sr20det fuel cuts at 6k after external added

[blitza]

so there is this s14 that a guy I know has, was non turbo, but added all the exhaust side bits off a det engined car, and a microtech extra injector controller....... runs fine, been tuned on a dyno, ran it at 6psi consistently, however has run 10psi.(std DE internals seem up to it)

now the interesting part, I fitted an STA exhaust manifold and external w/g to the thing, (have fitted exactly the same combo to a DET engined s13) the boost is a lot smoother, better controlled (8psi), sounds great, however it cuts out at 6krpm in third. fuel cut I think.

the usual scenarios;

fuel pump not up to it/leaning out?
It still has the std non turbo pump and all, but watching the a/f gauge, it stays well rich till just when it cuts, which is when it shoots off to lean, I suspect the nissan ECU is cutting the fuel for some reason at that point, as it is a sudden leaning, not a fading away as you would expect from a fuel flow problem.

bung plugs/leads?

As it only does this at w.o.t / full load the above could have been faulty, but it is a pretty violent cut, not an induced miss and accompanied richening as you would expect with an ignition problem.

the only remaing problem really is electrical, no welding was actually done in the car so nothing should have been 'spiked', so my remaining theory is this........that the noise from the wastegate opening at full throttle is interferring with the knock sensor at 6k, causing the factory ecu to create a fuel cut situation. As the cut only occurs under full boost, 8psi atm, this is the smartest thing I can conclude till further testing can be carried out...

your thoughts??

[blitza]

+ the ecu has been 'reset' (power remooved all weekend)

[CozmoNz]

did your mate change the turbo knock sensor when he did the conversion?

theres a plug in the block near the oil filter, that the standard De engine uses as a lower knock sensor or some junk.

did he replace it with a turbo one?

just a stab in the dark.

[blitza]

no? so youre saying that it uses the same sensor in a different location? or two at once in the atmo? hrmmm, will see if nissan list a different part number....

[Adamal]

Get a set of injectors from a DET motor. They have a larger flow capacity than the DE ones.

270cc on the DE
380cc on the DET.

As a comparrison, the Autech S15 SR20DE runs 480cc injectors as an N/A motor

[CozmoNz]

i remember reading it just a week ago.... mate of mine has the magazine, ill see if i can find it again...

(turbocharging N/a engines, performance car did a quick guide), and for the SR engine they also showed *remember to change this plug* pointing at the plug near the oil filter, saying its the *turbo knock* sensor.

i really dont know why an N/a engine would have this, maybe its just a generic *bung* that has no use, but you need to put the DET plug in?

without it id imagine you should get an error code though :S.

pulled any codes?

[ELOK]

does it go hard? i heard the DE has alot more torque than the det so when u turbo a de its a bit better than a det?

[Adamal]

DE+T has more immediate torque, due to compression still being 10:1. However, as you cannot run as much boost as a lower compression turbo motor, the top end power will not be as much.

[1598cc]

extra injector ... hmm .. check ecu for codes, possiblyy fuel pump but if it was fine before then maybe not

how hard does it cut, eg. like hitting a wall or just like a soft revlimit

[blitza]

it hits the wall like me on yamama, but the a/f gauge shows rich, (not that i have 100% faith in it) right untill it eats shit.

will; measure fuel pressure to make sure it isnt falling away
; try unpluging the lower knock sensor, hopefully there will be no error code;
if all that fails will put an elbow on the bottom of the external dump pipe to point it away.

thanks heaps for all the replies, and yeah if you can find tha article, that would be mint..

[RS13]

I didn't think knock sensors retarded timing to that extent? Even so, if it had, it wouldn't cut fuel instantly like that? I've only ever experienced cars with knock sensor issues to run like a bag of shit, missing, low power.. not just *WHAM* fuel cut.

It sounds a lot like hitting the boost cut. Have you double checked boost control? What does the boost gauge do during all this? Not creeping or anything? Maybe AFM? If an AFM is faulty, they tend to cut fuel instantly like that, almost like a rev limiter, I'm pretty sure the DE and DET have the same AFM, but may be worth borrowing a DET item and trying that?

Damn, this is a curly one!

[blitza]

hrmm, good points, the boost sits bang on 8psi till it cuts, so no creaping there, got a det coming in on friday so will try another afm thanks pal!