PSI Level Question.

[mshaw]

man people arguing i dont know who knows, i will tell you later tonight when i have tested it and tell you what the boost reads and what the vacuum is at idle, i think i will probably take a pic and post it where i have the boost gauge coming too in the engine

[dymz999]

I'll say this one more time, quite blunt your a blabbering idiot now go away and never come back.

SR20 engines, the FPR port is not i repeat NOT pre throttle body. It comes right off the intake manifold. The boost rate coming from the turbo doesn't mean nothing as it is not the factual amount of boost hitting the engine. Who cares if the turbo makes 18psi when the engine is seeing 20psi which in most cases is the situation.

I'll tell you this much you are a crappy internet mechanic. I do have an SR20 and know just about as much as one can. I recently had the "joy" of rebuilding the engine and upgrading everything.

yes the engines do have a wastegate, it is internal however and controlled by a set amount of vacuum going to the actuator rod which in turn opens and closes the wastegate. however when a wastegate goes bad it will cause the boost to be less not more. because the amount of vacuum going towards the actuator creates a leak in the diaphram which causes less pressure in the actuator arm and the wastegate is then open more thus allowing less boost. Not all actuators see exhaust gases, actuators are used on all Nissan engines i have worked on that are turbocharged. This is how they work down to a tee. This is the opposite of what is happening.

Now then, i'll re-itterate this, you dont know nothing about these engines so why try to help people with them with useless information? Unfortunately i have a lot of accurate information i can share on them from my own experiences. For the record you shouldn't insult people when you dont know anything about them, in this case my friend you were dead wrong. I'm not trying to argue here, i'm trying to give you accurate information so you can solve your problem. listening to someone who is giving you "generic information" will get you know where when you need specific help.

[86max]

I HAVE AN SR20 TOO!



Dymz, No need to argue if someone doesn't agree with you man.

Mshaw, if you want a more accurate boost gauge pm me.

[RickDaTuner]

yeah 86max will hel p you out good man

[dymz999]

Wow dont know where you pull your garbage from, man I get my stuff from the FACTORY SERVICE MANUAL which is what people should read for the answers.

a) FPR port comes from the intake manifold right above the throttle body but after the throttle body itself.

b) it uses an internal wastegate that has a flapper and an actuator. when the actuator goes bad the turbo will not produce as much boost.

c) the most accurate measurement of boost is obtained from the intake manifold itself. Aka this is how much boost is actually going into the engine. If you place the boost line out of the hotpipe you'll get how much air the turbo is producing but not how much is going into the engine.

d) when the base timing of the engine is off (retarded) it will cause you to be able to make more boost than normal as there will be excess fuel which is being burned off which causes the turbo to spool way more than it normally does. (this is similar to people in japan who inject nitrous oxide into the turbo of a T88 to make it spool instantly.

Not a matter of arguing, but people giving generic information to specific problems is just wrong. I still find this all kind of funny though. Considering all i've done with these engines to have some subaru dude tell me this and that is really kinda funny. Especially when he clearly knows jack about the engine(s) in question.

[RickDaTuner]

Originally posted by dymz999
Not a matter of arguing, but people giving generic information to specific problems is just wrong. I still find this all kind of funny though. Considering all i've done with these engines to have some subaru dude tell me this and that is really kinda funny. Especially when he clearly knows jack about the engine(s) in question.

so hows that small penis treatin you?

[dj_rice]

Originally posted by RickDaTuner


so hows that small penis treatin you?

[EK 2.0]

Originally posted by dymz999
I'll say this one more time, quite blunt your a blabbering idiot now go away and never come back.

Now then, i'll re-itterate this, you dont know nothing about these engines so why try to help people with them with useless information? Unfortunately i have a lot of accurate information i can share on them from my own experiences. For the record you shouldn't insult people when you dont know anything about them, in this case my friend you were dead wrong. I'm not trying to argue here, i'm trying to give you accurate information so you can solve your problem. listening to someone who is giving you "generic information" will get you know where when you need specific help.

how is your "I drove over railroad tracks and blew-up my SR motor" doing??

[mshaw]

so to earlier questions my vacuum in neutral is sittin at about 15 in.Hg and when i rev pretty hard to about 5500 revs i get about 2 psi, slowly doing it does nothing, i dont really feel like taking a picture but if it will help the solution i will for sure snap a quickie and put it on here

[dymz999]

EK 2.0 i dunno, 9:1 compression SR20 motor is pretty nice and fun to drive right now.

Now back to the point, normally you shouldn't be able to make any boost in neutral. Is the boost at 2psi fairly constant each time? If it were a timing issue you'd be likely seeing full boost by 5,000 RPM in neutral. If your coming to the NECC meet on sunday i can bring my spare gauge so you can verify its correct if you want...

[mshaw]

u know what i may do that actually, kinda busy that day though, what time is it goin on?

[pressure_ratio]

Originally posted by Aleks
Inaccurate boost guauge. My autometer reads 16psi even tho it's 11-12 max!

Originally posted by legendboy
elevation?

Why do people not realize this
Gauges are calibrated at sealevel,when you go up the readings do also.
You can't depend on factory boost specs either for the same reason.

[mshaw]

so does that mean that all boost gauges in calgary would be off by a couple psi that doesnt make sense

[dymz999]

Up at this elevation our pressure would most likely drop if i'm correct as the air is actually thinner. This is why i was told when doing a compression check on motors you can expect slightly lower compression than an engine say in vancouver since our elevation is higher.

[RickDaTuner]

Originally posted by pressure_ratio





Why do people not realize this
Gauges are calibrated at sealevel,when you go up the readings do also.
You can't depend on factory boost specs either for the same reason.

if the engine is desinged to regulate the Turbo for 7psi, then its going to make 7psi worth of boost either at see level or 3000ft of elevation.
It will only go down as altitude increases, and even then you would have to be pretty high before a turbo wont make its factory level Boost due to altitude...

gauges may be calibrated at sea level but if there is 7 psi worth of boost going into the engine, then its going to also read 7 psi of boost at the gauge since boost is static and not dynamic, if a gauge was going to read higher or lower due to altitude you would see that with the car turned off (the gauge would Read Positive or negative with the engine off)

they do read off though, due to miss calibrated Diaphrams in the gauge itself,

what does read actuall main sea level pressure regardless of your altitude is the MAP sensor, these are sealed and calibrated to sea level

[dymz999]

Mleh, your "somewhat correct". Maybe now explain to him why 7 psi on a T25 and a T28 is actually not the same....

also explain why your vacuum will increase by 1 to 2 psi when you go from calgary to vancouver...

[RickDaTuner]

Originally posted by dymz999
Mleh, your "somewhat correct". Maybe now explain to him why 7 psi on a T25 and a T28 is actually not the same....

also explain why your vacuum will increase by 1 to 2 psi when you go from calgary to vancouver...

are you fishing for faults, or testing my knowledge?
How about you add on to whats missing

This Forum is a constructive one, I am not here to prove my intelligence is greater than yours.

[pressure_ratio]

Originally posted by RickDaTuner



if the engine is desinged to regulate the Turbo for 7psi, then its going to make 7psi worth of boost either at see level or 3000ft of elevation.
It will only go down as altitude increases, and even then you would have to be pretty high before a turbo wont make its factory level Boost due to altitude...

gauges may be calibrated at sea level but if there is 7 psi worth of boost going into the engine, then its going to also read 7 psi of boost at the gauge since boost is static and not dynamic, if a gauge was going to read higher or lower due to altitude you would see that with the car turned off (the gauge would Read Positive or negative with the engine off)

they do read off though, due to miss calibrated Diaphrams in the gauge itself,

what does read actuall main sea level pressure regardless of your altitude is the MAP sensor, these are sealed and calibrated to sea level

I agree with you somewhat but temprature and air pressure will have an effect on your boost level.Look at the altimeter setting in an aircraft,it constantly needs to be updated acording to barometric and weather conditions,you can be several hundered even thousand feet off.


Any pressure gauge works on differential pressure.Pressure between what ever the signal is vs. outside air pressure.If the outside air pressure changes from altitude,air temp,humidity your reading on the gauge will change also.Similar to a barometer.

The reason an SAFC or whatever piggyback you may be using will read different than your gauge is they use a map sensor which reads absolute pressure,which isn't affected by outside conditions.

There are a lot of factors that could change the stock boost level.Bolt on an exhaust,intake,etc and it will change also.

[RickDaTuner]

Originally posted by pressure_ratio



I agree with you somewhat but temprature and air pressure will have an effect on your boost level.Look at the altimeter setting in an aircraft,it constantly needs to be updated acording to barometric and weather conditions,you can be several hundered even thousand feet off.


Any pressure gauge works on differential pressure.Pressure between what ever the signal is vs. outside air pressure.If the outside air pressure changes from altitude,air temp,humidity your reading on the gauge will change also.Similar to a barometer.

The reason an SAFC or whatever piggyback you may be using will read different than your gauge is they use a map sensor which reads absolute pressure,which isn't affected by outside conditions.

There are a lot of factors that could change the stock boost level.Bolt on an exhaust,intake,etc and it will change also.

I also agree with you on the above info, but Boost gauges used in cars are nothing more than a Open diaphram, they arent sealed units like altimeters, or Map sensors.

when pressure is applied to the Diaphram it will expand or contract(vaccum) and no matter what the tempeture or altitude reading will always be the same. it will always be the same because thier O psi/vaccum reading is reset everytime the car tuen off due to its open diaphram, basically they are nothing more than over Glorified Tire pressure gauges...

as for the other factors that can change Boost such as exhaust or intake, this is mainly the fault of the Stock turbo components not being able to handle the increase of CFm, that bolt on mods such as exhaust or intakes bring with them...

[pressure_ratio]

^^Agreed.

M Shaw you never mentioned if your car has any mods done?

Point is I doubt you have to worry much.Stock boost specs are somewhat vaugue.Don't go blaming the gauge as a POS.