Stock 2.0 w/ D-jet how far can you go?, What mods can the MAP tolerate? Options

[Brian Mifsud]

With my '76 languishing in the barn (can I call it a "barn find" if I forgot I owned it? (IMG:style_emoticons/default/wink.gif)) I haven't touched the car since my son and I overhauled the transaxle last year at McMarks in Sonoma.

I would like to get as much performance out of the stock emissions-controlled 2.0 as possible, but realize that there's not much you can get away with its brainless open-loop MAP driven fuel injection.

How far can you go on bumping displacement before the airflow vs MAP curve becomes useless?

Is there a popular cam grind that can sneak by and still work?

Is there any point at attempting to balance the exhaust back pressure by putting in a header that while with equal length tubes, still feeds into the CAT?

Many years ago, I probably new the answers to these questions when i actively drove and maintained the car. It's all forgotten, so my apologies if this line of questioning is overly redundant.

Thanks

Brian

[r_towle]

2.4 liter, 103 mm pistons works with djet.
you are still contrained by the camshaft, you really need to stay stock on the camshaft of the djet wont work.

with a 76, you have emissions to deal with also.

rich

[JeffBowlsby]

Its not MAP. D-Jet is based on a Manifold Pressure Sensor (MPS).

2.4L is the folklore, but I don't know nor have heard of anyone actually accomplishing that and that engine would be short lived.

Adjusting the MPS to function correctly on a 2056 is pushing its limits, I have no idea how an MPS could possibly get to 2.4L and still get solid AFR numbers.

[Dave_Darling]

Unless you were one of the very lucky handful of 76es to get into the exempt category the last time they changed the rules, you have to submit to the sniffer test and visual inspection. So you are stuck with the stock cam--period.

You can probably feed a 2056 pretty well with stock D-jet and still meet the emissions, assuming everything else is working well. A high-compression 2056 (96x71) would likely be close to the limit. I've heard that you can put 103s on and still have D-jet work, but I'd be worried about the sniffer test.

--DD

[worn]

Its not MAP. D-Jet is based on a Manifold Pressure Sensor (MPS).

2.4L is the folklore, but I don't know nor have heard of anyone actually accomplishing that and that engine would be short lived.

Adjusting the MPS to function correctly on a 2056 is pushing its limits, I have no idea how an MPS could possibly get to 2.4L and still get solid AFR numbers.

Is there more then a semantic difference between an electronic and analog mapping of engine work using rpm and vacuum? I have always been in awe of those engineers in the mist who pulled the d-jet off.

[worn]

Its not MAP. D-Jet is based on a Manifold Pressure Sensor (MPS).

2.4L is the folklore, but I don't know nor have heard of anyone actually accomplishing that and that engine would be short lived.

Adjusting the MPS to function correctly on a 2056 is pushing its limits, I have no idea how an MPS could possibly get to 2.4L and still get solid AFR numbers.

Is there more then a semantic difference between an electronic and analog mapping of engine work using rpm and vacuum? I have always been in awe of those engineers in the mist who pulled the d-jet off.

P.s. I find a high compression 2056 a handful to tune with stock mps and fi.

[Brian Mifsud]

MAP manifold air pressure or vacuum. MPS manifold pressure sensor...the means to read MAP... We aren't in disagreement. I've got the Bosch Fuel Injection book somewhere that I read cover to cover ten years ago. Sorry if my terms aren't correct.

Anyhow I guess nothing has changed interms of cams or engine-building since I last looked into it.

[JeffBowlsby]

MPS=Manifold Pressure Sensor
MAP=Manifold Absolute Pressure
MAF=Mass Air Flow sensor
AFM=Air Flow Meter

They are each different and work on different principles and are not interchangeable sensors or terms. That blue Bosch book explains the differences as I recall.

[Bleyseng]

Its not MAP. D-Jet is based on a Manifold Pressure Sensor (MPS).

2.4L is the folklore, but I don't know nor have heard of anyone actually accomplishing that and that engine would be short lived.

Adjusting the MPS to function correctly on a 2056 is pushing its limits, I have no idea how an MPS could possibly get to 2.4L and still get solid AFR numbers.

Is there more then a semantic difference between an electronic and analog mapping of engine work using rpm and vacuum? I have always been in awe of those engineers in the mist who pulled the d-jet off.

P.s. I find a high compression 2056 a handful to tune with stock mps and fi.

I find it pretty easy and been doing it for years...plus with a Raby cam you get 115-120hp and a cool little engine

[r_towle]

Its not MAP. D-Jet is based on a Manifold Pressure Sensor (MPS).

2.4L is the folklore, but I don't know nor have heard of anyone

Your statement is perpetuating a myth.
I DID IT, more than 7 years ago.
I have talked about it, it works.

Stop passing on this myth, it will go to 2.4 liters as a 71mm stroke, 103mm pistons.

Not short lived, but not as powerful as a 2.4 with carbs and a decent camshaft.

[JeffBowlsby]

Hey Rich, no slam intended, I just have not heard of any successful setups like this running around. Got a build thread or other reference?

Geoff...you've done the MPS's to feed 2.4L?

[JeffBowlsby]

Hey Rich, no slam intended, I just have not heard of any successful setups like this running around. Got a build thread or other reference?

Geoff...you've done the MPS's to feed 2.4L?

[r_towle]

No Jeff, and I won't.

It works, still works.

[JeffBowlsby]

You got nothin'?

How is that substantive then?

(IMG:style_emoticons/default/thisthreadisworthlesswithoutpics.gif)

[Bleyseng]

Hey Rich, no slam intended, I just have not heard of any successful setups like this running around. Got a build thread or other reference?

Geoff...you've done the MPS's to feed 2.4L?

No not yet....but I sold off the parts to build one. I just don't have the time anymore. I think it would work with a FI cam as there is enough adjustment in some MPS's. Ljet I don't think so as with my bus I am near the end of it's adjustment with a Raby cam.

[Jake Raby]

The answer to this question is greatly dependent upon what one is willing to accept for compromise and what your definition of efficiency is.

With D jet I learned that bigger is not better.

[r_towle]

Well, a djet 71/103 with a stock camshaft and stock HE was dynoed at 155 hp.

It's certainly a compromise for sure, but it's fun enough and still has heat.

Now I am changing out the camshaft in mine ( I built two, one still runs just fine)
I am ADD and bored so I am going to try Building a more modern FI motor similar to Wally on STF who managed to get nearly 500 hp from his turbo charged 71/103 motor....

This is not my daily driver, nor will it ever become that....it's cheaper than a therapist and keeps my out of more trouble....so I play around with it.

I built the large djet because so many people said it could not be done yet I kept hearing of two or three sleeper motors out there, I tracked down two of them, learned about them, so I went for it...
There was no help, just an air/fuel meter and some common sense tuning...
I do agree with Jake, it's a compromise.
I cannot go without having heat up here, so with my next version I will be designing heater boxes, or most likely a single box, for the headers to make sure I stay warm..

Rich

[worn]

Well, a djet 71/103 with a stock camshaft and stock HE was dynoed at 155 hp.

It's certainly a compromise for sure, but it's fun enough and still has heat.

Now I am changing out the camshaft in mine ( I built two, one still runs just fine)
I am ADD and bored so I am going to try Building a more modern FI motor similar to Wally on STF who managed to get nearly 500 hp from his turbo charged 71/103 motor....

This is not my daily driver, nor will it ever become that....it's cheaper than a therapist and keeps my out of more trouble....so I play around with it.

I built the large djet because so many people said it could not be done yet I kept hearing of two or three sleeper motors out there, I tracked down two of them, learned about them, so I went for it...
There was no help, just an air/fuel meter and some common sense tuning...
I do agree with Jake, it's a compromise.
I cannot go without having heat up here, so with my next version I will be designing heater boxes, or most likely a single box, for the headers to make sure I stay warm..

Rich

I always figured when I got things settled I would graph out the mps induction vs vacuum and post it so one could start at the bench with a pretty close setting. At this point I have web cams version of the 9550 increased compression, 2056 low torque below 2,000 rpm and I have to run an A/F of about 12 to keep it from overheating the head. I definitely have more power, but after an hour or so I am limited by temps sometimes. Oil cooler helped. So, how much better can it be? I think people are asking for advice here. I know I am.

[Bleyseng]

Well, a djet 71/103 with a stock camshaft and stock HE was dynoed at 155 hp.

It's certainly a compromise for sure, but it's fun enough and still has heat.

Now I am changing out the camshaft in mine ( I built two, one still runs just fine)
I am ADD and bored so I am going to try Building a more modern FI motor similar to Wally on STF who managed to get nearly 500 hp from his turbo charged 71/103 motor....

This is not my daily driver, nor will it ever become that....it's cheaper than a therapist and keeps my out of more trouble....so I play around with it.

I built the large djet because so many people said it could not be done yet I kept hearing of two or three sleeper motors out there, I tracked down two of them, learned about them, so I went for it...
There was no help, just an air/fuel meter and some common sense tuning...
I do agree with Jake, it's a compromise.
I cannot go without having heat up here, so with my next version I will be designing heater boxes, or most likely a single box, for the headers to make sure I stay warm..

Rich

I always figured when I got things settled I would graph out the mps induction vs vacuum and post it so one could start at the bench with a pretty close setting. At this point I have web cams version of the 9550 increased compression, 2056 low torque below 2,000 rpm and I have to run an A/F of about 12 to keep it from overheating the head. I definitely have more power, but after an hour or so I am limited by temps sometimes. Oil cooler helped. So, how much better can it be? I think people are asking for advice here. I know I am.

Really? My 2056 hasn't seen over 350F Cht's often running 9 to 1 CR and AFR is in the 13.5 -14. to 1 range at cruise (partload )
Is your MPS adjusted ?

[r_towle]

If that question is to me, why yes, it gets hot but it's manageable and tuned slight on the rich side, get shitty mpg.
I learned how to tune back when we tried to get over 40 mpg.....there is a thread here somewhere.
I use just an air/ fuel meter. No fancy setup here.

I don't have a temp gauge, really don't want to know and I can smell it when it gets too hot.....again, no longer a daily car so it does not see long highway runs