Looking for a 4" catback (Apex'i?)

[!^3]

I have heard rumors that Apex'i makes a 4" catback for the 1g AWD DSM. Is this true? I can't speak Japanese so their www.apexi.co.jp site doesn't really work for me, . I can't find this exhaust with any of the typical vendors either...just Buscher with their 3.5" (another exhaust that I am considering). If anyone has any info or a link, I would greatly appreciate it!

 

[DSMSpyder99]

there is no need for a 4" exhaust the fastest drag DSM owned by John Shep runs a 3.5" and he runs 8's. The 2G that came in second in the Ultimate Street Car Challenge by SCC owned by Roy runs a 3.5" exhaust. I cannot see how your gonna need a 4" exhaust

 

[!^3]

Thanks for the input. I should note that I am not a dumb newbie, this seemed like the only viable forum for my search.

I would like to note that this seems to be a fairly new exhaust; perhaps this is why no one uses it yet, or due to sponsorship reasons (I don't think Buscher would want anyone using an Apex'i part on their sponsored car, heh heh). Either way, a larger exhaust, as far as my fluid dynamics experience credits itself, will never ever hinder a turbo vehicle's output. Low range hp may be affected due to the turbo having not spooled yet and the vehicle is working as an N/A car, and thus benefitting from the added back pressure. However, the added flow will help spool the turbo faster, lowering the point at which the car goes from N/A to force fed (in other words, when it builds boost). In fact, any backpressure that can be released/avoided will reduce resistance of the turbine wheel (turbine wheel resistance is not something anyone wants). In theory, the best exhaust would be one that ends right after the o2 sensor, but then it is hard to avoid having the O2 sensor measure the outside air.

Personally, I'm not sponsored, I'm building up my 4g63 for a very large turbo, and I simply want to see what is available.

Now, does anyone have any info on a 4" catback made by Apex'i?

 

[Randomrage]

Um, Apex'I has a US site?


http://www.apexi-usa.com/

 

[boostedinaz]

Thanks for the explantion but we are not newbies either. For some reason this has been a big deal lately. We know that no exhaust is the best but for most the people on this board they dont even need 3 inch let alone 3.5 or 4. Bucher has a complete fab shop so I would imagine if they wanted 4 inch exhaust they could have made it. It isnt a matter of names or flow its a matter of will it fit and do I really need it. Not to mention these cars have been around for over a decade now and no one has made exhaust that big, I wonder why???? I am guessing, one, becasue no needs it, two, since no one needs it there is no market for it, and three, it would be a BIG PIA to make it fit.

http://www.dsmtuners.com/forums/showthread.php?t=116796&highlight=4inch

Check that out. Three pages of what you want to know.

Michael

 

[ITSME4G63]

4" = overkill , shit good luk trying to squeeze one in.

 

[!^3]

Um, Apex'I has a US site?


http://www.apexi-usa.com/

Sweet, thank you! Doesn't look like the GT Spec has been released for the DSM yet, but should be soon I hope. Maybe that's why no one uses it yet

It seems that most of the feelings toward 4" exhaust are merely "I don't need it, why would you?" or "Shep doesn't need it, why would I?" No one has actually taken two cars and performed actual dyno tests between 3", 3.5", and 4", so I will trust physics before I trust anything else. IMO, everyone needs 4", so why not? Even Shep would benefit from it. That and I will need to go with something larger than 3" for the power I intend to make by next summer and the Apex'i seems to be priced cheaper than the Buscher...and it bolts right up to the 3" N1 downpipe.

Also, Apex'i is supposedly the only company in the world with a 4" mandrel bender (actually 3.8").

Thanks for the link to that thread, but I found it rather useless...more like a bunch of people not knowing what they were talking about. Are they saying there is a magical formula for exhaust sizing? And it changes 2-3 times throughout the thread! Are we supposed to take an average of what people think, or go by hard numbers? Forums are great, but that is an example of why forums are not. Just a lot of people who mean well, but overall, they are only providing their own personal speculation. Which I wholly respect, but the base of most of these speculations is ungrounded.

Just because we haven't seen an exhaust this large until now does not mean anything...not so many people have been putting out 700+ until recently with DSM's! Turbo engineering/design has come a long way in the past five years, both in efficiency and economics, and the sport compact scene is now benefitting from it, allowing us to get mad power out of smaller engines. They've been getting 1000+hp out of 2 liters for years (i.e. Pikes Peak Tacomas in short distance hill climb form were putting out 1400hp with a 2.1 liter). Most of these vehicles use short side exhausts or very large diameter exhausts. Exhaust size does not change for DSM's...instead, flow and the basis of the aspiration of a 2 liter govern exhaust sizes. I am sure years from now people will think 4" is more accepted as people continue to raise the bar of output as engineering brings down the pricing of large-power modifications. But we shall all see

 

[IAMCLP1]

Dang I thought I was cool because I needed a 4 inch intake for my "large" turbo.

Look at it this way, dont you think if John thought that a 4inch would be better he would use it? We ALL know he has the Money, Time, and Resources to do it. If you can run low 10's on a 3inch why not save yourself some money and just use it?

 

[4g64GST]

Also, Apex'i is supposedly the only company in the world with a 4" mandrel bender (actually 3.8").

I work for an exhaust wholeseller in dallas I know people with
2", 2.25", 2.5", 3", 3.5", 4" and 5"

they are all very common,

actually, it is easier for me to get 4" and 5" inch mandrels than 2" and 2.25"

 

[boostedinaz]

I see what you are saying, but the reason members on this board go with what Shep or Buscher have done is becasue they have the fastest DSM. No one goes that fast by just guessing or on hope. Physics said that it is immposible to get a vehicle to go over 300 MPH in a quatermile distance from a stand-still, so it can be wrong. Not to mention common sense should over rule science. Most of the biggest finding in the world went against science. I hope you can dyno and let us all know what you have found and finally close the book on the 3, 3.5, and 4 inch debate. Good luck.

Edit: I just read you post again it is obvious that you, have read or know, a good deal about the dynamics of exhaust flow. With that said I would think you would go with a larger O2 housing and DP than just 3 inch. Also, bigger exhaust will help spool up not hinder it, so I am a bit confused as to some of your thinking.

Michael


PS. What kind of power are you "going" to be making?

 

[VRMAN]

Hey guys,

Maybe he doesn't care. He asked if anyone had any info on Apexi's 4" exhaust for his DSM. I didn't see the title saying "Is a 4" exhaust necessary?" or "Why doesn't Buschur run a 4" exhaust?"

He asked if anyone had any info on it. If you don't then save your replies for areas where your input can be used.

This is another reason I don't like this being called the General/Newbie forum as they really should be two different places. General is just that, but this forum seems to solicite dummied down answers too much.

 

[boostedinaz]

Hey guys,

Maybe he doesn't care. He asked if anyone had any info on Apexi's 4" exhaust for his DSM. I didn't see the title saying "Is a 4" exhaust necessary?" or "Why doesn't Buschur run a 4" exhaust?"

He asked if anyone had any info on it. If you don't then save your replies for areas where your input can be used.

This is another reason I don't like this being called the General/Newbie forum as they really should be two different places. General is just that, but this forum seems to solicite dummied down answers too much.

I thought this was a discusion forum not an question and answer forum. That would make for a prettyy weak forum board IMO.

One person ask a question then gets an answer and it gets closed. He asked a question got an answer and kept posting, therefor starting a conversation. I also dont see how your post did any better to answer his question that anyone else who has responded. Alot of members want something that they may not need and if they get some info then it can save them alot of time and money in the long run. If he truly wants it then he will get it and that will be that. I just tossed some info out there to let him think about, nothing more.

Thanks for your contirbution to the thread, it was quite helpful.

Michael

 

[4g64GST]

just remembered this thought it was interesting

flow numbers for exaust tubing only, no muffler.

2.25" 390 cfm
2.5" 472 cfm
3" 704 cfm

This is the recommended exhaust size for a race application
( I dont agree with this, but it is only a general idea, ever car is different)

2.5" 150-200 hp
3" 200-250 hp
3.5" 250-350 hp
4" 350-425 hp
4.5" 425-500 hp
5" 500-650+ hp

 

[!^3]

Hey guys,

Maybe he doesn't care. He asked if anyone had any info on Apexi's 4" exhaust for his DSM. I didn't see the title saying "Is a 4" exhaust necessary?" or "Why doesn't Buschur run a 4" exhaust?"

He asked if anyone had any info on it. If you don't then save your replies for areas where your input can be used.

This is another reason I don't like this being called the General/Newbie forum as they really should be two different places. General is just that, but this forum seems to solicite dummied down answers too much.

Thank you, my thoughts exactly. Although I do like the discussion thus far.

boosted, sorry if I came across as though a larger exhaust would hinder spool up...larger will help it. The larger exhaust will reduce backpressure which the engine *in theory* needs when running at N/A in order to make power (ex. large exhaust on N/A car=no good past a certain point). However, once the engine hits boost and pulls out of vacuum, flow increases as resistance approaches infinity=turbo cars will only benefit from larger exhausts. I hope that makes more sense.

Oh yeah, I'm totally in agreement with Shep/Buscher knowing their stuff. Why else would I have a Shep racing tranny They know what they are doing and they do it well. However, my guess is Buscher would rather Shep used a Buscher exhaust than a competing Apex'i exhaust. And again, the Apex'i is not yet available as I have found.

My biggest concern is having a 4" for clearance. Idaho winters here can get pretty bumpy Oh yeah, we do drive cars in Idaho (I know someone was bound to ask it ).

 

[!^3]

just remembered this thought it was interesting

flow numbers for exaust tubing only, no muffler.

2.25" 390 cfm
2.5" 472 cfm
3" 704 cfm

This is the recommended exhaust size for a race application
( I dont agree with this, but it is only a general idea, ever car is different)

2.5" 150-200 hp
3" 200-250 hp
3.5" 250-350 hp
4" 350-425 hp
4.5" 425-500 hp
5" 500-650+ hp

Thank you! Although that second set of numbers seems very under-estimated, the first set is what I am talking about; flow, not hp support (flow supports hp, hp does not support flow as many of you know ).

I hope we are not getting too technical for the "newbie" forum

 

[boostedinaz]

just remembered this thought it was interesting

flow numbers for exaust tubing only, no muffler.

2.25" 390 cfm
2.5" 472 cfm
3" 704 cfm

This is the recommended exhaust size for a race application
( I dont agree with this, but it is only a general idea, ever car is different)

2.5" 150-200 hp
3" 200-250 hp
3.5" 250-350 hp
4" 350-425 hp
4.5" 425-500 hp
5" 500-650+ hp

Were did you get those numbers??? I would like to know the test setup. Did they use a flow bench with a short piece of pipe or did they have something specialy built and use a long piece of pipe. The longer the pipe the more accurate the numbers if the pipe lenght matches the overall pipe lenght of the car it will be used on. Obviously bends in the pipe will decrease flow numbers. I think it would be interesting to see an entire exhaust system flowed to get somesort of CFM number.

Thank you! Although that second set of numbers seems very under-estimated,

I was thinking the same thing. My exhaust will only support 250 hp. I doubt it. Those may be off a bit even if they were wheel HP numbers.


If you go 4 inch why not go 4 inch from the O2 housing back and not just cat back. Another option would be to use a big 4 inch DP with a 4inch cutout and then a 3 inch cat back. That would give you flow but also give you better clearance. Alot of the GN guys do something like that. Just food for thought.


Michael

 

[leet]

Have fun getting that ton of piping to fit under your car. You REALLY do not need it.

 

[VRMAN]

I thought this was a discusion forum not an question and answer forum. That would make for a prettyy weak forum board IMO.

One person ask a question then gets an answer and it gets closed.

Michael

I don't agree, this isn't a "discussion" board nor is it a question and answer board. I think the thread and poster dictates what way that will flow. If he posted "Opinions on running a 4" exhaust" then it would be a discussion thread.

And to be honest, your opinion on the validity of my post is the last thing I care about. I made my statement and stand behind its reasons.

 

[Randomrage]

Have fun getting that ton of piping to fit under your car.

This is the correct answer.

 

[!^3]

The biggest concern, as has been discussed, is fitment. These cars simply are near imossible to fit much larger than a 3" downpipe without making major mods to surrounding metal. However, an exhaust that increases in diameter at a certain rate (8 degrees is optimal) is very important, leaving the downpipe at 3" is acceptable in our 4" exhaust theory.



For the person wondering what I am intending to do with my car, here are my goals:

Stages 1-3 will occur this year:

Stage 1 for my car is AEM EMS, UEGO WB O2, BJ's stage 3 race head, and built bottom end (these have been already purchased and being installed at the end of the month). Car will be run on the small 16g kit I have right now until August when a friend is buying the kit from me...

Stage 2 will be FP3065 turbo, Innovative turbo header, Tial WG, 720cc injectors, aftermarket fuel pressure regulator (August)

Stage 3 will be small things...coil on plug/MSD DIS-2, Fluidyne radiator, etc. (during the winter. No race season here in Idaho during the winter so I work more on tuning dynamics throughout this time).

Stages 4-7 will be for 2005:

Stage 4 roll cage, carbon fiber race seats, Ralliart or other 4 point harnesses. (April)

Stage 5 head will be further ported from 280 cfm to over 320 cfm. Replace Crower 65lb. single springs with Crower 85lb. double springs. (June)

Stage 6 will be tuning, tuning, and more tuning. If the bottom end breaks, Ross and Crower's go in (although the Wiseco/Eagles I am beginning with should hold up very very well). Weight reduction finalizing and perhaps body updates (new paint, fix my dent in the unibody, darnit, ). If my Shep tranny breaks, I'll go to a Quaife front/center LSD to replace my 4spyder current setup. However, I really doubt this thing is going to break if I take good care of it. I will, however, go to an ACT2900 or ACT3200 clutch kit. (July)

Stage 7 we'll see what the FP3065 can do for hp. I'd like to be getting around 600 out of the setup with race gas/high boost (25-30). However, for my 800+ goals, I'll be turbo shopping throughout this entire time. (August)


I don't know how serious I will get about pro-dragging or anything; I am mainly doing this all for fun and to learn more about modifying cars (I chose the DSM platform is probably the lowest cost/highest yield platform in the sport compact market). Eventually I would like to be working as a staff photographer/writer for a major automotive publication. With my current job as a photo editor for a major university newspaper, I've been able to develop my photography/writing skills quite a bit, but now I need to focus on automotive knowledge and I hope this project will help me do just that.

Thanks again for everyone's input; it is greatly appreciated. If anyone wants to discussing exhaust sizes, I'd love to

 

[NewB2dsm]

just so you guys know. That 3.5" exhuast is a class mandated for what shep is running in. So he can only run as big as 3.5" maybe thats why buschur only makes a 3.5" exhaust. 4" exhuast is overkill yes, but would it hurt? no.

 

[boostedinaz]

I don't agree, this isn't a "discussion" board nor is it a question and answer board. I think the thread and poster dictates what way that will flow. If he posted "Opinions on running a 4" exhaust" then it would be a discussion thread.

And to be honest, your opinion on the validity of my post is the last thing I care about. I made my statement and stand behind its reasons.

To dictate means to have sole control. On an internet forum board he has no control what so ever so he can only ask or discuss.

As for the validity of your statement I dont care either and I would hope you would stand behind it. I just dont see the point in comming into a thread and not helping but guessing what the thread starter wants and then tell that as the truth. He may have wanted a discussion and it seems that he has becasue it has gone on long after he got the "answer" to his question. With this said I will leave this bickering to PM's or something that doesnt do what I just described above.

Michael

 

[crankbender]

To take the antagonist position here with physics.

In the exhaust stream you do not want to slow the velocity down too much. This will cause a plume out of the turbo/dp and actually increase resistance. Also by increasing the diameter of the pipe you may be increasing the heat loss and consequently the velocity change. This can in turn increase the dynamic pressure at the turbo outlet. I have not totally modeled this sytem and can't give you a definative answer other than this. Bigger isn't always better.

If you are going for 800+ you may want to send me a pm about alternative fuels. With the correct fuel people have pushed 40PSIG with 11:1 compression.

 

[EvolvingGST]

why do you want an 800+ hp eclipse .... well all im gonna say is good luck... BTW: not insulting I just wanted to know... Cuz I don't think Shep's car is over 800 hp...

 

[MNGSX]

Any exhaust system does'nt need to start out full diameter...

Like 3" to the flex section 3.5" to the cat back then 4" or something.....

I guess my biggest question to most of these people looking for 3.5" and 4" exhaust is why do you think you exhaust tubing that makes your turbo intake pipe look puny?

I mean if that is'nt freeking huge as well as the rest of the turbo you are'nt moving enough air into the engine to need a pipe out the bumper that big to get rid of it...