Contour Enthusiasts Group Archives Forums Modifications Duratec Performance secondaries

Another way to look at both sides is efficiency. Yes, HP, but what about fuel usage? An efficient engine usually makes more power...It sounds like proper cylinder filling etc has a lot to do w/ efficiency. What if we had the same driver/car driving about w/ setup A, then the next week the same driver/car driving about w/ setup B. Test fuel consumption, see which is better.
Am I way off? If so...I'll just shut up and read these threads instead of contributing.

Efficiency... let me start by saying that I completely believe Terry when he says cylinder filling is better at low-rpm with the stock IMRC system.

That being said, my fuel economy has been very good, and very consistent since performing the IMRC delete. 24mpg around town, 31mpg highway, and 27.2 overall for the last 2000 miles. Previously, I would average 19 city/25 highway/22 overall.

On the other hand... my cars emissions seem to have increased substancially. The car has no cats, but you would never have guessed it before. Now it smells very rich, and people often comment on the smell. :rolleyes:

So, in conclusion... less of the fuel that goes into the cylinders gets burned, but I've been getting night-and-day better gas mileage in spite of it. Go figure!

That's not true either.

We both agree that low rpm efficiency is hurt by this mod.
I just state that it is well within my acceptable limits for all the added benefits.

I can also tell you that before the UIM & LIM mods and just with the secondaries pinned the engine would come alive around 2800rpm. Airflow data and A/F readings below that would be degraded from running the system normally.

After my mods the power and data shows that 2450-2500rpm is now the point the engine surpasses the data for a normally operating IMRC system.

Either level was within my tolerance range and the lower level is even better. I also make a bit more power than the average SVT so my losses may still be above everyone's averages???

Like Frank said, my mileage is atleast the same if not a little better so add that to the big list of benefits. (throttle response, instant acceleration after a shift, no heat soak lag, etc)

I agree! Go figure! I'm always up for a mod that increases MPG. Too bad I drive at low RPMs...

this is wat i did: i pinned the secondaries and i removed the moose, the car runs alot better more freely and has more power. but some people say pinning the secondaries u lose power under 2500rpm so get the best of both worlds by pinning one of the secondaries and let the mechanical one work its self. let me know wat happens

In my non-SVT Duratec, there was a huge loss in power below 3000 with the secondaries pinned. It did pick up much better in the midrange though. Just proof that the secondaries are restrictive.....to a point.