Real world experience 2270 / Heat / Stock FI ??

[999argonaut]

Gentlemen, some advice please and hopefully some real world experiences to make decisions regarding my type 4 rebuild. It's a stock Porsche 2.0L with L-Jet FI living in my 912E.

The crank is shot (bent), cylinders rusted, lifters damaged, crankgear damaged and more. In short I need to get a new crank, replace pistons and cylinders and the entire valvetrain. I have not done my shopping yet so everything is game.

I would like to use this opportunity to give the car a good performance upgrade (ie 120-150 hp) but I would like to keep my heat exchangers and FI system. Realistic or not? I dont mind modding things for performance purposes but obviously dont want to build a timebomb.

I guess the well travelled road would be to actually go for a 2056 cc build. 96 mm Keith Black pistons, 71mm stroke crank (maybe go T1 journals and rods to reduce weight etc), Jake Raby 9590 FI cam kit, 1.7L rockers, collect my 110-115 HP and call it a day (exhaust is a Bursch system). However, for pretty much the same money I can also go for a 78mm crank and go to 2270.

Has anybody build this sort of (mild) 2270 combo succesfully? What cam and other mods where needed to make it work with heat and L-Jet? I am reading air intake becomes important so maybe a larger (vanagon?) or smaller (2.0L bus?) depending on who you ask throttlebody / plenum setup is needed. Fuel delivery same story (ie balast restrictor on the CHT for extra fuel delivery?, potentially more fuel pressure (although stock is at 35psi for this car), cam not too crazy because of heat management issues (so which one then?) ? Have experience, warstories, specs ? Please share!

Thanks, Jason

[Clatter]

My experience with L-jet is with a 1971cc bus 2.0.

It was built with specs taken after Jake's 'Camper Special'; 42 x 36 valves and a 9550 cam (similar to a Web 73)
pretty much stock other than that, heaters and a header, plus a Mallory.

When you put even this mild of a cam on L-jet, things get wonky.
The reversion caused by cam duration/overlap tends to disturb the AFM.
At idle, the AFM flapper door gets flapped back and forth far more than with a stock cam.
Because the computer is designed to interpret fast, large variations in flapper door movement as an acceleration event,
It gives a squirt of fuel similar to the way an accelerator pump works on a carb.
This is a deliberate effort on the part of the engineers at VW to make the FI more drivable,
As a hesitation off idle was always complaint people had with FI.

So when the flapper door gets flailed around by the big cam, it causes the motor to get far more fuel than it wants.
Couple this with a need for more fuel when at WOT to feed a big engine, and you make the problem worse.
Tricks like more fuel pressure, bigger injectors, etc. only make the problem worse.

I used the '79 CA set-up with O2 sensor to try and fix this issue, and this made it run clean right at 14.7:1 AFR (stoich)
But stoich is hot, and hot is bad, and there's nothing to be done about it, other than ditch the O2 sensor.

So,
Long story short,
L-Jet doesn't have enough adjustability to deviate much from stock.

Go with carbs or PEFI if you build a big motor.

[Clatter]

IIRC, Jake had (has?) a version of the 2270 for heater boxes.
It was (is?) called the 2270-145 or something like that, because it made 145HP.
There was also a 2270-175 or some such for use with a proper header.
You would need the larger 2.0 914 heaters for this - perhaps the 912E headers are similar size?
So, the heaters are likely to be Ok if you keep the combo mild.

IIRC, your 912E has the same plenum and runners as the 914 2.0 - the biggest they made for these motors.
So, if you converted to MS or some such, perhaps you could still have a set-up that looked like stock externally,
Used the stock L-jet TB, injectors, etc. but, had the programmability to make it all work right.

It's do-able. But not using a flapper door and L-jet computer.

Sounds like a fun project!

[999argonaut]

Thanks for the replies so far. AFAIK the 2270 kits that Jake developed have all been designed around carbs and aftermarket FI. I think he did test versions with stock FI and considered it too risky. I don't know what those risks where but I am guessing heat management and a lack of L-jet tunability will come into play without mods. Any success stories otherwise I guess I need to start doing some reading on aftermarket FI setups.

[aircooledtechguy]

Just as Clatter said, the stock 912E L-jet isn't going to cut it. Also the intake manifold and throttle body will act as a governor just when you begin to have fun. A late Vanagon plenum and TB will actually flow better than your stock TB/plenum and may work out, but I still would go with ITBs or build a custom plunum with maybe a Jeep TB. Then Megasquirt it and be done. Drive happy.

Stock 912E HE should be just fine. They are the same size as the SSI 914 2.0L HEs and those work well, so. . .

[Piledriver]

The late bus plenum is the same size as the late vanagon, but either will need widened and modded a bit to line up with the 2L Porsche runners.

Would probably make for a nice torquey driver but would limit top end fun, depends on your driving preferences.

Shortening the runners a couple inches each side and widening/enlarging the plenum further would probably aid top end considerably, but the vanagon plenum is preferred for widening as the case mounts don't work on a t4 anyway.

The Vanagon TB is 50mm but they often tend to be in sad shape as the aluminum butterfly and bore is effectively the thrust bearing, definitely an issue on the automatics as a heavy linkage to the trans gets supported by it on one end.
(can usually be cured, but try to find one from a manual if you go there)

[cgates30]

I am also planning a rebuild of my stock 2.0L in a 912E. My plan was to stick to 71mm stroke, but to go with 96mm flat top pistons to bump up to 2,056cc and to use the 9590 cam kit from the type4store. Are you guys familiar with this setup and how it will run with the L-jet AFM FI? I don't want to get into the wonkiness clatter mentioned above.

I enjoy having a little fun, but really its a street/driver car, so 115HP sounds like fun over the original 86HP (34% increase in power!).

[aircooledtechguy]

The late bus plenum is the same size as the late vanagon, but either will need widened and modded a bit to line up with the 2L Porsche runners.

Not true. The plenum only needs to be clocked CW approx 15 degrees on the fwd mount by replacing the case bolt with one that is approx. 3/4"/1" longer. This enables you to use 2-3 M8x1.25 nuts between the case and the plenum mount. Tighten both mount flanges and you've clocked it enough to line-up the runners. Now you can use fuel/oil safe hose from FLAPS to connect the bus plenum to the Porsche 2.0L runners. Easy as pie. I've done this several times with excellent results on larger motors.

[raygreenwood]

The L-jet itself is NOT the limitation. Virtually the same volumetric AFM with tuning tweaks to spring wheel and flap and are used all the way through 5.0L V-8's.

And yes...unless you do serious manifold tuning...you cant just slam on a cam because it fits your lift and duration needs. Reversion is only caused on a plenum system...by a combination or poor plenum design and lobe center being way out of line of a flap based airflow meter. Less problems with hotwire ...but still some. The lobe center has to stay in the 104-108 range for L-jet.

The big issues are as mentioned....the plenum and runner volume sizing and the TB that feeds it.

The basic L-jet can be made to feed virtually any sized engine. As far as the electronic part of the system itself goes....its just a matter of injector injector sizing and fuel pressure.
But...you still have the cam limitations you have to stay within. That means that any real increases are mainly in displacement....which has its own issues with plenum, runners and TB.

If you are willing to invest that much time....just in tweaking out the electronics (you aare going to have to fab for manifolds in the worst case or mix and match at best....either way) with less choices in cam.....you might as well go to aftermarket programmable injection and get exactly what you need with a much wider choice of cams.

Upgrade the ignition while you are at it. Ray

[Piledriver]

Speaking of ignition....

Just pulled these out of my T4 powered squareback last week after ~80K miles.
Ran great at WOT but started a little hard on two cylinders lately and wouldn't pull 19:1 cruise AFR anymore without lean surges. 17:1 was fine.

Iridium Pulstars: (no longer made, they use larger Inconel electrodes now)
Plug gaps were just shy of 1/4" on the two with the burned back/recessed in insulator center electrodes, and ~.200 on the other two.

The deposits are clean/white all the way down, I switched from E85 to straight gas (~E8-10) about 3 weeks ago, so they look tan on the surface.
No idea what the deposits are. Not burned oil at least.

Popped some BP6ETs in now, all 4 hit/started on ~the first rotation.
Thought I had developed a vacuum leak.

LS2 coils rock.

80K-irridium-plugs.JPG

[999argonaut]

Hmm...I like the idea of the Jeep throttle bodies (I am guessing the 2.5L ones not the 4.0L)..cheap, plentiful, all the right stuff already plugged into it for aftermarket FI.. what about the plenum though..anybody done this for real?

[Piledriver]

what about the plenum though..anybody done this for real?

Nate and I have both done it "for real" or we wouldn't have posted.
This is not TOS or vwvortex.
(most folks here use TOS as a shorthand for That Other Site AKA "thesamba")

I widened/tweaked mine to meet/line up with the shorter 2L Porsche runners, and Nate offset the plenum mounts and used rubber hoses to connect.
I wanted a bigger plenum and shorter runners anyway.

I didn't change the TB though, 50MM is enough, in fact i think i put the 45 back in as the Vanagon TB leaked by too much for a decent idle on a small motor. The TB size DOES directly effect the plenums tuning though.

The Vanagon 50 and some late LJet TBs have units have the benefit of an idle and (sometimes) WOT switch, so the shaft is already made for a TPS. Even the earlier ones can be easily modded to take a TPS.

The TPS isn't strictly required, you can use MAP only for the accel shot.
Makes setting up the idle logic much easier though.

Now has an AEM (reboxed K&N, which is IIRC made in partnership with AMSOIL...) dryflow filter now as of today, also using a Vanagon fan shroud now.

Pic from install ~5 years ago, note no throttle cable yet.

These dry synthetic media filters are actually awesome as filters as compared to oiled gauze.
(Really, almost anything is a much better filter vs. oiled gauze, including an oil bath or paper)

I'm using a Vanagon 3 wire IAC in the original location now and ditched the VDO pressure sender as it was horribly inaccurate and eventually leaked a little at the crimped seam. Not needed once you know you have good pressure.

The distributor now has a missing tooth wheel and hall sensor to allow sequential spark/fuel.
The one in the pic is a late vanagon unit modded to provide just a sync pulse.
The distributor cap is just a dust cover. The non-missing tooth crank wheel is the flywheel in the pic.

[999argonaut]

Nice work !!

[raygreenwood]

yes...nice work! And I totally agree on your thoughts in your post.

The biggest problems with plenum systems is people not understanding how the volume works with the TB.

Most use "carb" tuning frame of mind when selecting a TB. It needs to be big enough...but no more. In fact...from my experience, installing a TB that is too large...actually creates a weak but significant form of reversion. Its an ugly harmonic and a fluttering of the vacuum signature at idle and under moderate load...disappearing at higher rpm. It makes for poor throttle response off the line and in the mid-range. Yes...its part of the normal expected airflow velocity drop expected with too large of a TB....but it causes problems in a plenum system that it does not on ITB's

When the TB is too large, as each cylinder ingests air...and its pulled from the plenum....the TB admits replacement air. The TB needs to be small enough in size to keep that air at a relatively constant velocity during the ingestion/intake time. Hold this thought/mental picture for a second

Because of timing, elapsed time and overlap of four cylinders....when the intake valve slams shut...most people assume that the shock wave traveling back up the runner from that column of air stopping its forward motion....just instantly creates reversion like you see in a carbed system. It does not.
This is because with intake overlap and the time lag between them.... there will be another intake valve opening usually diagonally across the plenum. The reverted air that backs into the plenum has a place of lower pressure to push into other than out the intake TB.

When that next intake valve opens it create a relief area in the runner for reversion air from the closed intake valve and runner.....which pushes air back into the plenum ....which squeezes air into the runner with the open valve.

But when...because of an overly large TB....the pressure differential just inside the TB throttle plate.... can be lower than the pressure differential/depression of the diagonally adjacent runner with the next valve opening point.
When this happens you get a pressure stall just inboard of the TB. This stalls allows compressed feed air from the runner with closed intake valve.....reversion...to squeeze towards the TB....until the depression of the drawing runner is high enough to pull air in its direction.

You can see this with a "good" vacuum gauge when its plumbed into the right area of the TB. Going to a slightly smaller TB can usually eradicate this fluctuation and the resulting turbulence caused.

A good way to keep a slightly smaller TB from becoming a restriction at peak rpm....is with carefully added plenum volume....or lead-in tube volume between TB and plenum (a lead-in tube by the way also helps to quell the throttle plate turbulence plume and moderate any remaining TB reversion). .....Not so much by changing runner volume...as runner volume has enough issues....its got to reach long distance on our engines while not becoming so high in volume/diameter that it stalls velocity or so narrow in diameter that it creates drag and chokes volume.

Pile's method is a blend of both. Expanded plenum volume....and the runners dont have to reach so far. Ray

[Piledriver]

Excellent description, Ray.

I wanted to ~match the Porsche 2L plenum volume/TB length as its just about perfect mathematically for the desired power range, and the very short "TB" length at the plenum input (sans the long TB<>air cleaner intake tube a Bus has) and shorter runners shove the plenum/manifold tuning uprange quite significantly.

Jake long ago proved the side inlet plenums outperformed the top inlet 912/914 plenum, so I decided to combine the best of both.

It also fits in my Squareback.

I get pk tq@~3200 and pkhp at ~4400-4600 with a web 73.
The intake tuning has far more effect on those peaks location than the cam AFAICT..
A longer cam would slightly move the tuning, the top end would make more tq/HP, but probably not at a much higher RPM.