supercharger and twin turbo comparison

[californiacuda]

I have been reading a book titled Building 4.6/5.4L Ford Horsepower on the Dyno by Richard Holdner. The book has over 185 dyno runs shown with various engine configurations and power adders. On page 161 a dyno graph is shown comparing an 03 4.6L cobra engine with the factory eaton supercharger, and then, a twin turbo configuration. On both dyno runs the boost pressure is kept the same at 11psi, The eaton starts off making much more torque and hp but at about 3750 rpm the turbo engine begins to surpass the supercharged configuration. At 6600 rpm the eaton engine produced a maximum of 572 hp, and at 6500 hp the twin turbo produced a staggering 750 hp. the torque numbers were similar with a maximum difference of 156ft-lbs.

I thought this was interesting information for GT owners. Although the cobra engine was a 4.6L and the Gt is a 5.4L, the engines are both manufactured by Ford for high performance applications and they both come with factory Eaton superchargers.

I think the most important information contained is that even though the supercharger produces considerable boost and hp, it also consumes copious amounts of energy to spin the positive displacement supercharger.

If the supercharger was removed and replaced with turbo chargers, and the same boost pressure was used, the engine would produce over 175 more horsepower with no additional strain to the motor.

I realize that there are other variables at play: the cobra eaton is a roots sc and not a more effecient screw type. the engine wias on an engine dyno using a different management system, and on and on. But I still think the premise stands; that generally, turbos can produce quite a bit more hp then superchargers because of the parasitic loss the supercharger requires to operate and compress air.

http://i27.photobucket.com/albums/c186/iattackenemy/eatonvstwinturbo.jpg

 

[BlackICE]

Accurate assessment of the tradeoffs. Note that for street, use not racing, the supercharger may be better for the reasons of no turbo lag and a flater torque curve. You have the torque down low where you are normally driving vs. having to spin up the turbos.

BlackICE

 

[Fast Freddy]

superchargers are for drag racing and turbochargers are for road racing. thats my opinion. but then you can always bend the rules a bit if you have too, so.......

 

[SLF360]

superchargers are for drag racing and turbochargers are for road racing. thats my opinion. but then you can always bend the rules a bit if you have too, so.......

Try to go a hilly winding road uphill, you'll see the difference with the turbos being real hard to handle properly, vs comfort, comfort with the SC's!

 

[Mod Friendly]

Lol time and time again weve had that discussion here with Cobra owners. Boost from a turbo will always make more hp with less work on the 32v ford motor. Ive got one cobra here rigth now in the shop that has the 2.4l KB charger on it with a custom return style fuel setup and a list of other misc items but its only good for about 700-750 rwhp, but if the same engine setup was used on a twin turbo cobra it would be nearly 1300-1500 hp at the same 26 psi. The SC takes entirely to much power to just get moving as opposed to the turbo that will spool up less effortlessly. Now with the GT having higher flowing heads than the cobra and it being a 5.4L block it will have more air flowing through it to spool up the turbos faster. It will basically be one rather uncontrollable GT if it were to be twin turbo with gobs of power to spare.

 

[Fast Freddy]

Try to go a hilly winding road uphill, you'll see the difference with the turbos being real hard to handle properly, vs comfort, comfort with the SC's!

tell me of one professional ROAD RACING organization in the world that use superchargers. i am not aware of any and that is because there is a reason for that. fomula 1 has used turbos for many years in the past and never superchargers. CART and pre-cart indy cars have been using turbos for 30 years now. imsa cars at lemans, etc have classes for turbos for 30+ years as well. i don't see any superchargers at lemans.

the only place i see superchargers are on the dragstrip. the fastest cars in the 1/4 mile in the world use superchargers, that bein NHRA top fuel dragsters.

so again i say "turbos are for road racing and superchargers are for drag racing". but again rules were meant to be broken, so.............

 

[ChipBeck]

Turbochargers suck!

All of the posts here are correct but other factors come into play as well. In addition to lag turbos cook, contaminate, and destroy engine oil in short order. They generate immense underhood heat that would create other problems in the GT. And for street use every time the car is shut down and the oil flow stops the residual oil sitting in the turbo is superheated and broken down. Synthetic oil helps here but does not eleminate the problem. I am an ex auto dealer who has sold hundreds of turbocharged cars and they are a warranty nightmare. When run hard turbocharged cars should be allowed to idle for several minutes before turning the engine off to allow the turbo to cool down while oil is still flowing. Customers won't (or at least don't) do that. For street use the supercharger runs cooler, doesnt kill the engine oil, responds quicker, and is far more reliable. I would have hesitated to buy a GT with turbos, I love the supercharger.

Chip Beck

 

[Mod Friendly]

Turbo timer :thumbsup will take care of that if the customer is advised on its benefits ahead of time. I use to work at a performance shop on the side and it was an easy $50 to $125 for one plus installation and it helps. But I know most people just buying the car outright dont really care. And as far as warranty goes for them, oh yea just about anything will void your warranty with turbos.

 

[CHAD]

Turbos? Blasphemy! :biggrin

 

[davefordgt]

Ford GT does not use a eaton supercharger. The factory is a whipple.

 

[californiacuda]

With slightly smaller turbos, say 60's, spool up issues would be greatly improved.

 

[satx]

Ford GT does not use a eaton supercharger. The factory is a whipple.

correction.......factory is an eaton twin-screw.

 

[analogdesigner]

It's throttle response!

In addition to the comments made, one of the real reasons for supercharging is when throttle response vs. maximum HP is of prime concern!

In drag racing (i.e. Top Fuel and Funny car), supercharging is used for throttle response AND the fact that the engine can be set to make more HP that the car can utilize. So any extra HP that a turbo could produce is simply not beneficial. Think of a sprint car on a small oval track, (if permitted) a supercharger would make more sense than a turbo due to the throttle response required for good performance (although artificial aspiration is illegal in these classes). These cars incorporate crude mechanical fuel injection (such as the original Hilborn type) although this brute-force type of system (by today's standards) will give the quickest throttle response.

Turbocharged drag racing motors have been making good progress in recent years.

I feel that for the street, a supercharger has more "sex appeal" in addition to the comment made above. Jay

 

[Fords4life351]

superchargers are for drag racing and turbochargers are for road racing. thats my opinion. but then you can always bend the rules a bit if you have too, so.......

in the recent years that i've been following the Ford Drag racing scene Turbochargers have been gaining in popularity, as of today there is a Twin Turbo 4.6L drag car(Owned by Accufab) and it runs high 6s in the quarter mile at over 200 MPH! As some stated above its all about what you want to do with the car, if you want bragging rights type of horsepower you cant go wrong with a Turbocharger, but most GT owners would most likely like the instant power afforded by the Supercharger over the Turbo(s). Having said that I'd rather go with a turbocharger setup. with the correctly sized turbos it could spool Almost as quick as an SC yet make about 100 peak HP... which is another possitive for the Supercharger over the turbo, a Supercharger like the one on the GT generally has a better tourque curve. But again the difference can be lessened with a "properly" sized Turbo. I sometimes think the best thing to do is have two, one to go "all out" and anotherone to keep stock.... or near stock :biggrin

 

[Hennessey Performance]

Turbos? Blasphemy! :biggrin

:banana :cheers :banana :cheers :banana

 

[Black2003Cobra]

Due to its higher thermal and mechanical efficiency, a turbo will make more brake power on a given amount boost than a P-D blower, hands down. Here's some data from your smaller 4.6L brother.

2.3L Whipple (Lysholm) blower data:

Turbo data:

 

[SLF360]

Nice,
but where is the comparison, to make your point!_?? :confused

 

[Black2003Cobra]

Hey SLF - to make a comparison, just look at the least-squared fit lines to the data points at any particular boost pressure for the two different cases.

For example, at 17 psi the Whipple car makes (on avg) a peak rwHP/TQ of ~600/560 whereas the turbo cars make ~710/685!

Or you could look at the slopes. The Whipple car gains (on average) ~14.7 rwHP/psi and ~18 lb-ft/psi, versus ~22.4 rwHP/psi and ~21 lb-ft/psi for the turbo car! Nice, eh? :thumbsup

 

[Black2003Cobra]

Here's another comparo of a turbo vs Eaton (Roots) on an '03 Cobra crate engine measured at as close as they (MM&FF) could get them to the same "nominal" boost pressure (~11 psi, or so). Obviously a Roots is less efficient than a twin-screw, but you get the idea.

Here's a plot showing boost pressure vs rpm. As is well known, the Roots (or twin screws) make considerably more boost down at low rpm (< ~3500), and so of course it makes more power and torque in the lower range.

Here's the power and tq curves.

Enjoy!

 

[FORDGT001]

What would be under the rear glass if it was turbo'd. I think the SC looks great under the rear glasss, I wouldn't want it any other way.