Roush TVS 105mm to 85mm blower pulley swap, how much boost?

[golkhl]

Thinking of swapping the stock 105mm blower pulley on my TVS and installing an 85mm, any ideas on boost psi increase? Car currently makes 5-6 psi with 105mm pulley. Thank you.

 

[07 Boss]

I would venture a guess at 10-11 psi.

 

[DiMora]

First, calculate a drive ratio.

Example: 6" crank damper pulley and 3" supercharger snout pulley = 6 divided by 3 = 2:1 IE the supercharger snout pulley spins 2 revolutions for every one revolution of the crank. So...and an engine RPM of 6,000, the supercharger is doing 12,000 RPM. That's just to explain the process.

Here are some numbers from my files:

DAMPERS:

Stock GT crank damper = 169MM or 6.65"
Original Roush P-51 single belt TVS crank damper: 180MM or 7.09"

Roush Dual Belt "Phased" dampers:

144MM or 5.67"
169MM or 6.65"
183MM or 7.20"

Roush Dual Belt Snout pulleys:

73MM or 2.87"
90MM or 3.54"

Single belt snout pulleys:

Single belt TVS OEM snout pulley: 3" or 76.2MM
Carmen's 3.47" TVS snout pulley: 3.47" or 88.1MM
VMP tuning 3.25" TVS snout pulley: 3.25" or 82.55MM

M90 stuff:

2.57" pulley = 65.3MM
2.49" pulley = 63.2MM

And now some examples:

With no other mods and a P-51 low compression engine (8.5:1) the 180MM single belt TVS crank damper and 3" (76.2MM) snout pulley yields a drive ratio of 2.36:1 and about 15-16 PSI

With no other mods and an unmodified, stock compression 4.6 GT engine, a stock GT damper (169MM/6.65") and the stock 3" TVS snout pulley (76.2mm) yields a drive ratio of 2.22:1 and about 12-13 PSI

With no other mods and an unmodified, stock compression 4.6 GT engine, a stock GT damper (169MM/6.65") and Carmen's 3.47" TVS snout pulley (88.1 mm) yields a drive ratio of 1.92:1 and about 10-11 PSI

Now, take the last example I just gave, and add long-tube headers and high flow cats: You drop 2-3 PSI, but make more horsepower!

What does it all mean? Well, you really can't say that a crank damper and snout pulley is going to give me X amount of boost unless you also consider your other mods: Engine compression, displacement, headers, ported heads, and cams all play a role in what final boost a car will make.

With the above information, however, you can calculate your own drive ratios when looking at a setup and come up with a pretty good idea of what boost you are looking at (at least on a TVS setup).

You can also see that Roush kind of "missed the boat" on non-forged phased TVS offerings...the Phase 1 has a 1.6:1 drive ratio, and is too little...around 7 or 8 PSI. The Phase 2 has a drive ratio of about 2.1:1 and is too much boost IMHO for a non-forged engine...at around 11-12 PSI. They keep from blowing up by making pig-rich tunes that foul your cats. They need a ratio on the single belt setup of around 1.9:1...which is what a custom 3.47" pulley offers - and gives you about 10-11 PSI peak. With headers, it gives you 9 PSI.

The Phase 3 dual belt, if you are forged, however - is sweet! It's drive ratio is 2.5:1. It is roughly the equivalent drive ratio of the old TVS single belt P-51 damper (180mm / 7.09") coupled with a 2.8" (71.1MM) snout pulley (That ratio is 2.53:1) which should yield 20-21 PSI on a stock compression forged engine, about 18-20 on an 8.5:1 CR forged engine, and 15-18 on a forged engine with headers and high flow cats. At 7,000 engine RPM, that blower would be spinning at 17,500 RPM - just below the max of around 18,000 that Eaton recommends for the rotors.

 

[drive_55_not]

With no other mods and an unmodified, stock compression 4.6 GT engine, a stock GT damper (169MM/6.65") and Carmen's 3.47" TVS snout pulley (88.1 mm) yields a drive ratio of 1.92:1 and about 10-11 PSI

My kit came with Carmen's 3.47" pulley and I made 465rwhp/430rwtq @9.5lbs on my otherwise stock 2010 3v when I installed it back in the fall of 2010 ..

With a 3.25" upper I saw 11.5lbs and made 485/450. Saw a lot of belt slip.

Boost being addictive as it is, I switched to a 3" upper [stock GT500 10 rib pulley] and saw 14lbs, made 530rwhp/490rwtq with a set of Comp 127300 cams, Ran that setup for a little more than a year before building my 1st shortblock.

I also had to install an 8-rib pulley setup to cure belt slip to run the 3" pulley.


.

 

[golkhl]

Amazing info DiMora, thank you.
I am currently running a Roush TVS Phase 1 kit on my 08 Bullitt.
With the stock 105mm blower pulley, and an oem diameter ATI super damper, my car make 5-6 psi on the street and 440 rwhp/393 rwtq.
If the 85mm makes 10-11psi, that might be a bit much for my stock engine.
Thanks again for the info.

 

[golkhl]

6.78” ATI Super Damper(172.2mm) / 105mm blower pulley= 1.64 drive ratio.

6.78” ATI Super Damper(172.2mm) / 85mm blower pulley= 2.02 drive ratio.

 

[DiMora]

Find an 88MM pulley (DOB can make you one or check with Roush and VMP) and put some longtube headers on.

You’ll make 9 PSI and 475-485 RWHP at 17 degrees timing on 93 Octane.

That’s what I’m running.

 

[Midlife Crises]

Fun stuff guys. I’m running a Roush R2300 packaged by Brenspeed as a 560HP kit. With a 3.5” pulley and the stock lower it shows 10psi with my set up. Switching to a 2.75” pulley I see 15psi on my gauge.

 

[DiMora]

Fun stuff guys. I’m running a Roush R2300 packaged by Brenspeed as a 560HP kit. With a 3.5” pulley and the stock lower it shows 10psi with my set up. Switching to a 2.75” pulley I see 15psi on my gauge.

The Roush and Brenspeed “kit” numbers are always a bunch of nonsense...what matters is your wheel rear horsepower.

560 -10% puts your RWHP in the low 500’s RWHP which is about right.

 

[Midlife Crises]

Brenspeed says right in the add that is flywheel HP. About 500 at the wheels is believable. No Dyno in my neck of the woods so I don’t know.

 

[golkhl]

Butt dyno and smiles per hour are all that matter.

 

[golkhl]

I have run my TVS with the 105mm pulley since installing the kit in January 2014, now have the itch for a few more psi. Car already has cooling(Afco heat exchanger, 2013 GT500 Fan, HD aftermarket aluminum radiator, Moroso aluminum tanks, 2010 GT500 hood vent). Fuel system mods are: KB boost a pump and S&H wire upgrade from battery to fuel pump control module. Limiting factor is the 91 octane gas here in Vegas.

 

[Midlife Crises]

Only have 90 octane here in Alaska so I know what you mean. I add Torco but what a hassle to mix fuel.

 

[eighty6gt]

I have 82 and 85mm pullies around which may fit this thing. Would pretty much give away. I will do a quick drawing of them (this coming week, on vacation now,) to compare back spacing. They are from Justin's TVS, which afaik is the same.

 

[429244]

Fun stuff guys. I’m running a Roush R2300 packaged by Brenspeed as a 560HP kit. With a 3.5” pulley and the stock lower it shows 10psi with my set up. Switching to a 2.75” pulley I see 15psi on my gauge.

When you put that pulley on your tvs, did you have to machine the nose of the supercharger or did it just bolt right on? Is the 2.75" pulley the Spine pulley that Brenspeed sells?
Thanks.

 

[Midlife Crises]

Yes the 2.75 pulley is the spine drive that Brenspeed sells. The pulley bolted right on with no modifications required to the blower snout. I also changed the belt and put a larger idler near the blower to get maximum wrap on the 2.75. I have not noticed belt slippage and it makes 15-16 psi at 6500.

 

[429244]

Yes the 2.75 pulley is the spine drive that Brenspeed sells. The pulley bolted right on with no modifications required to the blower snout. I also changed the belt and put a larger idler near the blower to get maximum wrap on the 2.75. I have not noticed belt slippage and it makes 15-16 psi at 6500.

Thanks for this info. Do you remember what size belt? When I called there, they said I will need the Phase 2 belt with the 2.75 pulley. I was just about to order a Griptec pulley from Beefcake when I found your post.

 

[Midlife Crises]

429244
I don’t know if your belt path is the same as mine but this is what fits and works on my layout. My alternator is next to the blower and I am using the Roush belt tensioner.(just like stock only stronger). With the 4” pulley (phase 1) on the blower use belt R07020041-13AA. PN 403805. 134”.
With 3.5” pulley(phase 2) use the same belt and replace one of the upper idlers with a 90mm unit.
To run the the 2.75” pulley use belt R07020062-13AA. PN 421160. 132.9”.
I purchased these parts from Brenspeed as the car evolved so I can not speak to other venders. PS. A tune will be needed for sure.

 

[429244]

429244
I don’t know if your belt path is the same as mine but this is what fits and works on my layout. My alternator is next to the blower and I am using the Roush belt tensioner.(just like stock only stronger). With the 4” pulley (phase 1) on the blower use belt R07020041-13AA. PN 403805. 134”.
With 3.5” pulley(phase 2) use the same belt and replace one of the upper idlers with a 90mm unit.
To run the the 2.75” pulley use belt R07020062-13AA. PN 421160. 132.9”.
I purchased these parts from Brenspeed as the car evolved so I can not speak to other venders. PS. A tune will be needed for sure.

Thanks for the information.