biggest 2.x with Stock FI

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r_towle
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biggest 2.x with Stock FI

Post by r_towle » Thu Nov 06, 2003 6:58 pm

What is the largest 2.x motor with a "stock" FI that someone has seen (prefer to talk to someone who has on working right now)
But, if anyone know how big you can go, please let me know...

I am assuming 2.2 with the stock injectors, a slightly different Cam and a slightly bored out throttle body.

I am also assuming the same if I go to 2.4 but replace the injectors with 4.8 liter mercedes injectors.

Thoughts????

Rich

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raygreenwood
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Post by raygreenwood » Thu Nov 06, 2003 9:11 pm

2.2 is about the limit for D-jet without some serious work. L-jet has few limits. L-jet has been put on just about anything. But...the limitatios will be in the calibration of the MAF. It will help to get one from an engine that is close to the same displacement and stroke...to limit the # of adjustments needed. Also...look at digifant injectin. Lots of cheap equipment and great possibilities. Ray

r_towle
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Post by r_towle » Thu Nov 06, 2003 9:37 pm

2.2 with djet?
What would you recemmond for an engine configuration?
Bore, Stroke, Cam???

Then what to do with the Djet???
How will I know if it is right, should I get an oxygen sensor to get the F/A mixture correct?

Rich

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raygreenwood
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Post by raygreenwood » Fri Nov 07, 2003 12:12 am

Remember that D-jet was used on the 2.0 with no problem. Stroke is not so much the huge issue. The combination of stroke and cam...and its affect on the smoothness of the vacume signature are mainly whats important. The level or variation and enrichment are still about the same on a 2.2...just that the overall fuel usage is higher. Read that as slightly larger injectors..and slightly higher fuel pressure. Of course, using stock parts...the available runners and plenum will become too small. The 2.0 runners, a 2.0 plenum....an extender tube to add some volume to the plenum..and a slightly larger TB can help keep the resulting higher velocities near normal for the system...but there will be some tuning issues. Ray

r_towle
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Post by r_towle » Fri Nov 07, 2003 8:59 am

Ray,
Always a well informed response from you, I appreciate that.

What are the next step injectors that you know of?

I have not looked to hard, but I found the 4.8 liter mercedes injectors are the same size, shape and require the same voltage....

How about Volvo injectors or others???

Looking in the 2.2 range to play with.
I would like to keep the plenum and runners stock, willing to bore out the throttle body...I think 2.2 is not to much of a stretch...

Rich

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raygreenwood
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Post by raygreenwood » Fri Nov 07, 2003 1:44 pm

The mercedes an volvo injectors may do fine. With added fuel pressure, the 2.0 injectors should do fine. The key to find out on the mercedes and volvo injectors is how large a displacement each injector was feeding. Ray

r_towle
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Post by r_towle » Fri Nov 07, 2003 2:16 pm

Right,
Another mechanic made a good point, its not just the displacement, but the HP/CC that the injector is feeding needs to be comprable.

We see a 4.8/8 mercedes engine that is pushing a 140 HP motor (not sure just for this discussion)

Yet we might find a honda motor 1.8/4 that is 180 HP ....

So I need to do some homework, I will and I will get back to you.

Rich

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raygreenwood
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Post by raygreenwood » Fri Nov 07, 2003 3:40 pm

What that mechanic noted is true...somewhat. Its one of the problems I see many people working with in this column. Its not exactly true for instance....that if you have a 2.0 liter engine with 100 HP...and you are workng to make it a 2.0 with 150 HP....that you will need more fuel...or a different injector.

What you are doing to an engine like I just described, is modifying its efficiency through better compression, cam timing, balance, airflow, exhaust. Many times this engine gets even better gas milage...which means it does not use more fuel. Its simply a difference in how and when enrichment is used.

If for instance, a system uses injection duration in milliseconds...which most modern injection do.....for enrichment, you would soon run out of injection duration or cycle rate. Then you would have to go to a larger injector. The problem with that...is a larger injector can only flow so low...at the lowest cycle rate. Many people start sizing injectors up simply by finding one with larger Lbs of fuel per hour. That is not even the most important factor. If the injector is too large, the idle will be terrible and low specific output at low rpms will be a common problem.

Now....if cycle rate of the injector is not your only method of enrichment...then this is easier. D-jet is actually quite good in that respect. You can bump up the fuel pressure as a multiple...instead of moving to a larger injector. You can only adjust so far this way...before the same effect as having too large of an injector happens. Thats because, even at lowest idle point...the extra fuel pressure is still there.

One of the best ways around this, is to use an aftermarket rising rate fuel pressure regulator. Use this in conjunction with a simple vacume switch...like you find on water cooled cars, to only activate the rising rate that you set...when a certain throttle point is achieved. You do not want a constantly self variable rising rate regulator with D-jet. This is because the EC has no sensors to know when it is operating.

So for instance. Stock D-jet fuel pressure is about 28 psi. Set the adjustable rising ate reg. for say...32 psi..to give you the higher volume you need. At say...2500 rpm...or the vacume rate that produces...teh vacume switch opens te vacume port to the rising rate regulator driving the pressure up to say 34 psi. A really sophistacated system could use a bank of regulators on the return rail to give ramped up pressures of say 32, 34 and 37 @ different times.....just for an example.

I would not get too wrapped up in the injector selection. Unless you are racing...like full out...you will find its not that important (yet). There are bigger issues. The D-jet injectors are some of the largest anywhere. The issue will mainly be wether it can cycle fast enough....to deliver the injection duration needed. I would get it running first and adjust as far as you can with fuel pressure. Ray

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Dave_Darling
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Post by Dave_Darling » Fri Nov 07, 2003 7:49 pm

I have seen a 2.2L 914 engine that ran with a modified stock 2.0 D-jet system. I did not do any of the work, though, so I don't know the details. However, the intake system looked completely stock. So I assume that the modifications were simply tweaks of the existing components.

I would bet that the cam used in that car was stock. Not sure about the bore and stroke measurements.

--DD

Gary Balke

Post by Gary Balke » Sun Nov 09, 2003 7:30 pm

My '74 is a bored and stroked 2.2 liter that is running a bone stock
D-jet system. This was done by the previous owner. I've owned the car for since Dec. 1997 and hvae had no problems.

The PO also had hydraulic lifters and cam installed during the engines rebuild. Based on his records, I believe the motor was originally a 1.8 liter that he had rebuilt by California based shop.

Gary
O'Fallon, MO

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raygreenwood
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Post by raygreenwood » Mon Nov 10, 2003 12:04 am

Thats very nice to know. I have always thought D-jet metering was one of the most flexible. Its just that the adjustments are a little delicate...and more than some people have patience for. The system itself is not difficult. I think it could handle more than 2.2....I just don't know...short of masive fabrication....where people would get the proper manifolds and plenums. Ray

r_towle
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Post by r_towle » Tue Nov 11, 2003 1:43 pm

ok heres the plan,

78.5 mm crank
96mm P/C
2270 config.

stock injectors
stock mps (adjusted)
stock plenum
stock intake tubes
bored out throttle body

My questions are as follows
Cam
Head mods (bigger valves?, port and polish?)

Throttle body, how big would be better, yet sane. I have heard that the VW bus Throttle body was larger and might serve my purposes.

And finally, how do you adjust the outer screw on the MPS without the inner screw turning???
Do you somehow mark the outer screw position, take out the inner screw, insert the star bit and adjust the outer screw, then re-insert the inner screw?? That seems to be the only way I can see doing it aside from fabricating a special tool for this purpose (may be a good idea)

And if I was to integrate some sort of oxygen sensor into the exhaust system and log my A/F mixtures, would that be the best way to get it back to the correct settings...I am basically thinking to adjust the system so it matches some of the stock tables on Anders site when I'm all done...

Rich

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raygreenwood
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Post by raygreenwood » Tue Nov 11, 2003 2:50 pm

Do not take out the inner screw. Its worth it to actually dissassemble the MPS....and look at the depth ...through the keyhole slot in the plate surrounding the center screw, to get an idea as to the factory measurement setting of the surrounding screw. Use a caliper with thin depth foot...softly..or use round wire feeler guages with the hook on the end. This way, you have a start position for that surround screw, in case you get out of whack.

I have found it best...on an un-molested MPS, to assume that the surround screw is good. This is mainly because the inner depth setting pretty much corresponds to the max amount the armature can be driven in and not upset the field response or damage the copper plate.

This is a hair bit tedious...but makes a wonderful tool. Cut very square..about 1.5" of a 7mm hex key. Mount it perfectly vertical in a drill vise...and using a carbide bit...slowly drill a hole about 4-5mm through the center. Spot weld that into the ring end of an old 7mm wrench. Now you have a wrench that fits and has small screwdriver accessthrough the center. You can alsogo to a hobby shop and but hex plastic stock...easier to drill. Or plastic square or round stock and sand the flats to taste....before drilling the hole.

The manifold volume may be getting in the tad too small range. A t that point, a slightly larger TB may be necessary to make sure the velocity dos not spike to quick....as well as the vacume signature. Boring out TB's is a rough way to go. For sure..use the 914 plenum and TB if you can get it. Thats the top mounted TB. Then you can use a short extender tube under the TB to give an adjustable amount of extra volume to the whle manifold. Something it would be worth trying if you havethe gumption....look for a very small CIS twin throat TB from like a 1500 cc rabbit engine. I would bet total throttle area would be nice. Also...you can always restrict on throat some. Ray

r_towle
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Post by r_towle » Tue Nov 11, 2003 5:13 pm

Ray,
I happen to live about ten minutes from the Eurometrics guy who bores out throttle bodies for the /6 porsches.

I know he could do this with extreme precision.

What size would you estimate would be a good size to go to for the bore on the throttle body?

Also back to the Cam.....what would you guess here??? I am assuming that I cannot really change that to much based upon all I have read..

Rich

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raygreenwood
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Post by raygreenwood » Tue Nov 11, 2003 8:33 pm

Yes, you can change the cam....a certain amount. See the problem is, the Djet in reasonable time....is already assymetrical in its injection timing. Its close enough, that its not a big deal. But if the timing gets too far out of whack...it affects the idle. But should run well above 1500 rpm.

The problem with people changing cams on D-jet...is that they generally don't just jump up a little...they jump up a lot. The valve overlap and duration are the most important at this point. Screw the injection timing. That does not really mess up the vacume signature to the MPS..unless you are idleing. Too little or way too much overlap will hurt ya. Lobe center I am guessing...between 105 and 108. I think the web #73 is a 106 lobe center...don't quote me. Its a good cam for D-jet. Little more lift and duration than stock...and timing of the original 411 with injection, within a couple degrees. You could probably get awaywith something a hair hotter...as long as the lobe center stays close. I don't know if they have anything that does not have too much lift.

Even if timing were no issue at all....you would want something with overlap and lobe center about like a web #73.

Now....depending upon when you want this thing running.......I have a set of new cams and triggers with a plug in harness (4 extra wires)....that uses the original two channels to make all 4 injectors individual and sequential. I will not be running on it until at least february...but I have already tested it. It works well....but will require a fuel presure adjustment. It uses two torlon cams in place of the original. It has four timing points and a larger diameter to leave the same open distance between trigger opening points. The cam sandwiched underneath....operates 4 interupters. So at four differnt preset points...it operates right channel, left channel, right channel, left channel. Again two injectrs paired to each channel just like stock...but the interupters underneath only allow one injector to operate in each channel at a time. It all fits in a stock D-jet dizzy. The interuptors are made of 1/8" square copper bar stock. They are about 1/4 the size of the stock D-jet triggers. They have a spring leaf on each one, a torlon bearing tube in the pivot drilling, are gold plated on the ends, and are stacked on top of each other with a garrolite wafer in between for insulation. The harness uses the original 3 pin plug on the dizzy, and a 4 pin pigtail coming from a grommet. Those four wires are the ground breakers. They go to the four injector grounds that attach to the crankcase split. The grounds have been un-paired and matched up to the four interupter wires wih afactory plug.
The switches run on the cams with torlon rollers. No lube needed. All contacts are factory crimps with gold plate.

I can hardly wait. The fact that the idle will be slightly smoother is less importaant than the fact that I can now adjust the ijection timing to either lead the opening of the intake valve, inject just as it opens...or during. Atomization should be superb. I expect throttle response above all else. Stay tuned. Ray

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