boost issue, huge flat spot

S

serious

first to say hi to everyone.

i am about to pick up a st,
went for a test drive, the car is alright, the only issue is it has a huge flat spot while boosting at around 7-9 psi, it felts like power cut off at all then pick up again.
other than that the engine still pulls pretty hard.
i believe the problem is the valve control the sc switch over to the turbo?
or spark? or some other things else?
 
ok, i have picked up the car today.
have spent about 2 hours to play around with this little beast,
found 2 vacuum hoses hanging, bad mate :eek:, fixed that but still can hear the "hisssssss" at the center of the engine, believe there are more vacuum leaks, between the eccs and rocker cover,
no doubt that causes the rough idle, will have a better check later.

also have some new thoughts of the boost issue,
if i put my foot down, the sc hit 14~15psi instantly and then fuel cut, i.e no acceleration even i floor the gas pedal (bear in mind i havent put my foot off the pedal yet).
but if my foot off the pedal and reapply to it, the car accelerates again until fuel cut (or air-cut?) again.

any input will be much appreciated.
 
located in kangaroo land :laugh:

pretty hard to find info about the st, even on this forum.
if there is sticky thread about all common problems, part number e.g spark plug, and interchangeable part with other cars, etc, that will be excellent.
 
dammit, that's a long way from any super turbos :p

To be honest it sounds like a boost leak, so I'd start with sealing the intake except space for an air gun, turn the regulator to 10-20psi and fill the intake. Any air leaving anywhere except through the valves needs to be found and fixed.

Where abouts are you based?
 
south australia adelaide :laugh:
remember the super turbo figured on autospeed? I picked that up on the weekend.
definitely will check all the hoses and vacuum line later this week.

just had a quick check on spark plugs today, they are NGK plug BP5ES, is it the right plug? search on the forum, http://www.micra.org.uk/threads/29684-Spark-Plugs, refers to BPR8ES....?

also what is the part# for oil filter?
 
well yours is the 3rd regoed one I know of in Oz then, Snikty on these forums has 1 in Brissie (off the road I think), and I have the one from smidge on here (also featured in mighty mods), mine is also off the road for a rebuild atm.

maybe we need to start supertubosaustralia.com:p
 
so probably mine is the only one on the Oz road at the moment? :p

i have read through 11 pages here, couldnt get many parts information, except brake from gtir.

what is your suspension set-up? any useful part tips?
 
also brakes from gtir are an upgrade not standard replacement. Mine has N14 pulsar brakes on the front for the same reason.

sorry not sure on filter or plugs, none of my paperwork is out atm (building a house and everything is in storage). I'll bet it is the same as the regular K10 March though.

Re suspension, the factory stuff is terrrible...think 30year old hatch back design. I was going to spend a bit on getting it to handle properly once the new motor is in and running, I have a contact that does small fwd race cars, eg starlet, with very similar suspension.
 
yes, even only have had it for 2 days, I can tell the stock suspension is just crap. I just want it be bit more stiffer and firmer.
maybe try looking at daihatsu charade as well?

is the N14 brake direct bolt-on?

by the way, has K10 micra even been sold locally in OZ?
 
nope K11 was the first in Oz. And I'm pretty sure nothing had a MAxx motor either, so yo uwon't find direct part numbers in local shops.

But, being nissan, the common stuff like plug,s leads and filters will probably be shared with local motors, so start with pulsars, exas etc from the 80s.

Re suspension, the basic layout is same as starlet and maybe others, I understand mine actually has starlet shocks in the rear (or maybe the front, can't remember, smidge could confirm). Either way, when I do it all I will post up the details. Also, snikty had custom bushes made up and I will do the same, I will let you know when I do if you want to order a set at the same time.

Anyway, job 1 is to get it running properly, there is a good diagram of all the vacuum hoses that Baz has posted up previously - colour coded to try and follow it.
 
yes, I have had a good read on the vacuum lines diagram, even color coded but still very hard to follow....

for sure will get it run probably first! I m sure the problem now is when the sc change over to turbo.
 
OK, just got the vacuum lines redone by following the awesome diagram here.
basically i reroute the vacuum lines straight to its destination, much easier to follow now.

idle now is much better but still not perfect, a little erratic, not a big deal here.
Test drive, first 2 run smooth as!! hardly notice the change over from sc to turbo, and boost drop to around 10-11psi from 14-15psi before, no fuel cut or what so ever! :laugh:

about 10 mins later, the old symptom come back a bit, (feel like fuel or air cut off), but not as bad as before.

should I look at the gasket on the intake side?

p.s. new spark plugs BP7ES and leads
 
small update.
cd played in (Y)

cleaned the ufo, load of oil came out! but running condition no change fwn

to let the turbo kick in i need to precisely control the throttle to let it rev over 4K rpm.
however, it will run rough at top end and eventually back fire. ( only good fuel been used)

the good thing about the st is, no smoke :grinning:
 
serious said:
small update.
cd played in (Y)

cleaned the ufo, load of oil came out! but running condition no change fwn

to let the turbo kick in i need to precisely control the throttle to let it rev over 4K rpm.
however, it will run rough at top end and eventually back fire. ( only good fuel been used)

the good thing about the st is, no smoke :grinning:
Click to expand...

As I said the turbo only comes in after 4000rpm so that is correct, all other issues you are describing are vacuum and ufo related
 
problem solved today.
it was one of the intercooler joint. after tighten up all the clamps it runs beautifully!
by the way i put one boost line in wrong way, the sc boost up to 20 psi instantly! spin wheel no doubt !

some notes on servicing parts:
spark plug NGK----BP7ES
oil filter Z145A
 
serious said:
problem solved today.
it was one of the intercooler joint. after tighten up all the clamps it runs beautifully!
by the way i put one boost line in wrong way, the sc boost up to 20 psi instantly! spin wheel no doubt !

some notes on servicing parts:
spark plug NGK----BP7ES
oil filter Z145A
Click to expand...

Cool, man what joint was leaking? the 20psi boost from the wrong vac line is actually the ypass valve staying open and the turbo and s/c boost together, make sure you sort that otherwise you will kill the engine(Y)

Also good info in the plugs they actual plug is a Bpr6es and if you running any more power than stock factory i would put the 7es in as it is a colder plug.
oil filter is the same as an ma10, 12 so readily available(Y)(Y)
 
it is the joint to the intercooler, massive leak! i think that hence not enough pressure to open the Y-pipe valve.

there are 2 vacuum lines, one to turbo outlet pipe, the other to the manifold intake pipe, i connect them wrong way around, that instant power was WOOWAA grr
immediately realize that's not right! fixed that already. very happy all vac lines have been redone, just a 10sec swap :grinning:

do i need 2 boost controller 1 for sc other for turbo? or just one is fine? then to which vac line?

i believe we dont have that engine in australia,
but lucky (unlucky) enough it still has a genuine oil filter on! i google its part number, find that ryco z145A can be used, which you can buy it anywhere in oz. or z442 (that is a smaller filter but dearer). there are common filter used in most nissan engine, i.e sr20, rb, etc
spark plug lead is easy, take them to any auto shop here, match the length, done. I use Bosch.

post some pictures later :grinning:
 
You can only control the boost on the turbo - mine has been running 15psi on a single bleed valve. Changing Supercharger boost requires different pullies etc - given that it is a very small s/c, even for such a small engine, I wouldn't be playing with it.
 
serious said:
I have read somewhere in this forum from either ed or baz, sc boost can be changed withot touching the pulley?
Click to expand...

Yeah really what happening it the bypass valve opens slighty and some boost is let in from the turbo, not worth doing really. Really what needs to be changed is the fueling as it so rich when the s/c is going
 

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