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 Post subject: Jenvey - Fuel injection throttle bodies
PostPosted: Thu Feb 09, 2017 8:20 am 
0-60 in VERY FAST

Joined: Tue Aug 13, 2013 1:14 pm
Posts: 161
Location: Regina, SK
I have seen these in Practical Classics magazine, and in Classic Motorsports magazine as well, I thought they looked pretty cool. They are injection throttle bodies that resemble the Weber DCOE carbs. I don't know the full spec or management system (MS3Pro, perhaps)? but I wanted to toss it on here so more could have a look. According to PC magazine, apparently Jenvey is looking at creating a SU-type Heritage injection body. The nice part, I assume is to use a readily available Weber-type intake manifold to easily adapt the throttle body (or bodies) to fit the engine without too much hassle.

UK site - https://www.jenvey.co.uk/products2/twin ... 48mm-tdsxx
US site - https://foxinjection.com/collections/dc ... tle-bodies

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1967 Volvo 131 B18D M41


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 Post subject: Re: Jenvey - Fuel injection throttle bodies
PostPosted: Thu Feb 09, 2017 10:19 am 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Dec 21, 2005 8:40 pm
Posts: 3366
Location: Calgary, Ab
Whoa, those are spendy but the hidden injector factor is interesting. Anyone would be able to spot them pretty easily, and there are other throttle bodies that use the Weber manifolds so you'd really have to want to fool people at a passing glance to buy these over them.

The issue with using SU throttle bodies as injectors is that TYPICALLY an SU is installed on a manifold that pairs two or more cylinders together. Usually those cylinders are not spaced evenly in the firing order. For instance, in our cars the front carb delivers fuel for 2 & 1, then waits for 3 & 4, then delivers, then waits... If you were to try to use a single (or a pair) of fuel injectors in an application like this, sequencing the injectors with the intake valves is CRITICAL.

Configuring a conventional Megasquirt to control these injectors is impossible. If you ran batch fire 1 squirt per cycle, practically all of the fuel would be consumed by cylinder #2 because that intake opens before #1, unless the injector happened to fire when #1 was open in which case most of it would go to #1. There is a small amount of physical separation between intake ports so SOME fuel would go to the lean cylinder, but not a lot. If you ran more squirts per cycle in batch fire mode (like 4) you'd have a similar issue except that it would be more predictably lean on #1 (or more predictably rich on #2).

If you switched to alternating mode and 4 squirts per cycle, or batch mode and 2 squirts per cycle, things get complicated. Either you'll squirt when #1 intake is open and then again on #2 compression (and the cylinders will be relatively but not exactly balanced), or you'll squirt when #1 is on compression and again when #2 intake is open, in which case #2 will consume 100% of the fuel. Either the engine will run half assedly on 4, or will flood 2 cylinders and not have enough fuel to run on the other two.

Setup of the injection advance becomes very critical and can only be done properly with many hours on a rolling road, I don't care what anyone says to the contrary. On a single carb, or on something like a twin carb inline 6, each carb is called upon in even pulses and injector phasing issues goes away and you can use the less expensive Megasquirts that have no phasing control. On our engines, you've got to use a fuel injection system that references cam timing and has FULL control over each injector driver with regard to pulsewidth and timing, and you will be spending many more dollars getting it set up right. A wideband would also be of marginal help here - you'd really want to suppliment the datalogging with individual exhaust gas temp streams, which obviously adds complexity and cost.

That all makes $550 USD Weber-style TBI units pretty cheap and easy to run.


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