Datsun Roadster Forum-311s.org

Finally an update!
So it's been another one of those life gets in the way situations. Long story short, sold a house, built my mother in law a detached apartment on her property then moved into the main house which hasn't had any major updates in... 30 years? So yeah, been super busy making a house a home. 2 bedrooms, one bathroom and the living room finished, 2 more bathrooms, 2 more bedrooms and the kitchen to go. Plus all the landscaping etc etc. The plus side is that now I reside under the same roof as my car!

Now onto the fun stuff. As I've been super busy with house stuff (and half the garage is currently a workshop for house projects) I haven't had time to really bolt things together. But I HAVE had time to spend money on parts!

Most of the progress has been on sizing components for an EFI system. And I finally bit the bullet and got a pair of Borla 2700 SU replacement throttle bodies with built-in injector bungs.

The plan is:
Bolt in replacement for the SUs with 1 injector per 2 cylinders.

Modify the distributor and add an optical encoder inside the body.
Run a wasted spark smart coil (VW style, I believe Daryl is using it?). Haven't purchased that one yet.

Map sensor mounted on balance tube in intake manifold.
Intake air temp mounted on inside of air filter box.
Coolant temp sensor mounted in the usual spot with adapter bung. (And heat shield)
Mechanical water pump and electrical fan. No thermostat and 240sx housing.
Microsquirt ECU running siamesed port injection code, Alpha-N and MAP blended tuning. Also controls fan on/off.
In tank fuel pump and primary filter with 10 micron filter down stream. 3.5 bar pressure regulator (I believe from a late model honda?).
PCV with 90 micron filter mesh (same as used in high pressure air lines) mounted where the low pressure fuel pump typically sits. Oil catch can between valve cover breather on air filter box.
LiIon battery mounted up against the firewall for reduced weight and more rearward weight distribution.
Uprated Denso single wire Alternator on passenger side.
4-2-1 exhaust header with two O2 sensors (needed for tuning the injector control). Once it's tuned I'm hoping to be able to remove one and put a single O2 downstream for closed loop control purposes. High flow catalytic converter under the driver's seat and muffler out back.
PWM 2-wire Idle Control Valve mounted to the air filter box with a split hose going to the throttle bodies.

What am I forgetting?

Something for sure. More pictures as parts come in and I have a chance to draw everything up, test fit things etc.

Some potential issues that may need to be addressed during tuning:
The accuracy in crank angle measurement using an encoder inside the distributor housing may not be good enough for spark and injector timing. If that happens then I'll have to put a sensor on the crank as well.
The fuel pressure may not be high enough to capture the full range of fuel needed from idle to WOT and max engine speed. May need to purchase an adjustable regulator to better dial it in.
In case it ALL fails then I will need to build a new intake manifold from scratch (or modify a stock one) and 4 injectors as the good lord intended!

So what's the motivation for all this? I'm interested in developing a simple, robust, bolt on EFI solution using a minimal number of parts and OEM equipment which is easily available. I decided to start with the SU manifold as they are plentiful and inexpensive compared to the more desirable DCOE style. (At least from what I can tell). So let's see how this goes! Still very much in the design phase and my engine still needs to be bolted together so a long way to go but it should be a learning journey!

If this works it could theoretically be applicable to any number of 4 cylinder twin SU engines from the same Era. Volvos, MGs, Triumphs etc. If not then it'll be a fun exercise anyway.

Nice progress my friend! I'm looking forward to hearing how those TBs work, as well as how much spark scatter you experience vs being crank-fired. The modification of the crank pully is something that most will need to farm out so that can be a barrier to conversion for some. An easy alternative would be helpful in making a bolt on system. I'm using a vacuum referenced fuel pressure regulator downstream from my TBs that then returns to the swirl tank to keep fuel pressure at about 60lbs (what my injectors want). Did you say "no thermostat" for the rad? I think you'll want one as my engine will not warm up to a good operating temp (190) without one and without will likely require a richer fuel mix (?). I want to see pics of your crank case ventilation system as that may make a difference on our motors. I'll also be curious about the cat converter... brand, shielding and how hot it gets. I've been considering one for a long time to reduce emissions but I'm not sure it will help much as carbon dioxide is a problem as much as monoxide and hydrocarbons (can reduce exhaust smell though, but its better now than it used to be with carbs). I think the best thing is that I can tune it to cruise consistently at 14.7, which from my understanding is the best balance for carbon monoxide and hydrocarbons. (Any thoughts?)

I should be on the rollers later this month (ya, been saying that for quite some time!). While tuning, Auto tune kept creating lean issues so I finally decided to no longer let it update the controller on the fly until I review the actual data logs and compare what the A/F ratio was vs target and then what Auto tune was recommending. Often the ratio was good or a safer slightly rich vs the auto tune suggestions which were resulting in 16s or leaner ratios regardless of my target A/F... not ok under load!

Keep up the good work! Fun stuff!

Hey Greg!
Yeah I'm still investigating the cat side of things. As with anything in the exhaust it's always a trade off between better emissions and reduced power. I would like to do more than just pay lip service to emissions reduction but everything has a limit both practically and from a budget perspective. Magnaflow sells a variety of universal cats around $200. If they work well and don't cost too much hp seems like a reasonable price to hopefully minimize my impact on the environment.

https://www.magnaflow.com/products/9920 ... er-99205hm

Above link is just an example not necessarily the one to use.

It's my understanding as well that stoich is the best overall minimum of emissions. Leaner than that and nitrogen oxides start to spike. I have a chart somewhere which shows emissions vs afr. Will need to see if I can find it.

Very exciting about getting on the dyno! As always if you need a hand or don't mind me snooping around while the tuning is going on I will definitely make the trip!

David, I will definitely let you know when im scheduled... might use your help even!

Some more minor progress on getting these throttle bodies to work. After many hours of online research into which injectors and TPS to use, I finally got some time today to swing by O'Reillys and do some fit checks.

I was able to determine that to work best the injector needs to have an extended nozzle which I had theorized based on pictures but wasn't able to validate until in the store. In order to work with the aluminum fuel rails bosses however, I would need to use the long sized EV14 injector or any of the older EV12 (EV6 extended) style ones. Unfortunately, finding EV12s in that style with the flow rate I want and the spray pattern I need is tricky. Will have to keep looking.
Regarding the TPS sensor. I thought I had found one from a late 99s early 00's BMW that would fit the bill but when I tested it I realized that it rotated the opposite direction and bottomed out the sensor long before WOT. Oh well. More research and testing till I find the right stuff I guess.

Overall I must say I'm satisfied with the quality of the throttle bodies but not overly impressed. It looks like they should serve purpose but to be honest in the future I would probably just design and build my own incorporating some significant improvements.
Firstly, I would remove the fuel rail bosses. They're over built and having them means that fitting shorter injectors isn't really possible. I may machine them off if I can't find a long body injector with the appropriate characteristics.
Secondly, there appears to be a little bit of lateral movement in the throttle shaft at WOT. Considering that actually WOT occurs at more or less 80 degrees, I will probably just adjust the throttle stop to not allow it too much throttle.
Thirdly, I feel like the throttle shaft is quite large for the bore diameter. The blockage looks much larger than it needs to be and one could certainly knife edge the throttle plate to improve flow.
Oh well, all things that can be improved but definitely aren't show stoppers so onwards!

Well 2 steps forward and one step back. I have been working on getting the main bearings sanded to size as most of the ones from the kit I bought were too tall. I invested in a small honing plate which has been working great with some fine grit wet sandpaper on it. I've also been using that to clean up and flatten out various sealing surfaces around the block in preparation for final clean and reassembly. I even spent a bit of time on the 5th main bearing cap sanding down the sides enough to get it to slide into the block. It was an absolute bear to get in. It was so tight I needed to whack the ever loving bejesus out of it which of course would dislodge the bearing. Finally sanded it down enough that now all I need to do it give it some gentle but firm taps to get it into place and....
Finally everything fits!

Except not quite. The middle bearing cap torque procedure felt weird compared to the others. At first I thought it was just the tightness of the cap in the block but after I removed the caps to check the plastigauge, I realized that the bearing had still been too long and deformed as I was torquing it down.

So now I need one replacement center bearing. Don't suppose anyone has one just hanging out they'd be willing to sell me?

At least all of the other bearings checked out great on the clearance!

The learning continues... one of these days I'll have the bottom end done and will have freed up space on my workbench!

Thanks for the updates, I've been wondering how things were proceeding. Not sure why you have had such issues with bearings unless I'm forgetting some mods you have done to the crank or? As far as I know I've never had any issues other than making sure I got the correct oversize.

Our friend Daryl is closer to firing his TB injected motor but working on linkage issues right now. My car is just sleeping, waiting... waiting... summer... warm... warp drive... zzzz...

Yeah I purchased them a couple years ago when I was cruising through some vendor sites. I saw them as the only bearing option on that site (if I recall) and ordered them. Then I found a different site that had two different options. Should have just gone for the more expensive one but thought, I'll make it work. Almost did! Luckily the old center bearing is still in really good shape. Or I get a whole new set and hope they are all correct.
Either way I'm going to finish block prep today so that it's ready for reassembly.
Did you ever get your car on the dyno? I also have a PCV valve design ready to go. I'll order up the components I need to make a couple of them in case you wanted to try one out.

No dyno but she's finally ready, running really well. Had a few issues mid summer and I just wasn't able to get time scheduled. For sure this spring... maybe you can join me! Very interested in the venting system!