1835 German plenum FI Thing

[thedrew]

Had nothing to do with either one of the guesses above. The issue was with the programming. If I ever buy another VW I'll stick with carbs

thats a shame....there are people that could have helped you work through the setup/tuning part of the setup.

[woodsbuggy1]

So sad to here that you gave up so easily. I have had great luck with Megasquirt, most problems with installs are self inflicted, I know this from experience .
Best of Luck
Kenric

[raygreenwood]

There is no such thing with fuel injection.....especially with any central plenum system.....as it being "just the programming".....or for that matter JUST the cam.....or JUST the plenum.

I have been trying to get people ro get their head around this for years.

The plenum has specific volume and resonance. ....and turbulence. ....which affects velocity, vacuum and air distribution timing. All of this affects whatever metering device(s) you use....which affects the data that is sent to the ECU......that.....affects the programming....and the programming further affects the data by changing how the engine runs.

All of this....and the effect it can generate can be leveraged and multiped by the cam, exhaust and gearing of the transmission. So yes....of the cam is too far out in lobe centre or lift.....and disturbs vacuum signature (important with a MAP based system). ...and lift and duration will affect velocity and volume (important for mass air flow metered systems)......so yes....the cam could be a poor choice.

The type 1 beetle plenum is one of the most single purpose......set up for a very narrow range of engine volume....with a shape that had very little thought given to airflow ....plenums I have ever seen.

It worked "adequately" for the engines it came with because VW compromised everywhere else.....cam, exhaust and programming.

You cannot just program around poor intake volumetrics or poor intake vacuum signature or velocity/volume.
With aftermarket programmable systems you can tune it to a great degree....meaning you can take a crappy intake with no thought given to turbulence or volume.....and optimize it to make it run the best it is capable of.....but you cannot increase its ultimate capability through software and programming.

It was a bad combo with a poor intake design. Programming will not work around that. Ray

[Steve Arndt]

Cam timing and the intake were working against it. You can't program around airflow problems. I said that a year ago.

[CBDZ]

This is interesting...

I have a 1904 with a 110 cam, running German plenum. I have a great idle.

[Jadewombat]

I'm currently tuning my 1588 with 9.0 to 1, 110 cam, 009 for spark, and 1.25 rockers. It's a pain in the butt so far. The idle has to be at least 900-1000 until things smooth out. Below that it just chugs and wants to die.

[Steve Arndt]

What does the map sensor signal look like? What numbers and how much variation?

[Jadewombat]

It jumps around about 100rpms at idle and the MAP is 50-60kpa. Attached is a log and the tune. Thanks.