81 400xs turbo build

Ok i see the design of the pump is totally different..... too bad.
We must remember that pressure and volume are completely unrelated. You can have a teeny displacement pump put out thousands of psi pressure with minimal flow.
Having a higher operating pressure only means there is more restriction to flow.:bike:
 
So tried a test fire today... It runs.... Turbo spins nicely I think I lucked out with sizing.... Did not check boost pressure because I have copper donut rings for the exhaust and don't wanna torque them down until the project is more complete.

The bad.... Despite having a restricter in the oil feed, the return line is not big enough as I kind of expected so will have to increase return line. You know the return isn't big enough when engine oil is weeping out the turbo after running for a minute or so. So for now old smoky is gonna have to wait for me to get a fatter return line made.
 
Yeah when I used to play with the journal bearing turbos on my cars back in the day, the supply line was -3an with a restrictor, and the return line was -10an!!!! Only way to get them to not spew out the seal at redline with 60+psi
 
So swapped out the 1/4" brake line for 3/8" fuel line and installed larger fittings and Presto!......no oil leaking through turbo!

Another surprise is that the fuel system seemed to be keeping up to the boost in neutral however this will probably change under load when on an actual road.... Unfortunately there is snow and a few miles of gravel in order for me to hit pavement so I will be tidying up loose ends until I can get on the road! But looking very promising!!!
 
You may be able to make a copper return line. Using like 3/8" tubing. That should be enough perhaps.... you may even find fittings kicking around my shop... and flare and bend it up like your originals!
 
Turbo's don't produce boost unless under load(unless you have the timing uber retarded and are burning fuel in the turbo). If you are just running the bike stationary on the stand you are just pulling from the pilot jet mainly. Won't know what is actually going on with boost or the main jet circuit until you get on a dyno or on the road.
 
Down pipe done..... I'm sure the cops are looking forward to meeting me in my small town. Something tells me those meetings will be less enjoyed by me though.

Here are a couple pics to wet your whistle....
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Well, the turbo itself is actually a really good muffler so you will actually be quieter than guys with straight pipes. But when the wastegate opens...should be fun :)
 
Great to see one of these projects coming together! Looking forward to hearing about how it runs.
 
In order to put your bike under load simply put front wheel against immovable object straddle bike in first gear and apply throttle whilst letting out clutch!:yikes:

I see you got your o2 sensor in..... any preliminary readings?
 
So I finally took it for a real drive today.....the beast is totally alive and well in this bike!!! Makes nice boost but to scared to look at gauge to see actual psi (gravel road lol). But ultimately it will begin to sputter and slowly run out of fuel....which is crazy because the stock gravity fed system kind of keeps up for quite some time. I am going to try a small inline fuel pump before going nuts on the full blown fuel system with the regulator and returns and what not.
But for anyone wondering......yes.....it is incredibly fun to ride when the boost comes on. It feels like I am hitting an extra gear between every shift!!!

Note...turbosmart adjustable bov is not soft enough....getting compressor surge on dump.
 
Awesome! :thumbsup:

Just a thought, not sure how it'd work with the regulator, but the carbs can be tapped and drilled on the other side of the bike too.
Might need a second petcock, or a different single one with more flow, but with two lines feeding the carbs you could probably double the fuel flow.
 
Awesome! :thumbsup:

Just a thought, not sure how it'd work with the regulator, but the carbs can be tapped and drilled on the other side of the bike too.
Might need a second petcock, or a different single one with more flow, but with two lines feeding the carbs you could probably double the fuel flow.
I discussed doing that with a neighbor this morning actually, but figured an inline pump would be easier than tapping holes and adding a petcock. Although we didn't even think about a petcock with more flow....probably try this if inline pump pushes fuel through carb.
 
When under boost, the fuel can actually be pushed back up the fuel line. A fuel pump and a rising rate pressure regulator is needed to maintain a positive relative fuel pressure at the needle and seat. Very little relative pressure is required, probably 1 or 2 PSI above boost pressure would be enough. As long as the fuel pressure is higher than the boost pressure. This is another downside of a blow through setup.

I'd be inclined to install the pressure regulator on the opposite carb so that the fuel has to go through both carbs before being returned to the tank. This will help prevent vapour lock issues.
 
So I tried a couple different inline fuel pumps. A 5-9 psi pump will push through the carb. A 2.5-4 psi does not pressure through, however it starves even quicker than with no pump at all. I wouldn't mind tapping another line to double the fuel volume....I think it would be enough because I ran a fatter fuel line and it nearly keeps up but like mentioned it will push fuel back when under boost.

I have a boost referenced regulator that I ordered for this thing a while back but unfortunately it does not have a return to tank line so a brain fart on my behalf cause it's for fuel injection only system.

Do any of you guys have a burning passion to see if 2 fuel lines will work.....if so I will try it for anyone that wants to know or wants to build a similar project on a cheaper budget. If not I will continue with fuel pump and regulator.
 
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