Whipple Stage 2 pulley size

[2021 Mach 1]

What size pulley comes standard with the Stage 2 Whipple kit? What's the range of pulley size down and up that are available? Lastly, what's the difference in power output on pump fuel between a smaller pulley than standard and a larger pulley than standard? Thank you.

Sponsored

 

[Houdinii_5.0]

The tuning and fuel will be your limitations. There's a large range of pulleys, however most stop at the 3.75 or 3.6 on pump gas. With a lund tune, e85, and fore system I've ran anything from a 3.6 pulley making high 700s to a 3.125 making a little over 900 on e85.

 

[HKusp]

The stock pulley they send with the Stage 2 is a 3.875. At sea level you'll be pushing about 11psi on that pulley.

 

[engineermike]

Roughly 15 hp per pulley size on pump gas. I did a back to back dyno comparison on this from 3.875 to 3.5 on 93 and it was about 45 hp difference. It’s more on e85 because you don’t have to pull timing, like 20-25. I ran as small as 3.25 on 93 but I’d only suggest that if you are very skilled at tuning and logging.

 

[Angrey]

As Mike pointed out, the general rule of thumb on 12:1 compression and pump gasoline with coyote platform is 12-14 psi is starting to ride the edge of what "typical" tuners do with the car. If you find someone as advanced as Mike you could push things further, but the rule of thumb is that's the borderline. Which in this case corresponds to certain pulley sizes (given the motor volume, flow characteristics of the headers, intake, throttle body, etc).

More important than raw "can it work" is the deeper issue that while it might log and appear safe when cold on a dyno, the real risk starts to come into play with fuel quality and heat soaked conditions. Even with good fuel, on higher compression and pump gasoline, when IAT2's are elevated from back to back floggings, you start to get preignition and detonation as the incoming A/F mixture is already superheated beyond safe compressing, hot combustion chamber elements, etc (things like heat range of the spark plugs and gap sizing comes into play as well).

Honestly I wouldn't run anything beyond the recommended pulley size unless you know you're going to condition the shit out of every tank of fuel and/or you know to limit yourself from beating on the car at elevated temps. (which necessitates something like an Ngauge that allows you to constantly keep an eye on important motor data).

 

[engineermike]

The funny thing is we were led to believe that the 3.75 pulley would lose power vs the 3.875 due to knock retard on 93. I proved that to not be true. Also Whipple limited timing on the gen3 to 17-17.5 deg. But the s650 gets a 3.75 pulley and 21 deg timing give or take, and it’s the same engine minus some minor tweaks.

 

[Angrey]

The funny thing is we were led to believe that the 3.75 pulley would lose power vs the 3.875 due to knock retard on 93. I proved that to not be true. Also Whipple limited timing on the gen3 to 17-17.5 deg. But the s650 gets a 3.75 pulley and 21 deg timing give or take, and it’s the same engine minus some minor tweaks.

Was the timing change on the "stage 2" or the stage 1? I read something that the Stage 2 was coming without warranty (something to do with their underwriting) so they might feel like **** it, if we don't have to warrant it, let's up it and sell some units, if it fries, not our problem.

I personally would NOT run 21 degrees of timing on boosted pump 93 with a 12:1 compression, but that's just me. It's playing with fire.

What's even more interesting is the risk analysis. Every good tuner starts off at zero or low timing and adds more timing to see the net results, when you start getting diminishing returns you know it's time to start contemplating whether less and less HP bumps are worth the additional risk. I'm betting from 12-13 degrees it's probably seeing decent gains, but from 20-21 it's probably single digit bumps.

 

[2021 Mach 1]

Thanks guys, that's all very helpful. Question, what if I want to start conservative, like maybe start with a 4.00 pulley on pump gas and Whipple tune? (I already have headers).

 

[DougS550]

As Mike pointed out, the general rule of thumb on 12:1 compression and pump gasoline with coyote platform is 12-14 psi is starting to ride the edge of what "typical" tuners do with the car. If you find someone as advanced as Mike you could push things further, but the rule of thumb is that's the borderline. Which in this case corresponds to certain pulley sizes (given the motor volume, flow characteristics of the headers, intake, throttle body, etc).

More important than raw "can it work" is the deeper issue that while it might log and appear safe when cold on a dyno, the real risk starts to come into play with fuel quality and heat soaked conditions. Even with good fuel, on higher compression and pump gasoline, when IAT2's are elevated from back to back floggings, you start to get preignition and detonation as the incoming A/F mixture is already superheated beyond safe compressing, hot combustion chamber elements, etc (things like heat range of the spark plugs and gap sizing comes into play as well).

Honestly I wouldn't run anything beyond the recommended pulley size unless you know you're going to condition the shit out of every tank of fuel and/or you know to limit yourself from beating on the car at elevated temps. (which necessitates something like an Ngauge that allows you to constantly keep an eye on important motor data).

Do you happened to know the equivalent, if you ran a 3.75 on a whipple stage 2 system which has a 20% overdrive crank pulley. What size whipple stage 2 blower pulley with a stock crank pulley would you have to run to make the same boost as the 20% OD? If you have to take your shoes off to count that high, that's OK. LOL

 

[J17GT]

Do you happened to know the equivalent, if you ran a 3.75 on a whipple stage 2 system which has a 20% overdrive crank pulley. What size whipple stage 2 blower pulley with a stock crank pulley would you have to run to make the same boost as the 20% OD? If you have to take your shoes off to count that high, that's OK. LOL

From the whipple install manual for a Gen5 3.0 stage 2 kit:

 

[Angrey]

The stock balancer size is 6.57." The overdrive (from ATI) of 20% is 7.88."

You could do the crude 20% and trust it so, 3.75*.8 = 3.00"

Or you could do the actual math and go 3.75*6.57 = 7.88*x: X = 3.12"

 

[DougS550]

From the whipple install manual for a Gen5 3.0 stage 2 kit:

Wow, the 20% really adds boost. Does anyone know any negative drawbacks from overdrive the AC compressor, water pump and alternator?

 

[DougS550]

The stock balancer size is 6.57." The overdrive (from ATI) of 20% is 7.88."

You could do the crude 20% and trust it so, 3.75*.8 = 3.00"

Or you could do the actual math and go 3.75*6.57 = 7.88*x: X = 3.12"

True, BUT: I could just use the chart given below. LOL

 

[engineermike]

Was the timing change on the "stage 2" or the stage 1? I read something that the Stage 2 was coming without warranty (something to do with their underwriting) so they might feel like **** it, if we don't have to warrant it, let's up it and sell some units, if it fries, not our problem.

The timing numbers I quoted are all stage 2. I have no idea what timing stage 1 runs.

I personally would NOT run 21 degrees of timing on boosted pump 93 with a 12:1 compression, but that's just me. It's playing with fire.

I've done it, but I snuck up on it really slow and it was on only 10 psi boost. I was led to believe by big tunerz that less boost and more timing was the key to making power on pump, but the car was a terd like that.

 

[Offsetz33]

I sort of have a similar question - my car is a Whipple stg2 and came out of CA. I’m at about 4200ft elevation and looking to have a custom tune. Where should I be for pulley size at this elevation on pump gas? Thinking of having a tune for running boostane and a basic 91 if I need to use it.

Sponsored