HPSI black box for L Jetronic

[rickyellow zee]

http://www.ebay.ca/itm/BLACK-BOX-Fuel-Control-Unit-Datsun-Toyota-Fiat-AlfaRomeo-BMW-L-Jetronic-/351427381142

I came across this "black box" fuel controll unit while doing research on bosch L Jetronic AFM's the other day. My guess is it alters the output voltage coming from the sweeper arm in the AFM and tricks the ECU in thinking theres more or less fuel. Not sure but it looks just like a potentiometer and the installation calls for splicing into only one wire. It seems to do a good job in the vid of leaning out the guys air fuel mixture in the upper rpms. Now it was my understanding that the ECU dumps a set amount of fuel past 3500 rpm and cannot be adjusted. Any ideas how this box might work? I may try and splice into my AFM return signal wire and add a pot to see if I can alter the air fuel in the upper rpms. Your thoughts on how this product works??

Thanks

[jeffer949]

HAHAHAHA  200 bucks for a that?  This is an old trick people have been doing for years.  http://atlanticz.ca/zclub/techtips/tempsensorpot/index.html

[NewZed]

Looks like this  - http://atlanticz.ca/zclub/techtips/tempsensorpot/index.html

 

I don't see how he can monitor RPM and control the "fuel level signal" using just one wire.  Looks like it's just the coolant temperature sensor tweak.

 

Looks like an average guy who's trying to make a few bucks off of the mystery of EFI.  It's Innovate not Innovative.  "Stage 2" injectors?  Rear muffler delete?  Implying that the black box shuts off at cruise but attributing control to the O2 sensor.  Don't look behind the curtain.

 

 $200 for a potentiometer and some wire.  Easy money.

 

http://www.hpsimotorsports.com/

 

"   Two factors can be adjusted. You can control exactly when the system signals the ECU to send in more fuel and you can alter how much extra fuel is added. The amount of fuel is not infinitely adjustable however we include 25 settings which will provide enough range of adjustment for almost everyone. The device on my car is set to trigger at 5500rpm and adds enough fuel to handle 10 pounds of boost on my Alfa Romeo 2.5L with Stage 2 injectors. Keep in mind, in stock form this car is normally aspirated, so that's 10psi over stock. Without the device the car starts to lean out at 5500 rpm and would be dangerously lean by 6000 rpm. Now at 5500 the car accelerates noticeably harder and the mixture stays in line up to 6500+ rpm.

Installation

     -Installation is simple and only requires one wire on the car to be cut. It does not require removal of the ECU, soldering or anything else. It's very small and can be hidden or mounted just about anywhere.

What's in the Black Box Kit?

     -Everything pictured in the kit is all you will need to get up and running. Pictured above is our Black Box control knob mounted on a gauge set we installed. You are free to mount and install anywhere you would like

     If you want to make this box yourself and save some money, instructions are included in my supercharging book, available on this site, or on our website.

[rickyellow zee]

The ol CHTS trick eh? I thought it might have been something different like controlling the AFM signal wire. That could work as well..... The thing with altering the CHTS wire is that the ECU only reads the CHTS in certain conditions. At around 3500rpm its no longer used, goes by the ECU map. How was he controlling fuel past that? 

[NewZed]

Find out what the "one wire" is and all will be clear.  The L-Jetronic system is very simple.

 

I think that he's playing word games, implying that the "black box" is controlling by saying that the O2 sensor takes over.  Lots of technical jargon intended to add sophistication to a simple system.  I'd say it's a scam, but it will work.  It's meant to take advantage of people who don't do their own homework.

 

The ECU always uses the sensor signal.

[rickyellow zee]

So the CHTS DOES plays a role in how much fuel is sent at all times. Interesting. From all the posts I've read recently I was under the impression that it goes on a "set map" after 3500 regardless of sensor input. Dumps a certain amount of fuel only tweakable by the FPR.  Learn something new every day!

 

When I purchased my car a few years back the previous owner was using the stock 78 ECU/AFM with an 83 L28ET swap by adding a resistor to the CHTS wire. It worked but only at partial throttle. Since then I have converted to the right ECU and AFM. 

[rickyellow zee]

Find out what the "one wire" is and all will be clear.  The L-Jetronic system is very simple.

 

 

Ive researched and cant find the answer. I figured it was a scam.

[NewZed]

Nissan gives somewhat conflicting information about "full enrichment".  They say it's 27% more than the base pulse, but say that the base pulse is before the other enrichments.  Then show a chart with full on top of, after, the other enrichments.  I think that they mean an extra 27% of base pulse is added on top of all other enrichments.  Everything derives from the base pulse.  No RPM set point, it's all base pulse plus enrichment with one big jump due to throttle position, at 30 degrees (the 280Z have idle, nothing, and wide open settings).

 

[rickyellow zee]

"the increased amount of fuel is constant when the temp is 70 deg C" but correction by intake air temp is always monitored. It would make more sense to hack into this sensor to adjust fuel one would think. This is what is shown on the graph above. Maybe my perception is wrong. Meh, old technology. 

[Tony D]

The 'fixed map' above 3500 is correct, but there is still temperature correction. Foolish to think it wouldn't have it--think of an engine not fully to 72C, on a -40C day, above 3,500.... The Coolant Temperature will still correct, but the 'fixed map' will be pulling out fuel past peak torque anyway, proportionally.

 

Thinking further, on boosted old school applications, you would have hobbs pressure switches with resistors spliced  into the circuit to bias the Coolant Temperature Bias... 

 

You can add a LOT of fuel if that sensor is biased appropriately....enough to absolutely drown the engine in fuel and wet-foul the plugs! For a turbo, it was messy way to do it, but you stayed 'safe-rich' and tapered to ideal before going slightly rich again...and once past torque peak it was pulling fuel just like it should!

[Tony D]

And it's really CTS....coolant temperature sensor.

 

CHTS is on the later  vehicles in the US Market, and the CHTS is generally 20F higher than the CTS, which is why they used it: puts the computer into closed loop faster, for emissions. Plus, more accurate under full load...

[lowrider]

Like Tony said, It looks like a Hobbs switch controlled system that adds the dialed resistance from a Pot.

Back when I first turboed my 260 with the stock injection from a late ZX I had a Hobbs switch control a relay that had a Pot in series on the N/O leg. It worked, but it was incredibly crude. It kept the O2 controlled cruising/partial throttle fuel control the same as stock and when the Hobbs switch was active would dump the fuel to it. I had thoughts of constructing a staged system with multiple Hobbs switches and Pots for better more refined part throttle transitions while on boost but for the price of materials a megasquirt could be had that wasn't technology from the 60's/70's.

[NewZed]

You two are talking about what could be, and should be, but the HPSI guy says "one wire cut" for installation and RPM control.  Not pressure control.  Considering his monologue in the video, with technical jargon and terms like "muffler delete" (who says that?), you might be on the path he intended, thinking that it's more than what it really is.  It may look like a Hobbs switch control system, but it probably isn't.

 

And there's no Nissan literature that says the 280Z L-Jet system is fixed map above a certain RPM.  The ECU sees one coil fire at a time and adjusts accordingly.  No step changes, based on RPM level.  Maybe the 280ZX ECCS uses RPM levels, but this guy is advertising for all of the L-Jets.  One magic black box fits all.

 

The fact that he calls it a black box is warning enough.  He's basically saying if you buy this you deserve what you get, for not looking in to what it.is  Like buying Marvel "Mystery" Oil.

[lowrider]

At the end of the video above he states that the trigger point of the black box is adjustable. He makes no reference to RPM, he does however reference manifold vacuum which leads me to believe that the system is using a Hobbs switch. It seems as though the literature/ descriptions between the video and the ad have some discrepancies.

 

If it is in fact RPM controllable, I guarantee that more than one wire would have to be cut to provide the proper inputs/outputs to modify the fueling amount.

 

Either way, for a couple hundred more dollars you could purchase a stand-alone fuel management system versus a Band-Aid to a system that was designed in the 60's/70's.

[NewZed]

He refers to RPM in the eBay copy.  Warning signs everywhere.  

 

 

[NewZed]

He also says that nothing else is required except that one wire.  Not even finding a spot for the pressure switch.  Seems like that would be worth mentioning.

 

 

[lowrider]

I'm in total agreeance on the point that this product/ marketing has warning signs everywhere.

[Tony D]

I just saw the ebay link while on my laptop.

 

10 turn trimming potentiometer, hooked to a surplus counting dial (I bought three of those for my generator throttles at work from ORVAC for $9 each...)

 

Sounds like he has an rpm sensor box to act as rpm triggering, and then the shorting or incorporation of the variable resistor on the CTS line to the ECU.

 

That would give you a fixed variable enrichment triggered at a specific spot. Think about an MSD 6A RPM Trigger Switch coupled to put the trim pot in parallel or series with the CTS Sender Circuit.

 

Meh! Ships from Oklahoma, for $80 in shipping? SMFD!