i guess you enjoy a cool climate 
. keep us updated
. keep us updated
The Underdrive Pulley Project
I just started a new project which consists in removing the AC compressor and replacing the heavy stock harmonic balancer / crankshaft pulley with a lighter chromoly pulley that was developed by TTV Racing for a Duratec project with Ford. I trust it’s light but not too light as some alloy pulleys might be.
The pulley has a single 6-groove race and drives the accessory belt approx. 20% slower than stock, so the alternator and water pump will rotate that much slower and induce less drag / less power losses, and less rotational inertia. The crank pulley alone is about 1.4kg (3lbs) lighter than stock.
I have to convert the entire serpentine path to the new 6-groove belt which means new idler pulley, new tensioner pulley, and new alternator pulley. Curiously, the water pump already has a wide pulley but I’m replacing it with a light alloy version.
The AC compressor is a heavy beast and the stock crank pulley is quite heavy too, so together with the condenser and some piping there will be a gain of at least 15kg or so, including approx 2kg of rotating masses between the lighter crank pulley and a new light water pump pulley as well as the removal the AC pulley and its belt. That’s significant as far as inertia, as the crank pulley obviously rotates at engine speed while the water pump and AC pulleys rotate even faster. There is also a general theory about cavitation in water pumps which may or may not be an issue on the EcoBoost, but slowing down the pump gives some headroom for more RPMs.
Together with the reduction of rotating masses, the underdriving also free up some actual ponies. So it’s free horsepower and less engine inertia, to accelerate the car harder, and a bit less “regular” weight too, by removing some of the AC components. The main drawback is less comfort during hot days.
I’ll post the part list once the conversion is sorted out.
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Yes I agree that's a step closer to frankensteinisationi guess you enjoy a cool climate
I live in moderate climate and I use the AC maybe five days a year, and carry the weight the other 360. The good thing is it's easy to undo.
Did you actually finish this project? If so, how did it turn out?
Yes I agree that's a step closer to frankensteinisation
I live in moderate climate and I use the AC maybe five days a year, and carry the weight the other 360. The good thing is it's easy to undo.
I sure will. What I did not mention on this thread is a moved away from the 6 rib belt and designed a lightweight 4 rib pulley that uses the stock belt.
I figured that would be much easier than change everything on the belt path: although I have the hardware on the picture the tensioner and idler pulley must somehow be adapted, and the clutched pulley on the alternator changed.
The final 4 rib pulley has 20% under drive and all is needed is a shorter belt, which is easy to find.
This is one of the intermediate designs I made for normal drive / stock belt. I got quotes all over the place from $300 to $3000 for the prototype.
True You can still keep the AC piping in place and store the removed parts for that elusive sale in 15 years.
It would not be too difficult to design a lightweight pulley to also underdrives the A/C but again a tiny batch would be expensive, and I’m not sure there is enough demand to risk making a larger batch to drive the cost down, and there are two product variants already.
That’s the dilemma of the small makers right there: you cannot drive cost down without volume and volume implies high upfront costs and risks. Many small fabs make one tiny initial batch sold with thin margins and wait until there is enough back orders to justify a second batch = perpetually out of stock.
You can still keep the AC piping in place and store the removed parts for that elusive sale in 15 years.It would not be too difficult to design a lightweight pulley to also underdrives the A/C but again a tiny batch would be expensive, and I’m not sure there is enough demand to risk making a larger batch to drive the cost down, and there are two product variants already.
That’s the dilemma of the small makers right there: you cannot drive cost down without volume and volume implies high upfront costs and risks. Many small fabs make one tiny initial batch sold with thin margins and wait until there is enough back orders to justify a second batch = perpetually out of stock.
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