Clark Kent

by changing to an SLP it does remove all friction/ back pressure for the engine. it may lower it slightly, but not by much. If back pressure were that big deal there would be alot less mustang owners with SLP. our kind isnt too keen on losing power. if we were we would all be driving 4 bangers

jedikd

obviously you haven't seen the thread about 22" Wheels

kevinb120

I have this VR6 Golf on the lot some kid put straight pipe side pipes on it, that thing does 0-60 in what must be 14+sec now and is louder then a dump truck engine braking, although the dump truck sounds better

bob

I'm still not seeing it, back pressure is litterally negative torque, if you cannot evacuate the cylinder and there is residual pressure in the cylinder, then the engine has to expend power to move the piston up on the exahust stroke and it turn this saps some power that could be transmitted through to the crank. On the other hand, a high flow exhaust system can be detrimental in a few ways; a. the system can over-scavenge the cylinder and draw some of the air/fuel charge into the exhuast reducing the volume of combustible material in the cylinder (if anybody wants to check this out, go DL Engine Analyzer Pro 3.5 and do a few cycle calculations after modeling an engine - pretty interesting), or b. the system can simply be too large for the engine and you end up with a lazy exhuast tract that relies solely on the engine to pump the spent exhaust out (not really trying to fight negative torque, but the engine doesn't get the assit provided by a well sized and efficient exhaust system and like fighting back pressure has to expend horspopwer to do the job that otherwise would be transmitted to the crank).

Clark Kent

bottom line willl I have a signifigant decrease in power in my vehicle by going SLP. Is it somehting that I would notice?

Mas35NYR

NO! Case closed!

Error404

myth of ram-air? how is that a myth?

bob

It has to do with the way air behaves at sub sonic speeds, super sonic aircraft (or well anything that can crack the sound barrier) can take advantage of an actual ram-air effect. At sub sonic speeds you cant ram air, the density remains the same, the only thing that effects the density of the air is temperature and humidity so with a "ram-air" vehicle your really taking advantage of cooler (denser) air, other than that, if the "ram-air" system can pass a greater volume of air (less restriction) than the original intake path, then you get power that way also (provided the original intake path poses some sort of restriction in the first place).

Ultimately "ram-air" is really just a very sexy cold-air set-up.

Bullitt995

I've seen a camaro create 3 psi in the intake manifold with no forced induction. Same principle. What's your backround bob? Engineer?

blkstang06

Bob, Well said and absolute fact!

nynvolt

Whatching some automotive program, they had one of the guys who designed the "ram air" concept on the 60's camero's he said it was worth 3hp max but it sure sold cars. Was actually an option on some. Yes it does look cool though.

I'll admit I'm ignorant as to what exactly back pressure has to do with torque, however I know that adding an intake and free flow exhaust can reduce it and on small displacement engines kills your low end (under 3000 rpm) torque. I also know that back pressure is important for keeping cylenders at optimum operating temperature. The purpose of the charge motion plates, atleast in Honda/Acura products, was to help with low end torque, they worked very similar to our 3v charge motion plates. They restrict the intake air under a predetermined rpm.

As I said before though, I really doubt removing the exhaust cans and adding straight pipes, as are slp lm's, is going to cause any real apriciable back pressure loss. You get plenty of back pressure from your cats and the exhaust manifold.

davids2toys

Just disconnect the battery and follow the directions in the owners manual to the letter...drive it spirited for 7 to 10 miles, and your problem will be solved!
Or, just drive it for a few hundred mile justr the way it is now , and it will self correct.