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Old 08-02-2006, 10:00 PM   #1
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Default .12 tuned pipe questions...

hi all,

needed to ask some qns regarding .12 pipes.
they come with 5.2, 6 and 7mm stingers.
i know legal pipes are 5.2mm.
but do the 6 and 7mm ones really make much more power?
which one makes low end and which one is for high speed?

i also know that the manifold plays a part, but assuming all other things equal, what's the diff btw 5.2, 6 and 7mm pipes?
and what about those 'turbo' pipes? are they using larger stingers?

let's say i need not conform to regulations, what wld be a gd pipe for my OSspeed 12TZ?
i'm looking at OSspeed T-1040SC 6mm and ZAC kawahara 6mm.
sumone did mention to get the mugen P01002 pipe (legal pipe?) supposedly works well with 12TZ series.

currently i have a ZAC 7mm. shld i stick wif it or get one wif a smaller stinger?
thanks in advance!
and waiting for replies from the engine gurus out there...

Last edited by n.e.r.d; 08-02-2006 at 10:22 PM.
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Old 08-03-2006, 03:27 PM   #2
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I haven't triez the zac pipe but I know the Skyline works extremly well and should you choose to race a roar event its legal.

Mark
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Old 08-03-2006, 03:43 PM   #3
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thanks for the 1st reply mark!

i'm not really concerned the pipe being roar/efra/ifmar legal.
juz a local club racer from asia.

i was wondering if the different size of the stingers make any diff to the power output of the engine?

but like you mentioned, i might just try the skyline pipe with my 12tz.
btw, wat's the diff btw vr12 and vr12plus?
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Old 08-03-2006, 07:39 PM   #4
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Using common sense about a two stroke engine, more back pressure equals more torque and less back pressure more top end rpms. This is why a longer exhaust manifold will make more low end torque than a short, because it takes more force to push the gasses out of the exhaust. In turn you can apply this to the exhaust stinger. A larger diameter stinger will flow easier than a smaller diameter one so the larger will have more top end and the smaller will have more torque. Personally, I haven't experimented much with the stinger so, I can recommend one, and there are alot of factors thapt effect the ideal combination (engine, gearing, fuel, carb tuning, race course layout, driving style, etc.), so you'll have to try them out. I hope this helps and I gave you the right insight to help you make a decision.

Keith
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Old 08-03-2006, 07:48 PM   #5
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i used to run a 6mm stinger but now i just run a 5.2, the 6 did have more top end but i wonted more low end and now you can get diff manifolds to fine tune this. i use S,I,R pipes but i hear skyline are good.
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Old 08-03-2006, 07:56 PM   #6
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Quote:
Originally Posted by ksj44
Using common sense about a two stroke engine, more back pressure equals more torque and less back pressure more top end rpms. This is why a longer exhaust manifold will make more low end torque than a short, because it takes more force to push the gasses out of the exhaust. In turn you can apply this to the exhaust stinger. A larger diameter stinger will flow easier than a smaller diameter one so the larger will have more top end and the smaller will have more torque. Personally, I haven't experimented much with the stinger so, I can recommend one, and there are alot of factors thapt effect the ideal combination (engine, gearing, fuel, carb tuning, race course layout, driving style, etc.), so you'll have to try them out. I hope this helps and I gave you the right insight to help you make a decision.

Keith
Keith, you are only half correct.

More backpressure will give more TQ, but the longer manifold doesn't necessarily make more backpressure. However the longer manifold does increase the pipes tuned length. This is why longer manifolds make more TQ.

The ROAR legal stinger dia. is 5.0mm. The Outlaw pipe stingers are usually 5.2 or 6.0mm. The pipes with 6.0 stingers are usually designed for 5 port engines. The 7.0mm stinger pipes are designed for use with the small block .18 engines and such.

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Old 08-03-2006, 08:02 PM   #7
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oh ya sorry im running a 5mm stinger.
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Old 08-04-2006, 04:36 PM   #8
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thanks for the input guys!

mxwrench,
would it be okay to use a 6mm pipe with a 3port modded engine? (in my case, the OSspeed 12TZ).
or shld i stick with a 5.2mm?
cos you mentioned that 6mm are designed for 5port engines.

i prolly be getting the OS T-1040SC pipe, now deciding btw 5.2 or 6mm.
reason is that i think OS engines will work best with OS pipes.

used to try lots of pipe for my V-Spec (JP2, 063, 086...).
in the end the OS 2060 was the best combo. not to mention that it's the most durable pipe IMO.
(my MBX5 had a side-on impact. pipe bent inwards touching the fuel tank, pipe hanger totally out of shape but not a dent on the OS pipe. even the stinger was perfect! )
only complain was the anal way of attaching the pressure nipple to the pipe itself. why can't they do it just like everyone else?

lastly, juz a side note,
why does ROAR limit it to 5mm pipes? they're pretty rare in my part of the world.
JMRCA has a 5.2mm limit.
what about EFRA/IFMAR?
i think the only valid reason for these restrictions is to reduce power output of the engines.

again, it's been nice chatting wth you guys!
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Old 08-04-2006, 05:21 PM   #9
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All about Pipes

Header
The header's length has a significant impact on performance. The rule of thumb is that a longer header is better for bottom-end power, while a shorter header makes your engine scream on the top end. The longer it is, and it resonates at a lower pitch. The shorter it is, and it resonates at a higher pitch. The idea is to adjust the length until the engine and exhaust system are in sync and “singing” in harmony. You can’t go too far in either direction, so don't be reckless; you'll do more harm than good. The ideal header would also expand outward (conical shape). This subtle expansion, when combined with those of the tuned pipe, helps scavenge, or suck, the exhaust from the engine. The header length is the number you play with when tuning your pipe. A heavier car demands a broader power curve, so a longer header is best. A light car, on the other hand, can be tuned for peak power on a narrow power curve with a shorter header.

Divergent cone
·A sharper angle of the divergent cone makes scavenging more efficient but limits it to a more narrow rpm range.
·A more gradual divergent cone reduces the intensity of the negative wave, but it lasts much longer, so this increases the rpm range.

It's a balancing act of sorts: more performance over a limited rpm range or less performance over a broader rpm range.

Belly
Parallel portion of the pipe, that connects the divergent to the convergent cone. It's length determines the relation between the negative and positive waves.
·A short section is best for developing maximum power at high rpm ranges, but narrower power curve.
·A longer section implies in a broader power curve with less peak horsepower. Its more suited for developing low-rpm power.

Convergent cone
·A sharper angle of the convergent cone limits engine to a more narrow rpm range.
·A more gradual convergent cone increases the rpm range.

Stinger
The convergent cone ends at the stinger ( the pipe portion opened to atmosphere ) which expels the burned gases way out. It works as a pressure bleed valve and controls back-pressure, enhancing the port plugging efforts. If it is too small or too long, you may have engine overheating problems. Too small a stinger causes excessive back pressure into the pipe and raises the pipe and engine temperature.
The ideal stinger diameter should be .58 to .62 times the header diameter, and its length should be 2.86 to 3 times its own diameter.

Stinger diameter affects the top and bottom end.
·Bigger = top end at the sacrifice of low end torque.
·Smaller= low end at the sacrifice of high end revs.
Stinger length affects the top and bottom end.
·Shorter = top end at the sacrifice of low end torque.
·Longer = low end at the sacrifice of high end revs.

The stinger's ideal diameter and length are important to performance, but are limited and governed by most racing sanctioning bodies.

Tuned Pipes Design Examples
Small volume - narrow operating range (peaky)
High volume - lower power (if too big) - broad range
Steep angles - 'peaky' - high power
Shallow angles - broad range - moderate power
Shorter or larger diameter stinger - lower or higher pressures and heat.

How to Pick a Tuned Pipe·Torque biased. Sharp cone on each end long flat band center, single chamber.
·Low-mid biased. Aggressive divergent cone.
·Mid biased. Moderate divergent cone.
·Mid top end biased. Moderate divergent cone aggressive convergent cone.
·If the engine is a short rod rever you need a torquier pipe to enhance the bottom end as engine will be biased and take over on the top.
·If the engine is a long rod engine you need a rev pipe to help the engine unload on the top.

Pipe length
The way you intend to use your car in combination with your engine, will dictate the optimal length for the pipe.
The shorter the pipe, the higher the peak horsepower and torque, but the range of the horsepower and torque gets narrower and drops off faster. Also, the shorter the pipe the more fussy your engine will be.
·Shorter=top end at the sacrifice of low end torque.
·Longer=low end at the sacrifice of high end revs.

For optimum performance, the following guide may prove useful.

A) Overheating / Hot Weather
·Increase combustion chamber volume or head clearance.
·Increase stinger diameter or decrease stinger length (to reduce pipe pressure).
·Decrease nitro content of the fuel.

B) Cool Running / Cold Weather
·Decrease combustion chamber volume or head clearance.
·Decrease stinger diameter or increase stinger length.
·Increase nitro content of the fuel (if the competition rules allow).

C) Pipe Length Too Short
·Frequent blowing of glow plugs
·Sand blasted head
·Over heating engine
·Difficult to get 'on the pipe', sensitive needle
·Excessive carbonizing of the head
·Engine sags under load
·'Harsh' running

D) Pipe Length Too Long
·Very easy on the needles
·Smooth, quiet running
·Prone to burbling, rich running
·No power
·None of above, try shorter and see what happens.

AFM
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Old 08-04-2006, 05:41 PM   #10
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What part of the pipe is the divergent and convergent part on?

What would happen if you just had a megaphone for a pipe like motorcycles do?
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Old 08-04-2006, 06:34 PM   #11
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Quote:
Originally Posted by THE DOCTOR
What part of the pipe is the divergent and convergent part on?

What would happen if you just had a megaphone for a pipe like motorcycles do?
Divergent cone is the initial cone where the header attaches.
Convergent cone is the other end cone inside the pipe, which exits gases on the silencer chamber, to which the stinger attaches.

Megaphone is used on 4 stroke engine motorcycles. 2 stroke engines need both cones and belly because.........

Starting with the moment the engine fires, forcing the piston down and the exhaust port begins to open the cycle starts.
The exhaust gases are forced out of the engine and start to travel down the 'header' section of the pipe. Before long, the gas reaches the expanding / divergent / cone. The effect is a pressure drop, creating a vacuum which helps 'pull' the remaining exhaust gases out of the engine.
Not only are the exhaust gases being 'sucked' out of the engine, the fresh intake mixture is being 'drawn' into the combustion chamber from the crankcase via the transfer port. Some of this new charge will follow the exhaust gas straight through the still open exhaust port.
The exhaust gas travels down the pipe, through the expanding /divergent cone and the belly, till it meets the rear reflecting / converging cone.
The converging cone forces the pressure to rise, generating a pressure wave which reflects back towards the exhaust port.
As the reflected wave approaches the exhaust port, it forces the fresh mixture (which flowed through the combustion chamber), back into the combustion chamber. As the transfer port closes before the exhaust port this results in a pressurized charge in the combustion chamber as the exhaust port closes, - the result - more power.

AFM
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Old 08-05-2006, 04:53 PM   #12
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very detailed post on tuned pipes,
thanks afm!

think i'll be going with a 6mm OS pipe for OSspeed TZ.
guess it'll abit of compromise btw bottom and top-end.
see how it goes and will let you guys know...
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Old 08-05-2006, 08:28 PM   #13
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If you have a ding it the pipe, does it change the performance of the pipe?
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Old 08-05-2006, 08:39 PM   #14
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Quote:
Originally Posted by THE DOCTOR
If you have a ding it the pipe, does it change the performance of the pipe?
yes,and you can try to fix it by putting water in the pipe than plug the holes then put it in the freezer.it will be like putting a beer in the freezer but the dings will come out if your lucky.
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Old 08-05-2006, 08:53 PM   #15
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About the diameter of the stinger, I am pretty sure that the legal limit for 1/10th gas is 5.0mm and the 1/10th open it is 5.2mm. Anything above that isnt legal. I have run a 7.0mm pipe, and in my opinion it isnt worth it. It turns the car into more of a straightline car. Here are the rules on stinger inner diameter, I just found my roar book.

.12 roar/ifmar 5.0mm
.12 open 5.2mm
.15 roar/ifmar 5.2mm
.15 open 6.5mm
.21 open 8.0mm
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