Tag: Fuel Injection

The thinking, exploring, reading, and slow comprehension of how big and expensive this project is continues.  Lately I’ve been thinking about injector manifolds and throttle bodies.  I’ve also continued to think about longer intake runners.

Looking at where to put injectors into the engine for direct port injection, I could remove one of the two spark plugs and use the open spark plug hole to inject.  However, there’s probably a reason that Honda put two spark plugs in the engines.  I don’t think it would be wise for me to mess with that.

I could potentially drill into the intake header on the engine and install the fuel injector there.  However, I’m very leery of drilling into the engine.  I want to be able to reverse whatever I do if I screw it up.

To be on the safe side, I think I will get a couple of aluminum blocks, bore out the middle of them for airflow, and then drill and tap in holes for the injectors.  One thing I still don’t know about is if I need to have the injectors angled in a certain way or not.  Can they jut out at 90 degrees or do they need to be turned toward the valves?  Would it be better to have the injectors staring straight down the barrel of the intakes and have the air curve around to the side?

One person on the IPCRC suggested I switch from dual throttle bodies to a single throttle body.  Evidently many car engines ran on single throttle bodies.  However, several websites suggest (to me anyway) that it’s better to go with multiple throttle bodies because the rider will have more control and better response.  I think I will try to stick with two throttle bodies.  If possible, I’d like to reuse the ones in my carb.  Just have to figure out how to hack off all the extra bits of the carb I’m not using…

Intake runner length continues to kick around in the back of my mind.  A few conversations on the IPCRC got me thinking about it.  It seems like it could be a nice little power boost if I could actually figure out the correct runner lengths.  Perhaps I will setup the bike so I can change in and out different lengths of tube.  Once I get FI timing and whatnot down, then I can play with tube length.

A few good articles people have sent me:

Intake Manifold Tech: Runner Size Calculations

V-Max Fuel Injector Kit (including scary costing figures)

Engine Basics: Detonation and Pre-Ignition

A few other thoughts…

The Suzuki GSX1300R has nice fuel injector-equipped throttle bodies.  The Honda CBR600 also has fuel injected throttle bodies.  So does the CBR1000.  I wonder if perhaps I can find one of the proper diameter to drop onto my engine.  There certainly are enough sets of them for sale on EBay.  What sport bike, street bike, or cruiser has fuel injection, only two cylinders, and has in the range of 1000cc worth of displacement?

The amount of knowledge on the IPCRC is truly amazing.  A half dozen people know their stuff about fuel injection and are supplying a lot of great suggestions and pointers.  The thread is a wealth of knowledge for me.  If only I had more time to devote to this project at the moment.  In the next month I have a bunch of travel and work obligations that will take me away from converting my bike.  I’ll still get some things done but not as much as I want.  Maybe in the next month I can get some preliminary designs completed and make a parts list.

Looking at the NT-700 microfiche, the throttle body assembly (16400-MEW-L01) looks very promising.  It includes the throttle bodies and injectors in one unit.   There wouldn’t be any room to tune the volume between the throttle bodies and the valves though.  Someone on the IPCRC suggested I try to match the volume of the cylinder to the volume between the valves and the throttle bodies to help compress the air as it enters the engine.  I could also do that with a turbo or super charger, too.  However, it would be very difficult to tap the exhaust and there aren’t any belts to draw power from.    An air ram would almost be better although it would be a wee bit ridiculous to put an air ram on a PC.  Never say never though…

Anyway, if the angle of the cylinders is different between the NT-700 and the PC-800 (I suspect it is based upon other engine drawings), it won’t fit quite right. Also I suspect the throttle bodies are smaller diameter on the NT-700 as it is a smaller engine.  If anyone reading this happens to have an NT-700 kicking around and wouldn’t mind measuring the throttle body internal diameter and also checking distance between centers on the throttle body and angle of the throttle bodies, that would be a HUGE help.  To buy that assembly would set me back $5-600.  Not exactly something to buy lightly!

I’ve been thinking more about using the MegaSquirt kit to do the fuel injection timing.  It seems very flexible and has a large community of active developers and tinkerers.  The unit I was thinking about using though seems like it might not be released (MS-II Sequencer).  However, it seems like the MSI, MSII, or MSIII should work.  Especially with the “Extra” firmware.  Then I get a bunch of other fun management potentials (nitric oxide injection, spark management, etc).  This page seems to have a descent rundown of what’s what in Squirt-land.  It also seems that Wikipedia is useful to better understand all of the available squirts.  One of my buddies has experience using MSII.  He bought it from DIY Autotune who he says is a good company.  There are mods and kits to make the MSII do nitric oxide injection.  Also can do methanol injection with the NOx to give extra oomph.  That would be a future project…  And hella fun.  Although I probably would need a new engine after that 🙂

Looking at the schematic for the spark system for the PC800, it appears we already have the necessary sensors to feed information to a MegaSquirt for cam sensing.  That is VERY good news as there isn’t anywhere to attach an external sprocket and sensor on the PC’s engine.  Hopefully I can adapt the MS to take the ignition pulse information.

All the extra room under the gas tank that I’ll be left with is opening up some interesting possibilities…  I’m thinking about installing a comm unit, some radios (CB, FRS, a few amateur bands, etc).  It would also be great to have that extra space for auxiliary switches and dodads.  I’ve been wanting to install auxiliary gas tanks in the trunk.  A few switches on the faux gas tank would allow me to have transfer pumps and whatnot to trim out weight distribution in those rear tanks and also feed that gas into the primary tank or from the primary tank into the rear tanks.  Who needs an aircraft when you can cross-feed your fuel tanks on a PC800?

A post from Jerry on the IPCRC brought up the point that the throttle bodies that the VT750S uses have a 90 degree bend in them to allow for a side air cleaner box.  That won’t work very well with the PC800 setup.

Looking at the PC800 microfiche, I wonder if I could use the PC800 throttle body and carbs with some heavy modification.  I could drill out the jet ports to install the fuel injectors.  All of the random diaphragms and other parts could then be removed and the various leftover holes could be sealed with JB Weld or Hondabond High Temp Engine Sealant or screws or metal plates, etc.  It wouldn’t be as good as a purpose-made throttle body but it might work.  And it wouldn’t require any modification to the stock air box.

Now if only I had a spare set of PC800 carbs laying around to experiment with…  I fear I will be removing the carbs on my bike several times to take measurements and figure things out in the coming months.  I’d rather have everything ready to drop into place once.  It wouldn’t be so bad taking apart the bike all the time except for the small problem of me not having a garage.  I do all of my work in a parking lot outside the fraternity where I work (I’m the house dad).  I have to button up the bike every time I’m not outside working on it.  That becomes tedious very quickly.

I wonder if there are any automotive throttle bodies with fuel injection that would be the right diameter.  Or maybe motorcycle throttle bodies.  Surely there must be some vehicle with the same diameter intakes.