Dynoed w/ PT4400...What happened?
01-02-2004, 07:36 PM
#1
Dynoed w/ PT4400...What happened? A few weeks ago I replaced my Midwest 3500 (POS) w/ a used PT4400. Now before I go on, I know dyno numbers mean nothing and track numbers are key, but I'm just looking for an explanation.
With the Midwest I put down 404rwhp and 424 ft/lbs back in July. Today, I put down 375rwhp and we couldn't get an accurate torque reading because going WOT anywhere below 5k ran it to the limiter quick (tranny slipping more than likely). I did gain about 15rwhp in the mid range but at about 5200 my curve leveled off and it was flat as a board to 6500. Now I know these converters really shine in the mid range and aren't very efficient up top, but I was surprised I lost 30rwhp. A:F was about the same, timing was the same, nothing really changed except the converter. Now I've seen a few PT series dyno graphs and they all seem to do the same thing (flatline).
This makes me think either this converter is very unefficient or the Midwest was very efficient and didn't really do its job "converting torque". Considering my best 60' ever w/ the Midwest was a 1.81, I think the latter might be very true. The Midwest seems to be close to a stock converter in alot of ways. I'm not worrying too much about this because my car is definitely stronger now, just looking for some comments.
With the Midwest I put down 404rwhp and 424 ft/lbs back in July. Today, I put down 375rwhp and we couldn't get an accurate torque reading because going WOT anywhere below 5k ran it to the limiter quick (tranny slipping more than likely). I did gain about 15rwhp in the mid range but at about 5200 my curve leveled off and it was flat as a board to 6500. Now I know these converters really shine in the mid range and aren't very efficient up top, but I was surprised I lost 30rwhp. A:F was about the same, timing was the same, nothing really changed except the converter. Now I've seen a few PT series dyno graphs and they all seem to do the same thing (flatline).
This makes me think either this converter is very unefficient or the Midwest was very efficient and didn't really do its job "converting torque". Considering my best 60' ever w/ the Midwest was a 1.81, I think the latter might be very true. The Midwest seems to be close to a stock converter in alot of ways. I'm not worrying too much about this because my car is definitely stronger now, just looking for some comments.
01-02-2004, 07:41 PM
#2
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Don't assume that a PT4400 isn't efficient up top just because it has a high stall speed. That's NOT the case at all. My PT4600 lost only 10 RWHP on the dyno unlocked as opposed to locked. Heck, a STOCK converter losses 6.
I think your tranny is slipping or you have other issues now. That converter should have picked up over the Midwest at any place on the chart.
I think your tranny is slipping or you have other issues now. That converter should have picked up over the Midwest at any place on the chart.
01-02-2004, 08:35 PM
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Have you been having transmission problems to make you think it is now slipping?
What gears are you running?
More than likely (Unless your transmission has a problem) the reason you were hitting the rev limiter is because the PT4400 with its high stall will allow the motor to spin up faster than before. Also the dyno does not load the drive train as much as driving on the street. Does it hit the limiter on the street or track or just on the dyno?
When I first went with the PT4400 I had to lower my shift points by a 200 rpm to keep from hitting the limiter. Just recently I put a vig3200 back in the car and I had to raise the shift points to get it to shift at the same point as before with the PT4400.
From what I have seen the PT4400 (mine) is not very efficient below 5500 rpm. Mine did not approach 90% efficiency in 1st gear (with 3.23 gears) until 6200 rpm.
John
What gears are you running?
More than likely (Unless your transmission has a problem) the reason you were hitting the rev limiter is because the PT4400 with its high stall will allow the motor to spin up faster than before. Also the dyno does not load the drive train as much as driving on the street. Does it hit the limiter on the street or track or just on the dyno?
When I first went with the PT4400 I had to lower my shift points by a 200 rpm to keep from hitting the limiter. Just recently I put a vig3200 back in the car and I had to raise the shift points to get it to shift at the same point as before with the PT4400.
From what I have seen the PT4400 (mine) is not very efficient below 5500 rpm. Mine did not approach 90% efficiency in 1st gear (with 3.23 gears) until 6200 rpm.
John
01-02-2004, 08:59 PM
#6
I am running stock 3.23's and I haven't had any tranny problems prior to the PT4400 install besides it not locking up every once in a while. Like in your case, I was hitting the rev limiter on every shift with the PT4400, so I bumped the limiter up 200 rpm and so far so good.
The reason I assumed the tranny was slipping was because going WOT on the dyno anywhere below 5k would just instantaneously hit the limiter. Add in the fact that I've had 400rwhp behind a stock 4L60E for 6 months, and it seems the tranny might be on its way out. The biggest factor though was the simple fact that I lost 30rwhp with the PT4400.
The reason I assumed the tranny was slipping was because going WOT on the dyno anywhere below 5k would just instantaneously hit the limiter. Add in the fact that I've had 400rwhp behind a stock 4L60E for 6 months, and it seems the tranny might be on its way out. The biggest factor though was the simple fact that I lost 30rwhp with the PT4400.
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01-02-2004, 09:25 PM
#8
Originally Posted by Ragtop 99
If you had a clean pull locked and lost HP compared to an unlocked run, then the issue is elsewhere.
FWIW, my PT 4200, measured locked and unlocked on the same day was 96% efficent.
FWIW, my PT 4200, measured locked and unlocked on the same day was 96% efficent.
01-02-2004, 09:56 PM
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Originally Posted by LS1BlackZ28
So you're saying in other words if it pulled 391 locked but 404 unlocked w/ the old converter, then the tranny is probably not slipping since its 1:1 when it's locked?
I thought you were comparing unlocked to unlocked numbers.
John
01-03-2004, 12:31 PM
#10
Originally Posted by JNorris
Oops! I missed the part about the PT4400 being locked on the dyno pull.
I thought you were comparing unlocked to unlocked numbers.
John
I thought you were comparing unlocked to unlocked numbers.
John
01-03-2004, 03:15 PM
#12
TECH Senior Member
I can't imagine any properly functioning converter losing 40 RWHP unlocked. IF there were no other factors involved, then the converter was bad.
I've dynoed two 4000+ Yank stalls and both lost exactly 10 RWHP.
My TCI 3500 lost 22 RWHP.
I've witnessed a stock converter losing 6 RWHP.
I haven't dynoed my SS4000 but I bet it loses 15 or less.
"375 with the PT4400 unlocked. When we locked up the PT4400, I pulled 391."
He said his locked is 391 and his unlocked is 375. That's a lose of only 16 RWHP. Not bad at all. His engine is obviously down on power since he pulled over 400 unlocked before.
I've dynoed two 4000+ Yank stalls and both lost exactly 10 RWHP.
My TCI 3500 lost 22 RWHP.
I've witnessed a stock converter losing 6 RWHP.
I haven't dynoed my SS4000 but I bet it loses 15 or less.
"375 with the PT4400 unlocked. When we locked up the PT4400, I pulled 391."
He said his locked is 391 and his unlocked is 375. That's a lose of only 16 RWHP. Not bad at all. His engine is obviously down on power since he pulled over 400 unlocked before.
01-03-2004, 05:59 PM
#13
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Back to back dyno tests of two locked converters should very close to the same RWHP. At what RPM did you pull the 375 RWHP?
However you can be sure that an unlocked PT series converter or any other high stall converter will be much less efficient than a 3200-3500 rpm stall below 4500 rpm. There will also be a much greater difference between locked and unlocked numbers at a given RPM until the engine/converter RPM reaches the point of hydraulically coupling the both sides of the converter. Lack of efficiency is why a converter is loose.
Torque converter efficiency will be much lower on the street than on a dyno due to additional load that is not there on the dyno.
BTW the way I determine torque converter efficiency on the street is by dividing the transmission input shaft RPM by the engine RPM.
Using this method my vig3200 average efficiency is 94% in 1st gear, 87% in 2nd, and 84% in 3rd. The highest rpm in 3rd was 4200. 1st and 2nd gears were full runs of the gears.
My PT4400 average efficiency was 71% in 1st gear, 77% in 2nd, and 71% in 3rd gear. This was measured during a ¼ mile run at the track. I am running 3.23 gears. Efficiency would be better with more gear.
John
However you can be sure that an unlocked PT series converter or any other high stall converter will be much less efficient than a 3200-3500 rpm stall below 4500 rpm. There will also be a much greater difference between locked and unlocked numbers at a given RPM until the engine/converter RPM reaches the point of hydraulically coupling the both sides of the converter. Lack of efficiency is why a converter is loose.
Torque converter efficiency will be much lower on the street than on a dyno due to additional load that is not there on the dyno.
BTW the way I determine torque converter efficiency on the street is by dividing the transmission input shaft RPM by the engine RPM.
Using this method my vig3200 average efficiency is 94% in 1st gear, 87% in 2nd, and 84% in 3rd. The highest rpm in 3rd was 4200. 1st and 2nd gears were full runs of the gears.
My PT4400 average efficiency was 71% in 1st gear, 77% in 2nd, and 71% in 3rd gear. This was measured during a ¼ mile run at the track. I am running 3.23 gears. Efficiency would be better with more gear.
John
01-03-2004, 07:13 PM
#14
I'm not sure of the RPM that the 375 pull was at because the dyno was reading my RPMs wrong. It was saying that I was revving to 8500 which I'm guessing was meant to be 6500. So my entire graph was shifted 2000 RPM or so to the right. Because of this, the only way I could compare my previous 404rwhp dyno to this one was to look at the graph based on speed instead of RPM. Also, if Sean went WOT anywhere before 5000 RPM, the car would just go straight to the limiter, which is why I assumed my tranny might be slipping.
All this being said, when comparing the 2 graphs, I gained 10-15 rwhp in and around the 110 mph mark. But at around 120 or so (just guessing because I don't have the graphs w/ me) the PT4400 hp curve just flatlines and the Midwest hp curve jumps above it and peaks 30 hp higher.
So, it looks like at around 5200 the hp curve just table tops. There's no sudden jumps or anything that would symbolize a misfire or knock. Previously, my car was tuned to 13.3 a:f across the board but it was very lean this time around (14.1). So after some tuning we got it back to the 13.3 area. I guess it's a possibility that there's a fuel pressure issue up top that's not allowing it to peak. Or it might be that tranny. I'm going to change the plugs, check the fuel pressure, and go from there.
All this being said, when comparing the 2 graphs, I gained 10-15 rwhp in and around the 110 mph mark. But at around 120 or so (just guessing because I don't have the graphs w/ me) the PT4400 hp curve just flatlines and the Midwest hp curve jumps above it and peaks 30 hp higher.
So, it looks like at around 5200 the hp curve just table tops. There's no sudden jumps or anything that would symbolize a misfire or knock. Previously, my car was tuned to 13.3 a:f across the board but it was very lean this time around (14.1). So after some tuning we got it back to the 13.3 area. I guess it's a possibility that there's a fuel pressure issue up top that's not allowing it to peak. Or it might be that tranny. I'm going to change the plugs, check the fuel pressure, and go from there.
Last edited by LS1BlackZ28; 01-03-2004 at 07:44 PM.
01-05-2004, 07:54 AM
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Originally Posted by LS1BlackZ28
I'm not sure of the RPM that the 375 pull was at because the dyno was reading my RPMs wrong. It was saying that I was revving to 8500 which I'm guessing was meant to be 6500. So my entire graph was shifted 2000 RPM or so to the right. Because of this, the only way I could compare my previous 404rwhp dyno to this one was to look at the graph based on speed instead of RPM. Also, if Sean went WOT anywhere before 5000 RPM, the car would just go straight to the limiter, which is why I assumed my tranny might be slipping.
All this being said, when comparing the 2 graphs, I gained 10-15 rwhp in and around the 110 mph mark. But at around 120 or so (just guessing because I don't have the graphs w/ me) the PT4400 hp curve just flatlines and the Midwest hp curve jumps above it and peaks 30 hp higher.
So, it looks like at around 5200 the hp curve just table tops. There's no sudden jumps or anything that would symbolize a misfire or knock. Previously, my car was tuned to 13.3 a:f across the board but it was very lean this time around (14.1). So after some tuning we got it back to the 13.3 area. I guess it's a possibility that there's a fuel pressure issue up top that's not allowing it to peak. Or it might be that tranny. I'm going to change the plugs, check the fuel pressure, and go from there.
All this being said, when comparing the 2 graphs, I gained 10-15 rwhp in and around the 110 mph mark. But at around 120 or so (just guessing because I don't have the graphs w/ me) the PT4400 hp curve just flatlines and the Midwest hp curve jumps above it and peaks 30 hp higher.
So, it looks like at around 5200 the hp curve just table tops. There's no sudden jumps or anything that would symbolize a misfire or knock. Previously, my car was tuned to 13.3 a:f across the board but it was very lean this time around (14.1). So after some tuning we got it back to the 13.3 area. I guess it's a possibility that there's a fuel pressure issue up top that's not allowing it to peak. Or it might be that tranny. I'm going to change the plugs, check the fuel pressure, and go from there.
cause the drum doesnt actually measure hp, it measures torque aplied to the drumand uses the basic equation to translate that to hp and if the wrong rpm was used in the equation it would throw your graph way off. But I guess it didnt do that, because that would overquote you hp if it gave your torque reading for 6500 at 8500 it would give you a BS high hp number
just see what it does at the track :-\ It will be fine
01-05-2004, 12:19 PM
#16
Originally Posted by 95Snoozer
the rpm on the dyno graph was off?
cause the drum doesnt actually measure hp, it measures torque aplied to the drumand uses the basic equation to translate that to hp and if the wrong rpm was used in the equation it would throw your graph way off. But I guess it didnt do that, because that would overquote you hp if it gave your torque reading for 6500 at 8500 it would give you a BS high hp number
just see what it does at the track :-\ It will be fine
cause the drum doesnt actually measure hp, it measures torque aplied to the drumand uses the basic equation to translate that to hp and if the wrong rpm was used in the equation it would throw your graph way off. But I guess it didnt do that, because that would overquote you hp if it gave your torque reading for 6500 at 8500 it would give you a BS high hp number
just see what it does at the track :-\ It will be fine
01-06-2004, 11:09 AM
#19
Well the car definitely feels faster so I'm not worried about that. It just worries me that I somehow lost 30hp which means that something in or on my car isn't right. I'm going to check the plugs and fuel pressure then see where that takes me.
01-06-2004, 12:26 PM
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Originally Posted by LS1BlackZ28
Well the car definitely feels faster so I'm not worried about that. It just worries me that I somehow lost 30hp which means that something in or on my car isn't right. I'm going to check the plugs and fuel pressure then see where that takes me.
i would just compare the locked numbers for dyno purposes and overlay those two graphs...it seems like you dropped some power not because of the converter but for another reason. im just judging this by 404 vs. 391 rwhp
maybe your numbers somehow got screwed with that problem you were having with the rpm being off? what the hell happened with that?
if anything i find it strange that you were only ever able to pull a 1.81 short time out of a 3500 midwest...hopefully i can get a better 60 with this 3200 stall...this exact one cut a flat 1.50 in someone elses car on nitrous with a nearly stock suspension...so we will see...most of the people i see that pull less that spectacular short times with them seem to never run good enough tire...i know you run good tire so i wonder what the problem was...