Carbs make more power than FI?

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Re: Carbs make more power than FI?

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Re: Carbs make more power than FI?

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hoffman900 wrote: Wed Mar 21, 2018 4:25 pm
statsystems wrote: Wed Mar 21, 2018 4:24 pm
GARY C wrote: Wed Mar 21, 2018 4:21 pm

That was true in the early days of FI, you may still see it with some of lower budget systems but I don't think that's a case with one thats designed for the application.

Power per dollar would be the question now days.


It certainly did show up in Pro Stock. Even with the RPM limit imposed the numbers don't show much improvement if any. Plus if we believe Warren Johnson, getting rid of the hood scoop would mitigate the RPM limit.

All it did was screw Pro Stock and make the cars look stupid.

They should have let carbs and EFI run together, with or without hood scoops. That's what Pro Stock SHOULD be.
Agree. Pro Stock should have had open induction rules. Run whatever, as long as the throttle body(ies) can't be controlled by the ECU (thinking traction control here). I believe they would all be fuel injected if that was the case and it would look nothing like what the rules specified.
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Re: Carbs make more power than FI?

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Everyone should read this white paper from Honda:

Development of High-Pressure Fuel Supply System for Formula One Engine : www.f1-forecast.com/pdf/F1-Files/Honda/F1-SP2_15e.pdf

They realized a 20hp gain by going from 174psi to 1450psi (rules maximum) fuel injection system and developing a better injector, which allowed them to shorten the pulse and time it with maximum port velocity. They were also measuring the effects of cooling efficiency of the evaporating fuel on the phase delay of intake air pulsation. All this from ten years ago.

I also stand corrected as Formula 1 rules makers made them go to a single injector in 2008.

This is the kind of development you can do with fuel injection that you cannot do with carburetors.
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Re: Carbs make more power than FI?

Post by statsystems »

hoffman900 wrote: Wed Mar 21, 2018 7:03 pm Everyone should read this white paper from Honda:

Development of High-Pressure Fuel Supply System for Formula One Engine : www.f1-forecast.com/pdf/F1-Files/Honda/F1-SP2_15e.pdf

They realized a 20hp gain by going from 174psi to 1450psi (rules maximum) fuel injection system and developing a better injector, which allowed them to shorten the pulse and time it with maximum port velocity. They were also measuring the effects of cooling efficiency of the evaporating fuel on the phase delay of intake air pulsation. All this from ten years ago.

I also stand corrected as Formula 1 rules makers made them go to a single injector in 2008.

This is the kind of development you can do with fuel injection that you cannot do with carburetors.


How much pressure does the Holley system use in the Pro Stock system?
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Re: Carbs make more power than FI?

Post by hoffman900 »

Rules spec it to 90psi.

You need a mechanical fuel pump to get that F1 level of pressure. Also the F1 injectors and their development are way more sophisticated. I’m unsure what the current F1 rules are and what the teams are doing, especially since they’ve gone to turbos.
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Re: Carbs make more power than FI?

Post by peejay »

hoffman900 wrote: Wed Mar 21, 2018 3:00 pm * not as sensitive to gforces < few dynos can test that.

The primary reason why I converted to EFI in 2009-ish.

It took a while to create a way to ensure that the fuel pump inlet never saw air, but once I identified that problem and attacked it, fuel problems related to lateral or vertical G are *gone*.
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Re: Carbs make more power than FI?

Post by roc »

For the carb lovers, I dare to see carbs running well here:

2009 Porsche 911 Engine Running Simulated Nürburgring on Active Dynamometer

PS.: Doctors have been telling this for a long time now: Carb is bad for you! #-o
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Re: Carbs make more power than FI?

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hoffman900 wrote: Wed Mar 21, 2018 7:03 pm Everyone should read this white paper from Honda:

Development of High-Pressure Fuel Supply System for Formula One Engine : www.f1-forecast.com/pdf/F1-Files/Honda/F1-SP2_15e.pdf

They realized a 20hp gain by going from 174psi to 1450psi (rules maximum) fuel injection system and developing a better injector, which allowed them to shorten the pulse and time it with maximum port velocity. They were also measuring the effects of cooling efficiency of the evaporating fuel on the phase delay of intake air pulsation. All this from ten years ago.

I also stand corrected as Formula 1 rules makers made them go to a single injector in 2008.

This is the kind of development you can do with fuel injection that you cannot do with carburetors.
1450 psi = 100 bar; this is in the vicinity of the pressures used in current-production direct-injection gasoline engines, and the injectors used in those engines also have the constraint of completing the whole fuel shot within a limited number of crank degrees. The F1 engine wasn't using direct-injection, but the pressures and injection durations are in the same ballpark.
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Re: Carbs make more power than FI?

Post by Ken_Parkman »

A fuel injector physically cannot atomize fuel as well as an emulsification system in a carb. You can improve injectors with very high pressure atomizers. I looked at F1 rules years ago and they were limited to 1500 psi, probably they would be at much higher pressure if allowed. The other big problem power wise for injection is the loss of vaporization cooling. Seen one reference that quotes a 2% loss in VE going from a carb to injection.

Saw a patent years ago Honda was trying to invent injectors with air in them to get some emulsification. Wonder if it ever worked?

So injection has 2 hits against it for making WOT power. F1 seems to have solved both of these, going to very high pressure atomizers, and sticking them on the opposite side of the air box to gain back the VE. A lot more difficult to control I understand. No idea on current systems.

Everything other than WOT power - injection all the way.
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Re: Carbs make more power than FI?

Post by Walter R. Malik »

Ken_Parkman wrote: Wed Mar 21, 2018 10:40 pm A fuel injector physically cannot atomize fuel as well as an emulsification system in a carb. You can improve injectors with very high pressure atomizers. I looked at F1 rules years ago and they were limited to 1500 psi, probably they would be at much higher pressure if allowed. The other big problem power wise for injection is the loss of vaporization cooling. Seen one reference that quotes a 2% loss in VE going from a carb to injection.

Saw a patent years ago Honda was trying to invent injectors with air in them to get some emulsification. Wonder if it ever worked?

So injection has 2 hits against it for making WOT power. F1 seems to have solved both of these, going to very high pressure atomizers, and sticking them on the opposite side of the air box to gain back the VE. A lot more difficult to control I understand. No idea on current systems.

Everything other than WOT power - injection all the way.
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Re: Carbs make more power than FI?

Post by MadBill »

peejay wrote: Wed Mar 21, 2018 8:23 pm
hoffman900 wrote: Wed Mar 21, 2018 3:00 pm * not as sensitive to gforces < few dynos can test that.

The primary reason why I converted to EFI in 2009-ish.

It took a while to create a way to ensure that the fuel pump inlet never saw air, but once I identified that problem and attacked it, fuel problems related to lateral or vertical G are *gone*.
Back in the early nineties, I was watching a Formula Atlantic (Weber-carbureted ~260 HP 1800 cc Toyota power) race and noticed that in one long sweeper, the backmarker's cars were farting and popping. "No wonder they're at the back; who's tuning that junk?" #-o But wait, it was the leader's cars that were crapping out! The slugs couldn't generate enough Gs to swamp the carbs.... :)
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Re: Carbs make more power than FI?

Post by user-23911 »

Ken_Parkman wrote: Wed Mar 21, 2018 10:40 pm . The other big problem power wise for injection is the loss of vaporization cooling. Seen one reference that quotes a 2% loss in VE going from a carb to injection.


liquid fuel doesn't burn.
It's only the vapour that burns.


So how is there a loss of vapourisation cooling?
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Re: Carbs make more power than FI?

Post by Steve.k »

Barry Daniluks world record setting fastest n/a car in 1/8 mile !!! Fuel injected! Just saying!
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Re: Carbs make more power than FI?

Post by MadBill »

joe 90 wrote: Thu Mar 22, 2018 12:48 am
Ken_Parkman wrote: Wed Mar 21, 2018 10:40 pm . The other big problem power wise for injection is the loss of vaporization cooling. Seen one reference that quotes a 2% loss in VE going from a carb to injection.


liquid fuel doesn't burn.
It's only the vapour that burns.


So how is there a loss of vapourisation cooling?
With a liquid fuel, vaporization occurs to a varying degree all the way from the carb boosters to the point of ignition and beyond. Some years back, David Redszus provided data and spreadsheets to combine evaporative cooling effects with the charge displacement effect of the resulting gas using various chemical and physical parameters.
AIR, the net effect was almost always* a net reduction in the induced air mass. *If the vaporization can be arranged to occur within the cylinder, i.e. direct injection, the charge displacement effect is absent.
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Re: Carbs make more power than FI?

Post by HiPer Express »

Ken_Parkman wrote: Wed Mar 21, 2018 10:40 pm

Saw a patent years ago Honda was trying to invent injectors with air in them to get some emulsification. Wonder if it ever worked?

Some direct injected 2-strokes use that kind of system. it was made to get cheap low pressure direct injection.
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