ca18det mafs maxxed out?

[mat180]

hey guys

ive got a ca18det with bolts on (intake, exhaust, fmic, ect) that spikes at 9psi at about 4500 rpmsthere is no form of boost control in the car as we speak

according to my boost gauge, she runs about 6psi, but when i bring the rpms up, she spikes to 8.5-9.5 psi

its also got a stock ca18det mafs which ive read is only good for 190hp.

do you thik with the bolt ons and 9psi im maxing the mafs then?

if i come on power gradually i can bring it up to redline problem free, if im driving hard and pushing each gear hard, it likes to bounce back around peak VE (5500 rpm) as if it cant go anymore

the car revs and drives perfectly freely otherwiseholds idle well

this is not a swapped car, it a 1990 180sx

[Bwana]

Sounds like the boost solenoid may be malfunctioning or something... Either that or the wastegate is fouled somehow. I can't think of any reason why you should be having boost creep like that with a stock turbo...

[Zero260]

I'm not sure how it is on CA's but from what I've seen, witha 3inch exhaust, you can boost creep a little in higher RPM's. Something to do with exhaust velocity flowing faster than the wastegate can bleed. as far as over flowing the maf, I think you can run up to 12PSI on a factory turbo, with a factory MAF, I could be wrong though.

[turbodcivic]

sorry to thread jack sorta, but im kinda having the same problem...

my gauge will read 9psi and start of WOT but will drop to 5 psi and stick it there the longer i hold it. i dont have a boost solinoid hooked up, my question is which way do i turn the MAFS to open it up?

[ch187]

its a common problem with acuated turbos. i removed my boost soleniod and use an MBC and was able to keep a constant 7psi.

and no with those mods i dont think you maxxed out the maf

the way i look at it, the stock t25 cant max out the stock maf. i never had a problem with it and i ran a similar setup.

[float_6969]

The stock turbo CAN max out the stock MAFS. I've done it. I too am suprised that you're getting creep. On my car, the stock turbo can't even maintain 15psi to redline. at around 5K it starts falling off and by redline it's down to about 10-12psi.

I would guess the stock actuator is sticky. How long is the tube going to the wastegate and where are you getting the signal from? Long lengths of tube going to the wastegate can give you spikes as well.

[ch187]

well ive only had it at 12psi. i would never take that little munchkin past that haha. meh..

[mat180]

my boost spikes the begins to fall off again towards 6psi or so in even higher rpms

ive got my wastegate tube (vaccuum), three way splitted for a bov aswell

could this be it? bad place to draw vaccuum for the bov? shoould i use the feul regulator vaccuum source?

thanks

[ch187]

use the port behind the tb for the bov and dont tee into it. use the port on the turbo for the wastegate and tee into that for the wastegate. done.

[float_6969]

Yea, don't T off of the signal for the wastegate. If you're using the stock turbo, just run a line from the nipple on the front of the turbo, straight to the wastegate and nothing else.

Use the nipple behind the TB on the outside of the plenum for the BOV.

Use the small nipple on the back of the plenum for the FPR.

[ch187]

woops i worded that wrong. yes of course you T into the WG line. only if you have a boost controller

[bias]

I have been following this thread to see if anyone answered the question in a way I could relate but I'm still not getting it. At what point is the stock maf not able to read enough air to feed the mods with the stock turbo at max boost(I guess 15lbs float), with 3" exhaust, down pipe, fmic,intake, Q45 fuel pump(300zx), and everything else stock?

[float_6969]

I'm only running 15 psi on that turbo because I'm not too concerned about it's longevity. It's really not efficient anymore and it won't hold that much boost to redline.

12psi on the stock turbo should be treated as the limit for the stock ECU and MAFS.

[mat180]

thamls for the info guys

im gunna pull the oem solenoid today and install the solenoid for ym evc5

accoridng to the instructions, im supposed to run one line (theres 3 vaccuum lines tat need to be plumbed) to the nipple behind the tb

one to the wastgate

and one to the nipple on the compressor housing

so, now wat should i do for my bov and boost gauge?

what woudl be the best place to tee from with this new setup?i was reccomended fpr reg. line for bov on another site, any good?