S2 Stagea Boost Problem

[morm]

I have a 2000 s2 stagea. Most of the time it boosts well(over 1/2 way on gauge). Intermittly something happens and the boost doesnt even reach half way. The MI light doesnt come on(light is working). The car has no known mods. I have swapped the boost sensor, AFM with my r34 skyline. I have also replaced the plugs and visually checked the coil packs. Any Ideas please?

[KiwiRS4T]

Check all the hoses to and from the solenoid/boost controller/actuator etc. is it possible that the wastegate is sticking open?

[morm]

Check all the hoses to and from the solenoid/boost controller/actuator etc. is it possible that the wastegate is sticking open?

I posted a bit of wrong info, normally over 3/4, when fauts under 3/4. Have had a good look at hoses.

[lachlanw]

mine did that ocasionaly standard apart from cat back . is your a manual ? standard 10 psi all the way through rev range? it did it twice . usually when i had boosted all the way through 1-3 and was winding out 4th and it would like "boost cut" and only run half boost untill i turned car off and restarted it . engine light fould flash right when it did . flash once . checked codes and it gave me "55". boost was not very stable with standard controller tho . hasnt doen it once with fmi and ebc set to 0.65 . didnt even do it when it went to .9 bar during tuning of ebc

[morm]

mine did that ocasionaly standard apart from cat back . is your a manual ? standard 10 psi all the way through rev range? it did it twice . usually when i had boosted all the way through 1-3 and was winding out 4th and it would like "boost cut" and only run half boost untill i turned car off and restarted it . engine light fould flash right when it did . flash once . checked codes and it gave me "55". boost was not very stable with standard controller tho . hasnt doen it once with fmi and ebc set to 0.65 . didnt even do it when it went to .9 bar during tuning of ebc

yes, rs4s. No engine light though. Got 55 code same after reset. Havent found if it shows code when happening. sounds very similar tho.

[pixel8r]

Check HERE for a list of fault codes.

lachlanw - your "boost cut" issue is related to your cat back exhaust. Standard boost is 7-8psi on a s2. An exhaust will raise this figure and this means more airflow...which may mean your AFM is then reading outside the preset range the ecu wants it to be, so it cuts fuel to protect the engine. To fix that, you need some form of tuning, be it as simple as a Apexi SAFC, or as full-featured as an E-manage. Nisstune is another option.

morm - if your exhaust is standard, then its unlikely to be the same issue as the above, and you wouldn't be experiencing the boost/fuel cut issue. Check your vacuum hoses etc...

Also be aware that the standard boost solenoid will keep it at 5psi until you reach 4500rpm and then it will jump up to ~7.5psi above that. Also I believe it will limit boost in first gear so you may not see the 7.5psi until 2nd gear. If you want to run 7.5psi all the time (you do, trust me) simply earth the black wire from the boost solenoid (this is a small vertical cylinder thing attached to the chassis near the passenger side strut - it has a red and a black wire coming off it into a plug). By this I mean so that the black wire connects the ecu to the chassis instead of connecting the ecu to the solenoid. I'm pretty sure thats right - its been a year and a half since I had my s2. If in doubt cut the black wire after the solenoid plug and earth both ends... Its a good idea to make sure you can reverse the operation later so dont cut it too short.

This little wiring trick causes the ecu to keep the solenoid on "high boost" mode all the time, instead of just after 4500rpm. Unfortunately it means you'll be running more boost between ~2000 and 4500rpm than you were before so your fuel usage will increase. It wont increase your peak power.

[mattye]

Autos run 5psi then 7psi (ie. dual stage).

Manuals run 7psi constant.

[jrm]

Weird, wonder why they're use a different setup to R34 (or even auto to manual stagea). That'd require a different wastegate actuator to run the 7psi all the time, etc wouldn't it? .. Unless they just bleed 2psi, but that just seems a bit silly ...

[morm]

I disconnected the plug that goes to the bleed solenoid and that is where the boost is (level on the gauge) when the fault happens. The car s s s2 rs4s (manual!) with factory everything as far as I know. My laptop is away for repair so I cant check codes while car is running. Easiest way to reproduce fault is om open road when in 5th and to accelerate. The first two times the car will accelerate ok, on the third the boost is limited and need to cycle the key to get it to run well again. We have only had car for a short time(>5k kms), dont know much else of the history.

[mattye]

Weird, wonder why they're use a different setup to R34 (or even auto to manual stagea). That'd require a different wastegate actuator to run the 7psi all the time, etc wouldn't it? .. Unless they just bleed 2psi, but that just seems a bit silly ...

Stageas use a solinoid to limit the boost to 5psi. When u do the solinoid earthing mod it in essence makes the solinoid redundent.

[DaveB]

aaand of course, better to take the solenoid out-of-circuit all together I guess, rather that having it on all the time... I just bypassed it with a 4mm-4mm barbed fitting.

Careful though - if you don't make a good connection, and boost leaks out... you'll get over-boost or worse still 'infinite' boost!

[DaveB]

Weird, wonder why they're use a different setup to R34 (or even auto to manual stagea). That'd require a different wastegate actuator to run the 7psi all the time, etc wouldn't it? .. Unless they just bleed 2psi, but that just seems a bit silly ...

I don't know but I'm guessing that in the manual stageas the ECU wouldn't know what gear you're in? (unlike the auto, where the auto ecu sets the gear) therefore no boost limit in gears... except probably reverse (that has a switch and I think a connection to the ECU).

[pixel8r]

Does the manual one not run the boost solenoid then? otherwise what does the solenoid do in a manual?

In the threads relating to the boost solenoid earthing trick, it was discovered that bypassing the solenoid altogether did not have the same result as earthing it. Something to do with the solenoid still having a restriction in it even when its open. If you bypass it by joining the hoses together you may end up with 10psi or even more.

The standard actuator is set at 5psi. All the solenoid does is bleed the extra 2psi pressure away from the wastegate, effectively giving you ~7psi. The solenoid is either closed (5psi) or open (~7psi). If the manual is indeed 7psi all the time then it means the solenoid is always open.

If you do get sick of the whole boost solenoid thing, search on this forum &/or ebay for a "turbotech" boost controller (NOT JRD or anything else!). They're cheap and reliable and you can set the boost manually and remove the boost solenoid completely. They will also allow your turbo to spool up faster too I had one on my previous stagea (s2) and it worked a treat!

The problem you're having could be related to the wastegate actuator, possibly a weak spring? or it may get stuck open...which would mean you'd have almost no boost, or if it did build up it would only build slowly...(i think)

[KiwiRS4T]

Here is the solenoid bypass (this will eliminate the ecu as a cause and also allow you to run 10 psi all the time):

This is the 10 minute no cost boost to 0.5 bar rerouting of the vacuum hoses [thanks to SK]. Disconnect the two vacuum hoses from the solenoid. Then connect the boost feed (from the cross over pipe on the left of the picture) to the standard T piece. Connect one side of the T piece directly to the wastegate actuator (on the right of the picture). The remaining connection on the T piece goes back into the inlet via the BOV return pipe (on the standard fitting). Make sure to put the standard brass restrictor in that vacuum hose to bypass the desired amount back into the turbo inlet. The standard bypass hole of 1.25 mm bypasses enough air flow for 0.5 bar. (See photo)

PS: If you want more boost you can drill out the bypass, 1.5 mm = more boost (around 0.7 bar) 1.75mm = a bit more (around 1.0 bar).

[photo in post #40 http://www.skylinesaustralia.com/forums/Ja....html&st=20]

OK, this is the picture of the vacuum hoses. The boost pressure comes out of the intercooler return pipe (that's the big black one on the left) via the standard fitting. It travels down the vacuum hose to the standard T piece.

The right hand side of the T piece goes to the wastegate actuator via another short piece of vacuum hose. It has 2 standard spring clamps on it. So that "some" of the boost pressure goes to the wastegate actuator.

The left hand side of the T piece is connected to another (longer) piece of vacuum hose that goes to the standard fitting on the BOV return pipe. You can't see that fitting in the picture as it is hidden by the (big black) turbo to intercooler pipe. I squeezed the standard restrictor into that vacuum hose, it is tight fit, so be patient and use some lubricant (RP7 in my case).

The restrictor limits the amount of boost pressure that is bled off, so that the "some" pressure that goes to the wastegate actuator is actually less than the boost pressure. This means you get more boost before the wastegate opens at its usual 4-5 psi. How much more depends on the size of the hole in the restrictor, the bigger the hole the more it bypasses and the higher the boost.

The standard hole is ~1.25 mm and gave ~0.5 bar on my Stagea, which has standard everything else (no exhaust, no FMIC, std filter, etc). If you have mods, you may not get the same boost pressure, so you may have to adjust the size of the hole in the restrictor, it is brass so you can easily solder it up and redrill the hole smaller if necessary.

[lachlanw]

i think anyone who doesnt own a rs four s should mind their own business as half of this post is a discussion about the diff between a s and a rsfour .

i have followed nissans flow chart for symptoms and diagnosis and ya cant really narrow it down much by those symptoms . nah its weird ive never heard or had one "boost cut" it not like a normal boost cut either . doesnt throw you through the windscreen more like a bad miss fire . and car never did it running 12 psi

[lachlanw]

"The powerplant is the RB25DET as introduced in the R33 GTS25T. In R34 form, however, the engine is upgraded to more environmentally friendly 'NEO' specs. The NEO RB25DET also features a hot-wire airflow meter, 9.0:1 static compression, air-to-air intercooler, ceramic turbine roller-bearing turbocharger, blow-off valve and variable inlet cam timing. With manifold boost pressure of around 60 - 70 kPa (as shown on the factory boost gauge) the R34 25GTt is listed at 206kW at 6400 and 343Nm at 3200 rpm. The R34 25GTt scores its extra power over previous models thanks to a larger turbo (providing a healthier amount of boost), better intercooler, an improved exhaust system and engine management updates."

[lachlanw]

yo should bet a proper boost gauge aswell . would help this problem . even jus borrow one . my car ran 0.7 kgfcm2 (10.2 psi) with just a cat back exhaust . still has standard cat and front pipe

[BensDR30]

FYI a code 55 is no errors.

Hook up a reliable boost gauge and do some tests. A cat-back will not affect the boost by very much at all - the wastegate will still open at the nominal pressure, but the turbo may reach that pressure sooner, and maintain it longer.

DO NOT just bypass the boost solenoid (if present), because you will overspeed the turbo, and risk detonation (destruction!?).

The '10 minute boost mod' is the safest boost upgrade available for the dual-stage vehicles. A Jaycar IEBC or PROFEC is the go for mappable boost control. But GO EASY, and get the wellbeing of the car monitored via Wideband O2.

And since we're talking about an S2 RSFS, getting a NisTune is your best programmable ECU bang-for-buck.

[morm]

By removing the plug I meant the electrical plug. The fault does not thow you thru the windscreen. It just makes the car feel sick. From my understanding for this sort of fault it should throw me a fault code to go into a boost cut or 'limp' mode. I just hoped that someone had a similar experience, and had fixed not overcome the problem. Thanks everyone for the advice so far tho!

[morm]

Also the fault is not just occuring whilst on boost. I took the car for away last weekend. Whilst cruising(110km/hish) it can occur so when I went to overtake there was reduced boost!

thanks again for your ideas!!!!