2.3 TVS Designs

[Gr8snkbite]

Found the below info interesting as posted over on TS from a guy who sent his back to ford for testing and inspection b/c of unusual noise...wonder why the two designs, when it came to be, and how one would know which they have....


Blower tested by Ford Racing, noise levels are within spec. The interesting tidbit is that there are two different TVS blowers sold under the same part number, an "early" unit and revised "later" unit. The early units have a lower tooth count on the drive gears and a tighter tolerance/clearance between the screw vanes. The later units have almost twice the number of teeth and a looser spec for the vanes, the Ford tech stated that the earlier units are louder, but capable of creating more boost.......mine is an early unit....

[Joe G]

Interesting...



Sounds like a good research project for Danny and Birdy. :reading:

[Birdman]

Interesting info MC...how do you know your is the earlier unit if they both have the same part #?

[Gr8snkbite]

Thats my point George....ford techs indicate both have the same part number....so how would one know which they actually have....I've never heard of this and am curious.....it's interesting they increased gear teeth on the latter unit, and I am wondering why.....what caused the change.....maybe your insiders can elaborate.....:grin:

[Alloy Dave]

Thats my point George....ford techs indicate both have the same part number....so how would one know which they actually have....I've never heard of this and am curious.....it's interesting they increased gear teeth on the latter unit, and I am wondering why.....what caused the change.....maybe your insiders can elaborate.....:grin:Based on how we do similar things in our company, they may know based on production date of the unit. There are two types of changes we do on such things....one is called "rc" for "running change", meaning you can just start using the new one the first day it's available...in this case it's hard to tell the difference as you could have one of each used ON THE SAME DAY. But the other is called "USAG", for "use up and go", where you cannot even open the box on the new ones until the day after you complete using of the old ones....thus they will be stamped with a different production date even though the p/N is the same.

[Gr8snkbite]

Understood, but the TVS doesn't come with production dates on the packaging or paperwork..... least I've never seen it, or remember. But what I want to know more than production date of the two, is why there are two....why the additional teethon the gearing....to reduce boost for the consumer maybe.....dunno...

[Alloy Dave]

Understood, but the TVS doesn't come with production dates on the packaging or paperwork..... least I've never seen it, or remember. But what I want to know more than production date of the two, is why there are two....why the additional teethon the gearing....to reduce boost for the consumer maybe.....dunno...Well obviously I don't know the true reason, but I know we do it for all sorts of reasons. Cost, quality, reliability, etc. He mentions noise...perhaps that's the reason...to be quieter. Or maybe they changed the profile of the teeth on the gears to make them stronger. All I know is that most big production companies change things like that all the time. Sometimes the reason is something you'd care about, other times it's so mundane you can't believe it. I remember at a job I had as a Product Cost Manager in '99, we changed the design on a capscrew (bolt) to have one less thread on it because it saved 2 cents per capscrew. That might seem insignificant, but there were 34 of that capscrew on each engine, and we built 136,000 of those engines that year....it adds up.

[Joe G]

I remember at a job I had as a Product Cost Manager in '99, we changed the design on a capscrew (bolt) to have one less thread on it because it saved 2 cents per capscrew. That might seem insignificant, but there were 34 of that capscrew on each engine, and we built 136,000 of those engines that year....it adds up.Nice savings.

Everything is counted because it adds up quick.

[68fastback]

In the original Condor build manual (that I've heard some have seen -lol) the SC for 2008 models incorporated some running improvements but, as I recall, they are characterized as "add stiffeners and PIA" (which are proprietary agreement changes), so maybe that's what it is? And it did carry the same part number (tho a different control prefix and suffix, as I recall).

I'd also heard, but never saw documented, that a running change was made at the same time to tolerances (different gears affect tolerances since the rotors physically mesh) to take advantage of Eaton's ablative rotor coating (self-clearances based on actual operational tolerances). Maybe that's what he's talking about?

The part about the earlier ones making more boost sounds like pure male bovine poo to me :giggle: ...since tighter tolerances and more accurate gear/rotor indexing should be superior in every sense, imo. :yes: ...but who knows?

[edit:] Oooops, you're talking TVS, not the stocker ...I missed that. My comments above relate only to the stocker.

[Birdman]

Thats my point George....ford techs indicate both have the same part number....so how would one know which they actually have....I've never heard of this and am curious.....it's interesting they increased gear teeth on the latter unit, and I am wondering why.....what caused the change.....maybe your insiders can elaborate.....:grin:

I will try and find out but I'm thinking this type of info is probably known only by the folks at Eaton...

[68fastback]

Ooops. forgot in my post above you were tallking about the TVS (not the stocker).

That said, the TVS packaging and build is done by Roush. Eaton just provides the rotor-set, I think. So possibly it's Roush who might know what the specific differences are?

[breoland]

I think the difference between the original tvs to the newer tvs is where the egr bolts up to. I can be wrong about this but the 2 bolts that hold the egr in place, 1 is shorter than the other in the original tvs. the newer one uses the same two bolts from the stock eaton
For instance if you had an original tvs and took off your stock eaton and put the egr on the tvs, you would need to find a short bolt to make it work or the egr would not sit correctly and rattle around because a longer bolt will bottom out

[Birdman]

I think the difference between the original tvs to the newer tvs is where the egr bolts up to. I can be wrong about this but the 2 bolts that hold the egr in place, 1 is shorter than the other in the original tvs. the newer one uses the same two bolts from the stock eaton
For instance if you had an original tvs and took off your stock eaton and put the egr on the tvs, you would need to find a short bolt to make it work or the egr would not sit correctly and rattle around because a longer bolt will bottom out

This is true...:goodpost:...

[Gr8snkbite]

I will try and find out but I'm thinking this type of info is probably known only by the folks at Eaton...

:waiting:

[Birdman]

:waiting:

Noise reduction in gear drive

[Gr8snkbite]

how?

[Birdman]

how?

Have no idea didn't get detailed info on that.

[68fastback]

...also more teeth permit tighter tolerances in gear mesh and reduced variation/pulsing in the angular velocity or the two rotors relative to one another ...and that permits tighter rotor-rotor tolerances and better effeciencies, so that could be part of it too.

[Birdman]

...also more teeth permit tighter tolerances in gear mesh and reduced variation/pulsing in the angular velocity or the two rotors relative to one another ...and that permits tighter rotor-rotor tolerances and better effeciencies, so that could be part of it too.

I believe the teeth angle was changed to reduce noise but it also weakened the gear so they added some teeth to keep the strength the same.

[68fastback]

I believe the teeth angle was changed to reduce noise but it also weakened the gear so they added some teeth to keep the strength the same.

Thanks, George -- that makes sense re noise :tiphat2: ...the weakening is likely beacuse of the 'twisting' load that angled gears inherently add, which can be substantial. I wonder if they just added more smaller teeth or more same-size teeth (larger diameter gears) or also widened the teeth to spread loading ...or some combination of all three within the packaging constraints.

---

Interesting that the Cucamonga gang went in the opposite direction on the plumbed SCs: to straight-cut teeth, as I reacall, because the offset loading of angled teeth was both impacting bearing sideloading and rotor end-seal/tolerances (based on their stated benefits of the revised design) as well as distorting/flexing the rotor shafts at high gear loads (which I found astonishing at first but don't doubt tey measured it somehow). There's definately a tradeoff: more teeth and angled teeth tend to be smoother (less pulsing and, therefore, less noise) but angled creates both more bearing load (both conventional from 'twist' and end-load from 'push') .

I'm surprised the NVH aspects on the 2013 were prioritized high enough to justify the tradeoffs and need to compensate for them ...it's not like these SCs are completely quiet anyway and that's sort of part of the character of an FD SC. The again, the TVS' two rotors spin at 1:1 speed so the bearings are *far* less stressed than on twin-screws (at identical pulley rpm) which typicall sport driven-rotor ratios of 4:6 (KB) or 3:5 (Whipple) ...another inherent benefit of the roots deisgn -- even on a high-twist TVS variant.

I noticed in the 5.0M&FF article that they mention (and it's implied Ford told them) that the '13's TVS eats about 100HP at full bore. While that number seems low (a good thing), I believe I recall a particular vendor who tested a particular popular twin-screw at similar boost levels at found it consumed *way* over that ..and the way they tested that was (same/day/dyno/car/boost), puled the twin-screw and put on the TVS and immediately saw the increase at the rollers. Different subject but straight cut gears, while rougher/noisier, also carry less parasitic loss but clearly (imo) only a tiny fraction of the difference observed.

Anyhow, I don't anticipate any noticeable loss of effciency in angled gears on the TVS and, if so, then the observed differences by that vendor must be inherent to the TVS design itself ....which it seemed clear was the reason anyway.

Just tossing these thoughts out in case its of interest to anyone.

[Birdman]

We're talking a minute amount of pitch change.

[68fastback]

We're talking a minute amount of pitch change.

Ah! Outstanding!! That's great to hear, George, and what I was hoping but had no way to know. Probably just enough pitch to sufficiently overlap tooth 'ramps' across the width of the gear to reduce pulsing/noise, and still have very little axial 'push' on the bearings. Likely some good modelling work was done. Since the TVS rotorset uses an ablative coating (I assume it still does) it will self-select minimum operational clearances but that can only work as effectively as stable design dynamics permit.