JETPILOT

iTrader: (51)

The boost isn't spiking. It's holding steady @ 11.5 PSI.

So what's the answer.... UTEC to build a reliable F/A ratio, and an electronic boost controller to control the boost?

Respect
JET

kcobean

iTrader: (2)

Westpak,
I have a 5 pound spring in my wastegate and am still able to pull 11+ pounds of boost with the boost controller turned off. The softer the spring, the faster/easier the gate opens and thus the lower your boost. I too have a pretty free flowing exhaust (Modified GReddy EVO2 which is basically a reverse-Y pipe to a pair of mufflers.)

westpak

iTrader: (19)

I guess I didn't mean to say spike but increase. A lower psi spring and a boost controller would allow you to control your boost. With a 5 psi spring and a controller set at 8 psi should hold pretty well.

That is interesting that with a 5 psi spring you would still go that high, the TN kit is pretty basic in that the only thing affecting boost is the wastegate and turbo spool/flow, so the exhaust would help it go up a bit but not from 5 to 11, maybe there is an issue with the wastgate either physically or how it is hooked up and is not allowing it to operate properly.

kcobean

iTrader: (2)

My wastegate was just replaced replaced with no positive results and the vacuum line routing has been checked, double checked, and verified.

See this thread for details:

https://my350z.com/forum/forced-induction/157278-uncontrollable-boost-mystery-of-the-ages.html

westpak

iTrader: (19)

WOW it is a stumper, I would have thought this would have affected all kits not just some, only thing I would think is thta maybe the wastgate doesn't work the same with all of the tubing plus the turbo being on top away from it? But like I said I would have thought all kits would be affected.

Shalopay33

same problem here. Nismo exhaust, TN kit. Boost around 11-11.5 psi.I double check every line and connections. Everything looks good. Any ideas?

JETPILOT

iTrader: (51)

Is an electrontic boost controller the answer?

Respect
JET

kcobean

iTrader: (2)

I have the top of the line, dual solenoid boost controller. It's completely useless. A boost controller cannot LOWER your pressure below the setting of the WG spring. The function of a boost controller is to hold the gate closed during spool up to better response-time and to increase boost by holding the gate closed more, thus keeping more gas flowing to the turbo. It does this by providing "counter-pressure" on the diaphragm that the signal line from the compressor housing is trying to push open. The answer to this problem is something else.

nissansource

iTrader: (10)

Just FYI my car detonated today. and stumbled for the first time too mid range duno whatsup gas light on low on gas but no wideband hookedup yet or boost livin on the wild side!@

Zivman

iTrader: (19)

I pray for all you turbo owners running an ecu reflash, especially those of you not running a wideband AFR.

A wideband + custom tune is much cheaper than an engine rebuild.

Playing with fire

kcobean

iTrader: (2)

It is highly advised that you don't let your car get low enough on gas that the light comes on. When that happens, the pump can have problems keeping the swirl-pot filled and you'll get air in your lines. When she hits a 1/4 tank....time to fill 'er up.

JETPILOT

iTrader: (51)

So what about a mechanical adjustable boost valve.

Respect
JET

nissansource

iTrader: (10)

Yup you are right ill top her off and throw her on the dyno tomarrow

kcobean

iTrader: (2)

The end result is the same, even if the function is different. A mechanical valve is just a spring loaded poppet-valve that keeps the gate closed until pressure pushes the poppet open. There's a **** or similar to adjust the spring tension on the poppet.

Either way, you can't drop your boost below the WG spring setting (or in this case, whatever odd-ball malfunction is causing our high boost).

If you look at the wastegate, it has two ports, one "lower", and one "upper". The lower one the one closest to the pipe) is used to push the wastgate plunger open and this one is fed by the compressor housing. The 2nd port is on the other side of the rubber/fiber diaphragm that the plunger is connected to and is used to "counter-pressure" the signal from the compressor. Lets say you have a 5 PSI spring in your gate. when the compressor pressure builds to 5 psi, the pressure it provides against the diaphragm will overcome the spring pressure that is holding the plunger closed and the gate will open. If you wanted to run your car with 7 PSI of boost, you would send a 7 PSI control signal from your boost controller to the same side of the diaphragm that that spring is on (which again is the opposite side that the compressor signal is on). That way, the compressor has to push 7 psi into it's side of the wastegate chamber to overcome the pressure sent by the boost controller.

One other note is that as you "approach" your spring pressure, the plunger will start to "creep" open. A boost controller will hold the plunger closed until you hit your actual desired boost level. Eliminating this creep is what gives you better spool time because all of the exhaust stream is applied to get the turbo spinning until it hits the desired boost level instead of allowing some to spill out during spool-up.



Make sense?

JETPILOT

iTrader: (51)

Yeah....... I just hadn't looked at the waste gate to see how it operated. But your description was good. Thanks

Respect
JET

westpak

iTrader: (19)

Very good description and what really puzzles the mind why the boost goes so high even with your 5 psi spring and controller off. It just sounds like the wastegate is not opening which brings it back to maybe the design of the kit prevents enough pressure to get to the wg to open it, I really have not looked at the design of the kit and how the piping/wg install goes so it may not make sense what I am saying.

kcobean

iTrader: (2)

Yep, it is truly mind-boggling. Since it's the pressure signals acting on the diaphragm and not exhaust pressure against the plunger face that opens the gate, back-pressure or the lack thereof should make no difference in the operation of the gate itself.

JETPILOT

iTrader: (51)

The next thing to check is that the waste gate is getting an accurate boost measurment. I will have to hook up my boost guage to my waste gate signal line form the turbo and see what boost signal the waste gat is getting.

It's also interesting I DIDN'T have this problem til I hooked up my exhaust. BUT the exhasut has nothing to do with the waste gate operation which gets it's signal to open from the boost signal line driectly from the turbocharger, and this pressure only opposes the spring pressure on the other side of the diaphram.... I'm correct on this?

Respect
JET

taurran

iTrader: (18)

This has nothing to do with the design of the kit. There are at least 150 of these kits on the road today and very few have reported this problem.

I'm running the fujitsubo exhaust (another person posted above they had the nismo) and while I'm hitting a little over 9psi, my wastegate is still kicking in normally. Besides, if there was a drop in pressure that would point to a leak somewhere rather than just the amount of piping on the kit.

redline350ZZ

iTrader: (1)

Hmm very odd...I have no problems...8 PSI with a Kintix plenum...and a modified Injen SES exhaust to allow for minimal back pressure..I had a reverse Y-pipe made.....My A/F is 10.8 to 1 and the temp here are about 74 degrees when I boost in the morning.......I installed myself....also the Tilton flywheel helps the motor rev so quick I hit boost like nothing......

one would think im a good candidate for this problem as well.....