Gas vs PSD
Posting Guru
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From: emporium
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.
the entire 2nd paragraph is about torque.
a more-heavily loaded vehicle keeps the engine from spinning up as fast
put a turbo on a v10 and it is much more responsive unloaded because it can gain its rpms so much faster. but when loaded the gas motor has a harder time reaching its higher rpms without downshifting due to the lack of torque. so the turbo will be less responsive until it dowsifts. now when you dont have to downshift like in a psd the turbo is more effective do to the fact your not lossing speed from running in a lower gear.
i think that makes sense. im a little groggy. also just want to throw out there i drove my uncles hemi dodge today. what a disapointment. they should have kept there v10
Posting Guru
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From: emporium
not sure what a bad penny is. i love pennies. i put them in a jar on the shelf and whenever it fills up i go down to the bank and put them in the machine. i always walk out with a smile on my face and a wallet stuffed with cash afterwords.
Elder User
Joined: May 2010
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From: WV
Tractive force is torque to the tires but my point is that engine torque is not even a variable in the equation, so it plays no role in determining tractive force. HP and wheel rpm are the only variables. Gearing can make up for lack of engine torque. Both of my trucks are 5 speed manuals with 4.10 gears, so there is no difference there. It doesn't take much tractive force to move an empty truck, so like the others said, the turbo isn't fully spooled on the empty diesel. That also means the empty gasser runs through that 0-3,000 low HP zone pretty quickly too. The more weight you add to the gasser the longer it is going to take it to get over that hump from a dead stop. Sorry about the lack of paragraphs but I am on my phone and it won't let me use paragraphs.
as for engine torque in the equation, you could easily make it based off engine torque, it's just simple algebra. You have what hp is in terms of torque, just plug that equation in for hp and you'll have an equation with torque instead... moot point really.
The fact that it takes long to get to it's power band is plenty of explanation.
Elder User
Joined: May 2010
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From: WV
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.
So then, this is enough to compensate for the gasser's ability to hold the gears longer and create a somewhat level playing field, at least once things get rolling.
Elder User
Joined: May 2010
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From: WV
its not the turbo off the line all by its self. its the torque. the turbo is only going to respond with more rpms. when your loaded the torque is getting the truck moving faster off the line witch increases the rpms quicker. once the engine gets rolling your building your boost. hence spooling the turbo at the redlight to get the jump. your increasing your rpms and creating more exhaust. from a dead start your torque is effectivly starting the process.
the entire 2nd paragraph is about torque.
thats were torque comes into play.
put a turbo on a v10 and it is much more responsive unloaded because it can gain its rpms so much faster. but when loaded the gas motor has a harder time reaching its higher rpms without downshifting due to the lack of torque. so the turbo will be less responsive until it dowsifts. now when you dont have to downshift like in a psd the turbo is more effective do to the fact your not lossing speed from running in a lower gear.
i think that makes sense. im a little groggy. also just want to throw out there i drove my uncles hemi dodge today. what a disapointment. they should have kept there v10
the entire 2nd paragraph is about torque.
thats were torque comes into play.
put a turbo on a v10 and it is much more responsive unloaded because it can gain its rpms so much faster. but when loaded the gas motor has a harder time reaching its higher rpms without downshifting due to the lack of torque. so the turbo will be less responsive until it dowsifts. now when you dont have to downshift like in a psd the turbo is more effective do to the fact your not lossing speed from running in a lower gear.
i think that makes sense. im a little groggy. also just want to throw out there i drove my uncles hemi dodge today. what a disapointment. they should have kept there v10
When the truck is loaded down, the RPM's don't build as fast allowing the boost to come up to a max at each RPM.
Is that more or less what you are saying?
Posting Guru
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From: emporium
I think what they are saying is with an empty truck, the turbo is always playing catchup. The RPM's are building faster than the max spool or boost is.
When the truck is loaded down, the RPM's don't build as fast allowing the boost to come up to a max at each RPM.
Is that more or less what you are saying?
When the truck is loaded down, the RPM's don't build as fast allowing the boost to come up to a max at each RPM.
Is that more or less what you are saying?
yes sir
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From: Long Island USA
I think what they are saying is with an empty truck, the turbo is always playing catchup. The RPM's are building faster than the max spool or boost is.
When the truck is loaded down, the RPM's don't build as fast allowing the boost to come up to a max at each RPM.
Is that more or less what you are saying?
When the truck is loaded down, the RPM's don't build as fast allowing the boost to come up to a max at each RPM.
Is that more or less what you are saying?
That thing could get loaded to the gills, to a point, and still accelerate almost the exact same way. The only way to figure that is the turbo was coming up and giving that extra boost. In the lower gears, the engine's crankshaft/flywheel is so heavy that it can only rev up so fast anyway, but once you hit the higher gears, the turbo starts to get it's act together and really apply the boost.
And that's with a purely mechanical direct-injection setup with a manual tranny. No magic possible from the PCM because their ain't one
Posting Guru
Joined: Aug 2008
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From: Sunny, Snowy, CO
Nope...I'm telling you, up here, your V10's are quite s-l-o-w...Besides, all I have to do is spool mine up and I'll eat you off the light too.
Postmaster
Joined: Apr 2006
Posts: 3,524
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From: CA Bay Area
EXACTLY! I used to drive an Isuzu NPR (joint GM/Isuzu developed engine, I believe), which was a totally mechanical injection 4-cylinder w/turbo.
That thing could get loaded to the gills, to a point, and still accelerate almost the exact same way. The only way to figure that is the turbo was coming up and giving that extra boost. In the lower gears, the engine's crankshaft/flywheel is so heavy that it can only rev up so fast anyway, but once you hit the higher gears, the turbo starts to get it's act together and really apply the boost.
And that's with a purely mechanical direct-injection setup with a manual tranny. No magic possible from the PCM because their ain't one
That thing could get loaded to the gills, to a point, and still accelerate almost the exact same way. The only way to figure that is the turbo was coming up and giving that extra boost. In the lower gears, the engine's crankshaft/flywheel is so heavy that it can only rev up so fast anyway, but once you hit the higher gears, the turbo starts to get it's act together and really apply the boost.
And that's with a purely mechanical direct-injection setup with a manual tranny. No magic possible from the PCM because their ain't one
I posted the pictures before, what is about 10 years old technology used on 200+ HP Mercedes engine. The turbo is fully adjustable
Than the 200,000 rpm turbo is very small and very light >>> meaning no noticeable turbo lag. Here is the look at compressor wheel comparing to a quarter.
Elder User
Joined: May 2010
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From: WV
Than we are diverting the topic to other engines again.
I posted the pictures before, what is about 10 years old technology used on 200+ HP Mercedes engine. The turbo is fully adjustable
Than the 200,000 rpm turbo is very small and very light >>> meaning no noticeable turbo lag. Here is the look at compressor wheel comparing to a quarter.
I posted the pictures before, what is about 10 years old technology used on 200+ HP Mercedes engine. The turbo is fully adjustable
Than the 200,000 rpm turbo is very small and very light >>> meaning no noticeable turbo lag. Here is the look at compressor wheel comparing to a quarter.
200,000 RPM? We use turbo molecular pumps that spin at 90,000 RPM for some of our high vacuum applications. Those blades have to be at 1x10^-3 torr before they come on, other wise they will shatter from the amount of air. We had one system depressurize on us and go to atmospheric pressure before the turbo pump could slow down, it shattered the blades and cost $15k to replace.
The cost of the parts to be able to hold such a high RPM must be insane on that turbo.
Postmaster
Joined: Apr 2008
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From: Rogersville, TN
ahh.. I knew both your trucks had 4.10, just for some reason thought your 7.3 had an auto...
as for engine torque in the equation, you could easily make it based off engine torque, it's just simple algebra. You have what hp is in terms of torque, just plug that equation in for hp and you'll have an equation with torque instead... moot point really.
The fact that it takes long to get to it's power band is plenty of explanation.
as for engine torque in the equation, you could easily make it based off engine torque, it's just simple algebra. You have what hp is in terms of torque, just plug that equation in for hp and you'll have an equation with torque instead... moot point really.
The fact that it takes long to get to it's power band is plenty of explanation.
Engine torque can be part of the equation as long as you are comparing them in the same gears and at the same speed/rpm because at that point the one with more engine torque is also producing more hp. Since gearing will be the same and wheel rpm the same, the one with more engine torque(and hp) will be producing more tractive force. The reason engine torque doesn't matter in this comparison(except off the line for the first 3,000 rpm) is because of the drastic difference in gearing and rpm ranges.
Honestly, I am not too impressed with the 6.2 off the line even with the 6 speed and 4.30 gears. Comparing it to my 2v 5.4 with both in 1st gear and turning 4,500 rpm the tractive force is 6,929 for the 6.2 and 7,112 for my 5.4. The 6.7 has seen a massive increase in low end power AND gets the 6 speed tranny while the 6.2 at its best is worse off the line than a 2v 5.4 with a manual.....
Postmaster
Joined: Apr 2006
Posts: 3,524
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From: CA Bay Area
Talking about low end toque. When my Superduty with 7.3 PS blow the differential, I rented 2004 Superduty with 6.0 PS.
The newer engine with very low torque and poorly design automatic almost made me costing couple of accidents when it took 20 seconds for the set to move across intersection.
The newer engine with very low torque and poorly design automatic almost made me costing couple of accidents when it took 20 seconds for the set to move across intersection.