CNG vs. unleaded perfomance

[maxman Member Find all posts View Profile Close maxman]

Just curious..
Has anybody with a bi-fuel compared the 0-60 times on both fuels? I believe the CNG to be slower. I have a bifuel F150 5.4L.
I tried this once with the CNG, but haven't had the chance I felt to responsibly and courteously test both at the same time and place. I got about 15 Seconds on CNG in my F150 4x4 regular cab.
Any others?
Max

[mostlyharmless22 Member Find all posts View Profile Close mostlyharmless22]

Re: CNG vs. unleaded perfomance

I have a bi-fuel cavalier and I think the CNG is faster/better. I haven't really compared acceleration speeds specifically because I rarely run mine on gasoline but, when I do, it runs rougher and the performance suffers. I believe CNG is also higher octane than regular unleaded so it would make sense for the performance to be better on CNG.

[CONEBOY Member Find all posts View Profile Close CONEBOY]

Re: CNG vs. unleaded perfomance

I have a dedicated F150 so I can't compare 0-60 with petro.

But I have attached some interesting tests done by the department of energy for CNG vs HCNG (hydrogen blend)

Check out page 9 at the end of section 2.2 where it has 0-60 results.

[ijustride Member Find all posts View Profile Close ijustride]

Re: CNG vs. unleaded perfomance

I think CNG through a standard engine will create less horsepower, CNG has a much higher octain than gasoline, I think its higher than 120. you would have to raise the compression ratio accordingly to get the same horsepower.

[CNGOwner Member Find all posts View Profile Close CNGOwner]

Re: CNG vs. unleaded perfomance

I have a 2001 Tahoe and when I run it on CNG it is much more sluggish and slower than on regular gas

[cngmike Guru & Moderator Find all posts View Profile Close cngmike]

Re: CNG vs. unleaded perfomance

The joys of dedicated vs. bi fuel. Or as my father always says "one size fits all fits no one well." Since no makes variable compression you need a engine that runs premium only with variable timing and cam.

[Highmarker Regulars Find all posts View Profile Close Highmarker]

Re: CNG vs. unleaded perfomance

I have a bi-fuel cavalier and I think the CNG is faster/better. I haven't really compared acceleration speeds specifically because I rarely run mine on gasoline but, when I do, it runs rougher and the performance suffers. I believe CNG is also higher octane than regular unleaded so it would make sense for the performance to be better on CNG.

mostlyharmless22,

I would have your gasoline fuel system checked out. You might have a clogged injector or something. I own a '01 Cavalier and according to my owner's manual here are the following horsepower specs on the 2.2L engine:

Gasoline: 115 hp @ 5,000 rpm (page 6-65 in owner's manual)
CNG: 105 hp @ 5,200 rpm (page 6-6 in supplement manual)

It has been stated here in this thread and it is correct. Natural gas has an octane of about 130, but its optimum compression ratio is about 13:1, whereas gasoline has an optimum compression ratio at about 9:1. All bi-fuel engines are tailored to the gasoline compression ratio, therefore, there is a power/performance loss when running on CNG.

You should be getting better power and performance on gasoline than on CNG in a bi-fuel vehicle. Dedicated CNG vehicles are different.

[josch Member Find all posts View Profile Close josch]

Re: CNG vs. unleaded perfomance

Actually, gasoline's optimal compression ratio varies with octane rating. 110 octane Trick racing fuel runs nice on 12.5 to 1 while 87 octane works nice on 8.5 to 1

[Sorry Dog Member Find all posts View Profile Close Sorry Dog]

Re: CNG vs. unleaded perfomance

My father owned a Morgan Plus 8 for several years.

They all come over to run on LPG to pass emissions since they had basically an unchanged Rover/Buick 3.5 V8 from the 60's

Rated a 190 HP on LPG. He changed it to gas with a Holley 4 barrel since filling up at Uhaul got old. Morgan said it would make 220 on gas. It did have accelerate much better on gas...plus the car only weighed 2200 pounds.

Also, when I used to install V8 generator sets the KW rating for CNG would be less than LPG. Additionally the nozzle had to be a bit larger for LPG.

If the octane rating is that much higher though then a forced induction motor would be a good option.

BTW - increased compression will gain torque at lower RPMS but the increased pumping restrictions at high rpms tend to cancel out some or all of those gains.