I recently picked up an EVOMS V-flow intake. Other than some fitment issues, I had only heard good things about the intake so I thought I'd take the plunge. As others have alluded to, there are issues with fitment. See my other thread in which I'm trying to sort things out.

This morning I decided to give it a shot even with fitment issues. I was honestly hoping to see/hear no difference to give myself an excuse to pull it out of the car and sell it. The fitment issues annoy me and now I need to find solutions.

I was changing over from a BMC filter in the stock housing (orange cap mod) to the V-flow setup in my 2001 C4. I took each setup out on the road and logged the rpm, air temperature, and mass air flowrate (stock MAF). I gave the car the same warm up in both cases and took the measurements over the same stretch of road. I did two pulls from ~3000rpm to ~6000 rpm with each setup. I would have liked to have done more and taken more data at each rpm but the situation didn't allow for that. I also would have liked to have take the data on the same day and temperature but again the fitment issues stopped me from collecting the data on the V-flow yesterday. There was a 10 degree temperature difference between yesterday (warmer-BMC) and today. This temperature difference was reflected in the intake air temperatures almost exactly. That said, I believe hot wire MAF's account for temperature in their measurement of mass so this shouldn't be an issue.

It looks like there is no difference below 4000 rpm but above that value you pick up about 5% more flow. I was extra conservative in calculating this 5% (two close data points were averaged for Vflow and the higher BMC value was used).

I did some quick efficiency calculations and roughly this intake increases the volumetric efficiency of the engine from the 90-95% range to the 95-100% range.

I didn't notice any improvement in sound.

I still wish it fit better, but I'm pretty convinced that you're getting more airflow with this intake. Assuming that ECU can compensate with additional fuel you should be making more power from 4000 rpm and up.

-Shawn

 

One question:

If you have more than one set of points, did you also take the standard deviation aside from the average of those points?

Seeing the standard deviation (sigma) would also be interesting aside from the average values. You can set the stdev to the chart also, which will show you and error (variation) within the data.

 

Ah nevermind, I now understand your post. You only have one set of datapoints for each filter. So sigma cannot be obtained from a sample size of 1.

 

Anree, that's a good point. If I had multiple sets of data with nice fixed rpm points that's exactly what I would have done. There are two sets of data for each filter but I just put them all on one plot grouped because I didn't have nice rpm set points. I would have to plot both x and y error bars which weren't that meaningful (only n=2) and I felt like they would confuse people. Just to give you a rough feel, the Vflow data is plus or minus about 2.5% and the BMC data is plus or minus 2%. Given those numbers the difference is probably real, but I wouldn't bet my job on it.

 

Interesting. Thanks for collecting the data!