Interesting article in the August issue of Hot Rod. Take a stroked 327 ci SBF with common aftermarket parts, and compare the performance of the engine with commonly available Centrifugal (Paxton Novi 1200), Turbo (HP Performance T62-1), and Roots (Holley 174) supercharger kits. Boost was limited to 9.5psi, non-intercooled. -------------------------Baseline------Centrifugal------Turbo--------Roots Peak HP-------392@6000------617@6000----600@6000--535@6000 Peak TQ-------386@5200------561@5200----617@4200--513@4600 Min Boost--------------------------1.7@2500-----5.7@2500--4.8@2500 Max Boost-------------------------9.5@6000-----9.5@5100--8.0@6000 Ave HP(2500-6000rpm)-310-------------412------------460---------394 Ave TQ(2500-6000rpm)-365-------------494------------564---------483 Ave HP(4000-6000rpm)-352-------------518------------555---------472 Ave TQ(4000-6000rpm)-371-------------542------------585---------497 TQ@2500------------------------------------360------------490---------440 TQ@3000------------------340-------------405------------500---------450 TQ@3500------------------355-------------450------------560---------475 TQ@4000------------------365-------------500------------610---------500 TQ@4500------------------380-------------525------------610---------505 TQ@5000------------------375-------------555------------600---------505 TQ@5500------------------355-------------555------------560---------485 TQ@6000------------------354-------------540------------530---------475 HP@2500------------------------------------170------------235---------210 HP@3000------------------190-------------235------------290---------250 HP@3500------------------240-------------300------------375---------325 HP@4000------------------275-------------375------------455---------375 HP@4500------------------325-------------450------------525---------445 HP@5000------------------360-------------525------------575---------485 HP@5500------------------380-------------575------------600---------510 HP@6000------------------395-------------617------------600---------535

turbo = win

August Hot Rod you say? ON MY WAY TO "DA STOE" NOW!

Here, this is a bit more readable.
-------------------------Baseline------Centrifugal------Turbo--------Roots
Peak HP------------------392@6000------617@6000---------600@6000-----535@6000
Peak TQ------------------386@5200------561@5200---------617@4200-----513@4600
Min Boost----------------1.7@2500------5.7@2500---------4.8@2500
Max Boost----------------9.5@6000------9.5@5100---------8.0@6000
Ave HP(2500-6000rpm)-----310-------------412------------460---------394
Ave TQ(2500-6000rpm)-----365-------------494------------564---------483
Ave HP(4000-6000rpm)-----352-------------518------------555---------472
Ave TQ(4000-6000rpm)-----371-------------542------------585---------497

TQ@2500----------------------------------360------------490---------440
TQ@3000------------------340-------------405------------500---------450
TQ@3500------------------355-------------450------------560---------475
TQ@4000------------------365-------------500------------610---------500
TQ@4500------------------380-------------525------------610---------505
TQ@5000------------------375-------------555------------600---------505
TQ@5500------------------355-------------555------------560---------485
TQ@6000------------------354-------------540------------530---------475

HP@2500----------------------------------170------------235---------210
HP@3000------------------190-------------235------------290---------250
HP@3500------------------240-------------300------------375---------325
HP@4000------------------275-------------375------------455---------375
HP@4500------------------325-------------450------------525---------445
HP@5000------------------360-------------525------------575---------485
HP@5500------------------380-------------575------------600---------510
HP@6000------------------395-------------617------------600---------535

Wow, so it looks like the centrifugal, and the turbo cars achieved the best overall gains and the turbo won the torque contest overall.

I'd be interested in the numbers if all three were limited to 8 lbs, or if the roots was uped to 9.5 lb. Seems a little off balanced. BW

Article was very interesting. Here is a pic of the TQ-Curve Differences.

Edit*pic was really big. Here is a link to it in its massive size
http://webpages.charter.net/snavely/100_0086.JPG

Brian

wow the turdo really punched up the middle

Id like to see a identical graph overlay showing A/F ratio

B4Ctom1 plans his assault of the streets with JYD 3.0, with a powerstroke turbo on some poor smallblock...

i was over @ monty's house today and we were talking about this but i didn't know they were using a HP turbo

i dont think this was a well done test, they should've used a well known garrett 62-1

the turbo they use is a Holset turbo with a GIANT compressor cover which helps the smaller wheel in it make a lot of horsepower

jmo though

Since I dont know anything about turbos. What are you saying? That they used too good of a turbo for this test? If so, that sucks.

Brian

ok, i'll try and explain. Most turbos are made by garrett and/or modified by other turbo places and call them fancy names

a normal 62-1 turbo would have a T04S cover with a 4" inlet and probably a 2.5-3" outlet on it. It's a common turbo and a base one

Holset Turbos are based out of england, they are used on big diesal and on dodge cummins turbo motors. They are becoming popular with the turbocharging crowd. HP Performance is using Holset turbos (with GREAT success might i add the #s they are making with their mustang kits are nuts) with similarly sized compressor wheels and they they are just modifying a garrett exhaust housing for use with the turbo so it makes mounting an exhaust easier.

The thing about those turbos is that the compressor housing which covers the wheel, is MUCH larger in size than a comparably sized garrett cover and it is allowing for less turbulence inside and thus creating better power.

i'm not saying this wasn't a fair test, im just saying that the average person playing with turbos is probably not using a Holset turbo

jim

ps i haven't looked at the magazine yet and i am not 100% sure they used a Holset turbo BUT that is primarily what they use and that is why i have been talking about it. If they used a garrett turbo, i apologize

Sweet, thanks for explaining that in such detail. If nobody else checks it before me, I will check the add and post which turbo they used.

Brian

What s/c did they use? I see it mentioned as a Paxton, please tell me it wasn't a SN series!

speaking of this, have you seen ebay lately? The prices on good used Holset and powerstroke turbos went from $300 to $600 almost overnight!

Paxton Novi 1200

How does that Roots blower compare to a 6-71 or 8-71?

http://www.holley.com/HiOctn/ProdLin...ro-Street.html

http://www.holley.com/HiOctn/ProdLin...-71_14-71.html

:lala:

not even close.

what kind of numbers would a 6-71 put out with the same amount of boost as that roots blower?

As the 6-71 is a ROOTS type blower it would put out similar numbers with similar boost.

Having some expereince with the smaller Weiand (Holley) 142 blower the curve for the roots looks about right. My experience is that the smaller 142 is basically "all done" at about 500HP. It just can't move enough air to go much higher. The 174, by pure extrapolation should be maxed out at about 600HP. And I'm talking about putting it on larger 350-383ci engines. Street engines, with modest cams and commonly available heads. On a smaller 320-330ci motor you're gonna have an even tougher time hitting those same HP levels.

Another thing I've noticed is that these small roots blowers don't really make any more power above about 5-6 PSI or so. Seems all the extra spinning gets transferred mostly into just beating up and heating up the air. A larger 6-71 blower would probably do better in the upper RPMs since it can not only build the boost but can also flow a lot more air at that boost level as well.

Still, for a total investment of $1500 and a single afternoon of wrenching to install one, it's still a pretty nice bang/buck and definitly the cheapest way to go if you just can't live without a boosted motor.

I know it is a roots blower, but they are also bigger, and B4CTOM1 pretty much said that 142 isn't even in the same league as a 6-71 and 8-71.

Yes,a 6-71 or 8-71 can make a lot more power than that.
Using that same engine and the same boost, they will make about the same hp. They might make a little bit more at max RPM if the 142 is reaching its air-flow limit but they would still not be able to match a centrifugal supercharger or the turbo.

ok thanks.

I think that it goes w/o saying that they picked WAY to small a roots blower for the test. they should have used a 6-71. that would have made the roots look a little better.

I also think that they picked a bit too small a Centrifugal, but I dont know that even with a slightly larger one, that it would have kept up with the turbo.

FWIW, It was a nice test I thought.

BW

somone left out the fact that the entire test was un-intercooled.

can you imagine the differences between the roots and turbo with a nice intercooler?

as for the 142 i agree with damon @ 500 horsepower.... "danger mouse" made 600 horsepower @ 6500~rpm with a weiand 177 roots blower though.

also im wondering its a stroked 327... im guessing it was a 302?
I wonder how much faster a bigger cube motor would have moved that turbo from the extra exhaust gasses?

No they didn't.

Don't forget, this is on an engine dyno. The engine is heavily loaded and taken through the rpm range slower than it would in a car. The result is more turbo boost, and the writers mentioned that. A dragstrip comparison would not demonstrate as large an advantage for the turbocharger.

<b>No they didn't.
</b>

I didnt mean THEY left out, i mean WE left out. no one mentioned that those thing werent intercooled. thats how i knew they werent intercooled, because i read that part.

I meant WE are overlooking that fact that even though the turbo outran the roots, it the gains with an intercooled would be insane. Who sets up an expensive custom turbo application and doesnt intercool? i wouldnt.

Well it says in the article in HR that the inlet temperature was only 190 degrees so an intercooler wasn't mandatory. The centrifugal could be intercooled also.

Well a paxton novi 1200 is not worth a crap to start with...If thats what they really used then the test was a wash...You could just about show a chart proving some 1.6 rocker arms are better performing than a nOVI1200...LOL

X-Paxton Owner
KENWOOD
Vortech supercharged BES 383

Well. Forget about what brand and exact type they used in the test.

They compared a turbo, a centifugal superhcarger and a roots type supercharger to the same NA engine. And they did not use any intercoolers. They used slightley more boost on the roots type blower.

Given these facts I think the graph shows EXACTLY what should be expected.

NA as baseline.

Roots lifts the curve about the same percentage over the whole range.

The turbo is boost controlled. When spooled up it will also lift the curve a fixed percentage until it starts to run out of air. The curve WILL be higher than the roots because the roots makes more heat.

The centrigugal blower builds boost with rpm and that is why it is so stong in the top end. At lower rpm it will produce less boost.

This graph shows exactly what to expect.

I wonder how the results would've looked if they had an intercooler for that turbo

I think they should have run a S-trim , a megacharger 250, and that turbo.

The act of compressing air generates heat.
The primary difference in discharge temps from S/C to T/C is that the turbo since it shares the housing with the exhaust, and that adds a more heat to the incoming air. Depending on boost and turbo, from not much to a heck of alot.

Once you get the turbo spooled it'll track rpm about as well as a S/C engine. So if your using an automatic tranny with the right stall converter you can get the turbo up and spinning rather well.
A manual with a S/C thou will be better able at instantly roasting the tires at a given speed.

For a daily driver, the down side with the S/C is that it's always a load on the engine. Where as with a turbo at say 70 you can get it to be slightly spooled, and raising the MPG by recovering some energy from the exhaust. But, just ever so slightly.

You can agrue by brand on turbos all day, which is better. On any given application, there will always be one that is a little sweeter. But, bottom line, with an auto trannied car, the converter can help/hinder things ALOT.

Yup.... BW

Less

Im sure you know it would take far less drive ratio to turn a 6-71 at 8 psi than the little 177. The 177 is spun at an amazing overdrive ratio even at just 8 pounds. Compared to a 6-71 which on a 327 would only require a 20 percent underdrive!!!. This alone would translate to lower intake temperature and air density , and the net result would be bigger power with out a doubt. Not certain if the 177 uses two or three lobe rotors and if they are straight or helix ( a 6-71 uses three helix(twisted)) but that also translates to different effeciency and different air turbulance factors throughout the rpm range. 6-71 > 420 mega.

If the tests were run with Identical wb a/f tuning on the full map range to nullify the fuel delivery as a possible hinderance to any of the combinations , and Manifold air temperature was sustained equally then the test numbers would be much much closer to one another.

A fair test would be unlimited budget no hold barred build up unique to each power adders with no rules of component use. Then again theyd all run slow in a car not properly set up individually , so what do I care.

Its to bad the bottle wasnt in the test , evil laugh...:

In the end roots and nitromethane > all

EDIT : Just reread its a 174 holley which is a two lobe

It is a well known fact that the roots type supercharger is much less effecient than the turbo or the centrifugal supercharger. It will heat the air more and make less power if the boost is the same. A modern displacement supercharger like the Eaton or Whipple will make about the same power as the turbo or centrifugal supercharger, but with the low end tourqe of the roots.

Well, ya got the nitromethane part right,
LOL

Yea, assuming that they are measuring the boost pressure at the intake manifold, if they kept the boost pressures the same and ran an intercooler it would even out the field some. The roots would have done better (assuming that they either ran a bigger one or limited the others to whatever boost it managed to generate after the intercooler), because most roots blowers have much lower adiabatic (heat added to the air when compressing it) efficiency.

Even if they ran a newer design, like an Eaton, there they’ve managed to increase VE significantly over traditional designs, but not adiabatic efficiencies, so the results would have been similar.

What people are missing (and has been said and seemingly ignored here) is that the way the engine was loaded for the test you’d have a hard time reproducing without putting it in a heavy car with no gear. This favors the turbo since the heavier loading forces it to spool sooner then it would in a more optimized setup.

Actually, this turns out to be a 6/half dozen argument. Turbocharged engines will loose a significant amount of MPG vs a well tuned, long tube header setup because there will be little or no scavenging, resulting in lower VE’s under comparable situations. OTOH, more modern designs like the eaton positive displacement blowers are very good at part throttle/no boost conditions. With their bypass open (built into most of the eaton cases now) eaton claims something on the order of .3hp to drive it when it’s not ‘boosting,’ and the rest of that engine could still be optimized for better scavenging/ve… As it turns out, it’s probably more up to your knowledge and your patience with getting the right setup.

(BTW, Bruce, it’s good to see you here…)

i still like the turbo idea though, i have a had a paxton before and my buddy had a 6:71 440 road runner.....and some turbo cars, fact is, that paxton took a lot to turn, if it wasn't for the exhaust and the plumbing i would stuff a turbo on everything that comes in the shop...they really do work good and are easily adjusted boost levels... even after i sent the paxton back to them and got it rebuilt it was tight... so i dunno i like the turbo's and wish there were more kits for the camaro's

I see this is an old post but my .02, I went from a B&M 144 to a B&M Mega Charger 420 on the same motor and I can tell you there is a huge difference between the two of them plus I went from 15lbs. to 9lbs.

15lbs to 9lbs or 9lbs to 15lbs

15 to 9

rite:...

After running 15lbs for 4 years (aprox. 15k miles) when I went to the 6-71 I decided to make it more streetable cost wise in both fuel and parts but even at the lower boost the 6-71 has more mid and upper rpm power than the 144 did

how did you get 15lbs out of a 144

how fast were you spinning the blower?

what was the rest of your combo

makes sence going from a little s/c with more boost to a bigger with less..

would be like anything else really a little turbo with more boost or a bigger one with less.

it was on a 305 and I had over a 2:1 pulley set up on it. I had the blower on the car in mid 86 so there were not a lot of aftermarket parts available at that time but added more as they were available here is a pic from 86 with the 15lb pulley on

edit: