turbo buell and harley exaust manifolding

[jayskind]

Turbo mounted to one exaust port on a harley engine with a 4 inch long pipe from one port and a 24 inch long pipe for the other cylinder.


I have found most of these so called tuning shops for an application I am building from scratch so loyal to profit that I dare not even ask them any questions on this.

I am building a turbo conversion using a new generic turbo bought on ebay with an o.e. styled boost curve translated :I mean a broad power band and whatever A/R ratio is for good broad toque for the 1.5liter engine it was developed for. I also have a custom turbo with different impeller A/R ratios.. that I will play with later.

I do not own a dyno shop and a few pulls to adjust air fuel ratios are all I can afford.

So Now I get to my friggin point: On a 45°harley motor with factory long overlap camshafts and high flow heads, is it better to to add a plenum chamber to the side of the shorter exaust pipe that is connected to the port the turbo is hanging off to similate more pipe length and volume as a tuning aid. If I did this I would not affect actual laminar flow much because the majority of the gas would travel by it because it is on the side of the pipe not in the middle.


My idea for the concept is a chamber to add volume, but not have the gas travel through it which would obiously affect veocity/pressure. I do not know if it is even necessary.

I do understand that as Hugh mcInnes points out in his book that a plenum chamber is absolutely necessary on the intake side of this engine due to its firing cadence, as the compressor could not feed the second cylinder so soon after the first got its charge without plenum area of at least one cylinder.

This engine is a 1200 cc engine that makes an honest 85 rwhp naturally asperated. I figure on roughly double that at 1 bar of boost using alcohol/water thru a draw thru system. S And S super E carburator. The engine will dump nitro methane thru an auxillary fuel circuit for extra power.

Of course packaging and asthetics are main reasons formy choices of the above

 

[patprimmer]

You will get the best response from the turbo by keeping the volume of the exhaust between the head and the turbo as low as possible while still retaining enough pipe dia to flow enough gas.

Do not use a large plenum on the exhaust, in fact, I would even keep the merge of the two pipes as close to possible to the turbo flange and neatly and compactly merged.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MikeHalloran]

Fitting such a plenum into the space on a motorcyle implies that it must have abrupt entry and exit transitions. Both produce surprisingly large increments of backpressure. Forget the plenum.



Mike Halloran
Pembroke Pines, FL, USA

 

[waross]

I have a question that may be pertinent. Given the firing patern of a Harley, is it important which cylinder has the long pipe and which one has the short pipe? I realize that it may not be possible to change the arrangement, but is there a significant difference one way or the other?
Thank you for your time
respectfully

 

[jayskind]

Reply to everyone thank you for answering my question. No plenum is necessary in exaust. Got it, and yes that is one less headache I have to worry about.

And to Waros: No the question you have is valid such as domestic v8s [sorry no approsprophe on my keyboard/spanish english thing). Who doesnt have fond meomories of bending the 1st and fifth cylinder together while avoiding the merged 3/7combination and steering gear, but in this case as there are two cylinders albeit in an unbalanced firing order prioritizing them isn{t actually doing that. I did however worry that the long short tube arrangement would cause surging in the turbine housing however everyone that answered this inquiry is saying the same thing: treat the turbo as a low pass filter and don[t worry about resonance. I guess that there won{t be much reverse resonace feedback to the second cylinder firing.

I cannot thank you guys enough for you response. Write me often you guys and gals
Jason

 

[waross]

Hi jayskind.

sorry no approsprophe on my keyboard/spanish english thing

Been there done that. I find the most confusing is one style of Spanish keyboard installed with the software mapped for the other style of Spanish keyboard. Try entering an E-mail address when you can't find the @ key and forget the code for it. Cut and paste time.
Thanks for the response.
respectfully

 

[patprimmer]

A little program built into windows, called "character map" will allow you to cut and paste many symbols not on the keyboard.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[waross]

Yes patprimmer
Things got a little easier when I found that table.
In my version of Windows 98SE it's at:
Start, Programs, Accessories, System Tools, Character Map.
On the lower righthand side it shows the "Alt." code for some but not all.
Thanks Pat
respectfully

 

[Craighell]

Hey Jayskind,

Not sure where you are, but I would love to work with you on the turbo system dyno tuning.

I have a small dyno room in NH and Buells are part of my interest (I own a modified M2 that I now call an M1W)

Good luck w/the project.

 

[jayskind]

Hi Craig I appreciate your offer, but the bike just moved to Costa Rica. The local Harley Dealer has never even seen one. I will however post copies of the dyno reports as I have a few guys down here that have them for cyles. Pass the word onto others I can get all the exaust plumbing custom made here cheap including stainless and cermacoat tubing.
Jason