7 mpg and slow

[HurstOlds]

Just reread your initial post. So you unbolted your Edlebrock carb, bolted on the mixer?

Gas goes into the vaporizer, is piped into the top of your air cleaner? Vaporizer is heated from water/antifreeze from your radiator line?

Can you post up the model of your mixer and vaporizer? Or a link to a kit for sale like yours?

Also, what temperature was it outside when you measured the 7 mpg and when you measured the higher mpg? What temp thermostat are you running? I'm thinking you need to heat the lpg up more in your vaporizer to lean out your mixture.

The only other idea I have is due to your air cleaner, your incoming air density is changing as the engine warms up. If you put a duct to in front of your radiator, incoming air density should not be changing as the engine warms up.

What kind of throttle base plate are you using?

 

[pfcvdv]

i've also read on other forums that they got better mpg with a lower gear in the rear end like a 3.42:1 or 3.72:1

 

[pfcvdv]

Just reread your initial post. So you unbolted your Edlebrock carb, bolted on the mixer?

Gas goes into the vaporizer, is piped into the top of your air cleaner? Vaporizer is heated from water/antifreeze from your radiator line?

Can you post up the model of your mixer and vaporizer? Or a link to a kit for sale like yours?

Also, what temperature was it outside when you measured the 7 mpg and when you measured the higher mpg? What temp thermostat are you running? I'm thinking you need to heat the lpg up more in your vaporizer to lean out your mixture.

The only other idea I have is due to your air cleaner, your incoming air density is changing as the engine warms up. If you put a duct to in front of your radiator, incoming air density should not be changing as the engine warms up.

What kind of throttle base plate are you using?

well, the mixer sits on top off he edelbrock carb. lpg comes out the tank as a liquid and it needs energy to vaporize otherwize the lpg comes in the engine as a liquid and freezes the motor since lpg gets near -400F when vaporizing.
u can purchase a kit but in my country the lpg system needs to be installed by a professional to be legal.
i bought the IMPCO kit with vaporizer and mixer for €1000 ($1300) and for those who dont know it, IMPCO is an American product manufactured in the USA (santa ana california). i will update this post with pics as soon as possible
and it's still possible to operate the engine with

 

[pfcvdv]

I just wanna say that I think that the 2" exhaust pipes might be a bit too restrictive for your engine. Take the pipes off and see what kinda performance you get from that change. Id be running 2.5" pipe with that kinda bhp.

I must have missed that part!!! Holy crap! Big tube headers going into an exhaust pipe the same size as the primaries.


2" exhaust was restrictive to an anemic LG4 305 stocker. And on top of that you have THREE mufflers, with 4 chambers. No wonder. Stock was 2.5", with a Y-pipe.

well, it's a dual 2''. wich is still better than a single 3'''. and i have a good, agressive throttle response. and FYI, my dad did some research and found out that the need for a 2,5'' dual is just a myth. something people often dont realize is that the engine fires one cilinder at a time and the smallest part off the exhaust system is the exhaust port in the head. as long as the exhaust does'nt get smaller than a single primary tube there wouldnt be any restriction caused by the pipe.
but i do believe that the mufflers can be restrictive and this week i am getting my 14'' magnaflow mufflers, maybe they will change my mpg a little but the main reason i ordered them is SOUND

 

[Coveted]

I don't want to be the one to debunk your dads research, but its been proven on a dyno.

Ig that wasnt enough put a piece of pipe on your mouth thats the same size of your mouth and exhale hard, then do it with a pipe twice the size of the opening and see which has less resistance / restriction. Not to mention that an engine might only fire 1 cyl at a time but the gas dosent escape the entire system before it fires the second and so fourth.

its not going to make a dire difference on a stockish engine, but you notice it on engines with more fuel and air getting dumped in with bigger cams etc.

 

[online170]

Im sorry but thats just plain wrong.

Exhaust gases flowing out of the cylinders are a fluid. There are lots of fluid dynamics laws and theories you can look up to support this info.

Anything past your headers is a restriction unless its tuned for scavenging properties. There are restriction factors for straight, stepped, 90, 45, 30 degrees, pipes etc. if they are not round or cnc mandrel formed, there are more restrictions. If you were designing a pump and had to route the fluid across a building, you would need to figure out what hp pump to pick. You have to calculate the restrictions based on every single run of piping or ducting to be able to figure out how much push you need at the beginning to compensate for all the losses. The same is true for your exhaust. Except you have a 400hp engine so it will always push out the other end. Problem is, youre eating up hp by forcing thru restrictions.

If you get rid of restrictions, or lessen them, you free up hp.

If you designed a pump based on your dads research you would be fired.

Your headers are a different story because they are more efficient than no headers. Meaning if you dynoed your engine without headers and with headers, with headers would make more power (at your power level) because they are designed for scavenging.





2" pipe is a restriction. Guys with your combo are sometimes running 3" or bigger duals, or a really well tuned 2.5" dual system for a GASOLINE engine. I dont know how that translates over to lpg, but 2" still seems too small.

 

[HurstOlds]

well, the mixer sits on top off he edelbrock carb. lpg comes out the tank as a liquid and it needs energy to vaporize otherwize the lpg comes in the engine as a liquid and freezes the motor since lpg gets near -400F when vaporizing.
u can purchase a kit but in my country the lpg system needs to be installed by a professional to be legal.
i bought the IMPCO kit with vaporizer and mixer for €1000 ($1300) and for those who dont know it, IMPCO is an American product manufactured in the USA (santa ana california). i will update this post with pics as soon as possible
and it's still possible to operate the engine with

Hmmm.....maybe it's a stupid question, but why are you mounting your mixer on top of your Edelbrock gas carb? Is your system set up so you can switch back and forth between gas and lpg?

Based on what you said, it sounds like you have two mixers. The IMPCO on top of your carb, and your carb.

I've never heard of setups like this. I thought most people only used a baseplate or something like that off a gasoline carb, under an IMPCO mixer. You have an interesting setup. I've never built one, so sorry for all the questions.

Doing a quick search, it looks like the only reason to mount it on top of your Edelbrock would be for dual-fuel ability. Is your setup like this one?
http://forum.73-87chevytrucks.com/smfor ... ic=23550.0

 

[pfcvdv]

here are some pics of my system. i still have more to come

the mixer above the eddy carb

the vaporizer

air/fuel meter

and before people start saying: dude u got ur mixer set too rich...
lpg gets better mileage with with a rich mixture. (rich mixture with lpg results in a faster combustion and less heat)

 

[pfcvdv]

the 60 liter tank (18 gallons or something)

in western europe, you can get lpg at almost every gas station.

 

[online170]

Nice clean setup you got there!