niguels

Hoping to shed some light on the BACKPRESSURE topic, please follow the attached link. It is about an analytical study on the backpressure effects on the engine output, including dyno charts of the car with stock exhaust and with straight through piping, plus conclussions. It also shows THE DATA THAT Magnaflow WILL NEVER SHOW.

http://www.is300.net/forums/showthread.php?t=209937

The Truth sets us free

hahaitzskippy

VERY GOOD STUFF

but, wat is a Y pipe???

unlmtdndeavor

nice find and good info.

since the car is a V6, there are 2 exhaust manifolds, the Y pipe is where they connect and become one. then it goes all the way back to the single exhaust on the is300.

oldman

The IS is a straight 6 and like the Supra and the BMW there are two exhaust manifolds, one for 3 holes. hence a Y pipe to put it to one.

http://www.canadiandriver.com/testdrives/01is300.htm

The only addition I'd make is the second setup is really a test of the a set of headers and axleback, IMO the typical "straight through" mufflers used on import axle back systems really have a lot of backpressure, IMO running a good muffler like a dynomax turbo would allow the car to be bone stock quite and drop the backpressure from the muffler to .5 PSI or less. All IMO of course. So really the header and axle back added a MAX of 6 ft-lbs in a small range. For maybe a couple of grand, and louder too, something I would never put on a IS. To bad all the import racers believe straight through fart mufflers are the performance setup while in truth the turbo muffler flows better, has a more consistant backpressure profile (the straight through ones have NO backpressure at low flow and MORE backpressure then a turbo muffler at highflow) yes a lose lose scenerio. Once again my thoughts and I've installed and buit many many many exhaust systems.


I go back to OEM, there are NO OEM performance cars taht I know of with "straight through" mufflers. NONE because these mufflers are a lose /lose scenerio for some reason propergated within the import market. My last turbo GS-R had a turbo muffler and it could do 350 WHP, pump fuel and be even quiter then a stock GS-R.

http://www.toyomoto.com/is300.htm

My final in a nutshell thought is the blahhh, blahhh, blaaahhh sound you hear from the average import performance "straight through" muffler is the sound of lose power in all ranges.


My sister has an IS BTW.

acasanova

guys i found another article:

http://www.nsxprime.com/FAQ/Miscella...austtheory.htm


Really like hearing from you oldman so please comment on this one.
:D

niguels

The article you mentioned does not show any dyno graphs comparing the torque and HP curves in a stock engine vs. an unrestricted exhaust engine.

If we don't show real comparisson data, then all we are saying is "word of mouth" and the thread will continue endless forever.

The link at the beggining of this thread shows a "REAL LIFE COMPARISSON" with dyno graphs so that everybody can understand how the system engine+exhaust behaves under normal and low backpressure conditions.

To everybody in this thread... Please show real comparative data, better if from an independent source, in order demonstrate what is the truth about low restriction exhaust systems.

oldman

Problem with "real" comparison data is that it is at WOT, but most people drive 99.9% of the time part throttle.

The mere fact that there are no vendor dyno shows that the exhaust part show no to minimal gains. Since many of us know this, many of us are not shelling out $$$ and then doing a dyno to show that yes indeed we got minimal HP for the money

Case in point your post on $2000 worth of exhaust, no real gains, hence the Toyomotor has no dyno of their exhaust on site. Why? Cause nobody is shelling out $2000 for 6 ft-lbs in the midrange. DC says "dyno proven" I have NEVER seen a DC dyno. So where is the "proven" part of their catch phrase.

I found a link for a GS-R dyno with

http://www.importtuner.com/tech/0407it_ppintegra/

Yep we all know the B18C is one of the MORE responsive engines to NA changes so read'um. Total bolt on like 10 HP.

Mistertwo

My friend's 2001 Hyundai Tiburon had a straight through muffler stock. Almost found that a little odd.

What is it about a typical straight through muffler that creates more back pressure than a muffler like the Dynomax Turbo? Just wondering. Something I've always noticed about them is that the centers are the mufflers are noticeably smaller than the inlet and outlet piping. A friend of mine had a generic muffler on his Supra that had a 3" inlet and outlet but when you looked inside the muffler, it tapered down to at most 2.5". The HKS Hiper exhaust I have on my MR2 is the same way unfortunately.

oldman

Even the classic turbo muffler off a 1962 Turbo Corvaier is “straight through” meaning if you held it up to the light you could see the outlet on the other side. This is not really a “straight through” design as the original and all follow on mufflers have reducer cones like you described and / or large baffles on the internal tube.

The dynomax superturbo muffler is really a reverse flow design BTW.


The “straight through” mufflers used by import performance exhaust builders as high performance mufflers feature smooth internal pipe with an assortment of funky design holes in them. Basically the design does not and can’t work. If you try to make a “straight through” performance muffler with smooth “baffles” aka a funky assortment of holes, for the internal tube you can’t make it quite and the muffler will feature NO restriction off idle meaning no back pressure meaning a loss of drivable torque. It will also be very LOUD. So then you gotta toss in real baffles and or crimp the case and or put neck downs to quite it down so restriction goes up then you just end up with an old fashion glass pack.

So “straight through” does not mean line of sight, it means smooth internal pipe AND you can see line of sight through it (in general) I can say the Edelborck “straight through” design has two divergent path ways and that re-combine and you can’t see through it. Dynomax or other turbo mufflers with reverse flow and / or baffles in the pipe and or baffles in the muffler itself with PACKING are the only mufflers that work as mufflers. I’m sure the OEM Tiburon has a baffled, internal packing design mufflers on its secondary (the two rear mufflers) Also I would speculate that the secondary muffler is more of a fancy resonator / tip and the large and long central muffler on a Tiburon is doing all the work..

I just went to tech for the autoX, there were many cars. A Civic B16 SI with Greddy exhaust was there, huge stainless steel muffler and resonator both really fancy glass packs, super loud and raspy, no real power gain per the owner. Need I say more?

I’ll sum this up a dynomax reverse flow turbo muffler can flow 410 CFM with .5 backpressure and be near stock quite. Every “straight through” muffler is going to be loud and the quiter it gets the more backpressure it will have at high flow, If you tried to make a straight through muffler as quite as a dynomax you would end up with a heavily baffled super small inlet cone old fashion highly restrictive glass pack.

As I’ve stated many times no OEM performance car has one of these “straight through” design mufflers. I don’t know if a Tiburon falls into this category and I’m not sure about the overall design of the Tiburon exhaust.

The link above shows the DC complete cat back added an average of 2HP over the super quite stock Acura exhaust system and that is after all the bolt ons. And the comment was that is was “The system is rather loud”. Yep and for 2 HP!!!!! I’d just run synthetic oil for the 2 HP and leave my system quite as a mouse.

At the Autox tech a Z06 was there and so was a C6, a few other exotics amazing how quite these cars are at idle and nice power loud at WOT, all of course with OEM baffled designed mufflers. Non as loud and obnoxious as the Greddy Civic.

For me, I’ve been around exhaust too long to spend such cash on a 2.4 liter with a HUGE exhaust system from the factory. IMO I’ll save it for a turbo, supercharger or autoX.

I checked out a new Type-S and it had a HUGE 2.5 inch fatory exhaust to get 10 more HP from last year Honda did:

Engine modifications that boost the horsepower of the Type-S model to 210 at 7800 rpm
High performance camshafts
Larger intake duct
Large diameter exhaust pipe
High-flow catalytic converter
redline raised from 7900 to 8200

Like I said the down pipe was HUGE and mandrel bent. look at what needs to be done for 10 HP: cams, intake, exhaust, converter, ECU tweeks. Not just toss on a fart can with large tip. The Scion's engine went from 137? HP to 160, so you know Totota did some major design changes. I don't think Toyota just left a spare 10 HP on the design table cause the suck as engineers.

chris0

are we comparing a 6 cylinder to a 4 cylinder? I'll admit what I know about cars could fit into a shotglass, but aren't we comparing apples and oranges here?

chris

niguels

Both are in-line engines, 4 valves per cylinder, VVT-i.

Sure there a differences in torque and HP, but the essence of the experiment (effects of unrestricted exhaust on hp and torque) and the engine behavior, should reproduce, at a lower scale (due to engine displacement), the results obtained for the Lexus IS300, IMO.

I agree with you in case we were trying to compare a regular gasoline engine with pistons with a Wankel Type Engine ("Mazda RX-8"). The operation principles of those engines are completely different.

oldman

Stock GS-R has 150+ WHP to th wheels about 10 more then a tC. The last loud raspy Greddy exhaust added 2 hp for $800.00 or so. Same gain could be found by running Amsoil 2000, redline or royal purple engine oi for 20 bucks as the tC takes only 4 quarts. I owned two GS-Rs and the exhaust is SMALLER then a tC. So if a higher HP enigne with WAY higher RPM with a full load of bolt ons gets 2 HP from the exhaust, how much are you going to get from a brand new design eninge that turns at less RPM, has a bigger exhaust by far and put out less HP? Answer no a whole lot. IMO sub 10 for sure, maybe sub 5. Proof? Alpha works is the only vendor with data on their stuff and full bolt ons they have 23 WHP, we will know in the next few months as customers get to the dyno. I hope that it s ture but have serious doubts.

wc01

more plz