Help with Turbo or Supercharger decision.


Thugboat

GT Owner
Jan 20, 2009
851
Humble Texas
Ladies and Gents,

After recently running the 2016 GT350 at Big Bend Open Road Race I have the itch to go faster. I do not want to add all the cage etc to the GT350 to run unlimited so thought I would use my FR500. I will need at least 600 Horsepower to reach my goals. I want to use a 4.6 modular ford engine to reach this. Normally aspirated would be to much so my question is would y'all recommend a supercharger or turbocharger? I already have a block with forged internals so need to build it from there. My concern is the heat build up. West Texas is April can be from 70 - 115 degrees at race time. I know our GT's can get heat soak if you run them at high temps for long periods of time and that is the only reason I shy away from a supercharger. I will be at WOT for at least 20 minutes so that will generate quite a bit of heat. SO, What do you think???

Thugboat
 

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Fubar

Totally ****** Up
Mark II Lifetime
Le Mans 2010 Supporter
Aug 2, 2006
3,979
Dallas, TX
Man it's all trade offs for what you want. I think you could keep a supercharger cool (maybe not cool but at least out of limp mode) for 15-20 minutes but if your really worried about heat then turbos are the way to go. You will also typically get more power from turbos but you will never get rid of the lag. It's takes a really badass driver to deal with turbo boost onset coming out of turns. The best engineers in the automotive world have been fighting that lag for decades... it's not as bad as it was but its not the instant power of a supercharger either.

The more turns and off throttle times you will be expeirenceing, the more I'd stay away from turbos. The more long straight pulls, and extended high revs, the more I'd lean towards the turbo. Keep in mind, I considered the same question and went supercharger... but that was because I drive the car on the street and wanted the instant blip of torque. I'll pay dearly for that decision on 120deg track days.
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
3,840
An interesting challenge any way you look at it. Keeping 600HP cool and delivering uniform power will be tough. In terms of cooling, the TT may be a bit easier. At the risk of oversimplifying, to get 600 RWHP, a supercharged car is going to really need to making ~725HP or so - 125HP going to the SC and the remainder to there rear wheels. The TT car will only be asking the engine to make 600HP as it doesn't have to spin a blower. A TT car on a road course can be a handful, however, if it is not built/sized properly. I think the OEMs (especiailly Ford with the V6 ecoboost in the F150 and the 2.3 4cyl ecoboost in the Mustang and RS) have figured out and all but eliminated lag. BUT, you don't have these kind of resources and all the turbo kits I have seen - they haven't figured it out either. Therefore, I think the turbo could be the best way to go but it would take a LOT of iterations, tinkering, and likely a multi-season effort and MAYBE you'll get it right.

If I was in your shoes, I'd look at a fairly built motor and the smallest, and most efficient SC you can get and then add a very efficient intercooler. I think that would be your best bet and the most practical way for you to proceed.
 
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FENZO

GT Owner
Mark II Lifetime
Jul 7, 2008
1,516
Lafayette, CO
Both?
 

Thugboat

GT Owner
Jan 20, 2009
851
Humble Texas
Thanks guys,
Exactly the info I am looking for. Keep it coming. I hope to run close to 190 in the straights and average 170+. I have no illusions of winning just finishing. The last couple of years if you finished you were top three. Most of these cars are trying to do 200+ and the naturally aspirated excessive horsepower engines are giving them heck. As far as I know no one is trying to do this the way I am. Just a bucket list item.

IF I go turbo will the heat off the turbo cause any problems?

Thugboat
 

beckertb

GT Owner
Nov 29, 2006
509
Beaumont, TX
Turbo is always more efficient Larry. Sc is easier for the application. Can get 550 reliable hp out of sc setup. Easy to drive. With turbo can make more power for sure. No road race cars mine included run sc because require so much power and generate so much heat.....
 

BlackICE

GT Owner
Nov 2, 2005
1,415
SF Bay Area in California
Fubar nailed it!
 

texas mongrel

GT Owner
Mark II Lifetime
May 3, 2009
1,512
Houston Texas
Larry, when we ran the 140/168 this year, the GT stayed cool no problem. My car has 614 RWHP per its last dyno session. I'd go supercharger every time; as others have posted, you don't want an extra 200hp suddenly appearing as you exit that sweeper out of the cut.
I also think you can easily get 600+ hp out of a NA motor; if I'm getting 533 out of an iron-head, low rise, single carb 302, think how much you could make with an unlimited, no-rules motor.
Of course, if you want cheap horsepower, dump the Ford engine and stick in a Chevy!
 

RALPHIE

GT Owner
Mar 1, 2007
7,279
If you are running high speeds, the car will stay cool at the thermostat temp (or under 200°). It only overheats on tracks where you are only in 2nd and 3rd gear all the time together with hot weather.

The limp mode temperature limiter is at 242° F.
 
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twobjshelbys

GT Owner
Jul 26, 2010
5,376
Las Vegas, NV
It only overheats on tracks where you are only in 2nd and 3rd gear all the time together with hot weather.
Oh you mean like at Spring Mountain at Rally 9 ? Mine ran pretty warm but never got into the red zone.
 

RALPHIE

GT Owner
Mar 1, 2007
7,279
Oh you mean like at Spring Mountain at Rally 9 ? Mine ran pretty warm but never got into the red zone.
Well - you didn't reach the temperature limiter, did you - and it was very warm there! I hit it at Miller in Tooele, Utah, in 109° temps outside.