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Motronic FI on a 2.4 in a GT

64K views 832 replies 34 participants last post by  The Scifi Guy 
#1 · (Edited)
This is a new thread that I'm starting on this subject because I'll be using a different, stock, engine this time. This saga began with this thread:

https://www.opelgt.com/forums/general-discussions/108159-im-so-pissed-off.html

I then decided to go FI on the modified, checkered past, 2.5 engine I had in this thread:

https://www.opelgt.com/forums/factory-fuel-injection/108883-gordo-goes-fi-gtx.html

I decided to start over fresh with a new rebuilt stock 2.4 engine with slightly bigger valves, the subject of this thread. These are 2 "side threads" related to this mod:

https://www.opelgt.com/forums/general-discussions/109127-fancy-fittings.html

https://www.opelgt.com/forums/factory-fuel-injection/109153-lazy-slow-old-mans-surge-tank.html



So, here we go. We(me and Charlie) will be using the Jetronic manifold from a 2.2L engine, because a 2.4 manifold won't fit under a GT hood without modification. I don't know much about the FI system specifics at this point, but the system will use the Motronic computer with oxy sensor. The Motronic computer is from a 2.4 Omega and my engine will be essentially a stock 2.4 with the Omega cam. I'll be retaining my stock 2.4 manifold, 2.25" exhaust piping, Magnaflow exhaust, no resonator with a split Y pipe and excellent sound tuning exhaust tips. I'll be changing out my excellent 3-row copper radiator for a new OGTS 3-row aluminum one, solely because it's shinier. This car was made for the purpose of enjoying building it and to show and compete in car shows, so appearance is more important than it's performance.


One of the first challenges I wanted to conquer was to be able to retain the use of my 7-blade engine fan, my GM SI-style alternator, and the use of the stock upper and lower alternator brackets. Not an easy thing to do. The fan belt, pulleys, timing wheel, and brackets interfered with each other. The solution was to use a 1/2" spacer to make the water pump fan and pulley extend farther forward by one pulley width, reshim the alternator to be 1/2" farther forward, trimming the lower alt bracket, and reconfiguring it's shock absorbing cushions. I had previously performed a mod to retain the use of the upper alternator bracket by creating an offset bracket for the oem bracket, so that the alt fan doesn't hit the bracket. This process was documented in the "Gordo Goes FI in the GTX" thread above. No final pics to show yet, but here's some pics showing the reconfigured set up that should work on the finished engine project:

Auto part Engine Fuel line Vehicle Car
Auto part Fuel line Engine Vehicle Car
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#2 ·
The next project I had to tackle was adding a fuel return line, a stronger fuel pump, and possibly a swirl pot or surge tank concept. This was partially covered in my "Fancy AN Fittings" thread linked to in my previous post.

I'll be trying to chrome just about every part of the engine compartment FI system that I logically can, so I decided to likely go with stainless steel AN fittings to connect things in the engine compartment, use Gates rubber fuel line hoses with my own decorative sleeves, "normal" AN fittings at the tank and stuff under the car, and copper/nickel metal fuel lines. That's the tentative plan for now.

I have a custom aluminum copy of a GT fuel tank with 3/8" NPT capability at the two upper vent outlets and at the bottom fuel outlet. The tank's rear driver's side and filler neck vents are linked together and vent to atmosphere with a restrictor in the line to reduce fuel smell. I plan on using the tank's front passenger side vent opening as my fuel return line entrance.

I'm currently looking into the possibility of simply using a large oversize fuel filter as a psuedo mini surge tank. We'll see how that plays out.


This morning I asked Charlie to take some pics of the FI system and tell me where the fuel lines hook up. He posted a lot of responses and pics of various things related to the fuel lines and rail. One pic shows a fuel rail modded with AN fittings. I'll just post our whole text discourse and then all the excellent pictures. You can match up the comments with the pics yourself:

Gordo:
<<< Charlie, where does the fuel enter and exit the FI system in this pic? Do both lines enter/exit from the back or can/do they enter/exit from the front? Would that pressure regulator you offered normally be mounted on the engine or out back near the pump or can I mount it on the brake booster support where I have my present one? I'm trying to plan out my fuel line routing. Here, draw some arrows on the attached pic showing where the fuel lines normally attach. >>>

Charlie's responses and various pics he posted:
<<< If you use the stock regulator the one I have for you is unnecessary
Return is in middle of rail in is back of rail
If you make a rail, you and do what you want for in and out.
If you get a blank off made. You can rid yourself of the 25 year old regulator.


Here is a rail that they used AN fittings on instead of the banjo fittings

The weakness in the rail are the little feet. The 10mm bolts too. They are fine in use, however, they usually break when tightening the banjo fittings.

Just like factory, the inline regulator will be in and out at top and 1 out (return) at bottom. The in or out at the top doesn't matter its a chamber.

The one mod I do is to remove the two tabs.. UNLESS you really want to keep them for mounting or something. I will be sending spares for you to play with. The spares I am sending either have broken feet, or bad regulators. The regulator can be replaced so if you make one you really like. I can swap the regulator. I feel that the way you want to display the car, you should:
1) blank off the factory regulator to use the cooler looking regulator that will also give you a fuel pressure gauge.
2) Once you have a fuel rail modded like you want, have it chromed.
3) Be careful of those little feet. They are delicate. Once the system is in use and tightened they arent a problem, they tend to break when tightening the banjo bolts or if they get dropped.

With the AN Fittings you could use an AN to Barb connector and rid yourself of banjo fittings. >>>


Here's some pics:

Engine Auto part Vehicle Fuel line Car
Auto part Engine Vehicle Carburetor Fuel line
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#4 · (Edited)
Cautions, questions, suggestions, and comments welcome!
Of course some will pipe up to get rid of the Opel fuel rail completely and make yourself a fuel rail..

Which isn't "too" hard.. (For them if you have the tools, etc... )

BUT I personally think it's a lot of effort and cost when the Opel one works and is designed for our intakes.. But thats me.

Maybe you can retrofit a pontiac one.. ?

https://www.edelbrock.com/fuel-rail-kit-low-profile-pro-flo-efi-6an-for-pontiac-torker-ii-3637.html
 

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#5 ·
I'm okay with the Opel fuel rail for now. As long as the one I get will clean up and chrome decently. It IS made to fit and I won't have to rig up my own brackets for an aftermarket one. I'm open to alternate ideas, though.

What's that round thing sitting on the square extrusion? That seems awkwardly placed. Is that the factory regulator that you suggested I block off?

I don't enjoy tapping things, even though I have a 3/8" NPT tap in the basement. If that is the factory regulator location and you suggest blocking it off, maybe you could give it to your machine shop and have them delete or block it off, welding or otherwise, AND tap the fuel line locations for 3/8" NPT? I could certainly make my own block off plate, but if I'll never need to ever remove it, why not just weld a plate onto it or cut it down some and weld it up? If all of this is the case, why not weld it up and delete that area as a possible leak source and make a cleaner look?

Differing opinions?

:thinking:
 
#6 ·
Your idea of using a large fuel filter for the swirl pot will not work. If you suck air into the fuel system from the tank you will still wind up with bubbles in the fuel line which naturally is a no no. The idea is to never allow the suction side of the fuel pump to be sucking air. Once the air is in the system you are cooked. I don't know if you can get into your fancy fuel tank but if you can there is another alternative that RallyBob turned me on to and I used in my car. (Ignore the "not for fuel" hose, it was only used to mock the system up). These pickups close off if they are uncovered by fuel so I put one one each side of the tank so that if one becomes uncovered and seals itself the other will supply the fuel.
 

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#8 ·
I think that's a bit hyperbolic, maybe if your turning 5000 RPMs and hit a hard corner at Summit Point Raceway.. But that's doubtful to happen on a street car.

I ran the system of an expansion tank no problems. The fuel system was dry and full of air a dozen times as I was testing fuel pressure regulators and was messing with things.

The air will either get compressed and shot out the injector or the bubbles will find their way into the tank via the return line. Air compresses quite easily, fuel does not.

OR

The motor will shut off as you are out of gas.

Consider its a 45 PSI system, flowing 20 LBs of fuel a minute. Its flowing so much that a glup of air won't even be noticed on a street car.

The Fuel pump is a 100 GPH, the car only uses 3 GPH ( at 60 mph).. so I think the system will recover from a loss of fuel for a split second.

Also for Gordo to be that low on empty for it to even happen I just don't see it.

Now could he burn up a fuel pump or something running out of gas ? Sure, could just get in a carb when the same thing happens ? Yep.. thats why its not good to run out of gas. But a Surge tank won't help him when he runs out of gas.

Kadett hasn't had a surge tank and ran for a year or two with a nothing more than teh return line going into the back of the fuel pump. THe only problem I had with that was the fact the fuel didn't have time to cool down so it made for a loud and unhappy fuel pump. Which is why I went with the in-tank fuel pump... Which is SOP for modern cars now.

The heat of compressing the fuel to 45 PSI an and running around in the rail above the exhaust manifold is a bigger problem than a little air.
 
#7 · (Edited)
I talked with Charlie and the blue AN fittings shown in one of the pics WILL screw into a standard Opel fuel rail. Maybe they're metric, maybe they're NPT, but they're from Earl's so I'll figure it out. Same for the regulator location, I'll figure something out.

I looked at fittings all morning and ordered some caps and sleeves for the copper/nickel fuel line I also bought and I also bought some Gates hoses for the flex lines. I'm going to wait on ordering the AN fittings for the hoses until I resolve the layout of things. We might use a BMW fuel pump with large filter that Charlie has to act as a pseudo surge tank.
 
#9 · (Edited)
#10 ·
Look at Pictures

Why should I show up pictures here when I show up all mine whole fuel lines and fuel pump unit in my thread. So that show me again that nobody will look there:ugh::thinking:
I have also pictures from install the LE-Jetronic computer with the big hole and the 2.2 ignition modul.
Only the 2.2 have this ignition modul what need two relais too_One for electric impuls and one for pressure impuls.
By my swap all those works are done allready:lmao:
 
#12 · (Edited)
Why should I show up pictures here when I show up all mine whole fuel lines and fuel pump unit in my thread.

By my swap all those works are done already..

So that show me again that nobody will look there!
Oh stop whining! :crying: :slap: :nana:

Of course we look at your pictures and learn from them. But you are Germans and Germans always do things the pain in the azz way because of the TUV.

We are Americans and Americans do things the stupid simple way.

:lmao:
 
#16 · (Edited)
Oh stop whining! :crying: :slap: :nana:

Of course we look at your pictures and learn from them. But you are Germans and Germans always do things the pain in the azz way because of the TUV.

We are Americans and Americans do things the stupid simple way.
Okay
Here in Old Germany we will have not your problem with the fuel temp.
But I know that the 2.2i have problems with the normal fuel pumps in hot countries.
So you only have to buy the Opel Pump part number 815006 or GM 9140207.
That is the Opel Factory Fuel Pump for Hot Countries on a 2.2i engine with the ignition modul.
If you have this pump you can be happy with no drop down pressure.

I think Norbert buy the last one here.Maybe it can warm up here in Germany:drive:
Have them is better as search them.:nana:
 

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#11 · (Edited)
WOW!

That's it! That sounds like the solution to everything. All the individual stuff you would need to buy to convert the fuel delivery system to FI all in one and just a vent hose back to the tank! The cost is comparable to all the stuff you would need to buy to go the individual device route.

I wonder if the pump is replacable if it goes bad? I'll betcha it is. :veryhappy

I like Edelbrock, too. Their low pressure fuel pump I got not too long ago works and is designed so well and is so low noise that I've fallen in love with that company.

Wow, it appears that I could get rid of all the pumps and filters under the car and run a hard metal line straight to the tank, then just a vent hose spliced into the existing vent lines or directly to the tank. No worries about high pressure fuel leaks inside the passenger compartment. No screwing up your 50 year old tank.

I could probably fit it on the driver's side of my engine compartment where my MSD box used to be or, better yet, somewhere in front of the radiator wall where it is cooler!

Oooo! Oooo! Oooo! I really like this!

Thank you so much Commodaren!


Okay, now you guys can shoot holes in the idea and say it will never work and my car will blow up.


:lmao:
 
#14 · (Edited)
Here's a nice synopsis of my thinking when someone suggested that I'm making this more complicated than it needs to be:

<<< What could be simpler than an all-in-one system that you can mount in or near the engine compartment? Why do I have to buy an individual new pump, new regulator, new filter, run new lines the length of the car, mod the tank or add gizmos to it, or get/make an individual surge tank concept, have multiple connecting hoses and fittings, and have most of that junk inconveniently placed under the car, when I can deal with all the issues of adding FI with a 9"x4"x10" unit that I can mount 2 feet away from the engine in the vast empty cavern in front of the radiator or on the driver's side of the engine compartment? Heck, I already have a decent newish metal fuel line running most of the length of the car, I would just need to remove and toss the present low pressure fuel pump and filter and extend the metal line to the tank. Maybe flare the ends for AN fittings. I've already ordered Gates hose and copper/nickel hard line, plus the AN caps and sleeves to make the hard line AN friendly, so I could theoretically run a single new hardline the whole length of the car from tank to the everything in one place assembly with only one unbroken hard fuel line from the tank and a flex line to the FI fuel rail. And it's a matched and tested system made by a car company that been around for like 75 years, instead of a whole bunch of cobbled together gizmos and widgets that are unproven to work harmoniously together. There's a nice empty spot for it below the brake booster in my car, where it will stay nice and cool and protected: >>>

Cable management Electrical wiring Wire Fuel line Cable
Auto part Technology Automotive fuel system Electronic device Automotive engine part
 
#15 ·
At this time, I see only one possible issue: Fuel heating up because it doesn't get returned and mixed with the cooler fuel in the tank. It apparently uses a sump-type fuel pump that gets cooled by it's immersion in the fuel reservoir. That might be great for pump longevity, but how hot will the fuel get if I'm stuck in traffic? How hot does fuel have to get before it creates a problem? How likely is it that the fuel will get hot enough to cause a problem with this system? That issue is another good reason for me to mount it in front of the radiator wall between my tranny cooler fan and my radiator fan, coupled with my engine fan which would constantly circulate a little air in that area. If I'm stuck in traffic on a hot day, all 3 of those fans will be in action and air will be swirling all around this unit. One would have to think that Edelbrock considered this issue and it's either of very little concern or the unit has cooling fins or other things to diminish the risk.
 
#18 ·
I bought it.

:banana:


Interesting.....the description says.....

<<< These Universal Sump Fuel Kits are designed to provide the necessary high fuel pressure required for EFI applications in vehicles equipped with an existing low pressure carbureted fuel system. They are a complete self-contained system that can be easily installed under the hood. The unique design of these systems allow them to deliver a constant fuel pressure with no fuel return line, external fuel pressure regulator or fuel tank modifications. They are compatible with the existing factory fuel tank and pump. They are ideal for use with aftermarket EFI systems and with many popular engine swap applications that require constant 35-90 psi fuel pressure.These Fuel Sump Kits feature a compact design that is adjustable from 35 to 90 psi and include a vacuum reference port. They are available in a 67 gph flow rate and can support up to 600 HP. They're great solutions when used with a Pro-Flo 3, Pro-Flo 4 or other aftermarket EFI system. Complete kit #36031 includes a durable, lightweight plastic fuel sump tank with high pressure fuel pump, wiring harness, hose and fittings. Fuel Sump Tank Assembly #36032 are for builders and consumers that want to utilize their own hose and fittings. Will require the installation of a vent line from the sump overflow vent port to the fuel tank. Edelbrock Universal EFI Sump Fuel Kits are the most affordable way to make your fuel system EFI ready. >>>


I wonder if this means that you can leave your existing fuel pump fully connected and working? If this is true, your existing low pressure electric fuel pump could possibly do most of the grunt work of pulling the fuel out of the tank and pushing it forward to the high pressure pump which would only have to pressurize the last 2-3 feet of hose and the fuel rail. Theoretically I could do absolutely nothing to my existing low pressure fuel pump and filter, they're not subject to the high volume and pressure of a recirculating system. In actuality, only the amount of fuel that the engine actually uses would flow through the system.......and that ain't much.

Or maybe that comment in the description just means that you don't have to remove your in-tank fuel pump and you could disconnect the power from it and the pump in this unit will suck the fuel through it.

I'll bet it's the first one.

This unit employs a concept that we're not used to seeing. It's not a circular high pressure system. It's only a high pressure system from the pump to the fuel rail. There's no fuel returning to the tank at high pressure or flow and there's no high pressure or flow from the tank to the pump. It totally makes sense when you think about it. Why push all that fuel around when all you're trying to accomplish is high pressure at the injectors? My present Edelbrock pump is regulated to 2.5 psi and I'm told that 40-45psi is what the Motronic system wants. That's almost 20 times the pressure through almost the whole system. As long as the pump is designed or capable of pushing with 40psi of force, but not actually flowing anywhere near that much fuel, all will be well. A good company designed it and I'm sure there's others like it, so it must be a workable principle.

:veryhappy
 
#19 ·
This uses a low pressure pump as a lift pump to feed this remote sump. The instructions say 7 psi max pressure from the low pressure pump; this lift pump can be an engine driven pump or one in the back or one in the tank. (In-tank would not normally be a low pressure pump.)

It reads like the regulator fuel bypass dumps internally right back into this remote sump. But the instructions show a return line with this. It reads like this is for some sort of overflow situation, but it is described as 'not an option' in the warnings.

Can't tell from the info if this is a plastic sump or what. Where to put it becomes a question.

FWIW: To clear up any misconception, there is NEVER high pressure in the return line from a standard regulated FI system. There is only a fraction of a psi to a few psi MAX in the return line, with the maximum right at the regulator return port.
 
#20 ·
And it sounds like you are using the Motronic 1.5 system? I wanted to read up on that for education, and saw that the fuel range pressure in that system ranges from 2 to 2.5 bar(g) and that is pprox 30 to 37 psig, with the 37 psi as the 'baseline' setting. I see that this remote sump's minimum pressure regulation is 35 psi or about 2.4 bar. So it looks to be right on the edge of specs for that pressure range. If this is the baseline setting range, then that's in range, but you might want to see if the pressure regulator can work down to 29-30 psi output (2 bar(g)) with full vacuum applied to the vacuum compensation port. (You guys might have a different plan for the pressure range but just wanted to point this out before going too far.)
 
#21 · (Edited)
Well, it's questions like that that I have no knowledge of my own to answer with. I have to rely on others, this being primarily Charlie, to handle the set up requirements and adjustments. I don't think we have Opels with Motronic in the U.S., so it's not that easy to dig up info on them. Yeah, Charlie's a knucklehead:)veryhappy), but he's the only knucklehead I have to work with to set this system up for me. With me, that means we have 2 knuckleheads, plus the entire Facebook and Opelgt.com community(aka: The Peanut Gallery) chiming in. Actually, one wackadoodle, one knucklehead, and a bag of peanuts.

:lmao:

Yeah, I would have been more comfortable with the regulator in this device having a slightly lower minimum pressure threshold. But the pressure I'm told I need is within the spec'd pressure range, so who am I to question it's suitability.

I was curious as to what the purpose of the vacuum port is.......

:thinking:
 
#22 · (Edited)
System is rated to runs at 35 to 45 psi..

That said, the Opel fuel pressure regulator is about 45-50 PSI.

There wasnt a lot of variance amongst the 10 I tested.I had a few at 25 ( and they leaked ) a few at 0 ( They shot few out of the vacuum connector ) and the rest were all steady at 50 PSI.

SO I don't think its super critical. I think the system is rated at 45, but the fuel pump and regulator care meant to be able to vary under load, so at idle 50 or so is correct.

Long story short all Bosch style MPI run the same way,

BUT the Motronic, is also controlled by the O2 sensor and AFM.. Remember the injectors if flowing too rich, the EFI can shorten the number of pulses it uses to compensate.

The vacuum will also control the regulator by dropping/increasing the pressure.

 
#23 · (Edited)
Gotcha... I just saw a Motronic 1.5 system description and it said 2 to 2.5 bar(g) (29 to 37 psi). The L-Jetronic varsion used in the '75's runs pressures from 35 to 43 psi... which sounds like this FI system's design pressure range. And yes, the ECU can adjust the pulses to the O2 sensor readings but it can only compensate so much; injectors have mechanical and electrical limitations at high and low flow, and you want to keep them in their designed-for operating pressure and pulsewidth ranges. Any ECU programming ASSUMES a certain injector behavior in it's mapping. So if you want to 'plug and play' with a set ECU program, then you ought to duplicate the designed-for setup.

As for the vacuum port on this remote sump's pressure regulator, it is doing the same as the vacuum port on any injection system regulator (like the one's Charlies reports testing) ..... it varies the fuel pressure based on intake manifold pressure. The variation is done so that the difference in pressure from the injector's fuel inlet to the injector outlet is a constant value. This takes out one variable in the amount of fuel that gets injectedby keeping the injectors working at their design pressure, and makes the system work better. (And is 100% vital for an older injection system like the L-Jetronic with no ability for the ECU to make O2 based adjustments.)

At idle, the manifold pressure is negative relative to atmospheric and so the vacuum at the regulator's vacuum port causes the regulator to lower the fuel pressure to the injectors. As you open the throttle more and more, the manifold pressure level rises (the vacuum reading goes lower) and the regulator increase the pressure to the injectors to compensate.

It sounds like Charlie tested those regulators with the vacuum port open to atmospheric pressure, which is like WOT on the engine. So that 50 psi is the WOT pressure output. If a vacuum source is attached and the vacuum increased (pressure going negative, or lower), the regulator's output pressure will drop if it is working right; complete regulator testing includes this check.

The regulator's output pressure will vary at the rate of 1 psi for each 2.04" change of vacuum pressure. So in operation, a regulator with 50 psi at WOT should be around 43 psi at idle. I'd expect the Edelbrock's remote sump regulator to mimic these pressure changes if the manifold vacuum is connected to its vacuum compensation port.

This setup is also used in turbo cars.... with the same rate of pressure change under turbo pressure as when the engine is drawing a vacuum. The purpose is the same: to keep the inlet to outlet pressure fairly constant across the injectors.

The nice thing about this Edelbrock setup is that you can adjust the baseline pressure (WOT pressure) AND it has the vacuum compensation port. Personally, I would use this Edelbrock regulator in a heartbeat versus the stock ones with a fixed 50 psi baseline pressure so you can start out in the proper pressure range.

And sorry for being so long-winded.... this stuff is interesting!

Edit to add: I see Charlie posted a video on the pressure regulator...nice! Watch the whole thing: the test at about minute 18 shows the pressure change vs manifold vacuum.
 
#25 ·
It sounds like Charlie tested those regulators with the vacuum port open to atmospheric pressure, which is like WOT on the engine. So that 50 psi is the WOT pressure output. If a vacuum source is attached and the vacuum increased (pressure going negative, or lower), the regulator's output pressure will drop if it is working right; complete regulator testing includes this check.

The regulator's output pressure will vary at the rate of 1 psi for each 2.04" change of vacuum pressure. So in operation, a regulator with 50 psi at WOT should be around 43 psi at idle. I'd expect the Edelbrock's remote sump regulator to mimic these pressure changes if the manifold vacuum is connected to its vacuum compensation port.
Good catch, hadn't thought of that.. also you may have answered my question I had at the 2.6L break in..

Why was I running rich ? I thought it was the 02 sensor not getting warm enough and too much flow through the AFM.. ( I STILL think that was part of it.. )

BUT these motors also by design have less idle vacuum.. so.. there is that added issue. Which is why I am probably going to ditch the Opel fuel pressure regulator at the next start up and go with an inline so I can regulate the pressure better..
 
#26 ·
You're welcome.. Less vacuum is not any issue.... as long as the pressure regulator has the vacuum connection, it will do its job and compensate for the intake manifold's pressure difference, be it high, low, or in-between. I have not run into a pressure regulator (yet) that changes pressure in any other fashion than 1 psi per 2.04" if vacuum, but they may exist. I'd like to hear what you may consider for a replacement pressure regulator.

Now the AFM possibly being off is a whole 'nother matter....

All the following is 'FWIW':

AFR readings based on O2 sensors will be LEAN when cold, not rich. Factory ECU's run in 'open loop' mode during warm up, meaning they ignore the O2 sensor and approximate the fuel injection until the engine coolant temp sensor gets high enough.

The lean AFR reading of based on O2 sensors in warm-up may be counter-intuitive, as we think of rich mixture during warmup. The reason is because O2 sensors do not actually read intake mixture; they only read free oxygen levels in the exhaust (lamba) and the system interprets that as AFR in the intake. During warmup, some fuel stays in liquid droplet form, and so does not burn and passes out of the exhaust. Because some of the fuel does not burn, then there is a higher level of free oxygen in the exhaust during warmup, and the O2 sensor measures a low lambda value, which is interpreted by the system as lean.

If the ECU tries to use the false, lean O2 sensor info during engine warmup, then it will adjust the mixture too rich.... so it ignored until the engine is warm.

And: The O2 sensor is not needed for an FI system BTW. The L-Jetronic, K-Jetronic, and other early FI systems, both electrical and purely mechanical, did not use an O2 sensor. The O2 sensor is there primarily to fine tune the system for emissions and fuel economy. The O2 sensor, plus a knock sensor, are also used to detect abnormal conditions to try avoid engine damage.
 
#28 · (Edited)
Yep which is why I am leaning towards the rich at breakin was due to an inaccurate reading of the AFM, due to lack of back pressure.

I had a steel headpipe with thin wall flexible pipe, and only a muffler on the end. So long story, I am sure the AFM wasnt reading a 100% accurate, and it was a new one I had.

Add to that the factory would have had it centered in the cast iron, where my setup had it in a cooler section of the exhaust, after the engine got hot. So while the 02 sensor may not have a lot to do with it.. it ran richer as the motor warmed up.. which kind of goes with what you are saying the computer stayed lean at startup.. but once warm it went too rich.

I did like the fact the old Jetronic didn't have a O2 sensor.. but found they run a little rich themselves with headers.

I would LOVE to find an Opel Motronic system I could modify that used the knock sensor too.. that would be helpful on a few cars.

Next time I will get my AFR reader out and test the system. After Gordo mails it back to me.
 

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#32 ·
Just two the ECU ( Computer ) and the Fuel Pump/O2/ECU relay.. its just a combination relay. I DONT wire the EFI fuel pump to it and run it off a keyed relay. That way I dont have to worry about the old relay taking a dump.
 
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#31 ·
Charlie and I are digesting what ohmage coil you could use with the Motronic system. I've got several very low ohm coils, one I think is a .34ohm one from Pertronix and the other is a very low ohm one from MSD. Charlie favors the one that came with the Motronic system and he doesn't want to gamble on a slightly different ohm aftermarket coil possibly messing up the computer. I think he checked the ohms of some of the Motronic Bosch ones he has and I think he said they were somewhere between .6 and .9 ohms. Charlie also favors the original coils because the wire harness will connect to them without modification.

Any thoughts on this?

:thinking:
 
#34 ·
Charlie and I are digesting what ohmage coil you could use....:
No.. WE arent.. ?

I have about 20 of the coils, new and used.. I see no need to try to use a coil not designed for the system. These are old ECUs, they are tough, but as I a mechancial engineer and not an electrical one, I just know your not supposed to do anything that could let the magic smoke out of them.

Partly why I use modern relays to run the fuel pump, that way I dont stress the old components that are harder to get. Like ECU and Opel specific Relays.
 
#51 ·
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#41 ·
Where to put it? Part one

To celebrate my 60th birthday I went home 2 hours early from work and decided to test fit the pump system(birthday gift to myself) in various locations in my engine compartment.

Passenger side:
Putting it on the passenger side doesn't seem to be an option, although with the absence of the heater box I could probably fit it and the hose to the fuel rail would be about 12"-18" long. But that would place it too close to the hot exhaust. The housing is plastic. The FI manifold, MAF thingy, cold air intake, and filter will pretty much take up all the remaining space on that side of the engine to the front of the radiator wall. Putting it where the heater box was would really congest that side of the engine.

In front of the radiator:
I could only fit it on the driver's side between my electric radiator and auto tranny cooler fans. The passenger side has the battery, MAF thingy, and K+N filter. Here's a few really lousy pics of it in various positions on the driver's side:

Cable management Electrical wiring Wire Fuel line Cable
Vehicle Motor vehicle Car Fuel line Auto part
Engine Auto part Vehicle Fuel line Car
Vehicle Motor vehicle Engine Auto part Car
Auto part Automotive lighting Vehicle Engine Car


That's a great place if I wanted to hide it and the hoses running to/from it. It would be cooler there, with fans that would both kick on if I'm stuck in traffic. Mounted all the way down at the bottom as my pictures show would be a PIA install and difficult to access, plus it would add interference to my already compromised radiator air flow. I could, however, move my chromy radiator overflow bottle to a different location and mount it up high where the bottle is, more or less next to the brake master cylinder. Ease of access, low temp location, hoses mostly hidden. I already have a passageway through the radiator wall for routing hoses to and from it, but adding 4 more hoses(fuel in/out, vent, fuel pressure modulator) would be kind of nasty. Maybe some hoses could pass through an area on the passenger side(fuel out and modulator). I'll have to remove my overflow bottle and see how things look.

Driver's side where the windshield washer bottle normally is:
The driver's side of my engine compartment is pretty empty. I've never liked how my wire routing in that area turned out. It's an embarassment. With the removal of my MSD box, plus the addition of my under car/hood LED lighting wires, that area is now an eyesore. Not car show worthy. The passenger side will be packed full of stuff and the driver's side looks like an empty suitcase. If I remove my now useless Edelbrock low pressure fuel pressure regulator, I can fit it in the space remaining with no room to spare and possibly touching stuff, plus I'll have to make a big high bracket to attach to it's 3 mounting tabs. I'll have just enough room to close my hood with the in/out fuel hoses fastened in place. Here's pics of that configuration:

Vehicle Auto part Engine Car Fuel line
Engine Vehicle Auto part Car Fuel line
Vehicle Engine Car Fuel line Auto part
Vehicle Motor vehicle Engine Auto part Fuel line
Land vehicle Vehicle Motor vehicle Car Auto part


It a good spot for hiding my wiring, running the hoses to and from it, but it's too close to my wiring, would be hard to adjust the regulator and it barely fits with me wedging it in there. I'd have to elevate it 1/2" or more for clearance, but then hood clearance becomes dicey.

(next post)
 
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