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i want the power back in my neon...any ideas on wat i can do to regain back pressure? i got a flowmaster racing series on it now...gutted cat...also has a pacesetter header....open as open can be....and dont say put a stock muffler on lol i cant go back man...i just cant... i wont go back

its not so much back pressure as it is velocity.

the less back pressure the better so long as the velocity of the exhaust gases are good. you probably only lost power on the bottom end which i believe is common when you free up an exhaust or go with a bigger exhaust.

at low rpms the velocity isnt that great so you loose power, but at higher rpms the velocity is good so you gained a little power.

why not just replace you hollow cat with a hi flow.....

well i have been tryin to figure out y i have no power compared to a stock one....best time s 10.8 in the 1/8 mile i see stockers doin 10.3........y is this lol... i got cai,pacesetter header, sts, solid motor mounts, gutted cat. with a flowmaster on there, and a #10 crane cam....also lowered an has 17's with kumho ecsta's weighing in at 34 lbs per wheel and tire.....wheres my loss???

i cant remember where are you located?

your 17" wheels are slowing you down. maybe you just dont have the launch down.

setup a garage here on the site. it will make it easier for people to tell what kind of car you have so they can make correct recomendations.

there are other factors too. maybe the track is uphill slightly. a track is allowed a 1% grade, whether it be up or down. if it isnt a NHRA or IHRA track then it may be greater.

there are a lot of factors that by themselves dont affect you much but added all together they can really make a big impact.

im in san diego. i have a garage set up i just dont know hw to make the link show up right there<<...my 17's are pretty light and are close to the stock size u think they are still just to big over all?....never thought of that.

not only does weight affect acceleration, but the increased inertia of the 17s that affects acceleration.

after trying diff setups with cai and straight through glasspack, no muffler, to cai and r/t muffler, to stock airbox res removed and r/t muffler. all those setups left me with low end bog, and loss...

being i have the 3spd auto, what works best for me im sorry to say is the plain old way it came, with stock muffler, and stock airbox WITH the resonator in the fender...... MUCH more get up and go for around town driving which is what i need..... IMO of course....... granted i dont race, but i do have a lead foot, and im sure my 17's and subwoofer arent helping any either. but thems the breaks.........

"backpressure" is simply the difference between the gases exiting a system and the gases outside a system. backpressure is never good as it decreases efficiency. ways to increase backpressure are to decrease the exit area of your muffler (switching from a dual outlet to a single outlet or decreasing the size of the tip), which increases the exhaust gas velocity, which decrease the gases pressure. this creates a larger difference between the exiting gases and the atmospheric gases which creates a greater backpressure. properly managing the gas flow within the exhaust system is not related to "backpressure" and is the reason for your decreased low-end performance. by making your exhaust system freeeeerrrr flowing you end up flowing the exhaust gases at velocities below/above peak efficiencies for lower rpm's which reduces your power output at lower rpm's.

like racer said, its not back pressure but velocity.

if you go back to your stock manifold and cat you with increase/decrease your exhaust velocity bringing it back to a more efficient velocity (read as "mass flow rate") for lower rpm's. if you want more back pressure go back to your stock muffler.

you should be running better times (or at least better et's) than a stocker. your larger wheels (increased mass moment of inertia like racer said) are most likely the culprit for slowing you down... because F=M*A (F=rotational force, M=mass moment of inertia, A=angular acceleration)

underway wrote:im in san diego. i have a garage set up i just dont know hw to make the link show up right there<<...my 17's are pretty light and are close to the stock size u think they are still just to big over all?....never thought of that.

If you air down 17s, you have about the same contact patch. If you air down 14s, your contact patch is huge in comparison. Try putting your stock tires on, and let the air in the front be 15psi, and pump up the rears to as much as the manufacturer says is OK.

have you tried light weight pullies i have light weight pullies on mine and they sure helped allot

esteinmaier wrote:If you air down 17s, you have about the same contact patch. If you air down 14s, your contact patch is huge in comparison. Try putting your stock tires on, and let the air in the front be 15psi, and pump up the rears to as much as the manufacturer says is OK.

dont u men that 14's air down is bout the same size as 17's? cus my 17's are wider and a bigger around wich would make more tire touch ground...maybe im wrong....also i dont have stockers or we wouldnt be havin this conversation...atleast not about wheels... i would have tested this theory long ago. and i tried runnin my tires all the way down to 15psi with no affect ..spin city ...maybe it makes too much torque and the tires arent enough rubber...yeaaa..thats it lol.... ..also i have not tried light weight pullies b/c i have run with no belts wat so ever on and started it and the car didnt rev any better....(no alt. ran off battery) and i have taken off just the ps/ac belt and tested it and felt no difference in power so i didnt see how an underdrive pulley could top no belts at all... and finally i also tried disconnecting both exhaust 02's and i might b crazy but it feels lil stronger under full throttle.... i kicked the focus that runs 10.4's in the 1/8 mile even worse last n ight on the street... just sucks that i cant see an actual time to prove my cars power....i think also that the fact that i have to burn out on the track cus u gotta roll thru water and then my tires get hot and they dont like heat..... kinda screws me a bit

They are wider, sure. But they have less sidewall. Think of a water balloon vs. a basketball. Same size, but you push down on the balloon, and more touches the surface it's on, as it's more pliable.

oh now i see what you mean, but do you think that enough sidewall will actually touch to make it that big, and is the sidewall rubber good for traction?...none the less i dont have the stockers and dont wanna pay 200 bucks to get a set with tires on them just to find out its not gonna help... im suppose to race a honda hatch tonight on the street with the si motor ....the b16 or b18 or wat ever it is... he ran a 10.2 in the 1/8 so if im close behind him ill know im fast...just not at the strip...