Jump to content
SAU Community

Recommended Posts

Hi, I just had my 25 neo tuned today on a apexi power fc. 

The engine is stock except for 3"exhaust all the way and blitz fmic. I have a turbosmart manual boost controller, set at 10psi. 

But after 4500rpm, the boost won't hold and lowers to 7psi at higher rpms. 

Is it time to start searching for boost leaks? Or is there something I'm missing? 

Thnx. Jasper

Link to comment
https://www.sau.com.au/forums/topic/480086-rb25det-boost-wont-hold/
Share on other sites

I deleted the 2 stage boost solenoid. Incoming line to the turbosmart boost T comes from the turbo, and outgoing goes to the wastegate actuator. 

Anyone else using only a manual boost controller and running 10+ psi? 

I think something is not right, it should hold boost

18 minutes ago, Jasper34gtt said:

I deleted the 2 stage boost solenoid. Incoming line to the turbosmart boost T comes from the turbo, and outgoing goes to the wastegate actuator. 

Anyone else using only a manual boost controller and running 10+ psi? 

I think something is not right, it should hold boost

You didn't mention the bleed - you do have the right one going to the actuator?

To test properly for boost leaks you need to make up a plug and put about 20 psi into it. Leaks are sometimes hidden from sight and hard to hear with the motor running.

3 hours ago, Jasper34gtt said:

The T only has one input and one output... In comes from turbo, out goes to wg actuator. 

I think that's correct 

OK so it bleeds to atmosphere. Is it supplied from a nipple in the compressor housing? Have you tried turning up the boost? I see the turbosmart instructions suggest removing the ball and spring in some applications - have you tried that?

Using the cold charge pipe as feed instead of directly from the turbo housing, shouldn't matter I think. But I'll try

4 hours ago, KiwiRS4T said:

OK so it bleeds to atmosphere. Is it supplied from a nipple in the compressor housing? Have you tried turning up the boost? I see the turbosmart instructions suggest removing the ball and spring in some applications - have you tried that?

From the compressor housing yes. I tried turning it up and stopped at 11psi. Then after 4500rpm it goes back to 7psi for some reason. I will try your suggestion to remove the ball and spring. Thanks

1 hour ago, Jasper34gtt said:

 

Just a thought... Could it be that the stock cat is too restrictive and exhaust gas pressure is pushing the wastegate flap back shut? 

It could be blocked too. Either way I would either lose it altogether or get a better flowing one. If you can without outraging the neighbours  you could try dropping the exhaust altogether to see if that is where the problem lies. 

Also, if dropping the ball and spring doesn't help you could pull the hose right off and , driving carefully so as not to overboost , see if the problem is with the wastegate.

7 hours ago, Jasper34gtt said:

Using the cold charge pipe as feed instead of directly from the turbo housing, shouldn't matter I think

But you would be very very wrong.

There is enough pressure drop across the shitty sidemount for that to be a bad idea. Although it should result in other bad effects, not low boost.

I'd seriously be looking for boost & exhaust leaks.

11 hours ago, KiwiRS4T said:

It could be blocked too. Either way I would either lose it altogether or get a better flowing one. If you can without outraging the neighbours  you could try dropping the exhaust altogether to see if that is where the problem lies.

Look you should drop the cat as Kiwi said just to eliminate that as a cause, but it probably isn't. I've had completely blocked cats. The side effect generally is it is pathetically gradual to build to peak boost, makes jack power everywhere, but the peak boost is still usually up the rev range. Blocked cats generally do not cause a spike to peak boost then drop like you are explaining.

I think the problem is elsewhere, but do it just to check anyway.

Ok I will check the cat. 

And as for boost coming from hot or cold pipe, I just installed it exactly the way turbosmart advised. 

 

People do have good boost over the complete rev range with just a manual boost controller? Or do most people install a rb20 actuator? I thought I might give that a try... Maybe the wg spring is just too weak

22 hours ago, KiwiRS4T said:

 

 

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Surely somebody has one in VIC. Have you asked at any shops?  Is this the yearly inspection or did you get a canary?
    • This is where I share pain with you, @Duncan. The move to change so many cooling system pieces to plastic is a killer! Plastic end tanks and a few plastic hose flanges on my car's fail after so little time.  Curious about the need for a bigger rad, is that just for long sessions in the summer or because the car generally needs more cooling?
    • So, that is it! It is a pretty expensive process with the ATF costing 50-100 per 5 litres, and a mechanic will probably charge plenty because they don't want to do it. Still, considering how dirty my fluid was at 120,000klm I think it would be worth doing more like every 80,000 to keep the trans happy, they are very expensive to replace. The job is not that hard if you have the specialist tools so you can save a bit of money and do it yourself!
    • OK, onto filling. So I don't really have any pics, but will describe the process as best I can. The USDM workshop manual also covers it from TM-285 onwards. First, make sure the drain plug (17mm) is snug. Not too tight yet because it is coming off again. Note it does have a copper washer that you could replace or anneal (heat up with a blow torch) to seal nicely. Remove the fill plug, which has an inhex (I think it was 6mm but didn't check). Then, screw in the fill fitting, making sure it has a suitable o-ring (mine came without but I think it is meant to be supplied). It is important that you only screw it in hand tight. I didn't get a good pic of it, but the fill plug leads to a tube about 70mm long inside the transmission. This sets the factory level for fluid in the trans (above the join line for the pan!) and will take about 3l to fill. You then need to connect your fluid pump to the fitting via a hose, and pump in whatever amount of fluid you removed (maybe 3 litres, in my case 7 litres). If you put in more than 3l, it will spill out when you remove the fitting, so do quickly and with a drain pan underneath. Once you have pumped in the required amount of clean ATF, you start the engine and run it for 3 minutes to let the fluid circulate. Don't run it longer and if possible check the fluid temp is under 40oC (Ecutek shows Auto Trans Fluid temp now, or you could use an infrared temp gun on the bottom of the pan). The manual stresses the bit about fluid temperature because it expands when hot an might result in an underfil. So from here, the factory manual says to do the "spill and fill" again, and I did. That is, put an oil pan under the drain plug and undo it with a 17mm spanner, then watch your expensive fluid fall back out again, you should get about 3 litres.  Then, put the drain plug back in, pump 3 litres back in through the fill plug with the fitting and pump, disconnect the fill fitting and replace the fill plug, start the car and run for another 3 minutes (making sure the temp is still under 40oC). The manual then asks for a 3rd "spill and fill" just like above. I also did that and so had put 13l in by now.  This time they want you to keep the engine running and run the transmission through R and D (I hope the wheels are still off the ground!) for a while, and allow the trans temp to get to 40oC, then engine off. Finally, back under the car and undo the fill plug to let the overfill drain out; it will stop running when fluid is at the top of the levelling tube. According to the factory, that is job done! Post that, I reconnected the fill fitting and pumped in an extra 0.5l. AMS says 1.5l overfill is safe, but I started with less to see how it goes, I will add another 1.0 litres later if I'm still not happy with the hot shifts.
    • OK, so regardless of whether you did Step 1 - Spill Step 2 - Trans pan removal Step 3 - TCM removal we are on to the clean and refill. First, have a good look at the oil pan. While you might see dirty oil and some carbony build up (I did), what you don't want to see is any metal particles on the magnets, or sparkles in the oil (thankfully not). Give it all a good clean, particularly the magnets, and put the new gasket on if you have one (or, just cross your fingers) Replacement of the Valve body (if you removed it) is the "reverse of assembly". Thread the electrical socket back up through the trans case, hold the valve body up and put in the bolts you removed, with the correct lengths in the correct locations Torque for the bolts in 8Nm only so I hope you have that torque wrench handy (it feels really loose). Plug the output speed sensor back in and clip the wiring into the 2 clips, replace the spring clip on the TCM socket and plug it back into the car loom. For the pan, the workshop manual states the following order: Again, the torque is 8Nm only.
×
×
  • Create New...