My S13 RB25 running.. full boost issues..

[mark slide squad]

Well this is my first post here. I got my car running almost 2 weeks ago now. Its an 89 coupe with silvia face, and R33 RB25DET. I am using the Apex'i Power FC with commander for R33 RB25, Z32 mafs, Turbonetics T04E 50 trim ceramic ball bearing stage 3 turbo, Spearco front mount i/c, Spearco aluminum radiator, Turbonetics "raptor" blow off valve, Turbonetics "Evolution" wastegate (I work at Turbonetics/Spearco hence all the similar related parts ) Apex'i Super Intake, 10" dual electric fans, R32 GTR flywheel with Stage 2 clutchmasters clutch and pressure plate, custom engine mounts, crossmember, and trans mount, R33 GTR fuel pump, custom extension pipe, 3" stainless downpipe with 3" stainless catback K-Style exhaust, and some other minor mods. OK here is the problem.. the car runs beautifully and everything seems good, even wired up the power for the VTC and O2 heater and AIV ( I noticed a lot of people don't know about that) and wired the harness for the Z32 mafs. I'm running 9psi of boost right now, but when the external wastegate opens, it acts like a rev limiter, and I can't rev past that point. The RPM is usually around 4000-5000rpm at that point. Its VERY annoying as you can imagine. If I don't apply full throttle (maybe around 1/2 to 3/4 throttle) I can rev all the way to the rev limiter which I have set at 7100rpm on the power FC. I set the power FC for the Z32 mafs also, and it seems in working order, as I have a steady idle, and no driveability issues (only the full boost issue). Now what I am wondering is that I don't have the stock RB boost sensor that connects to the ECU harness. I'm not sure if the Power FC needs this to work properly, but I have heard from people I don't need it. Also i'm not sure if the Mafs might be messing up at higher airflow. I checked my vacuum schematics for the BOV and wastegate, and they are ok. Also, the motor used to be an AUTO, and I converted to 5spd, not sure if that has anything to do with it. I know that the TPS had two different sensors, 1 for the throttle position, and one for the full throttle/closed throttle switch (for auto trans I think?) Now i'm wondering if anyone else has had any issues like this? I did a sensor check on my Power FC and all the sensors are working that I need. Any ideas? Hashiriya S13? any advice is welcome.. thanks! :pface Here are some pics of my car...



Mark Slide SquadTurbonetics Inc.

[kevie88]

I have no answers for you but I know this:

Your car owns.

[thephatone]

omg that is a beautiful car...wait your in THOUSAND OAKS? did you do the swap yourself???!!!! please let me know!!!! i live in northridge and soon to do an rb swap!!!

[Nameless EJ6]

I think it does need that boost sensor... I'd give it a try and report back to us. I'd like to know because I intend to run the same management on mine and I do not want that issue.

Can you also give more information on the wiring for the VTC, 02 heater, and AIV? Why would people not be running this stuff? That stuff is a must. I'd like to know what you had to do though to ensure that these sensors were powered correctly..

AND - can you tell me what all intercooler piping you are running? I like it ALOT. That'd be gnarly!!

One last thing. Your sir have the NICEST RB25DET powered 240 I've seen yet! good job.

[JonPowell]

The factory boost sensor just goes straight to the gauge cluster. I tcouldnt have anything to do with the problem. I would just double check all your wiring, I am sure it is in there. Maybe the computer thinks for some reason that you are in 3rd or 4th from the auto...I belive that there is a limiter to stop the car from going over 180KM/HR. Must be that, the computer thinks you are in one fo the top gears. I run the auto ECU with the 5 speed trans and the only issue I have is that I run diagnostics and have a code stored that it cant find the trans.

On another note...Bastard, you stole my wheels!

Car looks awesome, hope you get it figured out.

[rbsileighty]

Yes sir... I'd have to agree nice car.

As far as your problem, I'd imagine you sould be running some type of boost sensor on your car regardless... in some shape or form. I would contact Apex and see what they use. Forums can be lots of help... but sometimes you have to hear it from the horse's mouth.

I've had great support with HKS over the phone, and while I have spoken with Apex over the phone a couple of times, they have also been very helpful those few times.

Aftermarket ECU's typically at least come with their own sensors if they don't use the factory ones. Did you buy your Power FC new?

Are those GTS or R32 GTR wheels? I always wondered how they'd look on our cars... very nice bud. Clean work. What do you think of the boost characteristics with the TO4E? That trim should spool pretty decent w/ the BB center section I'd imagine.

Hope this helps.

Oh... and if it's not the boost sensor, do you think you might be running a wastegate that is to big? Correct me if I'm wrong, but if you only have a problem when it opens, then maybe it's venting too much exhaust gas and quits spooling the turbo in the high rpm's... which would make it quit making power and quit pulling up in the r's I would imagine. Just a theory... could easly be wrong.

[PROJECTRB240SX]

THE BOOST SENSOR IS NOT NEEDED ( IT RUNS TO THE GAUGE CLUSTER THAN THE ECU - FOR LIMITER PURPOSES). IT SOUNDS LIKE A TPS PROBLEM IF YOU CAN DO IT AT 3/4 THROTTLE BUT NOT FULL.

[Nameless EJ6]

eh. I hope he comes back soon, I'd like that info...

[rbsileighty]

THE BOOST SENSOR IS NOT NEEDED ( IT RUNS TO THE GAUGE CLUSTER THAN THE ECU - FOR LIMITER PURPOSES). IT SOUNDS LIKE A TPS PROBLEM IF YOU CAN DO IT AT 3/4 THROTTLE BUT NOT FULL.

"If I don't apply full throttle (maybe around 1/2 to 3/4 throttle) I can rev all the way to the rev limiter which I have set at 7100rpm on the power FC."

Yeah... sounds reasonable to me too project... Might have helped if I read more carefully. If you have an extra sensor laying around might be a good idea to try it. Anyone know if the TPS is interchangeable between the 20 and 25? If so... might be able to help you out.

Ok... after reading some more... this is where I was coming from with the boost sensor part. When you say it needs no boost sensor, you mean it doesn't need the stock boost sensor correct? The Power FC has it's own internal sensor I would assume.

My logic is coming from RX7 tuning when installing Haltech and Microtech standalones. When installing these you get rid of the stock sensor, but not monitoring boost all together. It's been a long day...

Might be a bad sensor... or better yet, the Power FC is somehow reading the signal wrong.

[JonPowell]

The TPS sensor is adjustable, might be in that. The computer knows boost based in air flow, oxygen in the exhaust and rpm. The ECU does not actually monitor "boost"

[95silvia]

first ... welcome to the nico rb board next ... the boost sensor is not the cause of your problem... Id put my 10 bux on the wastegate and the vacuum lines going to it. make sure its not split off of anything else. I had a simmular problem on my old 450 hp sr20 set up the the tial 40mm. hope it helps ... again just like on FA love your car, even tho it makes mine look pathetic.... lol good job just fix those radiator brackets... stay sideways Cjex

[mark slide squad]

Thanks for the positive feedback guys

The Phatone.... yes I am in Thousand Oaks, and yes I did all my own work, from the custom fabrciation like the crossmember, motor mounts, trans mount, intercooler pipes, extension pipe, and also body work and paint. Only thing I didn't do in the whole project was the driveshaft, I had a shop make that. You are in Northridge? I used to live there not long ago heh.

For the wiring on the VTC, 02 sensor heater, and AIV, all three of those get power from one wire. The wire is blue with a white stripe, and its a wire that is connected on the white smaller dash plug, where you cut the wires for the fuel pump relay, ignition and so on. The car runs smoother and idles smoother, and gets better gas mileage with the these items working, that I noticed.

I don't think it needs the boost sensor also, because my friend has Power FC in his S13 SR and it doesn't need it. The power FC doesn't use a boost sensor as such from what I hear, just needs the airflow signal. Thats why I'm wondering if my MAFS is bad.

The TPS, I checked this and its ok. its running .49v on idle, which is in factory spec, and at WOT its running 4.04v, which is also right on the money.

All the wiring for the auto trans has been removed from my harness, and the power FC is for manual trans only, I double checked all the wiring and its A OK..

Its not a speed limiter problem, because the Power FC displays your speed in KM on the FC commander, and the speedo reads slow anyways, says i'm going around 40km an hour when i'm going about 75mph hahah

RBsileighty, they are indeed R32 GTR wheels, 16x8 +30mm offset, they have always been my fav OEM nissan wheels

Oh 95Silvia, I also thought about the vacuum line diagram for the wastegate, and I tried every option with the vacuum lines, and I have it set up as other people with RB's, and still no dice..

I just had a thought though... I have Bosch platinum +4 plugs ( the type you can't gap because it has 4 electrodes) and I have a feeling I could be blowing out the spark... I'm going to put in different plugs and see what happens, and gap them at .030 too.

I appreciate all the brainstorming guys! I always believe in getting a 2nd, 3rd, 4th.. etc opinion heheh. Thanks guys

I have no answers for you but I know this:

Your car owns.

[thephatone]

I was wondering if you were interested in doing another swap and you did the body/paint also? are you from heaven? haha, lmk

[Nameless EJ6]

I just had a thought though... I have Bosch platinum +4 plugs ( the type you can't gap because it has 4 electrodes) and I have a feeling I could be blowing out the spark... I'm going to put in different plugs and see what happens, and gap them at .030 too.

Those +4 plugs are nightmares.. I'd ditch those right away. Alot of people have little issues with them, including me. I absolutely hated them when I ran them in my ITR engine. I decided to give them a try for a week, and switched back to my NGK platinums.. never had any problems with NGK's.

And hey! Would you be interested in making some more of that intercooler piping?? I'd pay! It looks very quality.

[rbsileighty]

This might be helpful:

"I RUN IN MY RB25DET,VL TURBO COMMODORE SPARK PLUGS AND THEY SEEM TO DO THE JOB AND ARE A HELL OF A LOT CHEAPER THAN THE GENUINE PLATNUM NISSAN PLUGS.IF YOU INTEND TO RUN A HIGHER BOOST PRESSURE BEST TO GAP THE PLUGS DOWN TO .8mm - .9mm RATHER THAN THE STANDARD GAP OF 1.1mm TO STOP BLOWING OUT THE SPARK WHICH HAPPENS WHEN YOU INCREASE THE BOOST.I HAVE A FREIND WITH A R32 GTR RUNNING UPTO 22 POUND BOOST AND HAS HAD NOTHING BUT PROBLEMS WITH THE GENUINE NISSAN NGK PLUGS AND HAVE HAD NO PROBLEMS WITH THE NON PLATNUM NGK VL TURBO PLUGS.AT THE COST OF THE NORMAL VL PLUGS WORTH GIVING IT A GO. Regards, Daz."

We run copper NGK's w/ gap of .8mm on Hyprid's motor (my old motor). I got the part number and gap rec from Motorex.

Hope this helps.

[PROJECTRB240SX]

AUTOLITES WORK ALSO. PLATINUM WITH QUAD ELECTRODES ARE NOT GOOD FOR TURBOS. THE AUTOLITES SHOULD BE GAPPED TO 80 THOUSANDS. HAVE YOU CHECKED COILS? OR COIL WIRES? DOES THE PFC HAVE A LEAN CONTROL LIMITER? BECAUSE IF AT FULL THROTTLE IT MAY BE LEANING WAY OUT AND IF THIS SYSTEM HAS ONE IT COULD BE SHUT THE ENGINES POWER DOWN TO PREVENT DAMAGE. I'M NOT TO KEEN ON THE PFC SO I DON'T KNOW MUCH ABOUT IT BUT I KNOW ALOT OF OTHER SYSTEMS HAVE THESE.

[mark slide squad]

OK well I just switched my plugs out, to NGK BCPR5REIX-11 iridium. They are gapped at about .030" and it STILL has the same problem! It didn't make any difference. At around 5800rpm it just started misfiring like a revlimiter basically. On the Power FC commander, it peaked at 4300mv on the MAFS, and 75% injectors, 46 degrees of timing, at about 5800rpm. I am about to switch out the MAFS for another Z32 to see if that is the culprit. Thanks again for the ideas guys..

Mark

This might be helpful:

"I RUN IN MY RB25DET,VL TURBO COMMODORE SPARK PLUGS AND THEY SEEM TO DO THE JOB AND ARE A HELL OF A LOT CHEAPER THAN THE GENUINE PLATNUM NISSAN PLUGS.IF YOU INTEND TO RUN A HIGHER BOOST PRESSURE BEST TO GAP THE PLUGS DOWN TO .8mm - .9mm RATHER THAN THE STANDARD GAP OF 1.1mm TO STOP BLOWING OUT THE SPARK WHICH HAPPENS WHEN YOU INCREASE THE BOOST.I HAVE A FREIND WITH A R32 GTR RUNNING UPTO 22 POUND BOOST AND HAS HAD NOTHING BUT PROBLEMS WITH THE GENUINE NISSAN NGK PLUGS AND HAVE HAD NO PROBLEMS WITH THE NON PLATNUM NGK VL TURBO PLUGS.AT THE COST OF THE NORMAL VL PLUGS WORTH GIVING IT A GO. Regards, Daz."

We run copper NGK's w/ gap of .8mm on Hyprid's motor (my old motor). I got the part number and gap rec from Motorex.

Hope this helps.

[JonPowell]

46 degrees seems a little excessive , doesnt it? Is it timed right? What is your timing at idle? should be between 15 and 20 degrees, my car LOVES 20 degrees. Try that...

[mark slide squad]

46 degrees was not at WOT or idle, it was just cruising peak timing, i'm using the stock timing map that the power fc comes with from factory. Well idle is 15 degrees. I even tried putting it up around 20 and no difference. I JUST got finished switching out the MAFS with another Z32 unit, and NO difference! BUT one thing I did notice, it seems like the intake manifold gasket (where the upper plenum meets the lower plenum) has a leak, if you put your hand there you can feel a lil bit of air, and you can hear some kind of vacuum leak. SO instead of fixing the stock manifold by getting a new gasket and blah blah blah, i'm just going to put on a surge tank style intake manifold this week. This could be the problem, if the gasket isn't sealing at full boost, and basically it will run too rich and start to misfire, i'm HOPING this is the problem because i'm really running out of options here. Arrrrgh..

46 degrees seems a little excessive , doesnt it? Is it timed right? What is your timing at idle? should be between 15 and 20 degrees, my car LOVES 20 degrees. Try that...

[JonPowell]

Yeah...that might be it...I had a small boost leak when I first got mine running, but it was problematic at 1/2 throttle, 3/4 throttle...whenever I was above 2500-3000 RPM. My problem was in the same spot. I would put some soapy water around all the joints in your intake tract and see if any bubble come up when you give ti a little throttle in neutral. You may not reach FULL boost, but you WILL find your leak. Have someone follow you and see if you get alot of black smoke out the back. That will tell you if it is running too rich.

It is misfiring and not detonating, right? Youwanna be careful there. I have heard of the CAS causing problems also, check and see that the stem is not bent or anything like that...I dont know much about the Power FC...is that a piggyback? If so, run diagnostics on your stock computer and see what codes you get.

[leroy0053]

hey man just a quick question, what injectors are you runnin

[dareo]

i just gotta say, wow man. I really like your car, its gotta be the cleanest setup i've seen yet. You've even got a Power FC going on, i must say im a bit envious. The pics of your car are so sweet i dont even remember what your post was about anymore.

[leroy0053]

love ya car man. but if u got a front bumper like we have over here (japan) holy **** your car would look so much more aggressive shoot me a email at [email protected]

[mark slide squad]

UPDATE! the problem has been fixed!! :ylsuper Well turns out the vacuum leak on the intake manifold was actually a small pin hole in the vacuum line for the fuel pressure regulator, fixed that. Then I took the plugs out, and regapped them to .74mm (.029") and then took the coil packs out, one by one, and cleaned the contact point where it touches the top of the spark plug. I used a rotary wire brush tool for use with a dremel. It cleaned them all up very nicely. Then I got some minor corrosion off the alloy plate that the coil packs bolt to, by sanding it lightly with 400 grit sandpaper. I also wanted to ensure a good ground of the coil packs, because I have heard that on RB's it is a problem of the ground being weak, and that leads to ignition probs such as misfires. I made a ground strap wire and secured it to the #6 coilpack bolt (the 8mm bolt that goes to the alloy plate) and then secured the other end of the wire to the firewall. After all that, the problem was fixed. Now it goes right up to the rev limiter ( I have it set for 7100rpm on the power fc) and it spins the tires no problem into 3rd I'm maxing out my stock injectors (370cc) and that means I gotta drop in my Tomei 555cc injectors that are sitting in my garage pretty damn soon! Right now i'm running 12psi on my Turbonetics T04E 50 trim ceramic ball bearing Stage 3 turbo. It seems to be a PERFECT size trim for my application, with power all through the power band. With my calculations, at 12psi and the stock injectors maxed out, its probably making about 350-370hp. Once I put in my bigger injectors, and greddy intake manifold, i'll get it dyno tuned, at higher boost. Thanks again guys for all your input on this situation, i'm just stoked I can actually go full throttle now! woo hoo! Mark

Yeah...that might be it...I had a small boost leak when I first got mine running, but it was problematic at 1/2 throttle, 3/4 throttle...whenever I was above 2500-3000 RPM. My problem was in the same spot. I would put some soapy water around all the joints in your intake tract and see if any bubble come up when you give ti a little throttle in neutral. You may not reach FULL boost, but you WILL find your leak. Have someone follow you and see if you get alot of black smoke out the back. That will tell you if it is running too rich.

It is misfiring and not detonating, right? Youwanna be careful there. I have heard of the CAS causing problems also, check and see that the stem is not bent or anything like that...I dont know much about the Power FC...is that a piggyback? If so, run diagnostics on your stock computer and see what codes you get.

[Nameless EJ6]

That's awesome to hear!

Now with that out of the way, I have a question. =P What have you done with the PFC to feel safe enough to run 12psi?

I will be running PFC as well.. but any input you have on it I would appreciate.

[thephatone]

hey mark, is there anyway possible you can do my swap? sometime in the next 3 months or so? and of course your getting paid to do so...let me know

[solarex]

you gotta post a vid of this car in action lol; beautiful work. can you post some pictures and maybe elaborate what you did to the crossmember and mounts. just food for thoughts, until i my motor come in.