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matausi

SR20DET boosting problem

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Hi all,

 

Another SR20DET boosting problem thread

 

Have just done a det swap into my S14

 

FMIC, new Walbro 255 fuel pump, 3" dump pipe to stock S15 front pipe to full 3" exhaust, stock injectors, t28BB

 

 

Engine was boosting fine in the 180sx that it came out of before hand

 

Problem is that it is struggling to boost from low rpm (2k - 5k rpm) - I've driven numerous t28s and know they dont take this long to spool. At full throttle it feels like it is a SR20DET running with no turbo at those rev ranges. At 5k it fully opens up and boosts normally

 

Currently have replaced plugs with BKR6E 0.8 pregapped, replaced coils with another working set. Same issue

 

 

Need to do a boost leak test and hook up a working boost gauge to check more symptoms but starting this thread now to get ideas on what it could be

 

Idles perfect also - so there is definitely no vacuum leak right?

 

Turbo cant be rooted as its not smoking, leaking and making boost from 5k onwards right?

 

Could it be wastegate flap faulty/actuator, FPR, or something along the lines?

 

Any input is welcomed and listed as much details as could come to mind

 

Thanks all,

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I noticed your using bkr6e spark plugs, just wandering how much boost your running at the moment.

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Also the stock s15 front pipe will be a restriction compared to the rest of your exhaust system.

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Stock boost, stock actuator no EBC.

 

Yeah the S15 front pipe should hold stock boost though right, since its part of the stock setup? or would having a bigger dump pipe then going to a more restrictive system be a huge difference

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Might be in limp mode, does it bog right down and in that 2-5k rpm range, almost undriveable?

 

The turbo can still be rooted and not blow smoke.

 

Id be looking at afm, knock sensors, tps.

 

 

A vac leak tester is easy to make. Go to bunnings and buy a pvc round cap the size of your intake tube, drill and tap a hole, use a bike bump kit with schraeder (spelling?) valves or similar and head on down to your local servo with a spray bottle filled with soapy water.

Set compressor to 15psi and spray for leaks, including the entire cooler core.

Edited by r0berto

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Not undrivable in those rev ranges. Just not creating boost i believe, will check properly when I hook up the working boost gauge.

 

Its still making boost after 5k though (just also have to make sure its not free boosting)

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Sounds Exactly like what was happening to mine. End up being the Knock sensor, which I just bypassed with a resistor, PM me if you need help with that

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Sounds Exactly like what was happening to mine. End up being the Knock sensor, which I just bypassed with a resistor, PM me if you need help with that

 

Having a read of it,

 

If I did a diagnostic scan again would it show up as a faulty knock sensor? Seems like it doesnt work past 4k which is what im experiencing?

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I had the exact symptoms your describing when I first got my s15. No boost till 5k rpm. Ended up being the wastegate not closing. There's a little spotweld on the sleeve of the waste gate arm and they do crack sometimes which then allows the sleeve to get loose and consequently the wastegate puck fouls against the inside wall of the housing. I had two t28's and it happened to both. The fix was to tap the sleeve back in an re weld the spot weld.

 

To check if this is your problem, take the actuator arm off the wastegate arm and see if the spotweld looks intact. It will be clearly noticeable if it isn't.

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I had the exact symptoms your describing when I first got my s15. No boost till 5k rpm. Ended up being the wastegate not closing. There's a little spotweld on the sleeve of the waste gate arm and they do crack sometimes which then allows the sleeve to get loose and consequently the wastegate puck fouls against the inside wall of the housing. I had two t28's and it happened to both. The fix was to tap the sleeve back in an re weld the spot weld.

 

To check if this is your problem, take the actuator arm off the wastegate arm and see if the spotweld looks intact. It will be clearly noticeable if it isn't.

 

So just take the actuator off pretty much?

 

Do you have a photo of what this spotweld looks like

 

Thanks

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Yep knock sensor only works from around 4-5krpm and below.

 

Just undo the clip near the injector rail and measure the resistance. If its Open circuted that should be it

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2sCbN8i.jpg

 

Is this right for it to be slightly angled? does that mean the flap is a bit open?

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Yes looks to be open a bit. They usually sit straight up when closed. All your issues definitely sound like a open wastegate flap

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Would a new actuator fix this or do i need to spot weld the flap again?

 

Best to remove the dump pipe off the turbo so you can verify that the gate isn't shutting and what's stopping it. If it turns out to be the spot weld I referred to earlier you just need to tap the sleeve back into position with a hammer so the spot weld is lined up and then re tack it. Then enjoy low rpm boost.

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This is the weld you are looking for. This picture is of a repaired weld on a t28 that I found by Googleing.

turbo2.jpg

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Car should still build boost fine with a f**ked knock sensor, actually seems to boost a bit quicker because of the retarded timing, just there's just no power down low

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So last night, I did a few things

 

- Took the actuator arm off to check the gate flap is opening and closing. That position in the above picture is fully closed

- Checked TPS - 0.4ish closed, 4ish fully open - this seems normal

- Checked AFM - clean as a whistle

- Checked spark plugs after putting in, slightly white tips which means its leaning out when im hitting that 3 - 4k rpm?

 

Was looking it over with a friend and definitely feels like its misfiring. Its just hesistant under load around that 3 to 4k mark then fully opens up

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the wastegate does not have an adjustable arm, so your preload cannot be applied. if the wastegate is held open a bit this can add to some fluctuating.

 

spark plugs should be .8mm as per the maunal if its stock cams turbo etc.

 

for a stock car i rate the platnum plugs, i got 120000 kms out of the stock ones! they were still going good but thought best to change them anyways.

if anything change to a 7 heat range if your running 15psi. but i never had to, the stock 6 heat was fine.

 

you could have a number of small issues to go track down, that could be compounding.

look over all vacuum lines - replace them all to rule out any issues. buy a roll and cut to suit.

check the pcv / replace it.

check every intercooler hose for pinched / cut hoses. pull the front bar to check it out.

iits unlkley but your fpr could be f**ked (mine flogged out so it does happen but its uncommon)

injectors could be not so happy either! if not fouled slightly.

have you changed your fuel filter?

 

white means its leaning out yes. and probably a bit too much, that could very well be your hesitation as well. if its too lean coming on, it will jerk and carry on.

are you using the DET s14 engine ECU? or a tuneable one?

Edited by n0nac-S15

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Yeah I have BKR6E 0.8mm pregapped iridiums - shouldn't have any problems with these plugs.

 

I'm going to try another set of working coils from a friends car which is also running an identical setup and swap coils between them to rule out the off chance i've got another faulty working set.

 

I need to change fuel filter - only changed the fuel pump in the rear.

 

This weekend I'm planning to do a boost leakdown test by pressurising the system - hopefully this will identify any split lines or cracks on the joiners. I have visually gone through them a few times and haven't found anything noticeably leaking.

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If it is misfiring, maybe check that your earth leads have good contact?

I was reading in one of the VET build up threads where at one point a misfire was caused by a loose earth lead.

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If it is misfiring, maybe check that your earth leads have good contact?

I was reading in one of the VET build up threads where at one point a misfire was caused by a loose earth lead.

 

Checked the earths on the intake, behind the 4th coil, turbo side earths look fine,

 

Its weird this misfire is only at 3 - 4 k and it isint a jerky one , it just slowly hesistates till 5k and fully goes fine again.

 

Swapped coils with working ones from a S15, boosted fine in the s15, and still same problem in mine.

Unplugged AFM - idled sweet without it, and plugging it in dropped idle and rose back to normal - All indicating my AFM is sweet - unless something happens under load?

 

Unsure what path to go now

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Did a boost leak test up to PSI to pressurise the system and found a couple of leaks which has been all tighted and nothing seems to be seeping out now. Still has the misfire

 

Replaced the fuel filter and the bottom fuel line was kinked so replaced that - thinking this could be why it might be leaning out because fuel isint being delivered properly. Still same symptoms

 

I'm leaning towards a electrical problem now,

 

I took pictures of this:

 

We believed these are the ABS plugs only and hence have left them unplugged (and they don't plug into anything anyway)

 

yxpru0jk.rm2.jpg

 

gf02gnvf.5a1.jpg

 

The ECU side, fully plugged in and a couple of loose plugs (any idea what they are?)

 

uqn5eije.xc5.jpg

 

 

Overall the car turns over every time, idles perfectly, comes on boost at 6k properly and just has this misfire at 3000 4000 rpm

 

Any help is appreciated , I will be looking to take this to someone more knowledgeable but looking to just throw ideas up on the drawing board

 

Thanks guys

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well your on the right track i guess.

 

might be relevant :

i recently had my newly purchased car running...ran fine day1...day 2 would run fine under half throttle...any more would kick and sputter and sometimes do as your car does and run fine toward redline.

shitload of diagnostic like yours, couldn't fault it,

replaced coils / spark plugs, clean AFM, leakdown test, ecu & even the ecu data log said everything's ok.

 

put in a fuel pressure gauge, but was in the engine bay. Idle pressure was correct, and would rise with more throttle (as it should) but the gauge fluttered around -2 / +2 psi each way while idling - thought it was just china finest shitty quality gauge (was $8)

figured everything was fine so went looking elsewhere.

 

removed any potential PVC air leaks by blocking the system off

removed injectors and manually fired them to test a visual on spray pattern / leaks

and more shit

 

couldn't fault it, so replaced the fuel pump cause i had a brand new one to go in anyway.

Fuel pressure was rock solid on the gauge and the car ran better than it ever had in its life.

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I have installed a brand new walbro fuel pump to replace the original sr20de that was in. After replacing, it primed and started fine, which indicates the install wasnt cocked up ?

 

 

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what ecu are you running? if stock, should be ok. if aftermarket, get your tune looked at.

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Car should still build boost fine with a f**ked knock sensor, actually seems to boost a bit quicker because of the retarded timing, just there's just no power down low

 

This.Mine would do this before I had it Nistuned and my boost gauge would always keep going up well past where my EBC was set to until about 5K then the timing would be corrected and it would launch like a rocket.

 

so while it feels like its not boosting, boost is building very rapidly just not being utilised.

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Ended up being afm. Im using my sr20de afm which is a 52f not a 62 or was it 69f

 

Now its driving like it should.

 

Is there a difference in de and det afm for s14?

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