Type 4 FI, How big Options

[r_towle]

So how big ahve you seen or heard of a 2.0 liter type 4 with a tweeks stock FI setup???

I need to know specs, I know 2056 works, I feel that it could go bigger, I am thinking 2.2 possibly, with a higher CR and a web cam, ported/polished heads.

I would like to hear Jakes real world trials to see how far he has gone, I know he has tried big displacement with the stock FI, I just want to know where the line is??

On that topic, how about 2.4 liter using the 4.8 liter mercedes injectors (they fit and have the same voltage requirements, and an old porsche race team mechanic said he had done it before)

Any thoughts?

Rich

[fiid]

So how big ahve you seen or heard of a 2.0 liter type 4 with a tweeks stock FI setup???

I need to know specs, I know 2056 works, I feel that it could go bigger, I am thinking 2.2 possibly, with a higher CR and a web cam, ported/polished heads.

I would like to hear Jakes real world trials to see how far he has gone, I know he has tried big displacement with the stock FI, I just want to know where the line is??

On that topic, how about 2.4 liter using the 4.8 liter mercedes injectors (they fit and have the same voltage requirements, and an old porsche race team mechanic said he had done it before)

Any thoughts?

Rich

My humble opinion:

I wouldn't go bigger than a stock with a D-jet. The Djet is measuring the manifold pressure and making a hardwired guess about how much air that means about how much fuel to put in. A bigger engine is going to have more suck, so I'm not sure it would compensate correctly for a bigger engine.

The L-jet might be able to take it because it is measuring the weight of the air going into the manifold, however the L-jet seems to be less, not more popular with 914 folks.

If you want to FI with a big-4 I would use the D-jet manifold, and injectors, bore stuff out a bit and run a megasquirt. It's not too hard to set up and if you can get access to a dyno, or a wideband O2, you ought to be able to do better on performance than the carb guys with the same engine.

As for injector sizing - there are calulators out there that will help you figure it out. The link below should help - just set the turbo boost to 0psi and the Intercooler efficiency to 0, run at about 75% volumetric efficiency at the redline rpm. Fill out all the other fields, for bore and stroke etc, and it should give you an injector flow rate. The Meqasquirt FAQ has a table of different injectors, so that should help you source them.

http://not2fast.wryday.com/turbo/glossary/...urbo_calc.shtml

I believe the 2.0L injectors are a little oversized so they might work fine. I have also heard of people using Subaru injectors. I think you'd be pushed to get an injector that is too big - as long as you can psysically fit it, and it's from a vaguely similar setup. Basically - the bigger the injector, the less granularity you have over how much fuel is going in. The fuel amount is varied by opening the injector for shorter or longer times, and most systems only work to a certain timescale. There is a high-resolution version of the megasquirt software that you could go to if this is a problem, but it won't be if you pick injectors that aren't way oversize.

Fiid.