vw sedan 1600i (Mexico) to 1776cc?

[juanpablo1969]

Hi guys;

I´m new in Shoptalkforums;

Installed 4.12 R/P in my mexican Vw bug 1600i 1994 (efi), I want increased to 1776cc for add torque; but my question is;
This new size works with the original EFI system without modifications?

Thank and regards.

[juanpablo1969]

???

[Marc]

No experience here with the Mexi F.I. but I would expect that to be within the realm of possibility. I've run L-Jet and D-Jet on 1679cc and both required a little tweaking to get right (L-jet's easy since you can simply use the components from a Type IV engine of similar displacement). That's a 6% displacement increase, you're contemplating 12%.

[Piledriver]

There are few folks here who have worked with the late Mexican EFI in its original form.
Typically they put a Megasquirt2 or microquirt on to control things using the original TB/manifolds, this is a fully programmable engine management system. That can work with much larger engines, even supercharged, or E85 fueled.

I personally have not worked on the Mexican system, but I have worked on L-Jet and digijet, so I'll try anyway...

Its essentially an L-Jet or Digi-Jet (decendant of L-Jet) system, and uses an AFM to measure flow, so SHOULD have some headroom to work with a slightly larger engine with a stock or near stock cam. The AFM won't tolerate a wild cam, or really even many pretty mild ones, just stock or close, high ratio rockers are fine, its ~just the valve timing that's critical.

If Digi-jet, there may be an aftermarket "chip" for it but that would still be somewhat engine-specific.

Going to 1776 raises the compression a little, may required better grade of fuel, maybe not.
The AFM has an internal adjustment or two, but Google will have to guide you there, don't mess with it unless required.
An adjustable pressure regulator and "ballast" resistor in the CHT sensor line are traditionally also used to fix L-Jet on larger motors, by feeding a % more fuel in an adjustable manner.

I would borrow or buy a WBO2 setup to make sure its isn't running lean at WOT, or at least see if you can monitor the factory narrowband O2 lambda sensor with a DVM to make sure it doesn't go lean.

The engines ECU also uses it for mixture correction once warmed up, so you can't just unplug it, you'd have to tap in to the wires to see the voltage, it reads either rich or lean, the ecu will actually fiddle the fuel so it switches back and forth across stoichiometric AFR. (lambda=1 or 14.7:1 AFR)

This assumes the factory sensor is still good... They have a limited life expectancy, and can be easily killed if your old motor was burning oil etc. A modern wideband system as a replacement may be cheaper or at least a better plan.

Many wideband O2 setups have a "fake" narrowband output.
(its not really "fake", it's calculated, coming from a much better sensor) to keep the factory ECU happy.

Some of these have programmable "fake" NB outputs so you can run leaner or richer than the programmed AFR at your desire.
Normally they just report what a narrowband sensor would have based on the widebands AFR results.

I personally have had great results with the units from 14point7.com.
Also some of the least expensive setups, and one version is the only Open Source design and firmware WBO2 I know of if you are into that.

IIRC the std narrowband will read about .350-.500v at lambda=1

[juanpablo1969]

ok...my 1600i use a 25 pins digifant, very similar to mexican vw golf, jetta, etc.....I have a wideband, maybe install a second port in the exhaust for check at WOT.....

[Ol'fogasaurus]

For torque, why not just stroke it. Stroking usually will give you a bit more bottom end.

Lee

[Piledriver]

ok...my 1600i use a 25 pins digifant, very similar to mexican vw golf, jetta, etc.....I have a wideband, maybe install a second port in the exhaust for check at WOT.....

For torque, why not just stroke it. Stroking usually will give you a bit more bottom end.
Lee

Stroking it or boring it out == bigger motor either way.
The key is if the stock EFI can deal with it.

Stroking it also means better rods for any longevity, and just generally a more complicated/expensive engine build.

I'd go 1835 with the thickwall 92s IF I was certain the stock EFI could deal with it, or amenable to smacking in a Microquirt and a 4 tower waste spark coil. (around $400 as you are already setup for EFI)

If you already have an aftermarket WBO2 sensor and controller you are most of the way there.
What model of wideband?

[juanpablo1969]

AEM wideband http://fast5.co.uk/index.php?route=prod ... duct_id=57
I have experience in carbureted aircooled engines modifications ...... do not understand much of EFI systems (basic concepts only).....

[juanpablo1969]

when you said; "An adjustable pressure regulator and "ballast" resistor in the CHT sensor line are traditionally also used to fix L-Jet on larger motors, by feeding a % more fuel in an adjustable manner"
The idea is that the ballast resistor in the CHT sensor sends a decreased signal so that the mixture is richer?
But this will depend on the results n WOT true?
The 25 pines Digifant uses a sensor map like the one you mentioned?.

Thanks and regards.

[Piledriver]

when you said; "An adjustable pressure regulator and "ballast" resistor in the CHT sensor line are traditionally also used to fix L-Jet on larger motors, by feeding a % more fuel in an adjustable manner"
The idea is that the ballast resistor in the CHT sensor sends a decreased signal so that the mixture is richer?
But this will depend on the results n WOT true?
The 25 pines Digifant uses a sensor map like the one you mentioned?.

Thanks and regards.

Yes, either makes it richer

Have no idea on the Digi ECU as they didn't come to the USA like that.
Last new Bug sold here was a 79 IIRC, still analog L-Jet. Similar AFM probably, but all else different.

[juanpablo1969]

Use golf 1800i injectors can be a good decision?

Thanks for your time!

[Marc]

Don't your Golfs have CIS? Those are constant-flow, purely mechanical injectors not electrically-actuated.

[juanpablo1969]

Mexican production Golf/Vento 94/98´s aprox use the same digifant style (specific for watercooled 1800i engine) and 1800i injectors, totally interchangeable!

[Piledriver]

Use golf 1800i injectors can be a good decision?

Thanks for your time!

Same effect as an adjustable pressure regulator, without the adjustablility, so you would need both.
Also the spray pattern is likely much different: the T1 injectors are ~60mm from the valves.
The mounting is different as well, you'd have to make manifold adapters.

The Golf efi injectors are mounted much farther away, as the head was designed for long, skinny CIS injectors.
They have to shoot though a long skinny hole.
(later heads actually too small for CIS injectors and the air shrouds, you have to drill them out a little for CIS use.)

[juanpablo1969]

maybe in german models. but type1 sedan 1600i and Golf/Vento Mexican injectors are phisically the same, only change injection capacity!