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Discussion Starter #1 (Edited)
So this fall, I was running the race car, and due to the I/C tank splitting and having to remove it to get welded back up, I forgot to hook the wires back up for the I/C pump. This happened on the last run on a Sat night, and I got the tank repaired overnight and re-installed Sun morning. During the the thrash to get everything back in and running for first round of eliminations, I forgot to hook up the wires to the I/C pump. Normally I turn on my I/C pump after the burnout and just before staging the car. On a normal run, I see high 60's*IAT temps at the beginning of the run and hit high 80's* IAT's at the end of the run. I usually see about 21 psi with a spike of sometimes 22 psi.
On this pass, due to the I/C pump not running, I started the run with an IAT of 170ish* and it pegged the IAT sensor at 255* and would not read any higher. As a result I saw 30 psi of boost!. Why? Before it hit 30 psi, the data-log shows about 24-25 psi and then the A/F just starts going dead rich. This is a fail-safe in the Fast XFI engine management system, needless to say, even though I was at WOT, the engine just fell on its face and the rpm's just plummeted. After that pass, hooked the I/C pump back up and a "test-n-tune" showed the boost numbers right in line with previous runs at 21-22 psi.

How is it possible to read a 8 psi higher boost reading? I am over-spinning the S/C as it is. Is it due to excessive heat in the air translating to more boost? Or is it the fact that the A/F went real rich and that made the boost number high, IE more fuel displacing air in the cylinder and causing the higher boost number? Everyone I have talked to kind of scratches their head, cause this should not happen.

Thoughts?
 

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Just a guess, as i did not do a calculation at this time

But i would look to a restriction at the time of rpm drop off,,maybe when all the fuel was dumped in
 

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Discussion Starter #3
Don't really see how there could be a restriction.

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Discussion Starter #5
Yup. There is no restriction in the fuel system either. Twin Aeromotive Eliminator pumps, -12 feed up to the engine compartment, Y block to -8 feeds to the front of both fuel rails, -8 out of the back of the fuel rails to the regulator and -10 back to the tank. 40 psi base pressure. 1:1 on the regulator. Precision Turbo 225 lb/hr fuel injectors at 64% duty cycle at the end of the run. You can see both pumps at the rear of the car in this pic.



And let me reiterate....the next pass with the I/C pump running, my boost level went back to normal, 21-22 psi.
 

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What was your AFR when the IAT's went thru the roof? What fuel do you run? And what are your normal AFR's in boost. Do you raise fuel pressure in boost? Food for thought if your fuel pressure goes up.
 

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Yup. There is no restriction in the fuel system either. Twin Aeromotive Eliminator pumps, -12 feed up to the engine compartment, Y block to -8 feeds to the front of both fuel rails, -8 out of the back of the fuel rails to the regulator and -10 back to the tank. 40 psi base pressure. 1:1 on the regulator. Precision Turbo 225 lb/hr fuel injectors at 64% duty cycle at the end of the run. You can see both pumps at the rear of the car in this pic.



And let me reiterate....the next pass with the I/C pump running, my boost level went back to normal, 21-22 psi.
if boost went up, why are you showing me the inlet?
 

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Discussion Starter #8
I run Pro E85 from Renegade Fuels. The fuel pressures rises 1 psi for every pound of boost. The target A/F ratio is 7.8:1 under boost. By the time the datalog showed boost at 30 psi, the A/F ratio was about 5.8:1 due to the Fast XFI engine management system going into "protect" mode due to the high IAT. I will go revisit the data log to be sure I am correct on the A/F part.
 

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Discussion Starter #9
if boost went up, why are you showing me the inlet?
IDK, some mention of a restriction. Did not make much sense at the time, but you have unique ways of looking at things and I just responded with the first thing that popped into my head. Either that or I am a picture whore....:wink2:
 

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did your fuel pressure rise to reflect the 30 psi? in other words did it rise the extra 9 lbs too? so you are asking if the extra fuel raised the boost pressure?
 

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IDK, some mention of a restriction. Did not make much sense at the time, but you have unique ways of looking at things and I just responded with the first thing that popped into my head. Either that or I am a picture whore....:wink2:
let me add a unique way

your boost gauge is measuring boost where?

im gonna bet not in the inlet.

and if there is a restriction causing boost to rise, I am sure not going to look up stream for a restriction
 

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Discussion Starter #12
That is all well and good, but there is no restriction to look for. There is something else in play is my guess.
 

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Discussion Starter #13
did your fuel pressure rise to reflect the 30 psi? in other words did it rise the extra 9 lbs too? so you are asking if the extra fuel raised the boost pressure?
My working theory is that the extra fuel displaced air, thus resulting is a rise in pressure, although I really doubt that is the case. I do not data-log fuel pressure. I watch the A/F numbers and the % of correction as the system adjusts for the target A/F that is programmed in. The other thing that I am looking at is the extreme rise in IAT was a factor in creating a higher boost number, or at least had an effect on the 3 bar MAP sensors readings. There is no other possibility, as all of the other data-logged items show within normal parameters. On top of that, the incremental numbers on the time slip do not show a performance gain by the increase in boost pressure numbers. At approx 35-37 hp gain per lb of boost, one would assume that the car would really have been moving with the extra hp provided by the increased boost.
 

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the theory you came up with, is exactly what i was thinking and asking. i just didn"t convey it correctly. i agree with your theory so i guess that makes two of us that are probably wrong! lol
 

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Is your WG's measuring boost after the IC or before the IC?
Heating air up will increase pressure and if the WG's aren't measuring the extra pressure that is at the manifold due to the heating/expansion of the inlet air then the WG's are still measuring the air psi as being perfectly normal.

ks
 

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Discussion Starter #16
Is your WG's measuring boost after the IC or before the IC?
Heating air up will increase pressure and if the WG's aren't measuring the extra pressure that is at the manifold due to the heating/expansion of the inlet air then the WG's are still measuring the air psi as being perfectly normal.

ks
WG? don't know what that is. :confused: My 3 bar MAP sensor is measuring boost after the I/C. The data-logger records boost based on the MAP sensor reading. During a dyno session I data-logged boost pressures before and after I/C and saw only a 1 1/2 psi drop across the I/C. Does that hold true going down track at speed compared to strapped to a dyno IDK.
 

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WG? don't know what that is. :confused: My 3 bar MAP sensor is measuring boost after the I/C. The data-logger records boost based on the MAP sensor reading. During a dyno session I data-logged boost pressures before and after I/C and saw only a 1 1/2 psi drop across the I/C. Does that hold true going down track at speed compared to strapped to a dyno IDK.
Where are the Waste Gates (WG's) measuring the boost signal at? Before or after the IC?

ls
 

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My working theory is that the extra fuel displaced air, thus resulting is a rise in pressure, although I really doubt that is the case. I do not data-log fuel pressure. I watch the A/F numbers and the % of correction as the system adjusts for the target A/F that is programmed in. The other thing that I am looking at is the extreme rise in IAT was a factor in creating a higher boost number, or at least had an effect on the 3 bar MAP sensors readings. There is no other possibility, as all of the other data-logged items show within normal parameters. On top of that, the incremental numbers on the time slip do not show a performance gain by the increase in boost pressure numbers. At approx 35-37 hp gain per lb of boost, one would assume that the car would really have been moving with the extra hp provided by the increased boost.

DID you increase boost by increasing the CFM of the supercharger?

you said its running the same speed.........you did nothing to increase CFM...so BOOST

its a measure of a restriction, your PRESSURE WENT up because downstream of the SC was an increase in RESTRICTION

you just showed that, and its one of the most misunderstood concepts

So when you say, NO restriction to be had, i don't see it.......its just you not being able to see it, its there

if you were to measure CFM..........you can calculate from MAF and press ratio and temp, you would have seen a decrease in it compared to your lower normal boost levels


think pressure washer......
 

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Discussion Starter #19
Where are the Waste Gates (WG's) measuring the boost signal at? Before or after the IC?

ls
Positive displacement S/C. Kenne Bell 2.8L. Do not use waste gates. I use two BOV's for the boost controller. The BOV's are on the outlet to the S/C before the I/C core, the MAP sensor is after I/C core.

 

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Discussion Starter #20
DID you increase boost by increasing the CFM of the supercharger?

you said its running the same speed.........you did nothing to increase CFM...so BOOST

its a measure of a restriction, your PRESSURE WENT up because downstream of the SC was an increase in RESTRICTION

you just showed that, and its one of the most misunderstood concepts

So when you say, NO restriction to be had, i don't see it.......its just you not being able to see it, its there

if you were to measure CFM..........you can calculate from MAF and press ratio and temp, you would have seen a decrease in it compared to your lower normal boost levels


think pressure washer......
Any "restriction" was the result of an increase in fuel delivery into the cylinder (not likely) or an increase in IAT. 2,350 cubic feet of air (arbitrary #) at 60*F is going to occupy less area than 2,350 cubic feet of air at 255+*F. Put the 255+*F air into the same container as occupied by 60*F air and the pressure would go up.
See I just answered my own question....>:)
 
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