1 (edited by darkostoj 2021-01-27 10:51 AM)

Topic: The great throttle body size debate

So, for the past forever I have seen larger throttle bodies sold for cars in the aftermarket and a bunch of unsuspecting Jabroni's buying these in hoardes and patting themselves on the back for it.

So, does anybody actually know when/why we should change throttle body size? Nobody ever talks about it.

For example this is my particular situation:

I am converting the engine in the rolls to a DBW throttle body and I have many options to pick from.  The stock throttle body is oval shaped with 2x65mm blades. The total bore area is 6636mm squared. 

If I go to a single blade throttle body, here is an example of the total bore area of different sizes

108mm - 9160mm
102mm 8171mm
100mm - 7853mm
92mm - 6647mm
90mm 6361mm

So it looks like to retain the same Throttle body opening I need to shoot for the 92mm size.

Now would be a good time to either go up or down...but how the heck do you figure that out?

Where the smart guys at???

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Re: The great throttle body size debate

IMHO, this is one of those areas where you'd need specific Viper V10 knowledge to answer that question.  I'd look for back/back dyno comparisons for that engine.  There's no universal answer to that like there is for other mods.  I do know there are some engines where a larger TB is counterproductive.  If there is restriction downstream that prevents more CFM than the 92mm body allows then you have wasted money and probably intake velocity.  OTOH, it's possible that the 90mm TB gains you more torque at the RPM you need it.

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Re: The great throttle body size debate

Bigger TB for the most part only help power at the top end and may hurt power in the low end
. Over the years of reading about dyno tests of various engine mods the one item that didn't do much was a larger TB.
Now if your change your camshaft/s, port the head, open up the exhaust, etc. then at some point a stock TB will become the main restriction and at that point you would go bigger.

Re: The great throttle body size debate

For the V10 I'd go with an 850HP lol

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Re: The great throttle body size debate

Bigger throttle body is less restrictive, so may increase power.  Downside is drive ability at part throttle. Will be more sensitive to pedal position.

Re: The great throttle body size debate

Math checks out, 92mm sounds good, though you'll have to fabricate an adapter to go from oval to round, as you know. I don't know how you're controlling the DBW, but within reason you should be able to calibrate decent drivability, at least a lot easier than cutting new cams for a cable throttle.

You can measure differential pressure across the throttle on a WOT run to see if a larger throttle may help, or if the Viper engine has a MAP sensor you can log it from OBD2. If you measure MAP and compare with barometric pressure keep in mind this will include intake tubing and air filter restriction, not just the throttle.