Dyno Shoot Out - Megabomb+PC4 vs Stock Header+DG-R
#21
06-07-2014, 04:48 AM
Good write up. If I was using logic(I know-what a thought) the best cost effective improvement you can make for performance is a 351 kit. That by itself transforms the bike-adding the other bits make small improvements but pale in comparison on bang for the buck of the added cubes.
#22
06-07-2014, 05:30 AM
Join Date: Jun 2013
Location: North Texas
Posts: 3,189
I understand your reasoning GBAUTO. A BB kit + dynojet kit is what, $550 - $575. Bills' figures for a stock engine/bike with the 351 is about 1 more HP and 3 more lb ft of torque than what I have now. The full FMF and dynojet kit are also around $575. The bike is low miles , like new, and doesn't need to be torn down for , hopefully, a very long time. I do acknowledge, however, that a stock bike with BB 351 would out perform mine and probably not need the added expense of a clutch upgrade.
#23
06-07-2014, 02:21 PM
Red Curves - Stock Header (port matched) + DG-R Cost: $150.00
Blue Curves - Full FMF, Megabomb + Power Core 4 Cost: $530.00
Test Notes:
DynoJet Dyno, roll-on, runs, SAE CF (which corrects for air temp, humidity, altitude, and engine temp.) Bike was run hot with no tricks to inflate numbers. Runs were only minutes apart -( I changed exhaust systems with welders gloves.) The full FMF system was run first.
Setup notes :
Please see my signature line for the modification status of my bike.
The AFR's are finally within reasonable tolerance for max power production. It took the #132 jet and raising the needle one notch above Stage 2 instructions to finally stop the bike from running too lean.
With the DG-R and stock header, deceleration popping is now occurring after raising the needle. Obviously decel popping is not a trustworthy indication of a too rich AFR - quite the contrary, it seems, decel popping is an indication that you are no longer running your bike lean. I can only assume fuel is being siphoned past the (now raised position) needle upon deceleration through the main jet.
Let the analysis begin !
Blue Curves - Full FMF, Megabomb + Power Core 4 Cost: $530.00
Test Notes:
DynoJet Dyno, roll-on, runs, SAE CF (which corrects for air temp, humidity, altitude, and engine temp.) Bike was run hot with no tricks to inflate numbers. Runs were only minutes apart -( I changed exhaust systems with welders gloves.) The full FMF system was run first.
Setup notes :
Please see my signature line for the modification status of my bike.
The AFR's are finally within reasonable tolerance for max power production. It took the #132 jet and raising the needle one notch above Stage 2 instructions to finally stop the bike from running too lean.
With the DG-R and stock header, deceleration popping is now occurring after raising the needle. Obviously decel popping is not a trustworthy indication of a too rich AFR - quite the contrary, it seems, decel popping is an indication that you are no longer running your bike lean. I can only assume fuel is being siphoned past the (now raised position) needle upon deceleration through the main jet.
Let the analysis begin !
#24
06-07-2014, 09:53 PM
Join Date: Jun 2013
Location: North Texas
Posts: 3,189
Thanks Cmott426, I'll recheck everything when I put the FMF stuff back on . I also need to check carefully that decel popping is not occurring with the FMF stuff.
#26
06-08-2014, 04:39 AM
Join Date: Jun 2013
Location: North Texas
Posts: 3,189
Well, Matt, you and I know all about the sound of the DG-R. We both like it. The Megabomb with the Power Core 4 is also very loud - too loud is a more appropriate description for both exhausts.
The DG-R , from idle to WOT is a "in your face", "bad boy" sound.
The FMF has a different quality to it. It is not quite as bad a$$ as the DG-R just putting around. At WOT the FMF quickly ramps up into a nasty DG-R like howl. Pin WOT and I can hear intake noise briefly before the FMF drowns it out - very different from the DG-R.
I've decided I like the FMF sound better - but not by much and not enough to spend 500+ to get the sound over the DG-R.
The DG-R , from idle to WOT is a "in your face", "bad boy" sound.
The FMF has a different quality to it. It is not quite as bad a$$ as the DG-R just putting around. At WOT the FMF quickly ramps up into a nasty DG-R like howl. Pin WOT and I can hear intake noise briefly before the FMF drowns it out - very different from the DG-R.
I've decided I like the FMF sound better - but not by much and not enough to spend 500+ to get the sound over the DG-R.
#27
06-08-2014, 04:43 AM
Join Date: Jan 2013
Location: Las Vegas, NV
Posts: 1,422
Well, Matt, you and I know all about the sound of the DG-R. We both like it. The Megabomb with the Power Core 4 is also very loud - too loud is a more appropriate description for both exhausts.
The DG-R , from idle to WOT is a "in your face", "bad boy" sound.
The FMF has a different quality to it. It is not quite as bad a$$ as the DG-R just putting around. At WOT the FMF quickly ramps up into a nasty DG-R like howl. Pin WOT and I can hear intake noise briefly before the FMF drowns it out - very different from the DG-R.
I've decided I like the FMF sound better - but not by much and not enough to spend 500+ to get the sound over the DG-R.
The DG-R , from idle to WOT is a "in your face", "bad boy" sound.
The FMF has a different quality to it. It is not quite as bad a$$ as the DG-R just putting around. At WOT the FMF quickly ramps up into a nasty DG-R like howl. Pin WOT and I can hear intake noise briefly before the FMF drowns it out - very different from the DG-R.
I've decided I like the FMF sound better - but not by much and not enough to spend 500+ to get the sound over the DG-R.
I never liked the two bros for example (even being loud), too high pitched and weed wacky. DG has a snarl and a bark to it
#28
06-08-2014, 04:44 AM
Join Date: Jan 2013
Location: Las Vegas, NV
Posts: 1,422
Well, Matt, you and I know all about the sound of the DG-R. We both like it. The Megabomb with the Power Core 4 is also very loud - too loud is a more appropriate description for both exhausts.
The DG-R , from idle to WOT is a "in your face", "bad boy" sound.
The FMF has a different quality to it. It is not quite as bad a$$ as the DG-R just putting around. At WOT the FMF quickly ramps up into a nasty DG-R like howl. Pin WOT and I can hear intake noise briefly before the FMF drowns it out - very different from the DG-R.
I've decided I like the FMF sound better - but not by much and not enough to spend 500+ to get the sound over the DG-R.
The DG-R , from idle to WOT is a "in your face", "bad boy" sound.
The FMF has a different quality to it. It is not quite as bad a$$ as the DG-R just putting around. At WOT the FMF quickly ramps up into a nasty DG-R like howl. Pin WOT and I can hear intake noise briefly before the FMF drowns it out - very different from the DG-R.
I've decided I like the FMF sound better - but not by much and not enough to spend 500+ to get the sound over the DG-R.
I never liked the two bros for example, too high pitched and weed wacky. DG has a snarl and a bark to it
#29
06-08-2014, 05:02 AM
Join Date: Jun 2013
Location: North Texas
Posts: 3,189
BTW, The dyno tuner and I agree that the FMF system is designed to carry more torque at the upper end of the RPM spread and the expansion chambers' part in the scheme is to mitigate (lessen) losses in TRQ from idle to mid throttle. For those that are not aware - the expansion chambers' goal is to reflect pressure waves back to the exhaust valve, having them hit the back side of the valve, usually, as the valve breaks seat. When the wave reflects off the valve back down the exhaust it creates a vacuum and that provides a scavenging effect on the cylinders' exhaust. This scavenging effect will only work over a small RPM range as the timing of all the critical events varies with RPM and the pipe can't - It has to be tuned to target the relatively small RPM range that the builder/designer deems best to enhance..
Last edited by Klxster; 06-08-2014 at 07:38 PM.
#30
06-08-2014, 12:32 PM
The expansion chamber distance to the valve is so close that I think the wave front is getting to the valve way before (as in your description) it is even to the TDC, unless your tuning to 17K+ rpm.
If we can arrive at an accurate avg exh temp in that region of the pipe, the wave travel velocity, & the duration of the valve, I think you'll see my point.