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Thread: where's the tune in tuner
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04-13-2008, 09:19 PM #61
bleeding off too much pipe pressure doesnt hurt bottom end (actually overall performance)?
I cant really say the stinger is too big anyways, considering i don't know the sizes. Just kind of going by the "look" of it...> Stainless steel Merc cowling plates - $110 shipped TYD - LINK <
1979 16' Action Marine/2.5L Merc S3000 - Metalflake Maniac
1984 18' Contender Tunnel/2.4 Merc Bridgeport
"Where does the love of God go, when the waves turn the minutes to hours?"
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04-13-2008, 09:19 PM #62
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04-13-2008, 09:28 PM #63
havent looked at the book for a long time. wish I had a copy to scan into PDF.
> Stainless steel Merc cowling plates - $110 shipped TYD - LINK <
1979 16' Action Marine/2.5L Merc S3000 - Metalflake Maniac
1984 18' Contender Tunnel/2.4 Merc Bridgeport
"Where does the love of God go, when the waves turn the minutes to hours?"
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04-13-2008, 09:29 PM #64
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04-13-2008, 09:33 PM #65
Expansion chambers don't work by heat, they work by controlling sonic waves. A hotter pipe causes faster sound waves and make the pipe work at higher rpm, the opposite of what you suggest. Stingers that are too small do cause motors to over heat, because they cause excessive pressure and reduced flow.
A stinger with too large diameter is just going to be less effective at the tuned rpm, not much effect below the tuned rpm ... that is one of the problems with fixed timing pipes (fixed length or non water injected)
Some successful alkie and mod racers with sliding length pipes also include a vented section on the front end of their header (lead in pipe) ahead of the main sliding part of the pipe. This is to take the pipe completely off line while getting over plane leaving the pits and getting the prop to hook up.
There is a pirate that has the book online as a pdf. You can find the link to it on some of the posts about books.Last edited by Mark75H; 04-13-2008 at 09:35 PM.
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04-13-2008, 09:35 PM #66
I just found the pdf of it... a little dirty but it'll work.
> Stainless steel Merc cowling plates - $110 shipped TYD - LINK <
1979 16' Action Marine/2.5L Merc S3000 - Metalflake Maniac
1984 18' Contender Tunnel/2.4 Merc Bridgeport
"Where does the love of God go, when the waves turn the minutes to hours?"
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04-13-2008, 10:02 PM #67
We used to use tighter stingers on some of our drag sleds to build pipe heat at the starting line. Cold pipes KILL performance...but this is all in the VERY short run. The factory 2smoke guys now use retarded ignition timing on the warm up stand to extend the flame front into the pipe to build heat...
I'm no pipe designer...I just use 'em lol.'08 SRV
Yamaha 3.1 Phase III
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04-13-2008, 10:17 PM #68
The idea behind the stinger being a certain size is also related to the exhaust gas flow. when the gas expands in the pipe it cools down, and cooler gasses don't flow as well. Like was stated, theres a happy medium in it.
> Stainless steel Merc cowling plates - $110 shipped TYD - LINK <
1979 16' Action Marine/2.5L Merc S3000 - Metalflake Maniac
1984 18' Contender Tunnel/2.4 Merc Bridgeport
"Where does the love of God go, when the waves turn the minutes to hours?"
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04-13-2008, 10:26 PM #695000 RPM
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I can never seem to jump into the thread in-time .. and i dont want to stall it from moving along.. but yes i was really refering to the stinger , but in referance to the length that extends into the the cone...believe it or not ,, ive toyed with some "home grown crazy-ness" and had killer resalts as far as where it "comes on the pipe" or comes into tune..now i gotta be honest i dident have access to a dyno ,, but my conclusions came from how it felt and at what rpm it started to pull...
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04-14-2008, 06:03 AM #70
Jennings' explanation of the stinger is to think of it as a "bleed resistor" to keep the pressure in the pipe constant ... not really a temperature thing.
If decreasing the flow out of the sled pipes helped ... the stinger was just letting the pressure be too low; directly reducing cylinder pressure
The size of the stinger doesn't directly and primarily control temperature in the pipe
I don't think there is much in The Two Stroke Tuner's Handbook on flow after the lead in (header) section, nor anything on gas flow relating to temperature. If you find it any where in that book, another book or on the net, please quote it to me.
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04-14-2008, 06:06 AM #71
Jennings does talk about having the end of the stinger moved forward and getting good results, so I'm not surprised you had good results. I'm also not surprised that tinkering helped, things have to be exactly right and power band and driver's technique are like shoes ... no two are alike and everyone has a different preference.
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11-14-2021, 10:06 AM #72
V 8 with expansion pipes.
Hi I finally found a thread on here about pipes - Its an old thread but hope you see it and can answer some questions.
I built a race car fitted with an Evinrude V8 plus a CVT transmission. However I retained the original exhaust with tuner but had to add a silencer(Muffler) to get down to 108 db allowing me to race. It works but restricts the power due to too much back pressure.
I am now cutting away the exhaust manifold to create 8 ports for me to fit 8 pipes. As I need to instal the power head with exhaust on top, I am also fitting EFI with an air inlet plenum and two large throttle bodies which I can position out of the floor level dirty area.
I attach pics of my present setup withe 8 Mikuni Super BN carbs plus an ignition system I made. There is also pics of a V8 converted by Rude in Sweden plus a Spanish V6 with pipes.
It can be done.
??????????? Has anybody else tried this since Lentzkow tried it many years ago?
I have recently built a 3 cylinder Rotax powered race car with 3 pipes. By extending the stinger into the centre of the belly section, the noise level is measured at 104db , without any muffler!
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11-19-2021, 09:18 PM #73
Cool old thread you resurrected, was an enjoyable read.
You're pretty much blazing your own trail here except for the relation to the Swedish car you speak of and the Spanish car you posted photo of above.
Lentzkow was fighting a different battle than you are as he only had one gear where you have infinite gears with your CVT, therefore you don't have to wait forever to get "on the pipe" as he did so long as your CVT tuning skills are up to snuff.
I'm assuming you have the Springs out of your clutches in the second photo you posted?04 XR 2001 RR/2.5
94 XS 2003 GSE/00 Promax
87 Vegas XT
87 Wellcraft 23 Nova XL
86 Wellcraft 3400 Gran Sport
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11-20-2021, 09:55 AM #74
Anyone who has heard / seen a 1973 Honda Elsinore explode out of a corner at low RPM , in a gear too high has to realize that the lie about "expansion chambers make no torque" is dead.
It's only been 48 years .. A little longer if you were into Maico's and Husky's ..
Jennings did say that the head pipe and divergent cone had the most influence on the torque curve .. which is what we have with outboard motors ..
http://www.bridgestonemotorcycle.com...ou_really6.pdf
Only part of the picture , but when your dealt lemons, make lemonade ...
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11-20-2021, 12:53 PM #75Member
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Talk about a serious trip down Memory lane with all these Posts
The Elsinores were Some Fun and Beyond ,Still remember the corner power and wheel coming up on exit.
Nothing compared to the later 500cc two strokes back in the day ,that was a test of Talent buy the manufactures.
The Pipe article has so much merit.
Feeling a bit Dated now Folks.
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