(S//NP)Bosch K-Jetronic

[CTX-SLPR]

Howdy,

Any Bosch CIS/K-Jetronic guys around here? Due to class rules at Bonneville, I have to run mech injection instead of the EFI I would prefer. After reading up on it, first as a potential boost adding fuel circuit, I think I'm actually just going to run a whole dang system on the car with the mechanical MAF and fuel distributor.

I picked up the lower section from a 92 Mercedes 300E because I didn't have time to pull the complete unit from the other car as I needed to get back home. I'll probably do that sometime soon when I get a chance to go back. I'll just give them the lower section to hold and exchange it for the whole deal once I get it out. The other option is to use a V8 unit since it has more air capacity and marginally more fuel capacity when you factor in that I'm only using 6 of the 8 fuel ports. Considering that the 300E made 217hp, I'm hoping that I can get 350hp worth of air through the AFM without it bottoming out. I've taken it apart (sorry batteries in the camera are dead) and it looks like I could stiffen up the return spring on the air door in the AFM to increase the range of mass air it will sense and correspondingly up the fuel pressure to restore the ratio. From my reading, there also might be higher fuel flow distributors out there that I could swap for to get the flow up at the standard ~53psi system pressure.
The one car that should have had the V8 unit at the yard had already had it's AFM and fuel distributor taken but I did get the bigger V8 injectors off the car. They are roughly the same diameter as EFI tips and fit into rubber mounting boots that do fit nicely into EFI bungs but since they are ~4.25in long, they stick way through the holes. I think I'll either whip up adapters that fit with O-rings into the EFI bungs on the intake and the injectors at the top or thread the bungs and screw in the injector carriers into the intake.

Anyone ever played with one of these systems?

[dieselgeek]

I would double check that system is not considered "EFI" by the SCTA/ECTA before spending any time on it.

[Beagle]

I wondered about that myself - the K was mechanical though. The D- and KE- had ECU and later versions picked up closed loop operation courtesy of an ECU. The K-Jetronic was hydraulic/mechanical based on the manual (page 12)

http://www.scribd.com/doc/3299223/Bo...jection-Manual-

I'm concerned when you pick up the later stuff that incorporates an ECU, it's not gonna fly with Tech.

[SpiderGearsMan]

this would be sick

[Barry Donovan]

I wondered about that myself - the K was mechanical though. The D- and KE- had ECU and later versions picked up closed loop operation courtesy of an ECU. The K-Jetronic was hydraulic/mechanical based on the manual (page 12)

http://www.scribd.com/doc/3299223/Bo...jection-Manual-

I'm concerned when you pick up the later stuff that incorporates an ECU, it's not gonna fly with Tech.

that is a great read. Not to invade the thread.

the ratio stuff is right in the beginning

is it me or did they come with 13.2 AFR as ideal?
I derived it from a graph.

I have heard the bosch stuff called one of their variants monojet, and that is incorrect. the book even calls it "monojetronic"

monojet is Rochester...older than a jetski.

in the bosch stuff, if there is any loss in manifold, the fuel dies.
why not carb it.

[CTX-SLPR]

I would double check that system is not considered "EFI" by the SCTA/ECTA before spending any time on it.

Good point, I'll find my rulebook (3yr old ran off with it I think)

I wondered about that myself - the K was mechanical though. The D- and KE- had ECU and later versions picked up closed loop operation courtesy of an ECU. The K-Jetronic was hydraulic/mechanical based on the manual (page 12)

http://www.scribd.com/doc/3299223/Bo...jection-Manual-

I'm concerned when you pick up the later stuff that incorporates an ECU, it's not gonna fly with Tech.

I did pick up a later AFM from a KE system but it looks like the only thing that's different from the earlier K stuff is there isn't an adjustment on the AFM lever arm for richening or leaning the whole curve. You might be able to still do it with some creative modification but otherwise the AFM looks good. I was worried about the KE or the K-Lamba stuff but from reading k-jet.org and a bimmer forum, the O2 controlled frequency valve just goes to 100% at WOT anyway. It's just a start, not planning on making this my final parts unless I think I can make them work. Definitely get the word from Tech before sinking anymore money in.

[Beagle]

http://turbobricks.com/forums/showthread.php?t=168170

some place called unwired? I fell on this looking for something else today. Might be worth a look.

[CTX-SLPR]

http://turbobricks.com/forums/showthread.php?t=168170

some place called unwired? I fell on this looking for something else today. Might be worth a look.

Looked it up, it's like megasquirting the warmup/control pressure regulator and that's class illegal.

Wrote in to the SCTA Classic POC and sent him a YouTube link on how the system works and pointed out that I'm not going to be using the K-Lamba or KE-Jetronic systems, just the classic K-Jet. Also read that document you linked Beagle, good section in there on the AFM's "cone tuning" principles. Got enough of a warm fuzzy that assuming I get an official "YES" from the SCTA, I'll get the rest of the parts to at least try and run the 3.8L core motor before I tear it down.

[CTX-SLPR]

K-jetronic MFI approved if I pull everything out that's electrical, bimetallic springs and associated heaters to slowly turn things off after start up, from the system. I could probably argue with them about the heater functions since carbs have bimetallic heater pull offs for chokes but I don't feel like doing that quite yet as a newbie with the belief that I can make it work without it. Since there seems to be a roughly 200% of original power rating limit for how much fuel/air they can handle, I'm actually planning on running a pair in parallel since the 300E's are rated at 215hp to start with and a pair of them would give me 430hp, more than my 375hp max target, without getting into "overage" capacity. This is nice since it means the meters and distributors will be running in their normal range and I hopefully will be able to tune it more like a conventional K-jet with a boost sensitive enrichment valve instead of playing games with the meter to get more air flow range out of it.

This next week I'm going to head to the junkyard and pull another 300E setup which was complete last time I was there and go hunting in the SAAB and Volvo section for a warmup regulator with boost enrichment to take apart and start playing with. Definitely going to have to invest in the tools needed to flare the lines for this setup as hard lines are much cheaper than braided hose and with 12 injectors and a myriad of supply and return lines, it will get expensive in a hurry if I'm not able to make my own.

[dieselgeek]

I like the idea of dual units so that you keep so much of the original design engineering in spec (airflow per inlet, etc). The only thing that would concern me is now you are tuning just like a carburetor. Make sure you can make a global adjustment for the 11-14% difference you'll see at sea level (or therabouts) density altitudes versus the 5800-7200' DA you'll find at Bonneville. You will want an onboard O2 sensor just for logging, and they'll allow that at Bonneville. Just not closed loop.

[CTX-SLPR]

I like the idea of dual units so that you keep so much of the original design engineering in spec (airflow per inlet, etc). The only thing that would concern me is now you are tuning just like a carburetor. Make sure you can make a global adjustment for the 11-14% difference you'll see at sea level (or therabouts) density altitudes versus the 5800-7200' DA you'll find at Bonneville. You will want an onboard O2 sensor just for logging, and they'll allow that at Bonneville. Just not closed loop.

Oh I'm going nuts with the datalogging, wideband, MAP sensors, IAT sensors, coolant sensors. Even thinking of putting in an Infinity (or Ford) voltage MAF's in the outlets of the AFM's to measure both the balance between meters and the total air flow to line up with the WBO2 data to see if it needs changes. Planning on using an Aurdino since it has more inputs and can fire off warning lights, I wish I could use it to trigger something like a blow off valve if I got into overboost or the oil pressure cut out but not allowed. If driver/amplifier boards and good quality sensors weren't so expensive I'd put EGT's on all the cylinders but that's like $500 in sensors alone!

Since the AFM's are mass flow sensors not pressure sensors, does the DA really need to be corrected? I don't dismiss your idea in the slightest, just am thinking that the system might be self correcting in that regard. Also I'm at pretty much the same or higher altitude as Bonneville here in Colorado so that does make tuning easier.

[CTX-SLPR]

Injector Placement

So I have enough parts on hand now to start mocking up my intake at least conceptually. The hard part is squeezing 2 of the blasted things into each runner on the intake I have. Now the injectors aren't very big, 0.355in or 9mm in diameter with 1/2in or 12mm head on them. They will fit in 3/8in compression fittings but a 3/8in compression fitting big enough to pass the whole injector through takes a 5/8in head on it and there just isn't enough room on the current injector shelves for that.
Now I don't have the ability to weld aluminum and I really don't want to farm out that job either. I need to fit two of them into each runner since running twice the pressure to an injector is not going to result in a linear fuel curve I have the very strong feeling of. Both injectors would run at all times as well with the doubled fuel systems.

My thoughts are to put a single injector in each runner at the normal EFI location by using 3/8NPT to 3/8in Compression adapters threaded into the EFI bungs. The second set of injectors would be mounted up at the top of the plenum basically fogging into the whole plenum or up in the top of each runner. I don't need this thing to have a smooth low rpm idle, I just need it to idle well enough to warm the engine up before a run and honestly a high idle will help ensure I have oil to the solid flat tappet cam during this time as well.

Here's the intake with a general idea of the upper plenum:

Second set would be either in the baseplate of the upper plenum or in the top 1in or so of the runner just below the mounting bosses. This is an "air gap" style intake and the runner inlets are raised off of the plenum floor if that makes any difference.

Thoughts?

[SpiderGearsMan]

q jet fits the rules

[CTX-SLPR]

I'm not drawing through and blowing through a Q-jet is not a good idea....