That depends on what S/C you're getting. The screw or roots type blowers already remove the CMCPs. However, if you're getting a centrifugal, then you definatley will want to get the CMCP delete kit.

 

Hi FuriousGeorge,

In the past Iposted that I thought that if you are planningfor a blower that going with1 3/4" sized primary headers might bethe better choice. This made good sense as the exhaust flow is much higher with a supercharged engine. But something about this thinking was amiss when looking at the dyno results ofmotors with big primary tubes and open exhaust both N/A and blown.

Recently I have seegood dyno evidence that the 1 5/8" primary headers are all that you need on the 3-valve 4.6l motor. I have a few of the classic books about exhaust system design and in doing the math it seems that even with an exhaust system that is pretty quiet on the street a set of long tube headers with 1 5/8" primay tubes should be more than enough for our 3-valve4.6l motors.Even blowna good set oflong tube headers will flow more thanour4.6l motors canuse and that 1 3/4" primary headers actually lose power and torque. This is the same issue I have seen with people running open headers even 1 5/8" headers, they lose power! There appearsto be a need for some small amount of back pressure or reflective wave in the exhaust systemto help keep the fresh charge in the cyclnder and not flowing out the exhaust ports. For 4.6l 3-valveheader primary pipes at least,smaller the sizeseems to work better.

HTH

 

Regarding the headers it all depends on boost. If you are running under 8 psi then the 1-5/8 will work better, but if you are running over 14 psi then you would want to get something wider. I think the only reason they say they dont recommend them is because they dont stock FRPP ones because FRPP wont cut the price for them because they are a lot of dealers of FRPP in the area. This was told to me by Brent himself; same thing for the gears. That is why I recommend any other tuner here than Brent because they actually update your tunes. From brent they "update the tune" but I know someone that installed LT's that he bought from them and he said no update req. Pulleys/exhaust don't need update. And cams/F-I I would recommend getting a dyno tune. So after the first cai/tune I can't think of a mod that he will update for free.

Att. Andrew

 

Agreed on the size of the headers. Unless you're going 500hp+, the difference between 1 3/4 and 1 5/8 is negligible.

In reference to the FRPP CMDPs and Brenspeed, good info, I didn't know that. I was wondering why Brent wasn't offering them. Seems to be out of his control.

Both Brent and Doug (B a m achips) told me a tune is not required for LTs alone, as long as they are catted. O/R needs a tune. This was an issue for me since I had the CMDP tunes from both of them, but my CMDPs were damaged when I got them and I wanted to install my LTs. Based on their info, I installed the LTs, kept running their tunes (not the CMDP tunes) and everything was fine for a couple of weeks until I got my CMDPs.

As long as a person bought a tuner from Brenspeed and buys additional parts from them that require a tune...he will offer a free tune for those parts. As long as you buy a tuner from B a m achips, he will offer new tunes for free. For me Brenspeed works well because his inventory of parts just keeps growing and he ships to APOs for free. Plus Brent's tunes are awesome. But I do run Doug's tunes as well.