Carb to EFI swap; how much gain in numbers could I expect?

jerry S · Sep 18, 2004

My engine is fresh, with 50 miles on it. Its top dyno run was 351 hp/331 ft/lbs torque at the wheels. Torque is MUCH higher at lower rpms. Assuming 20% drive train loss from my C-6 (could be as high as 30% according to some), this means my peak hp 438 at the fly. I have a Holly 650 double pumper on it now. I was looking at the Edelbrock web site for the multiport EFI system and they speak of 126 hp gain and 120 ft/lbs torque gain on a 302 from swapping the carb for the EFI system with no other mods. Would I expect to see similar gains on my 351W or is their claim just advertising puffery?

jS

Route666 · Sep 18, 2004

Holy crap! I'd like to know if gains like that are possible too!

The swap Edelbrock did most likely involved a small and/or untuned carb, a new (better) manifold, and the injection equipment. Do you have a link to it?

allcarfan · Sep 18, 2004

I seriously doubt you will gain any significatn hp by swapping to EFI....unless your engine is completely untuned

BlueMonster65 · Sep 18, 2004

i agree with allcarfan.
usually with efi more torque is developed at low rpm and less top end hp.
for all out hp a carb is the way to go. however that is not always true some efi sys. that allow independent cly. tuning can be better than any carb setup.

jerry S · Sep 18, 2004

Route666 said:
Holy crap! I'd like to know if gains like that are possible too!

The swap Edelbrock did most likely involved a small and/or untuned carb, a new (better) manifold, and the injection equipment. Do you have a link to it?

You are right. What I failed to notice when I skimmed the reading was that they also added new cyl. heads and a new cam. When I rebuilt my stock 351W, I too added Performer RPM cyl. heads and a new cam and these two mods probably account for most of my hp gains.

http://www.edelbrock.com/automotive/index.html

If it sounds too good to be true.....

88 Fox GT · Sep 18, 2004

You will gain a good amount. Just think of it. Precise fuel metering ALL the time. The fuel injectors also atomize the fuel better, just a big sray of mist into each cylinder. I don't think you will see 100hp more or anything, but you will get some.

65mistress · Sep 18, 2004

Not to mention, if you get one of the aftermarket kits from places like TwEECer, you may be able to pull even more power out of your engine. In some cases 80-100 hp.

allcarfan · Sep 18, 2004

the day a company makes a 100% bolt on EFI system that will give me 100hp more than what I have...I will be the first in line to buy it.

Route666 · Sep 19, 2004

Yeh I don't think you could ever have a fuel injection kit that increases maximum horsepower over a carbed motor by a large amount. If you tune for max power with a carb, it's going to be pretty efficient at max power because of intake air speed/turbulence mixing the mixture well. I think what FI will offer you over carb is better mileage and driveability while maintaining the power, and even gaining some over the whole rpm range. In general anyway.

6Stang7 · Sep 19, 2004

Hp will go up, but not by that much. Torque increases by about 25%.

allcarfan · Sep 19, 2004

so if i make 400ftlbs of peak torque, you are saying i would get 100ftlbs more torque converting to EFI??

usedtobe 67p51d · Sep 19, 2004

Hotrod mag did a test about three or so years ago The carbed motor made 2-3 more hp but wasn't as smooth on delivery. it was a full tilt race carb

Hack · Sep 19, 2004

I don't think you should expect a hp or torque increase. But you should expect easier cold and hot starts, if you run a radical cam it will seem more tame, you won't have to tear the system apart and adjust it, fuel economy will improve,

Route666 · Sep 19, 2004

allcarfan said:
so if i make 400ftlbs of peak torque, you are saying i would get 100ftlbs more torque converting to EFI??

I think maybe he meant you'd get 25% more area under the torque curve. An overall 25% increase. That sounds more reasonable.

6Stang7 · Sep 20, 2004

Route666 said:
I think maybe he meant you'd get 25% more area under the torque curve. An overall 25% increase. That sounds more reasonable.

That's part of it. It's also like the saying that manual drivelines lose 15% hp through them. If you have the same driveline, but increase the hp on the motor by 50hp, why should you lose more power through the same driveline? It only requires X amount of force to move it. The 25% is what you can expect on a normal motor. Of course you won't see 100 ft/lbs of torque on a 400 ft/lbs torque motor. EFI will also give you smoother acceleration, faster whined ups, and you will see an increase in gas mileage by about 10%-15%.

jerry S · Sep 20, 2004

thanks everybody for the input so far

6Stang7 said:
EFI will also give you smoother acceleration, faster whined ups, and you will see an increase in gas mileage by about 10%-15%.

Aside from the better fuel economy, would I notice any real performance gains, like a drop in my 0-60 mph time by .2 of a second or something like that?

Route666 · Sep 20, 2004

6Stang7 said:
That's part of it. It's also like the saying that manual drivelines lose 15% hp through them. If you have the same driveline, but increase the hp on the motor by 50hp, why should you lose more power through the same driveline? It only requires X amount of force to move it. The 25% is what you can expect on a normal motor. Of course you won't see 100 ft/lbs of torque on a 400 ft/lbs torque motor. EFI will also give you smoother acceleration, faster whined ups, and you will see an increase in gas mileage by about 10%-15%.

You should lose more with more power IF you make more power at higher rpms, as gears and driveshaft will be rotating more, and so more gear teeth meshing interactions, and more rotational inertia. I do see your point though, a gearbox will only take a certain amount of power to run at a certain speed, regardless of the power being put into it (to a reasonable extent, too much power may bend and heat things, requiring more power, but is the extreme case).

I by no means meant that the torque gain was the only thing. So you did actually mean 25% max torque gain is possible with say a starting 302 with 200 ft-lbs or so? I can't really see 25%, maybe 20%, but then again, stranger things have happened. What I suppose I'm saying is, I can't really see a carb being 20% less efficient (at mixing/atomising fuel) than a similar power EFI. (EFI 25% more eff. than carb = carb 20% less eff. than carb right?)

Is the consensus that you will definitely gain performance, driveability and fuel economy with a properly tuned EFI setup over a carb setup of the same magnitude? I believe this, it is easy to see why, it is all worked out, no set compromise tune, just measure everything on the fly and give as much fuel as is needed from a high-pressure nozzle.

anyways, enough of my yammering.

Carb to EFI swap; how much gain in numbers could I expect?

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