twin screw is better than centrifugal

[black mamba1]

You guys are not going to believe this. In light of all the debate going on about which superchargers are better, the Roe charger or the Paxtons, I said to hell with it; I am simply going to ask the tuners themselves. I emailed one of the most respected tuners that installs nothing but Paxtons on Vipers. I asked him, all things being equal if two same year Vipers raced in the 1/4 mile and one had a Paxton and one had the Roe, he said the Roe supercharged car would win b/c it makes more overall power under the curve. He did go on to say that Paxton equipped cars are street legal and hold value better, but I know most of you are like me and dont give a damn about resale value or smog n fog. Whaddya think?

 

[DocAdam]

I would add that you specified 1/4 mile and I would say no sh;t really? A positive displacement SC is always going to be the choice of drag racers everywhere.

Unfortunately the world is not about the 1/4 mile and you are still trying to compare apples and oranges.


That being said, I am very interested in the Roe development because it suits my preferred driving style better than the centrifugal.

 

[black mamba1]

You are right in that I only specified the 1/4 mile, b/c that is what most car drivers look at when comparing sports cars. For example, there is so much hoopla about the Z06 running the 1/4 in 11.7 while the Vipers are running 12.0, even though the Viper spanks the Z06 in many other areas, the overall view is that the Z06 is a faster/quicker car. But I would be very interested in seeing what the twin screw would do vs the Paxton in a road race or a 0-200 mph race.

 

[zorroespanol]

You guys are not going to believe this. In light of all the debate going on about which superchargers are better, the Roe charger or the Paxtons, I said to hell with it; I am simply going to ask the tuners themselves. I emailed one of the most respected tuners that installs nothing but Paxtons on Vipers. I asked him, all things being equal if two same year Vipers raced in the 1/4 mile and one had a Paxton and one had the Roe, he said the Roe supercharged car would win b/c it makes more overall power under the curve. He did go on to say that Paxton equipped cars are street legal and hold value better, but I know most of you are like me and dont give a damn about resale value or smog n fog. Whaddya think?

Just look at what top fuels and alike run... roots.

Road racing cars? turbos and centrifugal scs.

Again, depends on your style of driving. For me, I'd go with #2.

 

[Joseph Dell]

Hum... In my mustang days, we ran roots vs. centrifugal all the time. 2 cars with equal power would line up. The roots would be ahead off the line, but the centrifugal would fly by at the top end.

Put another way, I disagree with your bolt, it's-my-6th-post-on-the-VCA-board assessment.

JD

 

[SnakeEye]

Hum... In my mustang days, we ran roots vs. centrifugal all the time. 2 cars with equal power would line up. The roots would be ahead off the line, but the centrifugal would fly by at the top end.

Put another way, I disagree with your bolt, it's-my-6th-post-on-the-VCA-board assessment.

JD

Ha Ha. What JD said, centrifugal - AND it's available today.

 

[InjectTheVenom]

Ain't it great to have choices like these and put up a good discussion learning lots about it

 

[plumcrazy]

i still wanna see 1tony1 run 2 cars that are stock except the s/c's.

1 paxton and 1 roe. but they'd have to be of similiar rwhp. to me, that would end this debate.

are there 2 cars like this that would be willing to do it?

 

[black mamba1]

Let me ask the question to you more experienced Viper owners/racers...any of you Viper owners w/ twin screw chargers ever pulled up to another Viper or comparable car on the road at say, doing about 65 mph, and both of you "hit it"? If so, how does the twin screw Viper compare w/ the centrifugal cars in say a 65-140 mph or so contest? I know that JD seems to have addressed this scenerio somewhat. What are your views?

 

[Joseph Dell]

Let me ask the question to you more experienced Viper owners/racers...any of you Viper owners w/ twin screw chargers ever pulled up to another Viper or comparable car on the road at say, doing about 65 mph, and both of you "hit it"? If so, how does the twin screw Viper compare w/ the centrifugal cars in say a 65-140 mph or so contest?

Being that this would be unsafe, I would hope that no one does this on the street.

But even then, there are too many variables to compare. And one of them is driver skill.

But i'll bite on your theoretical question.

If you are 65mph and you both downshift it into 3rd gear and hit it, the positive displacement car will get-up-and-go very fast. the paxton isn't at optimum power band yet (nor it is making as much boost) so it will lag behind a second or so. but then, in theory, it will catch up.

Unless 1TONY1 is driving. then the paxton car always loses.

But if you look at the power bands of the cars (peak hp and tq) you'll see that the twin-screw has a different range of power... and this is where the difference comes from.

in theory.

JD

 

[DAMN YANKEE]

Now matter how you cut it, they are both great!

But there is just something special about a turbo in the engine bay.

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[black mamba1]

I have to admit I get carried away and do "hit it" when my Viper runs upon an opponent (Porsche, Ferrari, etc). As you know, it doesnt take long to get up to 140 mph when the adrenaline kicks in, and I have only done it on open highway. Having said that, "a second or so" is a long time in a race...I am just curious, at what speed will the Paxton catch up? If both cars are traveling at say, 130-140 mph before the Paxton closes the gap in my view the Paxton loses.

 

[SylvanSRT]

Ok Black Mambaa1 do you really have a Viper? (post some pics i see you dont have a gallery), your user name still says enthusiast. And "BEST" will depend on what the use of the car is. All things being eaual on Gen 1 & 2 cars a Paxton vs. Roe(as stock vs. stock as possible) the Centifigul will make more hp and tq. i also believe and i maybe wrong that the Displacement s/c's add more weight than a centrifigul system. I dont have a problem with either system and if i end up putting a s/c on my car it will be the one that has proven itself with the least amount of hiccups and problems. Cars tuned to the ragged edge of their maximum power will lead to a very short engine life and/or lots of time in the shop to keep it running well(i would much rather drive my car on the street and road course than to and from the shop)

 

[Steve 00RT/10]

Ok Black Mambaa1 do you really have a Viper? (post some pics i see you dont have a gallery), your user name still says enthusiast. And "BEST" will depend on what the use of the car is. All things being eaual on Gen 1 & 2 cars a Paxton vs. Roe(as stock vs. stock as possible) the Centifigul will make more hp and tq. i also believe and i maybe wrong that the Displacement s/c's add more weight than a centrifigul system. I dont have a problem with either system and if i end up putting a s/c on my car it will be the one that has proven itself with the least amount of hiccups and problems. Cars tuned to the ragged edge of their maximum power will lead to a very short engine life and/or lots of time in the shop to keep it running well(i would much rather drive my car on the street and road course than to and from the shop)

As a point of reference for low end grunt, I was able to run Gingerman last year all the way around in 4th gear. There was not one corner I couldn't break the back end loose tracking out. ...Kept the RPMs down and didn't have to worry about getting big eyed at the end of the back/front straights and down shifting too. Am I leaving a little time on the table -- probably. No big deal to me. I had just as much fun!. One or two track events a year will never a race car driver make.

As for weight, I think the net gain for the Roe was about 80 pounds--most of it sitting behind the axle.

You might want to check again with the 'participants', but last year, Dave's Gen I 5 pound Roe (untuned) hung in pretty good (from what I'm told) with GR8 ASPs big ol' Paxton --at least for a few seconds, which means maybe 40-90+? Each car was in 3rd gear I think. I'm sure Ron will correct me on the event My point being that for many street 'explosions,' the lower HP Roe will hang in there with the higher HP Paxton during the event. Most street races are over long before the Paxton gets to wind up. With a Roe, there's also really no need to shift much above 5,000 RPM (GEN II)which will contribute to longer engine life. I put 9,000 miles on ours last year.

It sounds like the new GEN III Roe kit will be a great addition to Sean's product line.

Steve

 

[Bobpantax]

I have had an 8lb Roe on a GTS and currently have the stock Paxton on an SRTC. As JD said, the power bands are different. However, with a little practice on which gear to use when, its pretty easy to keep within the sweet zone of the Paxton. The Roe was alot of fun but the power comes in so early that first gear is sponsored by Tire Rack. With respect to the additional weight of the units, I think that it is important to rebalance the suspension after the weight is added. More torque plus more weight in the front without an adjustment may increase the probability of a rear end around event.

 

[Shelby3]

The Roe was alot of fun but the power comes in so early that first gear is sponsored by Tire Rack.

That was a good one.

 

[InjectTheVenom]

Isn't first gear sponsored by Tire Rack anyway ?

 

[GR8_ASP]

Ok Steve, I guess I will chime in.

First the powerband is not vehicle speed related but engine speed related. So if both cars have the same gearing whichever one is in their prime power band will come out of the box quicker. So start at 80 mph when I am just beginning to make good power and it is asta la vista. That is effectively what happened with Daves Roe equipped car. We started from near 60 and I was in 3rd gear. I could have gone to 2nd and been in my prime power band but left it in 3rd. And for the first 20 mph gain it was near equal. But when my boost built up it was no contest.

For me one of the more important factors is driveline strength and a desire to not upgrade components. The centrifugal supercharger creates a lower maximum torque (assuming it is driven to create similar maximum power but at a higher rpm). That means the peak torque number is lower than an equivalent peak hp displacement supercharger. So in the case of an equal peak hp Roe would be much faster. But at the same time the Roe would have a peak torque much higher and be more prone to trans/diff or halfshaft failure. Now you could then raise the boost in the Paxton to create a near equal peak torque, thus be near equal for driveline reliability. In that case the Paxton would have significantly more power and would be much faster.

That is pretty close to the result between a Roe and a Paxton. The Roe makes boost in the engine speed realm of peak volumetric efficiency, really maximizing the torque value. The Paxton though creates its boost when volumetric efficiency is dropping off and thus achieves a lower peak torque, but a higher peak hp. Between those two the Paxton would walk away from the Roe, but only if they keep the engine in the top portion of the rpm band. Compete at 3000 rpm and the Roe would win hands down as the Paxton has very little boost available at 3000 rpm.

Another condition that was mentioned above that is worth noting. The centrifugal provides minimal boost at lower rpm. That means there is much more throttle control when exiting a turn (assuming revs drop in a turn) and thus less chance for spinning the tires and losing it. Steve mentioned being able to spin the tires in 4th gear in most turns. Same day same track I only had 1 turn where I was concerned about excessive tire spin during tip-in. And that was in 3rd gear. I realize that Steve has a 3.55 and I have a stock gear. But even then his in 4th is at a lower numerical ratio. So to me a centrifugal is better for track use for those without perfect throttle control. For those with perfect throttle control it is purely area under the power curve. For the rest of us a more linear power curve is preferred.

My $0.02

 

[1TONY1]

the power bands are different. However, with a little practice on which gear to use when, its pretty easy to keep within the sweet zone of the Paxton.

Just have to learn how to use each to your advantage. Well said.

 

[Viper X]

Random thoughts:

Each of these two power adders have their benefits and disadvantages.

I have run against one Roe on the street from a roll and it was no contest but it was an unfair race to begin with. My car made much more peak hp (925 rwhp vs his at 650 rwhp and I started right in the sweet spot. Hey, he wanted to do this!).

I have not yet come up against a Roe supercharged car with similar peak hp but if I did, I'd do it with caution and would not do it from a stop.

The Roe cars seem to be better at the drags, generally, while the Paxton cars seem to be better on the road and in longer races. The Paxton cars also seem to be more driveable. The Viper seems to have more torque than is easily useable, so I'm not sure why one would develop this type of supercharger for the Viper in the first place - maybe just for the drags or those short bursts on the street. The nature of the Viper engines has changed and continues to change as well. The older cars were torque monsters while the newer ones tend to spin a bit higher. Maybe the Roe's worked better on the older cars. Not sure. Maybe they don't work as well on the newer cars. Just guessing, but perhaps that's why we haven't seen one for the Gen III's yet.

I've run my Paxton car in the 1/2 mile drags the last two years at the Silver State and won both events. I think being able to wind it to 6500 rpm while power continues to increase helps. I can get to about 172 at the top of 4th gear and still be pulling strong. Last year with less power and boost than I currently have, I got to 164 mph in the 1/2 at 6500 feet elevation without going into 5th gear. I would love to see what a Roe car would do in this event, just for fun.

I've had heat issues with my Paxton at the track. Keep in mind that mine is very highly modded and not a good example for the track. Some guys do run Paxtons very successfully at the track, just not me. As a result, my Paxton car is now a street car.

I can't imagine running a Roe car flat out on the track for very long on a hot day without melting things but I guess that some guys may do it.

What ever you choose, be careful out there.

Dan

 

[black mamba1]

No one drives a Viper to get blown away on the street by a Z06 or modded Mustang. We drive them b/c they are the baddest cars ever made, period. Having said that, it seems that the Roe has the advantage in a street brawl from red light to red light. Who cares if a car can kick ass on some road race, many cars can do that, including Porches, F430's, etc. If you get your ass kicked in a street fight whaddya gonna say? Meet me at some windy street course? Even then the Roe will outperform w/ the right tires and gearing it seems. I love all you guys input and the technical info shows how astute Viper owners are. It seems to me, however, those who have the Paxtons in Gen 3 cars have them and are defending them b/c thats all thats available for Gen 3 right now. Even though several of you also have them on Gen 1 and 2. From what I have read so far, I will wait on Sean's Gen 3 charger which hopefully will be avaiable in a couple of months.

 

[SylvanSRT]

So where are the pics of your viper? you going to get you name changed from Enthusiast to owner?

 

[black mamba1]

So where are the pics of your viper? you going to get you name changed from Enthusiast to owner?

I am guilty of simply joining VCA and this site and not reading and learning how to upload pics or change my name from Enthusiast to Owner. I didnt even know what the difference was until you mentioned it. I was on the site last night trying to figure out how to make the change to Owner but didnt get very far. I am going to call the site guys today so they can walk me thru it. Can you help me w/ this? BTW, your silver Viper is totally gorgeous! I will upload some pics of my Black Beauty in a couple of days since we will have some nice weather.

 

[InjectTheVenom]

www.imageshack.us gets them uploaded instantly.

 

[SylvanSRT]

send a PM or email to one of the moderators and they will handle the change for you. thanks for the compliment

 

[zorroespanol]

No one drives a Viper to get blown away on the street by a Z06 or modded Mustang. We drive them b/c they are the baddest cars ever made, period. Having said that, it seems that the Roe has the advantage in a street brawl from red light to red light. Who cares if a car can kick ass on some road race, many cars can do that, including Porches, F430's, etc. If you get your ass kicked in a street fight whaddya gonna say? Meet me at some windy street course? Even then the Roe will outperform w/ the right tires and gearing it seems. I love all you guys input and the technical info shows how astute Viper owners are. It seems to me, however, those who have the Paxtons in Gen 3 cars have them and are defending them b/c thats all thats available for Gen 3 right now. Even though several of you also have them on Gen 1 and 2. From what I have read so far, I will wait on Sean's Gen 3 charger which hopefully will be avaiable in a couple of months.

Well if that's your mentality just slap on some slicks, skinnies up front and very loose suspension....??? Then you'll win pretty much every drag out there.

Most of us want a sports car, not a dragster.

 

[Steve 00RT/10]

Hey Ron,

First of all--it is fact that your car is faster overall than ours. You're starting stock with 50 more HP than me and 85 more HP than Dave. I'm not arguing that at all--although for the heck of it this summer some time, I'd like to do a couple of comparisons side by sides just for grins.

Ok Steve, I guess I will chime in.

First the powerband is not vehicle speed related but engine speed related. So if both cars have the same gearing whichever one is in their prime power band will come out of the box quicker. So start at 80 mph when I am just beginning to make good power and it is asta la vista. That is effectively what happened with Daves Roe equipped car. We started from near 60 and I was in 3rd gear. I could have gone to 2nd and been in my prime power band but left it in 3rd. And for the first 20 mph gain it was near equal. But when my boost built up it was no contest.

I should have said engine speed -- exactly right. I'm guessing most races aren't going to start at 80. Dave could have gone to 2nd as well. 50 MPH is not really the sweet spot in 3rd gear for a 3:07 rear end in his car either.

For me one of the more important factors is driveline strength and a desire to not upgrade components. The centrifugal supercharger creates a lower maximum torque (assuming it is driven to create similar maximum power but at a higher rpm). That means the peak torque number is lower than an equivalent peak hp displacement supercharger. So in the case of an equal peak hp Roe would be much faster. But at the same time the Roe would have a peak torque much higher and be more prone to trans/diff or halfshaft failure. Now you could then raise the boost in the Paxton to create a near equal peak torque, thus be near equal for driveline reliability. In that case the Paxton would have significantly more power and would be much faster.

No component upgrades here

That is pretty close to the result between a Roe and a Paxton. The Roe makes boost in the engine speed realm of peak volumetric efficiency, really maximizing the torque value. The Paxton though creates its boost when volumetric efficiency is dropping off and thus achieves a lower peak torque, but a higher peak hp. Between those two the Paxton would walk away from the Roe, but only if they keep the engine in the top portion of the rpm band. Compete at 3000 rpm and the Roe would win hands down as the Paxton has very little boost available at 3000 rpm.

That's exactly my point. Longer engine life through reduced RPMs and still getting a big kick in the pants down low. 'Engine component upgrade' less likely to occur

Another condition that was mentioned above that is worth noting. The centrifugal provides minimal boost at lower rpm. That means there is much more throttle control when exiting a turn (assuming revs drop in a turn) and thus less chance for spinning the tires and losing it. Steve mentioned being able to spin the tires in 4th gear in most turns. Same day same track I only had 1 turn where I was concerned about excessive tire spin during tip-in. And that was in 3rd gear. I realize that Steve has a 3.55 and I have a stock gear. But even then his in 4th is at a lower numerical ratio. So to me a centrifugal is better for track use for those without perfect throttle control. For those with perfect throttle control it is purely area under the power curve. For the rest of us a more linear power curve is preferred.

3:45 gear, but that was flooring it too early coming out. It was my first time with a SC on board so I was experimenting a little. It's not like there was instant tire spin with less than full throttle. Fairly easy to control I think in the future. (knock on wood)


Viper X

I can't imagine running a Roe car flat out on the track for very long on a hot day without melting things but I guess that some guys may do it.

I only have 1 track event so far with the Roe. If I remember right, it was low to mid 70s. Ron might remember better--he's younger The car never cracked a sweat.........at all. 2 needle widths above the 3rd hash is as hot as it got. Cooled down immediately. I logged about 80 track miles that day. I consider that a pretty good session.

Besides not wanting to run my engine at high RPM to develop the big power, to my knowledge there is not a DIY GEN II Paxton kit out there for a novice to install and tune. It must be done by a tuner well versed in such things. The closest one to here would probably be Chicago--400 miles. For the driving we do -- long trips -- all over the place, our self installed and tuned Roe is perfect. Big power, down low, where as I said up higher, most 'street explosions' occur and are over in a few seconds at usually under 100 MPH.

Steve

 

[black mamba1]

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"Well if that's your mentality just slap on some slicks, skinnies up front and very loose suspension....??? Then you'll win pretty much every drag out there.

Most of us want a sports car, not a dragster."

In response to this, sports cars in my opinion should be able to take advantage of the power over most of the powerband, not just in the upper echelons of the rpm band where most contests are already over. It reminds me of a prize fighter, a guy who can beat a guy in the first two rounds has the advantage over a guy that only wins in a 10 round fight. o.k., so the analogy is a little querky but you get my point. You dont have to make a sports car a pure dragster to make it one of the most feared cars on the road, which is what Vipers are. I am just favoring the setup most likely to hold up the Viper reputation.

 

[GR8_ASP]

Guys, something is wrong here with some comments. Above about 40 mph both can keep their engines in their repective power bands. Below 40 it does not matter as either have more than enough torque to spin the tires. That said I do not understand the street issue. The driver just has to pick the correct gear. And shift at the appropriate points.

As to producing power at a higher speed causing more engine damage, or potential damage I am not clear on a direct cause/effect. If the power is the same you have lower combustion loads, lower torque, and increased frequency for the higher peak power speed engine. The only factors I am aware of that are impacted are tensile forces due to inertia and things like valvetrain loads. Not an absolute at all. Does a Honda have a shorter life than a toyota (ha kept 2 **** for comparison) just because of higher engine speeds? Properly optimized they are fairly comparable but the Honda is lighter because it does not have to deal with the high driveline torque.

Steve, if you raise the Roe boost up to equal the Paxton peak power number you will be needing new/stronger driveline components. Because your peak torque will be much higher. And I am not sure I started with 50 more hp than you. I did not have headers, etc or lightened flywheel and lower gear either. Yours before sc was probably close to a stock SRT if not quicker.

 

[Steve 00RT/10]

Steve, if you raise the Roe boost up to equal the Paxton peak power number you will be needing new/stronger driveline components. Because your peak torque will be much higher. And I am not sure I started with 50 more hp than you. I did not have headers, etc or lightened flywheel and lower gear either. Yours before sc was probably close to a stock SRT if not quicker.

OK, OK I left a couple little things out I'm not sure I could ever get to the peak HP number, but new components would definitely be in order. I'm quite happy where I'm at....just need to add a little more air in there...in a couple weeks. ...Being newly retired gives me a little more time to play around in here. You'll have to keep your eye on me.

As for the higher engine RPMs / potential risk for damage, I'm basing that on conversations with Sean for my GEN II car. I think he said the stock valve train does not hold up well under continual high RPMs. Seeing as we drive about 10K miles per year, keeping the RPMs lower can't be bad for longevity.

Steve