2056 switch from carbs to L-Jet: 914/4

[914werke]

So ... here we go,
I have a motor that was one of Jake & Mark from Orig Custom's "Kits" from back in the day. It was delivered as lng block & has been run sparingly since with carbs. Ran great, Stinky as hell, Carbs were a pain.
Recently I pulled the carbs & gathered the parts and pieces to convert it back to FI.
2.0L heads, chromoly PR's, 1.7L rockers swivel adjusters, SSI exhaust, 2.0L intakes, Bus/1.8L plenum, Gowesty TB, NEW injectors, Bowlsby harness, OE AFM, AAR, Late decel, non-adjustable FPR ect
so all the components were tested good replaced or updated. Bigger mtr. better breathing. Including the cam ....
The cam, unfortunately, was a mystery. Mark didnt have any records from back then & Jake had sold off the T4Store to Charles so they couldn't help.
I reluctantly pulled the pump to hopefully get a read... sort of successful. Couldn't quite read it all, but it looked to be either a 9530 or 9580 ..?
Regardless bigger cam, impacted vacuum signal....ya
Installed the system had to do a little custom work to fit the TB, the 2.0L intakes dont quite line up with the L-Jet plenum so silicone hoses & T-clamps, other than that its pretty stock 914 stuff.
Timed it like stock but couldn't get it to idle. Classic vacuum leak symptoms. Quickly found that the AAR while tested for closure, still was leaking air. Replaced it, still had the same issue. Smoke tested it ... nothing.
Had me scratching my head. One thing non-stock was the TB. To get the TPS to work, I had to create a adapter plate. sure enough the TPS isnt a POT but two switches for IDLE & WOT. Some adjustment & now I could actually adjust idle. Success! Or so I thought,
I hooked up a wide band 02 meter & it was crazy lean, Adjusted the AFM & took for a road test.
Aaaand this is where I am.
Ive been chasing my tail trying to adjust this thing to.. 1. Start easily 2. Idle consistently 3.Run under load without issue.
I feel pretty confident with D-Jet but Ive never had to do a deep dive with L-jet so Im feeling pretty stupid as It seems like its a simpler system to work with.
Please help guide me ...

20220528_214538.jpg

[Piledriver]

Welcome to the STF!
The factory LJet seup was quite simple and reliable, but is the opposite of tunable.
Djet has more bits you can play with, but still isnt going to like any reasonably stout cam.

I'm sure someone has said this previously, but the DJet or ljet manifolds/plumbing works great with a megasquirt.
Getting early non-programmable EFI to work with even a mild cam will be a challenge, even assuming all the 40-ish year old hardware is still 100%.
If you remove the flapper from the airmeter and run a distributor rather than LS2 coils, it can be made to look bone stock.
(you can probably use the airmeter but... dont...its usually whats wrong with old ljet setups)

I personally would find a set of new, modern high impedance injectors that fit (20-ish Ohm coils), buy a trigger kit from Mario and pick up a microsquirt, load the latest ms2extra microsquirt firmware, a 3bar gm map sensor (external) and get wiring. If broke, any junkyard can provide injectors/coils etc... pick up a 3bar gm map sensor and pigtail.(external) always grab the wiring and plugs they can be stupid expensive to buy.

If you are handy there are simpler/cheaper and arguably better ways to do the triggering using a steel rc truck spur gear and a tiny spot of weld, a hall sensor in your existing distributor, and a inch or two of brass tubing.

If you buy tunerstudio and start with reasonable values you can have a drivable tune given a few stoplights, and a decent tune after a few freeway onramp pulls. hills work even better. playing in the driveway only allows setting idle...

tunerstudio can also be used with the fully open source and hardware speeduino setup, which has 4 cyl sequential fuel/spark capability out of the box for a bit le$$... On speeduino it may allow the autotune without purchasing TS.
(but I still highly recommend it, or if TS is free to use buy Megalogviewer)

You could even make the webers work right if you just use them for air... a good linkage is critical, the CB hexbar is not a member of that set.
Great design if your engine only sits on a display stand and never vibrates or expands/contracts.

[914werke]

Finally getting back this post ...
Yup the story is a simple one. No Matter WHAT you did there was no way to "tune" out the lean spots (2 BIG ones) in the curve.
So I pulled the plug & started down the path of MS. Fortunately for me Mario lives fairly close by & I've know him his since the hm. garage days.
I've chose to KISS & go Microsquirt & common plenum. I looked at MAF vs MAP & it looks even to be an simpler setup but also seems to have less Knowledge support overall? Big work building a custom harness ~ providing for a 2nd MAP, AAR (fast idle) & perhaps a fuel pressure sensor (?) but not part of the initial troubleshooting & tune.

[Piledriver]

Congratulations, great choice, once tuned will drive like a modern car.
DJet was a great system on a bone stock engine with 1968 gasoline in 1968...
Anyone still running it gets respect for sticking with stock, but you could stick a MS2 in the OG ECU case and swap the TPS guts...
If you ran a distributor* no one would be the wiser, if you stuck with batch fuel you could probably stick with the original DJet harness.


*dont run a distributor tho, the cap/rotor etc are probably 30% of all engine woes, and nobody digs all white wire harnesses.

[914werke]

Oh this will still be batch (MS2 V3 only provides 2 drivers) but trusting a potentially 50 yr old harness thats lived its life in the bay of an air cooled engine is folly. I suppose you could buy one of Jeff's (Bowlsby) new reproductions but buy the time you are done (at close to $.5K then modding it) Im better served with a customized unit for the T4 with the connectors for the new sensors necessary.

[Piledriver]

Agreed, was just providing example.

I still have a distributor but it houses a 36 tooth steel wheel, a homebrew ATS667 based hall sensor module sticking out the side, and a Rustoleum spray can cap for a cover...72 tooth will fit a 009 style distributor body, (wheels are RC truck spur gears) and supports full sequential with one sensor. The harnesses fron DIYAutotune are great and wires are labeled every foot. I run LS2 truck coils hose clamped to the intake runners...
Trick? no, but an absolutely 100% effective coil $4 mounting solution.