I have some questions on mech. FUEL INJECTION is there any
relationship to high speed lean out and the forward faceing hat stuffing air
into the blower at 200+ mph. I guess you should know the answer to that
question if it becomes more of a problem or only shows up on the track and
not in the dyno room??? Has anyone used the conventional Hilborn type
injection on thier blower to do say 90% of the fuel requirement and make up
the remaining 10% with electronic down injectors that is regulated wih
O2 and EGT sensors. Seems like you woouldn't need those expensive high flow
electronic injectors and they could cycle better. Kvach
----- Original Message -----
From: <ardunbill@webtv.net>
To: <land-speed@autox.team.net>
Sent: Tuesday, February 08, 2000 11:45 AM
Subject: Tuning Mechanical Fuel Injection
> Group, in looking more closely at the "Hemi Head Chevy Engine" article I
> told you about earlier today, there is an illuminating technical tidbit
> expressed for those like myself trying to get mechanical fuel injection
> working properly.
>
> That's a sidebar in the article entitled "Iskenderian Dyno Report". The
> chart under it reads in part as follows:
>
> RPM HP TORQUE BOOST BYPASS(jet)
>
> 5500 539 490 16# .105
> 6000 578 482 17# .105
> 6000 514 462 17# .090
> 6000 590 492 17# .110
> 6500 624 480 17# .110
> 7200 638 440 19# .110
>
> All the above involves this hemi-head 301 Chev running on alcohol with a
> 6-71 blower driven 1-1 with a Hilborn injector on top of it. With the
> Hilborn bypass jet system, a smaller (numerical) jet size means a richer
> mixture.
>
> Several interesting things here:
>
> l. The engine needed different bypass jet sizes to give max power at
> different RPM ranges. Something about the cam timing, etc., was letting
> more or less fuel escape out the exhaust at different rpms. Assuming the
> Hilborn pump delivers a constant increase in flow directly proportional
> to increase in rpm(does it?).
>
> 2. When running mechanical fuel injection, you can only run one bypass
> jet during a pass on a speed trials course (despite availability of 'jet
> selectors' etc., no time to turn 'em). One bypass jet size is not going
> to give you full power at all rpm ranges, blown or unblown, so you will
> have to focus on the top end and hope it doesn't hurt the mid-range too
> much.
>
> 3. The blower's manifold pressure increased at the top end because the
> gas-flow through the heads could not keep up with the increased output
> of the blower. At 7200, even though the manifold pressure went up to
> 19, the engine torque was dropping down sharply.
>
> The spark lead was 34 for all the above tests on this hemi-Chevy. The
> heads had the plug electrodes at the combustion chamber surface(no
> cartridge fire setup like the original Arduns).
>
> Any comment from veterans with mechanical fuel injection experience??
> ArdunBill
>
>
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