Datsun 240z with L20ET

[L20A]

Hi guys, I thought that after watching Antus post about the build it was probably about time I made myself known.

I'm Ross, the owner of the 240Z in question here and although I've been lurking for a while I haven't posted or acually done a Delco conversion until now.

Firstly I'd like to thank a few people as this whole build took a mere 28 days from Antus pointing at a heap of rags in my shed that contained the car to it sitting in my driveway running (although with clouds of smoke behind it) at 2am on track day.



Much kudos goes to Antus and Bart for all of their hard work both in researching problems, recommending parts and fabricating parts. Many hours of cutting, sawing, grinding, drilling and bolting then rebolting went into getting this all together. They both spent a lot of time researching the delco side of things too as it has been a STEEP learning curve for all of us.

Next, Jayme for being an all round legend. Someone who can look at a table or a 3D fuel map and make suggestions without seeing the car, hearing the car or driving the car. Fantastic.

Also, thanks Mick (zzzzzzzed) for providing the motor (and 280ZX parts car) it's just a pity about the turbo but I knew it was a risk when we took it on.

Lastly, the rest of you guys for the encouragement to keep at it because a couple of times I really thought it was an impossible task! Thanks for the posts and hints/tips on where we might be going wrong or what we've forgotten. Some of the posts were funny too (baby intercooler ) but many were quiet insightful.

Now, to a status update for the project. The next track day is the 30th of April, so we'll be well organised and hopefully well tuned by then. Currently we are running through the tuning with Jayme and Ant poring over the logs from my last drive. Something's not right but we'll track it down!

The alternator problem above has been solved. The alternator we were using was an externally regulated item and the car had no voltage regulator. It seems a previous owner had hacked it out of the loom so after some digging in the shed and plenty of wiring diag reading I found an item that fits. Unfortunately it's a Prince of Darkness model (Lucas) but with any luck it will keep pumping out 13.8V when we need it!

Now for it to be considered finished (when is any project truly finished?) we need to replace the headlights with H4's as one of them has blown and get the dash gauges working. It seems that something is not right there... Oh, and wire up the taco to the new ignition module.
Anyway, I've attached a couple of pics of the 280ZX parts car getting scrapped, the 240Z on the lawn after it's first drive (and wash) in 5 years, the engine bay, and a couple of other pics that help illustrate the car in it's current state.

Once again, thanks to everyone who has contributed

Cheers,
Ross.

[Holden202T]

i had a set of them saas seats without the holes in them for the harness, they will be great for a track car and super comfy!

good to see you getting to the end of the issues and getting it dialed in! im keen to see some pics/videos of the track day when you beat ants gem

[antus]

Small update.. The H4 headlights are in and working. Turns out the headlight circuit on these has a lights on/off switch, which connectes a seperate 10 amp fused suply to each headlight, and then the high beam switch is either connecting gnd on the high or the low beam elements. So.. when you hook up another 12v supply and circuit for the relay and the lights, you omit the first switch and lights stay on! You can only select which element with the high/low switch. This +ve side switching doesnt seem to be in the wiring diagrams we have, but there you go. End result was hook the switched + side to the + side of the relay coils, and the high/low to the low side of the coils.. and now it all works fine.

It seems to be boosting well, but there is a wiring fault somewhere which is blowing the efi fuse, so we need to track down where that is. Hopefully not a big one...

And the tacho.. Its an early current driven tacho, designed to be inline with the +ve side of the coil, and it detects signal with an inductive pickup. Its not very accurate, and not compatible with a delco ignition module. And to be even more annoying the indiactor lights are in the same enclosure. So... after some consideration and searching we came across this project:

http://www.dinoplex.org/tachoconversion/index.html

And decided that converting the tacho to function normally was the tidyest and nicest option. The circuit replaces the dodgy inductive pickup, and points out how to calibrate the unit so it turns out better than original

So... I ordered a couple of attiny13a mcus and a handfull of compents, and now have this in front of me:

240 tacho converter.jpg (114.17 KiB) Viewed 5861 times

I still need to figure out how to flash the firmware on the processor. Does anyone know of an app that can flash attiny13a via a willem? Icprog comes close, but the way out of date docs dont mention that exact processor or have much info on how to set it up in the device. I did have an atmel ISP cable somewhere some time ago.. but It'd be nicer to stick it in the willem...

[VL400]

The GQ4x does ICSP by jumpering from the ZIF to a ICSP header, just need to supply the target board with 5v (or above if connected to the input side of your reg) but can sneak off some USB power for 5v. The earlier willems support ICSP too AFAIK.

[L20A]

@Holden202 - That seat is mega comfy and should do the job holding me in for the track day... as for beating Ant's Gem? Maybe through the twisties but now that he's got track rubber I think I might be left behind!

@antus - good work on the circuit board, now to get into the tacho and get it to work plus that annoying electrical problem...

Fingers crossed some on road footage will be forthcoming once the above mentioned issues are sorted out.

Cheers.

[Holden202T]

thats good cause we like pics and videos around here
and videos

[antus]

Well, it looks to be running ok now. The 'ballpark' tune seems to be in the ballpark, and we successfully revved it up to 6500rpm (still felt like it had more!) and 158kpa (8.4PSI boost). The boost spark is pretty conservative yet it felt pretty good. We tried to get some footage but being dark the video didnt turn out. We've found we do have an issue with the reluctor, we had a few frames either reading way too low or 9000rpm which really makes the car feel like its hit a wall! I suspect this is because our mounting isnt solid enough its vibrating around a little, and when these vibrations are in time with the notches or something it goes amiss. We can build a stronger mount, and get the end of the sensor mounted closer to the balancer. Also the fuel pressure seems to high, we'll have to figure out if the return pipe is restricting or if the regualtor is bung before attempting to tune. We'll also have to make some adjustments to the accelerator cable mount so we can open the TB further, but its oversized anyway, so probably isnt much of a restriction. Heres a nice screenie of where its at for now. Too rich for the end result, but OK for this stage of the game.

6554rpm 158kpa.png (8.29 KiB) Viewed 5820 times

[Holden202T]

good to see your getting the kms on it!!

sounds like the issues you have are only minor teething problems and she'll be sorted before too long!

[Six_Shooter]

The tach issue is why I went to an Autometer tach. Even a 280Z tach (260Z for you Aussies), would read fine until about 5500 RPM or so and then either peg or most commonly would drop to zero. It seems that the dwell of the tach output from the DIS module is too short and causes this problem at higher RPM, with the Datsun tachs.

Also your odd RPM reading could be due to the fact that your reluctor wheel is actually rubber mounted and will be slowing and accelerating as the engine spins, due to being a part of the harmonic balancer. This is the biggest reason I went to a separate bolt on wheel.

[antus]

We had a very good run tonight. First of all we put a usb scope on the original crank trigger, and noticed that the signal was quite clean and quite strong. We pushed it closer to the balancer and saw about a 50% voltage increase at idle, and pulled it as far back as we could (it did have too much flex in it) and noticed it drop to about 30% signal strength of what it was, and yet the engine still didnt miss a beat. This got us thinking.. Probably the issue is vibration of the sensor, but maybe also its too close to the notches? It was about 1.5mm. Maybe imperfections in the balancer are creating more of a signal than if the sensor was further back? And at high RPM the voltage was huge anyway... So... we built this. Its literally got about 4 or 5mm gap from the balancer, and it works perfectly - 100%. It revs out awesomely, idles perfect.. its f**king fantastic! Couldnt fault it in functionality So.. It seems < 1mm is not required. Even up to 6mm is ok!

New crank trigger-small.jpg (167.97 KiB) Viewed 5782 times

Then we looked at the fuel pressure. We disconnected the return pipe to see if it was a restriction, but still measured 6 bar on the fuel line. Ross looked at the regulator and figured out how to adjust, and before long we had it under 4 bar. Some quick adjustments to the injector rate to compensate for the decreased flow and the car was much happyer. Idle was heaps smoother, as we think fuel was leaking around the injectors previously. The injectors were also a lot quieter.

Then we looked at the accellerator cable to TPS mount. Some adjustments there and its now attached much more cleanly, and the butterfly opens 100%.

After 10 mins of spirited test driving however we got a CEL light due to high temp even though the thermo fan had been running flat out. So the cooling system needs some work, but it looks like its going to be all systems go for the track day saturday