Explain how Hilborn fuel inj regulates?

Never drove one but the Chevy Rochester FI seemed to work OK. people sure pay enough for them now. I am surprised someone hasn't made a fake Rochester with EFI internals.

 

That's why Hilborn uses a Map Sensor and Air Temp Sensor to adust for Al***ude/Air density-

 

I use a Dial-A-Jet in conjunction with a set of curves/tables for atmospheric pressure, temperature and relative humidity....on the fly changes are quite easy with the right set up.

 

I use an on-board exhaust gas ****yzer to tweak the mixture, along with the Dial-A-Jet.

 

They were mechanically injected. How is it different?

 

The Bosch K Jetronic, as used by Audi, VW, etc. used an air door with a metering rod to adjust fuel to the volume of incoming air; NOT just throttle position. The Hilborn style with ITBs has no provision for airflow measurement. A vacuum fuel pressure regulator would be a distant second, but again, there is no common vacuum chamber. Bottom line, it just wasn't designed to work well under "normal" driving conditions...

 

That's what I was trying to say a few post back. But, apparently it was "BS". I guess I don't know what the **** I'm talking about.

 

Great picture! A friend of mine noticed better drivabilty, once he went to using a magneto. Burned hotter, I think he said. I'm pig headed, an am dead set on trying to use it on the street.

 

The Bosch K Jetronic was as stated above and it was the first of Bosch's systems to employ a constant fuel flow to the injectors. The "K" derived from the German word for constant.

The immediate predecessor was the L Jetronic which had pulsed or timed injectors and measured air flow. The "L" derived from the German word "luft" meaning air.

The earliest production system was the D Jetronic which also had pulsed injectors but measured pressure (or vacuum as mentioned by exwestracer). The "D" derived from the German word meaning pressure.

I believe all three of these systems also included a computer brain box.

I also believe the original Bosch systems were further developments of the Bendix system of the mid fifties which may have been purchased by Bosch

 

Dean, you know exactly what you are talking about.

Perhaps the HAMB er that called BS on my post #18 and your quote should provide some specifics.

 

Now that's funny!
IIRC, the K Jetronic had a version that did NOT use a computer. They did all have electric pumps as I recall.

 

I bought this Hilborn 2 holer from Rocky Childs in '64. God damn, did I try hard all summer to get it to run on the street! Maybe, if I would have known what the expert that called "BS" knows, I wouldn't have wasted the summer of '64 screwing with it, and actually got it driveable.

 

Simple. You don't know what the **** you're talking about.... HAHAHAHAhahaha.

Seriously Dean, it is great to have you weighing in on this stuff that a LOT of us are a generation behind on. I always look forward to your "been there, done that" posts.

 

Let's keep this going... I'm learning alot. Just amazing the knowledge out there.

 

Hotrodart mentioned a "dial a jet" earlier. This is also commonly referred to as a "pill selector". If you refer back to the Hilborn schematic in post 21, the dial-a-jet goes inline on the return side of the "main byp*** valve". While it won't really make the injector compensate for load or air conditions, it DOES make street driving a lot more friendly. The driver can now adjust the overall fuel mixture by simply turning a knob. Most racers don't run them because they don't need to.

 

And it's something for the driver to think about. As the car owner/tuner, you really don't want the driver thinking.

 

"like!"

 

I have a solid/blank pill in my barrel valve, with a kinsler Q/C pill holder in the return line. The 'dial a jet' might be in my future, once I start running it on the street.

Using a 80A O pump putting out 2/gal min @ 2000 rpm- 3.8 @ 4000
for a 408 SBC

 

I run the secondary and high speed directly out of the barrel valve chamber, not off the pump. I've found the motor picks up MUCH better coming off the corner with it that way. I don't run my supermod on the street, but I could see that setup helping keep the motor cleaned out for off-and-on throttle conditions as well.

 

Maybe this will put this thread to bed and silence those saying BS to those of us that are trying to provide accurate and meaningful information to those that ask and will listen.


<TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD vAlign=top></TD><TD><TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD><TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD vAlign=bottom></TD><TD vAlign=bottom align=right></TD></TR></TBODY></TABLE></TD></TR><TR><TD><TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD vAlign=top width="100%"><TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD vAlign=top align=left bgColor=#000000></TD></TR><TR><TD vAlign=bottom bgColor=#ff0000><TABLE cellSpacing=0 cellPadding=0 border=0><TBODY><TR><TD vAlign=top></TD><TD vAlign=bottom></TD><TD vAlign=bottom></TD><TD vAlign=bottom></TD><TD vAlign=bottom></TD><TD vAlign=bottom></TD><TD vAlign=bottom></TD></TR></TBODY></TABLE></TD></TR><TR><TD vAlign=bottom bgColor=#000000></TD></TR></TBODY></TABLE></TD><TD align=right width=134 rowSpan=3></TD></TR></TBODY></TABLE><TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD vAlign=top align=left width="66%"><TABLE cellSpacing=0 cellPadding=0 width="90%" border=0><TBODY><TR><TD vAlign=top align=left>[FONT=arial,geneva][FONT=arial,geneva]Technical Support - Mechanical - Fuel Injector Manifolds [/FONT]
Return to Technical Support
[/FONT]
[FONT=arial,geneva][FONT=arial,geneva]Can I run a HILBORN mechanical fuel injector on a street car?[/FONT][/FONT] <TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD vAlign=top align=left bgColor=#ff0000></TD></TR></TBODY></TABLE>[FONT=arial,geneva]A Hilborn mechanical injector is cl***ified as a constant flow system and was designed to operate at WOT under load. As a constant flow system, pressure and volume are controlled by the main jet, or pill, along with pump speed (engine rpm) and nozzle size. The barrel valve, which controls idle fuel and transitional fuel from idle to WOT, can be compared to a ball valve much like the one that turns off the water in your house. The basic design and lack of fuel control of a barrel valve does not allow us to control the fuel at part throttle especially no load part throttle. If you consider the fact that an engine's fuel requirements are based directly on load, and that we can have many different loads at different rpms all at the same throttle angle, the lack of fuel control for street applications becomes apparent. A mechanical system does not employ enough fuel control in the operating range where you drive your street car and, therefore, is not recommended for street use.[/FONT]
[FONT=arial,geneva]Of course we have all heard the stories of mechanical system working on the street but few if any actually worked correctly. The use of a dial-a-jet, additional byp*** valves, and home center ball valves have all been used to provide fuel control for adequate street use, but fall far short of the fuel control required as part throttle load is constantly changing. The constant manual adjustments needed, as one guesses the current fuel requirements of the engine, leaves very little time to actually drive the car and, at best, is incredibly inaccurate. Blown applications appear not to be as affected by the lack of fuel control of mechanical injection, possibly due to the load placed on the engine to drive the blower, but is still not recommended for those looking for the best all around drivability.[/FONT]
[FONT=arial,geneva]The use of alcohol helps because of it's large tune-up window, but fails to provide drivability due to loading up, mileage (in gallons to the mile) and severe oil dilution. Claims from those that run injected engines on stands or dyno's stating they can make mechanical injection streetable, are unable to simulate a fraction of the different part throttle load scenarios your engine will see, nor provide the required fuel control. Interestingly enough, engineers have devised a way to electrically control these valves and byp***es...it's called electronic fuel injection.[/FONT]
</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>

 

I have found that conditions in my area are quite stable for a daily cruise......I tweak the Dial-A-Jet before a trip and watch the wide band exhaust ****yzer. The car has made 3 round trips of 1100 miles each without a fault....might need another tweak at infrequent intervals. When the car is at highway speeds not much changes. Around town it really makes little difference. Initial set up takes a few minutes with the curves and tables I have. The three by-p*** springs and pills are quite critical though.

 

Ditto on the secondary and high speed by-p***es.......I took a lesson from you roundy-round guys.

 

I totally agree that a Hilborn out of the box will not work on the street......as I have said several times. I have made several design changes to the Hilborn and fabricated several parts that Hilborn does not supply.....it's not "your father's" Hilborn.....but it's still a mechanical stack injection......isn't that what hot rodding is all about???

 

Yes.

 

The first line on that Hilborn tech support page sounds familiar. Where have I seen that before??

 

For the unfortunate ones that didn't get to see this car on the road you missed out on something very special. It hauled the mail with beauty. Too get that car to run low 11's with a small block ( 283-301?) was very impressive. Guess someone knew how the Hillborns worked.....

 

Wow. This thread got some neat replies. For a 37 year old, I sure do appreciate the old school knowledge. Thanks guys!!!

 

I run my RP on the street every day with my electronic setup. This mapping is really very similar to a full mechanical setup, as there's no load sensing, just RPM and throttle position sensing(alpha n tuning), along with cold start enrichening, and air temp compensation. I have to run it a little rich in the part throttle/light load so that it has enough fuel under heavier load conditions. Overall it works very well, and makes WAY more power than the single four barrel carburetor I took off.

Now, I think if I were to do a mechanical set up with what I've learned setting up the electronic, I'd use an electric high pressure fuel pump and adjustable F/P regulator. That way you get constant fuel pressure without the rise as RPM's increase. That should eliminate the need for the high speed byp*** circuit, simplifying tuning.

 

The car I helped with at Bonneville had leaning troubles. The owner machined a blank pill. That mean all the fuel the pump could pump had to go through the engine. It was a 498 Chev. Dead slow idle was about 1900 to 2100 RPMs, making some black smoke. He would wing it to about six grand, drop the hammer at about 25 MPH and it cleaned out right away. If that's how you drive your street car, go for it! The electronic conversions look like a good deal to me.

 

i wouldn't call me an expert. But I think if I was running a blank pill, I would get a bigger pump. Seems like it would be hard to tune with no return.