Many know that the 2006 Shelby GT-H received a horsepower boost over the standard Mustang GT. The bump was the product of a cold air kit along with unique engine calibration. Those changes also necessitated that the GT-H would require premium fuel.
By July 2006 (the first 20 GT-H models were produced the week of 4/17-4/21) Hertz started reporting to Ford Racing that the GT-H was experiencing limited engine issues.
Ford Racing determined that the GT-H was suffering from "excessive rental abuse and octane lower (fuel) than that required."
By late August 2006, Ford Racing explained to Hertz that it wasn't reasonable that customers would use premium fuel, let alone return their rented GT-H fuel tanks full with premium fuel.
Ford Racing concluded that the best course of action was to quarantine each GT-H in the wild and install a new engine calibration, which would allow the GT-H to run on regular fuel. The only drawback was that the Shelby GT-H would now produce less horsepower than originally desired.
So there's a unique piece of unwritten Shelby GT-H history
Very cool bit of info.
So unless the post-Hertz owner of a 2006 GT-H recalibrates the engine, it has less HP than the 07-08?
I'm surprised the ECU didn't compensate enough for lower fuel grade.
I wonder if there is a back story that the recalibration wasn't certified by the EPA.
More back up
Under that bulging hood is an internally stock 4.6-liter, SOHC three-valve V-8 treated to a Ford Racing Power Pack, which kicks the horsepower rating from 300 to 325.
Torque increases by 10 pound-feet.
The package (FR1 in the Ford Racing catalog) consists of a 90mm cold-air intake, freer-flowing (read: louder) mufflers, and a reflash of the engine-management system for a more aggressive timing curve.
Premium fuel is now required. The exhaust's standard H-pipe crossover is swapped for a less restrictive X-pipe.
2006 Ford Mustang Shelby GT-H - Road Test - Motor Trend
https://www.motortrend.com/reviews/2006-ford-mustang-shelby-gt-h
Quote from: FL SAAC on January 14, 2026, 02:34:18 PMMore back up
Under that bulging hood is an internally stock 4.6-liter, SOHC three-valve V-8 treated to a Ford Racing Power Pack, which kicks the horsepower rating from 300 to 325.
Torque increases by 10 pound-feet.
I have a 2006 Saleen S281 with the 4.6 3-valve that they tweaked with a tune, pullies, exhaust, CAI, etc. I have to say it is the least impressive V8 Mustang I have ever driven. They are gutless. It's an awesome car to drive, handling is exceptional, ride is super, massive brakes and looks amazing. But HP leaves a lot to be desired.
Quote from: jimhyc on January 14, 2026, 03:28:57 PMUnder that bulging hood is an internally stock 4.6-liter, SOHC three-valve V-8 treated to a Ford Racing Power Pack,
I have a 2006 Saleen S281 with the 4.6 3-valve that they tweaked with a tune, pullies, exhaust, CAI, etc. I have to say it is the least impressive V8 Mustang I have ever driven. They are gutless. It's an awesome car to drive, handling is exceptional, ride is super, massive brakes and looks amazing. But HP leaves a lot to be desired. [/quote]
The EPA cracked down on mods before the car was sold to the first owner. They even seized some Saleen cars off dealer floors. Now only "upgrades" will keep the car withing the EPA certification that the manufacturer had approved. IE the Motorsport kits. Post title is a different animal. Once you own the car you can do whatever you want to it. While it's still a federal crime to mess with stuff that can affect emissions they let the states handle it.
In 2011 I travelled to SFO to work on a customer's airplane. I reserved a midsize Hertz car at the airport. When I got there the lot was empty except a Shelby GT-H convertible. The Hertz attendant rented me that convertible.
It was down on power. I drove it to Oakland and used it for 3 days. It was pretty sharp looking but it did not have a whole bunch of power. I topped off the gas tank with premium when I returned it.
Quote from: 98SVT - was 06GT on January 14, 2026, 04:22:23 PMQuote from: jimhyc on January 14, 2026, 03:28:57 PMI have a 2006 Saleen S281 with the 4.6 3-valve that they tweaked with a tune, pullies, exhaust, CAI, etc. I have to say it is the least impressive V8 Mustang I have ever driven. They are gutless. It's an awesome car to drive, handling is exceptional, ride is super, massive brakes and looks amazing. But HP leaves a lot to be desired.
The EPA cracked down on mods before the car was sold to the first owner. They even seized some Saleen cars off dealer floors. Now only "upgrades" will keep the car withing the EPA certification that the manufacturer had approved. IE the Motorsport kits. Post title is a different animal. Once you own the car you can do whatever you want to it. While it's still a federal crime to mess with stuff that can affect emissions they let the states handle it.
You are correct stating that the 4.6 3 valve is kind of limited.
On our 2007 GTH convertible we decided to concentrate on the suspension.
The car handles super solid on the track corners and has literally no wheel hop or spin (thank you Steeda) in the 1/4. We kind of have the best of both worlds here.
Cars engine is still stock N.A. running a consistent 12.8 at the 1/4 and trap speed ranges from 103-106 mph.
Cant ask for more considering its bulk, with all of its creature comforts and accessories still operable.
Go Black and Gold!
Quote from: Royce Peterson on January 15, 2026, 08:24:51 AM......I reserved a midsize Hertz car at the airport. When I got there the lot was empty except a Shelby GT-H convertible. The Hertz attendant rented me that convertible.
My dad had to travel on occasion for work and being 16 with a new drivers license I always volunteered to drive him to LAX. We passed the Hertz store and out front were always a row of Gt350H cars. I begged him to rent one for a weekend and even offered to pay for it - to no avail. I was never able to talk him into staying at the Wigwam motel when I was younger either. Man those aerospace engineers were cheap......
https://sleepinawigwam.com/
Quote from: jimhyc on January 14, 2026, 03:28:57 PMQuote from: FL SAAC on January 14, 2026, 02:34:18 PMMore back up
Under that bulging hood is an internally stock 4.6-liter, SOHC three-valve V-8 treated to a Ford Racing Power Pack, which kicks the horsepower rating from 300 to 325.
Torque increases by 10 pound-feet.
I have a 2006 Saleen S281 with the 4.6 3-valve that they tweaked with a tune, pullies, exhaust, CAI, etc. I have to say it is the least impressive V8 Mustang I have ever driven. They are gutless. It's an awesome car to drive, handling is exceptional, ride is super, massive brakes and looks amazing. But HP leaves a lot to be desired.
Here is another avenue you may consider (we did, but didnt) for additional power to your 4.6
"The interesting journey of the Shelby Hertz # 06H0055"
https://www.saac.com/forum/index.php?topic=7685.0