GM's OEM preturbo methanol injection system
12-11-11, 09:52 PM
#1
GM's OEM preturbo methanol injection system
Engine Overview
A few of you might be aware that GM went through a rather experimental phase in the early 1960s where the various divisions produced vehicles that we normally would not expect out of the company. One was the Chevrolet Corvair, a boxer-powered rear engine car that had an available turbocharged model. Another car, the one I am going to discuss here, was the Oldsmobile F-85 Jetfire, powered by a 215 gross horsepower turbocharged high compression all-aluminum 215cid (3.55 liter) V8 using preturbo methanol injection.
The engine had a 10.25:1 compression ratio and ran about 5psi peak boost. Above you can see that the turbo was mounted above the engine and the compressor outlet bolted directly to the intake manifold without an intercooler. The side-draft Rochester carburetor and methanol injection system were all integrated into a pre-turbo (draw-through) configuration:
Note that this system did not inject pure methanol: it was "turbo rocket fluid" which contained water, methanol, and some kind of corrosion inhibitor.
A few of you might be aware that GM went through a rather experimental phase in the early 1960s where the various divisions produced vehicles that we normally would not expect out of the company. One was the Chevrolet Corvair, a boxer-powered rear engine car that had an available turbocharged model. Another car, the one I am going to discuss here, was the Oldsmobile F-85 Jetfire, powered by a 215 gross horsepower turbocharged high compression all-aluminum 215cid (3.55 liter) V8 using preturbo methanol injection.
The engine had a 10.25:1 compression ratio and ran about 5psi peak boost. Above you can see that the turbo was mounted above the engine and the compressor outlet bolted directly to the intake manifold without an intercooler. The side-draft Rochester carburetor and methanol injection system were all integrated into a pre-turbo (draw-through) configuration:
Note that this system did not inject pure methanol: it was "turbo rocket fluid" which contained water, methanol, and some kind of corrosion inhibitor.
12-11-11, 09:53 PM
#2
Methanol Injection Control
Here's how the methanol is controlled. It's kind of ingenious how they managed to do everything mechanically. As you would expect of a pneumatic methanol delivery system, boost pressure flows from the carburetor ("boost pressure signal line") to the methanol tank in order provide the force needed to deliver the methanol. Methanol flows out of the bottom of the tank, through a filter and then to the "turbo rocket fluid control valve assembly." A depressurization valve and check valve keep methanol from flowing into the engine when it is not running. The control valve assembly accomplishes all methanol metering and delivery using completely mechanical means. To begin the process, valve #2 at the bottom lifts off its seat when boost pressure reaches 1psi. When valve #2 opens it allows methanol to flow to flow to valve #3. Valve #3 meters the methanol to the engine based roughly on throttle position.
Valve #3 is connected to ported vacuum from the throttle plate area. Ported vacuum predictably increases as the throttle opens. It is typically used in some emissions control systems and sometimes spark advance systems on old style distributors. So as the throttle opens, more vacuum acts on Valve #3 and this in turn increases the amount of methanol delivered to the engine. No solenoids, rpm switches, or anything electrical is used here to control the delivery.
Methanol Failsafe Systems
The Jetfire had a system to safeguard against depletion of methanol and safeguard against an overboost condition. This safeguard consisted of a butterfly valve in the intake system called the limiter valve, and a diaphragm that could pneumatically activate this valve under certain conditions. The methanol tank had a float inside. As the methanol was consumed, the float dropped and would initially activate a warning light to alert the driver. If methanol was completely consumed, the float would drop far enough that it would result in boost pressure being able to flow through the control valve assembly to the limiter diaphragm. This butterfly valve would then cause a restriction on the inlet of the turbo to protect the engine.
The turbo had a wastegate that ran at spring pressure and did not utilize what we would now consider a boost controller. In the event of boost somehow exceeding the wastegate spring pressure, a pop-off valve in the methanol tank would open to drop the methanol tank down to atmospheric pressure. Due to the design of the system this somehow ends up activating the limiter valve which creates a restriction in front of the turbo. So the limiter valve can protect the engine in the event of an overboost, a lack of methanol in the tank, or some kind of other pressure loss in the methanol delivery system.
This cheesy 60s commercial reveals the excitement of turbo rocket power (check out that sweet boost gauge at 0:58):
http://www.youtube.com/watch?v=n3Km9qlhaR0
With the Jetfire GM leaped well ahead of its time and became a pioneer in turbocharging gasoline engines for passenger cars. Supposedly the car itself was a commercial disaster and nobody knew what the hell to do with a methanol injected v8 family-ish car that ran on premium gas. Given the limited technology they had available at the time the system seems well-engineered with its failsafe system and progressive delivery.
Source: Lewis, "The Oldsmobile F-85 Jetfire Turbo Rocket Engine," 1962
Here's how the methanol is controlled. It's kind of ingenious how they managed to do everything mechanically. As you would expect of a pneumatic methanol delivery system, boost pressure flows from the carburetor ("boost pressure signal line") to the methanol tank in order provide the force needed to deliver the methanol. Methanol flows out of the bottom of the tank, through a filter and then to the "turbo rocket fluid control valve assembly." A depressurization valve and check valve keep methanol from flowing into the engine when it is not running. The control valve assembly accomplishes all methanol metering and delivery using completely mechanical means. To begin the process, valve #2 at the bottom lifts off its seat when boost pressure reaches 1psi. When valve #2 opens it allows methanol to flow to flow to valve #3. Valve #3 meters the methanol to the engine based roughly on throttle position.
Valve #3 is connected to ported vacuum from the throttle plate area. Ported vacuum predictably increases as the throttle opens. It is typically used in some emissions control systems and sometimes spark advance systems on old style distributors. So as the throttle opens, more vacuum acts on Valve #3 and this in turn increases the amount of methanol delivered to the engine. No solenoids, rpm switches, or anything electrical is used here to control the delivery.
Methanol Failsafe Systems
The Jetfire had a system to safeguard against depletion of methanol and safeguard against an overboost condition. This safeguard consisted of a butterfly valve in the intake system called the limiter valve, and a diaphragm that could pneumatically activate this valve under certain conditions. The methanol tank had a float inside. As the methanol was consumed, the float dropped and would initially activate a warning light to alert the driver. If methanol was completely consumed, the float would drop far enough that it would result in boost pressure being able to flow through the control valve assembly to the limiter diaphragm. This butterfly valve would then cause a restriction on the inlet of the turbo to protect the engine.
The turbo had a wastegate that ran at spring pressure and did not utilize what we would now consider a boost controller. In the event of boost somehow exceeding the wastegate spring pressure, a pop-off valve in the methanol tank would open to drop the methanol tank down to atmospheric pressure. Due to the design of the system this somehow ends up activating the limiter valve which creates a restriction in front of the turbo. So the limiter valve can protect the engine in the event of an overboost, a lack of methanol in the tank, or some kind of other pressure loss in the methanol delivery system.
This cheesy 60s commercial reveals the excitement of turbo rocket power (check out that sweet boost gauge at 0:58):
http://www.youtube.com/watch?v=n3Km9qlhaR0
With the Jetfire GM leaped well ahead of its time and became a pioneer in turbocharging gasoline engines for passenger cars. Supposedly the car itself was a commercial disaster and nobody knew what the hell to do with a methanol injected v8 family-ish car that ran on premium gas. Given the limited technology they had available at the time the system seems well-engineered with its failsafe system and progressive delivery.
Source: Lewis, "The Oldsmobile F-85 Jetfire Turbo Rocket Engine," 1962
12-12-11, 01:33 PM
#5
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the corvair was no slouch either, got 30lbs on the manifold and 3 charcoaled pistons at 14000 feet in 72 with what we would refer to as a hybred turbo. Sure wish that I had today's knowledge back then.
12-12-11, 03:54 PM
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wow that system is a trip!
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12-12-11, 05:48 PM
#8
talking head
the corvair was no slouch either
and that point there is one of the tragedies of automotive history
12-12-11, 06:41 PM
#9
A rotary would have to wait until the NSU Wankel Spyder, which was a peripheral ported 1 rotor mid-engine design. It never made it into a GM product and GM killed the program in the 1970s.
I've got a bunch of info on the Corvair's boxer engine here. It didn't use methanol injection. It did have a boost-activated spark retard system though, and GM did a bunch of tests to determine the calibrate the spark retard in relation to the MBT (minimum spark advance for best torque) spark curve. The 3.8 Buick engine also had a very early electronic knock control system back in the 1970s when it was still carb'd.
If anyone wants to learn about GM's early boosted engines you can shoot me a PM. I have stuff on the F-85 Jetfire, Corvair, early Buick 3.8 coupes, and the GMC Syclone/Typhoon 4.3 engine.
I've got a bunch of info on the Corvair's boxer engine here. It didn't use methanol injection. It did have a boost-activated spark retard system though, and GM did a bunch of tests to determine the calibrate the spark retard in relation to the MBT (minimum spark advance for best torque) spark curve. The 3.8 Buick engine also had a very early electronic knock control system back in the 1970s when it was still carb'd.
If anyone wants to learn about GM's early boosted engines you can shoot me a PM. I have stuff on the F-85 Jetfire, Corvair, early Buick 3.8 coupes, and the GMC Syclone/Typhoon 4.3 engine.
12-12-11, 11:22 PM
#12
Sorry, I meant late 1970s for when the 3.8 was first introduced in boosted form. The original 3.8 turbo had a carb and was one of the first engines conceived as a downsizing concept, where less displacement/cylinders + turbo is used to improve fuel economy. Now you see that all the time.
12-13-11, 05:39 PM
#13
talking head
and is there truth in the rumour the buick guys spotted the rover alum v8 prototype in britain in mothballs and revived it with 2 cylinders lopped from the block
12-13-11, 06:38 PM
#14
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the rover alm v8 is in fact built with gm 215 tooling, as the early land cruiser 6cyl was the old chevy 216 babbit rod 6 with inserts, and the original subi boxer was based and used many parts from the old 36hp air cooled vw. everybody gotta start somewhere, the corvair has some vw heritage, but a lot of it came from lightt aircraft engine design. theives all of them.
12-15-11, 01:53 PM
#15
Rotary Enthusiast
well, it seems as tho i'm only one who ever,is still alive, that actually drove one of those things.
in 1962 i ran a speed shop in massachusetts, HI-PERFORMANCE ENGINEERING, 1958-1965.
true they were so unusual, nobody worked on them, and i did not know where to start, had the car for couple hours, changed the oil&filter, thats it!!
426 big blocks were showin up, so the little one never made a big hit, GM had some bad boys runnin round.
AH YES the good old days, young and dumb and full of stuff.
in 1962 i ran a speed shop in massachusetts, HI-PERFORMANCE ENGINEERING, 1958-1965.
true they were so unusual, nobody worked on them, and i did not know where to start, had the car for couple hours, changed the oil&filter, thats it!!
426 big blocks were showin up, so the little one never made a big hit, GM had some bad boys runnin round.
AH YES the good old days, young and dumb and full of stuff.
12-15-11, 05:47 PM
#17
Rotary Enthusiast
arghx and guys, you want to read some interesting stuff google GM Le Sabre, a concept car 50 yrs ahead of things to come.
of interest it could run on gasoline or alcohol or a mixture of both in 1951. all aluminum v8 engine, rear mount auto trans, etc.
aluminumbody, with some magnisium ,and fiberglass bits,
but to me the encredible styling is just fantastic. 1951.
for me auxiliary injection is not new or recent.
my father bought a new 1949 Cadillac sedan hi-compression V8, well on hot days while going up hills ,engine would make a tinkiling sound , like marbles in an empty coffee can(dads words not mine).
talks with the dealer ,they said GM has a fix for that, a glass jar under the hood with a hose going to the carb or something! it was a dealer installed kit.
in summer just water,in winter some alcohol antifreeze,like 50-50%.
how many you guys remember ALCOHOL ANTIFREEZE,that sure dates me!!
of interest it could run on gasoline or alcohol or a mixture of both in 1951. all aluminum v8 engine, rear mount auto trans, etc.
aluminumbody, with some magnisium ,and fiberglass bits,
but to me the encredible styling is just fantastic. 1951.
for me auxiliary injection is not new or recent.
my father bought a new 1949 Cadillac sedan hi-compression V8, well on hot days while going up hills ,engine would make a tinkiling sound , like marbles in an empty coffee can(dads words not mine).
talks with the dealer ,they said GM has a fix for that, a glass jar under the hood with a hose going to the carb or something! it was a dealer installed kit.
in summer just water,in winter some alcohol antifreeze,like 50-50%.
how many you guys remember ALCOHOL ANTIFREEZE,that sure dates me!!
01-02-12, 04:15 PM
#19
Very interesting read, I really do wish a company like GM got its hands on the rotary back then and stuck with it...talk about funding money...two car manufacturers funding research and development...GM would've probably had the rotary with alcohol injection from the factory. Some crazy what-ifs go through my head when i think about it.
01-02-12, 09:04 PM
#20
Very interesting read, I really do wish a company like GM got its hands on the rotary back then and stuck with it...talk about funding money...two car manufacturers funding research and development...GM would've probably had the rotary with alcohol injection from the factory. Some crazy what-ifs go through my head when i think about it.
