Boost Pressure, Whipple v Paxton

[69dejavue]

The Shelby catalogue lists the Whipple as using 5 pounds of boost to generate 400 HP. I did not see a listing of the pounds of boost for the Paxton. Does anyone know the actual figures? I inquire as the amount of boost can help determine the longevity of the engine.

 

I realize that boost is not the only factor in determine the longevity.

 

Thank you

[ShelbyPilot]

My boost gauge typically reads 8-9 pounds for my Paxton.

[SGT2666]

Most of the Whipples being installed are 11psi .

[ShelbyGT#3658]

They are 2 whipples to chose from (well same one with different pully and intercooler) . Basicaly the more HP the higher the boost.

 

socaljafo what boost gauge set up do you have? Do you have the shelby center gauge pod? If so, how is the fit? The center gauge pods that I have seen fit worse than our hood scoops.

[SGT2666]

They are 2 whipples to chose from (well same one with different pully and intercooler) . Basicaly the more HP the higher the boost.

 

socaljafo what boost gauge set up do you have? Do you have the shelby center gauge pod? If so, how is the fit? The center gauge pods that I have seen fit worse than our hood scoops.

 

 

I was just saying not many buying the 500hp Whipple. I'm not to excited about the center guage set up either, this is what I'm leaning toward atm. Speed of Sound

[clark17357]

I was just saying not many buying the 500hp Whipple. I'm not to excited about the center guage set up either, this is what I'm leaning toward atm. Speed of Sound

 

Just my two cents, but it seems like there are more and more people opting for the Whipple given the manner in which it delivers its power, i.e., from low rpms all the way across the power band. I know I changed my mind from Paxton to Whipple due to that fact. Nice problem, huh? Which insanely powerful direction to go? Paxton or Whipple? Jim

[ShelbyGT#3658]

Nice option Wado. If you get one, let me know what you think.

[07SGT4578]

I was just saying not many buying the 500hp Whipple. I'm not to excited about the center guage set up either, this is what I'm leaning toward atm. Speed of Sound

 

 

you may also consider what roush and saleen have to offer, I believe they only hold two guages but if i remember correctly they look nice

[SGT2666]

you may also consider what roush and saleen have to offer, I believe they only hold two guages but if i remember correctly they look nice

 

 

Thats the pods in the middle of the dash right? If thats the one I think they look great, a little pricey like $700+ as I remember and they drill the dash. Drilling the dash I just couldn't do lol

 

Just my two cents, but it seems like there are more and more people opting for the Whipple given the manner in which it delivers its power, i.e., from low rpms all the way across the power band. I know I changed my mind from Paxton to Whipple due to that fact. Nice problem, huh? Which insanely powerful direction to go? Paxton or Whipple? Jim

 

 

Gotta say I love my Whipple :D

[ShelbyPilot]

socaljafo what boost gauge set up do you have? Do you have the shelby center gauge pod? If so, how is the fit? The center gauge pods that I have seen fit worse than our hood scoops.

 

 

I have the Shelby center pod. Mine is one of the ones that don't fit too well but I have a preproduction one. When the timing is better, with my wife, I am going to have it covered to match the dash better and remove the gap.

[ShelbyGT#3658]

Just my two cents, but it seems like there are more and more people opting for the Whipple given the manner in which it delivers its power, i.e., from low rpms all the way across the power band. I know I changed my mind from Paxton to Whipple due to that fact. Nice problem, huh? Which insanely powerful direction to go? Paxton or Whipple? Jim

 

 

Yea, I keep changing my mind going back and forth too. I'm still not sure which way to go. I keep thinking I have traction problems now, do I really need more HP down low. I would like to see quarter mile times for both.

[PhoenixCS8]

Edit: From a daily driver stock engine standpoint, I have read about the Paxton and other Centrifugal types you will have to wait longer for it to warm up to operating temperature versus the "roots type" SCs for starters. Also the Air in a Centrifugal has a greater distance to travel than the whipple the whipple capitalizes on venturi effect and the response is so instantaneous with the Whipple that having actually compared the 400 hp FRPP Whipple to a PS1-C Procharger HO tuned with 500 hp the whipple matched it on low end acceleration, torque, and response even though it was 5 psi less because it makes more boost at the low end then the centrifugal type chargers and Turbo chargers - just look at the dyno prints and compare the power curves for yourself out at each manufacture's website. Boost pressure on the SCs non-intercooled and intercooled will very based on ambient conditions ie: cold day versus hot day sea level versus high elevation as most of you know. Before I purchased an SC, I read all the reviews I could from various blogs. Keep in mind that this system is upgradable to 700 HP not all SC systems can match that and of course anything over 400 RWHP on the stock 5R55S is probably asking for it. JDM went 439 RWHP on "Project MILF" and of course theres the claim below of 603 HP which is unwise. One other thing, the stock black intake manifold is composite plastic - how much boost or pressure do you really want to put on it? The roots type sc alleviates this or any future issue if there are any.

 

Whipple has some of the best reviews because Ford Racing supplied the PCM progamming software after hundreds of hours of testing in the field for the 5-6 psi 400HP and 10-11 psi 500 HP HO intercooled SCs to protect the engine and drivetrain especially on the automatic since it is easy to burn up the 5R55S Automatic unless you upgrade it with the kit from Levelten. You can look up "Project MILF" in MMFF for all the specifics. I have the 400 HP right now just installed in 2 days by Sanderson Ford in Phoenix for $1100.00 total. As far as Driveability: Of course a faster, smoother, and far more instantaneous throttle response than my experience with the Procharger (The Procharger is an excellent choice too). I have had no issues since it was installed. The good news is that even normal drivability is improved with this application as it runs smoother. Pulley noise is higher with the smaller idler pulley but wait until you hear this (exactly how it sounds) check it out:

 

Flyby:

 

Inside up to 100 MPH:

 

 

Hood Open Pulley Noise:

 

I would definitely recommend you research this information for yourself read the articles about both FRPP Whipple SC's in MMFF get onto the manufacture's websites.

 

Here's how it looks on my Shelby CS8:

 

 

http://forum.shelbyautos.com/index.php?s=&...indpost&p=33782

 

Hope this helps...

[LuLu]

The underpinnings of our SGT 4.6L-3V engines are stock production engines. Nothing special, and not race prepared.

 

My experience with positive displacement/roots and centrifugal supercharges taught me that "boost" is measured slightly different between these designs. At best, both are "guesses"...Approximates. Moreover, boost gauges are nortoriously innaccurate. Close, but not spot on.

 

If you want to know the truth, read your MAP (manifold absolute pressure) data from the OBDII port with a ScanGauge (www.scanguage.com), or. the AreoForce kit (www.aeroforcetech.com/Fordtech.html).

 

Remember that once you exceed 10 PSI in either design, your "wear and tear" on a stock 4.6L-3V is subjective, a real "coin toss". IMHO, get a good tune from a professional tuner on a dyno, and get it done under the worst possible atmospheric conditions i.e. hot day, high humidity. The EEC will handle it from there.

 

Shelby/SAI has to be conservative here. They cannot afford to market any power adder that will gamble with engine failure. They cannot afford the public "whack" to their automotive reputation. Thus, you may expect the pulley size and performance tune to be conservative. I am sure they do not want to hear a public outcry of engine failure due to their retail offerings.

 

IMHO...The bottom line is that if you cross the 475 RWHP limitation from any design, you are in a red zone. IMHO, keep it at 450 or under, or, best be ready to cough up some bucks for a new short block...IMHO.

 

If you want 500+ RWHP, buy yourself a pro-built engine, and park you stock 4.6L in a corner somewhere.

 

Just my .02C on it gents, happy motoring.

 

EDIT...One other thing. The positive displacement/roots supercharger delivers more power from a standing start, no argument here. So, if stop-light racing and 1/8 mile drag racing is your thing, go with the Whipple/Eaton options.

 

However, if long term breathing is your thing, i.e. 1/4 mile drag, autocross and road racing, go with the Paxton/ProCharger centrifugal.

 

PD/Roots can spin only so fast, and they run of of breath over 5000 RPM. The centrifugals are "breathless", they can spin as high as 20,000 and still deliver boost.

 

Don't believe me? Look up the specs on national NMRA champs. Not a PD/Roots charger among them.

[csm198]

The roots sure looks and sounds bad as hell!

[Strawman]

I've been toiling over this decision for some time, and I've decided on the Paxton for a few reasons. The lineage between the Paxton and the Mustang goes back 40 years and I feel the car is a "purer" Shelby with the Paxton. I can keep the strut tower brace with the Paxton, and I think the engine is better looking with the polished Paxton than with the Whipple. I understand that I'm giving up some low end torque, but if I really want stoplight quickness there are other mods that can accomplish this, such as going to a higher rear end gear. It's certainly a personal choice, but in the end it was an easy decision for me.

[Torrence]

I've been toiling over this decision for some time, and I've decided on the Paxton for a few reasons. The lineage between the Paxton and the Mustang goes back 40 years and I feel the car is a "purer" Shelby with the Paxton. I can keep the strut tower brace with the Paxton, and I think the engine is better looking with the polished Paxton than with the Whipple. I understand that I'm giving up some low end torque, but if I really want stoplight quickness there are other mods that can accomplish this, such as going to a higher rear end gear. It's certainly a personal choice, but in the end it was an easy decision for me.

 

 

That is a good choice, since gears will help.

Since I have the Whipple, I won't go higher in gear, i'll be sticking with the 3:55. On the flip side of things, I don't need the gears since the Whipple gives me instant insane BOOST.

[SGT2666]

So LuLu you seem to be well informed on this stuff, whats up with the 5k RPM cut off you're talking about? Drag racers have been using gimmies forever and certainly weren't limited to 5k is this a Whipple design issue?

[LuLu]

So LuLu you seem to be well informed on this stuff, whats up with the 5k RPM cut off you're talking about? Drag racers have been using gimmies forever and certainly weren't limited to 5k is this a Whipple design issue?

 

Nope, not a design flaw at all, not even close to that, so, let's not start such a discussion. Don't paint my comments as being negative against any particular product. Rather, it's a matter of personal choice, and picking the right components for the style of driving you wish to pursue.

 

It's not really a "limitation", more a matter "volumetric efficiency". The Roots/PD blowers have limitations in how much air they can process internally, and still fit under the hood. The "gimmies" you mention, don't have hoods, and are mostly big block (500 plus CID) engines. A GMC 671 blower was popular a long time ago, yes. But, if you look at the winning champs of the last five years by class, (renegade, Outlaw, ect) twin turbos and centrifugals seem to rule the roost from funny cars down through the ranks to the novice ET bracket racers.

 

We're talking about dual purpose street race cars here, and Kenny Bell is one manufacturer who is very frank and upfront about his product's limitations by advertizing blowers with openly stated liter capacity. Others are not so frank. My point is, is that there comes a point in RPMs where the blower can run flat and not produce any more power than the engine is producing on it's own. Centrifugals can run flat as well, but not until well beyond the red-line of the base engine, i.e. 281 CID.

 

Would you expect a Holley 650 CFM carb to outperform a 750 double pumper? Hell no, but it's the same principles at play. CFM production through the RPM range of the base engine.

 

My point is (and has always been) to pick the blower style that work for you. Short term flat out racing, such as an 1/8 mile drag race, or, stoplight Gran Prix, the Roots/PD blowers kick azz. Lower 60 foot and 330 foot times, if you're a betting man on those numbers.

 

Long term racing, such as full 1/4 mile drag racing and road course racing, the centrifugal is your best bet. The MPH gain in the second 1/8 mile of a centrifugal bower car will never be run down by a Roots/PD blown car. The time slips prove it. The SGT has a 281 CID engine and can process only so much supercharged air. When that supercharged air runs flat at 5000 RPM, you are leaving power and acceleration on the table. Again, you must read the MAP numbers to know this, aftermarket gauges can't tell the truth at these RPMs.

 

Please...I mean no criticism towards any product/design. Buy what works for you.

 

Just my .02C, carry on gents.

[SGT2666]

Nope, not a design flaw at all, not even close to that, so, let's not start such a discussion. Don't paint my comments as being negative against any particular product. Rather, it's a matter of personal choice, and picking the right components for the style of driving you wish to pursue.

 

It's not really a "limitation", more a matter "volumetric efficiency". The Roots/PD blowers have limitations in how much air they can process internally, and still fit under the hood. The "gimmies" you mention, don't have hoods, and are mostly big block (500 plus CID) engines. A GMC 671 blower was popular a long time ago, yes. But, if you look at the winning champs of the last five years by class, (renegade, Outlaw, ect) twin turbos and centrifugals seem to rule the roost from funny cars down through the ranks to the novice ET bracket racers.

 

We're talking about dual purpose street race cars here, and Kenny Bell is one manufacturer who is very frank and upfront about his product's limitations by advertizing blowers with openly stated liter capacity. Others are not so frank. My point is, is that there comes a point in RPMs where the blower can run flat and not produce any more power than the engine is producing on it's own. Centrifugals can run flat as well, but not until well beyond the red-line of the base engine, i.e. 281 CID.

 

Would you expect a Holley 650 CFM carb to outperform a 750 double pumper? Hell no, but it's the same principles at play. CFM production through the RPM range of the base engine.

 

My point is (and has always been) to pick the blower style that work for you. Short term flat out racing, such as an 1/8 mile drag race, or, stoplight Gran Prix, the Roots/PD blowers kick azz. Lower 60 foot and 330 foot times, if you're a betting man on those numbers.

 

Long term racing, such as full 1/4 mile drag racing and road course racing, the centrifugal is your best bet. The MPH gain in the second 1/8 mile of a centrifugal bower car will never be run down by a Roots/PD blown car. The time slips prove it. The SGT has a 281 CID engine and can process only so much supercharged air. When that supercharged air runs flat at 5000 RPM, you are leaving power and acceleration on the table. Again, you must read the MAP numbers to know this, aftermarket gauges can't tell the truth at these RPMs.

 

Please...I mean no criticism towards any product/design. Buy what works for you.

 

Just my .02C, carry on gents.

 

 

I by no means meant to twist your words or infer you were negative about someones product. Just looking for information In my view the 5k limit is somewhat of a design limitation. If I'm making as much power as the stock motor can stand already I'm not sure this is an issue for me. Seems like it becomes more an issue if you wish to go further. So over 5k the roots style quits pulling in more air correct it peaks at 5k? So as you rev further your boost will fall of to some extent because the motor needs increasing amounts of air as the RPM increase is that correct?

 

Since the roots style blowers make almost full boost right off the bottom they have to conrol boost pressure with a waste gate no? If the blower makes enough volume to maintain the boost setpoint through out the rev range by 5k there is no need to keep building boost with RPM is there?

[EricM]

 

PD/Roots can spin only so fast, and they run of of breath over 5000 RPM.

 

 

 

Every dyno chart I've seen for a KB, Saleen or Whipple on a 4.6 shows it building power to peak at 6500 RPM. They seem to actually make the biggest increase over stock between 5000 and 6500, because that's where the stock engine's flat.

 

What's being put in the big power Shelbys, like the SS and KR?

[fatboy_merged]

I was just saying not many buying the 500hp Whipple. I'm not to excited about the center guage set up either, this is what I'm leaning toward atm. Speed of Sound

 

where do u accually get the 2 1/16" guages themselves? does ford dealership sell them?

[LuLu]

I by no means meant to twist your words or infer you were negative about someones product. Just looking for information

Understood, it's cool.

In my view the 5k limit is somewhat of a design limitation. If I'm making as much power as the stock motor can stand already I'm not sure this is an issue for me. Seems like it becomes more an issue if you wish to go further. So over 5k the roots style quits pulling in more air correct it peaks at 5k? So as you rev further your boost will fall of to some extent because the motor needs increasing amounts of air as the RPM increase is that correct?

Well, "design limitation" as you explain it now would be correct, but this is why blowers come in different sizes. The Kenny Bell PD "twin screw" is available in 1.7, 2.2 and 2.8 liters. Depending on your final CID, combustion chamber CC, and head/cam/valve choices, a 1.7L may be to small to deliver supercharged boost through the engine's RPM red line. OTOH, the 2.8L on a bone stock 4.6L-3V puts way too much pressure on internals at lower RPM. This could be fatal if not tuned right with the appropriate pully in place.

 

My Marauder S had a stock 4.6L-4V with a Vortech S trim and a 3.48 pulley making 9-9.5 PSI @ 6200 RPM. Blew the top off the #8 piston by running lean for a split second. I rebuilt the engine with forged internals, stock cams and some custom head work, and I replaced the S trim with a T-trim with a 2.90 pulley making 14-16 PSI through 6500 RPMs. It was quite an exciting car to drive again, considering it's weight, and size.

Since the roots style blowers make almost full boost right off the bottom they have to conrol boost pressure with a waste gate no? If the blower makes enough volume to maintain the boost setpoint through out the rev range by 5k there is no need to keep building boost with RPM is there?

 

Not much difference between a waste gate and a blow off valve, and yes, all blowers should have one or the other at play. Centrifugals use an external (and adjustable) blow off valve, Roots and PD blower have an internal valve. Their purpose is to vent out unused boost when decelerating, otherwise things come apart. An external valve can be adjusted to act as a form of power limiter, yes, but you're better off doing some homework and setting things up right the first time.

 

Moreover, all blowers will flatten out, things can spin only so fast. it's a matter of knowing where your power peaks, and teaching yourself to stay in the power band. Those who wind out every gear to the red-line, are not driving the car to it's full winning potential. Driving to the peak of the power band and upshifting back to the beginning of the power band is what wins races.

 

Dyno sheets tell half of the story. A dyno test is static, without wind resistance and road conditions. When you read a dyno report, there may appear to be more HP at higher RPM, but it's torque that moves the car. The objective is not making HP at maximum RPM, but delivering the torque necessary to increase acceleration. Doesn't matter how much HP you see on a dyno report, when you run out of torque, you're running slower, IMHO.

[SGT2666]

where do u accually get the 2 1/16" guages themselves? does ford dealership sell them?

 

 

I'm going to use these guys I think Autometer figure out what you like then find the good price. I'm liking the phantom II's they are white faced during the day and black at night.

[PhoenixCS8]

Autometer "NEXUS" gauges will change colors to match your choice like the 05-08 Mustang Color Scheme.