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Auto Trans Pressure?

FBRacing
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FBRacing Rising Star

FBRacing

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I've looked from start to finish in every thread, my books, and on the web and I can't find the answer. What is the pressure for the inlet/outlet for the auto in a R33? Trying to diagnose to see its in parameters. Just reached the 400kw at wheels and I want to watch what trans is doing on the dyno on Wednesday when we dial it in better. Also if I just put a tee in the cooler line, would it give me an accurate reading? In my head it wouldn't. If I'm right, any ideas where to tap into?

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Ben C34 Grand Master

Ben C34

Posted
Posted (edited)

The cooler line isn't under pressure. So you can't tap in there.

Who built the trans? Why don't they know? There's no way you would be running stock pressure anyway.

Edited by Ben C34
FBRacing Rising Star

FBRacing

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I don't know who built the trans cuz it was already built when I purchased the car. Have receipts for parts but no receipt for install. Upgraded clutches and bands, manual valve body conversion, upgrade input and tail shaft, and a 2800 stall. Have a 10 pass trans cooler with own fan. Bought the car almost as is and 3 injectors went bad. Long story short, wanted to retune the car with the new injectors. Trans is super strong but when driving it around the block after intense dyno runs I thought it shifted weird. Could have been a fluke or just in my head. I've always had bad luck after a dyno run. Something always breaks.

Kinkstaah Grand Master

Kinkstaah

Posted
Posted

Hook an ECU to it ;)

From what I gathered from speaking to the guys that built my trans was that there's no real way to know without some sensor or ECU reading pressure inside the box, it wasn't alterable unless there's a computer to alter it.

I once had the same sensation after going rather hard through the hills, figured it was heat related at the time. :P

There's not much you can really do though, if its not right.. Add fluid. If you have enough fluid.. Well... It has to come out :P

At least that's what I gathered from long conversations with guys who breathe AT systems all day.

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

Track down Mike at MV Autos 1 Stirling Road Blackwood in Australia - he does a lot of beefed up Nissan autos - you will need to find (google) a phone number rather than emailing.

However at 400kw I think your Nissan auto's days are numbered and you need to go manual or get in to the serious 2 speed drag boxes

KiwiRS4T Grand Master

KiwiRS4T

Posted
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That's what I'm afraid of. It's getting softer and softer. Drove it last night and it felt even more "slushy". Does a stock manual hold 400kw or will it need to be built?

Stock mine didn't last long with 280kw (so I stuck a GTR box in it). Beefed up stockers are allegedly good for 500hp (depending on who built them) but i don't know for how long.

FBRacing Rising Star

FBRacing

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Stock mine didn't last long with 280kw (so I stuck a GTR box in it). Beefed up stockers are allegedly good for 500hp (depending on who built them) but i don't know for how long.

Thanks for your input

scotty nm35 Grand Master

scotty nm35

Posted
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There is usually a pressure reading point on the side, for plugging external pressure gauges into. All that will tell you is the line pressure, which changes dependant on many variables, including temperature. Does the fluid still go through the radiator, or is it just going to the front oil cooler?

Do you know what box it is? Patrol/300z boxes can be built for 1200hp. If it's a stock box built, you are probably near its limit.

FBRacing Rising Star

FBRacing

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I must admit I'm not super excited about the car being auto when I first bought it but it sure pulls hard when everyone else is shifting. Was the first thing to go but life gets in the way. I've talked to auto gurus about it but they really can't say themselves. Know what the pressure would be with stock internals? Some kind of baseline to go off of would be helpful. Thought about going to an oil and lube shop to get a trans flush. Most lube shops use a machine to flush the trans fluid out that have a pressure gauge for flow. Only prob is I'm not sure what's good or bad

scotty nm35 Grand Master

scotty nm35

Posted
Posted

The lines to the cooler are after the torque converter, they won't tell you the line pressure off the pump outlet.

Have you installed the trans cooler? Usually the trans needs to get to a certain temp before the TCU will shift properly. Temp is much more important than pressure imo.

You are probably looking at 250psi or more pressure at the pump.

FBRacing Rising Star

FBRacing

Posted
  • Author
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The lines to the cooler are after the torque converter, they won't tell you the line pressure off the pump outlet.

Have you installed the trans cooler? Usually the trans needs to get to a certain temp before the TCU will shift properly. Temp is much more important than pressure imo.

You are probably looking at 250psi or more pressure at the pump.

I do have a trans cooler. About 30cm x 30cm with a fan. It's a manual valve body like Ben said. 250 psi!?! That's a whole lot more than I figured. Thinking around the 100-150 range

scotty nm35 Grand Master

scotty nm35

Posted
Posted

Ah, ok.

With a manual valve body there is no way the line pressure can be adjusted for temp changes, so when it's cold on the road there will be changes to the shift pressures and times that can't be accounted for due to the lack of a TCU. I hope you at least have a thermostat in the trans cooler lines...

As Greg mentioned above, a PCS controller is expensive but it changes the way the auto drives substantially, and allows infinite adjustment via a laptop. I was surprised how well his car drove, better than a manual or DSG I thought, and I usually hate auto's.

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