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-   -   Can't control boost - need advise (https://www.rx7club.com/single-turbo-rx-7s-23/cant-control-boost-need-advise-477056/)

moehler 10-29-05 01:13 PM
Can't control boost - need advise
 
My new engine is finally broken in and I am starting to drive the car hard (tuned with a rich map right now, getting re-tuned in two weeks). I am trying to keep my boost down, but my simple boost control set-up seems to do nothing.

I have a fairly good size turbo (a-spec AP-88 kit) with a Tial wastegate that has an 11 psi spring and a Turbo XS manual boost controller. Basically, even if I turn the controller all the way to the lowest setting the boost still just goes very high. It will climb to well over 20 psi at 85% full throttle in 4th gear by 5k rpms (I only did that once :eek: ).

I thought that with an 11 psi spring, and the boost controller all the way down I should only make about 11 psi. I'm pretty naive about boost control, so any advise would be very helpful. Thanks.

Matt

twokrx7 10-29-05 02:08 PM
Test that wg by applying pressure to the lower nipple to make sure it is actually opening when the pressure approaches the spring pressure of 11 psi. You can do the same to the boost controller to make sure it's set at the right pressure.

moehler 10-29-05 09:20 PM
Originally Posted by twokrx7
Test that wg by applying pressure to the lower nipple to make sure it is actually opening when the pressure approaches the spring pressure of 11 psi. You can do the same to the boost controller to make sure it's set at the right pressure.
How exactly do I do that? I really do not have a pressure source that I can hook up to the nipple on the WG.

alberto_mg 10-29-05 09:39 PM
i think people use a mityvac type of thing for that. hopefully some one will correct me if I'm wrong...

moehler 10-29-05 10:37 PM
Is it hooked up incorrectly?

Here's how I have it:

1) Connector on the side of the Tial wastegate is connected directly to a UIM nipple.
2) The inlet of the Turbo XS boost controller (side nipple) is connected directly to another UIM nipple.
3) The outlet of the boost controller (bottom nipple) is connected to the top nipple of the wastegate.

twokrx7 10-30-05 07:44 AM
Try connecting the UIM to the XS boost controller and then connect the XS to the lower nipple on the WG. Leave the top WG nipple open.

If you leave the XS out of the system you would only connect the UIM to the lower WG nipple and you should get boost around the spring pressure of the WG. With the XS in line it will restrict or regulate the pressure going to the WG so the WG will stay closed until the boost gets to the XS setting.

Back to testing the WG. If you have a hand pump you can test the WG spring setting. Just hose up the pump to the lower nipple of the WG and plumb in a boost gage and you pump it up until you hear or see the WG open.

GUITARJUNKIE28 10-30-05 09:34 AM
before you put the boost controller into the mix, just pop off the line on the top of the wastegate to make sure your wastegate is actually opening. once you're sure of that, do the boost controller.

moehler 10-30-05 11:02 AM
Originally Posted by GUITARJUNKIE28
before you put the boost controller into the mix, just pop off the line on the top of the wastegate to make sure your wastegate is actually opening. once you're sure of that, do the boost controller.
Thanks. I tried this last night at 1:30 am (slow night :) ). Worked perfectly (this car is fast :D) - boost made it to about 13-14 psi and never go any higher. I think this is normal since it's an 11 psi spring and I am feeding the WG boost from the UIM instead of before the IC. I've read that this will cause a few more PSI than the WG spring is set to.


Originally Posted by twokrx7
Try connecting the UIM to the XS boost controller and then connect the XS to the lower nipple on the WG. Leave the top WG nipple open.

If you leave the XS out of the system you would only connect the UIM to the lower WG nipple and you should get boost around the spring pressure of the WG. With the XS in line it will restrict or regulate the pressure going to the WG so the WG will stay closed until the boost gets to the XS setting.
Cool, I'll give this a try today. Thanks a lot. It makes more sense to me than how I had it listed above. The above method, though, seems to be more popular when reading through the forums. Why is this not the typical method that people use?

Poweraxel 10-30-05 11:57 AM
Grant,

setting up a boost controller is a little tricking sometimes especially with a external wastegate... make sure you follow the instructions for the external wastegate option

maxcooper 10-30-05 09:31 PM
Originally Posted by moehler
Cool, I'll give this a try today. Thanks a lot. It makes more sense to me than how I had it listed above. The above method, though, seems to be more popular when reading through the forums. Why is this not the typical method that people use?
The posts you have been reading are probably about electronic boost controllers. Your boost controller does not work the same way that electronic boost controllers work.

I think your only option (other than running no boost controller) is to connect the valve inline with the signal to the wastegate side port and leave the wastegate top port open.

-Max

moehler 10-31-05 06:26 AM
Originally Posted by maxcooper
The posts you have been reading are probably about electronic boost controllers. Your boost controller does not work the same way that electronic boost controllers work.

I think your only option (other than running no boost controller) is to connect the valve inline with the signal to the wastegate side port and leave the wastegate top port open.

-Max
Thanks Max :bigthumb:


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