote:
If this new cummins HP is understated then one can say that about the Duramax used in this test.
I don't follow your logic. :?
The Duramax is rated at 445 hp, the Cummins is rated at 400 hp. The Cummins had about 700# more weight and lower hp and made the same time.
