@Si2RS , I think you must drive with your seat reclined more than mine. I'm also 6'2", have the seat fully lowered (as much as a stock seat, anyways) and my helmet rubs a little on the ceiling panel. I'm glad we had options for the sunroof then, so we could get what we prefer! I wonder why Canada didn't get that option.
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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I am waiting for a quote from the manufacturer to cut two prototypes based on the above model. The finish will be zinc (electroplated) so yellow-gold-ish, and without the lettering which is cosmetic on the above rendering.
I've drawn all the pulleys on the belt path with the new underdrive pulley and the new calculated (theoretical) effective belt path length is 1310.88mm.
By chance, a 1311mm 4-rib V-Belt readily exists, the Gates K040517RPM 1311mm eff. / 1325mm ext. 4 ribs 14.3mm (9/16") 51.6" eff. / 52.125" ext. and can be ordered from any auto retailer.
Worst case I have to redo the water pump pulley (a simple design) to adjust for the belt length if necessary, I'll have to try on the car to figure that out.
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I've drawn all the pulleys on the belt path with the new underdrive pulley and the new calculated (theoretical) effective belt path length is 1310.88mm.
By chance, a 1311mm 4-rib V-Belt readily exists, the Gates K040517RPM 1311mm eff. / 1325mm ext. 4 ribs 14.3mm (9/16") 51.6" eff. / 52.125" ext. and can be ordered from any auto retailer.
Worst case I have to redo the water pump pulley (a simple design) to adjust for the belt length if necessary, I'll have to try on the car to figure that out.
The prototypes (as above) are ordered, it will take 3-4 weeks to make them and probably another week to ship.
In the meantime, I designed a variant with the A/C drive (also 20% underdrive) and I am wondering if I should start thinking about making the pulleys available as a product.
Some points:
I don't know the final price yet. Mountune sells a Duratec 36-1 pulley for $279, that seem to be massively under revving for fast N/A engines. I won't be able to match that price as my batch will be very small. If I ever sell these, it will probably be as a kit all sorted-out, with the big ARP 251-2501 bolt, the diamond washer, a 3mm key, and the shorter v-belt(s) included.
What do you guys think? Yay, nay? Dunno?
PFA (the future pulley with A/C drive that I just made tonight, for those who don't want to delete the A/C)
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In the meantime, I designed a variant with the A/C drive (also 20% underdrive) and I am wondering if I should start thinking about making the pulleys available as a product.
Some points:
- The stock cast-iron pulley weights 2460g (5.42lbs) and is in two parts. It tends to rust badly and some people have shown that the crank trigger ring sometimes gets some play and throws the timing off. Here’s a link. I'm not sure how often it happens, though.
- My A/C Delete underdrive pulley weights approx. 687g (1.51lbs) and the A/C Drive version weights approx. 975g (2.15lbs) both for lower rotational inertia which helps acceleration in short gears, and a little weight saving on the whole car, which also helps a tiny bit. The A/C delete pulley saves approx. 1770g (3.9lbs) which is far more effective at the crank than anywhere else on the car (say a corresponding weight saving on the rims or the brake rotors) as the rotation speed of the crank is much higher.
- They are keyed for a 3mm key (for keyed crankshafts from Callies, also sold by Mountune and Panda Motorworks, or the stock keyed crankshaft sold by Massive Speed Systems) - They will work with a standard crankshaft provided a Ford "diamond washer" is used.
- They reduce the speed of the accessories by 20% (alternator, water pump, A/C compressor) to reduce parasitic losses and free some ponies at high RPM. How many is anyone's guess, but there will be close to 20% less than whatever those losses are.
- They are cut in one piece (CNC-machined) and made of chrome-moly steel (41xx), a motorsport tradition. The finish for the prototypes will be zinc-yellow but if I make a batch, they will be finished in Black Oxide and look similar to the pic below.
I don't know the final price yet. Mountune sells a Duratec 36-1 pulley for $279, that seem to be massively under revving for fast N/A engines. I won't be able to match that price as my batch will be very small. If I ever sell these, it will probably be as a kit all sorted-out, with the big ARP 251-2501 bolt, the diamond washer, a 3mm key, and the shorter v-belt(s) included.
What do you guys think? Yay, nay? Dunno?
PFA (the future pulley with A/C drive that I just made tonight, for those who don't want to delete the A/C)
These are lightweight water pump pulleys. The stock one weights 356g and this weight can be reduced to 179g (half) in 1.5mm thick 4130 steel or 86g (about a quarter) in 2mm thick 7075 aluminum. This is more of an exercise this time as I'm not sure it's cost-effective to manufacture these.
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The pulleys are delayed 3 weeks 😕 I got the shorter v-belt as consolation prize.
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Finally, the pulleys arrived today. Pure work of (motorsport) art 😎
This is the lightweight, 20% under drive, A/C delete, 3mm keyed version.
Zinc-plated, monobloc, chrome-moly steel alloy, and 684g (1.5lb) is the final weight.
Note that the 3D model estimated weight was 687g (1.51lb) so only 3g (0.1oz) off, within one half percent of the real thing, well within manufacturing tolerances.
The belt fits perfectly in the race, and everything is perfectly aligned with the stock pulley. That seems obvious but other pulleys out there didn’t embarrass themselves with such details.
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This is the lightweight, 20% under drive, A/C delete, 3mm keyed version.
Zinc-plated, monobloc, chrome-moly steel alloy, and 684g (1.5lb) is the final weight.
Note that the 3D model estimated weight was 687g (1.51lb) so only 3g (0.1oz) off, within one half percent of the real thing, well within manufacturing tolerances.
The belt fits perfectly in the race, and everything is perfectly aligned with the stock pulley. That seems obvious but other pulleys out there didn’t embarrass themselves with such details.
The zero-crossing point that the PCM detects is the exact center of the teeth and is not affected by « rounded or square » provided the teeth are symmetrical. Mine are certainly no less symmetrical than the OE trigger.
The only reason why the OE trigger is rounded is because it’s a cheap stamped metal part. It’s an artefact of the fabrication process, not a design feature.
The thing that really matters as far as trigger wheels is there is no jitter i.e. no angular error between teeth so the TPU don’t register imaginary variations in angular velocity. My pulley’s teeth are spaced 6.000° as accurately as the CNC machining allows, and there will be no more jitter than the OE stamped metal one.
It took a long, long time but my new pulley is finally on the car.
The fit and alignment are perfect, the center hole slightly snug fit, length, the key, the belt alignment with the alternator, perfect.
The belt I calculated also fits. It’s a bit difficult to install it. I wish there was a length just 10mm longer, but it’s not a real problem.
I am doing the clutch at the same time so I was able to lock the crankshaft from the flywheel side. Otherwise I’d recommend removing the starter motor and using a “jaw” flywheel locker, that bolts into the starter holes, from that window.
I’d never rely on the timing index to undo the pulley bolt and to tighten it to 190Nm.
After removing the fender lining, the pulley is right there. With the right puller it was easy to remove the stock pulley.
I designed the pulley to fit the ARP 251-2501 bolt. It looks like it protrudes a lot but it’s because the pulley has only one belt race: it’s the A/C delete version.
I like the zinc plating finish. If I produce these (maybe this summer) I may switch to black oxide that looks a little more OEM.
I have designed an A/C version but I’m not sure which belt would fit for the A/C. Both belts need to be shorter than stock because 20% underdrive.
Remember that with keyed crankshafts there is not much timing slip to worry about when installing, or when running the engine. The key is at TDC. Just align the center of the crankshaft sensor to the center of tooth #20 when the engine is at TDC, as per Ford instructions, and it’s done.
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The fit and alignment are perfect, the center hole slightly snug fit, length, the key, the belt alignment with the alternator, perfect.
The belt I calculated also fits. It’s a bit difficult to install it. I wish there was a length just 10mm longer, but it’s not a real problem.
I am doing the clutch at the same time so I was able to lock the crankshaft from the flywheel side. Otherwise I’d recommend removing the starter motor and using a “jaw” flywheel locker, that bolts into the starter holes, from that window.
I’d never rely on the timing index to undo the pulley bolt and to tighten it to 190Nm.
After removing the fender lining, the pulley is right there. With the right puller it was easy to remove the stock pulley.
I designed the pulley to fit the ARP 251-2501 bolt. It looks like it protrudes a lot but it’s because the pulley has only one belt race: it’s the A/C delete version.
I like the zinc plating finish. If I produce these (maybe this summer) I may switch to black oxide that looks a little more OEM.
I have designed an A/C version but I’m not sure which belt would fit for the A/C. Both belts need to be shorter than stock because 20% underdrive.
Remember that with keyed crankshafts there is not much timing slip to worry about when installing, or when running the engine. The key is at TDC. Just align the center of the crankshaft sensor to the center of tooth #20 when the engine is at TDC, as per Ford instructions, and it’s done.
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