Dynoing A 7.3L Godzilla Engine With No Throttle Body Or Manifold

Dynoing A 7.3L Godzilla Engine With No Throttle Body Or Manifold

If you’ve spent any amount of time around an engine dyno, chances are you’ve had a crazy idea or three. Well, when it comes to crazy ideas, our buddy Ben Strader of EFI University has a way of making them work and then not seem insane at all. Enter his latest willingness to risk equipment and parts all in the name of learning — dynoing an engine with no throttle body or intake manifold.

“A lot of time in my classes, I like to talk about what the job of the throttle plate is. The reality is, the job of the throttle plate is to limit power,” explains Strader. “You normally make your dyno pulls at wide-open throttle, so what if you just didn’t have a throttle body? So… we took it off.”

If you haven’t spent time around an engine dyno before, this might seem a little confusing, so a quick, super-simplified explanation is in order. When you run an engine on the dyno, the dyno itself is controlling the engine’s speed at wide-open throttle. It can hold the wide-open engine at a given RPM, or allow a set acceleration rate for testing.

So, in theory, an engine with no throttle body should behave just like an engine that was already cracked wide open. The question was, could the dyno react quickly enough to prevent an engine runaway? Strader wanted to find out. But not just without a throttle body — without the whole upper half of the intake manifold.

In order to film down the throat of the intake manifold, you obviously need light. However, for a high-speed camera, you need a ton of light. Strader was recording at almost 7,600 frames per second. For scale, the average YouTube video is played back at 30 frames per second. That means for every second of high-speed video recorded, you get 4 minutes and 13 seconds of playback.

“We set the dyno, started it up, and it caught it,” says Strader of the successful initial run. “So then I had the thought, ‘if it can do that, what else can we do?’ We got this wild idea that we wanted to see what was going on inside the engine. What is unique about the Godzilla, is that the fuel injectors are cast into the cylinder head.” I’m sure you can see where this is going.

Since the injector isn’t positioned in the manifold’s runner, like typical port fuel injection, you don’t technically need the manifold for the engine to run. That led Strader to decide to try and run the engine without any intake manifold at all. This would allow his high-speed camera to film the injector and valve motion without any impediments whatsoever. The footage garnered from that is absolutely fascinating.

“At 6500 rpm, the intake valve is opening and closing 54 times per second. We are able to record almost 7,600 frames per second, so you can see every movement of the valve opening and closing, as well as the fuel movement,” Strader explains. At that speed, you can see the pressure waves moving the fuel (both in droplet and vapor form) around the valve as it opens and closes.

While this all might seem like some after-hours hijinks, Strader assures us this is all valid research and development work, that happens to come off as “hold my beer and watch this” (until you scour over the information garnered from it, anyway). After all, one of Straders most awesome engine projects — Spinal Tap — started off with a “what if” and a few calculations scribbled on napkins. And we all know how that turned out.

While this still image doesn’t do the high-speed video any justice, it is absolutely awesome that we are able to look at what’s happening at the valve in extreme slow-motion. The amount of information gleaned from this kind of experiment might not seem substantial, but it really is.

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About the author

Greg Acosta

Greg has spent eighteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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