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Might EFI my 1976 RD400 this winter

Started by rd400canuck, October 11, 2021, 11:25:49 AM

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rd400canuck

So 15 years ago I had an RZ350 and started to fuel inject it with a megasquiirt and some throttle bodies from an R6. I had it running and was about to start the arduous tuning process (i didnt have an O2 sensor) but I decided to get leukemia instead so that was the end of that.

Now I find myself yearning for a project to sink my teeth into and EFI popped into my head again. The plan is keep the airbox and use an O2 sensor this time to help with tuning. I have a 2004 700MXZ here I think I might sell to fund the project.

First thing would be buying a Vape ignition because I'd want the extra wattage it generates to run the fuel pump. I highly doubt the stock makes enough juice. Also there is no coolant like the RZ but I'm fairly certain people run those spark plug head temp sensors and alter the tables in the code to adjust mixture as the bike warms up. I have 10ah liFeP04 cells and Id use 4 to build my own 12v battery to make sure there's plenty of juice if I ever get caught in stop and go traffic. The Megasquirt has ignition map capability but I dont think I'll go down that road for fear of melting holes in pistons. This will really just be a project to keep me busy and interested over the winter.

I'm still a little on the fence if I take this on, tho.... im trying to save a down payment on a house and heading down this road will easily cost $2000 if not more. Im telling myself if I sell the sled its money I wouldnt have had anyways so.... its ok to spend it on this project.

If I do go down this road... there is still time before the snow to order a Vape and get that on and running. Once thats done everything will be in place to start EFI build.

Am I crazy?






m in sc

just out of curiosity.. with a 2t, would it be frugal to also add an egt to supply data to the ecm?


rd400canuck

I'm planning on adding them but for a gauge I can see....  Ive not yet started my research into what the megasquirt is capable of 15 years later so maybe feeding and EGT into it is doable. The thing is... what values mean what out of them? I guess I could add them before EFI and logging what they run now as a baseline but my bike is surely rich everywhere.

I'm kinda hoping the O2 sensor will tell me exactly what is going on with combustion and I can play it safe using that data.

rd400canuck

Been on fleabay looking around...  looks like Yzf-R3 throttle bodies are ideal. I wont need to mod them or the fuel rail like I had to with thr R6 ones... these are from a twin that makes 35 rear wheel hp. I think they and their injectors are a perfect match for what the RD400 needs.

The only icky part is I think they are 32mm throttle bodies so I'll have to figure out something simple to adapt them to the RD intakes.

Also... anyone have a preference as to where to buy Vapes's?  Things are pricey!

m in sc

johns is about on par with pricing with the vapes, i get mine from him.


Striker1423

#5
Sorry Mark keep clicking the wrong thing on my phone.

Striker1423


rd400canuck


m in sc


sav0r

EFI sounds like a lot of fun and potentially a lot of power and rideability.

I'd go O2 and forget CHT or EGT. I have used both extensively, generally recording them at like 20hz, and they just aren't that great for street use. CHT is particularly worthless, EGT can be used with great results on the race track, but it's not particularly valuable on the street.

I've used wide band lamda as well, and it's really pretty much the way to go. With a 2t you have to use heated units, and if you get too rich they will foul. Sometimes they will clean up, sometimes you have to clean them, but sometimes they are ruined. The other issue with a 2t (and any engine) is that you have leakage ahead of the sensor it will send your readings well off. This is particularly tricky on 2t's as we all seem to like to keep our expansion chambers loose on the spigots. Certainly not an insurmountable thing to figure out, but it should be on your radar if you go for it.

For what it's worth, I spoke with Jeff Miller and he says that on their engines the added complexity and weight of EFI wasn't providing enough of a benefit to justify switching from Lectrons. I guess they made a pretty good attempt at EFI and then reversed course back to Lectrons. That said, if you just want a fun project, then none of that matters. Somebody on DoTheTon had an EFI RD350 that looked pretty cool, so I don't think it's out of the question.

Jeff Miller's 2t project - https://grassrootsmotorsports.com/articles/two-strokes-genius/
www.chrislivengood.net - for my projects and musings.

pidjones

Just curious where the best O2 sensor location would be, considering the reversals and all.
"Love 'em all.... Let GOD sort 'em out!"

rd400canuck

#11
My plan is weld the sensor bung just after the header a few inches pointing nearly straight up to prevent any oil from seeping into it. Once I am done the tuning it will be removed. The head temp sensor will only be used to tell the EFI computer that the bike is cold and to richen the mixture (choke) and open the Idle Air Control valve until the bike has gotten up to temp. After that it will have no effect on the a/f ratio.

The thing that has always confused me is Ive always been told that unburned mixture always makes it way into the exhaust system in a two-stroke so how is it that people can use an O2 sensor to tune them?

m in sc

thats exactly why i suggested an egt. between the 02 and the egt you should get a good overall view of whats going on in the quickest realtime manner possible.

rd400canuck

Quote from: m in sc on October 12, 2021, 01:02:56 PM
thats exactly why i suggested an egt. between the 02 and the egt you should get a good overall view of whats going on in the quickest realtime manner possible.

Will defo be running EGT while tuning... but my experience with them from my RZ days tells me to take them with a grain of salt. The RZ would burble at WOT with particular jets... id drop down one jet size and it would pull cleanly. I assume I could have gone leaner but even at this the gauge needle would go past the safe zone (past 1400f I think it was) on the EGT gauge. I put the sensors exactly where the instructions said to as well. I knew a guy that raced old TZ's and he experienced the exact same thing. So there's that lol...

Also, there was a fellow named Smurph on RZ forums that EFI'd an RZ and he tuned the bike with an O2 sensor and he seems to have got it running perfectly. I remember him stating that the bike felt "electric" when talking about how the power was made.... so he musta tuned it pretty good with the O2.... which leaves me scratching my head again.... how are these guys able to do this if even the smallest bit of O2 will throw off the measurements?

I guess I'm about to find out for myself.... im leaning more and more to actually starting this project.

m in sc

youre going to get mixed results with just an 02 as well. more data is ALWAYS better.