My boost gauge and fuel press. say I have 20lbs of boost. The FAST data says I have 10. I have a 3 bar map and I have the FAST set for a 3 bar. I tried putting air press. to the map and then checked the data. It will only go to 18.5 no mater how much air press. I use.
FAST?? I need some help
- Thread starter SIXBANGR
- Start date
Craig Smith
That was easy!
- Joined
- May 25, 2001
You don't have a 3 bar sensor. Read the kPa reading with the engine off. It should be about 100. If it isn't, then your sensor isn't what you think it is. I bet this is the case.
- Joined
- May 28, 2001
3 bar map...?
100 kpa is right at zero boost, zero vac. Actually it's 99.
[99kpa is 14.7psi, aka sea level].
If I'm remembering correctly, your signature says 2200'.
IF you are at 2200', then the map will be less than 100.[99]
FWIW, the NHRA track guide shows the track at Vegas is at 2010'
As I recall, they start doing the altitude adjustments to indexes and records at about that altitude...
100 kpa is right at zero boost, zero vac. Actually it's 99.
[99kpa is 14.7psi, aka sea level].
If I'm remembering correctly, your signature says 2200'.
IF you are at 2200', then the map will be less than 100.[99]
FWIW, the NHRA track guide shows the track at Vegas is at 2010'
As I recall, they start doing the altitude adjustments to indexes and records at about that altitude...
Craig Smith
That was easy!
- Joined
- May 25, 2001
A MAP sensor should show absolute pressure. Higher altitude = lower pressure.
SIXBANGR, change the MAP sensor setting in C-Com until it reads about 100 with key on, engine off. I bet it's a two bar.
SIXBANGR, change the MAP sensor setting in C-Com until it reads about 100 with key on, engine off. I bet it's a two bar.
- Joined
- May 28, 2001
4400!!
Wow, 6banger! you are gonna have to add an oxygen system to your car, just to prevent blackouts when you race!! If the MAP reading is taken at 4400 and not at the 2200 you have in the sig, then I could see why the reading is REALLY low!
My info shows that the pt # you posted is a 3 bar. Hope they didn't switch boxes on you!
Back under my rock...
Wow, 6banger! you are gonna have to add an oxygen system to your car, just to prevent blackouts when you race!! If the MAP reading is taken at 4400 and not at the 2200 you have in the sig, then I could see why the reading is REALLY low!
My info shows that the pt # you posted is a 3 bar. Hope they didn't switch boxes on you!
Back under my rock...
- Joined
- May 28, 2001
More trivia!
Just went on Google and got the baro calc formulas for altitude.
Actually, I was wrong in reporting 99KPA was atmosphere at sea level. It's 101.3KPA. That converts to 29.92 = 760MMHG.
The formula calculated that at 4400 feet, the barometer, in KPA, will be 86.94 Still not down as low as you are reporting...
back to Craig's comment.. SURE it's a 3 bar????
Just went on Google and got the baro calc formulas for altitude.
Actually, I was wrong in reporting 99KPA was atmosphere at sea level. It's 101.3KPA. That converts to 29.92 = 760MMHG.
The formula calculated that at 4400 feet, the barometer, in KPA, will be 86.94 Still not down as low as you are reporting...
back to Craig's comment.. SURE it's a 3 bar????
Reno, at 4400 ft, should give you a static pressure reading of 85-90 kPa.
Now that is odd... trying to think of what the problem could be.
If you had a 1 bar sensor, the sensor would be sending a signal that was about 85% of max to the FAST box, and with a 3 bar setting in the FAST it would think you have a MAP of ~255 kPa.
Same reasoning with a 2 bar sensor, it would be sending a signal = 85/200 = 42.5% of max, which the FAST would see as .425x300 = 128 kPa.
Same reasoning with a 3 bar sensor, it would be sending a signal = 85/300 = 28.3% of max, which the FAST would see as .283x300 = 85 kPa.
Same reasoning with a 4 bar sensor, it would be sending a signal = 85/400 = 21.3% of max, which the FAST would see as .213x300 = 64 kPa.
Which is what you see. Could you have a 4 bar map sensor on your car? Do they make a 4 bar sensor? Can the FAST be set to see a 4 bar sensor?
John
Now that is odd... trying to think of what the problem could be.
If you had a 1 bar sensor, the sensor would be sending a signal that was about 85% of max to the FAST box, and with a 3 bar setting in the FAST it would think you have a MAP of ~255 kPa.
Same reasoning with a 2 bar sensor, it would be sending a signal = 85/200 = 42.5% of max, which the FAST would see as .425x300 = 128 kPa.
Same reasoning with a 3 bar sensor, it would be sending a signal = 85/300 = 28.3% of max, which the FAST would see as .283x300 = 85 kPa.
Same reasoning with a 4 bar sensor, it would be sending a signal = 85/400 = 21.3% of max, which the FAST would see as .213x300 = 64 kPa.
Which is what you see. Could you have a 4 bar map sensor on your car? Do they make a 4 bar sensor? Can the FAST be set to see a 4 bar sensor?
John
Also this:
you run 20 psi boost and see 10 psig on the data log.
20 psi boost = ~32.7 psia at your altitude. 32.7 psia = 225.4 kPa
A 4 bar sensor would send a signal of 225.4/400 = 56.36% of max.
A 3 bar setting in the FAST would see this signal as .5636 x 300 = 169.1 kPa.
The FAST would convert this to 169.1 / 101.325 * 14.7 - 14.7 = 9.8 psig
Which is what you see.
If you had a 2 bar sensor and a 3 bar software setting, once you got to 15 psi boost the FAST would be reporting a full 3 bar MAP, or ~29 psig.
John
you run 20 psi boost and see 10 psig on the data log.
20 psi boost = ~32.7 psia at your altitude. 32.7 psia = 225.4 kPa
A 4 bar sensor would send a signal of 225.4/400 = 56.36% of max.
A 3 bar setting in the FAST would see this signal as .5636 x 300 = 169.1 kPa.
The FAST would convert this to 169.1 / 101.325 * 14.7 - 14.7 = 9.8 psig
Which is what you see.
If you had a 2 bar sensor and a 3 bar software setting, once you got to 15 psi boost the FAST would be reporting a full 3 bar MAP, or ~29 psig.
John
According to Ken Moser, the new MAP I got with the new part#, is a 3 bar. I get 63 kpa with it and with the one I had. It also was supposed to be a 3 bar. I got out the orig. one that came on the car, I bought it new, And I get 91kpa. That one should only be a 2 bar.All 3 were with a FAST setting for a 3 bar. Key on, motor off.
Craig Smith
That was easy!
- Joined
- May 25, 2001
You have 3 2-bar MAP sensors.
Take a look in the connectors in the sensors. You'll see inside the connector that there are two or three little tabs that are supposed to line up with slots in the wiring harness connector. I'll bet you a buck that all three sensors have the same orientation and number of tabs. 1, 2, and 3 bar sensors all have different tab orientations. So if all three of them have the same tabs, they are all the same sensor.
This should help you arrive at the same conclusion that you would arrive at following John Estill's advice, only with a lot mess math!
How much boost are you running? If it's less than 15 psi, just use the 2 bar sensor. If you need a 3 bar sensor, you can get one from your FAST dealer. Part number is 30-7009.
Take a look in the connectors in the sensors. You'll see inside the connector that there are two or three little tabs that are supposed to line up with slots in the wiring harness connector. I'll bet you a buck that all three sensors have the same orientation and number of tabs. 1, 2, and 3 bar sensors all have different tab orientations. So if all three of them have the same tabs, they are all the same sensor.
This should help you arrive at the same conclusion that you would arrive at following John Estill's advice, only with a lot mess math!
How much boost are you running? If it's less than 15 psi, just use the 2 bar sensor. If you need a 3 bar sensor, you can get one from your FAST dealer. Part number is 30-7009.
All three have the same pins. The left one is at 9 o'clock. the center is at 12 o'clock. They are all 3 bar. Two of them are no good, including the one I just got Monday.The one I had in my old parts box says 91 kpa. It also has an orange connecter which the older 3 bar had. So thanks to every one who chimed in.
I hate to even bring this up again.I got another new MAP for a spare, since it appeared I had 1 good one and 2 bad ones. The new one also reads 63kpa. I did some voltage test. On the 3 that only read 63kpa, I get 1.39v out from the center wire. The one that reads 91kpa I get 1.99v. What should it be? Could the FAST be not working correct?
My understanding is that the signal is linear, and the range is 0-5V. So a 2 bar sensor at 100% of range (ie at a MAP = 2 bar) would have an output of ~5V.
If you are at key on, engine off, and see an output of 1.39V, then the sensor is at 1.39/5 = 27.8% of scale.
With your local air pressure at ~85 kPa,
85 kPa / 300 kPa = 28.3%
Sounds like 1.39V is about right for a 3 bar sensor where you are at.
On the oddball one, 1.99V / 5V = 39.8%
85 kPa / 200 kPa = 42.5%
Close enough, sounds like a 2 bar sensor.
John
If you are at key on, engine off, and see an output of 1.39V, then the sensor is at 1.39/5 = 27.8% of scale.
With your local air pressure at ~85 kPa,
85 kPa / 300 kPa = 28.3%
Sounds like 1.39V is about right for a 3 bar sensor where you are at.
On the oddball one, 1.99V / 5V = 39.8%
85 kPa / 200 kPa = 42.5%
Close enough, sounds like a 2 bar sensor.
John
The fact that they all have the same tab orientation and that one of them has an orange insert, leads me to believe you have 2 bar sensors. I have never seen a 3 bar with an orange plug. Stock GN's with 2 bar sensors have orange plugs.
How accurate is the VE table when you tell the FAST you have a 2 bar sensor?
That is all weird though. If you have a 2 bar sensor installed, but the FAST thinks it is a 3 bar, all your MAP readings should be too high, not too low.
For example, if you had a one bar sensor installed, but the software thinks it is a 3 bar sensor, key on/engine off should give you a MAP of ~255 kPa (~22 psi boost, at your altitude anyway).
To get readings that are too low, you have to have a sensor that has a bigger range than what the computer thinks it is, for example a 3 bar sensor with a 2 bar setting in the software.
So how is that happening to you? Puzzling...
John
For example, if you had a one bar sensor installed, but the software thinks it is a 3 bar sensor, key on/engine off should give you a MAP of ~255 kPa (~22 psi boost, at your altitude anyway).
To get readings that are too low, you have to have a sensor that has a bigger range than what the computer thinks it is, for example a 3 bar sensor with a 2 bar setting in the software.
So how is that happening to you? Puzzling...
John
The sensor with the orange connecter is a 2 bar. That is the one that read91kpa.The other 3 are 3 bar ,all of them are new. All 3 were bought from people that sell Buick stuff for a living. Hard to believe that 3 diff. venders sold me the wrong MAP. Any way, the 3 new ones all give me 1.38volts out and 63 kpa and 18lbs of boost max. I have set and reset the MAP settings. It is at 3. It looks to me like I am missing something or the FAST is only seeing a 2 bar. Car runs very good, just want to be able to adjust fuel and timeing for the boost I run.
Craig Smith
That was easy!
- Joined
- May 25, 2001
I'm sorry if this has gotten confusing for you.
Do this. Plug in one of the other 3 "questionable" sensors. Now, go online. Set it for one bar and see what the MAP sensor is reading. Now, set it for two bar and check, and do the same for 3 bar setting. One of the three will give you somewhere close to 100 kPa. Or, at your altitude, about 90.
Whichever of those three settings shows 90-100 kPa is what your MAP sensor is. Period.
This thing WILL run...
Do this. Plug in one of the other 3 "questionable" sensors. Now, go online. Set it for one bar and see what the MAP sensor is reading. Now, set it for two bar and check, and do the same for 3 bar setting. One of the three will give you somewhere close to 100 kPa. Or, at your altitude, about 90.
Whichever of those three settings shows 90-100 kPa is what your MAP sensor is. Period.
This thing WILL run...
