175 Exhaust Designs

Came across this design for a 175 Exhaust I did, it worked ok with a 35mm carb, B10EGV plug and ignition timing set to 1mm BTDC.

Cant find all the notes but think it was based on 9500 rpm

Hi James,


Was this with a pvl ignition?



Eddie

Ed,

Yes PVL ignition, Pump fuel (Shell Optimax now V-power) Castrol TTS at 20:1 mix Compression Ratio around 9.75:1

James

Hi James,


thanks for that and the added info, much appreciated.



Eddie

James,

Interesting design, with shallower tapers on second and third parts. Presumably that would spread torque to lower rpm ?

I am looking for a decent pipe for my 175 (cast iron barrel, with smaller ports) E = 176 degrees.

What Exhaust port timing were you using this with ?

john the first thing I would do is sort out your exhaust port timing, ?

what rev's do you want to do, ?

Edward Pickering I have found the offical data set up sheets and break down for amal MK11 I will try and post it to here for you, or pass it to my dad you can then collect it or PM me you email I will scan it and eamil the it

but basically it says
type
bore size MAIN NEEDLE JET NEEDLE POSITION THROTTLE SIDE PILOT JET AIR JET
2034 320 .107 3 3 25 2.5
2036
2038 400 .108 SAME

regards Derek

Hi Derek,


Will pm you the email adresses but as you say will be good to be on here too.



Eddie

johnSbantam wrote:

James,

Interesting design, with shallower tapers on second and third parts. Presumably that would spread torque to lower rpm ?

I am looking for a decent pipe for my 175 (cast iron barrel, with smaller ports) E = 176 degrees.

What Exhaust port timing were you using this with ?

John,

Exhaust timing was 180 to start and I moved it to 182 with this pipe if memory serves me correctly

James

Thanks James,

So it would be a good pipe for an alloy barreled 175.
Such as my 4 speed weapon / project.


In the meantime I am stuck with the biggest E hole I can get in iron barrel and longest timing (without have ring drop in inlet, or expose top of piston in inlet at BDC) with 1mm spacer underneath.

Hi John

Todd's Bantam reved to 10,500 and only had an exhaust port height of 22m, he could out perform bost 5 speed box bikes of that erra and did 110mph, if we are to believe the MCN that is. anyway I dont believe you need the biggest ports, as often shape and direction is just as important, besides I believe Peter Tibbets sleeves his exhaust port down to I think 32mm. !

The latest RS is only has an exhaust port height of 23.5mm.

so you dont just need big holes, JUST as big a volume as possble "see the Trevor Amos posts" ?.


regards Derek

I agree about the physics of gas flow. I know, I have a small rectum and a tight sphincter and I can pass gas at high flow rates easily !!!!

But, no pun intended; One simulated Computer designed system and current (short version of your "Sprinter" system) to formula lengths do not work very well with the porting I have. The tinny 1970s pipe on my 125 longstroke only produces 12Hp but is very easy to ride and helps me get good lap times.
My 175 is a pig to ride compared to others. Despite a lot of expert help.

So was just wondering if anyone had any old designs for an iron 175 ?
Some pipes have 600+ long first part others 400ish, defies logic.

Good Evening,


Is there a thickness and type of metal that most people use to build these exhasts?




Eddie

Good Morning,


Any tips/advice on how to bend/roll the sections to be made for exhausts.



Eddie

Hi Edward,
There is some advice and plenty of pictures on the main web site under the Bikes Section and the go to Bantam Racer articles. This should help! but I will give you some advice and assistance if you struggle!
Cheers,
Alan

Hi James ,is the first number from piston face or barrel stub cheers Andy C

James do you have a note of the diameters for your above mentioned 175 pipe ?

Theoretically, it could suit my iron barrelled 175.

cheers

john

AlanB,

The diagram you kindly sent me of the 2002 Moulden "wonder" pipe, was that intended for a longstroke 175 or a short stroke 125 ?

Ta

JohnS 8{)}

Second glance, of course the numbers are there !

If you were to run AvGas, would you have a higher CR and more advanced timing ?

Any fuel above 100octane allows for advance of ign timing purely by the attribute of these high octane fuels being anti-knock and anti-inaudible/audible detonation.
Particularly methanol (which Mike hates) is so cool and slow burning that the peak combustion pressure is very low at the beginning of combustion and then spreads over a greater number of degrees, after TDC, than when using 98octane petrol for example. That is providing the fuel-air is always RICH. Hence one can use a higher compression-ratio and gain more thermal efiiciency... Where, about 10:1 compression ratio is the limit for a 95-98 octane petrol -- going to 16:1 C/R for a doped fuel is no problem. My speedway JAP 500 engine had a 16.5 C/R....

The latter -- inaudible detonation -- is the sneaky, illegitimate, too-early combustion (before TDC) that can put a hole thro´the piston crown without even making one little `Pinnnk´ sound.
What happens if you are too advanced with ordinary petrol of around 95octane is that the early combustion (before TDC) goes to extremely high pressure -- thus opposing the piston´s upward travel (a loss to begin with...) -- at the same time increasing the combustion temperature such that it exceeds the melting point temperature of the piston crown which collapes into a hole. Usually the piston has expanded -- because of the high temperature -- and siezure happens at the same time. Andy Boyle´s ABS 250 did just that at my jinx circuit -- and I wept tears of blood that day because it was quicker than the Japanese bikes on the Norwich Straight in practice.

I apologise for this being Old Hat -- and stuff you know already -- but I thought it might help those who are newcomers to scene...

Ahhhmen! (Yaaawwwn!).

Hi John,
If you are running Avgas then I would run 3 degrees more advance as a starting point.
The 2002 pipe spreads the power out and depresses the overall Bhp, but the advantage is that you get the acceleration long before the top end power comes in! it was a major improvement on my lap times! It was by the way intended for a short stroke, but Andy did say it appeared to work well on any engine.
The pipe I have now is loosely based on this pipe after a lot of development work on the dyno.
Hope this helps
Alan

If any one is after a pipe building to there own spec I can sort you out have a look at my web site, and let me know what you think

Mick