Stinger question

[tz375]

Pedro,
I was working the midnight shift playing with pipe shapes and trying to match a set of pipes to particular porting combinations. I happened to have a brain fart and decided to measure a set of stock outer pipes and made a few assumptions on how to lie to the software about the "reverse cone". It wouldn't allow me to enter a flat plate which is how the gases see the baffle plates, so I had to enter a small cone to make it work.

Some hours of calculations with what seemed like every possible combination of pipes and ports, I realized that the Allspeed simulated power graph was very similar to a stock pipe. That surprised me, so I checked the dimensions and for all intents and purposes, Allspeeds are a stock pipe with the back end cut off and replaced with a proper reverse cone. Very similar header dimensions, same body and tapers.

I didn't see that one coming. I guess that Pete G knew where he got his dimensions, but how close they are to a stock L pipe surprised me. I guess that also explains why they make just a little more HP than stock but not a whole lot more.

Ah well. That was a great way to waste a perfectly good couple of evenings.

[Blokhead]

tz375,

Have you ever tried to design a pipe for a buffalo with TSR's pipe software? I had great luck with it on my dragbike, but I'm not sure how it will do on such a low performance motor as the GT.

You know, that really surprises me that the stock pipe with the proper baffle cone would not run better. I'm thinking of building a set of old school Denco style pipes for my GT, but only if I can come up with dimensions that have a reasonable chance of making more power everywhere, rather than just the peak. I suspect that this is what Jemco's do, especially since you have remarked about how short the tuned length is. Just by eye they look about the same as my H1 Denco's which probably peak around 8500, but for a mild street GT I think 6000 rpm might be better. An ignition with a retard function would then help sustain power on the over rev.

[Suzukidave]

Do you have any more pictures / details you could share about your drag bike ?

[Blokhead]

Do you have any more pictures / details you could share about your drag bike ?

Its got a 1998 Polaris XC700 Big Block (non power valve) twin snowmobile engine in a Kaw 650 frame. Stock bore, and stroke. Dynoed at Dynotech Research in Batavia New York. 162hp, 102 lbs./ft of torque. That dyno sheet cost me $600.00!!!!!!! Hearing that thing scream for 20 pulls made it worth every penny!

I've gone 9.68 @ 132 mph on it.

I also have a Utube video, but its not that great.

[Suzukidave]

OMG .. 162 HP @ 8300 rpm .. nice , now those are some fat pipes

[Blokhead]

OMG .. 162 HP @ 8300 rpm .. nice , now those are some fat pipes

Thanks.

Cylinders are only trail ported by Struthers of Carl's Cycle, although the carbs are 44mm Lectrons. V-Force II reeds. Heads are my own design, VERY tight squish, 14:1 comp. on 100 LL straight avgas mixed @ 26:1 with Yamalube 2S. Ran the best with the timing 4 deg.'s retarded from stock. I run an electric water pump with reverse flow (heads first).

[tz375]

Very nice. On the pipe question, Bill Tripp uses TSR and I use Bimotion and MOTA and I found that all three give different pipe designs. MOTA is typically the highest but not the widest, TSR, were good, but I got best results by tweaking the parameters in Bimotion and then simulating the results in MOTA. Of course that's all theoretical.

On the Stock pipes what I tried first was to simply add a cone after the stock pipe belly section and that made then too long. Unlike like most K models there is no cone inside (AFAIK). Then I tried to shorten the tuned length to better match stock or slightly modified porting and found that I could make a significant (theoretical ) improvement.

One of the great things about software is that it allows you to try things that in the real world might be extremely difficult or expensive to do and to see the effect. For example, it's not hard to exceed 150HP if you ignore the fact that it require ports to be where there is no metal to carve them. We craved on one block to find the limits and some were not what we expected, so that limits the shapes and sizes we can get without a lot of machining and welding.

And that's what makes Brett's achievements in Australia all the more remarkable. He just goes ahead and tries things and welds and cuts and repeats until he makes it work.

$600 for a dyno run They do have a nice facility from what I have read and getting BSFC figures helps too.

[Blokhead]

[$600 for a dyno run They do have a nice facility from what I have read and getting BSFC figures helps too.[/quote]

Actually I made 20 dyno runs that day, but that sheet was the final end result of tuning which cost $600.00 ($125/hr. X 4.8hrs.). Those pipes were, I should say, loosely based on TSR software. I had two sets of aftermarket pipes for my sled (LRM trail twins, and Hot Seat Perf.) The LRM's are highly regarded Polaris pipes. They were painstaking measured, and compared to TSR specs. The header, and diffuser sections were almost EXACTLY identical in diameter, and length for all 3 designs! Tuned length was VERY close. The differences were in center section length (dwell), and baffle cone angle. I went larger than all 3 on center diameter, and used the steepest bafle cone angle (TSR). Pipes were then made adjustable in length (center section), along with adj. stingers.



So, have you worked out a set of dimensions for a good GT street pipe that you'd be willing to share?

[Suzukidave]

Here are the specs for the chambers i am running on my project bike

[diamondj]

Sorry to slightly sidetrack the thread - what are you using as a transmission on your dragbike Blokhead? Belt drive from the Polaris' centrifugal clutch or did you actually mate up a transmission somehow?

Jim

[tz375]

Dave are those the same as the dimensions you sent me a while ago? If so you should find they work quite well .

[Suzukidave]

Dave are those the same as the dimensions you sent me a while ago? If so you should find they work quite well .

Yep .. these are the same specs that you ran for me before , my hopes are the reeds help the mid range and the chambers will pull out some top end .

[tz375]

Good. And that picture is to show us what we'll be seeing when that bike hits the road - massive wheelies everywhere.

[Blokhead]

Suzukidave,

Pipes look great. Do you know what rpm they peak at?

Sorry to slightly sidetrack the thread - what are you using as a transmission on your dragbike Blokhead? Belt drive from the Polaris' centrifugal clutch or did you actually mate up a transmission somehow?

Jim

I run the exact same setup as a sled. Primary is a Pol. P-85, and the secondary is an AC roller. The clutch cover has now been blocked off on the side.

[cor geraets]

This is more the idea of setup i was figureing to use but the longer stingers on Richards bikes do place the silencers at a more " sporty " looking spot .

Hallo that is a picture of a racing exhaust i build fore a Barton 500 cc 3 cylinder two stroke
Based on a 380 6 speed suzuki engine whit Barton cylinders it has about 90 hp
Nice too see some old work

Gr Cor
Samracing