Cory Simpson

I don't think an X-pipe has an effect on rotarys does it?

It may, but I'm not sure of that.

Also, I used dual spintech shoot out muffler, and I would NEVER do it again, in my mind it was a waste of $180 bucks. And one of the worst sounding mufflers I ever heard. Because it really didn't do much muffling!

But they were some of the loudest street mufflers from spintech, so their more streetable versions may be quiter (most likely are), but I still don't think the sound would be improved.

Also Bonzitoyota did a single 3" with a spintech, and he hated his to! Said it was horrible for power (from what I remember on his thread). I don't think they provide enough back pressure for the rotary engine, it your car is turbo they may be fine, because that offers all the back pressure needed, and muffles the exhaust some to.

But if I were you I would go with raceing beat if you want performance and good sound. Or a quiter HKS system.

Makenzie71

X-pips and H-pipes are pointless. They don't do anything but add a restriction in the exhaust, disrupting flow. An exhaust seeking the best performance and sound will be a single exit or a true dual, anyway. If you're going to collect it at any point then your best route would be to go ahead and run a single.

Icemark

Threads generally don't get deleted, unless they cover useless info or are major repeats.

And if there are enough votes for 5 stars it gets archived.

But there is no reason to bump because you are worried about deletion. Please don't do it again.

Makenzie71

no problem...so do we have enough 5 star votes?

rxspeed87

on piston motors x/h-pipes make decent difference

and rotary motors do follow many of the same basic ideas of a 4 stroke piston motor so I would think that it woudl work there as well


this way you can keep a smaller cross section pipe to limit heat transer of the exhuast gasses to the piping as well as keeping velocity whlie allowing the two pipes to merge wich would help ones side of the exhuast help pull out the next pulse on the other side of the exhuast

tannji

I read something a long time ago about the ability of a properly designed H-pipe to tune and tone-down an exhaust note (not drastically, but some) but it was noted that this was at the sacrifice of a small amount of power, due to an increase of drag. I think part of the necessary design was how far from the manifold to place the H, and the lengths of the feeds into the H. (I dont remember if they had to be identical or not... just that it was part of the equation. This was back in the 80's, when I was doing my best to Rice a 280Z, tho rice still referred to bikes, lol.) Problem is... this was in reference to V8's, and the power parasitical wasnt as much of a factor as it would be on an NA FC. Someone I knew fabbed one for his L28 motor. We all noticed the nice exhaust note, and the guy swore he felt a difference in perf. Not too scientific tho, and the V8 guys I knew and semi-trusted swore he did it too far from the manifold. Any input on this idea, and how would we go about testing or proving? Is it even worth a test? Earlier in this thread someone said that RB systems were decent, but not designed as well as they could be, and too expensive for the yield. What is the current consensus on exhaust solutions now?

tannji

Makenzie71

No matter how it's designed or used or whatever, an X-pipe or an H-pipe will do nothing but add a restriction in the exhaust path. No good can come of it...not performancly speaking. Either design adds a specific volume to the exhaust plumbing that the engine has to pressurize before the backpressure-enduced effect of scavenging can take place. This extra volume slows exhaust gasses down, which in it's self, adds a great deal of resistance. On top of that the change in exhaust tubing consistancy changes and also causes significant turbulance. It's bad joojoo.

Just because they dont think stickers add horsepower doesn't mean they're not a ricer...some of them think X-pipes help, too...

rotarygod

iTrader: (1)

An X-pipe or an H-pipe are used on V-8s because they have 2 pairs of 2 cylinders per side that each fire 180 degrees out from each other but each pair is not evenly spaced with the other at 90 degrees firing but rather 45 degrees. It sounds a little confusing and is hard to expain without a picture so try to figure it out. Even with a good set of headers, at some point down the pipe this out of sequence pair of cylinder's gasses interact with the others in a way that pressure at that particular spot in the pipe builds up. This is where the X or H pipe is to be placed. Some of this added building up pressure is vented to the other side. Streetcars don't have room but some old race cars used to use 180 degree headers. These were frequently works of art that sent the pipes from 2 cylinders from each side of the engine over to the other side to merge in with 2 of those pipes. This way every cylinder feeding that header fired 90 degrees apart from each other. On this type of system there was no point in using an H or X pipe and the layout is actually superior. On a rotary, we always have equal spacing between each rotor so an X or H pipe would do nothing beneficial.

On V twin engines such as those on motorcycles like Harley's, it may be beneficial on a dual exhaust to add a crossover pipe right at the beginning of the exhaust near the engine. This just splits up some of the noise between both pipes a little and does practically nothing for power. The rotary may or may not work the same way in this respect but I suspect it is minimal.

rxspeed87

makenzie do you know what how an x-pipe works?
second do you know how scavenging works?

but many test have been shown with x/h-pipes to show improvement on cars

granted maybe not with a rotary but in theory I would think it would work for them as well being again they follow same 4 stroke ideas


but you have two pipes a and b
when pipe as lets an exhuast pulse go it creates a low pressure zone behind it (which also goes again backpressure) when it meets the x/h pipe what it does is also help create a low pressure zone in pipe b

this will help create a greater pressure differential which is going to further suck the exhuast gas out of pipe b

true there is a little extra volume in the exhuast which might make for a little more resistance but the pay off is worth it being it helps with scavenging on the other bank.... sorry but exhuast isn't so simple as just backpressure and volume either



please research on how the items work a little more
and think about why a lot of high end cars include them stock as well as many cars used in racing series if they are pointless?

rotarygod

iTrader: (1)

I think he was referring solely to the rotary and not a V-8.

rxspeed87

they also have an effect other then just the odd fire

it might not be as strong but the effect is still there and I swear somewhere I have seen dyno using system that fired always left right left right and so on with no odd fire in there
and gains where made by that with due to the above statement

Makenzie71

X-pipes and H-pipes add bends and joints and things that only add turbulance to the exhaust flow. This is a bad thing. Point one.

V-8's and V-6's fire in odd orders. An 8 usually fires in order of 8-1-2-7-6-3-4-5 or 1-8-2-7-3-6-4-5...this leaves many unbalanced intervals in the exhaust cycle. Due to this a propperly tuned H-pipe or X-pipe can be beneficial over a stock or near stock exhaust...but no matter how tuned the X-pipe or H-pipe is it will NEVER achieve the performance that a true dual exhaust.

A tuned H-pipe or an X-pipe is as beneficial to ANY vehicle's performance as any glasspack or mid-pipe. It helps...but why do it when you can get better results doing it right?

Another reason? H-pipes and X-pipes are junctions in the two individual exhaust routes. Not only does this cause a pointless restriction in the exhaust but it also weighs more. So lets not only spend more money for something that will not benefit us as much, lets add wieght, too.

Another reason? Not only do tehy add a sensless restriction in the exhaust flow, and weigh more, they **** a small displacement engine's exhaust wave frequency, which causes posative waves to hit open valves at the wrong times.

Want some more reasons? I got a few more...

Also, don't question my knowledge if you haven't taken the time to read AT LEAST the first page.

rxspeed87

I have read the first page
and disagree with a few things you said
but have have already covered that on supraforums.com

yes I am rx7speed


like you whole idea that backpressure is needed when it is not
yes it happens and when you get a good system in there you are going to have some it is inevitable
but the less the better as long as you are not going to large and killing velocity


as far as messing with the sound waves
that is why an h-pipe should be possitioned in tune with those waves
yes it creates a set of waves all of it's own just as mufflers do just as a cat does just as a collector does or your exhast tip for the most part anytime there is a change of volume you create a wave that heads back to the exhuast port

but if you put this item in sync with the rest of them at that point you stand to magnify the waves there to be even stronger

as far as the weight of an x-pipe that is nothing to worry about


as far as restriction in the exhuast this goes back to backpressure
back pressure is bad but yet to get the correct sized piping you are going to get a little backpressure. it's a compramise that pays off
same thing with an x-pipe



would you care to take a chance at disproving the reason I put forth about how it can help with scavenging by tying both banks together so bank a helps pulls bank b's exhuast pulse out?

rotarygod

iTrader: (1)

On a V-8 engine, if it does not have 180 degree headers or a dual plane crank (unless it is a true race car it won't), then it will absolutely need some form of crossover pipe for max power. A true dual will not do it. An X-pipe scavenges just like a collected system, an H-pipe does not.

On a rotary the effect is different due to even intervals. A true dual system is tuned with tube length and diameter based on organ pipe resonance but does not scavenge. Adding an H-pipe still won't make it scavenge since H-pipes don't scavenge. A collected system does scavenge however and so do X-pipes. Whether or not an X-pipe works good on a rotary is a good question that needs a factual answer.

rxspeed87

I would think the x-pipe would make gains
as far as how much of a gain I honestly don't know

as far as the h-pipe I'm sure it does do a little scavenging but it's efficiency is VERY limited and more often then not a just a balance tube in function


think we just need to get someone here who has some time and true duals to make up an x-pipe to there car go for a dyno then hook the true dual back up and see howthat works

Icemark

Actually there would be no gains from an X pipe at all in a rotary powered application.

Something that you are all missing as I read through the H-pipe X-pipe stuff in this thread is that the rotary engine fires at the same time, something that does not happen on piston engines.

The closest exhaust and firing equivalent would be the Honda dual firing piston engines that they R&D'd back in the 90s. Where in an 8 cyl engine two cyls fired at the same time. (so the engine worked like a 4 cyl with double the displacement).

The principles of a X pipe is to utilize the exhaust pulse from each cyl to drive the exhaust gases out at a high velocity. Where each fired cyl, emptying its burnt gas load, stacks up behind each other.

But with a rotary engine, each combustion chamber per rotor empties its load at the same time. So an X pipe or H pipe would simply stall the velocity of the gases being pumped out the exhaust pipe.

That is why there are such significant gains from the true dual system on a rotary engine. With using a non-connected true dual exhaust you are not forcing the combustion wastes out at the same time into the same pipe, or forcing the gases to intermix (reducing exhaust velocity).

To make it more clear, let use the ABC analogy mentioned earlier.

With a piston engine you have the exhaust gases entering the manifold and exhaust system like this:
A-D-B-C each following the other.
But on a rotary they enter like this:
AB-AB-AB
Or more accurately:
A+B
A+B
A+B

But never A-B-A-B-A-B

That is why a X-over of any pipe would not help the rotary engine. If it fired A-B-A-B where the timing if each event was separate, then there could be gains.

*edit<
Also to go back to some of the original size comments back on the front of this thread...

There was a missed concept of the expanding exhaust flow pattern of a non-turbo rotary.

Because of the large amount of un-burned as well as burning and burnt mixture ejected as exhaust inherent to a rotary engines operation, the exhaust gas continues to expand. Therefore the common piston engine concept of a single sized exhaust pipe does not utilize the full scavenging effect for a rotary engine.

What I am saying, is that a say 2.5 inch/dia exhaust all the way back, will not show the same scavenging effect that a 2" to 2.5" to 3" exhaust will. Mazda themselves used this concept on the stock N/A FC and FE with the dual muffler and expanding y-pipe set up.

But often with newer designed Piston engines (with their considerably lower exhaust gas temp, and more complete burned mixture) that same expanding design would result in a serious loss of scavenging effect.

So again, you can not compare the rotary engines operation to a piston engine or expect to utilize a common concept for every aspect of flow dynamics between two different power plants.

Makenzie71

Yeah yeah...I remember you now...lol.

Last night I was drunk...you should see the stupid crap I bid on at ebay...

Anyways...my bias isn't so much against X-pipes as cross-overs or H-pipes. I can see how they can be somewhat beneficial as they have some of the benefits of a collected system...which if you're going to entertain the idea of an X-pipe then you should go ahead with a completely collected system. However H-pipes do nothing but add a restriction in the exhaust. Some pressure tuning can be achieved with a crossover but there's not really any point.

I also think we worked out our differences on the whole backpressure thing on sf...lol.

rxspeed87

yeah that is part of the reason I did question you was hoping you would remember who I was

lol

eh I think who was right was still up in the air not sure but eh think it is close enough so who cares



icemark I thought the firing was 180*s off as far as dumping the exhuast,ignition or anything


**** I see what your saying and it is something I did miss and that is even though they open 180* off from one another both ports are always open
so if it was setup something more like the renesis motor with the side ports where the exhuast actually gets blocked off it might work a little better with an x-pipe


only thing can really think of is maybe the little dwell time because while both exhuast ports might be open they are still dumping at 180 degrees from one another so it os still a-b-a-b-a-b just they have a lot of overlap that hardly has any space in there


thanks for bringing that point up icemark

efi12a

I'm using a Spintech XL in conjunction with an RB presilencer and a large diameter/very short "resonator" originally meant for a Grand Marquis. The resonator is between the presilencer and the Spintech. I'm happy with this combo. It's deep toned, none of that "bees in a can" stuff. That said, without the resonator, it's a whole 'nother story, unacceptably loud and high pitched. For that matter, I've tried different combos of these components and this is the only setup that I'm 100% pleased with. The resonator does take 7hp (167 vs 160) but I've made it easily removable via flanging it's installation so it's easily replaced with a straight pipe in 5 minutes.

-Mike R.