Newbie 4L80 owner, is this how stall should work?
10-12-2011, 06:53 PM
#67
No if it goes to a certain points stops then climbs again as boost and rpm comes up and gets louder and louder, rpm, engine noise from rpm, turbo making boost, it gets loud lol, but I absolutely don't think any other sounds gets my adrenaline going than the jet sound of my engine rpm's starting to stall against the converter and the turbo starts to build boost on the footbrake, as it climbs to 3500-3600rpm that sound just gets me evertime, then the two step limiter hits and it starts popping something serious and popping and powin' and poppin and spoolin LOL then BAM release that brake and its gone, nothing else like it in my opinion.
10-26-2011, 11:56 PM
#72
Assuming 5400 rpm engine rpm and 4400 Dshaft rpm, driveshaft, thats a tick over 20%. It will probably be more efficient if you can turn more RPM (usually converters lockup more in the 2nd 1/8 mile compared to the 1st).
10-27-2011, 01:23 AM
#73
I don't know what to say. In other logs where I logged all 5 rpms (I think), slip was equal to engine RPM minus tranny or turbine rpm. So I trust that. And speed at that run indicates 4400 dshaft rpm is correct cause I was at roughly 3/4 of the speed I get at 6000 with TC locked.
What's the reason for "more lockup in 2nd run"? Hotter fluid?
And it was about 1050rpm slipping at 3rd and 2nd run.
What's the reason for "more lockup in 2nd run"? Hotter fluid?
And it was about 1050rpm slipping at 3rd and 2nd run.
10-27-2011, 03:10 AM
#74
The converter is still not completely locked up at the end of the 1/8th mile. To be more efficient, it will need more gear, or to be tightened up (or a lighter car, etc)
A converters stall ( ANY converter) varies based on HP input. A converter that will stall 2000to rpm behind a 100 HP 4 cyl, may stall 3200to rpm behind a 400 HP V8, add a turbo to that V8, and the stall at 0 psi will be 3200 rpm, and may be 4500 rpm at 10 psi.
The more boost you build the higher it will stall, because you are making more HP.
You don't want to be sitting on the converter too long stalled up, it heats the fluid a BUNCH and fast.
A converters stall ( ANY converter) varies based on HP input. A converter that will stall 2000to rpm behind a 100 HP 4 cyl, may stall 3200to rpm behind a 400 HP V8, add a turbo to that V8, and the stall at 0 psi will be 3200 rpm, and may be 4500 rpm at 10 psi.
The more boost you build the higher it will stall, because you are making more HP.
You don't want to be sitting on the converter too long stalled up, it heats the fluid a BUNCH and fast.
10-27-2011, 05:16 AM
#75
When do I expect it to fully "couple" (I understand that it is never truly locked hydraulically, until you use clutch)? Is it normal slip - 1000 rpm at 5400 engine rpm?
yes I realize that stall depends on power.
BUT.
From what I read in stickies, transbrake tests true stall speed. So I expected that custom-built for my engine 3500 TC should stall somewhere in 3500 area, especially on only 60% of power? Now it stalls at 3500 for just few moments before turbo is up to speed and then goes to 4500
yes I realize that stall depends on power.
BUT.
From what I read in stickies, transbrake tests true stall speed. So I expected that custom-built for my engine 3500 TC should stall somewhere in 3500 area, especially on only 60% of power? Now it stalls at 3500 for just few moments before turbo is up to speed and then goes to 4500
10-27-2011, 06:17 AM
#76
When do I expect it to fully "couple" (I understand that it is never truly locked hydraulically, until you use clutch)? Is it normal slip - 1000 rpm at 5400 engine rpm?
yes I realize that stall depends on power.
BUT.
From what I read in stickies, transbrake tests true stall speed. So I expected that custom-built for my engine 3500 TC should stall somewhere in 3500 area, especially on only 60% of power? Now it stalls at 3500 for just few moments before turbo is up to speed and then goes to 4500
yes I realize that stall depends on power.
BUT.
From what I read in stickies, transbrake tests true stall speed. So I expected that custom-built for my engine 3500 TC should stall somewhere in 3500 area, especially on only 60% of power? Now it stalls at 3500 for just few moments before turbo is up to speed and then goes to 4500
The stall speed using a transbrake on a naturally aspirated car will be more or less static. If it stalls 3500 rpm, it does so BECAUSE the engine cannot make anymore HP/TQ to continue to increase the stall of the converter.
In a turbocharged combo like you have, the stall is NOT static because the engine's HP will continue to ramp up the more boost it makes. It depends on how ballsy you want to be with heating up the fluid where it will quit stalling.
It will continue to build boost (and HP and stall) until it reaches the limit of the turbo's ability to build boost (which happens to be where max HP is reached).
The problem is, you'll cook the fluid, balloon the converter, and kill parts long before the turbo quits making boost.
It sounds like your converter is a 3500 stall, and you can build boost on it to increase to 4500.
A turbo converter is a tricky deal to setup. It needs to be loose enough to allow the engine to rpm up a bit, and then couple well enough to create load on the engine to build boost, then be efficient above that threshold so you can't drive through it with the tremendous power the turbo makes.
The builder is guessing at how good you setup the combo. Most setups will need a couple of tweeks to be perfect. If you have a slightly too big turbo or too tight converter, it won't build boost easily. If you have a smallish turbo that spools quickly, a looser converter will waste much of it's torque curve.
The ultimate grading is done one of two ways, either by how well the converter performs on the track, or how well you like the way it performs.
What you have may be the cats meow on the track, but since you don't like the driveability, it's worthless to you.
I know it's a long trip, but if you don't like it, send it back and get it restalled.
I'm sure Chris will fix it up for you.
10-27-2011, 06:21 AM
#77
If you are crossing the stripe at 5400 rpm, with 4400 rpm driveshaft speed in the 1/8th mile (in 3rd gear), your converter is still slipping.
Basically at that point it is acting as a 5400 rpm stall. It will continue to couple better the more time it has to allow the vehicle speed to match engine rpm.
If you measure it at a 1000', if your engine could stay in 3rd, you'll see it has likely nearly completely coupled, even without lockup. The engine speed is higher (further away from the stall and flash speeds) and the car has "caught up' to the converter/engine rpm.
Basically at that point it is acting as a 5400 rpm stall. It will continue to couple better the more time it has to allow the vehicle speed to match engine rpm.
If you measure it at a 1000', if your engine could stay in 3rd, you'll see it has likely nearly completely coupled, even without lockup. The engine speed is higher (further away from the stall and flash speeds) and the car has "caught up' to the converter/engine rpm.
10-27-2011, 07:18 AM
#78
Jake, thanks for your input, very informative!
So 5400in / 4400out is about right, it's how fluid coupling works, right?
And to sum it up a bit:
Is that correct that TC we wanted to stall at 3500 stalls at 4500 now with and will probably stall far beyond 5000 when (IF) I reach 900+ HP?
OR
is it a bit mismatched to my turbo and I could gain a lot in driveability without loosing anything at launch if we tighten it up a bit (300rpm maybe?) ?
edit: if we COULD tighten it up, because cost of this even with free restall could reach $400+ for shipping/taxes...
So 5400in / 4400out is about right, it's how fluid coupling works, right?
And to sum it up a bit:
Is that correct that TC we wanted to stall at 3500 stalls at 4500 now with and will probably stall far beyond 5000 when (IF) I reach 900+ HP?
OR
is it a bit mismatched to my turbo and I could gain a lot in driveability without loosing anything at launch if we tighten it up a bit (300rpm maybe?) ?
edit: if we COULD tighten it up, because cost of this even with free restall could reach $400+ for shipping/taxes...