Boosting Issues

[72nismo]

Stock KA24DE,Stock MAF,T3 Turbo set at 7lb boost,JWT ecu,370cc Inj,Intercooler,BOV,,3" pipe w/Apex exhaust on a Datsun 510.Here's my problem,seems like after I added the 3" exhaust I started noticing that when I am boosting and hit 7 lbs the boost just drops when before it didn't do that.So I am not sure if it has anything to do with the 3"set up or something else is going wrong. Anybody have any ideas??

[480sx]

What type of wastegate are you running?

So your saying that after you reach 7 psi, instead of holding 7 psi it drops down some? How much is it dropping, at what rpms are you having the issue?

[72nismo]

Wastegate has no name brand on it.Boost & Rpms completely drop.I want to say at about 4500 to 5000 k.The other thing I am wondering is if you are set at 7lbs of boost and your gunning it down the freeway is the boost suppose to hold as long as your gunning it or is it suppose to drop after a certain point?Heres a pic of my set up.



Fixed your pic, WD

[480sx]

So your saying your engine just falls flat on its face after it hits boost? Your rpms go down, boost obviously drops, ect?

If you have a 7psi WG spring(you are externally gated right?) your turbo should spool up, your wastegate should open and you should hold 7 psi of boost all the way to redline.

[240FeVeR]

boost is supposed to hold.

When you reach 7 psi, your boost and rpm drop? Sounds like the problem here isn't the turbo it's whatever is causing your RPM to drop. Losing boost is just a consequence of the rpm dropping.

[72nismo]

It seems to happen when I am gunning in 4th gear and it get to 7lbs it feels like if I had a switch that I just turn off really fast and then I shift to 5th and it does the same thing when it gets to 7lbs.It is totally weird because it wasn't doing that.Would timing have anything to do with it.I retimed it today at stock 20 degree. []

[boker240]

dude, the intake looks realy cool but, that may have somthing to do wit it, 12in pipe wit slight bend in it and put the maf on and ait cleaner and b done wit that part of it. also looks like a z32 maf u got ,did u have the ecu tuned to an inj. size and do u have that inj. size on there?20 btm is right for jwt ,they tune it to stay there .that also looks like internal wgate on there , is it?/ if so get rid of it ,it also could b fouling up.

[72nismo]

Intake pipe is not the problem.MAF is stock 240sx,Yes it is an internal wastegate.and ECU was tuned for 370 cc injectors.

[Florida240sx]

Car was running fine before upgraded exhaust?Ran the ecu for codes? Sensor or wire somewhere. I'd check the mafs wiring/voltage.

[Florida240sx]

You've done a boost leak test right? I had a leak at 15psi but wasn't present at 10psi. Cut coupler somehwere by chance possibly by the clamps tightening on the coupler?

[WDRacing]

The T3 is kinda small, although 7 psi isn't very much. If the boost was dropping off in the higher rpms only with no other symptoms then it would be normal with a smallish turbo.

But what you're saying is definitly odd...swap the exhaust and all of the sudden the motor gets sluggish under full boost, but only in 4th and 5th? Is that right? Or is it in every gear? What rpm does it start to fall at? Or is it as soon as you hit 7psi in all gears.

Right now I'm leaning towards a boost leak myself.

[BoostedNismoNJ]

Check the o2 sensor the injectors and maf it could be fuel cut.

[72nismo]

Ok so today I adjusted the actuator and I raised the boost to 10lbs car seem to perform normal.I even had my friend test drive and it ran fine until I drove it home it did it to me once.So I thinmk I am going to get a new actuator 1st and check for leaks & maf.

[nelson8708]

super clean setup man. Hope you get the problem figured out.

[cmoody2006]

Yes it looks purty but... I wouldn't run the intake like that... I don't like that sharp of a bend. Why not just make it straight? You might even see a hp gain possibly.

[72nismo]

The reason my intake is that way is because i have to have a minimum of 12" from turbo to maf.So that is the only design that works.I can't go straight or elbow not enough room. If it would fit it would of been done by now. .
Modified by 72nismo at 11:03 AM 1/14/2008

[72nismo]

Ive read a few comments of my turbo being to small for my 3" exhaust.Turbo not spooling fast enough because of less back pressure.Which im starting to think that it might be that turbo is to small.I was running 2 1/4" or 2 1/2" exhaust pipe before and it would spool up faster.
Modified by 72nismo at 11:05 AM 1/14/2008

[WDRacing]

Wrong...

Turbo's love NO back pressure. The more pressure you have behind the turbo the more lag you have since the exhaust isn't free to flow past the turbine wheel. But, a 2.5" exhaust is plenty for 300whp. So having a full 3" is overkill, but over kill in this case isn't a bad thing.

WD

[boker240]

it ran fine like this both times!big *** sucking sound when i hit boost but i think it sounded cool.

[72nismo]

Thats interesting because I had a friend with the same set up and his car would idle fine but when he would drive it and come to a stop the car would want to turn off on him and also just by revving the car it wanted to turn off.So then we put the same intake I have and problem was solved.I was originally told by JWT to run it this way.

[480sx]

The reason your supposed to have your Maf 12-18 inch's away with a bend is due to the vortex effect that the turbo makes on incoming air. It messes with the accuracy of the MAF. Sure you can get away with running it like that, but its not really what you want to do.

[72nismo]

boker240 How come your set up isn't 12-18" long?