Thunderheader Torque Dip & pinging problem

[greghj]

Just found this site - awesome!

I have an 05 Road King with 95" kit (SE flat top pistons, S&S 570 gear drive cam, SE performance heads, Fueling oil pump & lifters, P.C.III and Thunderheader 2 into 1). It dyno'd at 98 torque & 95 H.P. Overall it runs great, but I have a significant torque dip around 2800 RPM that I'm told is due to the Thunderheader pipe. With the SE 6 speed trans that I also have, it's very noticable - seems like I have to be over 3100 rpm's to even use 6th gear or it bogs down. I'm also experiencing pinging around that same RPM range (2500-3000) when the bikes under heavy load. Any way to correct through tuning or other methods? Thanks.

[Mike]

The torque dip is typical for the Thunderheader and can be greatly improved by bending over two or three of the flat vanes of the baffle up against the outside from the middle putting some back pressure into the system, This will reduce peak hp a little but is worth the gain in torque. Of course mapping should be changed to fully optimize the exhaust.

The pinging is common to 2 into 1 exhaust as they tend to hold heat at the merge collector (folding the baffles does not seem to increase this as one might expect). This is a tuning issue and should be ably handled by the PC. It may mean sacraficing a little fuel milage from the added fuel and retarded timing. Your combo is a good one and just needs a little TLC.
Mike

[greghj]

Thanks for the info Mike, I appreciate your time. One last quick question, I'm told by a few folks that the SERT could do more for me in curing this problem than the PCIII (with a good dyno tech of course). What's your opinion and do you think it's worth the added expense?

[Mike]

I do not normally tell people to change to SERT if they've already invested in a PC, so long as that PC is the USB version. The USB PC has "advanced mode" tuning, which means you can tune each cylinder independently (similar to SERT) and it is this capability that allows you to minimize those torque dips. If you do not have the USB version and your goal is to reduce the dips, it is argueable that the SERT would be worth the investment. The dyno time for SERT and Avanced Mode PC tuning is similar (depending on the tuner's skill). Agian, those dips are a function of the pipe and cannot be fully eleminated through tuning but, depending on how far off the tune is, they can often be reduced by the amount that tuning correction allows.
Mike