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?

ive been told that thebig bore 2056 cc motor (96 mm pistons, stock strck
) is about thelimit for stock 2.0liter d-jet tweeks of the pressure sendor will be required to run the 96mm pistons.

NOOOOOOOOOO

oh

2056 with MPS modification is about the limit to a 2.0 d-jet

Maybe Andy will chime in. He has a very nice red 914 with 2.3 TIV and a tweaked D-Jet FI system. I know he did not build it himself. He uses it for cruising and AX racin and was always happy w it when I saw him

I would like to hear from Andy or anyone that has tried this mod. Thanks, Ray

Yes it works.
Keep the stroke the same, 71mm and put in the 103mm jugs.
Keep the camshaft the same...
You can change the heads to 46/38mm valves for a bit more flow.
You will need to tune the MPS.

It works.

Rich

Thanks for the info Rich. I was sure someone has done this. Just wanted as much input as possible from other 914 owners before going ahead with this rebuild. Thanks, Ray

since you are increasing displacement by nearly 1/2 a liter, don't you need bigger injectors?

Zach

Will increasing the fuel pressure provide the extra gas that would be needed?

You cant change the type of manifold pressure (short stroke and stock overlap) but you can change the volume.

You will need a way to tune your mps when you are ready.

Rich

I've tuned the MPS on several of my other cars so that's not a problem. Just hoping that the end result will give more go power without any major glitchs with the FI. Some people would just put on carbs but I've kept the FI on all of my 914s because it works so well.

Then Jake Raby will come in and tell you 2056 is the limit ...

Welcome in the arena ...

The french guy ...

150-165 hp is the max D-jet really....and that would be with a 9.5:1 CR....
If you do that, its gonna get hot, so plan for the heat.

Manfold pressure is how drag racers use fuel injection, so there really is not an upper limit....but with our Djet you are dealing with fixed air/fuel maps that are hard coded.

You can use aftemarket FI and get alot better results, but you can also restrict the build to use Djet and that can be fun.

Same cam is the key. And that really sucks, but thems is the facts.
Same stroke is the key.

This leaves alot on the table for potential HP. but its still a fun car to drive
Get a header also...

Rich

Speaking of camshafts-------------------------I've used Web-Cam grind #73 on two of my fuel injected cars with good results and plan to use one on this motor. Hoping to keep the CR at 8.5:1. And yes----I've read that it'll run a little hot.

Why would you handicap the motor? I realize it is a little more money, but in the grand scheme of things, a more modern FI unit will make the car that much more enjoyable.

There are really no limits in engine maniplation. The difference is what can SAFELY be done without losing the entire investment or creating an engine that does nothing well except idle. Been there..

Smart people won't try to build an efficient D jet engine above 2056cc, beyond that the compromises are great.
Projects that begin with compromise, end in demise.

My engine is a 78 x 96 with a mild webcam for FI engines. It has been together and running extremely well for 10 years. I've been driving very hard at autocrosses for 8 years and it doesn't even leak a drop. And yes I built it! It does not run lean anywhere. No it does not make as much horsepower as Jakes, but it is a torqy SOB and it was probably less than 1/3 of the cost of his. I built this engine to pass smog and it did...barely. The compression is around 8.1:1 The fuel pressure is around 36 psi. Early 2.0 manifold pressure sensor/injectors (supposedly flow more gas and cheaper at the time). Stock rev limiter, larger or bored out throttle body. The big deal is to trick the brain into thinking its cold outside, so put a resistor inline with the head sensor. Mine took about 400 ohms resistance to accomplish this. I determined this with an O2 sensor in the exhaust and later it was checked on a chassis dyno. Do a search it has been discussed here before.

Thanks for the info Andy. Everyone has been very helpful. Think I'll go with the 96mm pistons and use the Web-Cam grind # 73 that I've use in my other engine rebuilds. Nice to hear from someone who has put one of these together himself. Ray

Of course Andy built it himself!
One day, I will build one too. Just waiting for the 1.7 to kick the bucket. If I get from the AX track to Sears Pt big track this year, that should speed things up

could have said your viewpoint without throwing stones.
I never considered myself stupid.

Its built like this for a number of reasons...smog, PCA classing,,,,etc etc.
The compromise may be less HP, but the stock motor and a 2056 is also a compromise if we consider that Jake can and does get 200hp or damn close to that out of a type4 motor.
Anything else is a compromise...

We all have our opinions and I could not find any data on someone doing this, just rumors.
It works, plain and simple.

Look at using a 411 MPS with a single manifold, its alot easier to tune, looks the same, and you can tune it perfectly.

Rich

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~

The biggest compromise for some is money!

Which is the exact reason they don't need to do the job twice, or three times.

Hey Mr. Self Righteous, your way is not the only way. Lots of other people have had success and quite a few of us nail it the first time. Recognize that. Accept it. Jake you are incrediblly talented and we value you as a knowledgeable resource, but stop crapping on the rest of us that have been successful.

What about using the L-Jet?
Is it better for big engines?

I'm looking at rebuilding an engine myself and have both D-jet and L-jet available. Which one should I use (don't want carbs)?

You have perceived what I have said incorrectly, but that may be my fault because it was written incredibly clearly to get a point across.

The original poster asked if the stock system could be used on a larger engine, something of 2.4 liters of displacement. The direct answer to that is yes.

The best way to explain what the person doing the modification may experience would be: "Results may vary"

One of the only times that I have failed when I put my efforts into getting a result was working with the constraints of stock FI. I see lots of people make lots of mistakes, these mistakes vary from internal design that makes an engine impossible to tune, to improper placement of components that cause their car to burn to the ground. We are generally a last resource for people that can't figure it out and that gets really old, especially when people call up down and out having lost thousands of dollars and have nothing to show for it except an engine that won't run. If I have to hurt some feelings to help people see that they should put more consideration into their project before opening their wallet, I am willing to do that.

I used to have a Murphy's Law calendar in my office. My favorite one was this, "It never fails, that when you make something absolutely, 100%, crystal clear; you are going to confuse someone!

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...

Hey Rich: ok that sounds interesting,the 411 MPS. How is the 411 MPS different than on our 914's? I thought the 411 motor was really close to the 914 motor, do you get better adjustment range with the 411 MPS? or ?????

Certain early longsnout MPS's have more range plus using a late cover gives you the most range of adjustment...

Certain early longsnout MPS's have more range plus using a late cover gives you the most range of adjustment...