Exuast piping & mufflers

[3sgte@daspeedof]

Ok, so I'm doing a 3sgte swap into my celica.
I plan on going 3" all the way back. Now I've seen 2 different types of mufflers.
2 1/2"Inlet W/4" tip
3" Inlet W/3 1/2" tip

Just wondering which would be a better set up. I've heard a little bit of back pressure is good, Thats why many people go with 2 1/2 exaust pipes.

[MartinGouda]

in a boosted car there is no proof that backpressure helps anything...

and on your motor you need to look at a downpipe (TB Developments 3S-GTE DownPipe would be my choice) that will acomedate a 3" setup or the rest of the exhaust is useless...ask drew' he's rocking 3' from the turbo to the bumper. less lag, faster spool and more power all along.



in my eyes you are getting ahead of your self again tyrone...

Step one... get motor in car
Step two... think about after market exhaust

[3sgte@daspeedof]

no, because the exaust needs to be accounted for, or I won't have a streetlegal car. I have to have an exaust. Better to do it right the first time then have to go back and do it again.

Where can I get this TB Developments 3sgte downpipe

[3sgte@daspeedof]

no, because the exaust needs to be accounted for, or I won't have a streetlegal car. I have to have an exaust. Better to do it right the first time then have to go back and do it again.

Where can I get this TB Developments 3sgte downpipe.

Are you still painting my car? Would like to pick up paint this weekend sometime

[spoolin_gt]

if youre going for full 3"...then go for full 3" from the turbo to bumper...it's better to have 2.5" downpipe and 3" exhaust than having a 3" down pipe, exhaust and choking it with a smaller muffler...its never good to bottle neck any cars..

[MartinGouda]

Originally Posted by 3sgte@daspeedof

no, because the exaust needs to be accounted for, or I won't have a streetlegal car. I have to have an exaust. Better to do it right the first time then have to go back and do it again.

Where can I get this TB Developments 3sgte downpipe.

Are you still painting my car? Would like to pick up paint this weekend sometime

I'll be ready to paint but you arn't ready for paint and you shouldn't buy it untill you are ready to spray it, once you have the motor out and all the body work is done then holla back man... but last time i checked she wasn't ready for the gun yet....

i agree with gian but the cost of a full 3' will be alot while still trying to build a working car and swap in a 1st gen 3sgte with newer 5sfe parts... at first i would say just get her running... then tune after.. it will allow for more of a war chest to be saved for the issues that will come up i mean the down pipe alone will be like 450 cdn and that's assuming you want to run 3's from the turbo.... i know it might seem silly to have the stock downpipe mated to the stock gts exhaust but truth is that before you make power by upgrading you should consider making a running car...

cars happen in stages... no one really jumps to stage 3 with out stage 1 unless it's in a video game or they have too much money to spend.. you fit into neither catagory..

[3sgte@daspeedof]

See your wrong on all accounts.
A turbo car needs a little back pressure to spool up, with a full 3" your gonna get more top end power, with a 2 1/2" your gonna get more low end.

Boost kick in around 3200 rpm, and cut at about 5500 thats for a 2 1/2"pipe straight back

Boost will kick in at 4000 with a straight 3" and last longer, but you lose on the lower end cuse it will take more time to spool up.

Car will be ready to start paint this week, cherry picker is at my place engine will be out sat morning. Doors are primed, will have the front bumper on sat. Need to get fenders but that won't stop us from painting the rest of the car. Trunk trim is already un bolted. just needs to come out.

[3sgte@daspeedof]

The motor will go in after the paint is done, so I wanna get started this week, I should have it all primed by next week friday. engine goes in the following week, I will be a 2nd gen engine now though, thinking about going with an wta set up too.

[MartinGouda]

Originally Posted by 3sgte@daspeedof

See your wrong on all accounts.
A turbo car needs a little back pressure to spool up, with a full 3" your gonna get more top end power, with a 2 1/2" your gonna get more low end.

Boost kick in around 3200 rpm, and cut at about 5500 thats for a 2 1/2"pipe straight back

Boost will kick in at 4000 with a straight 3" and last longer, but you lose on the lower end cuse it will take more time to spool up.

Car will be ready to start paint this week, cherry picker is at my place engine will be out sat morning. *Doors are primed, will have the front bumper on sat. *Need to get fenders but that won't stop us from painting the rest of the car. Trunk trim is already un bolted. just needs to come out.

i hear what you are saying but i dont see proof... scc has run tests on boosted civics, 300zx's rx7 and many other cars on dynos with and with out backpressure and they have also done this with NA cars... in all of the test the more open the exhaust the more power...

in no situation that i can think of has backpressure helped make power.. maybe smooth lines but not make power..

[MartinGouda]

Originally Posted by 3sgte@daspeedof

The motor will go in after the paint is done, so I wanna get started this week, I should have it all primed by next week friday. engine goes in the following week, I will be a 2nd gen engine now though, thinking about going with an wta set up too.

then buy the paint monday...spray monday tuesday and let dry till thurs

[MartinGouda]

Destroying a myth.
Some say that "an engine needs backpressure to work correctly." Is this true?

No. It would be more correct to say, "a perfectly stock engine that cannot adjust its fuel delivery needs backpressure to work correctly." This idea is a myth. As with all myths, however, there is a hint of fact with this one. Particularly, some people equate backpressure with torque, and others fear that too little backpressure will lead to valve burning.

The first reason why people say "backpressure is good" is because they believe that increased backpressure by itself will increase torque, particularly with a stock exhaust manifold. Granted, some stock manifolds act somewhat like performance headers at low RPM, but these manifolds will exhibit poor performance at higher RPM. This, however does not automatically lead to the conclusion that backpressure produces more torque. The increase in torque is not due to backpressure, but to the effects of changes in fuel/air mixture, which will be described in more detail below.

The other reason why people say "backpressure is good" is because they hear that cars (or motorcycles) that have had performance exhaust work done to them would then go on to burn exhaust valves. Now, it is true that such valve burning has occurred as a result of the exhaust mods, but it isn't due merely to a lack of backpressure.

The internal combustion engine is a complex, dynamic collection of different systems working together to convert the stored power in gasoline into mechanical energy to push a car down the road. Anytime one of these systems are modified, that mod will also indirectly affect the other systems, as well.

Now, valve burning occurs as a result of a very lean-burning engine. In order to achieve a theoretical optimal combustion, an engine needs 14.7 parts of oxygen by mass to 1 part of gasoline (again, by mass). This is referred to as a stochiometric (chemically correct) mixture, and is commonly referred to as a 14.7:1 mix. If an engine burns with less oxygen present (13:1, 12:1, etc...), it is said to run rich. Conversely, if the engine runs with more oxygen present (16:1, 17:1, etc...), it is said to run lean. Today's engines are designed to run at 14.7:1 for normally cruising, with rich mixtures on acceleration or warm-up, and lean mixtures while decelerating.

Getting back to the discussion, the reason that exhaust valves burn is because the engine is burning lean. Normal engines will tolerate lean burning for a little bit, but not for sustained periods of time. The reason why the engine is burning lean to begin with is that the reduction in backpressure is causing more air to be drawn into the combustion chamber than before. Earlier cars (and motorcycles) with carburetion often could not adjust because of the way that backpressure caused air to flow backwards through the carburetor after the air already got loaded down with fuel, and caused the air to receive a second load of fuel. While a bad design, it was nonetheless used in a lot of vehicles. Once these vehicles received performance mods that reduced backpressure, they no longer had that double-loading effect, and then tended to burn valves because of the resulting over-lean condition. This, incidentally, also provides a basis for the "torque increase" seen if backpressure is maintained. As the fuel/air mixture becomes leaner, the resultant combustion will produce progressively less and less of the force needed to produce torque.
taken from:
http://www.uucmotorwerks.com/html_pr...torquemyth.htm



Can You Tell Me About Exhaust Systems?
Exhaust Theory

Exhaust gases leave the engine under extremely high pressure. If we allowed exhaust gasses escape to the atmosphere directly from the exhaust port, you can well imagine how loud and cop-attracting the noise would be. For the same reason gunshots are loud, engine exhaust is loud. Sure, it might be cool to drive around on the street with that testosterone producing, chest-thumping, 150 decibel roar coming from your car… for about 5.3 seconds. (Not 5.2 or 5.4 seconds… 5.3.) Even the gentleman's gentleman has gotta use a muffler, or system of mufflers, on their exhaust.

Again, you may hear a few SPMT's tell you that "Borla mufflers make horsepower!" Or "An engine needs some backpressure to run properly!" Nonsense. A muffler can no more "make" horsepower than Wile E. Coyote can catch roadrunners. Any technician with any dyno experience will tell you that the best mufflers are no mufflers at all!

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


other resources, OverBoost.com howstuffworks.com and others are avalible too... read up before you tell me i am wrong on all counts

[spoolin_gt]

wrong...
the bigger the piping is for a turbo car...the faster the turbo will spool up...my turbo starts spoolin at about 2200rpm and will be at full boost before 3krpm with my 3"exhaust set up and will boost up to 6500rpm.....my 2.25 exhaust before was spoolin up to 6500rpm and starts at around 3krpm...it really depends on your turbo..not your exhaust.......turbo will spool up to a certain rpm depending on exhaust size....

Originally Posted by 3sgte@daspeedof

See your wrong on all accounts.
A turbo car needs a little back pressure to spool up, with a full 3" your gonna get more top end power, with a 2 1/2" your gonna get more low end.

Boost kick in around 3200 rpm, and cut at about 5500 thats for a 2 1/2"pipe straight back

[3sgte@daspeedof]

[quote=from [url]www.mr2oc.com][/url]
Originally Posted by dsf3g
A quick question to those in the know (Ricky B? ATS?).

What are the negative effects of running, say 15 psi of boost on the stock ECU? I understand that the USDM 2nd Gen 3SGTE ECU has no fuel maps beyond 12psi, and that the ECU just dumps a lot of fuel into the engine at that point to avoid lean running and detonation.


Not correct. If you look at any 3sgte dyno chart with an A/F trace, it is obvious that the ECU makes a smooth, curvilinear transition from stoich at normal cruise conditions, to about 10.5-11:1 as boost climbs to 15 or more, and RPM increases. There is no sudden transition at 12 psi (or any other point) where the ECU "dumps fuel".

And the OEM fuel system, as well as the ECU programming, is fully capable of delivering an adequate, albeit somewhat rich, fuel supply for a CT26 equipped 3sgte.

BTW, I ran 15 psi on an otherwise stock '91T for about 6 years troublefree. Many others have safely run 15 psi with no other mods for long periods of time.

bill

http://www.mr2oc.com/showthread.php?...t=running+Rich


".....The stock ECU runs the engine excessively rich..... "
^^Taken from celicatech.com
http://www.celicatech.com/forums/sho...jump+fuel+pump

Stock 3sgte engines run rich to begin with. You can ask anyone who has a swaped 3sgte, and is running the 3sgte fuel pump.
If this wasn't an issue then people wouldn't start with 2 1/2" and then decide to go 3" straight back.


Taken from Nissan Performance Mag.com

You need to have the lowest backpressure possible to produce the maximum power by keeping pumping losses low. Too big of an exhaust pipe causes power loss, especially low-end torque. This is because a big pipe has less exhaust stream velocity than a smaller pipe. Velocity is essential to get the best scavenging (or sucking) effect from tuned headers, which we will discuss in more detail later in a future installment. To simplify things, if the exhaust gas flow is kept high with good velocity, a vacuum can develop behind the closed exhaust valve allowing even better scavenging when the exhaust valve opens on the next exhaust cycle. Good scavenging is even more critical on valve overlap, the part of the 4-stroke cycle where both the intake and exhaust valves are open, especially with longer duration performance camshafts.

If the exhaust pipe is too large, the flow will be sluggish with low velocity and the scavenging will not be good. Remember that a good exhaust has low backpressure and high velocity. The only possible exceptions to this rule are for turbocharged or nitrous motors. It is almost impossible to put too big of an exhaust past a turbocharger as a turbo depends a lot on the pressure differential across its turbine to get power recovery efficiency. A turbo engine can have an exhaust gas volume about 1.5-2 times more than an equivalent displacement naturally aspirated motor. NOS motors also have a pretty high exhaust volume and require a bigger exhaust if they are to be optimized for NOS operation.

The stock exhaust system on most modern rice rockets is often so well designed nowadays that just switching to a high performance cat back exhaust often does not allow for huge gains of power. With the exception of turbo cars, you can usually expect only about a 2-10 hp at the wheels difference on a stock car. The power gain will usually be the greatest from just below the torque peak to the tach’s redline. On cars that are modified with headers, intakes, cams, headwork, etc., you can expect bigger gains with the addition of a cat back exhaust due to the higher flow volume that these mods produce.

As turbo cars are very sensitive to back pressure, you can expect much larger gains with them, especially if the boost is turned up. A free flowing exhaust usually allows the turbo to spool faster also. A turbo car usually gains from 8-30 hp at the wheels depending on how bad the factory exhaust was and how high the boost is turned up over stock.

Taken from NissanPerformanceMag.com
http://www.nissanperformancemag.com/...fthenerds2.php

Now tell me why someone with a 3sgte is not running a 4" or a 3 1/2" exaust, can you tell me why you wouldn't wanna run something that big on a stock setup?