exhaust & air filters

[cargle]

For people who ahve upgraded their exhaust, have you noticed much difference to your fuel economy, the reason I ask is that I actually do alot of travelling and may have to take this into account because I'm thinking about upgrading my exhaust soon, although it probably wont change my decision.

I've been told that if you go for a exhaust larger than 2" it actually hinders performance, is this true?

The same with Air Filters has anyone upgrade their air filter, I was thinking about it but my mate upgraded the air filter on his wrx and found it made little/no difference to performance but a large difference to his fuel efficiency (made it worse)

[Rex]

ive noticed better fuel economy with the exhaust *IF* you dont thrash it. If you like to belt around flat-strap all day long you will definitely get worse fuel economy. Generally a 2" mandrel bent or a 2.25" press bent exhaust is the way to go, anything bigger than that will give you shocking bottom end and sound like someone farting in a milo can (unless of course youve got the mods to run a bigger exhaust like that)

[Fahootie]

Originally posted by Rex
anything bigger than that will give you shocking bottom end and sound like someone farting in a milo can

ROFL...excellent.

I've never heard that sound, so how am I expected to know what that sounds like?

[dan]

Originally posted by Rex
anything bigger than that will give you shocking bottom

got any data to back this up rex? as far as i'm aware, bigger is always better with exhausts.. and i cant see a reason why not... and if you want to use backpressure as a reason, please explain *why* engines need backpressure? :)

as for fuel economy, i too noticed an increase in fuel economy on the highway and when driven softly around town.. however when i'm strapping it it drops down more than it did before. i cant say for sure with recent figures however, as my odometer has seized.

just on fuel economy, i get 60-80km more out of a tank of optimax/ultimate.

doing the math on this..

* assume the full 50L in a tank is used.

* the use of theoretical prices does not matter, only the price difference matters

* the price differences between ulp and 98ron pulp is 6c/l in queensland at all times.

* assume 500km from ulp, 550km from 98ron pulp

* ulp = 70c/l.. 50 x .7 = $35 for a tank
$35 tank = 500km = 14.28km per dollar

* 98ron pulp = 76c/l = $38 for a tank
$38 tank = 550km = 14.47km per dollar = 1.32% further

* therefore 98ron pulp is 1.32% more economical to run than ulp, with the increased performance as a side effect.

so there ya have it, run 98ron :)

[REDSSS]

you definitely CAN get TOO BIG for normally aspirated engines

the only sort of engines where bigger is better is forced induction (turbo/superch) because the backpressure decreasing turbo performance outweighs everything else

the exhaust is tuned for a certain ideal rev range. i cannot explain it myself as i only half understand the theories behind it and i dont want to get it confused. Maybe someone else can help here

but i can guarantee that bigger is not necessarily better with N/A. there are lots of articles on the net about this but you are better to ask someone more technically minded

[REDSSS]

btw they also talked about this a bit in march hot4s

[dan]

I did a quick google search for exhaust size and didnt find all that much.. all I found was this on autospeed

its in the members only section, so i'll quote the relevant part


originally written by Julian Edgar, AutoSpeed
Back-Pressure
In all but one test I have ever performed, the bigger the pipe, the better the power. That exception was on a Celica 2.2 FWD, where I'm willing to bet that if the management system had been slightly retuned (eg low rpm ignition timing advanced) the power at low revs would have picked up over standard as well (it was already improved over standard at high revs). Thus, after the tuned length section of the pipe is finished (ie after the first muffler/resonator/cat converter), in a naturally aspirated engine you should go for a large pipe. In turbo cars, go for a large pipe straight off the turbo. Incidentally, note that over the last 40 years, the pipe size regarded by some as "too big" has been getting larger and larger every year! The following table, extracted from the book 21st Century Performance*, is my recommendation for pipe size:

Maximum Power (kW) : Pipe Diameter (inches)
75 : 2
120 : 2.5
165 : 3
230 : 3.5
375: 4


i'm not saying you're wrong, so dont take this the wrong way - i'm just interested in some data to back up your claims.

[bio]

well tihnk of it this way...how is a bigger end pipe going to increase performance? If you have a 2inch manifold, cat etc, a 3inch endpipe will do exactly what?

[dan]

decrease restriction, increase airflow

[bio]

but the restriction is already there form the manifold and cat. to use a computer analogy (perhaps incorrect) its like sending something from a 56k modem to someone with a 2meg line.

perhaps the increased size reduces back pressure? not sure really, all i know it the countless NA cars with >2inch end pipes (and stock cat/extractors) dont seem very responsive low down, and make a hell of a noise. *shrug* :P

[cargle]

I am going to take my car to some exhasut specialists over the the next week or so to get some quotes on upgrading my exhaust.

I'll make sure I ask them all the questions we have been trying to work out.

I always use ultimate, nothing else although the prices over here in the west are reaching over a $1/ltre the past few days, it'd be nice that the new exhaust doesn't make much difference to the fuel economy, but I guess that the nice rorty exhasut note will outweigh any negatives.

[REDSSS]

removed this post as it was explained better in a lower post of mine

[REDSSS]

removed this post as it was explained better in a lower post of mine

[REDSSS]

removed this post as it was explained better in a lower post of mine

[REDSSS]

ok here is a reaaaaally good article

this article is supposed to be on a paid site but this guy cut and pasted it on his site

http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

it clearly explains everything that i was (badly) trying to explain

the MAIN problem with too large exhaust->

scavenging
========
like i said pressure and velocity have a lot to do with it. when an exhaust is about to pump gasses from a cylinder there is a LOW pressure at the tail end which sucks the new pulse of exhaust out much more efficiently... with a larger exhaust the difference in pressure is negligable at low speeds... the loss in scavenging can outweigh the lesser backpressure... thus less power in low revs

there are other problems with too large exhausts discussed in there but basically they are a compromise between top and bottom end power

for the ultimate exhaust... yes dan u do want to have as little as possible backpressure but in doing so you dont want to run into other losses by having a too large exhaust... so u r better minimising your backpressure by other means: mandrel bends, better muffler, top qual extractors, thermal insulation etc

as that guy mentioned... cat back doesnt really matter AS much... the scavenging is already done so the only thing u have to weigh up here is the losses gained in air density/temp vs a slight gain in backpressure

in terms of the muffler.. all things considered i would say the larger the better for that as the gasses are practically out of your system and the muffler is one of the primary causes of backpressure

l8er
Dennis
______________
resident expert in exhaust systems

[cargle]

you have made some interested points,

you have given me alot of ammunition, theories, questions for when I go and have look at getting my exhaust done.

[Fracka]

Originally posted by cargle
I am going to take my car to some exhasut specialists over the the next week or so to get some quotes on upgrading my exhaust.

I'll make sure I ask them all the questions we have been trying to work out.



Hey dude

When you find out some prices and what is recommended let me know what you find. I will do the same.
They say two heads is better than one. :)

I am just about to upgrade my exhaust and intake as well.
I have a Nissan Pulsar Q Hatch 2002 Model (Who knows whether it is the n14 or n15??).

I am also looking at getting a power chip for my beast as well. :D

I will let you know how I go if you are interested.

[bio]

fracka the N14 was made between 1991 and 1995, the N15 between 1995-2000 i think. Your model is the new N16 sadly sans the SR20DE.

[Fracka]

Originally posted by bio
Your model is the new N16 sadly sans the SR20DE.


What do you mean sadly sans? I don't know much about the diff between the pulsars as of yet

[bio]

sadly the N16's dont come with the 2 litre engines of past pulsars, making them rorty little sex beasts that everyone here knows and loves :P

[Fracka]

Yeah i would have gotten the SSS had it come in the current shape but they were still flogging the older shapes and I liked the new Hatch shape better

But just after I bought my car I heard that they were thinking of bringing it out. Just a rumour though. Probably a load of shite.

[bio]

n14 all the way mate!

[dan]

hmm, to add fuel to the fire..

chiptorque specify a 2.5" press bend or 2.25" mandrel bent exhaust system for all their power chips.. and chip torque seem to be pretty good, in my opinion at least..

you can check at www.chiptorque.com.au in the 'performance chips' section.

anyone want to lend me $1,395 for a few years? hehe :)

- dan

[Fracka]

Hmmm.....

6kw gain with there chips?
That has to be a misprint!!

Power Chips Australia (http://www.powerchip.com.au) shows the the 2.0L going from 105kw to a healthy 121kw.

Not bad if you ask me and for $935AUD. Even better priced.
Is there something better with the chiptorque ones that I do not know about?

I am knew so I know shite at the moment

[Spectrix]

Hmmm 121 Kw and 205Nm sounds awsome.:devil:
Thats a pretty good increase for under $1000, especialy with no other mods eg headers, exhaust, lumpy cams etc.

Makes me wonder what they've done to the air/fuel mapping in order to achieve these figures though. The stock Sr20DE runs rich for a reason, reliability. I doubt you'd get figures like that without making dramatic changes to the air/fuel ratios.

I sent an online request for info to powerchip but there was no option to ask for a dyno sheet or ask anything other than their own multiple choice questions. I'd be interested in seeing a dyno sheet to make sure the power and torque curves werent too peaky.

Oh.. the other thing is that these figures are specifically for the Sr20DE found in the SSS/Q .. so sorry Fracka it's not gonna work on your car, and so far they havent developed a chip for the Qg18DE. :bawlink:

[Fracka]

Oh.. the other thing is that these figures are specifically for the Sr20DE found in the SSS/Q .. so sorry Fracka it's not gonna work on your car, and so far they havent developed a chip for the Qg18DE. :bawlink:

Yeah I know......what a bummer!!!

My car is very new so eventually a chip will come out for it I suppose. So until then :bawlink:

[dan]

i'm not so confident with the results that powerchip presents.

first of all, they quote these figures at the flywheel. they have never done engine-dyno testing so it is not possible for them to back these numbers up with a dyno map. sooo.. i'm not sure where the numbers came from... certainly not a dyno.

chiptorque instead quotes power atw.. so i feel a bit more confident with their numbers.

if you're wondering why i'm not too happy about powerchip, read these:

http://www.autospeed.com/A_0402/page1.html (part one)
http://www.autospeed.com/A_0408/page1.html (part two)

[Spectrix]

Common thing to do with Sr20s is to bump up the ignition timing a few degrees and run them on 98ron Premium Fuel like BP Ultimate or Optimax... but I have a feeling the Qg18DE might have variable valve timing?? Not sure if you can advance the ignition on them...

In regards to exhausts, Neill (SilverSSS) has the nicest sounding exhaust I've heard on a pulsar... Sublte but deep. Its just a 2.5 inch Cat back press bent system, cost him around $250 I think. :thumbsup:

And I know some people are gonna argue with me here but if you go for a full system that's any larger than 2.5 pressed or 2.25 mandrel, you might gain a little top end but you'll lose torque low down. You can go huge with a turbo because the back pressure from the turbines make up for any losses caused by the larger diameter pipe.
You can also use a huge exhaust on a riced up excel because the stickers, skirts, spoiler and bonnet scoop add more than enough horsepower to make up for the loss of engine performance.:thwap:

[REDSSS]

http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

[Fracka]

Good Article :thumbsup:

[twincam16]

People often think that the bigger the better. with turbos Yes for sure.

with a Supercharger... to a degree. but not the same extent as a turbo.

with N/a its a little harder.

Sorry i have missed all the begging of this but how anyone can claim to go from 70odd kws to just under 400 kws is beyond me. if this was true then every single Excell would have 6" systems and be able to chop a Skyline GTR. its not that simple

you need back presure for the valves to run correctly. indeed increasing your pipe dia. will make you motor rev more freely (which most people believe is making more power) but you will be loosing an absoloute fu<kload of tourque

at the end of the day you have to remeber that its a 2L N/As. keeping in mind that even mild worked 5L commodores mostly run a 3" system and a 3.8L V6 makes it most power with a 2.5

as a general rule of thumb anything below a 1.8 stick with a 2" system if you have a 1.8 that does not rev high also stick to this size. if you have for example a CA18DE or a SR20DE go for the 2.25 but for heavens sake the only think your doing by sticking a 2.5 or larger on is making more noise and attracting the cops.

Which we dont need :)

Cheers
Shane.

[Spectrix]

Everyone seems to have different ideas about whether or not an oversized exhaust is detrimental to the performance of a small naturally aspirated engine.

I went searching for info on exhaust size and found various contradicting articles, most of which summed up either:

a) 'backpressure is not needed & the bigger the better', or

b)'going to big will cause a loss of backpressure and therefore torque'

Obviously someone's wrong here. :confused:

I've always believed in b), but I'd really like to see some dyno runs to prove it.

.

[Spectrix]

Which reminds me, Powerchip got back to me about 'dyno results' for the Sr20DE running with a powerchip module.

Please see attachment...

Looks great on paper.. not sure where they pulled this info from if they don't own and have never used an engine dyno. It looks like an Ms Paint jobbie.

I'd be asking to see a valid Dyno Dynamics chassis dynamometer result showing power at the wheels rather than a bit of mythical drawn up smeg before spending a grand on one of their chips. :mad:

[REDSSS]

Originally posted by Spectrix
I've always believed in b), but I'd really like to see some dyno runs to prove it.

ive been saying for ages we need to get everyone with dyno sheets to put them on the pulsar.org.au website with a summary of their mods

that will give us all a good estimation of what mods are worthwhile and what are not

[twincam16]

Agreed. apart from Rigoli at the coast where in brissie has a Dyno Dynamic Dyno? and what do they charge for a simple power run now?

[Rex]

my mate got his ET turbo done on one in brisbane (brisbane turbo or something like that, i will try to find out)

offtopic, he pulled a very usable 150fwhp in his ET... not bad for a lightly modified 1.5t!

[twincam16]

I would be interested to see what Nancys does now compared to factory specs.... what are they at the wheels in KW in stock form?

[Spectrix]

Um.. stock Sr20DE makes somewhere along the lines of 80kw at the wheels.. every motor is different of course, but this is a ballpark figure.

Carb'n'ject at Underwood have a full 4wd Dyno. They also do Unichip installation which requires real time tuning exactly matched to a particular engine. This is one of the few distrubutors of APS (Air Power Systems) WRX and 200sx Kits and they come highly recommended.

http://www.4wddyno.com/index.html

[twincam16]

Obviously i wont tell till i stick it on the dyno but i think i may have got what i aimed for. the original aim was to get the factory flywheell output at the wheels without touching the internals (ie forged pistons bla bla bla and stock ecu) i think i would be bloddy close to the 100kw at the wheels not sure / doubt if i would make 100 tho... have to wait and see

we should make a day out of it, get everyone out there have have a sort of mini shoot out. would work out cheaper for the lot of us then :devil: What ya thinks

[Spectrix]

YEps.. I've just emailed carb'n'ject saying we might have a dyno day and asked for prices'
aslo asked about best exhaust size for an Sr20DE hehe'

[twincam16]

got a fealing this is going to be a on going debate :thwap:

[Rex]

check this thread for dyno info:

http://forum.pulsar.org.au/showthread.php?s=&threadid=125

[dan]

just got a new pipe on my 2L q, and here are my thoughts on the three different sizes i've had on it. for reference, my car is perfectly stock (except for, obviously, the zauhst) running the standard airbox with a new-ish ryco paper filter.

1 7/8" pipe w/12" resonator (standard) : lots of backpressure = lots of bottom end torque. almost no exhaust noise at all. top end is a bit lacking due to backpressure.

2 1/4" pipe w/no resonator and large 2.25" muffler (press bent mild steel) : good increase across the rev range. bottom end noticeably gruntier, top end also pulls better. was very loud and made a spitting sound.

2 1/4" pipe w/18" hotdog resonator and large 2.25" muffler (press bent mild steel) : similar increases as with previous 2 1/4" pipe, just a tiny bit smaller, bad sound gone. my recommendation for an un-modified car with only mild mods planned for the future.

2 1/2" pipe w/15" hotdog resonator and 2.5" strait-thru muffler (press bent mild steel) : my current system, about the same noise level as the previous system, although louder when higher up in the rev range and under load (so in 2nd/3rd/4th gear). noticeable drop in bottom-end torque, however very noticeable gain in top-end power. can now wheelspin into 3rd without being
brutal on the clutch. is really an exhaust system in waiting for cam/head work. with the 2.5" i beleive there is more power, certainly the car is faster in a straight line. however around town it is a bit less driveable without the bottom end torque.


if you're wondering why i've had so many systems, the 2 1/4" systems suffered from poor workmanship.. hence where replaced to go for the 2 1/2" system. the poor workmanship was more in the design of the pipe (hung down too low), so i figure i can still legitimately comment on the performance of the pipe size. i went for a 2.5" system because all the chiptorque chips are tuned for that pipe size, and it's on my list-of-things-to-do. the 2.5"system was done by performance pipes at acacia ridge (qld), and i am _very_ pleased with the standard of workmanship. highly recommended for any zauhst work.

[twincam16]

Hrmmm only ever had 2 systems on Nancys

Standard - Granny Material
Current - Wildcat Custom Extractors, Tuned length, port matched, press bent 2.25" Stainless Pipe. 2.25" Cat. Hand made Stainless 2.25" Muffler (non chambered). oh yeah and a 4" dump tip but that dont mean sh!t :)

And quite simply. yes its loud, personaly i think it sounds awesome, altho Niell and a few others thinks it sounds like and Excel.... :Flipa: But hey it goes well

[REDSSS]

Originally posted by Spectrix
YEps.. I've just emailed carb'n'ject saying we might have a dyno day and asked for prices'
aslo asked about best exhaust size for an Sr20DE hehe'


the last sydney dyno day was $40 each

[dan]

shane, three words for you..

get a resonator!

[Rex]

I agree, a resonator will get rid of that raspy overrun noise, you will lose minimal flow by adding a resonator and it only costs about $80 installed. Make sure you get it welded as U-joints are not acceptable on cars like this, they will shake themselves loose in no time.

[SILVRSSS]

It does sound like an excel :Flipa:

Get a friggin resonator :devil:

Hold on its not even your car :evilgrin:

Oh and the polishing is complete and I have reinstalled the rocker cover bolt and now I have a spare one he he

Cheers
Neill

[twincam16]

I never said it was my car.... Whats your point....

oh wait... thats right my girlfirends car is quicker than yours... sorry couldnt forget that now could i :Flipa:

[SILVRSSS]

Yet to be proven

And besides I don't rape cars to get the best out of them...

Just wait until after July my friend :devil:

And besides where is your car I'll give that a chop with the Nikes.... he he

[twincam16]

if you really want to know Niell my car is i getting fixed due to an acco i had last week that was not my fault and landed me with a stuffed up back and no car....

Besides. its a ford laser. i aint / never will say its anything more. besides the fact it is a pice of sh!t no argument there

Rapeing cars.........?????? What do you mean by that?

[Rex]

rape = torture the shit out of them
im a big believer in this practice (expecially the super-robust sr20) :D

[twincam16]

Ahhh now i see...

Nancys may get a hard life but atleast its well looked after :)

Speaking of which... just got off the phone to nissan. 104 bucks for a new clutch cable :barf:

[CharcoalSSS]

Just got my stock exhaust put back on for insurance reasons. I preveiously had a gunie 2 1/4" system frome the cat back. The SSS is a new car I can take off slowly with out boging down, exit corners in second and have instant pick up. Obviously this backpresure thing is very true and having the smaller exhaust makes a hell of a difrence. Up top its prety much the same. My mates vectra 105kw stock used to beat the sss through 3/4 of 1st gear even though I would beat him off the line. Then at the end of first we would be even and by 3rd id have two car lengths on him. Now ive got him from the word go.

Hope this helps with any exhaust issues.

I personaly am going to get a 1 3/4" or 2" hiflow system when I sort my insurance out. Surly there has to be better exhausts than the stock one however the bloke at the exhaust place did close by saying "manafactures are not stupid" food for thought hey.

cya,

Adam

[AussieN14]

You have insurance problems with an exhaust?

man, i told NRMA (usually the pickiest pricks you can find) that my car had headers and an exhaust and they said "thank-you" and made no change to my policy, to them, headers and exhaust make no difference.

[Spectrix]

Theres a lot more to an exhaust than just pipe diameter. A properly tuned 2.25 inch system should make a little more power over the entier rev range than the stock 1.75 system. I'm sure Shane and Nance will atest to that.

I've heard some horror stories about aftermarket exhausts though.. people paying for larger systems only to find that they've lost power due to oversized pipes or shockingly bad welding and pipe intersection setup.

Check out http://www.autospeed.com/A_0486/page1.html for a bad exhaust job.
(This is a members article so you'll only be able to view the 1st page but there's a fair bit of info there.... and if you're interested in tech stuff it's worth the membership cost too.... they have stacks of good articles.)

[twincam16]

agreed.

you have to remeber that when the facotrys make a system that have to keep things in mind like cost cutting and sound.

one thing facotry mufflers do not do is flow well. they do a super job of keeping it quiet tho :)

i am still standing by my word that a 2.25 is the absoloute largest i would go under any condition. have a look at mike glews sss n15, now he has aftermarket cams, headwork, extractors and hi is "only" running a 2" system. altho it is a high quality system with quality mufflers. and trust me having been in his car when he was nailing it i can vouch for how well this thing moves. it kicked the pants of Nancys. and it didnt feal "restricted" in the top end like all the 2.5" system owners say it does.

just my 2 cents

[Spectrix]

I found out some interesting things about exhausts..

Apparently exhausts CAN be too big, but the problem doesn't lie in the lack of back pressure, infact as little backpressure as possible is the way to go.
The problem with oversized exhausts - and the reason they can rob a small N/a of torque - is to do with harmonics, ie the pulsing waves that happen each time a cylender fires. An oversized, or more to the point badly tuned oversized exhaust buggers up the harmonics that the engine and chip were originaly tuned for in the first place. New engine managment with real time tuning can overcome this (to an extent) but ultimately the car manufacturers usually do a pretty good job in the first place so it's best to have a properly tuned (and this usually means not too big) exhaust fitted. ;)

[REDSSS]

fark didnt ne1 read my link dammit

http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

i talked about it in this thread but obviously noone was listening

there are more factors than harmonics but yes that is an important point and the main theory behind extractors

[Spectrix]

Eeeh.. no one reads those links! Heheh


And yeah I've read that article, it's a good'n

You can't beleive everything you read though:D

[badger]

bringing up an old thread but:

IMHO, the reason that you lose bottom end torque by going bigger is that you need to retune the engine to take advantage of the higher flow.

if you retune the engine then you will have more power from bigger exhaust (all other things being equal).

of course there will be a size where you don't get any more gain, or you don't get enough gain to justify the bigger expense...

[Pulse]

I put a 2 1/4 madrel system with high flow cat, remus muffler and K&N on mine about 4 years ago. I had plans back then to get a chip and cams later on but that never happened. Without the chip and cams I think 2 1/4 madrel is too big, I lost a fair bit of bottom end, but then again top end is great.

[cargle]

im getting my exhaust done this week, or next, just a cat-back system

I have been to 3 of the popular exhaust specialists in perth and each have recommended a 2", they say 2.25 is too large unless I am going to do other mods such as chips and cams etc..