IceY2K1

iTrader: (3)

Anybody think an aftermarket Y-pipes' removal of 18-20" of exhaust runner(piece from exhaust manifold to Y-collector) length from the REAR bank could cause long term damage? Is this even a possible issue?

I know the VQ will last forEVER, but is it even worth worrying about uneven backpressures, uneven combustion gases exchanging, whatever reasons Nissan had for purposefully INCLUDING the extra 180* bend and extra 18-20" of tubing in the OEM Y-pipe? If not, why?

Today, I ROUGHLY measured the STOCK exhaust vs. Cattmans' Y-pipe and the rear bank loses ~18-20" of exhaust runner length, while the front stays the same. I'm wondering if Nissan engineered the equal length runners for a reason(balancing/coordinating exhaust pulses?), other than trying to fit the precat.

Any ideas appreciated. Thanks.

BigDogJonx

iTrader: (7)

Im not following you on the unuequal part of the Ypipe. I still have my stock Ypipe and the only thing different seems the extended flex section where the Cattman has a shorter one.

Dixit

IceY2K1

iTrader: (3)

Roll over the Y-pipe and see under the rear bank precat shield?

If not, maybe I was looking at a different year, since there were about 2-DOZEN Y-pipes laying around.

Got pics?

BigDogJonx

iTrader: (7)

You are SOOOOOO right. Last night I was right, now you 100% right.
And yes it is almost 3am here and I am taking pics of a freagin stock Ypipe. Does that not constitute a true modder and need for help?





But you can see it is very very restrictive. That bend has to kill the flow bigtime.

Dixit

IceY2K1

iTrader: (3)

Just play'n.


Yeah, I know why the Y-pipe gains so much, but I'm wondering about the side-effects. There could even be some more power in there if the runners were equal length, but designed with flow/exhaust optimized as Nissan did. Wait, so why is that 180* there again?

I don't know, that's why I'm asking for help. BTW, thanks for the pics again.

BigDogJonx

iTrader: (7)

Yeah my toes look a bit retarded cause I compressed the image to get it below the 50k limit on the board so I guess that part of the pic got screwed. Honestly they dont look like that!!! hahaha Just messing.......

I dont see if there would be any advantage to making it equal length. I mean it all translate in one big pipe regardless. So backpressure cant play a part in that if you think equal length might be better.

Man I need to get some type of sleep pill. Here I am up at 3am, and need to get ready for work in 3hrs. Yeah think im an insomniac.

Dixit

IceY2K1

iTrader: (3)

Same here, except the 3hrs. part.

VeeQueue

iTrader: (1)

I'm speculating that the rear bank's precat is the reason behind the extra piping/bend. If Nissan installed the rear bank's precat without the extra piping bend it would've prevented them from using the looooong flex section.

IceY2K1

iTrader: (3)

I thought of that too, but they could have integrated it into the exhaust manifold like they did on the front(CALI spec only) and still had room.

BigDogJonx

iTrader: (7)

You are right there, you can clearly see that the bend has the precat on it. Cause the front bank one gets the precat from the calispec manifold.

Dixit

BigDogJonx

iTrader: (7)

Yeah but the Cali spec manifold is not part of the exhaust manifold. It is the very large 6" diameter pipe. That is why the Ypipe is straight on the frontback side, unlike the 2k ones that also bend upwards like the rear back Ypipe.

Did you ever see DesertPearl's Cali-spec to FedSpec conversion in the HOW TO in the 5thgen? You can see how big that cali-spec manifold is.

Dixit

IceY2K1

iTrader: (3)

Yeah, that's right. If the rear was like the front then they wouldn't need the 180* turn, but there doesn't appear to be enough room.

BigDogJonx

iTrader: (7)

You know what I just thought about??? That the headers that OBX planning on putting out in a month or two are not going to work for Calispec. Unless they putting out two different types.

Cause its obvious that the header is different cause the cali one has like 6 bolts where the cali-spec manifold is connected, the regular one has three. Only reason Im interested in the headers is for the supercharger, i think I should be able to get a good amount off it with a boosted car. Damn this ****es me off.

I guess I jumped cause i saw the 2000-2001, I know they probably just messed up, unless if for the very remote chance they planning on making two different front headers. I mean I could do what DesertPearl did but that means all this crap of getting a new Ypipe and rewiring the O2s and all that, I dont want to go through that.

Dixit

IceY2K1

iTrader: (3)

Good excuse to get a 3" FED pipe? Man Dixit, you got money to burn!

dmbmaxima2k2

iTrader: (1)

the reason for the bend is to add length and to give EQUAL LENGTH exhaust tubes from both side which in theory should give a better power distribution since the exhaust pulses will precisecly meet at the collector. they make headers like that for mustangs and stuff i know and the ones that emax got for his 4th gen from new zealand were like that too. it won't hurt the car but maybe that's why 5th gen guys don't see as much of a gain from a y-pipe.

IceY2K1

iTrader: (3)

Thanks. That confirms most of what I've been told about the exhaust pulses meeting at a certain time at the collector. Timing the pulses with the length of the pre-collector tubing is KEY to maximizing performance.

The Stillen and Cattman Y-pipes are clearly NOT designed with this in mind. They were more concerned with eliminating one precat and the O2-sensor squished portion of the tubing along with MUCH CHEAPER production cost.

BigDogJonx

iTrader: (7)

Wrong Steve, the reason for the equal side length on that is clearly because the precat is right there. There is no other way to fit that precat. And how is you think the 5thgens are not getting enough gains from a Ypipe? I have seen dynos from 8-12fwhp, that is not enough for you?

Equal length in exhaust cant do much, pipe is a pipe, like two water hoses meeting a T, it dont matter how long one end of the T is, the water is still going to meet at the T and mix and then flow. There is no restriction.

Dixit

mzmtg

iTrader: (11)

I just wanted to comment the the 5th gen OEM piece looks like a MUCH MUCH less restrictive design the the OEM 4th gen Y-pipe...

IceY2K1

iTrader: (3)

I'm going to try and get this right, but don't hold me to it being 100% accurate.

Basically, with headers it's VERY critical to time the firing, ehaust valves opening, and the ehaust valves closing BETWEEN all the cylinders. Ideally, you want a COLUMN of air moving out the exhaust NOT a waveform(high-low-high-....). Now for this to happen the cylinders firing sequence between the two banks must be accounted for when the exhaust gasses leave each cylinder and meet at the collector. You don't want for example cylinder #1 and #4(example I don't know the firing sequence) to "run into" eachother at the collector. You want cylinder #1 to just finish entering the collector as cylinder #4 begins. The reason for this is that previous fired cylinder "pulls" the following exhaust pulse and thus aides in creating a constant column of air that flows with the proper velocity to clear the exhaust. Somewhat, similar to the reason you don't want to go to big on the exhaust tubing, because all though you decrease backpressure, you'll lose air velocity which can cause side effects such as turbulance, hot spots, etc...

BigDogJonx

iTrader: (7)

Very very detailed and good explanation. Obviously we dont know this for 100% sure, but if you right, then there would be a problem. But I am not saying you are wrong, just that if the aftermarket Y's are getting about 8-12fwhp, that is damn good. But I do agree with you on if they were equal length pipes "it could" be like 3-4fwhp more. COULD is the key word. But as far as I know this is not the case cause most Ys from other engines like Toyotas and Hondas and Mazdas have similar Y's of unequal length. And the only reson I cant believe in this theory 100% is that the bends on that rear bank Ypipe is so visicious that is kinda puts it to rest cause that alone causes major restriction and flow movement. Requires more pressure to get it through there than the other side. That would could problems in that bank alone.

Dixit

VeeQueue

iTrader: (1)

I dont have the factory service manual in front of me, but i believe the firing order is

R 135
F 246

or

R 246
F 135

dmbmaxima2k2

iTrader: (1)

yes equal length headers do matter(dixit), nissan did it for a reason and it's very difficult for an aftermarkter company to duplicate that.

i was not wrong and i did not say that 5th gen's did not see enough of a gain just not as much, 8-12 is good but 4th gen guys see more, WHY because the stock 5th gen y-pipe was designed a little better.

IceY2K1

iTrader: (3)

Thanks, but it was just an example. I really don't need to know that, at least right now.

Anachronism

I posted a thread on this a couple of weeks ago -- http://forums.maxima.org/showthread....hreadid=141608

Does anyone know what the Middle East Y-pipe looks like? They don't have emissons equipment, right? If we could see a ME ypipe we would know what Nissan thought was the best way to make a y without precats.

IceY2K1

iTrader: (3)

Guess I didn't search. Oh well.

VERY intriguing idea about the Middle East Y-pipe. If someone can get one, I'll see if I can get it made for a reasonable price. However, I've been told at least $1K for a prototype, so the cost-to-benefit would probably not be worth it.

Maybe one of the guys supplying the ME VI manifold would be able to find one.

NightRider

iTrader: (6)

Did anyone ever notice that the Budget Y-pipes took this into account? They use a smaller diameter pipe in the rear to make up for the larger, longer front pipe. This is supposed to equal out the exhaust pulses much like the equal length piping.