Stock S14 SR hitting 12 lbs.....normal?

[khilgers]

I just got my S14 SR running about a week ago. It is mostly stock with only turbo elbow, downpipe, and exhuast. Other than that, stock fuel, computer, everything. Driving around it will stay around 7-8 lbs. then spike to 12, is this normal? From my understanding the stock computer was meant to keep it at around 7-9. I checked all of my vaccum lines and they check out, my wastegate is obviously working, but what else could it be? Could it be that the previous owner upgraded actuators? I checked the wastegate actuator arm and it does not seem to be bent. Any ideas? Pardon my ignorance, this is my first turbo car, and I'm still learing as I go. Thanks in advance.

Is it OK to run these motors, untuned at 12 lbs.?

[DOOK]

may have one of those HKS wastegate upgrade deals, I think they boost a T25 that high and now that I think about it, you probably have a T28 so yeah, spiking to 12 is ok.

[khilgers]

but why would it be spiking at 12 if the computer is only "supposed" to allow it to get to around 7?

[Irukandji]

Check the line going from the wastegate actuator going to the boost source. To my understanding, the closer the boost source to the turbo, the better.

[khilgers]

that's one thing I was wondering about. The intercooler kit I bought comes with a nipple on the cold pipe that is intended for the line going to the wastegate. This is what I used so my line is going all the way from my coldpipe, along the front of the valve cover, and finally connecting to the wastegate. All in all it is about 2 1/2 feet long. Is there another vaccum source that is closer I could tap into and run to the wastegate, or am I going to have to put a nipple on my hotpipe and run it that way?

[superJoy]

Yes, the vacuum source should be as close as possible to the turbo. If you want to relocate the vacuum source, you have several options. You can:

- weld a new nipple on the hotpipe (this is an acceptable way of doing it, as the stock SMIC piping uses a nipple on the hotpipe as the vacuum source for the wastegate actuator, at least on S13 SRs)
- install a "quicktap" that splices into the silicon connector (http://www.atpturbo.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=tp&Product_Code=ATP-FTG-010&Category_Code=BCS)
- drill and tap for a fitting either in the compressor housing itself or the outlet elbow

I opted for #3 for my wastegate source. I'm running an SR turbo on a CA18, so there was no previous source (original turbo on CA's had the source on the compressor housing). I used a $2 fitting from O'Reilly's, something like 1/4" NPT to 1/4" hose barb if I recall correctly, and drilled and tapped a spot for it on the compressor outlet elbow.

http://i8.tinypic.com/631ikbl.jpg

I chose that spot due to it being the flattest, most practical spot to put the fitting. The vacuum line does need to be looped a little bit to plug in there from the wastegate actuator (they're REALLY close to each other, clearance is tight for the line), at least on the SR T25. A 1/8" NPT is probably a better fitting to use here due to its smaller size, but I used what I could find locally.

Another reason you could be getting boost spikes is the upgraded exhaust system. If I'm thinking right, it's pretty common for a freer flowing exhaust to overrun the wastegate somewhat and cause it to spike the boost level.

[khilgers]

I plan on running a manual boost controller soon and I imagine I would want to keep the lines as short as possible. Thanks for the help, I will look around tomorrow for a hose barb and also investigate the exhaust to see if that's causing it.

[khilgers]

So I got my compressor outlet tapped and installed a brass hose barb. Everything is hooked back up and sealed, but I am still getting the same boost spike. Would a manual boost controller take care of this and keep it from going above 10 lbs?

http://www.khilgers.com/forumpics/wgline.jpg

[DJ_Sunrise]

Sort of would. Depends what the issue is. Take a better pic of the shaft for the actuator. If I'm not mistaken.. OEM are not adjustable. If it is adjustable then it is after market. If wastegate were to be set at "x" psi, mbc would do minimum "x".. raising boost would = x+.5,....,x+6.

-Bart

[khilgers]

here are 2 pics of the actuator shaft, looks completely stock to me.

http://www.khilgers.com/forumpics/wgshaft1.jpg
http://www.khilgers.com/forumpics/wgshaft2.jpg

[khilgers]

anyone have any other ideas?

[Sileighty_85]

Well that definatly a stock actuator.
another possiblity could be that your actuator has a hole in the diafram.

[DJ_Sunrise]

take the clip off of the actuator where it ataches to the gate and pop the rod off. pull the rod out as far as you possibly can, and then put your finger or a vacuum cap over the actuator nipple. leave it be for like 10 minutes and see if it so much as budged. if it moves at all, you need to replace the actuator. i have a stock one i know is in good working order if you want it.

-Bart

Edit: If you buy a boost controller, buy the Forge Unos. Electronic ones have all these gadgets and whoop dee doo's.. to most people that shit just means more to break, including myself. Evo guys love the Forge. Evo enthusiasts are big on using MBC's, and as it turns out the Forge is their favorite. I felt a massive difference with this MBC.. It pops that actuator open perfect everytime and right at the last second... MASSIVE power difference with it on..

-Bart

[Nikeboy355]

You are fine at 12lbs. untuned... The ECU knows that more air is coming in via the MAFS and adjusts accordingly...

[bigOdom1]

dont plan on turning it any higher though as the injectors are close to limits. but you lucked out and got a free mod as long as everyting else is in line. get it on a dyno/af reading not a narrowband electric light show to check it all

[Slidin240Wayz]

Yes, the vacuum source should be as close as possible to the turbo. If you want to relocate the vacuum source, you have several options. You can:

- weld a new nipple on the hotpipe (this is an acceptable way of doing it, as the stock SMIC piping uses a nipple on the hotpipe as the vacuum source for the wastegate actuator, at least on S13 SRs)
- install a "quicktap" that splices into the silicon connector (http://www.atpturbo.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=tp&Product_Code=ATP-FTG-010&Category_Code=BCS)
- drill and tap for a fitting either in the compressor housing itself or the outlet elbow



Thank you so much. I will be doing this very soon.

Carlos

[Mikester]

You are fine at 12lbs. untuned... The ECU knows that more air is coming in via the MAFS and adjusts accordingly...

Actually not quite the case... SR's run inherently lean untuned. The stock ECU will only supply fuel to about 70-80(ish) percent of the injector duty cycle regardless of how much air the MAF is reading. Even running 12-14psi with my power FC installed, which ran my injectors at full capacity, it wasn't uncommon to see my knock reading at 80+ (scale is 0-100). Now with 850's and a proper tune, my knock rarely exceeds single digits.

However, if this guy's only experiencing a momentary spike then yeah, I'd agree wholeheartedly that he's in the green.

Awesome pictoral & some great ingenuity SuperJoy!:2f2f:

[bigOdom1]

well i had no problems for over a year at 12 psi i dont think it would be a problem. if i was there again i would do it the same

[johngriff]

Ever take a wide band off of it?

[bigOdom1]

yeah it was actually a little rich. mods were: walbro255, 3"downpipe and exhaust, front mount, and boost controller

[mwilloughby87]

You are fine at 12lbs. untuned... The ECU knows that more air is coming in via the MAFS and adjusts accordingly...

i was under the impression that an s14 didnt have a mafs?

[bigOdom1]

you were under the wrong impression all sr have mafs unless it was converted to map on another engine management

[khilgers]

Ok so I got a different actuator from DJ Sunrise and I am still creeping to 15 lbs. I'm pretty much out of ideas at this point. I have the vaccum line to the actuator as close as possible. I checked all other vaccum lines. I have a working actuator and it still creeps. Could it be a tune on the computer, but from my understanding you CANNOT tune the kouki code "NA" ecu? Any help would be greatly appreciated.

[fliprayzin240sx]

K now my question is...what gauge are you using? I dont understand how a stock actuator will boost pass 7-8 psi. Its just not possibble unless something is wrong with the actuator itself and this is what? 2nd or 3rd actuator? Its not the ECU that controls how much boost you run, its the actuator itself. It can only physically hold up to 7-8 psi of boost before it opens up. So like i said, its either a bad boost gauge or another bad actuator...

And no 12 psi is not kosher for his setup...I didnt see a fmic or anything to add extra fuel into the engine. Stock sidemounts limit is pretty much close to 10 psi, anything after that, your liable to push hot air and SRs go bubye. Same thing with fuel, having either a SAFC or an FPR is needed for the extra air or the car is going to go lean.

[khilgers]

I am running a DEFI boost gauge. I am getting the vaccum signal from a "T" off of the pressure regulator. Is there a better vaccum source to hook up to the gauge? This is the 2nd actuator I have used including the one that came with the motor.

Also I should have noted my mods list:

FMIC
Exhaust
downpipe
intake

untuned ECU

[usdm180sx]

When I upgraded to a greddy turbo elbow and an s15 smic on my s14 sr the motor picked up another .25 bar of boost which is around ~11.25psi and it ran fine

[khilgers]

so as this point it could either be:

1) a bad actuator
2) incorrect boost source to gauge
3) It's climbing beyond 8psi. due to the elbow, downpipe, exhuast, and FMIC

[superJoy]

I dont understand how a stock actuator will boost pass 7-8 psi. Its just not possibble unless something is wrong with the actuator itself and this is what? 2nd or 3rd actuator? Its not the ECU that controls how much boost you run, its the actuator itself. It can only physically hold up to 7-8 psi of boost before it opens up.No, not necessarily. Ever heard of boost creep? There's a limit to how much exhaust the wastegate can bypass physically--the wastegate opening is only so large. The addition of a larger-bored exhaust system would naturally cause the exhaust gases to evacuate the system faster (that's why we add the things and they make power), so there's a possibility that it increases the velocity of the gases enough to cause the wastegate to be completely open and still not flow enough to keep the turbine from spinning at whatever RPM creates 8 psi. The solution is to switch to an external wastegate or port the internal one until it flows enough to keep the settings in check.

I did a little research after mentioning the exhaust system causing the increase in pressure, and that's what I found. It's a standard problem, and a Google search of "boost creep" will turn up many results describing the same situation you're in.