Bambam7

Ya- I singled you out HAILERS, because you seem to have spent too much spare time fondling your voltmeter!
I noticed youve tested the boost sensors a few times, and just wonder if you- or anyone else- knows what voltage from the TII pressure sensor cooresponds to what boost levels??
I just want to know, because I don't have a boost gauge yet- but when I get the turbo in, I can at least drive around, and I want to make sure I'm not getting crazy boost creep! (street port, exhaust, intake, all that!) If I know what voltage 10 psi is- I can keep in under that!
Thanks!

Dan

NZConvertible

Well that's a crazy way to monitor boost but if you read the write-up on the Team FC3S DIY FCD there's a graph of exactly what you want.
Just buy a boost gauge, there's no reason not to.

Bambam7

Oh, don't worry, a boost gauge is definatly on the list!!
I just don't have one yet, and I'm a cheap-***, so I am waiting untill I find one that agrees with my wallet (E-bay or used.. like my AFC, etc..)
It's just that the turbo will be done in the next month, and I don't want the perfectly funtional car sitting in my driveway- finally all done, and scared to take it around the block because of unknown boos the first time I turn the key... all because I am a cheap-*** and havn't found a gauge yet........

HAILERS

Yeah, that team fc3s is the site. Oh not so fast there NZCONVERTIBLE, on the goofy way to observe boost. I did the reasonable thing and followed advice on this forum to disregard the factory gauge and buy a boost gauge. Dutifully did buy a Autometer. Nice bright shiny thing it is too. Needle moves up and down during boost. Easy to read numbers in psi. Light weight. Reasonable cost. Too bad I bought the only one that lacks that feature I was really looking for. Accuracy. I hit fuel cut when the thing shows 10 psi. Fuel cut is 8.6 psi on a series four. I used the voltage readings from the above site to confirm the Autometer was optimistic. My car isn't capable of 10 psi. It only has a 2.5 inch downpipe with presilencer and stock exaust (the 2.5 was deliberatly selected over the 3 inch). I have found the factory gauge to be a darn site more accurate that THAT GAUGE I BOUGHT. All that BS said, yeah, buy a gauge, but make sure its a good one. And Bambam, you are looking at a turbo boost sensor? Not a na sensor? They read different even if they look the same. Considerably different on the readings.

Bambam7

I am working on seeing if I can run them both at the same time, and run the stock one to the ECU, and the TII one to my S-AFC instead of it taking the TPS signal.
It would give me fuel dependant boost (which I need with my TII conversion) instead of throttle dependant- I should be able to get a more consistant A/F ratio that way.

niner

Pretty good idea. I guess you could be the pioneer and tell us how it works out for ya. Oh yeah-I just sent you another email

HAILERS

A graphic example of how different the two boost/pressure sensors are...........If I patch my n/a boost/pressure sensor on to the TurboII car, the factory TurboII boost gauge needle will go half way , no make that three quarters of the way up the boost gauge just sitting there with the key on and the engine not running. I kinda see what you are doing. I've got a spare/rebuilt turboii engine I'm going to put in my n/a someday, but I also have a N332 turbo ecu to go with it and a turboii boost/pressure sensor. I'm not quite as adventurous as you are. Mostly because I'm a touch ignorant about to go about it. Someday, no hurry.

NZConvertible

Yeah, you’re dead right. That is a good way to check boost. I was thinking monitoring boost long term, and had images of a DMM strapped to the dashboard and Bambam furiously converting voltage to pressure in his head while screaming down the drag strip! Overactive imagination...
That’s a pretty good way to check your boost gauge; I might do it myself. And when I said buy a boost gauge, I should have said buy an accurate boost gauge! One of the reasons I bought a VDO boost gauge instead of the common Autometer is because I know I had a much better chance of getting an accurate gauge.

Thaniel

Anybody got the same kind of info as posted on the link
http://www.teamfc3s.org/info/articles/fcd/diy_fcd.htm

except for the NA boost sensor. The manuals I have read seem to have some conflicting info for pressure vs voltage.

HAILERS

THANIEL.....All I have is the 87 fsm that says 2.5 ~ 3.5V when pulling 100mmhg (3.9 inhg) on the boost sensor. I could do some more figures if needed. My car just sitting there with just the key on gives me 3.5 volts. This is for a N/A engine. The n/a uses a boost sensor. The turbo model uses a pressure sensor. Go figure. About 1.2 volts at idle of 800 rpm (got tired of waiting for the car to fully heat up for a 750 reading). All the above on a 87n/a.

Six Rotors

iTrader: (17)

There is a little more info in the FSM(see4A-32 and 4B-32).It gives you the voltage of the sensor with no vacuum on them--3.5-4.0v on the N/A sensor and 2.3-2.7 on the TII sensor.

HAILERS

Here's a jpg out of the 87 manual for NORMAL ENGINES.

HAILERS

This for n/a:

Thaniel

Thanks for the info. It's the 3.5V in both specs that keeps bothering me. In the hanes manual the no vac values are higher as well.

Mine reads just under 3.4V with the key on which is out of spec but is .1 V enough to make it bad? I think my voltage at idle is around 1.0V. I hooked a voltmeter and took it for an run then hooked the same thing up to my bros '87 and did the same thing. They were pretty much the same but mine seemed .1-.2 V lower. Trying to decide if that is enough to cause problems?

I'd just buy a new and say the hell with it but the price for a new one from what I hear is high.