Will 2.4 L engine work with stock FI, Will stock FI work with a larger bore engine Options

[reharvey]

I'm getting ready to build a 2.0 engine for my latest 914 project. I've put together several of these motors in the past but have always used the Euro type Mahle 94mm pistons. How big of a piston can I use and still retain the FI. I can make minor modification to the FI if need be. I've done this in the past. Has anyone out there try this?

[Jake Raby]

I'd be willing to bet that a 2.4 designed around the compromises associated with stock FI would make the same power as a 2056 with the same stock FI.

The difference would be the operating range, more than likely the engine with the added displacement would make poek output at an RPM thats unusable in a 2300 pound 914, it may be better suited to the application of a heavy weight VW Bus.

In the late 90s I tried and tried to make the stock FI system effective on large engines, because I knew that if I could make it work that sales would be incredible. At that time stock FI was still fitted to more cars and smog laws were impacting cars at even an earlier age.

The plain and simple facts time and time again soon pointed to the fact that I was wasting my time. I did lots of this work with no dyno, but I didn't need one to give me numbers about how bad the engine sucked.

The closest I came to making it work was a 74X94 combo built close to the way my 2056 D Jet combo is today. I designed a camshaft for that one that was basically backward from the designs I used at the time for carbureted engines.

Considering that the stock cam is inadequate for an otherwise bone stock engine (very clear when a cam change alone can net 23HP and 20 lb/ft of torque at peak with 50* cooler head temps) in a 914 or even in a VW Bus, having to use it for compliance is a huge compromise. I developed my 9550, 9560 and 9590 cams while trying to build a D Jet compatible larger than stock engine and the answer is yes, the last time I used a stock cam was in the quest to make the D Jet "Big Four" a reality.

I didn't throw any stones. What I said was meant to be fairly firm, because otherwise people won't listen to experience. I am sure you have made this work and so did I, the difference was I had something to compare it to (dozens of combinations) that proved just how ineffective it was in reality. What I was stating is smarter built engines make more power, do that in a broader operating range, drive better, run cooler, attain better MPG and do so better than a larger engine built with compromises.

Anything will run, if it has compression, spark, fuel and timing it'll run. Some engines run better than others.

D Jet proved to me to be a total waste of my efforts and I worked at it for the better part of two solid years. My current 2056 makes just under 130HP with D Jet. It has an exceptionally broad powerband and makes almost the exact same power at every RPM in both TQ and HP as my a carbureted 2056 with an even bigger camshaft and the same heads.

Yes you can make a larger D Jet engine work, but that engine will cost more money to build and it will be more difficult to assemble. The larger engine will require altered design with tall deck heights to drop the CR to a sane level, thus effecting eficiency and will require altered tuning to optimize. All of that and it may not make any more power than the properly configured, less compromised 2056 that assembles just like factory and is very simply altered from a stock state.

I realize that due to rules in racing classes and emissions that there is a desire for people to retain stock FI. In most of those classes engine displacement is also limited, so most of those people are cheating anyway and in all the instances where emissions are concerned even if the engine runs with stock FI the engine is operating illegally modified.

The question to ask yourself is: Will the engine provide an elevated level of output that will justify all the extra cost and complication?
I can guarantee you that it will not be more efficient than a properly configured, smaller, lesser compromised engine.

Remember, I am not saying this won't work, my statements are for nothing more than the stimulation of thought for those considering carrying out these types of mods centered around stock FI. Anything will run~

[Bleyseng]

I'd be willing to bet that a 2.4 designed around the compromises associated with stock FI would make the same power as a 2056 with the same stock FI.

The difference would be the operating range, more than likely the engine with the added displacement would make poek output at an RPM thats unusable in a 2300 pound 914, it may be better suited to the application of a heavy weight VW Bus.

Hmmm, a "Big Four" with 103mm Nikkies in a Bus. Now that sounds like something I would do, but would the Ljet work with it and a Raby Cam? I'd like more hp in my Westy and have a set of Nikkies on the shelf...