Contour Enthusiasts Group Archives Forums Modifications Duratec Maintenance remove secondary intake runners?

Originally posted by DemonSVT:

---

Your thinking is definitely on the right track & the flow theory is sound. However you are a bit flawed your basis.

The stock manifold setup was designed for a 170HP engine and the fact it would be primarily mated to a slushbox. Also the UIM was a compromise to fit under the stock hood. (It was EH'd for moderate flow improvement and port uniformity for the SVT)

Now about the IMRC. The rpm range of "just the short runners" drops drastically as you improve the efficiency of the engine and attached parts. (i.e. mods) The more modified the engine is beyond the stock 170HP slushbox range the lower the maximum rpm range of the short runners will be. There comes a point where the rpm range of the short runners is below even cruising range. Albeit, like you said, not on the stock engine or one close to stock. This rule of flow dynamics is part of the reason why an SVT has a 400-600rpm lower IMRC point even though the engine has a higher powerband due to the cam change. At a lower RPM point it needs more air then "just the short runners" can supply. That's even considering the bit of flow improvement the EH process added to the short runners.

---

Did you know that I'd pop up on this???

I am in agreement except on the sticking point where you imply that the plates have to be removed for performance.
No, not really.
For naturally aspirated performance it is very important to keep the runners operational.
If you increase the airflow requirements for that engine then you need to enlarge your runners accordingly.
Removing them is only a viable option if you are having problems with your system.
Flutter, or coding problems that cause unnecessary opening and closing are important. When my secondaries weren't clean I had issues with the IMRC not being able to open them and it really sucked.

However, after I removed them and properly enlarged and modified them when I went to 3.0 liters of displacement I never had a problem. In fact, they complemented the 3L so well that I would never remove them naturally aspirated! I had them pinned open for testing purposes back when I was having a lot of driveability issuse and it really sucks away the low rpm torque, EVEN with a 3L. For me it turned out to be bad plug wires that were really hurting me.
On top of that, I opened my IMRC box and cleaned it up checked connections, etc. I still use my original in the stock location and it works great! No more sticking secondaries. Less manifold cleanings. Etc.

Wow, should I actually give away my secret for success??
I've explained to you in detail what I have done and you have seen the torque curves from the dyno graphs. You know as well as I do that the torque curve is going to tell you the most about whether your secondaries are helping or hurting. You can't argue that my torque curve wasn't as flat as a table top with very slight, almost non-existent torque drop where the secondaries open.

Originally posted by warmonger:

---

I am in agreement except on the sticking point where you imply that the plates have to be removed for performance.
No, not really.
For naturally aspirated performance it is very important to keep the runners operational.
If you increase the airflow requirements for that engine then you need to enlarge your runners accordingly.
However, after I removed them and properly enlarged and modified them when I went to 3.0 liters of displacement I never had a problem. In fact, they complemented the 3L so well that I would never remove them naturally aspirated!
I had them pinned open for testing purposes back when I was having a lot of driveability issuse and it really sucks away the low rpm torque, EVEN with a 3L. For me it turned out to be bad plug wires that were really hurting me.
Wow, should I actually give away my secret for success??
I've explained to you in detail what I have done and you have seen the torque curves from the dyno graphs. You know as well as I do that the torque curve is going to tell you the most about whether your secondaries are helping or hurting. You can't argue that my torque curve wasn't as flat as a table top with very slight, almost non-existent torque drop where the secondaries open.

---

For starters I never said you "had to" remove the rods & plates for performance. I did say that removing them eliminated the turbulence they cause right before the head inlet. Turbulence like that is always bad.

Your 3L is a perfect example of why to remove them. Your 3L showed NO MORE POWER down low then my 2.5L engine (way back when) that also had an operational IMRC. That means they were of no help to your 21% larger engine because mine had the same power output. (i.e. the short runners limited power, plain & simple. Even with you modifications to the manifolds)
Well outside of maybe a little drivability help when tractoring below 2000rpm. I have one word for that though, "DOWNSHIFT!"

I hate to do this to you Tom but that comment about pinning them is pointless. No @%$#^)$ @$#@ you had issues just pinning them. No surprise there. That's not a valid argument at all in this topic. Then to boot your whole problem was wires... 'nuff said.

Above your power curves. See above. Below the IMRC point they were just like my 2.5L engine. Way back before any real mods too. (just intake, MAF, & exhaust) That's more then enough proof to show the limiting ability of just the short runners.

Face it Tom. You are here again now the same thing I said when we first talked about your numbers. There is no real discernable difference between my, then basic bolt on, 2.5L and your full port & polish high compression 3L below the IMRC point. That itself says volumes more then anything I could ever type.

The IMRC is for drivability only. Something it does quite well on the small 2.5L and is a must for the slushbox. It serves no other valid purpose though. There is just no valid supporting argument otherwise.
It does cause countless other issues though. The performance of the engine without one if infinitely better at ANY THROTTLE POSITION (not limited to WOT ) and any rpm above 3000. (of course a lower rpm range for a well modified engine or any 3L)

Originally posted by DemonSVT:

---

Oh yeah you big meany head.

My NA car is still quicker then your turbo car. (either of them actually ) What does that say?


Also that should be "stay out of little kid talk, man" Remember I was the one with low end torque in the 2.5L engine. That's manly.

---

Hahahaha! too funny.
Now I gotta get my sorry arse to work today.....someone (else) failed to plan right and I gotta suffer for it.