Turbo Spirit: The IMSA GTO Mustang

Lately there’s been a lot of talk about the new Ford Mustang being offered with a turbocharged four-cylinder engine, and with my own Project EcoBoost I’ve been able to experience this new kind of Mustang first-hand. But anyone with a passing knowledge of the Mustang knows this isn’t the first time America’s original pony car has been made available with turbo-boosted four-pot power from factory.

In the mid 1980s, Ford famously offered a version of the Mustang called the SVO, which featured a turbocharged 2.3-liter motor. Along with a host of other performance upgrades, the Mustang SVO had a unique personality when compared to its V8 counterparts.

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And the application of turbo four-cylinder engines in Mustangs would also expand to the race track. During our recent visit to the Rolex Motorsport Reunion at Laguna Seca I came across what’s certainly one of the most unusual Mustang race cars ever built: the 1991 Roush Racing IMSA GTO.

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Like the cars it competed against in the GTO class, this Mustang doesn’t bear a ton of resemblance to the production version – but that doesn’t make it any less exciting. To me, this thing just exudes early-1990s race car attitude.

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The bodywork is loosely based on the Fox Body Mustang of the era, but beneath the skin sits a CAD-designed tube-frame chassis built by Roush Racing with the help of Ford’s Special Vehicle Operations outfit.

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At first glance you’d expect the Mustang to be powered by a variant of Ford’s small block V8, but that’s not the case here. Powering the IMSA GTO Mustang is a 2.5-liter SOHC four-cylinder engine that shares its roots with the SVO Mustang and the Ford Pinto before it. This one’s got a dry sump, a Roush/Kinsler fuel injection system and a Garrett TO4 turbocharger, and it’s good for up to 950 horsepower and 750 pound feet of torque.

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IMSA GTO cars sit somewhere in between traditional GT cars and full-on prototypes, and this becomes quite evident when you peek inside the Mustang’s cockpit. There in the center you can see the shift lever for the the Hewland VGC 5-speed transaxle.

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And let’s not forget the center-locking mesh race wheels with massive Avon slicks at each corner.

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Piloting this machine in the IMSA GTO series was none other than NASCAR and off-road racing veteran Robby Gordon. In 1991 he drove the car to a second place in the Driver’s Championship.

In this video clip you can see Robby along with the rest of his IMSA GTO competitors in the ’91 season finale held on a makeshift course at the Del Mar Fairgrounds near San Diego. There’s some great racing here.

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The early 1990s were an extremely interesting time for American sportscar racing, and vehicles like this Mustang are a big reason why.

Stay tuned for my next spotlight from Monterey in which we’ll take a look at another IMSA GTO competitor from 1991 campaigned by a little Japanese manufacturer from Hiroshima…

Mike Garrett
Instagram: japanifornia_media
mike@speedhunters.com

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1

There's something special about IMSA GTO that (to me) no other racing series has ever delivered.
The cars are somewhere between pure tools for the job and full out artworks. The raw Engineering was mind blowing and the sounds where like music in any ears. Easily my most missed series from my childhood.

2

There's something special about IMSA GTO that (to me) no other racing series has ever delivered.
The cars are somewhere between pure tools for the job and full out artworks. The raw Engineering was mind blowing and the sounds where like music in any ears. Easily my most missed series from my childhood.

3

Is that ford pinto engine ?

4

I had always thought this was V8 powered.  Interesting to see how much success they had with a turbo 4 cylinder compared to the IMSA GTP Mustang which was a disaster in both engine and chassis.

5

Different time, different engine. The Ford Probe GTP program used the Zakspeed turbocharged Ford 1.6L Kent engine from the late 1970s Group 5 Capri car. Roush built the 2.5L in this car after developing it in the Trans-Am Merkur XR4Ti program in the mid-1980s. The Ford Probe GTP would have done better with this engine, but it wasn't available in this form in 1984.

6

I had always thought this was V8 powered.  Interesting to see how much success they had with a turbo 4 cylinder compared to the IMSA GTP Mustang which was a disaster in both engine and chassis.

7

I had always thought this was V8 powered.  Interesting to see how much success they had with a turbo 4 cylinder compared to the IMSA GTP Mustang which was a disaster in both engine and chassis.

8

j_tso I came to the comments to post the same thing.  I was into Mustangs big in the '90s and early 2000s and never knew it was a 4 cylinder.

9

1990s race cars are the best race cars. Fact.

10

1990s race cars are the best race cars. Fact.

11

1990s race cars are the best race cars. Fact.

12
Gianluca FairladyZ

These were Real badass race cars!!!!! Love this stuff!

13

QD been reading a lot about those old cars in the last years, pretty surprised just how powerful they have been even decades ago, before we had modern ECUs, with less advanced metallurgy behind it, less CAD and FEM.

14

I literally lol'd when I saw the engine. All that ridiculous power and still has the same cam cover as a Thunderbird. That's awesome. 

950 hp in 2.5 liters is ridiculous. I've heard the Lima blocks are pretty stout, but goddamn. 

I wonder how they fare in reliability to a BDT. I know they can get to nearly 900 hp but only last for about 10 minutes.

15

This is awesome but that Allard J2X in the background is SO MUCH BETTER. Sorry guys, it just is.

16
deleted_82067014_Abezzegh87

950 horsepower feom 2.5 liter sohc!
awesome, especially if you keep in mind this is a track car, not some dragster..
these things gotta last a bit

17
deleted_82067014_Abezzegh87

950 horsepower feom 2.5 liter sohc!
awesome, especially if you keep in mind this is a track car, not some dragster..
these things gotta last a bit

18

TylerHorne The 2.3 in my XR4ti weighed as much as a 5.0L v8 so i'm guessing they were already overbuilt, however there were some "motorsport" blocks with taller deck, I can't imagine this car isn't using one of those "unobtanium" castings.

19

TylerHorne The 2.3 in my XR4ti weighed as much as a 5.0L v8 so i'm guessing they were already overbuilt, however there were some "motorsport" blocks with taller deck, I can't imagine this car isn't using one of those "unobtanium" castings.

20

IMSA GTO. It's the silhouette series we want and deserve, but not the one we're getting.
TA2, however, is spiffy enough for an alternative.

21
jbfromsiliconvalley

Such a different type of car/mindset. Both are amazing for different reasons.

22

j_tso I built the Revell model kit of this and it has a V8 so Im not sure if they just through this in or if this truly is the original engine to this vehicle. Why would they make a replica model kit, totally inaccurate? Im not sure about this. Google??

23

j_tso I built the Revell model kit of this and it has a V8 so Im not sure if they just through this in or if this truly is the original engine to this vehicle. Why would they make a replica model kit, totally inaccurate? Im not sure about this. Google??

24

deleted_82067014_Abezzegh87
Sounds like perfect ingredient for Formula Drift . XD

25

milkplus 

Maybe the 4-banger is heavy , due to using cast iron block ?

26

dougbunge
Mustang SVO is 2.3-litre 4-cyl .

27

RDS milkplus 5.0 is iron block and heads.

28

RDS milkplus 5.0 is iron block and heads.

29

UWerqxTeam_MJ LeMans is as close to it as we can get :(

30

bluestreaksti 
That is surprising !
How did they managed to made iron block so light ?

31

Turbine chatter akin to WRC cars :)
Undoubtedly impressive they managed to get 950bhp and 750lb/ft out of it!

32

D1RGE UWerqxTeam_MJ Don't be so sad. LMP1, LMP2, and both GTE/GTLM classes are stompin' it lately.

33

D1RGE UWerqxTeam_MJ Don't be so sad. LMP1, LMP2, and both GTE/GTLM classes are stompin' it lately.

34

RDS bluestreaksti The later roller cam 5.0 blocks were an extremely thin casting. Rumors abound that they're only good to 450 hp or so before they're a time bomb.

35

RDS bluestreaksti The later roller cam 5.0 blocks were an extremely thin casting. Rumors abound that they're only good to 450 hp or so before they're a time bomb.

36

There is a actually a much earlier Mustang IMSA as well that came out in 1984

37

There is a actually a much earlier Mustang IMSA as well that came out in 1984

38

Storz So rad. Wish that one was still around.

39

Derelict I'll take both :)

40

j_tso There's actually another IMSA Mustang that looks similar with a V8. It's easy to mistake them until you hear it.

41

Franz Samm Agreed. Crazy to think this was 25+ years ago.

42

milkplus 
Sleeve it , then you're good for another 250hp . XD

43

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