is 1000rpm converter slip up top normal?
04-29-2007, 07:35 PM
#1
is 1000rpm converter slip up top normal? working on a turbo 5.3L fairmont with a th400 and a precision "3200-3400" converter. i told them 600rwhp/600rwtq for the motor when precision asked all of their questions. we are a ways under that.
so far we have just run the 1/8th. we are at 5700rpm @107mph at the end of the 1/8th. looking at the rpm calculator with 26" tall tires and 3.27 gears 107mph should be 4500 with a 1:1 ratio. to me that indicates we are seeing 1200rpm slip up top. doesnt that seem like too much? we have no problem 2steping(with a tbrake) to 3600rpm and 14psi. looking at the log we only drop to 5200rpm after the 1-2 and 5300 after the 2-3 shift. thats probably past our peek power(stock 5.3, stock cam, small .68ar on turbo).
i dont know if we are going to be able to run out the 1/4 with this thing as it sits. maybe it will get tighter as the rpms go up and the power falls off?
so far we have just run the 1/8th. we are at 5700rpm @107mph at the end of the 1/8th. looking at the rpm calculator with 26" tall tires and 3.27 gears 107mph should be 4500 with a 1:1 ratio. to me that indicates we are seeing 1200rpm slip up top. doesnt that seem like too much? we have no problem 2steping(with a tbrake) to 3600rpm and 14psi. looking at the log we only drop to 5200rpm after the 1-2 and 5300 after the 2-3 shift. thats probably past our peek power(stock 5.3, stock cam, small .68ar on turbo).
i dont know if we are going to be able to run out the 1/4 with this thing as it sits. maybe it will get tighter as the rpms go up and the power falls off?
04-30-2007, 10:54 AM
#2
It could couple back up higher in the rpms. What's it look like at your shift point?
If you are shifting around 6000, you might benefit from a tighter design, but I wouldn't want it to drop below 5300 rpm at 107 mph or you will be too far from peak HP on the upshifts.
If you are shifting around 6000, you might benefit from a tighter design, but I wouldn't want it to drop below 5300 rpm at 107 mph or you will be too far from peak HP on the upshifts.
04-30-2007, 11:31 AM
#3
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Parish
Glad to see you got a new project
With that small turbo and stock cam...That engine is done making power by 6000 rpm...In fact, it's probably dropping power after 5250rpm. You could stick it out and see if the verter tightens up...MY guess it will still cost too much power up top...and you'll be seeing 6500rpms thru the traps (never see that with stock springs). We try and verter the turbo cars to around 4500-4750 extension (big mid range torque there) and go thru the traps by 6000rpm (on more stocker combos like that). If you destall that verter by 300-400 rpms your extension should drop down to 4700ish range and be way tighter upstairs...I bet your 1/8 mile trap speed will really pick up....Too bad that converter design could not hold that mid range punch of that turbo combo...Seen that too many times as these companies just can't account for that big mid range punch.
Taller rear tires are an option too...! You would still be loosing some efficiency with that too lose converter though....
Good luck with it...I like sleeper projects...
Glad to see you got a new project
With that small turbo and stock cam...That engine is done making power by 6000 rpm...In fact, it's probably dropping power after 5250rpm. You could stick it out and see if the verter tightens up...MY guess it will still cost too much power up top...and you'll be seeing 6500rpms thru the traps (never see that with stock springs). We try and verter the turbo cars to around 4500-4750 extension (big mid range torque there) and go thru the traps by 6000rpm (on more stocker combos like that). If you destall that verter by 300-400 rpms your extension should drop down to 4700ish range and be way tighter upstairs...I bet your 1/8 mile trap speed will really pick up....Too bad that converter design could not hold that mid range punch of that turbo combo...Seen that too many times as these companies just can't account for that big mid range punch.
Taller rear tires are an option too...! You would still be loosing some efficiency with that too lose converter though....
Good luck with it...I like sleeper projects...
Last edited by jimbob; 04-30-2007 at 11:40 AM.
04-30-2007, 04:19 PM
#4
right now peek hp is around 5100 and peek tq is around 4700rpm. from what i understand you look at the tq and we are well past peek tq for the entire run and falling off hard as we spin it up. we are shifting at 5700 and droping to 5200-5300 after the shift. infact the entire run we are in the 5200-5700rpm range.
we would be willing to up the rpm range of this motor a little. a higher ar and small cam like an ls6 cam would help some but i am afraid if we pushed the peek tq up to 5200rpm or so we would just end up pushing the converter up even higher and still not get to enjoy the peek tq at any point in the run.
if we send the converter back is there any chance of them hitting things so it is still loose enough to 2step and build boost while not blowing thru past peek tq?
we would be willing to up the rpm range of this motor a little. a higher ar and small cam like an ls6 cam would help some but i am afraid if we pushed the peek tq up to 5200rpm or so we would just end up pushing the converter up even higher and still not get to enjoy the peek tq at any point in the run.
if we send the converter back is there any chance of them hitting things so it is still loose enough to 2step and build boost while not blowing thru past peek tq?
04-30-2007, 11:17 PM
#5
i just looked at some of the logs. on the 7.5psi 7.46 run the shift extention was 4700rpm. the 13.5psi 6.80 run was 5000rpm. the 18psi 6.63 run was 5250. the extra power is really pushing this converter right thru the heart of the tq range. we definately need to tighten up the converter a fair amount.
has anyone ever heard of swaping some of the tranny fluid for tractor hydrolic fluid to tighten things up?
has anyone ever heard of swaping some of the tranny fluid for tractor hydrolic fluid to tighten things up?
05-01-2007, 04:57 AM
#6
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Originally Posted by parish8
i just looked at some of the logs. on the 7.5psi 7.46 run the shift extention was 4700rpm. the 13.5psi 6.80 run was 5000rpm. the 18psi 6.63 run was 5250. the extra power is really pushing this converter right thru the heart of the tq range. we definately need to tighten up the converter a fair amount.
has anyone ever heard of swaping some of the tranny fluid for tractor hydrolic fluid to tighten things up?
has anyone ever heard of swaping some of the tranny fluid for tractor hydrolic fluid to tighten things up?
05-01-2007, 09:04 AM
#7
I didn't realize that you peaked so low in the rpm band. Definitely look at tightening it up.
Different converter designs have faster drop offs, so you may be better served by designing for 18 lbs boost, rather than tinkering with your current one. The challenge you have is that peak HP and TQ are so close together. Most converters typically are designed to work over a 2000 rpm range with power peaks about 1000 - 1500 rpm apart.
I'd be a little surprised if the LS6 cam pushed peak torque up 500 rpm. You can also put it in a one or two degrees advance to account for your desired operating range and smaller cubes.
Different converter designs have faster drop offs, so you may be better served by designing for 18 lbs boost, rather than tinkering with your current one. The challenge you have is that peak HP and TQ are so close together. Most converters typically are designed to work over a 2000 rpm range with power peaks about 1000 - 1500 rpm apart.
I'd be a little surprised if the LS6 cam pushed peak torque up 500 rpm. You can also put it in a one or two degrees advance to account for your desired operating range and smaller cubes.
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05-01-2007, 04:07 PM
#8
Originally Posted by Ragtop 99
I didn't realize that you peaked so low in the rpm band. Definitely look at tightening it up.
Different converter designs have faster drop offs, so you may be better served by designing for 18 lbs boost, rather than tinkering with your current one. The challenge you have is that peak HP and TQ are so close together. Most converters typically are designed to work over a 2000 rpm range with power peaks about 1000 - 1500 rpm apart.
I'd be a little surprised if the LS6 cam pushed peak torque up 500 rpm. You can also put it in a one or two degrees advance to account for your desired operating range and smaller cubes.
Different converter designs have faster drop offs, so you may be better served by designing for 18 lbs boost, rather than tinkering with your current one. The challenge you have is that peak HP and TQ are so close together. Most converters typically are designed to work over a 2000 rpm range with power peaks about 1000 - 1500 rpm apart.
I'd be a little surprised if the LS6 cam pushed peak torque up 500 rpm. You can also put it in a one or two degrees advance to account for your desired operating range and smaller cubes.
i am prety sure i told precision were were looking at 600rwhp/600rwtq, 3000lbs and 3200-3400 stall. seems like they always come back too loose to start out. right now the dyno shows a peek of 540rwtq but who knows what the real number might be if the converter is blowing thru.
