GEN 1 Need some help

[Cristian]

I have a roush since it came with the truck but I would've preferred the whipple. Whipple makes more power

 

[EricM]

There are incidentals like serviceability, but the crux of the matter is you are buying a belt driven air compressor. You want the one that moves the most air while using the least amount of input power to do so in the RPM range you plan to spin it. The only way to determine that for sure is to see the compressor maps.

Unfortunately, the aftermarket companies keep that close to the vest as far as I've seen. If the maps were available, you could easily estimate the airflow required for your HP goal, and then pick the most efficient blower for the desired airflow rate and blower speed. Instead, you are pretty much stuck with asking people's opinion and going off a bunch of advertising info provided by the very people who want your money. You'd think dyno numbers could tell the tale, but you cannot rely on those either. All dynos vary, and they can all be adjusted or manipulated.

From an efficiency standpoint, your best best is probably going to be buying the one that was most recently updated, which is the Whipple, as the roots/twin screw blowers have only gotten more and more efficient with each new version.

Before you go with either supercharger, I'd make sure you understand the difference between a roots style superchrager, which is what the Roush is, and a twin screw supercharger which is the Whipple.

As I understand it, the Roots style should be more efficient and cooler when you are just cruising around out of boost. In that case, the bypass valve will be open and excess/pressurized air will be circulated back to the inlet side of the supercharger. The roots allows most of the air to go between the screws and the case, round and round it goes, no big deal. The twin screw will be passing most of the air through the screws though, heating/compressing it everytime. It does have some airflow near the case walls similar to a Roots blower, but it's not the primary method of moving air like a Roots style. Most of the air is going through the screws and it has to be compressed if it goes through the screws. This non-boost operating advatngae is why Ford always goes with roots blowers as OEM and not twin screw superchargers.

Be aware that both styles are positive displacement superchargers which function very uniquely. They are very sensitive to inlet restrictions (ie get the biggest MAF/TB/piping/filter possible) however, the don't really care much about downstream restrictions. Headers and a bigger exhaust will get you some gains, but it's not really needed with a positive displacement supercharger. The stock setup will get it done just fine.

 

[Landon T]

I completed the Roush 590/590 kit about 5000 miles ago. Only because the roush kit was more accessible in my region and the support from a local speed shop gave me some peace of mind. Installed, drove for a week to make sure everything was good. Then talked to JDM and got an improved all around tune for the truck.

Also did the twin TB, Melling upgraded oil pump and a JDM oil catch can.
Nothing major other than the oil pump but its a great daily driver in town, on the highway, in the heat and cold.

Also changed the plugs to a NGK 6510 while doing the install.

Information claims (Take with a grain of salt)

• Stock Roush Raptor 6.2L = About 440 RWHP and 477 RWTQ
• Modified = About 510 RWHP and 500 RWTQ

Its enough for me and totally changes the truck love.

 

[MTF]

Before you go with either supercharger, I'd make sure you understand the difference between a roots style superchrager, which is what the Roush is, and a twin screw supercharger which is the Whipple.

As I understand it, the Roots style should be more efficient and cooler when you are just cruising around out of boost. In that case, the bypass valve will be open and excess/pressurized air will be circulated back to the inlet side of the supercharger. The roots allows most of the air to go between the screws and the case, round and round it goes, no big deal. The twin screw will be passing most of the air through the screws though, heating/compressing it everytime. It does have some airflow near the case walls similar to a Roots blower, but it's not the primary method of moving air like a Roots style. Most of the air is going through the screws and it has to be compressed if it goes through the screws. This non-boost operating advatngae is why Ford always goes with roots blowers as OEM and not twin screw superchargers.

Dustin said that any time you lightly enter into the throttle, there’s an under-the-curve power scenario [separate from wide open throttle] that you’ll feel.

“There’s a lot of midrange and part-throttle areas that the supercharger is working efficiently at, making the engine more efficient, and making more power – and that’s a huge advantage over any other type of forced-induction application.” he explained. “It’s a difficult area to measure, meaning the useful RPM range of normal driving – but a twin-screw supercharger tremendously increases performance in those areas, separate from even wide-open throttle. The overall performance is enhanced, and you feel like you have a much larger cubic-inch engine at any throttle input.”

While it’s obvious that your hot rod’s fuel economy could change after installing a twin-screw supercharger, it might not be as much of a decrease as one would assume. Because Whipple superchargers use a high-flow bypass valve, normal city driving, and low-RPM highway cruising, can actually mimic a naturally aspirated application quite well thanks to the bypass valve equalizing pressure above and below the supercharger, resulting in significantly lower parasitic losses.

In most cases, IATs are measured at the mass airflow sensor inside of the air intake, but Dustin said this isn’t the most accurate way to measure them. According to Dustin, finding the difference between the temperature at the MAF and the air post-intercooler, is the most accurate way of measuring them.

In most cases, IATs are measured at the mass airflow sensor inside of the air intake, but Dustin said this isn’t the most accurate way to measure them. According to Dustin, finding the difference between the temperature at the MAF and the air post-intercooler, is the most accurate way of measuring them.

“Almost always, we incorporate the IAT sensors post-intercooler,” Dustin elaborated. “Therefore, we have the actual temperatures entering the combustion chamber. The other part of that is, in a lot of our systems, we have the advantage of being able to rewrite Ford’s software to allow us to run two sensors. We’ve run one sensor on the inlet side at the MAF where the air is being taken in, and another sensor post-intercooler – so we’re actually able to get the Delta between the two.”

This method allows Whipple to do far more with its calibration; whereas alternative aftermarket versions will require you to pull the sensor from the mass airflow sensor and direct it into the manifold, giving you only a singular reading.

“You won’t have variance with this method,” Dustin said. “These readings help us set more safety standards, and allow for more timing safely. Having the Delta between the two allows us to tune more aggressively, yet stay conservative enough to be in the ‘safe zone’ for tuning.”

You often hear others comparing roots-style superchargers to twin-screw iterations, and it’s easy to see why. Both of these supercharger versions are similar in appearance, and even construction – but that is where the similarities end, as Dustin told us.

“The main differences basically boil down to two things – the first being temperature,” he said. “In generic terms, the roots style supercharger has a hotter discharger temperature. So, as manifold pressure increases, the Delta between a twin screw compressor and roots gets greater.

“In turn, what you can typically do with timing and air/fuel ratio on a twin screw style of supercharger, is less as the RPM and timing increases on a roots style. The longer you’re on the throttle, and the longer it’s in boost, the higher the temperature will rise with a roots-style blower, so long as all parts are equal,” Dustin elaborated. “That typically means that the roots blower would fall off on the top end because the temperature is ever increasing. Of course, part of the equation is when it’s leaking more, it’s taking more power to drive – it’s a direct relationship between temperature and power consumption. The parasitic loss and the temperature will grow as the RPM is increased.

Here's the site where I copied the text:
https://www.fordnxt.com/tech-storie...perchargers-101-heres-the-whipple-difference/

 

[EricM]

“In generic terms, the roots style supercharger has a hotter discharger temperature. So, as manifold pressure increases, the Delta between a twin screw compressor and roots gets greater.

I'd agree with that, but I'd clarify that we are talking about discharge temps while under boost only.

During the 99% of time you are NOT in boost, the twin screw runs hotter. He tries to poo-poo that early on in the wall of text, but the roots style blowers have the same high flow bypass, plus they do not compress the air being bypassed like the twin screw does.

I have a Whipple twin screw blower on my Cobra so I have nothing against Whipple or twin screw compressors, but the roots style blowers do have some advantages in some situations, just like the twin screw do in some situations. Again, there's a good reason Ford (or any OEM that I know of) typically only use roots style superchargers on OEM vehicles. I know Ford ran a twin screw on the first Gen GTs with the S/C 5.4L, but other than that, I've only seen roots blowers on production vehicles.

 

[MTF]

When Whipple is not under boost the bypass valve opens up and then there is equal pressure thought out.
NA air will bypass the Twin screws for the most part.

Ford used the Eaton blower because it's cheaper and guys won't kill themselves either.

 

[EricM]

Whipple not under boost the bypass valve opens up and then there is equal pressure thought out.

Ford uses the Eaton blower because it's cheaper and guys won't kill themselves either.

I don't think you really understand what's happening inside the twin screw s/c vs a roots s/c.

Yes, there is a bypass valve. What is the bypass valve? It's a hole that connects the inlet to the outlet side of the blower. When you are cruising out of boost, the supercharger moves more air than the engine needs to make the power you are asking for with your right foot. So, they use a vacuum operated valve that sees you are not in boost and opens the bypass. With the bypass open, the excess air that the engine can't use is circulated back to the front of the supercharger instead of building pressure/boost.

The key thing is this- on a twin screw, some of that that bypassed air has been through the screws once, and is about to go through again. It gets heated/compressed each time. This does not happen with a roots blower. With a roots style s/c the air is not compressed in screws, it's "blown" down by the rotors against the case walls. A roots supercharger is literally where the term "blower" comes from. When a roots style s/c is not in boost and it's bypass valve is open, the bypassed air does not get compressed/heated on each trip through the blower. So a twin screw out of boost compared to a roots out of boost 1) takes more power 2) heat soaks the case and 3) heat soaks the IC system as well.

The roots style is more efficient and that is why the OEMs choose them. There's really no difference in cost between a roots s/c and a screw s/c when you buy them by the tens of thousands.

 

[MTF]

I know exactly how things work.

The bypass valve is in the front before the twin screws and between the upper (compressor) and lower (intercooler).
While the compressor is still spinning it does not need to rob horse power to continue compressing every bit of air.
That's why it's more efficient than a roots style.

 

[EricM]

Sigh...

Lets clarify exactly when each is more efficient. I'm talking about the efficiency when the bypass is open.

A twin screw is not more efficient than a roots style when it out of boost. If you are saying it is, you are wrong about that.

If you want to know why you are wrong about that, I very clearly explained why above.

 

[MTF]

That's only your opinion, while it's a big debate on the web.
I'll stick to my opinion.

Cheers