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Mon Sep 15, 2014 1:59 pm

I picked up a 73 squareback FI engine rebuild request from a customer. I have read up on some other similiar posts that specify you cannot put a bigger cam and expect the stock injectors to keep up. So, is it possible to up the cr to say 8 or so from the stock 7.5/7.7cr? Possible to slap 37x32 super stockers in there? Or would we need to upgrade the injectors also? This engine is a first time acvw owner and he is even using this vehicle to learn stick. The oil is burnt, which leads me to believe at one time the belt may have broke and they limped home or something. The main seal is leaking, so Im pretty sure it has developed some thrust. Who knows until I break it open. I want to know what the possibilities are for upgrades as is. Thanks for any info. The customer regardless wants a rebuild even if end play is still good.

Mon Sep 15, 2014 4:52 pm

I'm thinking as far as improving intake flow is concerned, the stock throttle body and intake manifolds would be a restriction, and no significant gains could be made unless everything was enlarged. That said, if there is a small margin, maybe seat blending, a good valve job, back-cutting the intakes, and a flap job would be all that's necessary.

As far as the cam, it might be wise to stick with a close to stock profile. You could always use 1.25s on a stock cam, or use a "cheater cam". The compression could be played with, as long as it's kept modest and works for that profile and octane requirement.

Mon Sep 15, 2014 5:12 pm

I appreciate the suggestions but I need some tried and true answers on this one. Adding 1.25s to a stock cam changes the amount of fuel-air charge that will be demanded of the engine. Already Im sure that the stock injectors will be undersized. I dont want to mess with the stock FI.
I guess at this point it would be safest to remain in the stock head realm and maybe a 3 angle seat clean up w/ chamber smoothing might be the ticket.
Ill have to ask a friend in Cal about the compression factor with stock FI.

Mon Sep 15, 2014 6:07 pm

Why not just keep it stock? They do very well in stock trim.

Max

Mon Sep 15, 2014 6:22 pm

Max Welton wrote: Why not just keep it stock? They do very well in stock trim.

Max

It sure is one of the options of course.

Mon Sep 15, 2014 7:37 pm

jfats808 wrote: I picked up a 73 squareback FI engine rebuild request from a customer. I have read up on some other similiar posts that specify you cannot put a bigger cam and expect the stock injectors to keep up. So, is it possible to up the cr to say 8 or so from the stock 7.5/7.7cr? Possible to slap 37x32 super stockers in there? Or would we need to upgrade the injectors also? This engine is a first time acvw owner and he is even using this vehicle to learn stick. The oil is burnt, which leads me to believe at one time the belt may have broke and they limped home or something. The main seal is leaking, so Im pretty sure it has developed some thrust. Who knows until I break it open. I want to know what the possibilities are for upgrades as is. Thanks for any info. The customer regardless wants a rebuild even if end play is still good.

It has not much to do with the injectors. Those same injectors (same flow rate)....keep up with the 914 2.0 no problem.

The issues with the cam are that its intake valve timing is very specific. Because the injectors run in pairs ( 1&4 and 2&3)....you get two injectors that fire just about perfect for the start of intake valve open event....but 2 that are out of phase. The valve timing and injection timing are set is careful enough that at all but idle its not very noticable.

The cam also has a fairly specific range of lobe center. Typically between 105 and 110 max. This is to keep the vacuum pulse signature stable so that the MPS (manifold pressure sensor) plays well.

All of that being said....you can use modest increases in mostly duration and just a little lift.
Webcam makes a pretty good cam for the type 4 for D-jet that is a decent improvement. Its called grind #73. I dont know if they make a type 1/3 based version of it.

I dont know exactly what cams etc you can get for type 3 D-jet but here is a range of improvements I used to get a stock 82 hp type 4 1.7l with D-jet to just a hair over 100hp (102 with about 90 rwhp.). The same type of massaging will be required for the same level of improvement with a type 3.

Stock domed pistons with 8.6:1 cr (stock was 8.2:1)
Deck at .038"
42 x 35 valves (stock was 39 x 33)
Slightly stiffer springs
Web #73 cam
Porsche swivel feet
5mm larger tb
Valves unshrouded
Larger fuel pump for correct fuel pressure stability...key for this system
Better than stock exhaust. ....and I still could have done much better
Pertronix with 42kv coil...still could have been better
Port match in intakes
Resistor ballasts for cht and ambient air sensors...non stock mod
Rebuikt distributor with adjustable vacuum advance and tweaked mechanical curve
New fuel injection harness....key...connectivity is key.
Lots of driving and adjusting and tweakin
Adjustments to injection timing...non stock mod
Lightly, modified TVS switch.

The problem with the type 3 that will limit you most is the intake manifold system. About yhe max size it can comfortably feed......and thats barely and not optimum...is 1776. Your runners will handle that....you TB will not. I would machine that aluminum bottle manifold end off and bolt on the tb of your choice. The center manifold is slightly small but could be expanded by about 1/4 in volume pretty easily.

Injector wise....this system uses a low ompedance injector. About 2 ohms max. You should buy brand new injectors. The stock sized 26-28 pound injector will do you fine....but nice new ones can handle a bit more pressure than the originals which max out...really the safest max pressure with a no lie gauge is 32 psi. They start to have reseating issues at 35 psi above 3000 rpm.
You can get better more modern low impedance injectors and run just at 40. Thats a better range of tweakability and atomization.

Its tough injection work with. Its not complex.....23 wires and 4 sensors......its, complicated. But its fun to play with...reliable as a brick when you do it right....and the throttle response spanks anything but new after market injection. Ray

Mon Sep 15, 2014 7:39 pm

jfats808 wrote: I appreciate the suggestions but I need some tried and true answers on this one. Adding 1.25s to a stock cam changes the amount of fuel-air charge that will be demanded of the engine. Already Im sure that the stock injectors will be undersized. I dont want to mess with the stock FI.
I guess at this point it would be safest to remain in the stock head realm and maybe a 3 angle seat clean up w/ chamber smoothing might be the ticket.
Ill have to ask a friend in Cal about the compression factor with stock FI.

Undersized for what? Are you increasing the CCs?

Mon Sep 15, 2014 8:51 pm

http://www.drcamshafts.com/

As of three years ago, this guy was the only person that I could find that would commit to a non - stock cam profile for type 3 engines. No one had any information or guidance. Web didn't cut their type cams on type 1 blanks.
John at DR Camshafts has experience with 914 d-jet cams (same injection), and his mild grind is milder than the Web.
Call John, talk to him. He'll recommend a grind a compression ratio. Then build a reasonable decked, stock displacement, balanced engine with stock sized valves and clean heads.

Mon Sep 15, 2014 9:26 pm

bugguy1967 wrote: jfats808 wrote: I appreciate the suggestions but I need some tried and true answers on this one. Adding 1.25s to a stock cam changes the amount of fuel-air charge that will be demanded of the engine. Already Im sure that the stock injectors will be undersized. I dont want to mess with the stock FI.
I guess at this point it would be safest to remain in the stock head realm and maybe a 3 angle seat clean up w/ chamber smoothing might be the ticket.
Ill have to ask a friend in Cal about the compression factor with stock FI.

Undersized for what? Are you increasing the CCs?
Think about cam dynamics. If you add a 1.25 rocker assembly to a 1.1 set up cam. You increase the need for more fuel due to added lift and added duration. Maybe it will affect it, maybe it wont. Its close enough to have me doubting. I am not increasing CC size. I wanted to know first off, how much more cam I can add if at all and how much more CR I can increase before the stock injectors become lacking. Im not sure what size the valves are in this one till I tear it down, nor do I know what condition. I know one fact is that at one time or another the oil was cooked.
The owner first time driving a stick and vw for the matter. So I think probably a bone stock rebuild is the best course as Max recommended.
Appreciate the suggestions from you 4.

Mon Sep 15, 2014 9:49 pm

The ratio rockers will do something but not very much. I'd shy away from the 37mm intake, works great with carbs but remember on the FI models they went smaller, probably for a reason.

This is a perfect application for the CB cheater cam.
Keep the deck tight and up the CR a little.

Just doing those things it will have better vacuum signal than stock so the injection may even work BETTER than before. Not a ton but a little :wink:

Mon Sep 15, 2014 9:50 pm

Well more compression will not demand more fuel, and I've read a few posts here and have seen one T3 with more CCs and stock F.I. The system does have some adjustability. It has been said several times that the system can handle up to 1800 CCs. For me, it would not be a big gamble to add ratio rockers, increase compression slightly, and re-work my heads.

Try and search for T3 F.I.'d larger CC engines. I did a quick search, but didn't type in the right key words. There is some good info there.

Also, in case you didn't know, the CB Cheater Cams were originally developed for factory F.I. engines.

Mon Sep 15, 2014 10:07 pm

jfats808 wrote: bugguy1967 wrote: jfats808 wrote: I appreciate the suggestions but I need some tried and true answers on this one. Adding 1.25s to a stock cam changes the amount of fuel-air charge that will be demanded of the engine. Already Im sure that the stock injectors will be undersized. I dont want to mess with the stock FI.
I guess at this point it would be safest to remain in the stock head realm and maybe a 3 angle seat clean up w/ chamber smoothing might be the ticket.
Ill have to ask a friend in Cal about the compression factor with stock FI.

Undersized for what? Are you increasing the CCs?
Think about cam dynamics. If you add a 1.25 rocker assembly to a 1.1 set up cam. You increase the need for more fuel due to added lift and added duration. Maybe it will affect it, maybe it wont. Its close enough to have me doubting. I am not increasing CC size. I wanted to know first off, how much more cam I can add if at all and how much more CR I can increase before the stock injectors become lacking. Im not sure what size the valves are in this one till I tear it down, nor do I know what condition. I know one fact is that at one time or another the oil was cooked.
The owner first time driving a stick and vw for the matter. So I think probably a bone stock rebuild is the best course as Max recommended.
Appreciate the suggestions from you 4.

From your speculations and from the suggestions here....and this is no insult.....you have no idea how the D-jet system works.

Injector size has not one thing to do with the limitations of this system. I have been working on virtually nothing but D-jet (as my toys...and lots of other stock injection along the way)...since about 1978.

All the talk about "cam dynamics" and ratio rockers will help you little. This system is set up to be injection timing critical.....and if you play with the cam enough to disturb the vacuum signature outside of the harmonic it was designed for.....you will be lucky if it starts at all....no shit!

Ratio rockers will help a bit....because excessive cam lift does not. A split pattern cam with extra exhaust duration helps....but again you cannot go too far....or your vacuum signature is gone. And no....its not just about a specific level of vacuum. Its about a smooth signature without spikes.

There is no great mystery to D-jet cams. Only so many degrees to play with that will result in a lobe center and lift/duration range that supports the range of the MPS.

Right now the best D-jet cams out there (for type 4) are the web #73 (mild but uses factory early Z series valve timing) and the Raby 9550 and 9590....both are split pattern cams.

The issue with tuning D-jet and staying stockish is based around the manifolds and adjustability.
The MPS is highly adjustable.....but the temp sensors that set your mixture baseline (MPS is load) have to be modified.

Unlike tuning for carbs or aftermarket injection....which are where most of the ideas and suggestions here are based. .....its not about just cramming as much air in with a fat cam as you can and switching to a larger injector.......because the system cannot meter that to tell it how much fuel it needs. Also...this is a centralized plenum system...and a pretty good one. On a centralized plenum system...if you try to force it to flow more than its designed for (short of a turbo.....different animal)....it actually loses velocity through turbulence .....and flows less.

The baseline D-jet system with the same basic sized injectors....only 8 of them....was used to feed Mercedes v-8s......so its NOT an injector issue.

A lot can be done within a certain range....even with stock cam. The factory tuning was fairly mediocre. .....but you have to obey the vacuum signature parameters. This whole system runs on two thkngs: vacuum and resistance. No programming at all. Ray

Mon Sep 15, 2014 10:16 pm

bugguy1967 wrote: Well more compression will not demand more fuel, and I've read a few posts here and have seen one T3 with more CCs and stock F.I. The system does have some adjustability. It has been said several times that the system can handle up to 1800 CCs. For me, it would not be a big gamble to add ratio rockers, increase compression slightly, and re-work my heads.

Try and search for T3 F.I.'d larger CC engines. I did a quick search, but didn't type in the right key words. There is some good info there.

Also, in case you didn't know, the CB Cheater Cams were originally developed for factory F.I. engines.

Yes....but thats a meaningless statement (that yhe cheater cam was made for fuel injection) unless the fuel injection it was designed for was D-jet.....which it may be.....but there were no actual type 1 engines ever built with D-jet....only L-jet.
Even though a type 3 engine is "technically" a type 1....you need to get specific.
In type 1....they are close enough....and that is part of the issue. D-jet vacuum signature is similar to L-jet.....but more sensitive to spikes. So if you are planning to do better than stock tuning uou are going to need something optimized better.
Again....its not JUST about lift and duration. Its about valve timing. This is not a bank fire system.

As for size......the type 3 D-jet "fueling" system.....can handle up to about 2.2 liters with nothing but an injector change....and a few tweeks to the MPS.
However....the "induction" system (the runners, plenum and TB) cannot handle over just at 1700cc.
Yes....you can run a 1776...but the performance will be lower than a carbed 1776. It will drive nice.....but whats the point of injection if there is less benefitit. Yes there are a few that have stretched to 1800.....but not with stock intakes.

If you work within the vacuum signature and airflow feeding requirements....virtually any sized engine can be fed with a basic D-jet system.....but you better be ready to fabricate an intake system. Ray

Mon Sep 15, 2014 11:20 pm

Ok timing specific fi system. Changing cams sounds like a wash because of specifity of timing events and ultimately cost. What I was waiting on was whether or not upping cr would effect the FI system and it got answered.
Your right Ray, I dont know how the D, L and whatever other fi systems work. Thats why I came here to ask. Thanks for the history lessons back to 86 and wisdom.

Mon Sep 15, 2014 11:27 pm

Hello
ALL what Ray said, and then some :wink:

Step one to increase performance on a type 3 D-jet is to enlarge the throttle inlet.
Step 2 is optimizing the engine inside. The typical detailing of a set of stock heads, perfect deck height and a raise in CR to 8,2-1 and a freer flowing exhaust, can be considered as a stage 1, which will give you a power increase of about 6 hp and + 10 Nm torque.
The moment you staret changing the cam and alter the manifold pressure you must change the fuel pressure regulator to a newer, more modern (read: one with a larger pressure span) and possibly replace the diaphragm in the barometer can, (or air pressure sensor) also so that it gets a wider and faster working range.
A split duration cam would be nice, but in lack of such a shelf item you should look towards the cheater cam, but have it ground on 110 LC, then install it on 107 ILC. This to get the manifold signal as close to what a stock cam will do as possible.
A set of Tims super stock will work fine, but you would need to clean up the ports a little still. 8,5 CR on medium grade fuel.
Exhaust. For instance an over the top system. 1 3/8" is plenty. 1½" will work too, as long as the muffler is not a straight through.

Now the trick is to set the fuel pressure so that it pulls the pressure enough "backwards" at idle and low speed, but also supply enough at WOT.

This way it is possible to increase the power to about 65 hp and 130ish Nm torque with a nice and flat curve.
It can even work with automatics.

It does take some time tweaking the sensors to make the system do what you want it to, but its possible and not that much worse than working with a set of carbs that are really out of tune 8)

Hope this helps.

T

Tue Sep 16, 2014 12:28 am

This probably wont help, but I used the stock injectors from my squareback with a LH-Jetronic box. Pulled way over 250 hp from a two litre Opel.
Not much from the D-Jetronic can be reused if you switch systems though...

Tue Sep 16, 2014 6:35 am

Alstrup wrote: Hello
ALL what Ray said, and then some :wink:

Step one to increase performance on a type 3 D-jet is to enlarge the throttle inlet.
Step 2 is optimizing the engine inside. The typical detailing of a set of stock heads, perfect deck height and a raise in CR to 8,2-1 and a freer flowing exhaust, can be considered as a stage 1, which will give you a power increase of about 6 hp and + 10 Nm torque.
The moment you staret changing the cam and alter the manifold pressure you must change the fuel pressure regulator to a newer, more modern (read: one with a larger pressure span) and possibly replace the diaphragm in the barometer can, (or air pressure sensor) also so that it gets a wider and faster working range.
A split duration cam would be nice, but in lack of such a shelf item you should look towards the cheater cam, but have it ground on 110 LC, then install it on 107 ILC. This to get the manifold signal as close to what a stock cam will do as possible.
A set of Tims super stock will work fine, but you would need to clean up the ports a little still. 8,5 CR on medium grade fuel.
Exhaust. For instance an over the top system. 1 3/8" is plenty. 1½" will work too, as long as the muffler is not a straight through.

Now the trick is to set the fuel pressure so that it pulls the pressure enough "backwards" at idle and low speed, but also supply enough at WOT.

This way it is possible to increase the power to about 65 hp and 130ish Nm torque with a nice and flat curve.
It can even work with automatics.

It does take some time tweaking the sensors to make the system do what you want it to, but its possible and not that much worse than working with a set of carbs that are really out of tune 8)

Hope this helps.

T

Everything is fairly spot on....except for changjng the barometric chambers. That is simply a reference chamber for what counterbalances atmospheric pressure. The MPS does not rsally have an enrichment limit range per-se. Its just a reaction rate chamber. That rate of reaction can be adjusted. Whether its a v-8 or a 4cyl.....the vacuum signature will be similar. V
Baseline fuel volume is adjusted and added to at the MPS.....but is not totally set at the MPS.
Baseline fuel pressure has quite a bit of the function.

Tuning D-jet works more like this: in general if the MPS appears to run out of range of adjustment, the first move is to adjust fuel pressure (within what is allowed by the injector pressure range). When you run out of range with that,....f you are serious about this.....tweaks to the main armature spring can be made. Then there are some overall enclosure volume or venting tweeks that can be made.

Yes.....a better fuel pressure gauge is nice....but mainly for accuracy. Unless you get injectors that can handle higher pressure. ....you cant use higher pressure.

But you are correct that a better regulator would help.....along with a better pump. This is a fixed pressure system. Because of that.....all adjustments to enrichment are made by the ECU with the "assumption" that fuel pressure is dead on and stable.
As you start making more demands of the system. ...it gets harder for the stock pump to keep the pressure stable.
Because the MPS is generally capable of feeding the system more fuel than it needs....the firs5 main symptom of a poor cam profile creating a poor vacuum signature......is wild +/- 5 psi swings of the needle at rpm speed....based around the reaction of the MPS.

I also add a surge bleed tank to the system. The more you tune the system for higher output...the more critical stable fuel pressure becomes. If you are tuning for optimum a Bosch 044, surge tank and a return bleed from the surge tank fix that nicely. Ray

Tue Sep 16, 2014 7:04 am

jfats808 wrote: Ok timing specific fi system. Changing cams sounds like a wash because of specifity of timing events and ultimately cost. What I was waiting on was whether or not upping cr would effect the FI system and it got answered.
Your right Ray, I dont know how the D, L and whatever other fi systems work. Thats why I came here to ask. Thanks for the history lessons back to 86 and wisdom.

Hey...wasnt beating on you. Just pointing out that a great many awesome mechanics have bent their brains around this system and failed. You cant force D-jet to conform to a different set of physics. But if you know what its physics are.....you can work within them and trick the system into doing quite a bit more than stock.

The easiest way to get the better than stock cam profile under control is to look at the stock cam....stay with its valve timing (unless as mentioned. ..someone has an aftermarket type 1 based cam set up for a better than stock D-jet)......and add duration to the grind without iolating a lobe center between 105 and 108.
Lift.....a little can help. As others have mentioned.....small ratio rockers may help that. The issue is that if lift becomes to high....velocity and atomization drop too quick....and that screws up vacuum signature.

I would find out what the owners goals are with the engine. If they want to keep it....origjnal-ish......and can handle say. ...15% better hp and much better throttle response than stock....and much better performance than carbs with the same size engine....then its a viable option keeping D-jet.

Then.....as I noted.....it depends on how much tweaking and time you want to spend with it. If this were your engjne and one of your regular drivers....and you wanted to experiment......I am working on a whole range of tweeks. Like:
1. I have a sequential injection trigger point system using the original two channels. I have tested it on the bench and it works nicely....but have not fueled the far with it yet. That wojt happen until about January when I finish my new engine and can get it into the car and it is broken in. It will most probably either require almost double the fuel pressure.....not the most reliable method with low impedance injectors.....or an injector with about 30% higher baseline volume and a modest 25% fuel pressure increase.

2. I am getting set to print a new circuit board for the TVS. It will have an increased sweep arc (diameter not total sweep of arc). This will allow putting more enrichment contacts between the park/idle point and WOT....also allowing strategic spacing of them. It will mean modifying the wiper arm as well. In effect....the TVS is the accelerator pump. This adds more range to it and more control.

3. .....and this is mainly for the type 4 plenum....but I am working on a plateless TB that will get rid of the nastly turbulence plume within the plenum.....make it flow, better and promote better vacuum signature and MPS tuning.

4. Another tool that I will be employkng is a frequency valve injector....just lioe CIS injection used.
The objext is that fuel pressure higher than what is necessary is supplied to the loop. The rrequency valve keeps it bled back to normal. When rpm hits about 4700.....the frequency valve snaps shut in two stages increasing fuel output at WOT in exact steps.

This is good because D-jet runs out of enrichment ability at about 5500 rpm due to epectronic limitatokns. Other tuning factors can cause the effects to start being noticable as low as 45-4700 rpm.

I am also going to at worst a hall type 55kv ignution, system...and at best I am contemplating, frank fired ignition and capping the original distributor and using it for nothing b7t iniection, triggering.

Just some thoughts. Ray

Tue Sep 16, 2014 10:09 am

[quote="raygreenwood"] jfats808 wrote: Ok timing specific fi system. Changing cams sounds like a wash because of specifity of timing events and ultimately cost. What I was waiting on was whether or not upping cr would effect the FI system and it got answered.
Your right Ray, I dont know how the D, L and whatever other fi systems work. Thats why I came here to ask. Thanks for the history lessons back to 86 and wisdom.

Hey...wasn't beating on you. Just pointing out that a great many awesome mechanics have bent their brains around this system and failed. You cant force D-jet to conform to a different set of physics. But if you know what its physics are.....you can work within them and trick the system into doing quite a bit more than stock.

The easiest way to get the better than stock cam profile under control is to look at the stock cam....stay with its valve timing (unless as mentioned. ..someone has an aftermarket type 1 based cam set up for a better than stock D-jet)......and add duration to the grind without violating a lobe center between 105 and 108.

Lift.....a little can help. As others have mentioned.....small ratio rockers may help that. The issue is that if lift becomes to high....velocity and atomization drop too quick....and that screws up vacuum signature.

I would find out what the owners goals (are you the new owner?) are with the engine. If they want to keep it....original-ish......and can handle say. ...15% better hp and much better throttle response than stock....and much better performance than carbs with the same size engine....then its a viable option keeping D-jet.

Then.....as I noted.....it depends on how much tweaking and time you want to spend with it. If this were your engine and one of your regular drivers....and you wanted to experiment......I am working on a whole range of tweaks. Like:

1. I have a sequential injection trigger point system using the original two channels. I have tested it on the bench with a powered system and it works nicely....but have not fueled the car with it yet.

That wont happen until about January when I finish my new engine and can get it into the car and it is broken in with the original set of injection parts. It will most probably either require almost double the fuel pressure.....not the most reliable method with low impedance injectors.....or an injector with about 30% higher baseline volume and a modest 25% fuel pressure increase.

2. I am getting set to print a new circuit board for the TVS. It will have an increased sweep arc (diameter of are not total sweep of arc in degrees). This will allow putting more enrichment contacts between the park/idle shut off point and WOT....also allowing better strategic spacing of them. It will mean modifying the wiper arm as well.
In effect....the TVS is the momentary accelerator pump of the system. This adds more range to it and more control.

3. .....and this is mainly for the type 4 plenum....but I am working on a plate-less TB that will get rid of the nastly turbulence plume within the plenum.....make it flow better and promote better vacuum signature and MPS tuning. That alone would be a big improvement. Kind of like what the slide valve TB did for high pressure Kugelfisher injection...but without vibration sensitivity. It will use a bullet shaped plug with a shaped tail instead of a throttle plate.

Throttle plate turbulence is a big issue with any plenum system. Programmable injection can get around a small portion of the effects....and adding an air straightener screen can help.....but with such a small plenum volume there is little room to work and a very short path before the 90 degree turn into the runners. This will help that a lot making flow and runner velocity much better

4. Another tool that I will be employing is a frequency valve injector....just like CIS injection used. I have used this before on D-jet with some success but have never fully tuned it out.

The object is that fuel pressure higher than what is necessary is supplied to the loop at all times. The frequency valve keeps it bled back to normal pressure.
When rpm hits about 4700.....the frequency valve snaps shut in two stages increasing fuel output at WOT in exact steps....about 5 psi per step.

This is good because D-jet runs out of enrichment ability at about 5500 rpm due to electronic limitations. Other tuning factors can cause the effects to start being noticeable as low as 45-4700 rpm.

I am also going to at worst a hall type 55kv ignition, system...and at best I am contemplating, crank fired ignition and capping the original distributor and using it for nothing but injection, triggering.

EDIT: as you can see....there is not much that you can actually insert into the electronics of the D-jet system. Its a closed loop...and short of reengineering the circuit board and changing components...there is no interface. There is no software. It is hardboard that is internally....built something like a "lotus" chart with input/output parameters based around resistance circuits and timing circuits. Its all hard wired.

But.....you can ADD small sub-systems to effect D-jet's subsystems.
The original designers speak of the system as three separate systems

a. The fuel supply system (pump, lines, injector, regulator, damping systems etc.)
b. The air system (plenum, runners, TB, vacuum control items like decel valve and AAR)
C. electronic control system (ECU, intake air temp sensor, Throttle valve switch, Manifold pressure sensor, cylinder head temp sensor, wiring harness, distributor triggers)

as you can see....you can separately tweak each of these sub-systems or add parts to them that manage the input to the fixed computer either in terms of resistance readings, turning things off or on or or changing when they turn off or on....or in the case of fuel pressure, stabilize it, vary it....or in the case of airflow...increase it, smooth it etc.

Just some thoughts. Ray