How to Tune 5EAT Line Pressure

[ClimberDHexMods]

Cool, thanks for the reply. I will keep watching and pretending like I know what all this technical talk means

 

If it makes you feel any better, Infamous has not noted any issues with my +30% RT map. I still hit 100% throttle, car still drives fine, etc. So far so good.

[seabass07]

ClimberD, have you logged RT yet? I'm curious whether it will show anything over 408.

[ClimberDHexMods]

ClimberD, have you logged RT yet? I'm curious whether it will show anything over 408.

 

No, I can do so in a couple days hopefully. Need to get new fuel lines on first so I don't die in a fire

[KyLegacy 2.5GT]

Well, the other day I changed my Requested Torque and Throttle Plate maps by +40% and I can definitely feel a difference in the shifting of my car. After reading utc_pyro's post about logging line pressure, I decided to go out to my car and give it a shot..... So here are the results.

 

In Drive (1st pic): An instant line pressure jump up to the stock 1370kpa is noticed and then it immediately drops to 490 kpa. No line pressure increase over stock with the modified maps.

 

In Sport (2nd pic): Again, an instant line pressure jump up to the stock 1370kpa is noticed and then it immediately drops to 490 kpa. No line pressure increase over stock with the modified maps.

 

In Sport Manual (3rd pic): An instant line pressure jump up to the stock 1680kpa is noticed and IT STAYS! (utc_pyro's hidden launch control term). But still, no line pressure increase over stock sport manual values with the modified maps.

 

Soooo, long story short, we are not changing the line pressure by adjusting these maps. There have been a lot of us reporting the difference in shifts with this modification, but what are we changing?

 

Utc-pyro, why do you call the higher line pressure launch control? Shouldn't this be called something more like 'higher line pressure for punching it at a dead stop '....... (this is my inner engineer speaking). Launch control is an automated program that allows engine and transmission management to help launch a car with the least amount of wheel spin and get up to speed as fast as possible. Launch control also allows the driver to rev the engine at a dead stop in drive without the transmission trying to push against the brakes. In our cars, when we torque brake, the car pushes against the brakes. In an Evo or GTR is launch control, the engine will rev to the programed launch RPM without all of that load on the trans. In our cars, if you were to try and rev the engine up to 5000 rpm with the brakes on, you would destroy the clutch packs in the trans, and that's why we are not to launch our cars on a stock trans with stock torque converter. I can talk about this for a while, but I think I have the point across.

 

Anyways, mad props to utc_pyro for finding out about the hidden line pressure increase and this is definitely a start in the right direction!!!!

[utc_pyro]

Yeah, it's not really launch control. It just makes it safer to torque break for a launch as you're less likely to slip any of the clutches in the process.

 

On your '05 in "manual" mode when not starting from a dead stop, does the line pressure still drop down significantly when cursing? Mine appears just slightly higher than auto mode for normal steady driving, only peaking hither at full throttle or from a dead stop.

 

Also you might want to try logging the other clutches as well. I'll go drive around and see what my peaks are and we can compare. It may not increase the primary line pressure, but it might increase the pressure to individual clutch packs.

[ClimberDHexMods]

I suspect we need to do a lot more testing. Putting it in drive at a stop is a fine start, but what about when driving? I say this because a) vacation pics says so, and b) some are noticing a difference... What is causing that difference?

[seabass07]

We may be looking at this wrong. We may not be increasing the top line pressure. We may just be raising line pressure in lower rpm shifts to hit the max sooner. There is a noticeable difference in lower and mid RPMs. I can't tell if there's a difference at WOT. It is possible that we are just changing the curve, but keeping the max the same. We definitely need more testing. We also need to look at all of the pressures that freessm will show us.

[ean611]

We may be looking at this wrong. We may not be increasing the top line pressure. We may just be raising line pressure in lower rpm shifts to hit the max sooner. There is a noticeable difference in lower and mid RPMs. I can't tell if there's a difference at WOT. It is possible that we are just changing the curve, but keeping the max the same. We definitely need more testing. We also need to look at all of the pressures that freessm will show us.

 

You probably hit the nail on the head. The max line pressure (1370kpa) is probably a pretty good shift, but if it's reserved for WOT, we're not driving WOT for most of the time. They tuned the TCU for stock power levels, so with the mods most of this forum has, the line pressure is low. By raising the line pressure at low RPM, it may be making up the ground lost by tuning the car.

 

On my 08, the issue is shifting between 1st and second is a bit slow at low RPM. increasing line pressure with this will probably be a big help, even if it is just brining in the max earlier. WOT shifts are rarely the issue if you have the VB mod.

[lieutenantcolumbo]

 

In Sport Manual (3rd pic): An instant line pressure jump up to the stock 1680kpa is noticed and IT STAYS! (utc_pyro's hidden launch control term). But still, no line pressure increase over stock sport manual values with the modified maps.

 

 

 

 

My transmission shop told me that when you manually shift the 5EAT transmission it uses higher line pressure than when it shifts automatically. This is better for your clutches.

 

 

When my transmission started to fail I drove around for a while exclusively in manual mode just because the transmission would slip less.

 

While it was being rebuilt, my transmission shop confirmed to me that the transmission applies higher line pressure while it is manual mode, and that's why it didn't slip as much when I changed gears myself. Fourth and Fifth were the gears that were slipping, so line pressure in manual mode is increased for all gears.

[underground000]

I posted this in SEAT:lol: Pride also because OP posted it there

 

The high line pressure at stop I think would be normal in any automatic car. When fully stop the engine is forcing the torque converter to spin but it not going to. and when you start moving theres torque multiplication up to 3x (for 5eat) up until the stall speed of the converter.

 

Because we cannot slip a clutch to get moving we make can make a lot more torque to get the car moving if we dont the car will bog down and stall. And because of that added torque there needs to be a higher line pressure so the clutches wont slip. And this high torque amount of torque is only in 1st gear from stop, when the car is moving it takes less 'force' to get the car moving

 

For some guys that get weird/very high dyno numbers is because the converter isnt locked and its multiplying the torque that why you get high readings.

[fishbone]

Fourth and Fifth were the gears that were slipping, so line pressure in manual mode is increased for all gears.

How were they slipping, how was the car behaving? In manual mode it shifts fine for me but in full auto sometimes it just almost coasts into 4th and I'm not liking it. The revs just slowly decrease instead of dropping. I guess I'll have to do some road testing to see. I can still feel the car pulling while that's happening.

[lieutenantcolumbo]

How were they slipping, how was the car behaving? In manual mode it shifts fine for me but in full auto sometimes it just almost coasts into 4th and I'm not liking it. The revs just slowly decrease instead of dropping. I guess I'll have to do some road testing to see. I can still feel the car pulling while that's happening.

 

 

Oh you'll know when it happens. Mine got so bad in 5th that even light to moderate acceleration on a level road could send the revs up, speed would start to slow, and you could feel it slipping.

[lieutenantcolumbo]

 

On your '05 in "manual" mode when not starting from a dead stop, does the line pressure still drop down significantly when cursing? Mine appears just slightly higher than auto mode for normal steady driving, only peaking hither at full throttle or from a dead stop.

 

 

I don't think "cursing" has any effect on my line pressure, and I've used some good ones!

[seabass07]

I've got the same results with my line pressure. I logged all of the solenoids with a 30% increase in RT and then with 27.5. I know there isn't much difference, but the 27.5 fixed all of my throttle problems. That confirms to me that anything over 408 RT is going to mess things up on the 05 ecu. The car will use the part of the throttle position that correlates to 408 RT on the TP map effectively reducing the throttle plate position.

 

My max line pressure for all solenoids except the L/U solenoid (it was 620, I'll have to look up which one that is) is 1370. The base number of 490 slowly increases with RPM and TP. When I start in first in manual, it goes up to 1680 and holds it for a bit. It looks to me that the only way we will be able to increase the max will be with a VB mod or possibly a resistor.

 

My thinking is that line pressure is scaled to certain voltages from the TCU. We can't make it go higher because it at it's maximum voltage. If we could rescale that in the TCU, then we could do whatever we want. Or we can attempt to use the resistor mod to trick it.

 

Changing the RT tables does appear to effect shifting line pressure across the board below WOT without changing the max. It also seems to be increasing holding line pressure by changing the ratio that it increases with RPM.

[utc_pyro]

We may be looking at this wrong. We may not be increasing the top line pressure. We may just be raising line pressure in lower rpm shifts to hit the max sooner. There is a noticeable difference in lower and mid RPMs. I can't tell if there's a difference at WOT. It is possible that we are just changing the curve, but keeping the max the same. We definitely need more testing. We also need to look at all of the pressures that freessm will show us.

You probably hit the nail on the head. The max line pressure (1370kpa) is probably a pretty good shift, but if it's reserved for WOT, we're not driving WOT for most of the time. They tuned the TCU for stock power levels, so with the mods most of this forum has, the line pressure is low. By raising the line pressure at low RPM, it may be making up the ground lost by tuning the car.

 

On my 08, the issue is shifting between 1st and second is a bit slow at low RPM. increasing line pressure with this will probably be a big help, even if it is just brining in the max earlier. WOT shifts are rarely the issue if you have the VB mod.

 

I think you two nailed it. We DO need to do testing though.

 

My thinking is that line pressure is scaled to certain voltages from the TCU. We can't make it go higher because it at it's maximum voltage. If we could rescale that in the TCU, then we could do whatever we want. Or we can attempt to use the resistor mod to trick it.

 

Pretty much. It's actually less power out = more pressure, but there is head room. It's duty cycle based with a ~6-12ohm load. So 100% is 2A, max pressure (0%) is 0A, and the 1680kpa is at .11a (~6% duty cycle). Thus if we do get into the TCU, we can go up in pressure a little bit.

 

I can build an "intercept" module that can read the PWM from the TCU and modify it, I actually did a project like that in a class ~2 years ago. The resistor mod will work, and is the cheapest, but it won't increse that absolue max quite as much as part throttle.

 

Speaking of resistors, I need to go ship those out tonight.

[seabass07]

In theory, with a resistor, we should be able to get that 1680 across the board for all shifts. That's a big difference. If we can do that, there may be no need for a VB mod. That tells us what it is capable of in stock form.

[utc_pyro]

In theory, with a resistor, we should be able to get that 1680 across the board for all shifts. That's a big difference. If we can do that, there may be no need for a VB mod. That tells us what it is capable of in stock form.

 

 

1680 kpa on all or just WOT? For all, you'd need to put a 6 ohm dummy reistor between the P/L solonoid output and ground, and wire the input to the valve body to a 120ohm resistor to +Vbat.

 

For all WOT shifts, I think that can be done... Let's look at the math (just algebra)

 

We'll just use Ohms law: V=IR

Also this is presuming duty cycle = voltage

 

Presume the stock solonoid is 6 ohms (it varries a little car to car) and the TCU will fire off a CEL if above 12 ohms.

 

1370kpa = 0.26A to the P/L solonoid => "1.56V equivilent"

1689kpa = 0.11A to the P/L solonoid => "0.66v equivilent"

 

So we need to drop ~.15A of current, .9v to get the desired pressure.

 

So, to make it to the required current, the reistor would need to be 9ohms. That WILL trip a CEL, and isn't even taking any current feedback correction into account. So we'll need something more advanced.

[KyLegacy 2.5GT]

Just to clear up the kpa unit issue for some of you guys:

kpa (kilopascal) is a unit of pressure in the metric system

 

To get to the more common unit of pressure, psi (pounds per square inch), you would need to multiply the given kpa values we have been talking about by 0.14503773773020923.

 

Sooo, here are the corrected values:

490 kpa = 71.069 psi

1370 kpa = 198.702 psi

1680 kpa = 243.663 psi

 

The values we are seeing in the Sport Manual mode are pretty high. I am not familiar with other transmissions and what their solenoids run at, but I think we need to do some research on these pressure before going much higher. We are seeing pretty big jumps here between modes, but how much more of a jump can we take safely?

[seabass07]

I would also like to see what the VB mod does to these peak values.

[utc_pyro]

Right. I kind of doubt that the pressure is REALLY that high inside the transmission. Probably like "requested torque", it more of a guideline.

[fishbone]

Any new development on this front? The beta AP firmware now shows requested torque, and completely unsurprising the top value seen at WOT is 320Nm and it reminded me of this thread.

[underground000]

I broke my lappy top so I did not update the AP

[seabass07]

Is it a different scale on the AP? Because romraider shows mine maxing out at 408 and effecting throttle plate position negatively if the RT map is higher.

[fishbone]

Any updates on this? Any more people done it? Anyone else verify a marked change and improvement?

[underground000]

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