Supra Forums banner
1 - 20 of 26 Posts

· Registered
Joined
·
126 Posts
Discussion Starter · #1 ·
I wonder if anyone have an answer to this question. I would like to compare stock exhaust vs two chambered exhaust. We all know straight through is much better. For example, the APEXI world sports vs stock exhaust.

Is the World sports a lot better than the OEM exhaust?

This application is for the turbo motor. I know APEXI does not sell the Worlds sports for the supra turbo. But for the heck of this learning research, would the APEXI WS be much better than the stock? Please elaborate your opinions. Thank you.
 

· Banned
Joined
·
191 Posts
The question of stock being restrictive boils down to a bunch of factors. Some will argue that the stock exhaust was built to maximize performance for the stock setup. However, there is also the fact that there are noise and emission regulations that require certain exhausts.

For example, I was speaking with the head of GM performance vehicles and when I took the new ZR-1 out for a ride, he mentioned when I got on it how loud it got. I noticed the change in exhaust note and just assumed it was because I was standing on it. However, he said that what happens is when you are really on it, the exhaust has some cutouts of sorts that then open up to maximize the flow. When asked why he said it was 2 fold. 1. for a $100k car some people like to have a nice quiet ride when driving around town. 2. The regulations on noise and emissions require them to make such measures.

Additionally, anyone who has driven an older camaro z28, ss or corvette will remember the times when they had that stupid 1 to 4 skip shift that required you to go from 1st to 4th. This was supposedly for economy but in actuality was for noise restrictions on the exhaust.

In all, the debate will loom forever :)
 

· Registered
Joined
·
126 Posts
Discussion Starter · #3 ·
Great info Jeff. Thanks

I know there are some cars out there, that if you change the OEM exhaust for an
after market, you would loose some horsepower and sometimes the gain is very minimal.

Im thinking that the difference between the OEM and aftermarket is the amount of sound damping materials they put inside. If you notice most OEM exhaust are huge, while after market is much smaller? OEM must be quiet, so they have to stuff more sound damping material...right? Hmmmm....

Are we just buying the exhaust tone or are we buying actual performance? Hmmmm
 

· Registered
Joined
·
13,982 Posts
The biggest "power loss" in the stock exhaust system are the cats. People here, including me, have run with a full 3" downpipe, no cats, feeding the stock catback and you can feel that is a large power increase; maybe somebody even has dyno numbers on that but I don't. But there is still some power left on the table by using the stock catback ...my wild ass guess estimate is 25whp from the stock catback being replaced with a free flowing aftermarket catback when still running the stock turbos. The larger the turbo/s the more the stock catback is a restriction.
 

· Registered
Joined
·
126 Posts
Discussion Starter · #5 ·
Nick

What do you think of this exhaust setup for stock twins?

I know at the turbo exit where the O2 sensor sits is about 2.25" ID. I was thinking of getting a 2.5" downpipe and run it to a Y spliter. This Y splitter has a 2.75" ID. This is then Y off to two OEM exhaust. Since there are two OEM exhaust, I figure the flow should be better than compare to a single OEM muffler.

To clear things up. This is for a GS300 with a 2jzgte vvti swap. Say I were to replace the OEM exhaust with an after market AXLE back exhaust. How much would you will ass guess the power difference? :)

Supra is single exhaust. GS300 is dual. It might have a better benefit. What do you think?

Im in the process of deciding whether to get an after market exhaust or not. If the after market is only difference of few horses, then its not worth it. Im trying make my car a sleeper and only reason for that are the COPS.
 

· Registered
Joined
·
13,982 Posts
I'm not sure and don't recall the 2.25" turbo exit. But the 2.5" downpipe is a choke point compared to the usual 3" (or larger) downpipes used on Supras:

2.5" dia = 4.91 sq. in. flow area
3" dia = 7.07 sq. in flow area

Your overall concept sounds valid but I'd go with a 3" downpipe to your Y splitter.
 

· Glad to be back
Joined
·
3,478 Posts
I just put a Apexi GT spec on my about two weeks ago. Before exhaust I had an intake, dp and NO cats. After the installation i still had a notice gain in power. Top end especially.
 

· Registered
Joined
·
126 Posts
Discussion Starter · #8 ·
The measurements are valid. I took my tape measurement and measured it accordingly. Its 2.25 ID, mid pipe, then 2.75" ID to Y pipe.

If I were to get a 3" downpipe and then goes to a 2.75" Y pipe...wouldnt that interfere with my air flow velocity? If I remember correctly you want exhaust to start small then go larger and larger to the exit point. Basically to keep its momentum moving faster. Maybe the different is so small that it does not matter? Since the 3" pipe would probably have an about 2.75" ID anyways?
 

· iSketch Master!
Joined
·
12,496 Posts
On a turbo car you do want velocity out of the turbine, but I don't think trying to forever expand the diameter of your exhaust would make a significant difference. the pipes are usually measured by their inside diameter so the 3" is 3" ID.

I say don't bother with that Y setup. Run a 3" DP back to the stock exhaust. The factory crush bent exhaust will never be better than a single mandrel bent exhaust for flow. Especially considering there are about 100 bends in the factory exhausts!!!

Instead of spending money on all these Y's and stuff, just get a cutout like SP's. It opens under boost and you can keep your noise down, and you keep factory exhaust on. I suppose you would still need a Y to connect the end, but it doesn't have to be large or anything.

Alex
 

· EchoDeDupra
Joined
·
7,159 Posts
The stock is exhaust is really restrictive. I swapped out my 3" mandrel bent for stock for some reason back in the day, and it was incredible how much slower the car felt.
 

· Boost Junkie
Joined
·
15,154 Posts
WTF? Hasn't this been covered a million times? Typically a BPU car picks up 25-30whp at stock boost levels with an exhaust system. Start upping the boost and the increase is even more. It is a no brainer.

Steve
 

· Registered
Joined
·
126 Posts
Discussion Starter · #12 ·
Yes this is obvious. I was trying to ask if I were to use the stock exhaust compare with an after market exhaust, but both exhausts are chambered. I was trying to see if the after market flows a lot better than the OEM or are they almost identical. Chambered vs chambered.

Yes its obvious if you get a straight through exhaust and up the boost you will get a bunch of HP gained.
 

· Registered
Joined
·
126 Posts
Discussion Starter · #13 ·
I wish I was in other states where smog is not an issue. COPS in CA is very strict. About 8 years ago, I had an Acura Integra and my after market exhaust was so mellow and I got pulled over for having a modified exhaust. He popped my hood and I had to get a state smog. That was rediculous, since I was driving like 15 mph making a u turn into a parking lot and he pulled me over. My exhaust was slightly louder than stock.

This is why Im trying to find ways to get the best performance using stock exhaust if possible.

I wouldnt be asking this question if I was in other states. I would get me a 3" downpipe, and a nice straight through exhaust.
 

· EchoDeDupra
Joined
·
7,159 Posts
This is why Im trying to find ways to get the best performance using stock exhaust if possible.

I wouldnt be asking this question if I was in other states. I would get me a 3" downpipe, and a nice straight through exhaust.

Install a 3" downpipe, and put a 3" electronic cutout after it, then connect your stock exhaust to that.

It will be like running open downpipe when it's open, but when it's not, it will be stock :)
 

· Super Moderator
Joined
·
14,009 Posts
I wish I was in other states where smog is not an issue. COPS in CA is very strict. About 8 years ago, I had an Acura Integra and my after market exhaust was so mellow and I got pulled over for having a modified exhaust. He popped my hood and I had to get a state smog. That was rediculous, since I was driving like 15 mph making a u turn into a parking lot and he pulled me over. My exhaust was slightly louder than stock.

This is why Im trying to find ways to get the best performance using stock exhaust if possible.

I wouldnt be asking this question if I was in other states. I would get me a 3" downpipe, and a nice straight through exhaust.
Integra777, yes, any aftermarket exhaust will make a very significant improvement.
If you're looking for a cali-friendly catback for the MK4 Supra Turbo I highly recommend the Tanabe Medallion Touring.
Very close to OE look but dispenses with a lot of the weight of the stock system, and for an 80mm system it is extremely quiet between its main muffler and inline resonator. I have one with myself and it is top-notch.

Tanabe used to have a video of it where you could hear the exhaust note, I'm not sure if that's still floating around somewhere or not.. here's some pics from their website.

Here's some pictures:



 

· iSketch Master!
Joined
·
12,496 Posts
I think one of the best street exhausts would be the GReddy Power Extreme. It's kind of heavy in the muffler though. It is very quiet, and throaty as well. It has a main muffler and two pre-mufflers. I cut the main muffler off and replaced it with a straight pipe, and I still don't think it's as loud as the HKS Ti.

Alex
 

· ...smell like cabbage
Joined
·
4,106 Posts
100% bone stock I trapped 104.

Same temps, same track, same tires...

RRM DP with HKS Carbon Ti. NO boost controller, only a cut controller because sometimes I would hit a cut. Stock sidemount, stock intake, everything else stock went 112. I would say 8mph from only exhaust is quite the improvement.
 
1 - 20 of 26 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top