ya true that......

There seems to be 2 schools of thinking with turbo cams. One is the popular theory that overlap is bad and because of that, more intake duration is usually the norm

The other is more of what monty is talking about and even Mr Duttwelier agrees with obviously because my cam for my TT motor has a small amount of overlap in it.

 

There are two very different schools of thought pertaining to turbo camshafts. Both sides are proven with great results.

Maybe.. just maybe.. the camshaft isn't that critical, as far as gross horsepower goes.

Hell, I'm running an old "blower" cam and my car hauls ***
I'm using the Comp Cams XE 224/236 on 114ls.

6.2X**( 1/8's first time out with a budget 355 and stock ported LT1 heads and intake with pump gas, ain't bad.


**1/8 mile times are calc'd from a 600' foot track where I ran a 5.91.

 

Well, there aren't 2 schools of thought, the reason why some people recommend overlap is the combo. when you get up in the A/R ratio and turbo size, the boost to exhaust pressure ratio is at or near 1:1, you can get closer and closer to a NA style cam. When the pressure in the exhaust is high you have to run very little overalp. ie, small ARs and turbos.

I am running a reverse split due to i think that I am going to have a lot of exhaust pressure when running full boost. When I go to a GT80 Rtrim with a 1.32a/r, illl prolly change cams to a single pattern.

BTw, finished my turbos exhaust tonight, headers, cross over down pipe etc is all done.. weee!!

 

well if thats the case jordan, kenny's a moron cuz my gale bank turbo manifolds aren't the greatest things in the world and a header would be 300% better and i have single pattern but i gave him all my requirements and i think he gave me some overlap cuz i told him i wanted to run on pump gas most of the time and i wasn't willing to o-ring the motor. So sacrifice a little power for the ability to keep the heads on

 

not sure what kinda power you are aiming for, but there are head gasket technologies that can hold big power with out a traditional oring. anyway, more than likely he is guessin that you won't have a huge exhaust to intake pressure differential..

 

Turbo o Supercharger will be personal preference probably. Specially on the street.

Its like the battle with.. smaller engine and lighter car or bigger engine and torquier car... One can use the fact that top fuel only uses supercharger and some argue to why they only use them...

Its a PERSONAL PREFERENCE for me the SC, its not that is better, its that I like it more...

I am not really sure to which is better as I have yet to see a similar comparison between a single turbo of the same size as a supercharger...

I honestly think that the turbo doesn't get that power free as many people say.. There is Nothing like a FREE lunch... or so you guys say...

 

Of course it's not free. But it is "more free" than with a supercharger

 

That is what I would love to find out for sure and by how much...

I do think its less power loss from a turbo, but, for how much and at the expense of what?

Bigger companies are leaning towards the superchargers...

GM was one that used turbo's in an era and now its using superchargers..

Mercedes is using SC
Jaguar is also using SC
Ford uses SC

Only the japs are the ones that use Turbos and nissan is moving towards SC...

Why? easier to troubleshoot? Easier on other aspects??? Why should it be easier a SC to them since they were the ones who perfected the art of using turbos...

Just a thought...

 

Again, it is a compromise with the big companies. The cost of tooling up to make the headers, crossovers, downpipes, boost control systems (wastegates, solenoids, PCM programming time, etc.) all outweighs the costs of their percieved performance vs. cost benefits. They can do it cheaper with the SC route. Especially since they're building cars for the masses. Think about it: if they can make a car pull (some) horsepower using a SC at about $1000 less per unit than with using a turbo set up, after making 50,000 cars they saved $50 million dollars. And thats not considering all the initial investments need to produce them.

The stage 2 buicks are prime testaments to turbos: 4.5L V6s making well in excess of 1600 hp and they're making more with every passing day. The most powerful SC'c V6 I've seen so far was a 1000hp 4.3 chevy.

Under equal circumstances a turbo will produce more power simply due to the fact that the crank's rotational force isn't being used up while turning a SC's compressor. Baxter was making about 1,100 hp with a SC, but I'll put money on it that the SC was consuming at or near 200hp. That's why I'm thinking that 1300 turbocharged horses are possible on a LT1 (especially considering the fact that turbos are much more forgiving on the rotating assy). It has been shown that for every 100hp you get out of a SC setup, anywhere from 20-30 is being used to turn the SC. The math is rough, but the concept has certainly been proven.

Talking potential, turbocharging is where it's at ---> relatively unlimited boost. Something was metioned earlier about the big guys using SCs in pro dragracing; that's because turbos were banned in the pros. They're making 5-6000hp with near 50#s of boost right now and with turbos how much boost do you think they'll be making? 70? 100? The traction technology simply can't contain that much power right now.

Like I said earlier, it's a compromise only the buyer can make. The depths of your pocket determines how fast you can go. If a SC will help you reach your goals, then go for it. But sooner or later you will end up going the turbo route b/c it will be much easier to attain higher hp numbers.

 

In addition to what Fast Caddie mentioned, one of the primary reasons why factory turbo cars are less common these days is emissions standards. Particularly at cold start-up.

Think about it. Throw in a massive hunk of metal, such as a turbo, between the exhaust ports and cat(s), and it will suck up precious heat that would otherwise bring the catalytic converter to operating temperature in a timely manner. Cold cat = non-functioning cat = lots hydrocarbons = failing emissions standards = pissed off Feds = not being able to market a car in the U.S.

Case in point: almost if not all European manufacturers, from Renault, to Peugeout, to BMW, to Mercedes, to Audi/VW, to Saab, to Volvo, to Porsche, to Fiat, to Alfa Romeo, to Skoda all offer turbo models. Most mentioned do not ship many of their turbocharged models to the States simply due to more stringent emissions standards.

Most stateside probably haven't a clue BMW and Mercedes even offer turbo models. This includes high-performance diesel models that really scoot, yet still yeild superb gas mileage. On this side of the Atlantic, "high-performance diesel" is an oxymoron

It's not that the Japanese are the only ones still producing turbo models, but rather they seem like the only ones still exporting them to our neck of the woods. There are actually more European turbo cars in production - we just don't see them here.

In essence, OEMs opt for SC's over turbos for the same reason as many 4th gen F-Body enthusiasts: far easier and cheaper to package, not necessarily for any performance advantages. In addition, for OEM's, SC's are simpler to mass produce.

However, of all the manufacturers you mentioned - Mercedes and Jaguar/Ford - each opts for roots-style blowers, not centrifugals. Hell, Shelby's the only "manufacturer" that straps on a centrifugal from the factory, if you can even call that operation a "manufacturer." No one else runs them

Again, the popularity of roots blowers from OEM's probably revolves around packaging and costs, but also "street performance (almost instant boost)" and longevity. Roots blowers have been proven to last over 100K miles. Not too shabby. Cheap, reliable, easy to R&D, and significantly improved power where it matters most for the general consumer - down low. For an OEM, what's not to love?

This debate would be much different if comparing turbos vs. roots or screw-type blowers rather than turbos vs. centrifugals. A roots significantly closes the "area under the curve" deficit a centrifugal sacrafices to a turbo.

The Lightning and Cobra come to mind as roots-blown cars with gobs of low end torque, especially compared to a centrifugal SC. Additionally, in smaller-displacement motors, the ol' roots flat out kicks a turbo's *** in street performance.

IMHO, unless shooting for really big power, the poorer adiabatic efficiency of a roots is insignificant for the majority of street motors. Up to about 500 - 600 RWHP, I'll take a roots over a centrifugal any day of the week. Lower ultimate power potential? Yes. More "total" HP/TQ for any given "peak" HP/TQ vs. a centrifugal? You bet

Yes, the die hard centrifugal blower fans could brag about their superior efficiency, but at the power level most are at, it wouldn't matter anyway. Plus, I'd have SO much more low/mid range torque to boot

 

Actually, I am not favoring per se the centrifugal type.. I was talking about the supercharger...

I do have a supercharger because it was easier on the $...

But one question is:

If I am getting my peak torque at 4200rpm why should I need more power lower if when racing I am never lower than that?

Anyways... the supercharger used in NHRA I think its a roots type..

The other thing I would like to say... In some points and rules (dont quite remember now) they banned the use of the paxton vr4 due to its superiority for short races...

You guys are right about the european cars and turbos and not comming here.. I knew about them, I just for got about them when writting the other post...

I still think that superchargers are underated... And also centrifugal type...

I wish I could mount a novi 2000 on a camaro and see where it goes, that I bet it will go as far and even better than a YS-trim for the street, which is comparable to a T76 turbo...

I think that turbos are unlimited due to the bigger cfm rating than your average supercharger.. (s-trim, t-trim)

 

Blower for off the line & turbo for the rest

 

dont confuse "roots" and "screw" type blowers.....they aren't the same

screw types are MUCH more efficient than roots and offer the low end punch of a roots. That is what is being used on applications like the GTP and Cobra

 

We can make points for each... it's all what your goals are for the car. For most, boost using a centrifugal blower is the easiest, cheapest, and least maintenance way to go fast. For others the intricacy involved in building a tuning a proper turbo system is a task they look forward too. I mean let's admit for power, especially torque, the turbo will kick a blower *** to hell. The main idea here is area under the curve... A blower's power is gradually increasing whereas a turbo's power kicks in at full force right when you punch the gas. I mean whats better than cranking the boost up from the driver's seat.

For turbo OEM cars... man, I don't even want to start... Audi and VW for example. With a simple chip to up the boost you already have a high 12 low 13 second car in an S4. Turbo technology is going to keep getting better and better as emissions standards get more and more strict... a turbocharged car will not waste all that gas unless your foot tells the car you need it.

I actually traded my turbo technologies kit for my vortech. And although I do sometimes regret it, I think of how much money I would have to have put into the car to make it run the way I want and then I am happy again =) I mean think... FAST, T-76 upgrade, wastegate, intercooler, blowoff valve, boost controller and many other upgrades... With my car there are so many people blown that its really easy to get help with the car. Well this is long enough I'm done =)

 

Doesn't Whipple own the patent on all screw-type blowers? Consequently, if I'm not mistaken no current OEM runs screw-type blowers.

The Cobra and GTP do indeed use roots blowers.