Sizing carb and jets for turbo application

[Saml01]

I have decided to pursue a new project. Always wanted to learn to weld and have a turbocharged bike. Got the bike and always wanted to learn to weld.

The big question is, how do I determine what size carb and jets I need for a draw through turbo on a stock motor? I know almost everything about EFI but my carb knowledge is seriously lacking.

I know I need a larger diameter throat on the carb. But how do I know how big? I assume at least as big as the inlet on the carb so it doesnt restrict. But I don't think thats a very scientific determination.

Other part of the problem is determining the jet sizes.
How do I compensate for the additional air as boost increases? Is there a formula I can use to determine how large each of the jets need to be over stock? Due to the purely mechanical nature of carbs, I have a nagging thought they may not have to be bigger since the ratio of air/fuel stays the same just more of both gets crammed in the combustion chamber.

Thank you in advance for any advice.

 

[KJShover]

Drop $3k on thier universal system and all your left to do is weld up your manifolds and such.

http://mrturbo.com/turbo-sys/turbo_sys.html

Good people to deal with, A ton of help with thier systems. I ran one of thier racing systems years ago. I also installed a kit on a friend's busa about 10 years ago. Still runs strong the last time I heard.

Almost 30 years in the biz and many records, you can't go wrong.

 

[[email protected]]

http://www.outlawdragbike.com/showthread.php?104-Mikuni-42mm-HSR-Carb-Settings-for-Turbocharging

This is what we are using in our turbo kits from gary.

From all the reading I've done, it seems that the general consensus is to use the mikuni hsr if you plan to hit the streets at all. It works well for track duty as well but adapts to street use easier than alternatives. I can't agree or disagree. I've never had a turbo bike and the only hsr I worked on was on a hopped up, but normally aspirated HD.

I hope you go for it.

You might want to shoot hubeerjw a message. He has a working knowledge of turboed maxes.

 

[hubeerjw]

My old kit came with an S&S Super B carb with a 100+ main jet... I'll do some digging and try to come up with the exact main jet... For the new turbo project I will try to come up with the main jet size for the Mikuni 42mm HSR carb that comes from Mr. Turbo. It would be pretty interesting to see if the diameter is much different between the two...

I really don't have a whole lot of turbo knowledge other than they are fun as hell, and the power is always there!

Jeff

Mikuni HSR Carb from Mr. Turbo:
The Mr. Turbo carb kit comes with the following:
Jet Needle - "8DDY1-95"
Needle and Seat - "2.3"
Pilot Jet - "35"
And it came with 3 main jets - 210, 220, and a 230

Check out this post: http://www.vmaxforum.net/showpost.php?p=108886&postcount=1
Looks like the 0.096 was the best jet I used... I was always told to run on the rich side with a turbo, so I bumped it up a little but it hurt me on the track. My A/F reading was safe with the 0.096, but I was told we didn't want to go any leaner.

Here is another interesting link: http://vmaxoutlaw.com/tech/dyno-mikuni.htm
and.... http://www.mikuni.com/tg_main_jet_size.html
and... http://www.nightrider.com/biketech/hdcarb_S&S_jetting.htm


I hope this helps.

Jeff

 

[Saml01]

Drop $3k on thier universal system and all your left to do is weld up your manifolds and such.

http://mrturbo.com/turbo-sys/turbo_sys.html

Good people to deal with, A ton of help with thier systems. I ran one of thier racing systems years ago. I also installed a kit on a friend's busa about 10 years ago. Still runs strong the last time I heard.

Almost 30 years in the biz and many records, you can't go wrong.

The system looks pretty complete but id like to know exactly what parts are included. For example the brand of turbo and wastegate.

 

[Saml01]

hubeerjw,

That is some EXCELLENT information. The parameters on that carb are an excellent place to start, especially since Mr Turbo says they size the carbs to the applications. Its next to impossible for the average man to figure out carb jet sizing.

 

[Saml01]

http://www.outlawdragbike.com/showthread.php?104-Mikuni-42mm-HSR-Carb-Settings-for-Turbocharging

This is what we are using in our turbo kits from gary.

From all the reading I've done, it seems that the general consensus is to use the mikuni hsr if you plan to hit the streets at all. It works well for track duty as well but adapts to street use easier than alternatives. I can't agree or disagree. I've never had a turbo bike and the only hsr I worked on was on a hopped up, but normally aspirated HD.

I hope you go for it.

You might want to shoot hubeerjw a message. He has a working knowledge of turboed maxes.

Who is "we" and Who is "Gary"?

I really want to do it, just need to figure out a few things first, namely the turbo sizing.

 

[[email protected]]

http://www.vmaxforum.net/showthread.php?t=10528

 

[Saml01]

http://www.vmaxforum.net/showthread.php?t=10528

Fantaaaaaaastic. Just read this whole thread.

Question.

Any idea what wall thickness I want to use for the hot side plumbing?

Any idea where I can get the exhaust and intake flanges? I know I can cut it off the stock stuff, but thats not ideal.

 

[[email protected]]

Not sure how to help you with those questions.

There is a book mentioned in that thread. Author was Corky Bell. Satriel666 posted a link to download it. That may be useful as far as design goes.

Not sure where you could buy flanges. Our intake flanges are made. No exhaust ones yet. At least that I know of.

 

[Saml01]

I read Corkys book when I got into Turbo Miatas. Its one of those must reads for anyone getting into forced induction.

Those are some nice intake flanges. Looks like aluminum. Are they for sale separately?

If I cant figure out how to get flanges or decide against cutting them off the vboost manifold I may just get a euro manifold and just build a collector on top of it. Problem solved.

I have some ideas for the hot side plumbing already, just need to draw it and see if the flanges I want are readily available.

HubeerJw, You got any pics of your setup? I found some of your videos on youtube. I love the idea for a square plenum, I was thinking to do the same but discarded the idea because I thought it would impede flow. Apparently not . Did you swage fit your hot side pipes so you can take the system off? Where are you sourcing the oil feed from if not from the oil port under the water pump?

 

[[email protected]]

Check out this thread for some pics of hubeerjw's turbo setup
http://www.vmaxforum.net/showthread.php?t=5785

 

[Saml01]

Check out this thread for some pics of hubeerjw's turbo setup
http://www.vmaxforum.net/showthread.php?t=5785

SO AWESOME!!!!!!!!!!

I like the location for the oil feed. There is a picture in the thread that shows a nylon hose connected to the banjo, how was that port created?
The idea to weld a barb on top of the banjo is a nice idea, I was also thinking about using double banjos, stacking one with a barb.

The intake plenum seems to have a few barbs whose purpose I cannot identify, nitrous ports maybe?

I love how the oil drain was designed. I right into the clutch cover. BRILLIANT!!!

Where did you get the flanges for the exhaust and intake on that setup? I love the fact that the entire system can be slid off the engine due and swaging one pipe was genius.

Huberjw, what kinda of turbo are you guys running and at what RPM do you reach full boost? Looks like T3/T04.
I am not sure how big of a turbo to get because I have no parameters on the engine. Anyone know the VE and BSFC?

I am thinking of using an internally gated T25/T28 turbo to keep costs down and save fab time. But it might be small.

 

[hubeerjw]

I purchased this as a used setup. Mad Max was the creator of the system. I'm not exactly what the turbo was off of (there is no tag on it), the intake had AN fittings for NOS was was in a seperate chamber that cooled the compressed air before going into the engine. I'll dig up the specs on the Comp Turbos we recently purchased. Feel free to send me a PM and I can send you my phone number if you want to talk in a little more detail.

Jeff