93%-98% duty cycle on Evo IX with just a mail-in flash?
#1
93%-98% duty cycle on Evo IX with just a mail-in flash?
I've been tinkering around a bit more with EvoScan and finally got around to calculating IDC from IPW (IPW*RPM/1200), and I'm getting 92-97% duty cycle at WOT 7000 rpm with just a mail-in flash on my Evo IX. Calculated load at 7000 rpm is 220-225. I'm a bit surprised at the high IDC values because although I'm running more boost at 7000 rpm, the fuel map in the mail-in is about 1 point leaner than stock. Seems like there's no room for exhaust or other mods with the stock injectors which seems unbelievable considering that there are lots of folks running around with flashes and TBEs on their IX. Either that or the IPW value in EvoScan is off. Anyone have any insight here?
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TTP, what do you think the stock injectors are good for without meth to make up some headroom. Reason I ask is I'm running 19 psi on my 35R w/ the stocker injectors and while the IDCs are up there, the car still has fuel as I have it dipping into the very high 10s above 7k rpms (call me paranoid ). The car pulls like a relative freight train and I know the correct airflow is there as the ecu hops up into the 280s load-wise with 19 psi of boost.
#4
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The IPW numbers may very well be off, but the numbers may very well be valid, too. What sort of boost are you running?
Doing some quick math on the stock injectors to see how much airflow they can support:
560cc/min injector
specific gravity for fuel = .76, so 560 cc fuel = 560*.76 = 425.6 g/min fuel
four injectors = 425.6*4 = 1702.4 g/min fuel
assume 11:1 A:F for pump gas
So, the amount of air that can be support is 1702.4 * 11 = 18726.4 g/min of air
454g/lb, so that is 41.25 lb/min of air
So, this all means that at an 11:1 A:F, the stock 560cc/min injectors can support an airflow of about 41 lb/min, or roughly 410HP, using the common 10HP per lb of airflow.
It all depends on how much mass airflow you are pushing.
Eric
Doing some quick math on the stock injectors to see how much airflow they can support:
560cc/min injector
specific gravity for fuel = .76, so 560 cc fuel = 560*.76 = 425.6 g/min fuel
four injectors = 425.6*4 = 1702.4 g/min fuel
assume 11:1 A:F for pump gas
So, the amount of air that can be support is 1702.4 * 11 = 18726.4 g/min of air
454g/lb, so that is 41.25 lb/min of air
So, this all means that at an 11:1 A:F, the stock 560cc/min injectors can support an airflow of about 41 lb/min, or roughly 410HP, using the common 10HP per lb of airflow.
It all depends on how much mass airflow you are pushing.
Eric
#5
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Originally Posted by A418t81
TTP, what do you think the stock injectors are good for without meth to make up some headroom. Reason I ask is I'm running 19 psi on my 35R w/ the stocker injectors and while the IDCs are up there, the car still has fuel as I have it dipping into the very high 10s above 7k rpms (call me paranoid ). The car pulls like a relative freight train and I know the correct airflow is there as the ecu hops up into the 280s load-wise with 19 psi of boost.
Furthermore you are babying it on 93 octane, 19psi and 10.9 AFR.
#6
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To find the airflow through an engine, you can use the following equation:
Airflow(CFM) =
RPM*VE*Cid
2*1728
Then multiply that by the PR. The pressure ratio is simply the amount of boost pressure + 14.7, all over 14.7
So, 22 psi for example, would be (22+14.7)/14.7= 2.5 PR
Using 7500 RPM, a VE of 90% and our Cid of 122 for a 2 L engine, the airflow would be:
7500*.9*122/(2*1728)=238.3 CFM
Multiply by 2.5 PR (for a boost of 22 psi)
2.5 * 238.3 = 595.75CFM
Now, to get CFM to lb/min, multiply by about .0756 (for standard temp and press)
595.75 * .0756 = 45 lb/min
Perhaps the VE is too high in this equation for our engines at 7500 RPM...it is probably more like .8 or so, but you get the point. You can flow more at 22psi than the injectors can support if your VE is high enough, your boost is high enough, or you rev high enough.
Eric
Airflow(CFM) =
RPM*VE*Cid
2*1728
Then multiply that by the PR. The pressure ratio is simply the amount of boost pressure + 14.7, all over 14.7
So, 22 psi for example, would be (22+14.7)/14.7= 2.5 PR
Using 7500 RPM, a VE of 90% and our Cid of 122 for a 2 L engine, the airflow would be:
7500*.9*122/(2*1728)=238.3 CFM
Multiply by 2.5 PR (for a boost of 22 psi)
2.5 * 238.3 = 595.75CFM
Now, to get CFM to lb/min, multiply by about .0756 (for standard temp and press)
595.75 * .0756 = 45 lb/min
Perhaps the VE is too high in this equation for our engines at 7500 RPM...it is probably more like .8 or so, but you get the point. You can flow more at 22psi than the injectors can support if your VE is high enough, your boost is high enough, or you rev high enough.
Eric
#7
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Originally Posted by mrfred
I've been tinkering around a bit more with EvoScan and finally got around to calculating IDC from IPW (IPW*RPM/1200), and I'm getting 92-97% duty cycle at WOT 7000 rpm with just a mail-in flash on my Evo IX. Calculated load at 7000 rpm is 220-225. I'm a bit surprised at the high IDC values because although I'm running more boost at 7000 rpm, the fuel map in the mail-in is about 1 point leaner than stock. Seems like there's no room for exhaust or other mods with the stock injectors which seems unbelievable considering that there are lots of folks running around with flashes and TBEs on their IX. Either that or the IPW value in EvoScan is off. Anyone have any insight here?
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#8
Originally Posted by C6C6CH3vo
Would adding a walbro 255lph lower the %, anybody?
Last edited by mrfred; Sep 14, 2006 at 10:24 AM.
#11
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Originally Posted by mrfred
At 7000 rpm, the car is pushing about 20-20.5 psi.
#12
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Originally Posted by mrfred
At 7000 rpm, the car is pushing about 20-20.5 psi.
Also, is anyone seeing their boost climb to ~20 (at a fast rate) and then slowly climb to 22 and then start to taper? It is almost like I have lazy boost? Thanks
#13
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Originally Posted by l2r99gst
Airflow(CFM) =
RPM*VE*Cid
2*1728
Then multiply that by the PR. The pressure ratio is simply the amount of boost pressure + 14.7, all over 14.7
So, 22 psi for example, would be (22+14.7)/14.7= 2.5 PR
Using 7500 RPM, a VE of 90% and our Cid of 122 for a 2 L engine, the airflow would be:
7500*.9*122/(2*1728)=238.3 CFM
RPM*VE*Cid
2*1728
Then multiply that by the PR. The pressure ratio is simply the amount of boost pressure + 14.7, all over 14.7
So, 22 psi for example, would be (22+14.7)/14.7= 2.5 PR
Using 7500 RPM, a VE of 90% and our Cid of 122 for a 2 L engine, the airflow would be:
7500*.9*122/(2*1728)=238.3 CFM
Originally Posted by l2r99gst
Multiply by 2.5 PR (for a boost of 22 psi)
2.5 * 238.3 = 595.75CFM
Now, to get CFM to lb/min, multiply by about .0756 (for standard temp and press)
595.75 * .0756 = 45 lb/min
Perhaps the VE is too high in this equation for our engines at 7500 RPM...it is probably more like .8 or so, but you get the point. You can flow more at 22psi than the injectors can support if your VE is high enough, your boost is high enough, or you rev high enough.
Eric
Theoretical air flow would be 2.5 * (10/9)(238.3) = ~660cfm
Actual flow rate = (flow rate at 7500rpm lb per min.)/ (Density of air for the intake lb/ft3)
VE = (Actual flow rate) / (Theoretical air flow rate)
VE = (?????????) / 660cfm
*This is still assuming we are boosting at 22psi.
Last edited by heyzeus11; Sep 14, 2006 at 06:38 AM.
#14
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On pump gas 11:1 I'm at 100% IDC according to DSMLink.
My AFR's lean out to 12:1 up top regardless of whether I add fuel with the sliders or not.
On 110 leaded I still have room to grow.
I only used DSMLink for S&Gs. I prefer my XEDE for daily driving and road racing.
My AFR's lean out to 12:1 up top regardless of whether I add fuel with the sliders or not.
On 110 leaded I still have room to grow.
I only used DSMLink for S&Gs. I prefer my XEDE for daily driving and road racing.