Stagea Boost Probs.

[m1lky]

I have a 97 RB25DET Auto Stagea. The engine is completely stadard at mo and its running 4psi boost. I just put a boost tap on yesterday, a real simple one that just bleeds pressure to atmosphere, and wound it up to 10psi. It boosts at 10 then spikes to about 13 just before changing gear, then settles back down to 10 in the next gear. I can hear a fluttering sound coming from the engine bay which I assume is just the tap, but I dont know why its fluttering?? But the main problem is when its doing this the whole car judders as if its trying to break traction, but its not. Its pretty bad and it never did this before, and doesnt do it when i wind the boost back down. Also when it changes into second it looses power. The boost gauge still reads 10 but it definatly doesnt feel like it. And at slow speed there was some pretty funky sounds and clunks coming from what feels like the diff. These also go away when I wind the boost back down.

Anyone know what goin on???

[wolverine]

rich and retard mapping will be one of the causes.

alternatively it also sounds like compressor surge. the compressor is feeding in more air than the engine can take and there is a backwave of pressure being vented by the BOV.

is it the standard turbo? what exhaust? what IC?

Edited September 1, 2008 by wolverine

[m1lky]

Standard turbo, standard, exhaust, standard i/c. Also doesnt have a BOV. Uness it has a standard one, but ive never heard it.

How can I fix any of these things?

[KiwiRS4T]

Standard turbo, standard, exhaust, standard i/c. Also doesnt have a BOV. Uness it has a standard one, but ive never heard it.

How can I fix any of these things?

Probably not a good idea to vent to atmosphere ... try plumbing it back into the intake pipe or else get rid of the boost tap and just follow the "ten minute no costguide to 0.5 bar" at

http://www.skylinesaustralia.com/forums/Ja....html&st=20 (post 40)

and play with the size of the restrictor til you get the boost you want or the exhaust can handle.

(the standard bov is plumbed in - you don't normally hear it.)

[QWK32]

yes they have a stock bov, usually muffled down by the airbox. the climb in boost is probably the stock boost solinoid, which switches to a higher boost setting when you get higher in the revs. stock its 5psi then to 7psi.

with the boost tee in there it sounds like you have wound the initial boost up to 10psi, then when the boost solinoid switches your getting 13psi. bypass the stock boost solinoid then set the boost level. although, i wouldn't recommend running anymore than stock boost with a stock exhaust.

all the jerking and "juddering" would be air flow cut. running anything above 10psi, which your getting when it climbs to 13psi, you can max out the airflow meter causing the engine to feel like its cutting in and out.

[m1lky]

Oh really, ratshit. This is going to sound like 21 questions but... is there anyway i can run more than 10 psi or will I have to wiat untill Ive done the exhaust. Do you usually have to uprade the afm to run high boost? And what would you recommend replacing the afm with, whats a common upgrade?

[jonny8ball]

Oh really, ratshit. This is going to sound like 21 questions but... is there anyway i can run more than 10 psi or will I have to wiat untill Ive done the exhaust. Do you usually have to uprade the afm to run high boost? And what would you recommend replacing the afm with, whats a common upgrade?

Z32 will do it! Same as 300zx. I've just ordered mine up from Nissan japan cause mine was maxing out.

[KiwiRS4T]

Z32 will do it! Same as 300zx. I've just ordered mine up from Nissan japan cause mine was maxing out.

Your standard afm is not the limitation.

If you are planning to raise boost to 10psi as the only mod then you should get your actual air/fuel ratio checked with a meter (e.g. on a dyno) because you could end up blowing a piston. Preferably get a bigger exhaust rather than a new afm ($200 for a second hand Z32) and check your fuel pressure.

[jonny8ball]

Your standard afm is not the limitation.

If you are planning to raise boost to 10psi as the only mod then you should get your actual air/fuel ratio checked with a meter (e.g. on a dyno) because you could end up blowing a piston. Preferably get a bigger exhaust rather than a new afm ($200 for a second hand Z32) and check your fuel pressure.

For me the standard afm is my only limitation left on the engine. I've had it on the dyno and the afm is maxed.

There's not alot left that's stock apart from the afm. The standard afm maxes at 300bhp and I'm able to go above that with the work that's been done on the engine and to get there I need a z32.

You guys pay alot for new z32 afm! I bring new ones in for £200

[Xmetal]

Milton

In the meantime bin your standard exhaust and I/C and upgrade. 10psi is going to do diddly squat with a standard exhaust and intercooler.

Basically, buy a catback exhaust, bigger dump pipe and hi-flow cat and then buy a front mount intercooler. shouldn't cost you much more than $2k for all of that.

[m1lky]

2g? Faaaarken hel. Ha I only paid 3500 for the car. Ill be getting that stuff later but winding up the boost is cheap for the meantime. 4psi is a bit of a joke. I just got a free boost tap so was gonna wind the crap out of it but seems like it aint that simple. I think ill just bypass the solinoid and run 10 psi or maybe bit less. And yea Kiwi ill get a a/f ratio guage to keep an eye on it.

But thanks guys at least now I know what the all shuddering is - too much boost!

What about the clunking from the diff?? I read somewhere on here that the rear diff locks itself or something when you take out the 4wd fuses? Anyone know if thats true?

[KiwiRS4T]

2g? Faaaarken hel. Ha I only paid 3500 for the car. Ill be getting that stuff later but winding up the boost is cheap for the meantime. 4psi is a bit of a joke. I just got a free boost tap so was gonna wind the crap out of it but seems like it aint that simple. I think ill just bypass the solinoid and run 10 psi or maybe bit less. And yea Kiwi ill get a a/f ratio guage to keep an eye on it.

But thanks guys at least now I know what the all shuddering is - too much boost!

What about the clunking from the diff?? I read somewhere on here that the rear diff locks itself or something when you take out the 4wd fuses? Anyone know if thats true?

If you leave those fuses out in a Stagea you'll end up with a stuffed transmission (do some readind in this forum).

BTW Jonny 200 pounds is AU$421 or NZ $516!