2.0 Rebuild Advice Needed, 2056 or 2270? Options

[r_towle]

Djet can go up to 2.4 liter with the 71mm stroke (stock) crank.
That is 103mm pistons.
It cannot deal with a longer stroke.

rich

Rich, just a curiosity, why can't the Djet system deal with a longer stroke?

If the capacity of the engine is the same why would it matter whether it was because of a larger diameter or a longer stroke, the FI is most concerned with the flow of air into the engine? I would expect the flow rate of air into the cylinder to be essentially the same at a given RPM if everything else was identical.

You can see from the graph that the change in volume (flow) into cylinders follows the same basic path. (the 103 mm x 71 yields a larger displacement than 96 mm x 78.4 but even if it's changed to 101 mm it still follows approximately the same curve) You can see how the rod length affects the curve by essentially flattening it as length increases.

Again I have no idea, but this surprised me.

Andy

Dunno, but btdt with both, one can be tuned, one can't
It's measuring manifold pressure, not air flow on diet.
I tune them on the road with a/f gauge, and seat time, up and down the roads while tuning.
A lot less precise than all the data collecting, but it work as well as it always has, and the motors run great.

Not looking for the ultimate hp , just a decent motor that does not require 2k worth if fuel injection, or a homemade mega squirt setup....

I have heard that ljet can do more, and air flow is used on the 944 and 911 with less of the issues that manifold pressure introduces to the whole scene.

I heard loads of myths when it came to what diet could do, and I , like you, could not understand why it would not go bigger.
So, I did it, more than once.
It's fun to try for me, and I am now breaking in my motor on carbs before I tune the djet for it...

I have built two other ones and tuned them, I learned a lot about wht works on these...and my motor I tried a different cam to see if I can get around another djet issue with overlap and flutter in the manifold...
Honest I don't think this motor will be able to run djet, but I am going to try anyways...

Rich

[Jake Raby]

Adding all that displacement when keeping the stock intake characteristics is just one huge compromise no matter how you are fueling it. I found long ago that the stock intake system is done at 2.1 liters.

Yes, anything will work, but whats efficient is another story.

[r_towle]

I recall some testing that showed the intake runners and throttle body would support up to 2.4 liters.
It was quite a while ago when I looked really hard at this, but one of our resident science guys did some calculations and the intake system will support the airflow.
Maybe someone could work on those numbers again that can remember thermdynamics..


The djet may be the issue that you experienced, but I believe the physical intake system can handle the airflow.

I remember you tried and found the system to be to weak for your goals and what you want to build.

For me, the goal was different. how big for how little money was the objective...I believe I have achieved it, now I am curious to see what I can trick Djet into doing...
I have read to many stories about Megasquirt and how it does not seem to work right...or its finicky, or some other reason it cannot be tuned...
I figured, why not take the Djet system to the next level.
Heck, its the preffered method for alchohol based drag cars...so maniold pressure can and does deal with large aggresive camshafts, and lots of overlap....but it may just be a matter of some technology to smooth out the curve properly.

I have found a few manifold pressure sensors, but not like the one we use, something more modern.
Just a napkin idea that another buddy and I came up with on how to replace the MPS with a more modern setup, and have the ability to tune it for a larger motor...

I know your motors put out the maximum...
a 2.4 pushing 150hp, without getting to hot, is a fun car.
Not looking to break the bank, do external cooling, nor get near 200hp.
Looking for a fun car that can be streetable, fun at an autox, and a bit unique.

Heck, if I did not like tinkering, I would sell the car.


Rich

[Jake Raby]

how big for how little money was the objective...

Of course you were.

[r_towle]

Not everyone needs to follow you jake, we all have different goal and your way is not the only way.
Fun to have you back, but don't start bullying as soon as you show up.

Rich

[gothspeed]

To the OP, a 2056 or 2275 each have their virtues and possibilities, mostly depending on what fuel system and head/cam combo you plan on running. I went with a 2056 only because it was my first type 4 and it 'seemed' more straight forward. Maybe in the future if time and money allows, I will look into a 2275. (IMG:style_emoticons/default/idea.gif)

That said, I will share what I did on my 2056. I added counterbalance weights to the stock 71 mm crank. Used H-beam rods (5.375 length if I recall correctly) and the rotating portion of the bottom end was spun balanced as an assembly, with the pressure plate installed. Reciprocating parts were matched for weight and the rods end to end balanced. All galley plugs were pulled, galleys cleaned then tapped for tapered plugs.

The heads is where most of my work was done, I used 2.0 heads and went with bigger valves, 44 mm intake and 38 mm exhaust (stock 2.0 is 42 and 36mm). I enlarged the intake ports to just shy of 37 mm and smoothed them from the back of the intake valve, through the isolator block and through the intake manifold. The cam I chose was a Web #270 with .473" lift and I think .288" duration, on a 108° lobe center. Used swivel adjusters, 44 mm webers and 8.4:1 compression among other mods. I hope to go with ITB EFI in this engine in the future too.

So whatever engine size you decide, I think a well thought out and efficient motor is more important than displacement alone. And if you are going with stock injection, I would say stick with a 2056cc or even stock 1971cc. Then just focus on the heads (valves), cam and compression for the 'mod' portion.

Good Luck on the project! (IMG:style_emoticons/default/beerchug.gif)

[Jake Raby]

Not everyone needs to follow you jake, we all have different goal and your way is not the only way.
Fun to have you back, but don't start bullying as soon as you show up.

Rich

I don't agree with increasing engine displacement by 20% and expecting the stock intake to feed the engine optimally, so I am a bully?

Classic.

Oh well, I've been called worse, and they were probably right.

Outta here, I'll try again in about a year.

[rwilner]

I have read to many stories about Megasquirt and how it does not seem to work right...or its finicky, or some other reason it cannot be tuned...

Rich
As you know from my experience -- MS isn't plug and play, but it's the most cost effective way to squeeze out all the power from our engines IMO, simply because it can adapt to various configurations and be tuned....especially if you control fuel and spark.

Now of course I am no expert, but once it was running (with help from you, Chris, and Mark), it was running better than my tired old D Jet ever did.

/hijack over

[914_teener]

I have read to many stories about Megasquirt and how it does not seem to work right...or its finicky, or some other reason it cannot be tuned...

Rich
As you know from my experience -- MS isn't plug and play, but it's the most cost effective way to squeeze out all the power from our engines IMO, simply because it can adapt to various configurations and be tuned....especially if you control fuel and spark.

Now of course I am no expert, but once it was running (with help from you, Chris, and Mark), it was running better than my tired old D Jet ever did.

/hijack over

Hmmm. Interesting as ever here.

I believe the OP is talking about Volume and Jake is trying to address VE.

The OP spreadsheet does not address VE which has a lot to do with the hard map VE table on the D-jet board. It is one thing to due a volumetric analysis as opposed to an integral analysis which would measure all the aspects of the given induction system.

I think Rich (T) is saying is that it will run...maybe just not very efficiently...I might add....respectfully. Can't address why the stroked motor won't work very well with D-jet but you can do some integral math to figure it out once you really understand how D-jet works. My calculus is a bit rusty.

Sounds like Jake has already done some quantitative research on the VE of the type IV and knows what is optimal.

With respect to MS.... I have been reading some threads recently and without doing my own research on MS....sounds like some are having trouble understanding how this is accomplished...(including myself) and spending a lot of time tuning it later without a core understanding of how to map the VE curve and then fine tuning it.

Like Rich said there is no out of the box solution.

My two bits...however I am planning my own build so I always can learn from others. (IMG:style_emoticons/default/sunglasses.gif)

[rhodyguy]

1. dave hunt had nightmares trying to get even a modified djet system w/a bigger tb and megasquirt to function in a 2270.

2. no one has mentioned the need for a better exhaust system than heat exchangers to get your moneys worth out of a 2270. whichever path you choose on that bring $$.

3. you can build a 2056 for FAR less money. still buy the right premium heads for your application.

4. people seem to treat jake rudely if not like a tool. then a valuable asset has had enough and plays elsewhere. unfortunately.