has anybody Mega-Squirted a Bay?

[Mr. Electric Wizard]

I have been looking for any info I can get my hands on about Bays, as I just bought my first one about a week ago, a '78 Westfalia.
I have been toying around with the idea of upgrading the L-Jet injection. There seems to be a very large learning curve to this stuff, but I just wanted to know if anyone out there has done it.

Any ideas either way?

[jeremysmithatshawdotca]

This ought to cover it for you!
http://tbone2091.tripod.com/megasquirt/
Jeremy

[Mr. Electric Wizard]

thanx...
that's actually the article that got me thinking about it...

has anybody else done this though...

[Mr. Electric Wizard]

How about any other non factory FI systems?

[ratwell]

You can't upgrade L-Jet. Besides the fact that the ECU is undocumented it's a pusled injection system and the minimum amount of time the injection can open and close has a limit. You could upgrade to injectors that put out more than 185cc/min or swap in an adjustable fuel pressure regulator but I think it's not worth the effort: just put on another FI system.

Here is a 77 Westfalia with Megasquirt.
_________________
'78 Westfalia CDN
'76 Doublecab
Read the Baywindow FAQ

[Mr. Electric Wizard]

So ratwell,
since the L-jet cannot be upgraded and you seem to know a lot about how it works, what do you think the breakover point is that it is necessary to to upgrade the FI system?
Like anything over 2.0L?

[ratwell]

Of all the available L-Jet documentation the Probst book explains the limitations well.

There are simple horsepower formulas for fuel injectors:

185cc/min for the stock injectors translates to 37 HP per injector.

That's the theoretical limit for those injectors only and seems to imply that if you replace enough parts but leave the fuel injection stock you may be able to approach those numbers with a modified bus engine. The injectors can't find wide open or the windings will melt so they typically run at 75-80% duty cycle. So that would mean 37 * 0.8 * 4 = 118 HP for a 4 cylinder.

In a bus that would be about a 30 lb/hp power to weight ratio which means there's a little potential for some acceleration.

You could switch to larger injectors (one rated to deliver more fuel at a higher fuel pressure) but you've just thrown away 5 items of the original system already. Since air/fuel ratios have to be obeyed you need to trick the ECU into delivering a smaller pulse width to the oversized injector for the same amount of air deflecting the flap in the AFM.

As far as the stock system is concerned, my guess is 2.2L is the maximum you could support producing maximum torque at 3000rpm. There are air fuel ratios to obey and the maximum fuel delivery will tell you how much air you could possibly pump into the engine and burn without leaning out.

Surveying some of the L-Jet equipped vehicles that were produced from the mid 70's to late 80's the numbers weren't overwhelming:

4 cylinders:

78 VW Bus 2.0L - 67 HP
75 Porsche 914 1.8L - 76 HP
76 Porsche 912E - 86HP

All those vehicles produced in the neighborhood of 100 ft.lbs. of torque so weight laregly determined 0-60 times. 13s for the 912E must have been embarrassing when you looked so cool!

6 cylinders:

1977 BMW 3.0i 3L - 195 HP

8 cylinders:

1984 Porsche 928 4.6L - 242 HP

Basically to get HP out of L-Jetronic requires more than 4 cylinders which is why it had a short lived run and better Bosch FI systems replaced it. Even VW replaced it with DigiJet and Digifant etc.

What's really interesting is the info for the 928. Take a look at the model years and all of the FI systems that were used and you see that US models got L-Jetronic often while the more powerful Euro models for LH-Jet or K-Jet, the latter known as CIS. The best K-Jet 928 with the same displacement produced 300 HP while the LH-Jet version produced 310HP.

There are a few CIS powered busses with both stock and modified engines and the owners report lots of torque.

My feeling you'll get more out of your engine modifications by choosing a FI system other than L-Jetronic. The bus has one set of dimensions and the car you'll steal the induction system from will have another so you've got a lot of fabricating to do.

Convinced?
_________________
'78 Westfalia CDN
'76 Doublecab
Read the Baywindow FAQ

[NeverHadaBeetle]

A new guy posted here about 2 months ago and I think he had a 2143 cc running stock L-jet. He indicated he was very pleased, but he just wasn't as long-winded and detailed with his answers. I guess we're all kind of spoiled to ratwell and Colin (a.k.a. Amskeptic) when it comes to details.

I plan to put in a 76 mm stroker crank on the next type IV I build and keep the stock L-jet. I may be naive, but I rarely get over 18 mpg so I really don't understand the theory that the L-jet can't feed a larger displacement engine. It seems to me since my stock L-jet can process a gallon of fuel every 15 miles then it has to be sufficient for a 4 cylinder engine with less than 2.5 liters. Good luck and keep us updated if you try anything new.

[Mr. Electric Wizard]

**This is all hypothetical by the way. I will probably never build a motor that would need anything more I just like to hypothesize.

So, I guess if I were to go with a different fuel injection system, there would be several items that I could still use from the stock system, and several that would need to be replaced. Going with an upgraded ECU system like say, the Megasquirt or the SDS system, you could keep the same fuel rails and some of the sensors but would need to replace everything else, such as the injectors?