Gas vs PSD
Laughing Gas
Joined: Jul 2010
Posts: 1,155
Likes: 31
From: Idaho
Turbo
There is a pause before the turbo starts to spin. This is the lag, once the turbo makes about 10 pounds no more lag.
When ford had dual turbo I could not detect the turbo lag. It was a great system. On the new one I can detect it.
When ford had dual turbo I could not detect the turbo lag. It was a great system. On the new one I can detect it.
Elder User
Joined: May 2010
Posts: 650
Likes: 0
From: WV
Yes I have a turbo car, I've felt the lag many times when I need to accelerate very quickly to pull out into traffic. You set and wait for the turbo to kick in like a deer in the headlights of the on coming traffic, then turbo spools and you're gone.
Apply that to what Kewart says, the diesel should be slower off the line while the turbo spools, then if both have similar power you would have similar acceleration, just the diesel would be 0.5 second (or what ever amount of time it takes to spool up) behind the N/A.
But the data shows the opposite, when loaded the diesel is the quicker of the 2. In fact Josh even stated his 7.3 will out jerk his 5.4.
Apply that to what Kewart says, the diesel should be slower off the line while the turbo spools, then if both have similar power you would have similar acceleration, just the diesel would be 0.5 second (or what ever amount of time it takes to spool up) behind the N/A.
But the data shows the opposite, when loaded the diesel is the quicker of the 2. In fact Josh even stated his 7.3 will out jerk his 5.4.
Postmaster
Joined: Apr 2008
Posts: 4,724
Likes: 4
From: Rogersville, TN
Torque moves a car/truck
Using yours and Josh's logic, if the diesel and gas trucks are evenly fast empty, they should still be evenly fast towing, right? Yet this is not the case. The extra torque from the diesel allows the truck to apply more hp through the tire to the ground as the payloads increase.
Using yours and Josh's logic, if the diesel and gas trucks are evenly fast empty, they should still be evenly fast towing, right? Yet this is not the case. The extra torque from the diesel allows the truck to apply more hp through the tire to the ground as the payloads increase.
Postmaster
Joined: Apr 2008
Posts: 4,724
Likes: 4
From: Rogersville, TN
To put this phrase in correct context, my 7.3 will out pull my 5.4 off the line if I pull out in the same gear because they will have the same wheel rpm at the same speeds and the 7.3 makes more low rpm HP, so more tractive force. My 7.3 will do 12 mph in 1st gear, so from 0-12 mph my 7.3 runs off and leaves it lol. Once it shifts to 2nd my 5.4 smokes it. So from 12 mph to top speed my 5.4 accelerates better...... That 0-12 mph makes a big difference when comparing empty/loaded 1/4 mile times, but means nothing when driving under normal circumstances.
Elder User
Joined: May 2010
Posts: 650
Likes: 0
From: WV
Engine torque only matters when both engines are turning the same rpms and going the same speed because the one with more torque is putting out more HP and being divided by the same wheel rpm, so it has more tractive force. That is why my 7.3 is so much better off the line than my 5.4 if I pull out in the same gear. Once the 7.3 shifts it is all over though and the 5.4 eats it up. That is not my logic at all. I said the diesel doesn't slow down as much because it makes better power at low rpms and doesn't struggle getting the load moving. The gasser makes much less HP(and tractive force) at low rpms and from a dead stop it takes a lot longer to get into its power band. So it will slow down more in a 1/4 mile race from a dead stop. Run them from a rolling start and you'll see much different results in how much the gasser slows down with a load.
I see your logic, but I'm still not seeing why the there is no difference between the gas and diesel empty, but a significant difference between them when towing in the comparison tests.
Elder User
Joined: May 2010
Posts: 650
Likes: 0
From: WV
To put this phrase in correct context, my 7.3 will out pull my 5.4 off the line if I pull out in the same gear because they will have the same wheel rpm at the same speeds and the 7.3 makes more low rpm HP, so more tractive force. My 7.3 will do 12 mph in 1st gear, so from 0-12 mph my 7.3 runs off and leaves it lol. Once it shifts to 2nd my 5.4 smokes it. So from 12 mph to top speed my 5.4 accelerates better...... That 0-12 mph makes a big difference when comparing empty/loaded 1/4 mile times, but means nothing when driving under normal circumstances.
The comparison tests show the diesels get a better jump basically, but then the acceleration on both truck looks similar once they hit 15 mph or so.
Postmaster
Joined: Apr 2008
Posts: 4,724
Likes: 4
From: Rogersville, TN
Exactly, which is torque to the tires, not hp at the tires.
I think in your case what you are observing is the difference between having a good manual and a bad auto. Haven't heard of anyone that loved their 4R100 yet.
I see your logic, but I'm still not seeing why the there is no difference between the gas and diesel empty, but a significant difference between them when towing in the comparison tests.
I think in your case what you are observing is the difference between having a good manual and a bad auto. Haven't heard of anyone that loved their 4R100 yet.
I see your logic, but I'm still not seeing why the there is no difference between the gas and diesel empty, but a significant difference between them when towing in the comparison tests.
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Joe Kucinski
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 422
From: Long Island USA
That's the turbo. It's hard to explain, but at any one point in time during acceleration, a more-heavily loaded vehicle keeps the engine from spinning up as fast, giving the turbo more time to come up and provide more boost.
I'm not talking about "turbo lag" where you don't get boost as soon as you smack the go-pedal. I also suspect there is more going on in the PCM in terms of which gear you are in, and how fast the engine is spooling up.
Senior User
Joined: May 2010
Posts: 288
Likes: 0
From: Oregon
Not sure of all the talkin that went on in nearly 500 pages, was just stopping by. Why compare apples to oranges and get sore about either? Both are strong motors, just very different.
Me being captain obvious:
If I could own a PSD or a V10 I would love to have either. If my 87 f250 had a 7.3 DIT (or 12v cummins, dt466
) running perfect I'd be a gitty ****
and before I get slandered for being a 'thick' diesel guy or w/e was said earlier, my other truck is a gas 61 econoline pickup...
Me being captain obvious:
- The V10 has 10 pistons to help give it torque, the v8 psd has 8 heavier pistons to make up for the short coming. the lighter the rotating mass is the easier it is to rotate it faster - momentum and inertia.
- displacement vs induction who gives a rip. the thread is a comparison so the fact is that the diesel is turbo'd and the gas has more cylinders less displacement. Can't compare and then set limits on what can be talked about. Each motor has its pro's and con's. Each is suited to a certain task well. Diesel engines usually have better fuel economy but I admittedly don't know too much about the tritons. Diesel engines can last a very long mileage but I don't know how long a triton will do.
If I could own a PSD or a V10 I would love to have either. If my 87 f250 had a 7.3 DIT (or 12v cummins, dt466
) running perfect I'd be a gitty ****and before I get slandered for being a 'thick' diesel guy or w/e was said earlier, my other truck is a gas 61 econoline pickup...
Posting Guru
Joined: Aug 2008
Posts: 2,313
Likes: 0
From: Sunny, Snowy, CO
I never said it would be slower off the line. You brought up the "phenomenon" of a diesel keeping it's acceleration more than a gasser as it loads up with more and more weight, where the gasser falls off quicker.
That's the turbo. It's hard to explain, but at any one point in time during acceleration, a more-heavily loaded vehicle keeps the engine from spinning up as fast, giving the turbo more time to come up and provide more boost.
I'm not talking about "turbo lag" where you don't get boost as soon as you smack the go-pedal. I also suspect there is more going on in the PCM in terms of which gear you are in, and how fast the engine is spooling up.
That's the turbo. It's hard to explain, but at any one point in time during acceleration, a more-heavily loaded vehicle keeps the engine from spinning up as fast, giving the turbo more time to come up and provide more boost.
I'm not talking about "turbo lag" where you don't get boost as soon as you smack the go-pedal. I also suspect there is more going on in the PCM in terms of which gear you are in, and how fast the engine is spooling up.
Has it been 3 days yet?
Fleet Mechanic
Joined: Sep 2007
Posts: 1,256
Likes: 6
From: Garden Valley, Idaho
Sorry but by the time your turbo does kick in you'll find it very hard to catch me if ever. And only if you have done some mods, otherwise it's a push even towing. Been on both ends with both engines.
Elder User
Joined: Apr 2009
Posts: 685
Likes: 0
From: Spokane, WA
Where are you located? I will pull with ya, even with my older transmission. LOL Sorry, but there is no test where a V10 has outpulled or even pulled with a psd except for one that ended up smoking.