A4: will I have to go low on my 1-2 shift MPH?
11-10-2005, 08:43 AM
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A4: will I have to go low on my 1-2 shift MPH? got HP tuners and am trying to tune my 1-2 shift so it doesnt hit the rev limiter. I currently have WOT rpm shift set at 6000rpm's I believe and the WOT shift MPH set to 34mph. stock 2.73's is something like 45mph I think. 34mph seems too low. I know i need to lead the shift and all, but I think my stall is slipping past the shift to redline. Should i keep on lowering the MPH till I dont hit the limiter anymore?
my rev limiter is set at like 6400RPMs.....
my car: 2.73 rear, Yank ST3800, ARE stage 2 heads, pulley, intake mods, exhaust.
thanks for any help guys
my rev limiter is set at like 6400RPMs.....
my car: 2.73 rear, Yank ST3800, ARE stage 2 heads, pulley, intake mods, exhaust.
thanks for any help guys
11-10-2005, 08:50 AM
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Yeah, with a converter that's kind of an unknown
quantity (depending on engine output as well as
just different) you have to "back into it". Also may
need to adjust the RPM as the converter will let
you run up faster (rotating mass) in RPM as well
as RPM leading MPH by the slip.
You might want to push WOT RPM down lower
and work on a MPH-only basis, then blend that
MPH back into the part throttle tables as well
for a "seamless" shift-vs-pedal profile.
quantity (depending on engine output as well as
just different) you have to "back into it". Also may
need to adjust the RPM as the converter will let
you run up faster (rotating mass) in RPM as well
as RPM leading MPH by the slip.
You might want to push WOT RPM down lower
and work on a MPH-only basis, then blend that
MPH back into the part throttle tables as well
for a "seamless" shift-vs-pedal profile.
11-10-2005, 09:10 AM
#4
You need to first log the input and output shaft rpms to figure out what % loss you have, that will help to let you know if your converter is the culprit. Also log the "current gear". By comparing the difference from the input vs. the output, you will be able to see if your shift RPM or MPH is correct ... leading to another culprit. Too much pressure can simulate this problem as well. You need to look at your pressure tables as well. You may need to lower some areas on those tables to avoid pressure blow by in the transmission, this effectively causes the pressure to be to high to allow shifts (in some cases).
11-10-2005, 09:17 AM
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Originally Posted by Flame Throwing SS
You need to first log the input and output shaft rpms to figure out what % loss you have, that will help to let you know if your converter is the culprit. Also log the "current gear". By comparing the difference from the input vs. the output, you will be able to see if your shift RPM or MPH is correct ... leading to another culprit. Too much pressure can simulate this problem as well. You need to look at your pressure tables as well. You may need to lower some areas on those tables to avoid pressure blow by in the transmission, this effectively causes the pressure to be to high to allow shifts (in some cases).
so the only thing that would be important is the WOT input/output shaft difference? how can i make sure my tranny is in a 1:1 gear to calculate my %eff?
my max line pressure is 90%, and for base shift firmness I have it progressive just a little higher than stock (I believe I mimicked your second table that you posted on the HPT forum on your '01 SS I think) the pressure feels good and it's not hitting the rev limiter any different than when I had left it at stock settings. it's barely tagging the limiter
11-10-2005, 09:25 AM
#6
You don't need to be in 3rd gear (1:1) to calculate %loss. Actually, I would suggest you check it in the gear that is tagging the limiter, 1->2. With a higher STR, a converter at lower gear ratios tends to cause the trans to "slip" more (as viewed with input and output). So it sounds as though you do not have a pressure issue, that is good. 
11-10-2005, 10:46 AM
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whats the general formula to calculate % converter efficiency?
only thing i found was [(engine speed - TCC slip speed) / engine speed ] x 100 = eff
only thing i found was [(engine speed - TCC slip speed) / engine speed ] x 100 = eff
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11-10-2005, 11:14 AM
#8
Edit: Corrected variables
Log Engine RPM [SAE] and Trans Input Shaft RPM, then divide the Input RPM by the Engine RPM and that gives you a percentage which is the amount of "actual" slip the converter has. Compare the values as you accelerate through the power band, lower in the power band (RPMs) should yeild higher loss.
That formula you posted I have no idea about, that is propbably for the TCC slip error, not the efficiency of the converter.
Log Engine RPM [SAE] and Trans Input Shaft RPM, then divide the Input RPM by the Engine RPM and that gives you a percentage which is the amount of "actual" slip the converter has. Compare the values as you accelerate through the power band, lower in the power band (RPMs) should yeild higher loss.
That formula you posted I have no idea about, that is propbably for the TCC slip error, not the efficiency of the converter.
Last edited by Flame Throwing SS; 11-10-2005 at 11:51 AM.
11-10-2005, 11:34 AM
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I believe that once past the stall speed you have
zero torque multiplication (or rather, 1.000) and
the shaft speed ratio is the efficiency (when 1:1).
That's how I've been looking at various converter
efficiencies, anyway - using that assumption. If
you graph on that basis you get a reasonable-
appearing "dyno curve" of efficiency vs input RPM.
In other gears you'd want to factor it something
like (outputSpeed*ratio)/inputSpeed.
zero torque multiplication (or rather, 1.000) and
the shaft speed ratio is the efficiency (when 1:1).
That's how I've been looking at various converter
efficiencies, anyway - using that assumption. If
you graph on that basis you get a reasonable-
appearing "dyno curve" of efficiency vs input RPM.
In other gears you'd want to factor it something
like (outputSpeed*ratio)/inputSpeed.
11-10-2005, 11:57 AM
#10
Whoops, I just looked back at my notes and I corrected the variables needed to be logged. Here is a quote from my findings.
... The first image shows the flash stall speed of the converter. By looking at the Engine RPM (SAE) it is a 3200 converter. You can easily see the Engine RPM in the graph “waiting” for the Trans Input Shaft to catch up, displaying the converter stall speed. This would normally not be visible if you were looking at the tachometer, as it occurs in a fraction of a second.
The next image shows the data from the top of first gear to demonstrate the efficiency of the converter. By comparing the Engine RPM (SAE) and the Trans Input Shaft RPM we get an efficiency percentage of 97%. The efficiency pretty much stays right around the 96-97% range in the other gears...
The next image shows the data from the top of first gear to demonstrate the efficiency of the converter. By comparing the Engine RPM (SAE) and the Trans Input Shaft RPM we get an efficiency percentage of 97%. The efficiency pretty much stays right around the 96-97% range in the other gears...
