281 replies to this topic

[Captain Midnight TT Gold Member]

lateapex31 said:

how will you handle ignition timing?  Increased cylinder pressures call for reduced ignition timing, not the 30+* all in by 3k RPMs of the factory CDI box.  It's not even close!  While I applaud your creativity I think you may need to put some more effort into engine management.

I have a progamable ignition that will work for you.

[pablo83 TT Silver Member]

Captain Midnight said:

I have a progamable ignition that will work for you.

Programmable ignitions, BOVs, aftermarket carbs/EFI, and all that other stuff will have to come after I've put the initial system together.  This is going to be a budget build.  It's just for fun, not serious competition.

I have an XR650L parts bike that will provide me with a backup engine which I'll need when I run the boost up to 20 psi on pump gas and no ignition retard

Uncle Bob, thanks for keep such good notes on your turbo build.  I'm half way thru the thread right now and I've learned a lot.  I'm getting worried about my carb.  Since the bike was street legal from the factory, the carb is horribly un-adjustable.  I'm still going to start with the stock carb, but I think it may not last long.

[UncleBob TT Silver Member]

pablo83 said:

Uncle Bob, thanks for keep such good notes on your turbo build.  I'm half way thru the thread right now and I've learned a lot.  I'm getting worried about my carb.  Since the bike was street legal from the factory, the carb is horribly un-adjustable.  I'm still going to start with the stock carb, but I think it may not last long.

What is the stock carb for the NX?  Sorry for not knowing off the top of my head.....

MOST carbs are doable with a turbo with nearly no adjustment.  95% of the time, the only thing you're adjusting is the main jet if you are using a pitot tube properly (blow thru only).  There are a few exceptions, but not many.

The turbo thread is painfully long, no doubt.  If you have any questions...shoot.

And your low-cost goals are very doable.  I agree completely with you.  Although I went with an adjustable ignition box, fiddled with the compression ratio, cams, etc, it is fine tuning that isn't all that productive over what you can achieve with the bare bones setup.  It is mostly minor tinkering IMO.  Don't for a second think that you need to invest a huge amount into this to make a reliable, very potent machine.  It just takes the right starting point, the right attitude, and the right tuning.  

IMO, the hardest part is finding the INFO!  There is so little out there, even in this day and age, with the wonders of the internet.  No reason to reinvent the wheel, when it has been reinvented 20 times over.

[pablo83 TT Silver Member]

UncleBob said:

What is the stock carb for the NX?  Sorry for not knowing off the top of my head.....

MOST carbs are doable with a turbo with nearly no adjustment.  95% of the time, the only thing you're adjusting is the main jet if you are using a pitot tube properly (blow thru only).  There are a few exceptions, but not many.

The turbo thread is painfully long, no doubt.  If you have any questions...shoot.

And your low-cost goals are very doable.  I agree completely with you.  Although I went with an adjustable ignition box, fiddled with the compression ratio, cams, etc, it is fine tuning that isn't all that productive over what you can achieve with the bare bones setup.  It is mostly minor tinkering IMO.  Don't for a second think that you need to invest a huge amount into this to make a reliable, very potent machine.  It just takes the right starting point, the right attitude, and the right tuning.  

IMO, the hardest part is finding the INFO!  There is so little out there, even in this day and age, with the wonders of the internet.  No reason to reinvent the wheel, when it has been reinvented 20 times over.

The NX uses a Keihin.  I have the backup motor which also has a keihin of a slightly different model.  There's a casting number on the side that begins with VE and is proceeded by a stamped number that's slightly different between the NX and XR carbs.  How do I identify the exact model carb?

[UncleBob TT Silver Member]

pablo83 said:

The NX uses a Keihin.  I have the backup motor which also has a keihin of a slightly different model.  There's a casting number on the side that begins with VE and is proceeded by a stamped number that's slightly different between the NX and XR carbs.  How do I identify the exact model carb?

After I posted it, I looked it up.  It is a CVK40, which is the same carb they use on the KLR650.   I actually used this same carb briefly on the DRZ

You'll have no problems at all.  IMO, one of the better carbs for turbo'ing

[pablo83 TT Silver Member]

UncleBob said:

After I posted it, I looked it up.  It is a CVK40, which is the same carb they use on the KLR650.   I actually used this same carb briefly on the DRZ

You'll have no problems at all.  IMO, one of the better carbs for turbo'ing

Thanks.  I know you fiddled with a lot of needles and jets. what do you think I should start with  on this carb with 8psi boost?  Also, what kind of fittings did you use to make your pitot tube?

[UncleBob TT Silver Member]

pablo83 said:

Thanks.  I know you fiddled with a lot of needles and jets. what do you think I should start with  on this carb with 8psi boost?  Also, what kind of fittings did you use to make your pitot tube?

all of my early efforts with the turbo system were a waste of time because I didn't have the magic secret:  air box size.  Without that, you'll never get it to run right

With the right air box and pitot tube, the carb will be dead stock, other than the main jet (which will probably be close to stock size)

I don't use any fittings for the pitot, Just a rubber hose connecting the pitot tube to the vent tube

[pablo83 TT Silver Member]

UncleBob said:

all of my early efforts with the turbo system were a waste of time because I didn't have the magic secret:  air box size.  Without that, you'll never get it to run right

With the right air box and pitot tube, the carb will be dead stock, other than the main jet (which will probably be close to stock size)

I don't use any fittings for the pitot, Just a rubber hose connecting the pitot tube to the vent tube

Do you make the pitot tube or is it commercially available?

[lateapex31 TT Bronze Member]

Captain Midnight said:

I have a progamable ignition that will work for you.

I've got a Microsquirt with plans to EFI the XR this year   I do this stuff for work   If anyone in the Northeast needs some dyno time, let me know, located just outside of Boston.  We have a 4WD car dyno but it runs bikes just fine!

[Captain Midnight TT Gold Member]

pablo83 said:

Programmable ignitions and all that other stuff will have to come after I've put the initial system together.  This is going to be a budget build.  I'll need when I run the boost up to 20 psi on pump gas and no ignition retard

Megajolt programable ignition is $84.00.

[PorterzCustomz TT Bronze Member]

Are you going to run some type of innercooler or is it just going to be hot piped? You could probably make a mini water innercooler.

[DRX350 TT Gold Member]

No sense in an intercooler if you're running 1bar or less, especially with an air cooler motor.
On an NX, an air cooled turbo set up would work fine.

[lateapex31 TT Bronze Member]

DRX350 said:

No sense in an intercooler if you're running 1bar or less, especially with an air cooler motor.
On an NX, an air cooled turbo set up would work fine.

By that logic Porsche shouldn't have bothered upgrading the 911 turbo to intercooled after just a few years.

Captain Midnight said:

Megajolt programable ignition is $84.00.

Are you going to use EDIS or is there another way to configure the MJ?

[DRX350 TT Gold Member]

lateapex31 said:

By that logic Porsche shouldn't have bothered upgrading the 911 turbo to intercooled after just a few years.

I meant to say for A/C motorcycle applications.  Besides, that's a lot of extra plumbing.

[pablo83 TT Silver Member]

Captain Midnight said:

Megajolt programable ignition is $84.00.

That's pretty cheap.  I may be into it farther down the line.  What type of trigger is required?  Will the stock one work?

[pablo83 TT Silver Member]

PorterzCustomz said:

Are you going to run some type of innercooler or is it just going to be hot piped? You could probably make a mini water innercooler.

Yes, the plan is to have air/air innercoolers.  I plan on mounting two small innercoolers where the radiators would normally go.  This will require a pipe connecting the two over the top of the tank.  It may look silly, we'll see.  Plumbing shouldn't be too big of an issue since the turbo will sit right below the coolers.  

This will significantly cut into the fuel tank size, so I'll add an aux fuel tank under the seat where a muffler would go.  The NX ran dual mufflers but the turbo will bring it down to 1.  It does not matter if this tank is below the carb since I'll be using a fuel pump anyway.  I know having two coolers will not be best for airflow or pressure drop, but I'm slightly worried about heat since the engine is air cooled.  I also have a nice oil cooler from a CBR600F.

[cleonard I ride therefore I am.]

Don't know if you plan to ride your creation off road.  A turbo is considered a valid spark arrestor so you don't need to concern yourself about retaining a legal sparky with your sure to be custom exhaust system.

[dubkatz TT Silver Member]

cleonard said:

Don't know if you plan to ride your creation off road.  A turbo is considered a valid spark arrestor so you don't need to concern yourself about retaining a legal sparky with your sure to be custom exhaust system.

Plus turbo's dont like any back pressure so you can go as free flowing as possible.

[pablo83 TT Silver Member]

cleonard said:

Don't know if you plan to ride your creation off road.  A turbo is considered a valid spark arrestor so you don't need to concern yourself about retaining a legal sparky with your sure to be custom exhaust system.

Thanks for the tip.  I was wondering about that.  I'll have a muffler, but no spark arrestor and I do plan on riding in national forest.  But I'll probably have to find some official documentation on this because there's no way the forest service rangers will believe me on this.

[cleonard I ride therefore I am.]

pablo83 said:

Thanks for the tip.  I was wondering about that.  I'll have a muffler, but no spark arrestor and I do plan on riding in national forest.  But I'll probably have to find some official documentation on this because there's no way the forest service rangers will believe me on this.

It's in the forest service Spark Arrester Guide.  This is the publication that has every approved spark arrestor in it.  You are right that no ranger will know this so print out those few pages you need and carry them.  It's here http://www.fs.fed.us...OHV_SAG2007.pdf  The page requires a username and password.  Both are t-d

From this document on the 17th page from the begioning

Quote

Turbochargers qualify as effective spark arresters when 100
percent of the exhaust gases pass through the turbine wheel.
The turbine wheel must be turning at all times and there
must be no exhaust bypass to the atmosphere. Depending on
design, small enclosed system bypasses that reroute some
of the exhaust back through the engine may be allowed. The
illustration of the exhaust-driven turbocharger shows the air
intake and the exhaust path through the turbine wheel. The
action of the rotating turbine wheel causes carbon particles
to remain within the confines of the turbo-drive section until
they are reduced to a harmless size by attrition.