What voltage to see from boost sensor?
07-19-04, 09:22 PM
#1
What voltage to see from boost sensor?
OK,
So my car has been running fine for the last 3 days.
The only item I removed from my system was my unknown condition HKS FCD.
My symptoms were that the rear housing wasn;t getting fuel.
So for now I have assumed that the FCD was bad and was sending the ECU into fuel cut(at idle/startup!)
Now I remember checking the boost lines voltage one time and with the FCD in there at idle it was like 3V.
I think(can't remember) I checked the voltage with the FCD out and it was like at 5V.
Does anyone have some info on the voltages?
Like does voltage drop or increase with pressure?
So my car has been running fine for the last 3 days.
The only item I removed from my system was my unknown condition HKS FCD.
My symptoms were that the rear housing wasn;t getting fuel.
So for now I have assumed that the FCD was bad and was sending the ECU into fuel cut(at idle/startup!)
Now I remember checking the boost lines voltage one time and with the FCD in there at idle it was like 3V.
I think(can't remember) I checked the voltage with the FCD out and it was like at 5V.
Does anyone have some info on the voltages?
Like does voltage drop or increase with pressure?
07-19-04, 10:52 PM
#2
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boost sensor is just like a map sensor
it works as a variable resistor from about 1v to 4.9v
and thats right what the fcd is doing becase it is not letting the sensor see the full load on the motor thats (5v) why it doesnt cut fuel
when u take it off u see the full 5v and u will get a cut if boosted above 8.6psi
it works as a variable resistor from about 1v to 4.9v
and thats right what the fcd is doing becase it is not letting the sensor see the full load on the motor thats (5v) why it doesnt cut fuel
when u take it off u see the full 5v and u will get a cut if boosted above 8.6psi
07-20-04, 12:58 AM
#3
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you voltages at idle should be low.. like below one.. The FCD should never send out voltage over 3.65 Volts, at about 3.68 volts, the ECU will slap on the fuel cut.
You may have something hooked up wrong. The brown and red wire is the boost OUT from the sensor to the ECU (it is the only one that should fluctuate). One wire should be ground another should have a constant 12V and one shoud have a constant 5v (this is the reference voltage or V-REF) make sure the connections are good.
When I was prototyping my FCD's on my car, i had the same thing happen if the V-Ref connector came loose or wasn't making good contact.
Get some silicone Electric contact grease and lube up all the contacts with it.
You may have something hooked up wrong. The brown and red wire is the boost OUT from the sensor to the ECU (it is the only one that should fluctuate). One wire should be ground another should have a constant 12V and one shoud have a constant 5v (this is the reference voltage or V-REF) make sure the connections are good.
When I was prototyping my FCD's on my car, i had the same thing happen if the V-Ref connector came loose or wasn't making good contact.
Get some silicone Electric contact grease and lube up all the contacts with it.
Last edited by YearsOfDecay; 07-20-04 at 01:06 AM.
07-20-04, 02:48 AM
#5
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Originally Posted by Digi7ech
OK,
So my car has been running fine for the last 3 days.
The only item I removed from my system was my unknown condition HKS FCD.
My symptoms were that the rear housing wasn;t getting fuel.
So for now I have assumed that the FCD was bad and was sending the ECU into fuel cut(at idle/startup!)
Now I remember checking the boost lines voltage one time and with the FCD in there at idle it was like 3V.
I think(can't remember) I checked the voltage with the FCD out and it was like at 5V.
Does anyone have some info on the voltages?
Like does voltage drop or increase with pressure?
So my car has been running fine for the last 3 days.
The only item I removed from my system was my unknown condition HKS FCD.
My symptoms were that the rear housing wasn;t getting fuel.
So for now I have assumed that the FCD was bad and was sending the ECU into fuel cut(at idle/startup!)
Now I remember checking the boost lines voltage one time and with the FCD in there at idle it was like 3V.
I think(can't remember) I checked the voltage with the FCD out and it was like at 5V.
Does anyone have some info on the voltages?
Like does voltage drop or increase with pressure?
Depending on the known variables, use one of the two equations.
Out(V) = 0.169V/psi*P(psi) + 2.318V
P(psi) = (Out(V) - 2.318V)/0.169V/psi
07-20-04, 03:04 AM
#6
well those numbers are guestimates.
So if the car is running at 1.5k I should see only a volt or close to it right?
The connections at the boost sensor itself were horrendous. I had to rewire 3 of the 4 due to broken and brittle wires.
I'll check the voltages tomorrow when I make a jumper wire plug to bypass a FCD(made my FCD plug and play
)
Oh yeah.
J...
I drove my car for about 15 minutes today never going into positive boost and under 4k rpm.
I got home and checked the engine. The turbo was a little red/glowing.
Possible timing?or is it normal?Last time I checked I was at about 6-7advanced so I was really close to stock.(stock being 5degrees)
So if the car is running at 1.5k I should see only a volt or close to it right?
The connections at the boost sensor itself were horrendous. I had to rewire 3 of the 4 due to broken and brittle wires.
I'll check the voltages tomorrow when I make a jumper wire plug to bypass a FCD(made my FCD plug and play
)Oh yeah.
J...
I drove my car for about 15 minutes today never going into positive boost and under 4k rpm.
I got home and checked the engine. The turbo was a little red/glowing.
Possible timing?or is it normal?Last time I checked I was at about 6-7advanced so I was really close to stock.(stock being 5degrees)
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07-20-04, 01:24 PM
#9
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Read the voltage/pressure chart on this site: http://www.teamfc3s.org/info/articles/fcd/diy_fcd.htm
I'd quickly pull the afm and the turbo inlet duct off and reach down there and feel for play on the turbo shaft. It should be negligable.
I'd quickly pull the afm and the turbo inlet duct off and reach down there and feel for play on the turbo shaft. It should be negligable.
07-20-04, 01:38 PM
#10
The turbo is fine. It has 40 miles on the rebuild.
The car wants to build boost fine too. I accidentally hit 4psi in second gear a day ago.
So far my driving has been all very light throttle to keep it under 0psi/into vacuum.
I think I put 8 miles on it yesterday during that drive.
The car was running at 1/3 on the stock S4 guage and I didn't have a hood or undertray on.
I haven't really gone over 4k yet.
Tonight I will check timing and my plugs. I want to see if my rear housing is really doing it's full job.
I'm planning on driving it 32 miles one way to work tomorrow.
I will have extra belts and stuff on hand in case I break down.
The injectors are tested and cleaned 550's and I have a Walbro so I shouldn't be running out of fuel.
The car wants to build boost fine too. I accidentally hit 4psi in second gear a day ago.
So far my driving has been all very light throttle to keep it under 0psi/into vacuum.
I think I put 8 miles on it yesterday during that drive.
The car was running at 1/3 on the stock S4 guage and I didn't have a hood or undertray on.
I haven't really gone over 4k yet.
Tonight I will check timing and my plugs. I want to see if my rear housing is really doing it's full job.
I'm planning on driving it 32 miles one way to work tomorrow.
I will have extra belts and stuff on hand in case I break down.
The injectors are tested and cleaned 550's and I have a Walbro so I shouldn't be running out of fuel.
07-20-04, 02:06 PM
#11
Hmmmmmmmm.................
Well!
Me had another thought.
Sinc I don't have a good FCD. This gives me the oppurtunity to get the Rtek!
I could wire up a FCD if I wanted but I'm kind of lazy. Especially after 8 months of working on this ******.
Lower secondary kick on,no FCD at all,timing retarded with boost?
Me likey!
Well!
Me had another thought.
Sinc I don't have a good FCD. This gives me the oppurtunity to get the Rtek!
I could wire up a FCD if I wanted but I'm kind of lazy. Especially after 8 months of working on this ******.
Lower secondary kick on,no FCD at all,timing retarded with boost?
Me likey!
Last edited by Digi7ech; 07-20-04 at 02:12 PM.
07-21-04, 12:01 AM
#13
I checked my timing I brought it to the edge without restabbing and I'm at 6degrees so I'm only 1 degree advanced.
The front leading plug was pretty dirty while the rear leading plug had some spark burn on it but not very much.
Me a little afraid the injector to the rear isn't doing it's full job.
The front leading plug was pretty dirty while the rear leading plug had some spark burn on it but not very much.
Me a little afraid the injector to the rear isn't doing it's full job.
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