Back Pressure

[bra0063]

Hi guys I'm just wondering if I would be loosing back pressure and low down torque I have a stock exhaust system but the rear muffler has been changed for a cannon muffler also that exhaust curve before the stock muffler had to be replaced will this affect my back pressure? I still have stock centre muffler but I do also have a high flow cat the car feels a little slower at lower rpm but it could be just me being paranoid as my old exhaust " cat back performance" system made the car a lot slower

Cheers

[zebra]

back pressure is bad mmmkay

[mad082]

changing the rear muffler won't do much for performance in either a positive or negative way. it will make the car louder though.

also you need to know that, despite what a lot of people will tell you, you don't want back pressure from an exhaust system, whether it's turbo or natro. back pressure is an unwanted side effect from having an exhaust that flows well at lower rpm. the majority of people will just refer to back pressure when talking exhaust size without knowing what they are really talking about. what you want is an exhaust with optimum flow and minimal back pressure, however this is much easier said than done.

[bra0063]

Just feels a little slugger in low rpm it really pisses me off how sensitive shitty NA skylines are to "back pressure"

[zebra]

It isnt "back pressure" it is gas velocity and cylinder scavenging

[bra0063]

Yeah I know it's gas velocity but most people understand is at back pressure lol just is annoying that when I replace any part of the exhaust to more free flowing the car becomes in fact slower

[Berk]

More timing?

[Hanaldo]

More timing?

There are very few people out there who waste money on purchasing and getting an aftermarket ECU tuned for a naturally aspirated Skyline.

[Super Drager]

Yeah love how everyone talks about "back pressure" like its the end of the world on an NA car.

[xALmoN]

laminar flow is good..

turbulent flow, not so good.

you dont want eddies in your flow.

[zebra]

What if it is Eddie Vedder singing Even flow?

[xALmoN]

hmm.. opens up a whole new can of worms doesn't it.

[mad082]

There are very few people out there who waste money on purchasing and getting an aftermarket ECU tuned for a naturally aspirated Skyline.

you can add timing without an aftermarket ecu.

[zebra]

wind the cas around a bit lol

[T04GTR]

not a skyline, renault clio, sock exhaust . 2" press bent with lots of mufflers. went to a 2.5" no cat and 2 straight thu mufflers gained 10% @ wheels.

[mad082]

not a skyline, renault clio, sock exhaust . 2" press bent with lots of mufflers. went to a 2.5" no cat and 2 straight thu mufflers gained 10% @ wheels.

not discounting your gains, but what you said is somewhat of a blanket statement and doesn't show the true nature of the power gains. unless you overlay the before and after power runs and compare the power gains throughout the rev range you can't accurately see what gains you made. the majority of people just look at the peak power output. this can mean that while you may have a car that at the top of the rev range makes more power, but in the low and middle of the rev range (where you spend most of the time when driving on the street) you may be down on power. not saying this is the case for all cars, it's just a generalisation. i've seen plenty of cars with exhaust systems that give gains at the top 1/3 to 1/4 of the rev range, but lose power at the lower end of the rev range. the funny thing is though, because of the slightly steeper power curve, it gives the sense of total power gains. i've also seen exhaust systems that gave no total power output, but lower power in the lower rev range that also gave this feeling of more power.

[sikmatesubwoofa]

<br />not discounting your gains, but what you said is somewhat of a blanket statement and doesn't show the true nature of the power gains. unless you overlay the before and after power runs and compare the power gains throughout the rev range you can't accurately see what gains you made. the majority of people just look at the peak power output. this can mean that while you may have a car that at the top of the rev range makes more power, but in the low and middle of the rev range (where you spend most of the time when driving on the street) you may be down on power. not saying this is the case for all cars, it's just a generalisation. i've seen plenty of cars with exhaust systems that give gains at the top 1/3 to 1/4 of the rev range, but lose power at the lower end of the rev range. the funny thing is though, because of the slightly steeper power curve, it gives the sense of total power gains. i've also seen exhaust systems that gave no total power output, but lower power in the lower rev range that also gave this feeling of more power.<br />

<br /><br /><br />

Well I think it's better to lose some down low for overall top end. Honestly I think you NA guys should build the engine up WITHOUT a turbo and run a stealthy NOS setup. It doesn't matter if you're a P Plater you can set it up in a stealthy way. This would cost some money though not only the building but I'm not sure if the stock ECU can run different tunes for NOS and non-nitrous but if you have the cash and want alot of power on your Ps then it's the way to go.

[mad082]

<br /><br /><br />

Well I think it's better to lose some down low for overall top end. Honestly I think you NA guys should build the engine up WITHOUT a turbo and run a stealthy NOS setup. It doesn't matter if you're a P Plater you can set it up in a stealthy way. This would cost some money though not only the building but I'm not sure if the stock ECU can run different tunes for NOS and non-nitrous but if you have the cash and want alot of power on your Ps then it's the way to go.

for a race car yes, for a car driven on the street, then hell no. if you are making less power below 5000rpm then stock, then you will spend pretty much all your time driving a car with less power than you started with, unless you plan on only driving round in 1st and 2nd gear, and maybe 3rd on the highway. less power at lower rpm results in higher fuel usage as well as a car that isn't as nice to drive on a daily basis. in a lot of cases the difference in drivability and fuel economy is minimal.

[Gerg_R31]

f**king school holidays aye

i agree with mad082 what's the point in having all that power if it can't be used, n/a or not any motor needs to be built around its main purpose and be practical

Plus im a strong believer of response/ torque is what you should focus on and the power output is just a bi-product.

With the nos idea, to "just whack a nos kit on" is going to kill any motor that is not prepared for it, some stock valves will burn out that never would in normal conditions. cast pistons will crack or melt, forged pistons will eventually melt, "tuff" coated forget pistons will stay coated from 6-20 shots (varying depending on how much is used) leaving a bare forged piston, and im sure there is more in areas i don't specialise in

(wow we did go off topic a bit didn't we)

[MBS206]

I'll take the car that makes all of its grunt down in the low to mid range rather then up top...

That way you just short shift, and stay on power.

If it's dead down low on power, it's going to be slow off the mark unless you have a shit load of grip and launch it all the time...