How to boost torque
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Posting Guru
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From: Kent WA
How to boost torque
OK, so a buddy pointed out that your basic 350 CID chevy gasser will make as much torque as my 420 (6.9) diesel in stock form.
I've read a lot around here about how to get more HP out of the IDI motors, now my question is how can I improve the torque?
Logically the same mods that increase the HP should also increase the torque too, right? To what extent? For example, if I make intake & exhaust mods that gain me 20 HP, how much is that going to improve on the stock 318 ft/lbs of torque?
I've read a lot around here about how to get more HP out of the IDI motors, now my question is how can I improve the torque?
Logically the same mods that increase the HP should also increase the torque too, right? To what extent? For example, if I make intake & exhaust mods that gain me 20 HP, how much is that going to improve on the stock 318 ft/lbs of torque?
Posting Guru
Joined: Oct 2003
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From: Monroe, WA
What stock 350 chevy has over 318 lbs of torque? Doesn't matter anyway cuz diesel and gas numbers are kinda apples and oranges. Since these engines will never see over 5 grand it's all torque anyway.
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From: Kent WA
Originally Posted by Spectramac
What stock 350 chevy has over 318 lbs of torque? Doesn't matter anyway cuz diesel and gas numbers are kinda apples and oranges. Since these engines will never see over 5 grand it's all torque anyway.
Also, will making mods that boost HP (which peaks at 3300 RPM in stock form) also change the RPMs at which the peak torque is developed (1800 RPM in stock form IIRC)? If it changes the RPMs where the torque curve peaks, will it be at higher, or lower RPMs?
I'm glad you chimed in on this one 'cause you seem to be one of our very knowledgeable experts around here (one of many I might add).
Mountain Pass
Joined: Jul 2006
Posts: 100
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From: 6 feet under
Originally Posted by CheaperJeeper
Ok, all true. BUT, I'm still wondering how much will the HP improvement mods help torque? For every 1 addtional HP, do I get 1.5 ft/lbs increase? 2 ft/lbs? More? Less?
Also, will making mods that boost HP (which peaks at 3300 RPM in stock form) also change the RPMs at which the peak torque is developed (1800 RPM in stock form IIRC)? If it changes the RPMs where the torque curve peaks, will it be at higher, or lower RPMs?
I'm glad you chimed in on this one 'cause you seem to be one of our very knowledgeable experts around here (one of many I might add).
Also, will making mods that boost HP (which peaks at 3300 RPM in stock form) also change the RPMs at which the peak torque is developed (1800 RPM in stock form IIRC)? If it changes the RPMs where the torque curve peaks, will it be at higher, or lower RPMs?
I'm glad you chimed in on this one 'cause you seem to be one of our very knowledgeable experts around here (one of many I might add).
Don't get hung up trying to hit a number, just make improvements that make sense and you will be happy. The numbers arn't everything, and in a diesel, they are misleading.
Fleet Mechanic
Joined: Sep 2005
Posts: 1,509
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From: Ladner, British Columbia
When Ford started putting the factory turbos on the 7.3l motors in 1993 the rated horsepower gain from the N/A 7.3l was only 5 hp (i.e. 190 vs. 185)
Ford could have achieved the 5 Hp gain by turning up the fuel on the IP a little; however they could not have attained the 15% greater torque the turbo motor puts out by turning up the fuel, you need the turbo for that.
In regards to performance mods you can do on a 6.9l or a 7.3l to gain torque, as well as hp the by far best mod you can do is install a turbo charger.
Increase turbo boost to 20 psig, add and aftercooler and now you really have an engine that will curl your driveshaft and splatter your tranny all over the highway.
Seb...
Ford could have achieved the 5 Hp gain by turning up the fuel on the IP a little; however they could not have attained the 15% greater torque the turbo motor puts out by turning up the fuel, you need the turbo for that.
In regards to performance mods you can do on a 6.9l or a 7.3l to gain torque, as well as hp the by far best mod you can do is install a turbo charger.
Increase turbo boost to 20 psig, add and aftercooler and now you really have an engine that will curl your driveshaft and splatter your tranny all over the highway.
Seb...
Posting Guru
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From: Monroe, WA
Originally Posted by BLACK 6
Don't get hung up trying to hit a number, just make improvements that make sense and you will be happy. The numbers arn't everything, and in a diesel, they are misleading.
Just to give you some ammo, my old 6.9 is really tired (almost 200k). You think a little 350 chevy could beat me going over the pass with a 12 foot wood camper and boat behind it? You've seen the pic. It gets around 12 mpg doing it too! Sure, a hungry 454 could pass me getting around 6.
Last edited by Spectramac; Sep 21, 2006 at 01:59 PM.
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From: Kent WA
Understood, Black 6....
I'm not looking for hard, fast, numbers - just estimates.
Above all I want to make sure that mods to gain HP aren't going to decrease torque or throw the torque curve out of whack.
These questions are based on my experience with gassers where something as simple as opening up the exhaust on some motors will boost HP, but will actually decrease torque output AND move the torque peak significantly up the RPM range. The Jeep 4.0 liter I-6 being one very good example.
Don't want to do something like that to my truck (or my Jeep either for that matter). I'm new to diesels - this is my first one and I've had it about 3 weeks - so I have lots of questions to ask in considering the mods I do....
I'm not looking for hard, fast, numbers - just estimates.
Above all I want to make sure that mods to gain HP aren't going to decrease torque or throw the torque curve out of whack.
These questions are based on my experience with gassers where something as simple as opening up the exhaust on some motors will boost HP, but will actually decrease torque output AND move the torque peak significantly up the RPM range. The Jeep 4.0 liter I-6 being one very good example.
Don't want to do something like that to my truck (or my Jeep either for that matter). I'm new to diesels - this is my first one and I've had it about 3 weeks - so I have lots of questions to ask in considering the mods I do....
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From: Kent WA
Originally Posted by Hamberger
When Ford started putting the factory turbos on the 7.3l motors in 1993 the rated horsepower gain from the N/A 7.3l was only 5 hp (i.e. 190 vs. 185)
Ford could have achieved the 5 Hp gain by turning up the fuel on the IP a little; however they could not have attained the 15% greater torque the turbo motor puts out by turning up the fuel, you need the turbo for that.
In regards to performance mods you can do on a 6.9l or a 7.3l to gain torque, as well as hp the by far best mod you can do is install a turbo charger.
Increase turbo boost to 20 psig, add and aftercooler and now you really have an engine that will curl your driveshaft and splatter your tranny all over the highway.
Seb...
Ford could have achieved the 5 Hp gain by turning up the fuel on the IP a little; however they could not have attained the 15% greater torque the turbo motor puts out by turning up the fuel, you need the turbo for that.
In regards to performance mods you can do on a 6.9l or a 7.3l to gain torque, as well as hp the by far best mod you can do is install a turbo charger.
Increase turbo boost to 20 psig, add and aftercooler and now you really have an engine that will curl your driveshaft and splatter your tranny all over the highway.
Seb...
Originally Posted by Spectramac
I agree 100%. Any improvements you make should affect the engine across the board, so get busy!
and you guys on the board here have been a HUGE help so far!
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
I have a dyno sheet that came with one of my reman 7.3 turbo engines.
223 HP and 423 ft lbs of torque running 7 PSI of boost and reman stock fueling rate.
The 6.9 turbo I just built is running 20 PSI boost and heavier fueling rates.
This engine would eat that 7.3 for breakfast.
I only judge my engines when I have 6 or 7 tons hooked to the back of my truck.
223 HP and 423 ft lbs of torque running 7 PSI of boost and reman stock fueling rate.
The 6.9 turbo I just built is running 20 PSI boost and heavier fueling rates.
This engine would eat that 7.3 for breakfast.
I only judge my engines when I have 6 or 7 tons hooked to the back of my truck.
Hotshot
Joined: Feb 2004
Posts: 11,697
Likes: 3
From: Marengo, Iowa
Yep, hook them to a pulling sled and see who gets further... there is a very good reason the diesels don't pull against the gassers... Another thing to think about on the diesel vs gas debate in regards to torque is the fact that diesels have a longer stroke, which is also part of why they are better in the low end torque.