Datsun Roadster Forum-311s.org

Greetings all! Well it's time to start the next chapter of the never ending project that is my car of 34 years. It started all those years ago when I came across a new Solex conversion kit when doing my first engine, and it's never really stopped. After many years of messing with nearly every carb version available for a U20 (Mikuni, SK Racing, OER Mikuni/Weber hybrid and finally Dellortos) I've decided to enter the world of fuel injection. The goal is not more power (though that would be nice!) but better driveability, improved fuel economy and lower emissions. I've discovered that the more you modify one system in the car, the more the limits of other systems become apparent. If I'm gonna get the best out of my modified U20, the next thing is better fuel control. The Dellortos are great carbs, the best I've worked with, but a fixed jet system simply cannot adjust to the different demands this more sensitive engine requires... I need computer control! I've taken it this far, can't stop now right?
Converting a carbureted engine to EFI has become more common these days, and if you have an American V6/8 you have complete bolt-on kits that tune themselves, but for us it's a bit more do it yourself, though thanks to the Internet there's a lot of support and options. I elected to go with a set of Heritage throttle bodies made by Jenvey in the UK and control it via a Microsquirt, a more basic system than the more well known Megasquirt. The Heritage TBs look a lot like Weber DCOE carbs, so the fuel rails, injectors and throttle positioning sensors are all contained within. I went with the 40mm size as I've been told it's better to go smaller than too large with EFI, and the biggest choke I ever ran in my carbs was 40mm (currently 37s) so I expect to flow plenty of air. EFI requires a high pressure fuel pump and lines, and a return to the tank my '67 never had. The stock tank would require a lot of modification and welding etc to install an in-tank pump, so an external pump was what I decided on. However, they can be loud, run hotter since they're not in fuel, and if the fuel level gets too low and exposes the fuel pick up in the tank I'll be getting all the hesitation issues I have now with carbs. Thusly I decided upon a surge tank set up that would allow me to put the pump in some fuel and provide a buffer for fuel starvation. I already run an electric fuel pump, so I decided to simply reroute it to feed the tank which would also accept my return line and allow me to install an additional return to the stock tank via the original vent. EBay and Amazon were my friends sourcing these parts, and after hours of looking at all the possibilities and trying to keep this project within budget (ha!) I had gathered the main components of this system. In the pictures you will see the Heritage TBs, surge tank with the pump installed, fuel pressure regulator kit, Microsquirt EFI computer with harness, and a high pressure fuel line kit. After looking over the car, I decide to mount the surge tank in an area under the passenger side of the car under the rear shelf. There's just enough room to fit the tank and allow me to run the fuel lines. I rubber mounted it with the hope that it won't transfer too much noise from the pump, but we'll see. One thing I would do (and probably will) is to install a drain plug in the surge tank in case I need to replace the fuel pump so I don't have fuel pouring out of it as I pull the pump. I mounted the low pressure pump near the tank and routed the high pressure fuel line up the drivers side to the engine, which then will continue to the TBs, then route in the stock fuel line path in front of the engine and over to the passenger side, and finally to the pressure regulator. From there the return line follows the old fuel line back to the surge tank. In case the surge tank is full, a second return was run to a new tank vent hose with a brass T, and as far as I can tell there shouldn't be any problems. I need to add a high pressure in-line fuel filter and will likely locate that on the driver side frame rail. The lines are run but not set, so I'll post pics later of the complete system.
This has been the easiest part of the install. Now comes wiring the pumps, and more complicated wiring up the Microsquirt. The MS can control ignition timing as well as injection, but I'm already doing this via the Megajolt and Ford EDIS system and I'm used to tuning on this system. However, it's redundant and it may make sense to eliminate it and just convert to the Microsquirt.
Before I convert to EFI I'm going to do one more dyno pull to get my real WHP since the last one was on 3/4 throttle (doh!) and do a short video of the air/fuel ratio now running carbs and showing why I'm doing all this! There's A LOT of work coming to learn and tune EFI, but I'll be using Tunerstudio which features a self tuning app once it's running and in the ballpark. I'm under no illusion that it will be easy, but that's part of the fun! Hope you find some enjoyment in this journey and come along for the ride. More to come!

Greg: Does this bolt up to a Solex manifold?

Shannon

Shannon
They bolt to any DCOE pattern manifold so yes

Sounds like fun times ahead Greg. I like the idea of the surge tank, seems much better than cutting up a good original tank. Hope it all comes together for you.

I've been enjoying the last few days of sun before pulling the car off the road, but now that the weather has changed the time has come. I wanted to get a final dyno run done to document "before and after" the conversion (currently on 45mm Dellortos with 37mm chokes), especially since the last one was done at 3/4 throttle. However, as usual for me, the dyno quickly proved that the street and the dyno are different. Before running on the rollers, I drove the car hard, monitoring the air/fuel ratio and seeing a max 11.7 to 1 on the top end which was rich but not significantly power killing. I felt a lot safer being rich than lean, so I was OK with this and the car felt good. Unfortunately this did not translate to the dyno, where instead it drowned the engine with a 10 to 1 ratio above 5000rpm. The engine showed only a bit more torque and HP than before, and you could feel it struggle to rev higher and see it on the graph. I was running the largest air jet I had, so I had no place to go, and a smaller main fuel had earlier shown a leaner mix than I wanted at lower rpms. I should have pulled the filters off, but the operator's time was tight as he had fit me in that day, so i just ran it. If anything, this run confirmed my desire to have full control over the ratio. Once I get the EFI tuned, I expect to gain improved throttle response, no more lean spikes, and a bit more power with a proper ratio. The engine made the most power it ever has, but it's still far from right. I may play with cam timing in the future but not before I know what it really does when it's not drowning.
Onward!

Pretty damn good power for a streetable motor..

Nice work Greg! Lets see what the engine bay looks like now with these?

Thanks Mike! Nothing like the screamin SR VVL... Oh what a sound that thing makes!

Current configuration with Dellortos:

Gregs672000 wrote: Tue Oct 13, 2020 9:15 pm Thanks Mike! Nothing like the screamin SR VVL... Oh what a sound that thing makes!

Current configuration with Dellortos:

Looks really cool Greg, nice work. Interested in the sound, post a video before/after!

Next time you go to the dyno, please have someone record a video!

OK, so I'm getting closer and thought I'd update things a bit. I went ahead and added a drain plug into the surge tank as I mentioned earlier. Decided I had one chance to do it before it was full of gas and needed to be drained! I also located a neat filter sock designed for this pump (gotta love the internet! Ebay!) so I added it. I also added an inline filter (not pictured). After much thought about what wires needed to go where, I ended up installing the Microsquirt unit from the underside of the dash passenger side, secured with a convenient bolt and some industrial double sided tape. Not all the wiring you see is it, but it does have a 30inch loom of which i only used some of. I don't want to cut it off for now. It helps that i have no heater etc underneath, Eh? I made a dedicated relay and fuse box board to power the MS unit, injectors and fuel pumps. It's mounted in the drivers left kick panel. No, that's not a kill switch you see; it's for resetting the computer to accept new upgrades. I did wire in a kill switch however . I figured out the linkage issues (hours of pouring over pics of linkage arms, but it finally came together. A U20 has a kind of unique linkage set up); located the pressure regulator and cut and ran the engine bay fuel lines; reviewed schematics, identified wires, planned, then routed and joined all the necessary wires for sensors, injectors, power, grounds etc; and installed the new wideband that will talk to the MSquirt. I'm pulling engine temp off from the same part that houses the stock sensor, except on the other side where there's a perfect spot to tap in a GM sensor. Intake temp sensor is inside the filter sock. I added to my existing plumbing for vacuum that I already had for the previous Megajolt and ran that to a MAP sensor and over to the pressure regulator. The last thing I'm waiting for are some banjo bolts and fittings for the throttle bodies before I run the pumps and check for leaks. Then, if all is good, I'll start learning about programing in my old timing map and a preliminary fuel map, setting sensors, etc. Good thing it rains a lot Here!

Hopefully you went with 40’s if your goal is improved drive ability.

JT68 wrote: Fri Nov 27, 2020 12:24 am Hopefully you went with 40’s if your goal is improved drive ability.

Yes I did, 40mm. I thought and read about this a lot, and was convinced that the biggest mistake people have made is going too big. I've run 40mm chokes in the Dellortos and it had more top end but was harder to jet at slower rpms. My only concern was the fact that the manifold is at least 45mm, so there's gonna be a step in the intake track (not an obstruction of course). I asked around, including Jenvey, and nobody could give me a definitive answer as to what this will do, though most felt it would not be an issue... we'll see! I'm hoping that it creates a previously unknown ramming effect that results in a supercharged intake ram air process that creates an additional 27 hp (wait... no no, 50 hp!) throughout the entire range... but I'm not holding my breath. Ya, improved throttle response will be nice... and a steady air/fuel ratio...

Greg,
The 40's are a good choice as they should be good for over 200 hp.

Just curious, did you add a second MAP sensor for constant barometric correction? It is a MAP sensor, but, doesn't measure manifold vacuum, just actual current barometric pressure. Considering drives here have a lot of elevation change, it is a near nescessity. Otherwise you have to shut the car off once in a while during elevation changes so the mixture doesn't go too rich or too lean. Only happened too me once and caused an overheating session. I was unaware of the problem at the time, but, shutting the car down and letting it cool while I searched for an actual mechanical problem did the job.

Daryl, thanks so much for the heads up. An additional sensor was not in the main schematic, but I believe this is mentioned in the literature and that there's a dedicated wire built into the loom for it. I don't recall reading how important this can be as described by your experience, but we spend a lot of time driving into the mountains and have already experienced an overly rich condition with my carbs. I will definitely want it to be able of adjust to altitude, so I will look into that today and post later. Thanks again!