Carb. Engines vs. EFI Engines -hp per pound
Carb. Engines vs. EFI Engines -hp per pound
(OP)
Can anyone compare Detroit RWD V6/V8 (250-300hp) engines using a Carb (usually - older pre 1985) vs EFI(post 2000) on a HP per pound comparison ? Any thoughts on the power/weight for the complete drivetrain?





RE: Carb. Engines vs. EFI Engines -hp per pound
I don't have weights but obviously the power to weight ratio improved a lot.
Now if you want to get into real power arguments you have to go back to the late 60's when the horsepower wars were raging and there were no emission or mileage regulations. Also the standard for measuring HP was different so you get all sorts of wild claims.
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RE: Carb. Engines vs. EFI Engines -hp per pound
Are you asking about a carefully-tuned example of each (carb vs. injection)? Or averages of random samples pulled from the production lines?
Real-world performance (large variety of temperatures, altitudes, air densities, fuel compositions, etc.) or controlled-conditions of a dynamometer lab?
I'm not merely nit-pickiing; the above clarifications bear directly on the answer to your question.
RE: Carb. Engines vs. EFI Engines -hp per pound
Real examples.
A typical mid 70s 5 litre (308CI) Holden V8 was advertised at 245hp and that was written in big letters on the air cleaner. They typically made about 145 corrected hp on the dyno. A "40hp" VW Beetle typically made 25hp.
A 1991 Honda D16A9 engine was advertised at 130hp. they typically made about 130 corrected hp or almost as much as the 5 litre Holden V8. I could just lift the complete with all ancillaries VW or the Honda off the ground with suitable straps and harness. I have loaded and unloaded both onto a Ute (pickup truck) on my own with no jacks or cranes. No way could I do that with a V8 that was anything more than a fully stripped bare block.
Regards
Pat
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RE: Carb. Engines vs. EFI Engines -hp per pound
Tuning is certainly a problem with a carb. I've been to many cruise nights and I've only seen a couple of old cars with the big "HP war" era engines that have actually been impressive when pulling out. From observations, my personal opinion is that most of the older carb'ed engines are unimpressive out of tune dogs.
FYI, a 2000 Corvette @ 345hp has an all aluminum LS1 engine and is not the same basic Chevy 350 small block as pre '97 Corvettes had. Automatic? I would only buy 6-speed Corvette.
RE: Carb. Engines vs. EFI Engines -hp per pound
Are we trying to compare OE advertised power or the power that's at least potentially available at some given level of modification?
Compared to the "pre-1985" range suggested, engine weights have dropped anywhere from about 50 to over 100 lbs. Think 430-ish for Ford's aluminum modular engines and GM's aluminum LS vs 500 - 575 for the older Windsors and SBCs. 460 - 475 for the 289/302 Fords.
Automatic transmissions have probably gotten slightly heavier over the same 1985 - 200? time span due at least in part to having 5 or 6 ratios instead of 3 or 4. I ran across a 25 lb weight difference claim for Ford's 5R55S vs the C4.
I guess if you buy a car to be seen in, the transmission type becomes irrelevant. Mine would be a manual too, just like every other car we've owned over the last 40 years.
Norm
RE: Carb. Engines vs. EFI Engines -hp per pound
In terms of ultimate performance on anything other than a steady state application, modern fuel injection will provide significantly more power at higher reliability, but there is always a trade-off somewhere, and system weight may be it depending on your application.
RE: Carb. Engines vs. EFI Engines -hp per pound
Fuel particle size of about 3 microns seems to be the ultimate for power production, properly mixed with the charge air. Getting this size is more difficult with low pressure injectors or poor design carburetor venturies, boosters, air emulsion, etc.
Best fuel economy comes with thoroughly mixed gaseous fuel properly mixed and with a lot of turbulence in the combustion chamber. Gaseous fuel takes much more volume than mist, so the amount of energy in a given volume of mixture is much greater with 3 micron mist.
All that being said, a perfectly calibrated carburetor currently makes better power and economy. Problem is being perfectly calibrated is almost impossible. All the sensors and programability of electronic injection makes a more efficient fuel system.
Progress in injectors and using direct injection into the combustion chamber at very high pressures to better break up the droplets and more energetic combustion chambers is closing the gap.
Point if interest: Mercedes Benz used direct port injection on it's 3 liter six in the 1950's 300SL.
RE: Carb. Engines vs. EFI Engines -hp per pound
Coupled with that the vast majority of SI engines are rather tolerant in terms of fuelling.
I'm sure that I don't need to teach grandma to suck eggs - I venture there is chuff all differences.
MS
RE: Carb. Engines vs. EFI Engines -hp per pound
Regards
Pat
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RE: Carb. Engines vs. EFI Engines -hp per pound
However, I would counter by saying that in some (not all) EFI applications the head/manifold geometries are actually compromised to allow the placement of injectors.
I'd say that, bottom line, there's not much in it!
MS
RE: Carb. Engines vs. EFI Engines -hp per pound
I would also say that carby placement mostly has as big if not more compromise on head and manifold than does injector placement, especially on V8s where a low bonnet line is also desirable.
Regards
Pat
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RE: Carb. Engines vs. EFI Engines -hp per pound
With regards to the conditions conducive to valve float, it seems logical to take the cam profile, and translate the profile into translational displacement. Integrating the displacement twice yields the "required" acceleration of the valve.
For non-floating valve motion, the "actual" valve acceleration is equal to the "required" acceleration set fourth by the cam.
At an unknown elevated engine speed, the follower will leave contact with the cam, at which point the the required valve acceleration is greater than the actual acceleration.
Perhaps it is at this inequality, the equations of motion for valve float can be evaluated, thus yielding the engine speed at which float occurs?
RE: Carb. Engines vs. EFI Engines -hp per pound
RE: Carb. Engines vs. EFI Engines -hp per pound
For all-out-top-end maximum horsepower production, the carburetor usually wins. This is probably because the performance manifolds for carburetors have been much more thoroughly developed over many years than those for EFI.
Many aftermarket EFI manifolds for older design engines, such as the Gen I SBC, do not have optimum injector placement.
There is also some evidence the evaporative cooling effect of the fuel by the carburetor lowers the intake charge temperature versus the EFI where the fuel is sprayed low down the intake runner onto the top of a hot intake valve.
Having said that, this past year's Engine Masters Challenge was won by an EFI system on a Gen III Mopar hemi; an engine designed for EFI.
jack vines
RE: Carb. Engines vs. EFI Engines -hp per pound
Another thing mentioned was atomization vs gassification of the fuel. It turns out that the displacement of air by gaseous gasoline is usually more than made up for by the increased density of the charge due to the temperature drop from vaporization. Hence, an ultra-low restriction drag racing carb on an optimized manifold may make more power than a port injection setup.
RE: Carb. Engines vs. EFI Engines -hp per pound
That is the exact opposite from what I have been lead to believe, hence the success of down nozzles where wet fuel is injected right above the inlet valve.
Regards
Pat
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RE: Carb. Engines vs. EFI Engines -hp per pound
The displacement of air by gasoline goes on a mole ratio basis. The mole ratio of air to gasoline for an 11:1 mass ratio is about 37:1. That is, 37 molecules of air(N2 + O2) for one gasoline. The reduction in air density can be made up for by a reduction in temperature of about 12 degrees. Since charge temperature reduces by more than 30 degrees from gasoline evaporation, it should make more power this way. Anyway, the Predator Carburetor experience implies that PORT FI has no advantage over a low restriction carburetor. IMVHO, this is only due to the advantage of charge cooling.
I also note that the history of Formula 1 FI setups saw them raising the injectors progressively from a low, below the throttles location until they eventually wound up with the injectors above the intake bell. Reversion is no problem since they use a plenum and fuel stealing by one cylinder from another can be compensated for by computer. I am not aware of benefits other than increased charge density, but there could be other considerations.
RE: Carb. Engines vs. EFI Engines -hp per pound
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RE: Carb. Engines vs. EFI Engines -hp per pound
TTFN
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RE: Carb. Engines vs. EFI Engines -hp per pound
RE: Carb. Engines vs. EFI Engines -hp per pound
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RE: Carb. Engines vs. EFI Engines -hp per pound
The OPs question was clear.
If you wish to change the question you really should start your own thread.
Regards
Pat
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RE: Carb. Engines vs. EFI Engines -hp per pound
RE: Carb. Engines vs. EFI Engines -hp per pound
Sure answers drift, but to suggest the OP asked the wrong question is a bit rude I think
Regards
Pat
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RE: Carb. Engines vs. EFI Engines -hp per pound
Anyway, this exchange is definitely off topic.
RE: Carb. Engines vs. EFI Engines -hp per pound
Regards
Pat
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RE: Carb. Engines vs. EFI Engines -hp per pound
No such suggestion and no such tone.
RE: Carb. Engines vs. EFI Engines -hp per pound