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?

 

The calculations are either off or they allow for over 100% IDC.

I have over 500whp on stock 560's and meth injection. Granted meth takes up some DC, it still illustrates what is possible on stockers.

 

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.

 

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

 

I am in no way telling you to do this, but if it was my own hard work and money I would feel comfortable with the logging gear I have from ZEITRONIX to go ahead any push it until is starts to lean out on top, ignoring any input from me richening it in the programming.

Furthermore you are babying it on 93 octane, 19psi and 10.9 AFR.

 

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

 

Would adding a walbro 255lph lower the %, anybody?

 

Not directly. Raising the baseline fuel pressure can increase fuel delivery and allow the IDC to be scaled back, but adding an Walbro wouldn't significantly raise the fuel pressure all by itself. An adjustable fpr would need to be added too. I imagine that the ECU would need to be adjusted for an effectively larger injector when the fuel pressure is raised.

 

Via injector scaling or modifying the cells themselves, correct.

 

At 7000 rpm, the car is pushing about 20-20.5 psi.

 

how are you monitoring your boost? if you're at a tapered 20.5 psi, i imagine you are peaking around 25 psi or so?

 

What is your peak boost (must be greater than 22psi) and how did you achieve that via the ECU? I cannot seem to get more than 22 psi tapering to ~17 - 18 by 7600 rpm.

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

 

I dont think our stock heads flow over 230cfm, atleast that is what I have seen from other peoples post on this board. So I would say VE is def. below 90%. I think I saw a comparison between stock heads and the Cosworth head, and in that comparison the stock heads did not flow no higher then 227cfm in a lift range our cams dont even reach.

I guess your right fortunately for our stock injecters our car appears to restrictive to reach a VE/boost high enough at 7500rpm.


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.

 

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.

 

Maybe someone can use EvoScan and another logger back to back and compare the IDC numbers to see if EvoScan is accurate