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Carb to EFI Less Power?

Started by WhipLash96, July 13, 2021, 04:13:15 AM

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WhipLash96

OK, I am in the midst of converting my Road Glide to EFI. In talking with my engine builder he flat out said that there is a big possibility that be switching from a carb to EFI with the exact same set up that I could lose power instead of gain. Does this make sense to anyone? It certainly defies logic for me, but what do you think?
Thanks,
Whip

HogMike

Quote from: WhipLash96 on July 13, 2021, 04:13:15 AM
OK, I am in the midst of converting my Road Glide to EFI. In talking with my engine builder he flat out said that there is a big possibility that be switching from a carb to EFI with the exact same set up that I could lose power instead of gain. Does this make sense to anyone? It certainly defies logic for me, but what do you think?

Ask him to explain how.
I don't see it.
:potstir:
HOGMIKE
SoCal

WhipLash96

Quote from: HogMike on July 13, 2021, 04:22:25 AM
Quote from: WhipLash96 on July 13, 2021, 04:13:15 AM
OK, I am in the midst of converting my Road Glide to EFI. In talking with my engine builder he flat out said that there is a big possibility that be switching from a carb to EFI with the exact same set up that I could lose power instead of gain. Does this make sense to anyone? It certainly defies logic for me, but what do you think?

Ask him to explain how.
I don't see it.
:potstir:

His very vague response to the "Why" question was in the way that carb atomizes fuel vs. EFI.....  I was looking  more but that is all I got.... :banghead:
Thanks,
Whip

PoorUB

I don't see it either. With EFI you can tune for RPM and throttle position, or MAP depending on the year. With a carb you have idle, mid and full throttle jets. Fuel required at full throttle and 3,000 RPM may be slightly off from full throttle and 5,000 RPM. A well tuned carb does a decent job, but you can tune an EFI tighter. Plus an injector does a darned nice job of atomizing fuel, better than a carb, IMO.

The guy is old school, probably likes breaker points too.
I am an adult?? When did that happen, and how do I make it stop?!

Norton Commando

Quote from: PoorUB on July 13, 2021, 05:32:46 AM
I don't see it either. With EFI you can tune for RPM and throttle position, or MAP depending on the year. With a carb you have idle, mid and full throttle jets. Fuel required at full throttle and 3,000 RPM may be slightly off from full throttle and 5,000 RPM. A well tuned carb does a decent job, but you can tune an EFI tighter. Plus an injector does a darned nice job of atomizing fuel, better than a carb, IMO.

The guy is old school, probably likes breaker points too.

:agree:
Remember, you can sleep in your car, but you can't drive your house.

smoserx1

Well I know this is not what you are planning but remember the 99-01 baggers that had the MM-EFI?  They all had 3.37 ratio primaries and I heard somewhere that was because they made less torque than their carb brothers.  So your builder said it was a "possibility."  He didn't say it would actually happen, but the conversion would add a layer of complexity that I don't see unless you just can't get a carb to run properly on your bike.  My bike has a carburetor (and it runs good) and I wouldn't even consider it but I am very much an "if it ain't broke don't fix it" person.

Hossamania

I would think that if the efi system is set up to match the build, power should not be a problem, and it should run a little smoother than a carb.
If the government gives you everything you want,
it can take away everything you have.

HogMike

Quote from: WhipLash96 on July 13, 2021, 04:42:43 AM
Quote from: HogMike on July 13, 2021, 04:22:25 AM
Quote from: WhipLash96 on July 13, 2021, 04:13:15 AM
OK, I am in the midst of converting my Road Glide to EFI. In talking with my engine builder he flat out said that there is a big possibility that be switching from a carb to EFI with the exact same set up that I could lose power instead of gain. Does this make sense to anyone? It certainly defies logic for me, but what do you think?

Ask him to explain how.
I don't see it.
:potstir:

His very vague response to the "Why" question was in the way that carb atomizes fuel vs. EFI.....  I was looking  more but that is all I got.... :banghead:

In his defense, I have a 2019 with EFI that runs verrrrry nice (after a good dyno tune) BUT my other 3 bikes have carbs.
All the bikes run very well with the EFI bike getting a little better gas mileage. Only difference is the other bikes have choke knobs! I'm NOT going to change the carb on them. Ride ability on all the bikes are just fine, no hiccups stalls or hard starting on any of them.

No need to "fix them until they break".  My son's crew chief has THAT motto on his shop wall. :emoGroan:
HOGMIKE
SoCal

Ohio HD

It only makes sense because he probbaly has no clue as to how to program and tune FI bikes.     :crash:

kd

I did a quick search on carb / EFI power differences.  In the race world they go both ways.  The carb seems to get the more power at full throttle refit over EFI but that's specifically WFO.  EFI can be quickly adjusted to barometric, temp, altitude and other conditions and carb not so much.  Closed loop EFI can be helpful to keep up on changing conditions.  Carb, you need tools and a pocket full of parts. Look at what your building it for and your expectations.  A good tuner can do wonders.
KD

Don D

All things being optimally configured he is 100% wrong

rigidthumper

A carb requires air movement to express fuel, and the slower the air speed, the more likely it will dribble that fuel into the intake tract.
An injector sprays at 58-62 PSI, immediately atomizing that at same rate every time, regardless of the air speed.
Ignorance is bliss, and accuracy expensive. How much of either can you afford?

WhipLash96

Quote from: Ohio HD on July 13, 2021, 08:35:24 AM
It only makes sense because he probbaly has no clue as to how to program and tune FI bikes.     :crash:

I respect your opinion a lot but in this case I am laughing. (In a nice way). This engine builder's credentials are impeccable  and knows how to tune Fuel Injection.
Thanks,
Whip

WhipLash96

Quote from: HD Street Performance on July 13, 2021, 09:25:45 AM
All things being optimally configured he is 100% wrong

Care to elaborate?
Thanks,
Whip

Ohio HD

Quote from: WhipLash96 on July 13, 2021, 05:44:56 PM
Quote from: Ohio HD on July 13, 2021, 08:35:24 AM
It only makes sense because he probbaly has no clue as to how to program and tune FI bikes.     :crash:

I respect your opinion a lot but in this case I am laughing. (In a nice way). This engine builder's credentials are impeccable  and knows how to tune Fuel Injection.

Then why are you on here questioning his statement? You also said "It certainly defies logic for me".     :hyst:

kd

As I stated before, my searches show more WFO power on the track.  I didn`t dig into how much but I expect not a huge difference and only on tap at the top when WFO.  The builder (if reputable and well known as said) may have been referring to what his dyno sheet will show but we all know what that means in real world full range performance.  He also said with the exact same set-up.  That may mean the OP is running cams more suited to carb intake.   :nix:
KD

JW113

Think of it in terms of A/F ratio. If you have both carb and EFI dialed in for optimum A/F, then how does the motor know the difference? It don't! Both will make same power.

Also think of EFI as the latest pollution control device. There you have it...

-JW
2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber

Ohio HD

In general, FI offers a better atomization of fuel, meaning a better burn, more power. As well in general a motor can accommodate a larger bore TB than a carburetor, more flow means more power, as long as the motor can process the flow. This is of course speaking of gasoline powered motors.

kd

July 13, 2021, 06:37:07 PM #18 Last Edit: July 13, 2021, 06:42:20 PM by kd
JW, Ohio,  I agree with that reasoning.  I do however remember threads on here discussing how some cams and their event timing etc. are better suited for EFI.  If it's "pulling" fuel from the beginning of the intake tract (longer intake duration??) instead of just air and injecting fuel vapor onto the back of the valve, One cam may work better than another.  That may be why the builder said "with the exact same set-up".  Maybe the present cams could hold it back on EFI? 
KD

HogMike

I took my softail out today after reading this post just to see if I should change it to EFI.
It's a 2000 model, 95". Mild cam and heads to match.
It was so much fun riding the twisties and hitting the throttle on the uphill curves I decided to just quit messing with it and enjoy the ride.

:potstir:
HOGMIKE
SoCal

Hossamania

Quote from: HogMike on July 13, 2021, 07:26:53 PM
I took my softail out today after reading this post just to see if I should change it to EFI.
It's a 2000 model, 95". Mild cam and heads to match.
It was so much fun riding the twisties and hitting the throttle on the uphill curves I decided to just quit messing with it and enjoy the ride.

:potstir:

I wouldn't even consider changing it, carbs are still fun!
If the government gives you everything you want,
it can take away everything you have.

WhipLash96

Quote from: Ohio HD on July 13, 2021, 05:59:35 PM
Quote from: WhipLash96 on July 13, 2021, 05:44:56 PM
Quote from: Ohio HD on July 13, 2021, 08:35:24 AM
It only makes sense because he probbaly has no clue as to how to program and tune FI bikes.     :crash:

I respect your opinion a lot but in this case I am laughing. (In a nice way). This engine builder's credentials are impeccable  and knows how to tune Fuel Injection.

Then why are you on here questioning his statement? You also said "It certainly defies logic for me".     :hyst:

I agree that his statement was very odd and came from nowhere. I can't explain it. That statement just hit me upside the head.  :scratch: :hyst:
Thanks,
Whip

WhipLash96

Quote from: HogMike on July 13, 2021, 07:26:53 PM
I took my softail out today after reading this post just to see if I should change it to EFI.
It's a 2000 model, 95". Mild cam and heads to match.
It was so much fun riding the twisties and hitting the throttle on the uphill curves I decided to just quit messing with it and enjoy the ride.

:potstir:

Here is the situation. I am running PIG RICH with this CV 51 and I am not able to get the afr into acceptable range. I have the stock CV 51 main in it  (248) and a 44 pilot in it and my rear cylinder is still at like 10.9 and the front cylinder is at 11.5. This is real time data as I have a set of Weggo's hooked up to the bike. My bike makes a lot of power for the cam choice at this current jetting but we all know that this isn't necessarily good to run at such a rich afr. I spoke to Bob Woods about this issue that I am not able to get this any better and he offered a solution for this, but, i can't justify the expense for a carb. Now I have a 58mm TB and all the other things needed to convert my bike to EFI as I have had it for a long time. What I want to do is to put the EFI on and retune. If I lose power as my builder suggests, i will put a different cam in. My fuel mileage SUCKS and understandably with that kind of AFR.
Thanks,
Whip

WhipLash96

Quote from: Hossamania on July 13, 2021, 07:38:25 PM
Quote from: HogMike on July 13, 2021, 07:26:53 PM
I took my softail out today after reading this post just to see if I should change it to EFI.
It's a 2000 model, 95". Mild cam and heads to match.
It was so much fun riding the twisties and hitting the throttle on the uphill curves I decided to just quit messing with it and enjoy the ride.

:potstir:

I wouldn't even consider changing it, carbs are still fun!

They are when they working correctly. :hyst:
Thanks,
Whip

cheech

Have you fooled with the needle in it?  See you mention pilot and main jet but not the needle. Seems in cruise range you'd be "on the needle".