WHy are Duramax trucks so fast at the track????
03-02-2008, 10:04 PM
#17
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Both the cummins and dmax are purpose built engines. You would never want to spin a cummins at 5,500 rpm like the dmax can. However the dmax will never have the low end towing grunt that we all love around here.
The dmax is just like any gasser engine where yes you can make it fast but no it won't come that way from the factory and you'll have to put allot of $$ in it to even stand close to the strengh of the cummins stock.
The dmax is just like any gasser engine where yes you can make it fast but no it won't come that way from the factory and you'll have to put allot of $$ in it to even stand close to the strengh of the cummins stock.
03-03-2008, 11:02 AM
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03-03-2008, 04:08 PM
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I don't buy the rpm thing. The redline (3250rpm on dmax) and torque are similar to the cummins. I think it's partly a weight thing but mostly the way the 6 speed auto puts the power down. With the same mods (exhaust, intake and 120hp tune on dmax, 130 on cummins) my old 2006 dmax was about .65-.7 seconds faster in the 1/8 mile. Both trucks were crew cab 4x4's.
03-04-2008, 08:02 AM
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I don't buy the rpm thing. The redline (3250rpm on dmax) and torque are similar to the cummins. I think it's partly a weight thing but mostly the way the 6 speed auto puts the power down. With the same mods (exhaust, intake and 120hp tune on dmax, 130 on cummins) my old 2006 dmax was about .65-.7 seconds faster in the 1/8 mile. Both trucks were crew cab 4x4's.
03-04-2008, 08:12 AM
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look again, thats the un-fueled redline when you are coming down a long hill with a heavy trailer using the allison's grade braking, if you floor it in park or hold it in 1st gear (for example) and floor it the engine cuts off fuel at 3250
ben
ben
03-04-2008, 09:39 AM
#24
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The lbz will actually run to 4800 but, as was already stated above, only when coasting unfueled. I have heard that guys do raise the limiter and spin them real fast without any modifications, I don't think I'd do it though.
03-04-2008, 10:22 AM
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Them trannys make a duramax fast. Torque multiplication is what they have over a cummins dodge. They have like 3.20-3.60 first gear ratios compared to Dodges 2.45? That is a HUGE advantage. Put an Ally behind your Cummins and watch out.
03-04-2008, 03:37 PM
#26
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The allison flat out stinks as a race trans. Gear ratios are all wrong. Diesels make so much torque down low that the allison's super low first gear is worthless when you do a boosted 4wd launch. You blow through it in less than a second, then the trans has to fumble around aimlessly and collect itself, then shift to second, then lock the converter. All of this has to happen in about 2-3 seconds because the allison's gear ratios are not evenly spaced like the 48re's. Being clutch to clutch with no "overrunning" parts compounds the complication factor. Clutch-to-clutch is anything but ideal for an all-out lighting fast shifting race trans.
And when you are racing, all the while the TCM is trying to coordinate defuel, handoff clutchpacks within milliseconds, try to avoid tie-ups etc... The fact that the TCM can handle shifting a clutch to clutch auto trans under the conditions we put it through is pretty impressive; the allison programming and algorithms in that little box are amazingly complex and advanced. PCS and other guys have been working on aftermarket standalone allison TCM's for YEARS and they still cant figure it out. It is just that difficult a trans to control, let alone while racing under huge hp.
Tie-ups (when more than two clutchpacks are applied at one instant, basically trying to be in 2 gears at once) are such a huge issue with the allison under big power. TO shift big power without burning clutches, you have to shift FAST. But shifting fast on an allison increases the risk of getting a tie up. Darned if ya do darned if ya dont. All built allisons with guys that run big hp have minor tie ups under WOT. 3-4 is a tricky shift and if any of you have ridden in a built allison truck, you'll know what I mean. 3-4 bangs much harder than the other gears and sometimes does a "double shift bang jerk" feel too. When this happends it puts huge stress on the hard parts. The only reason built tranny's can survive these unavoidable "minor" tie-ups under big hp and racing are because the stock hard parts are so massive. If the allison had 47/48re hard parts it would probably grenade with an 80hp tow tune.
Billet hard parts for the allison arent really an answer because you STILL have those potential tie-ups. SO great you put in a billet input and you get a tie-up when racing....so instead of breaking the input you then strip the slines in the C1/C2 drum....so ok lets make a billet drum...then you race again and get another random tie up...then you just break the next part down the line.
First gear is so useless that now with the ability to tune the TCM with EFILive, a lot of guys are deleting 1st gear altogether (only when racing at the track tho, its not advisable for street driving). They launch in second gear and go from there.
"Dirtymax" that dmax that runs 8's or whatever runs an allison, but the ONLY reason it works is because the truck is not a full bodied (lightweight), and they only use 2nd 4th and 5th gear, (I think thats what they use, its only 3 gears of the 5) because 1st and 3rd arent spaced correctly in regard to the other gears when the trans is used for 1/4 mile racing.
Thats why one of the fasted full bodied 4x4 dmax's (buck and jess spruill) swapped out the allison for a 47re. They kept blowing up allisons because you cant make a clutch-to-clutch trans shift that fast. They also dropped something rediculous like .2 of a second off their et because the 47/48re gear ratios are perfect for racing, and you can slam one gear right onto one another without defuel or tie ups or anything.
Trust me, for all out drag racing, dodge guys have a huge upper hand. That being said though, Ive driven many stock CTD/auto's and no offence, but in my oppinion they are some of the most un-coordinated awkward automatic's Ive driven. Towing and daily driving with one would drive me nuts. Just when that awesome low end grunt of the cummins kicks in, the 47/48re ruins the fun and downshifts or unlocks the converter or something dumb. I have never driven a completely built dodge auto though, so maybe its just a stock thing.
Some day LONG time down the road I think it would be kinda fun to buy a beat up 12v with a body thats falling apart, and bomb the heck out of it, but ONLY if its a manual. And on the opposite end, Id NEVER want a manual dmax. Wrong torque curve and I just think driving a manual ctd would just be so mcuh more fun.
All out racing tranny: dodge, by a mile hands down.
Daily driving/towing/occasional weekend racer tranny: allison
Each has its advantages and disadvantages
Just my own dumb oppinons!!!
ben
03-04-2008, 04:11 PM
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I'm pretty sure one of the biggest (and simplest) factors why the Duramax is "faster" is because of it's lower weight and 2 extra cylinders. Each piston, rod, etc. weighs less and has less distance to travel. The power is also distributed among 8 cylinders instead of six. Imagine we had a 4 cylinder 5.9L engine. Each cylinder would be 1.5L and each would take a lot longer to get moving & make one revolution than an 8 cylinder 5.9L (theoretically). Finally, the Duramax is a well engineered engine for its configuration. Everything works together well and was designed for street driver friendliness.
03-04-2008, 07:15 PM
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NO ITS NOT!!!!
The allison flat out stinks as a race trans. Gear ratios are all wrong. Diesels make so much torque down low that the allison's super low first gear is worthless when you do a boosted 4wd launch. You blow through it in less than a second, then the trans has to fumble around aimlessly and collect itself, then shift to second, then lock the converter. All of this has to happen in about 2-3 seconds because the allison's gear ratios are not evenly spaced like the 48re's. Being clutch to clutch with no "overrunning" parts compounds the complication factor. Clutch-to-clutch is anything but ideal for an all-out lighting fast shifting race trans.
And when you are racing, all the while the TCM is trying to coordinate defuel, handoff clutchpacks within milliseconds, try to avoid tie-ups etc... The fact that the TCM can handle shifting a clutch to clutch auto trans under the conditions we put it through is pretty impressive; the allison programming and algorithms in that little box are amazingly complex and advanced. PCS and other guys have been working on aftermarket standalone allison TCM's for YEARS and they still cant figure it out. It is just that difficult a trans to control, let alone while racing under huge hp.
Tie-ups (when more than two clutchpacks are applied at one instant, basically trying to be in 2 gears at once) are such a huge issue with the allison under big power. TO shift big power without burning clutches, you have to shift FAST. But shifting fast on an allison increases the risk of getting a tie up. Darned if ya do darned if ya dont. All built allisons with guys that run big hp have minor tie ups under WOT. 3-4 is a tricky shift and if any of you have ridden in a built allison truck, you'll know what I mean. 3-4 bangs much harder than the other gears and sometimes does a "double shift bang jerk" feel too. When this happends it puts huge stress on the hard parts. The only reason built tranny's can survive these unavoidable "minor" tie-ups under big hp and racing are because the stock hard parts are so massive. If the allison had 47/48re hard parts it would probably grenade with an 80hp tow tune.
Billet hard parts for the allison arent really an answer because you STILL have those potential tie-ups. SO great you put in a billet input and you get a tie-up when racing....so instead of breaking the input you then strip the slines in the C1/C2 drum....so ok lets make a billet drum...then you race again and get another random tie up...then you just break the next part down the line.
First gear is so useless that now with the ability to tune the TCM with EFILive, a lot of guys are deleting 1st gear altogether (only when racing at the track tho, its not advisable for street driving). They launch in second gear and go from there.
"Dirtymax" that dmax that runs 8's or whatever runs an allison, but the ONLY reason it works is because the truck is not a full bodied (lightweight), and they only use 2nd 4th and 5th gear, (I think thats what they use, its only 3 gears of the 5) because 1st and 3rd arent spaced correctly in regard to the other gears when the trans is used for 1/4 mile racing.
Thats why one of the fasted full bodied 4x4 dmax's (buck and jess spruill) swapped out the allison for a 47re. They kept blowing up allisons because you cant make a clutch-to-clutch trans shift that fast. They also dropped something rediculous like .2 of a second off their et because the 47/48re gear ratios are perfect for racing, and you can slam one gear right onto one another without defuel or tie ups or anything.
Trust me, for all out drag racing, dodge guys have a huge upper hand. That being said though, Ive driven many stock CTD/auto's and no offence, but in my oppinion they are some of the most un-coordinated awkward automatic's Ive driven. Towing and daily driving with one would drive me nuts. Just when that awesome low end grunt of the cummins kicks in, the 47/48re ruins the fun and downshifts or unlocks the converter or something dumb. I have never driven a completely built dodge auto though, so maybe its just a stock thing.
Some day LONG time down the road I think it would be kinda fun to buy a beat up 12v with a body thats falling apart, and bomb the heck out of it, but ONLY if its a manual. And on the opposite end, Id NEVER want a manual dmax. Wrong torque curve and I just think driving a manual ctd would just be so mcuh more fun.
All out racing tranny: dodge, by a mile hands down.
Daily driving/towing/occasional weekend racer tranny: allison
Each has its advantages and disadvantages
Just my own dumb oppinons!!!
ben
The allison flat out stinks as a race trans. Gear ratios are all wrong. Diesels make so much torque down low that the allison's super low first gear is worthless when you do a boosted 4wd launch. You blow through it in less than a second, then the trans has to fumble around aimlessly and collect itself, then shift to second, then lock the converter. All of this has to happen in about 2-3 seconds because the allison's gear ratios are not evenly spaced like the 48re's. Being clutch to clutch with no "overrunning" parts compounds the complication factor. Clutch-to-clutch is anything but ideal for an all-out lighting fast shifting race trans.
And when you are racing, all the while the TCM is trying to coordinate defuel, handoff clutchpacks within milliseconds, try to avoid tie-ups etc... The fact that the TCM can handle shifting a clutch to clutch auto trans under the conditions we put it through is pretty impressive; the allison programming and algorithms in that little box are amazingly complex and advanced. PCS and other guys have been working on aftermarket standalone allison TCM's for YEARS and they still cant figure it out. It is just that difficult a trans to control, let alone while racing under huge hp.
Tie-ups (when more than two clutchpacks are applied at one instant, basically trying to be in 2 gears at once) are such a huge issue with the allison under big power. TO shift big power without burning clutches, you have to shift FAST. But shifting fast on an allison increases the risk of getting a tie up. Darned if ya do darned if ya dont. All built allisons with guys that run big hp have minor tie ups under WOT. 3-4 is a tricky shift and if any of you have ridden in a built allison truck, you'll know what I mean. 3-4 bangs much harder than the other gears and sometimes does a "double shift bang jerk" feel too. When this happends it puts huge stress on the hard parts. The only reason built tranny's can survive these unavoidable "minor" tie-ups under big hp and racing are because the stock hard parts are so massive. If the allison had 47/48re hard parts it would probably grenade with an 80hp tow tune.
Billet hard parts for the allison arent really an answer because you STILL have those potential tie-ups. SO great you put in a billet input and you get a tie-up when racing....so instead of breaking the input you then strip the slines in the C1/C2 drum....so ok lets make a billet drum...then you race again and get another random tie up...then you just break the next part down the line.
First gear is so useless that now with the ability to tune the TCM with EFILive, a lot of guys are deleting 1st gear altogether (only when racing at the track tho, its not advisable for street driving). They launch in second gear and go from there.
"Dirtymax" that dmax that runs 8's or whatever runs an allison, but the ONLY reason it works is because the truck is not a full bodied (lightweight), and they only use 2nd 4th and 5th gear, (I think thats what they use, its only 3 gears of the 5) because 1st and 3rd arent spaced correctly in regard to the other gears when the trans is used for 1/4 mile racing.
Thats why one of the fasted full bodied 4x4 dmax's (buck and jess spruill) swapped out the allison for a 47re. They kept blowing up allisons because you cant make a clutch-to-clutch trans shift that fast. They also dropped something rediculous like .2 of a second off their et because the 47/48re gear ratios are perfect for racing, and you can slam one gear right onto one another without defuel or tie ups or anything.
Trust me, for all out drag racing, dodge guys have a huge upper hand. That being said though, Ive driven many stock CTD/auto's and no offence, but in my oppinion they are some of the most un-coordinated awkward automatic's Ive driven. Towing and daily driving with one would drive me nuts. Just when that awesome low end grunt of the cummins kicks in, the 47/48re ruins the fun and downshifts or unlocks the converter or something dumb. I have never driven a completely built dodge auto though, so maybe its just a stock thing.
Some day LONG time down the road I think it would be kinda fun to buy a beat up 12v with a body thats falling apart, and bomb the heck out of it, but ONLY if its a manual. And on the opposite end, Id NEVER want a manual dmax. Wrong torque curve and I just think driving a manual ctd would just be so mcuh more fun.
All out racing tranny: dodge, by a mile hands down.
Daily driving/towing/occasional weekend racer tranny: allison
Each has its advantages and disadvantages
Just my own dumb oppinons!!!
ben
I dont ever want a D-max because I am stuck with what I have for a long time
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