Might EFI my 1976 RD400 this winter

[rd400canuck]

I have a couple questions that I dont have the knowledge to answer...

Lets say I am holding the bike at a steady 5000rpm at 50% (or 70, 80, 90, 100%) throttle under a load.

Can I just add/delete injector pulse width until the bike no longer gains rpms and assume that is the the optimum setting for that rpm/throttle setting for max power?

Also, If i ever want to create my own ignition map.. can I do the same with retard/advance of ignition for a set rpm/throttle, back it off a degree for safety cushion and call it a day?

Yes and no.

At say 100% throttle at say 5,000 rpm, the bike should accelerate.  If you had an eddy current dyno that adjusts the load to keep rpm steady, you could do what you suggested.  You basically set it to run from say 2,500 to peak revs at say 10% throttle and log the A:F and repeat every 10% to see what the "map" is and then adjust it from there to get the A:F you want at any point on the map.  At cruise, you want a fairly lean (not catastrophically lean) condition and as you open the throttle you want to get to power A"F which is much richer. At higher revs and say 0-20% throttle you need to be a little richer to avoid a lean stumble as you slow down.

OK thats what I was wondering...  I might rent an eddy dyno and a tuner to help me in the future. I was just wondering, since it's a two-stroke, if there is anything funky that can happen if I tune this way. Im fairly certain they do that with 4-strokes... just feed in spark until they get to the point where it is no longer pulling any harder and then they back it off 1 degree for a safety and leave it like that.

Same with fuel... can I hold it at steady rmp and 100% throttle and just increase the fuel until it ceases to pull any harder. In this case I wonder if max power is going to be too hot... but i dont think so. Max power isnt a lean condition afaik.

[sav0r]

OK... everything has been ordered.... god help me (and you guys too, of course) down the rabbit hole I go again 

Ordered the VAPE from EC, the Microsquirt and R6 throttle bodies.

Still trying to find an external inline efi fuel pump that isnt capable of 250HP...  Id like to draw as little as possible... however the vape has 150w.

Any ideas on fuel pump?

Godspeed!

How about a BMW pump from on of their bikes? My father and I fixed an R100 (maybe a K75) a few years ago with some random pump we found online. Unfortunately it's been too long and I don't recall the details. The pump was in tank, so you'd have to navigate that, but I think inline versions exist.

[teazer]

Lots of bikes with carbs used external fuel pumps back in the day.  Two issues with those.  First, the pressure may be insufficient for your EFI which will probably need 3 bar or so, but check on the injectors and what they came from to match them.  Secondly most external fuel pumps on ebay come from China and some of them leak like sieves. I have a few you are welcome to try at no cost.

I suspect that most EFI pumps are in tank and have a return line plumbed in as well.  That's how my old Duc is set up.  Submerged pump and a return line to generate more or less constant pressure when the injectors open and close.  If there is no re-circulation, the pressure will build up during the closed part of the cycle and then the flow rate will be higher than planned for the next cycle and fueling might be all over the map.  I have not tested that hypothesis.  It's just speculation on my part. 

If you look at a power or torque curve for your bike and estimate BSFC at different points, you should be able to work out injector capacity and duty cycle percentage as a series of starting points.  When I did that for a GT750 it basically suggested that injectors large enough for the massive HP I was aiming to extract, they would be so large that they basically were no use at small loads, so that meant I was supposed to go with twin injectors like any decent HP motor.

Shower head injectors were not an option so I kinda shelved that project. I planned to use GSXR 34mm throttle bodies with the secondary throttle shaft removed and plugged.  I think I tripped over them the other day gathering dust.

[sav0r]

External pumps like to overheat when you are pushing enough pressure for EFI. That's why in tank has become standard. We fought extensively with this on my fathers hot rod Mini. The tank is only 7 gallons and my father didn't want to submerge a pump because the extra volume is needed, but after like 5 in-line pumps left him broken down we decided to try a submerged pump. It's been going strong for years now.

[rd400canuck]

concerning inline external high pressure fuel pumps I think they need to be in a return feed setup and this is what keeps them cool. The R6 fuel rail has the pressure regulator on it and a nozzle for the return line back to the tank using the fuel tank as a heat exchanger for cooling. There are some guys around who've used these pumps on Rz's and i cant really remember anyone of them experiencing issues with them.

I havent looked into the R6 injectors but I seem to think they run at 67 psi something like that EDIT... looked it up, it runs at 45psi... and other bikes i see now, like the ninja 400, seem to be set for 45psi. I plan on using the stock regulator so im good to go with the stock injectors.

Im fairly certain the Walbro external replacement pumps for something like the econoline vans of old are of good quality. Fingers crossed!

I think this will be a good choice from a trusted maker...   https://walbrofuelpumps.com/walbro-gsl393-fuel-pump.html

[sav0r]

Walbro pumps are exactly the pumps we smoked multiple times on my father's Mini. They are probably okay pumps, the layout of the Mini is particularly strenuous (hot). The pumps are pretty noisy, which is a big drawback in my opinion.

I'm sure you'll regulate fuel pressure, so all you need is a pump that can exceed the regulated pressure.

[rd400canuck]

Walbro pumps are exactly the pumps we smoked multiple times on my father's Mini. They are probably okay pumps, the layout of the Mini is particularly strenuous (hot). The pumps are pretty noisy, which is a big drawback in my opinion.

I'm sure you'll regulate fuel pressure, so all you need is a pump that can exceed the regulated pressure.

Do you know if youre father had a return line or not on his setup? I can see them burning out if there is not constant fuel flow cooling them.

[sav0r]

Yes there was a return.

The car is rather tightly packaged and ambient heat was high around the pump. Keep in mind the car is mid engine and has to move fuel from the front of the car where the fuel tank is located to the engine in the middle of the car. The fuel lines run along side coolant lines through a tunnel between the seats inside the car. The example isn't particularly relevant to what you are trying to achieve, except that we just had bad reliability with those pumps. The Walbro pumps we had were all very loud, even for a car. They get even louder when they are getting ready to crap out.

[rd400canuck]

I did notice when looking through all the EFI pumps available that people were leaving comments and saying how quiet certain ones were.... I better look for them again and see which ones they were talking about.

R6 throttle bodies arrived.. parts are rolling in.

Anyone have ideas on how I might attach them to the intake boots?  EC sells a pair of boots for larger carbs... Id like to order them if I knew I could get this suckers in them.

In the other pic you can see my plan so far... cut the fuel rail to length then cut and weld back together. The tab on the throttle will need to be extended to reach the other' tab. Also each body has it's own spring to close the butterfly valve however the the one that has the throttle cables attach was about 3 times stronger than the others. I despise tough to twist throttles so I took one of the weaker ones off an unused body and replaced it. Feels way better.

Testing will show whether or not I keep the vacuum operated slides in them. Im assuming these are needed on the R6 to smooth out off idle so the bike isnt as jerky but the RD wont have vacuum like a 4-stroke. I will test with and without them and see if they need to be yanked up permanently.

[Brad-Man]

Datsun used external Bosch fuel pumps on the 280 Z's and ZX's that don't die..

Plenty of capacity but rather large...

[pidjones]

The EFI 1986 GoldWing SEi used a high pressure pump almost identical (I used one to replace a failing OEM pump) to an automotive pump that you could pick up at a parts store for ~$109. But, you still need a fuel pressure regulator on the rail to circulate extra pressure back to the tank.

[rd400canuck]

The EFI 1986 GoldWing SEi used a high pressure pump almost identical (I used one to replace a failing OEM pump) to an automotive pump that you could pick up at a parts store for ~$109. But, you still need a fuel pressure regulator on the rail to circulate extra pressure back to the tank.

I found this replacement for the EFI Goldwing https://www.highflowfuel.com/qfs-oem-replacement-external-efi-fuel-pump-for-honda-goldwing-gl1200-efi-1986-replaces-16700-ml8-751/?sku=HFP-603-56711&gclid=CjwKCAjwzaSLBhBJEiwAJSRokryt5Iz74ckGoplYkQ-szud7D8kGmtufeNzyG95f6IVWWZ_Fng3pHxoCytoQAvD_BwE

and used their part number to find this in caanda...   https://www.amazon.ca/gp/product/B01N4UW7LY/ref=sw_img_1?smid=&psc=1

Looks promising

Finding an external EFI pump that is less than 190L per minute and not super expensive is looking impossible. I'll settle on this one for now. I have a regulator right on the stock R6 fuel rail so all good there.

[rd400canuck]

look what I found... 

https://www.amazon.ca/Carbpro-16700-HP5-602-FOREMAN-RANCHER-TRX420/dp/B088LXHKTL/ref=sr_1_5?dchild=1&keywords=HONDA+FOREMAN+RANCHER+fuel+pump&qid=1634409884&sr=8-5

Still trying to find specs on it but its EFI pump for honda foreman. A little bulky but unless I find something better this is what will go in. Obvs my concern is amp draw and the smallest walbro pump i can find is 6amps so this should be way better than that.

[rd400canuck]

ok, parts are rolling in... in balls deep now. Should be an interesting winter in the garage.

Still trying to find a fuel pump that is suitable.

[rd400canuck]

Got my Vape from EC :)

I just wanted to ask... where is the ECU that controls spark curve? It seems its right in the coil assy to me. And if so... now I'm wondering when I get my Microsquirt to take over ignition duty will I have to replace the VAPE coil for one with no ECU in it?