Does Size Matter? 2.5" vs. 3" Exhaust discussions. [merged]

[Boostin18]

2.5" vs. 3" exhaust discussions are merged here.

I have a 90 GSX and when i bought it the guy said it was full 3" turbo back with a EVO3 O2 housing (ported), now here is my question. When I took the exhaust down, it had a 2.5" exhaust flange at the top of the down pipe and then flares for about a half inch out to 3", if that makes any sense. This is my first 3" exhaust and I was wondering if this is right? I was thinking of porting the o2 housing because it is 2.5", making it 3". Then bringing the exhaust to a shop and having them weld a 3" flange to about a half inch long peice of 3" ehxaust pipe and then welding it on to the whole exhaust. So basically getting rid of the 2.5" flange and the half inch long flare and just welding on the 3" flange with the new piece. Would this make a diffrence if i do this or not. I don't know if this would make any diffrence or not, but when i put a boost controller on, i would try and get it to set at 15psi, but never would it would just spike and go down to like 12 or 13, but never above 15, but never at 15. I also have a ported 2G manifold (havent had it off to make sure it really is ported). Any help would be great!

 

[livedsm4g63]

Okay now we are at the heart of the problem we see you as a leader but you don't consider yourself a leader! So you definitely have a modest side to yourself and that's good! Whether you want to accept it or not you are a leader here on tuners because people listen to you whether wrong or right its up to you to use that influence for the benefit of the forum or not! All I am saying when you disagree with someone don't try and make them feel less than human with big words and math but instead pm Them and reason with them your point then come back to the open forum you and them a united front. If you do this these forums will be awesome because I think you can be a powerful leader on tuners if you get you act together. I know we disagree most of the times but a can't imagine the boards without a land speed dsm there to give the scientific explanation of the matter! With the benefits of the forum in mind that is!

Dr. Oz couldn't say it better himself.
Land Speed for President.

 

[mercaholik]

Got my vote, I love science it's the balls.

 

[94awdcoupe]

worth a read as it seems pretty relevant to this thread.
warning: goes against president land speed theories.

http://www.performancecar.co.nz/articles/guide-to-performance-exhaust-systems-138

 

[athlete3344]

This entire thread has basically been "theory" (basic laws of thermodynamics which industrial plants use for design) vs opinion (i heard this mechanic say this, this guy wrote this article and says this). A little experience has come into play, mainly in the forms of "feelings", which can often be misleading.

However, two or three real life examples have been provided. The first was cut out vs no cut out, the 2nd was the article with dyno results as data, and the last was kel's dyno results for cut out vs no cut out. In all cases, the larger and shorter pipe makes more torque for our cars.

Show me dyno results for 2.5" vs 3" on a 16g where it makes more low end torque on the 2.5", and maybe we will have a discussion. Quoting random articles containing absolutely no data is the same thing as having a friend of a friend beating 500hp cars with 300hp cars.

 

[94awdcoupe]

my "opinion" comes from testing. I used "theory" to build a" 3" exhaust to improve performance over the"2.5" I was running. the 2.5 exhaust produced far more low end tq below 4000 rpm.

ask the WRC guys why they run 2.5 to 2.75 inch size exhausts and get back to us with the dyno results.

my opinion is the only people that should be posting in here are the people who have tested back to back and learned. common theories will mislead you.

 

[athlete3344]

Would you be able to provide some of your data so we can compare against the other 3 sets of data posted? It would be interesting to see the higher torque numbers you are producing and by how much of an increase it is.

So far the other 3 sets show the opposite, so this is actually very interesting.

 

[livedsm4g63]

5 inches.... AArrroounnnddd.

I wanna see some data 94awdcoupe.
Dyno pulls will work just fine.

 

[94awdcoupe]

man I wish I had back to back data for that car but dont. I did find old data from when i developed my yellow car. there are twelve columns of changes. the car drove to the track 120 miles round trip on twelve occasions. car made successful passes each trip and drove home all twelve times. . the numbers in first column is the power the car made on its first trip to the track. first pass was 11.48 second pass was 11.49. the last column the car mustered 10.25 93/meth, street radials tires , no stutter launch, or any other changes to make it "trackable".

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interesting reviewing notes. change form .63 to .82 exhaust housing lost 60hp at 4000. lost 20hp at 6500 rpm. no gains anywhere. internet theory said I would pick up 40-50 hp.
1g extrude hone swap to cyclone gained 45hp at 4000 rpm. 2-8hp losses through the midrange. remains on car to column 13. numbers are from gtech on same stretch of road. equal whp from low reading mustang.

 

[livedsm4g63]

Back to back is the only way to truly tell. AKA Buschurs thread.

 

[LandSpeed-DSM]

For starters, there's no mention of exhaust size in your "data."

All of which is taken from 4,000rpm up. Swapping cams and turbine housings is not the same as a downpipe.

None of which is back to back.

Basically all you've demonstrated is that you couldn't even squeeze 500whp from a 35r and you have no idea how to use the scientific method in practice.

No "internet theory" here. Just an industry-backed and text-book published understanding of turbomachinery.

There is general consensus between industries, from aviation and power generation to automotive and marine manufacturers, all saying the same thing.. yet some random dude (who can't even understand what he posted himself) claims they are all wrong because he and some "shops" say so.

You have zero data. What you BELIEVE or FEEL is not equally valid nor some alternative perspective to established laws constituting a Theory.

 

[94awdcoupe]

where did I say there was an exhaust test in this data? the first sentence states I have no data on that from that car. and the numbers were stated as low reading mustang. first column was 410 dynojet, last column was good for 599 dynojet .

again, I see reading comprehension of a ten year old here. and absolutely pointless to attempt any civil intelligent conversation.

 

[athlete3344]

again, I see reading comprehension of a ten year old here. and absolutely pointless to attempt any civil intelligent conversation.

Agreed.

 

[94awdcoupe]

Back to back is the only way to truly tell. AKA Buschurs thread.

yeah. and hers a direct quote from dave from 2009. these number were on his low reading mustang dyno. 700 is well over 800whp dynojet.

Flash forward to about 2 years ago. I had the lighest 3.5" tubing with minimal bends in it bent up for a 3.5" turbo back system to market. I built one for my car, the Bad Bish, put it all together using V-band connections and a Burns super lightweight racing muffler. Loaded the car on the dyno and dyno'd the car back to back VS our 3" turbo back with our bullet muffler. The car was over 600 whp on our Mustang Dyno at the time. The results? 3" had more low/mid and the same or better top end. I could not believe it. I had all those exhausts left at our shop until about 6 months ago when I traded them to another shop looking to build some. I built one for Al's GT42r car, one for Matt's GT42r car and sold the one I built for my car.

To add even more to this. I think it was this spring when I decided that my 700 whp car was just too loud and I was sick of listening to it. The car had run (most of you know this already) 9.0 at 159.6 mph through our standard 3" turbo back with the bullet muffler. I found a small diameter lightweight muffler that I wanted to try to run in the rear. My car runs our Bullet muffler in the center where the cat goes because of the JDM EVO9 rear bumper cover, I don't like to see a big muffler back there. This new muffler I found was very small in diameter, we named it the SD muffler (small diameter). I kept the bullet in the center and added the SD muffler to the rear, it took a bunch of the noise out of the exhaust. Anyway, the car was on the dyno, never unstrapped. I made a couple of pulls with the car that were in the 69x whp ran and then we swapped on the SD, the power went to 700.

Some of what I have seen makes no sense but the dyno doesn't lie and you can gauranfkingtee that if I am testing stuff like this for my own use and my own car there is no BS being pulled, I want my car to be as fast as it can be. To this day I run our complete 3" turbo back, bullet in the center and SD in the rear. The car has made 710 whp like that now on our dyno.

 

[livedsm4g63]

I guess I'm suppose to read it twice? When Im the one that found it? hah. Silly 94awds, tricks are for kids.

 

[Mello]

where did I say there was an exhaust test in this data?

Isn't this thread discussion about exhausts? Do you have anything relevant to the subject? What am I missing (besides no data & only opinions from the naysayers)?