exhaust question
exhaust question
(OP)
If I have a 360 V8 with great low end torque.
then modify with throttle body/intake/headers/larger exhaust pipe..
and end up with less low end torque and more high end torque....
could I get my low end torque back simply by putting a plate in the exhaust pipe downstream of the muffler?
and do you think the low end torque would be higher than it was before the mods.
then modify with throttle body/intake/headers/larger exhaust pipe..
and end up with less low end torque and more high end torque....
could I get my low end torque back simply by putting a plate in the exhaust pipe downstream of the muffler?
and do you think the low end torque would be higher than it was before the mods.





RE: exhaust question
RE: exhaust question
RE: exhaust question
Rather..for the sake of the knowledge...I kinda tend to think of an engine as an air pump.
if I did go and figure the correct amount to restrict the exhaust pipe downstream of the muffler..do you think I would end up with more low end torque than before I added the mods?(disregarding what ever happens to the rest of the torque curve).
RE: exhaust question
Is there a "correct" amount of restriction to have in the exhaust pipe downstream of the muffler? I would have guessed that the less restriction the better...
RE: exhaust question
RE: exhaust question
If you could install a valve that would allow you to vary the restriction, you could conceivably get the best of both worlds... Almost like having variable valve timing.
Correct me if I'm wrong, anyone, but isn't the main reason that you'd see lower torque @ low rpm with the reduced restriction due to thru-flow in the cylinder? I'm guessing that some of the intake charge is heading out the exhaust valve, thus reducing vol. eff.?
RE: exhaust question
RE: exhaust question
Rod
RE: exhaust question
DW
RE: exhaust question
It seems more likely that the flow is going the other way, some exhaust heading up the intake, but with the same net result (reduced vol eff).
That doesn't help explain how a valve in the exhaust could improve low-end torque (and such devices ARE used successfully in motorcycle applications)..
RE: exhaust question
With larger headers, the exhaust flow at low rpm is at a lower velocity so it can change direction easier. This leads to the situation Ivymike mentioned, with the exhaust backfilling the cylinder, and even mixing into the intake charge.
RE: exhaust question
http://www.automotiveforums.com/vbulletin/t13199.html
"We see these in the Mercedes McLaren F1 car. If you think this is somebody's Frankenstein pipe dream then guess again. The new Suzuki GSXR1000, Honda Fireblade, and Yamaha R1 already have these."
http://biketransplant.tripod.com/exup_replacement.htm
"The Yamaha R1 is fitted with an EXUP valve. This is a Yamaha specific invention designed to improve torque at low to medium revs. It works by placing a small "flap" in the exhaust collector. This flap can be rotated to reduce/increase flow through the collector. When reduced the back pressure is increased and the wavefront at lower speeds can be reversed to improve extraction. "
http://www.power-sports.org/new/bikes/gsxr1000.html
"as well as Suzuki's Exhaust Tuning system that optimises back pressure in the pipes for optimum power throughout the rev range. "
http://www.suzukisa.co.za/ModelDisplay.asp?ID=90
"The new GSX R1000 features the new digitally controlled Suzuki Exhaust Tuning (SET) system. The new exhaust control system uses a butterfly valve to modify back pressure and thus tulle the pipe to suit running conditions. The butterfly valve is opened and closed by a servo motor, via cables, depending upon engine rpm and transmission gear selection.
At low rpm, die valve closes, increasing hack pressure and improving low-end torque while also reducing exhaust noise. As engine speed increases, the valve progressively opens to reduce back pressure and improve mid-range and high-rpm output. The four-into-two-into-one exhaust system itself uses a combination of titanium, stainless steel and aluminium parts to reduce weight. The header pipes, collector and internal muffler core pipes and core-pipe mounting plates are made of titanium"
(good typos in that one, eh?)
I think that these bikes are all 4-strokes, but I have to admit that I'm not entirely certain about that, as I don't really know much about motorcycles...
RE: exhaust question
http://www.motorcyclenews.com/news/detail?sectionID=50678&documentID=22528&pageNum=1