I realize that I am not considered an expert here but I do have a bit of a following on other forums and find exhaust upgrades very interesting.

I noticed both the Fujitsubo and Unlimited Y-pipes and was very impressed with the quality of manufacture. The welds look like machine welds and the construction looks in line with premium Japanese workmanship. Very nice parts for the price.

They also "look" identical. In reading the information the Fujitsubo claims 2.25 primaries with a 3.00" merge outlet. The Unlimited claims 2.50" primaries with a 3.00" merge outlet. I did a VERY unscientific measurement with a precision caliper that shows in both standard and metric. I measured the primary and secondary pipes for the stock, Fujitsubo and Unlimited Y-pipes and calculated the percentage difference between there respective pipes. I also compared the percentage difference between known standard and metric pipe sizing.

Again, measuring of my MONITOR is not "admissable in court" accurate but gives at least a basis for comparison.

Of the pictures the Unlimited was probably the best to measure as it was available in the largest picture and flat to the camera to minimize perspective variables.

Here are the results:

Unlimited: secondary is 33% larger than primaries
Fujitsubo: secondary is 33% larger than primaries (identical to above)
Stock: secondary is 20% larger than primaries.

Here are some ratios of typical pipe sizes.

60mm/50mm (very common stock Japanese sizes, 2.38"/1.97"): secondary is 20% larger than primaries

75mm/60mm (very common aftermarket Japanese sizes, 2.95"/2.38"): secondary is 25% larger than primaries

80mm/60mm (very common aftermarket Japanese sizes, 3.15"/2.38"): secondary is 33% larger than primaries

2.50"/3.00" (very common US spec sizes, 64mm/76mm): secondary is 20% larger than primaries

2.25"/3.00" (very common US spec sizes, 57mm/76mm): secondary is 20% larger than primaries

So, based on the above ESTIMATES and the actual ratios of known pipes... I would suggest the following as probable.

All three parts are most likely made in Japan and are therefore metric sizes.

The stock pipe sizes look to be 50mm primaries into a 60mm secondary.

Both aftermarket pipes are the same size and look to be 60mm primaries into an 80mm secondary.

Another observation is that the stock pipes are crush bent and therefore even SMALLER in the curves than the 50mm unbent sections.

Now, if either of the 2 vendors would care to measure and post the ACTUAL pipe sizes for the stock and aftermarket parts it would be of interest at least to me.

 

Stock pipe picture



Fujitsubo



Unlimited

 

my only question is, why would nissan put a TON of cash into developing a beautiful engine like the VQ35DE and then, stick exhaust like that stock piece on it.. makes no sense to me

 

here is the JIC / BULLET Y-Pipe

JIC Y=Pipe





Tanabe has just released pictures of their Y-Pipe... but... IMHO the JIC still looks best...

 

That JIC part does look good... do you happen to have the pipe dimensions? It looks like another 33% ratio. 60mm primary and 80mm secondary is my guess.

That said, and assuming my guess on the stock Y to be accurate at 50mm/60mm, and considering the horrible bend in those 50mm pipes... I would think well shaped 2" pipes (51mm) would be a noticeable upgrade with a 2.5" (63mm) center pipe. This is a 25% ratio.

If you have too dramatic of a change between the primary and secondary pipes your flow velocity really drops. Of course this also occurs with the primary pipes. Remember, each side of this engine is ONLY 1.75 liters. Giving that a 2.38" pipe (60mm) is NOT going to help low to mid RPM torque.

Honestly, IMHO, all of these aftermarket pipes are TOO large in diameter. Preserving/enhancing low to mid RPM torque make an engine FEEL very good and is much more fun to drive than gaining some top end at the expense of low/mid rpm torque.

While you guys are concerned with the stock pipes you may want to consider what Lexus did to my 290hp engine. A SINGLE 50mm center pipe!!! And yes, with that pipe my 4000lb sedan went 14.22 @ 99.38mph at Houston Raceway Park... open 3.27 differential, stock 225/60-16 Bridgestones.

I have components to build a better exhaust. I am going to run 2.25" primaries and have two Y pipes, one with a 2.5" outlet and the other with a 3" outlet. I intend to test both to see what works better. FYI, my engine is identical to the 1998-2000 GS400 with the exception of the GS has a 60mm center pipe and is rated 10hp/10tq more at the same rpms. My LS400 is rated 290hp @ 6000rpm and 300tq @ 4000rpm.

 

I just busted out the micrometer...

NISMO y-pipe is 58mm / 77mm

JIC y-pipe is 54mm / 74mm

any others I should measure?

 

or you could just eliminate the y pipe all together


true dual anyone?

 

you can run a true dual exhaust...

like STILLEN / INJEN /

 

Thank you Brady and Jason for looking into all this!!

I think this is very helpful to everyone shopping for an exhaust like myself.

I really like the stock exhaust tone on my G. and esp now with my popcharger/plenum/cats. I am thinking about getting just a Y-pipe for now but I am torn btw a 3" and 2.5" collector size...
should I go for a 3" + transition tube to stock exhaust? this would be more flexible if I want to get a nismo/fujistubo later.

how is the stock G muffler?


Also, when you look at the Y-Pipes, the JIC has less "turns" and wider angles but its turn radius are tighter. is the only way to compare thru flow bench and/or dyno?

 

Jason, thank you for taking the time. If you get the chance to measure the stock sizes that would be good for reference.

That said I am a bit puzzled by your measurements. I get the following from my measuring calipers:

54mm = 2.125" (2 1/8")
58mm = 2.29"
74mm = 2.92"
77mm = 3.03"

Except for the 54mm size... none of these seem to be standard pipe sizes. 50mm, 2.00", 2.125" (not common but available), 2.25", 60mm, 2.50", 2.75", 75mm, 3.00", 80mm, seem to be the most common factory and aftermarket sizes with the metric being Japanese and the Standard here in the States. Pipes can vary in diameters in turns even with mandrel bending. Also the overlap at the Y itself is another area that looks larger than stock. Are you pretty confident in your observed measurements?

That said, I would gamble that the JIC system will make the best torque under the curve. The 2.125 primarys should be a very good compromise between higher flow and not too large. I also like the merge angle. Some unbiased testing would be nice to see.

fluff, thank you for noticing...

Depending on the actual stock center pipe measurement... I would think the smaller pipe size to be your better bet. Although from what I have read so far and from what I have noticed from many suppliers... confirming ACTUAL pipe sizes is recommended.

If the stock center pipe is 60mm OD (outside diameter) that would have an ID (inside diameter, the important dimension) of approximately 55-56mm. A 2.50" pipe has an apx ID of 58-59mm which gives at most a 2mm lip (not perfect but not bad) whereas a 3.00" OD pipe has apx a 72-73mm ID for a 8mm or so lip. If you choose this I would make some effort to smooth the transition. This could be done is a few ways all of which require fabrication skills. However, the smaller primary pipes of say the JIC may outweigh the transition problem. Also, if the 2.50" advertised size is actually bigger... ask questions before spending money.

 

let me add another y-pipe in the mix....

the kuruma Z fujisubo ypipe:
https://my350z.com/forum/showthread....0&pagenumber=1

 

Thanx, J, for this interesting thread. I am looking to purchase a ypipe. I noticed the differences in the diameters btwn the ypipes being offered for sale on this site as compared to stock, and i wondered out loud in another thread "why the differences?", and "which offers the best performance based on its dimensions?", but I could get no definitive answer. It seems that no one knows for sure, that no comparative experimnts have been performed. So when i saw your thread, i thought it had the answers to my questions initially, but as i think about your measuring technique, it seems as though there is just too much potential error inherent in your "monitor measuring" method. I am not an engineer, but i think you are, and i'm gonna subscribe to this thread in hopes that your research will lead to the answer to my main question which is "which ypipe offers the best performance for my setup: kinetix cats pre-ypipe and stock exhaust post-ypipe.

 

MGL, got it, second picture in first post. Now if we could get someone to actually measure the pipe sizes that would be good for as Z BOY points out (and I said on the onset) my guesstimates made from monitor measuring are not exactly scientific.

Z BOY, I realize that most people don't want to or care to know WHY a part works... they just want to bolt up the best performing part for their money... I on the otherhand find exhaust science very interesting.

A very thick book could be written and still not cover all the variables but for simplisity sake let me state (and you can quote me) that the SMALLEST size exhaust pipe that gets the job done is BEST.

This may be counter intuitive at first and many people WANT to bolt on the biggest tubes they can get... with less than optimal results... often, less than stock power (at least in the low to mid RPM range but sometimes even peak power is reduced).

Now the KEY to my first statement is the word "JOB". When the exhaust valve first opens there is a tremendous amount of energy released. The JOB is to preserve this energy so that it can be used to enhance the flow of adjacent exhaust ports that are at a different phase. Poor flowing pipes obviously restrict this energy flow. What is not so obvious is that too large of a pipe can actually create MORE reversion at key times in exhaust ports and therefore reduce torque/power compared to UGLY stock parts. This is a very complicated subject but the bottom line is velocity. The smaller the pipe the higher the velocity for a given flow. The higher the velocity the lower then tendency to "reverse" flow.

So, anybody that has any of these systems are encouraged to measure the pipe sizes so that performance and designs can be compared with the end result being the best part for the application.

Of course turbo and supercharged engines have different flow volumes and therefore will need a larger diameter than stock... but how much? Turbo Supras often make 600-700+hp through a single 3.00" system... so how big a pipe does a 300hp engine REALLY need?

 

i just swaped my mid-pipe and NISMO muffler out today and kept the NISMO y-pipe, stock mid pipe and muffler. The car is much more responsive. This may not equate to much more hosepower, but the engine response is noticiable. Even the mechanic noticed.

so far to date, i have swapped out the two most restrictive parts: cats and y-pipe. i will dyno once my transmission is fixed.

 

we have the Ultimate Racing Y pipe specs here:

http://z1auto.com/prodmore.asp?model...ust&prodid=579

 

Then maybe the yettobereleased kinetix ypipe, which i believe has the same dimensions as stock but probably better diameter consistency, would be the best choice for my setup?

 

Very interesting. Especially since the NISMO Y-pipe outlet is 77mm/3.00" and is mating to your stock mid pipe which I am guessing at 60mm (someone want to add the stock dimensions?)

So, you have a sharp edge protruding into your flow at the Y to Mid flange and yet you feel more low/mid torque due to the velocity (no folks, it is not the backpressure making more power )

Z1 Performance, nice array of parts you guys carry. Had not seen that Y-pipe yet. Happen to have any exhaust dyno graphs?

 

Don't confuse this "Ultimate" pipe with the "Unlimited" pipe! Shape of Ultimate's looks better--more direct, but obviously, shape is only one consideration. The "ultimate" test would be to dyno/flow test all of them under the same conditions. Kind of a ypipe shoot-out. I would really like to see this done! These manufacturers should put their pipe where their mouth is and see which blows the hardest--god that sounded gay.

 

That could be the best setup for most cars... of course the execution including internal surfaces and the merge area are unknown but stock dimensions in mandrel pipe with straighter sections should easily outflow the stock part while maintaining velocity.

A good way to think of this is if you remember the days of the carburetor. Stock carbs were rated at a vacuum drop of something like 1.5 in/hg vacuum. (4 barrels anyway). A number of tuners found out that by smoothing the surfaces of the venturis and housing that they could create a much higher flowing carb while keeping the exact same butterfly valve size. So, all pipes are NOT created equal. Even pipes with the same size... bends, merges, collector area and merge angle, internal surface, O2 sensor bung placement all effect a parts performance.

There is also a post about a member that removed his resonator and "feels" that the car is less responsive. Tone change can make the brain "think" things (that is why the but-dyno is often wrong... loud equals power... right?) So I cannot say if he gained, lost or stayed the same BUT removing the resonator certainly could change the way the exhaust works with the engine. Even though resonators are straight through, and therefore have similar flow capacity to straight tubing, their accoustic size if different, hence the name. This change can effect a systems performance. These are just a FEW of the reasons that thorough R&D is a real plus when offering aftermarket parts.

 

From another thread:
Let's talk ypipe diameters in inches:
Stock inlets=2.25";outlet=2.5"(??? can someone verify this???)
unlimited's inlets=2.5"; outlet=3.0" (from their website)
fujitsubo-style gb inlets=2.38"; outlet=3.0"(http://www.my35oz.com/forum/showthr...&threadid=83271)
Kinetix inlets=2.25"; outlet=2.5"
And we haven't even talked about weight comparison yet.


What if i decide to run N2O? How would that affect my choice of ypipe?