L jet on 2L heads, how to fit Options

[rfinegan]

How are people fitting the Ljet intake manifolds to work with 2.0L heads? FWIW this will be on my 2056.

[914werke]

I used custom silicone connector hoses

[rfinegan]

So you use the Djet runners on a Ljet plenum? SO it fits the head pattern ?

I used custom silicone connector hoses

[Dave_Darling]

You'd have to use the 2-liter runners. They're shorter than the 1.8 ones, so you need longer hoses to connect to the intake air distributor. (AKA the "plenum".) The runner pipes are the same diameter, or close enough.

--DD

[914Sixer]

Take the 1.8 runners and drill 3rd center hole. You should be able to bolt on 2.0 spacer block on and use it as a pattern for hole.

[TRP]

Will you be running bigger injectors for the 2056? Any other tuning necessary for the L Jet?

[JamesM]

Find a 912e system (IMG:style_emoticons/default/lol-2.gif) (IMG:style_emoticons/default/lol-2.gif) (IMG:style_emoticons/default/lol-2.gif)

Seriously though if you have 3 bolt heads and 4 bolt runners you will have to modify your 1.8 l-jet runners or swap your heads. If I recall the 2.0 runners are going to come up short and in the wrong position to work properly with the 1.8 plenum. You could probably adapt them with soft hose or physically modify them but I suspect using modified 1.8 runners would be a cleaner setup. 1.8 and 2.0 runners are the same ID so you are not losing anything.

[JamesM]

Take the 1.8 runners and drill 3rd center hole.

The other 2 holes will also need to be enlarged as they are in slightly different locations.

[914werke]

So you use the (2.0L) D-jet runners on a Ljet plenum? SO it fits the head pattern ?

I used custom silicone connector hoses

(IMG:style_emoticons/default/aktion035.gif) for good measure I used SS tight seal bolt clamps as well.

[GregAmy]

Genuine curiosity: why? Rebuiliding a 1.8L with 2L heads and that's what you have? How will you tune for the airflow difference?

My interest comes from the FI system. I've got Microquirt on my 2L using DJet induction and I've been curious of the LJet induction would flow more air (I would not use the MAF). I thought about getting an LJet induction and trying it out.

[rfinegan]

@GregAmy , This will be and after market EFI crank trigger system purchased here.(Eltromotive/clewett) Im think the 1.8 manifold holes can be tig welded up and a center hole added to the flange. Making for a Clean OEM looking system with little fabe work. After its up and running a larger Throttle body can be added with a bolt on Go Westy? We will see how this goes. I am mostly done with the heads as we work on getting the 2056 sealed up again

While I have the welder out , i may as well add an O2 bung to the Bursch/SS HE exhaust too

[rfinegan]

Thanks every one for the intake tips....no more syncing or idle jet cleaning for me.... moving forward

[914werke]

In my case it was a 2056 that I fitted a GoWesty TB L-jet kit to & also applied the intake air mod proven and documented by Deming oh so long ago.

[GregAmy]

Good info...so it appears the LJet is the preferred induction? I might just sit back and watch and then maybe give it a go...

[ClayPerrine]

I have run L-Jet on a 2.0 engine. The runners are shorter, and you need longer hoses. That's it. It will bolt on and run.

Now I suggest three things.

1. Bigger throttle body. The factory throttle body for a 1.8 is way too small for a 2.0, much less a 2056. I used a 2.1 vanagon throttle body, and that woke the motor up big time. But they are getting harder to find, so the GoWesty throttle body is a good solution. It just doesn't look as stock.

2. Remove the snorkel on the air cleaner. The end of the snorkel is the same size as the stock throttle body. So the snorkel has the same restriction. If you really want to get radical, cut holes in the bottom of the air filter box. That will improve the airflow into the AFM.

3. Replace the injectors. Get injectors for a 1980 Datsun/Nissan 280ZX. Nissan used a license built copy of the Bosch L-Jet on them, and the injectors are slightly bigger than the stock 1.8L injectors.

Hope that helps.

[rfinegan]

Chat GTP 5
on throttle body size for 2056:
Short version: pick your target peak-RPM and volumetric efficiency (VE), estimate the engine’s peak airflow, then size the throttle so the airspeed at WOT near peak power lands in a reasonable range (usually ~250–325 ft/s for a single throttle). Here’s the quick way:
How to size it
Convert displacement to cubic inches
CID
=
cc
16.387
CID=
16.387
cc
​

For 2056 cc: CID ≈ 125.5
Peak airflow (4-stroke NA engine)
CFM
peak
=
CID
×
RPM
peak
×
VE
3456
CFM
peak
​
=
3456
CID×RPM
peak
​
×VE
​

Choose a target airspeed through the throttle at peak power
Common choices at WOT: V = 250–325 ft/s (lower end for torque/driveability; higher for top-end bias).
Solve throttle diameter from volumetric flow
First convert to ft³/s:
Q
=
CFM
/
60
Q=CFM/60
Then area
A
=
Q
V
A=
V
Q
​
and diameter
d
=
4
A
π
=
4
Q
π
V
d=
π
4A
​

​
=
πV
4Q
​

​

Convert ft → inches → mm as desired.
Worked example (2056 cc, NA)
Assume peak ≈ 6500 rpm, VE = 0.90 (healthy street/track build).
CFM
peak
peak
​
=
125.5
×
6500
×
0.90
3456
3456
125.5×6500×0.90
​
≈ 212 CFM
Q
=
212
/
60
=
3.53
 
ft
3
/
s
Q=212/60=3.53ft
3
/s
Now pick a target velocity:
V = 250 ft/s → d ≈ 1.61 in (41 mm)
V = 275 ft/s → d ≈ 1.54 in (39 mm)
V = 300 ft/s → d ≈ 1.47 in (37 mm)
So for this 2056 cc, a single throttle around 37–41 mm is right in the pocket, depending on whether you favor midrange (bigger bore / lower velocity) or peak power response (smaller bore / higher velocity).
If you’re using individual throttle bodies (ITBs)
The math above assumes steady flow, which underestimates ITB size because each cylinder inhales in pulses. Practical rules of thumb for a ~2.0–2.1 L 4-cyl NA:
Street/track cams: 40–42 mm ITBs
Hotter cams / higher RPM: 42–45 mm ITBs
Pick near your intake port diameter (or slightly larger) and consider a gentle taper for signal and atomization. ITBs smaller than ~36–38 mm on a 2.0 L often choke the top end; larger than ~45 mm can soften low-speed torque and throttle resolution unless the combo truly needs it.
Practical adjustments
Add ~10–15% headroom for shaft/plate obstruction, filters, and real-world pressure losses.
Re-run the calc with your intended peak RPM and a realistic VE (0.85 street, 0.90–1.00 well-sorted NA).
Match the throttle to cam, port CSA, and target RPM; the smallest “non-restrictive” bore that meets your power goal usually drives best.
If you want, tell me your target redline, cam/VE estimate, and single-TB vs ITBs, and I’ll plug your exact numbers and suggest a specific size.
You said:
single throttle body target rpm 6000 redline
ChatGPT said:

Thought for 32s
Nice—thanks for the details. Using 2056 cc (125.5 CID), single throttle, and peak ≈ 6000 rpm:
Peak airflow (NA):

CFM
=
CID
⋅
RPM
⋅
VE
3456
CFM=
3456
CID⋅RPM⋅VE
​

VE = 0.85 ⇒ ≈185 CFM
VE = 0.90 ⇒ ≈196 CFM
Throttle sizing from target airspeed (good WOT targets for a single TB: 250–300 ft/s):
d
=
4
(
CFM
/
60
)
π
 
V
  
  
(
ft
)
→
mm
d=
πV
4(CFM/60)
​

​
(ft)→mm
Results (rounded):
VE 0.85 → 250/275/300 ft/s ⇒ ~38.2 / 36.4 / 34.9 mm
VE 0.90 → 250/275/300 ft/s ⇒ ~39.3 / 37.5 / 35.9 mm
Add ~10% area headroom (shaft/filters/real losses) → diameters increase ~5%:
VE 0.85 → ~40.1 / 38.2 / 36.6 mm
VE 0.90 → ~41.2 / 39.3 / 37.6 mm
Recommendation
For a 2056 cc at ~6000 rpm on a single throttle, you’ll be right in the sweet spot with a ~38–40 mm bore.
Favor ~40 mm if you want a bit more low/mid torque and softer tip-in.
Favor ~38–39 mm if you want slightly higher airspeed and snappier top-end response near 6k.
If you share the cam/VE estimate or intended manifold (long-runner plenum vs short), I can tune that to a specific part number.
You said:
long runner and .465/465 lift/ 288/298 duration: lobe center 108
ChatGPT said:

Thought for 36s
Great—thanks for the cam and runner info.
That cam (0.465/0.465", 288/298 adv, 108 LSA) with long runners will keep VE strong in the midrange and still breathe to ~6000. It points to VE ≈ 0.90–0.95 at peak for a well-sorted NA 2056.

Sizing at 6000 rpm (single throttle)
Using the airflow method and a sensible WOT target velocity (250–300 ft/s) through the throttle:
VE 0.90: 39.3 / 37.5 / 35.9 mm (250 / 275 / 300 ft/s)
VE 0.95: 40.4 / 38.5 / 36.9 mm (250 / 275 / 300 ft/s)
Add ~10% area headroom for shaft/plate, filter, and real losses → diameters rise ~5%:
VE 0.90: 41.2 / 39.3 / 37.6 mm
VE 0.95: 42.4 / 40.4 / 38.7 mm
Recommendation (for your combo)
Aim for a ~40 mm single throttle (39–41 mm window).
Pick ~40–41 mm if you want a touch more low/mid torque and gentler tip-in with the long runners.
Pick ~39 mm if you want a bit higher airspeed and crisper pull right at 6k.
Quick setup notes
Keep throttle bore ≈ runner/port CSA “projection” to avoid a step. A slight inlet taper toward the plenum helps signal and atomization.
Long-runner plenum: don’t undersize the throttle; the runners already boost velocity. Your ~40 mm choice won’t dull response but will avoid top-end choke.
If you share your runner inner diameter/CSA and plenum/throttle neck geometry, I can double-check the match and fine-tune the exact bore.

[Geezer914]

I am running a 2056 with Ljet FI. Installed a 50mm Vanagon modified throttle body and modified the snorkel on the air cleaner box. Moved the large wheel one notch richer on the air flow meter. Running HAM heads and 9.0 CR. Runs like a bat out of hell!

[rfinegan]

Thanks all for the insights and advice as i move into this new phase of my 914.... I will of course thread my adventures here and youtube as I move forward


Kind regards

-Robert

[bdstone914]

@914Sixer

' date='Sep 20 2025, 02:32 PM' post='3225008']
Take the 1.8 runners and drill 3rd center hole. You should be able to bolt on 2.0 spacer block on and use it as a pattern for hole.
[/quote]

U don't think that will work. The two holes at the top are difference distances between 2.0 and 1.8 patterns.

[914Sixer]

Yep, that was all read pointed out, my bad.