Improve mileage 350 with Quadrajet

[camshaftgsxr]

Originally Posted by Long79

Don't ditch your EGR it increases mileage, make sure it is working properly. Free flowing exhaust will help some too.

wow this is as wrong as it gets... ditching the egr will improve gas mileage, but it will also make it non emissions compliant

the egr is an Exhaust Gas Recirculation valve, it pumps exhaust into your engine to keep the airfuel mixture from burning too hot while cruising down the highway, exhaust into an engine hurts the hell out of performance btw...

[Oilbrnr]

Originally Posted by camshaftgsxr

wow this is as wrong as it gets... ditching the egr will improve gas mileage, but it will also make it non emissions compliant

Maybe you should take two seconds and notice where the OP lives...

Also, everyone should note that he runs LPG with gasoline as a backup. IMHO advise should be given that is appropriate for that configuration. There has to be some tuning differences.

Just say'n

[kikkegek]

thanks Oilbrnr. Appreciate it!

The EGR is supposed to be only open when the engine is cold. Cruising down the highway I am guessin the engine is nice and warm, which would mean the EGR is closed and no recirculation is being done. right? The way I will be hooking it up, it wil do exactly that.

[kikkegek]

hello, back again. And again a step closer to better mileage.

connected the distributor to the vacuum advance like in all the pictures (right port on the carb). And connected the EGR to the middle SMOG connection (picture with blue letters).

And we drove a long stretch this morning and the mileage was about 1 liter per 4,5 km. Which is a about 10,5 mpg. NICE!

The ca r is being treated this week with Fluid Film for rust prevention. So I can not drive it this week...

thanks for now everbody! to be continued!

[geezer#99]

If you calculate it in Canuck gallons you'll feel better yet. Comes to 12.2 mpg.

[kikkegek]

alrightytighty!

today picked up our ride again. It has been treated with Fluid Film for anti coroosion and is ready for winter. Snow has started coming down this weekend, so we are just in time.

Calculated the mileage from the last ....

*drums mode ON*
.
..
...
....
.....
drove 120 miles (193,08 km)
got gas (LPG in my case)
payd for 51,97 liters (13,729 gallons)

that makes for: 120/13,729 = 8,74 MPG
or
193,08/51,95 = 3,715 km/l

this means improvement. But only for highway...like 99% of this was done driving 90 km/h which is about 55-60 mph.

So mileage is still poor as far as I can judge.

the search continuous...please advise.

[tucsonjwt]

I read that LPG gets 10% less fuel economy when compared to gasoline. So, 8.74 mpg LPG = 9.6 gasoline equivalent MPG. The 3 squares I have owned were all 3/4 ton (2 -454, 1-350) and ranged between 10-12 mpg. In ideal conditions I could get 14 mpg with my 73 C20 454 all highway, but 12-13 was more likely. Cold weather consumes more gas due to choke being on longer. I have known people with 1/2 ton 350s that got 10 mpg. I have also read that tuning a vehicle to run on LPG is different than one running on gasoline. I suspect that most people driving old V8 pickups don't get more than 10 MPG most of the time, unless they keep their trucks in top shape. Just some random thoughts.

[geezer#99]

Are you still using that open element air cleaner. Cold air is a fuel hog. Good for HP but bad for mileage.
Pm the op in this link. He's taking his off.
http://67-72chevytrucks.com/vboard/s...d.php?t=432749

[kikkegek]

Originally Posted by geezer#99

Are you still using that open element air cleaner. Cold air is a fuel hog. Good for HP but bad for mileage.
Pm the op in this link. He's taking his off.
http://67-72chevytrucks.com/vboard/s...d.php?t=432749

I am using a filterhouse with a pipe to the grill. See picture:



The second picture is what it looks like behind the grill.

There are different opinions on cold or hot air being better for mileage.

Some say cold air holds more oxygen, so you get more power from heach stroke of the engine. Some say warm air performs less, so you have less power, so you get better mileage. Personally I think the first sounds more reasonable.

This is what Wikipedia says about a Cold Air Intake:
http://en.wikipedia.org/wiki/Cold_air_intake

This is what Wikipedia says about Warm Air Intake:
http://en.wikipedia.org/wiki/Warm_air_intake

Especially the second piece of text mentions a ECU reacting to the warm air, etc. Since my car has no ECU, a WAI will be of no use, I assume.

Anybody got an opinion on this? or field-experience?

[motornut]

mine was all bypassed,this was summer,flipped top norm for winter
with a winter grill cover i found i got it warmed up real quick (choke of quicker)inside heat and got better gas mileage
my idea being the all the air around the block is warmer, quicker to help vaporise gas then ice cold from the front
in the winter if it's from the piped front (ideal for summer tho)it may clog up quickly depends tho on road spray
but dosn't it have stock, some kinda plastic cover go around to keep stuff out

[Cue-Ball]

Originally Posted by kikkegek

Some say cold air holds more oxygen, so you get more power from each stroke of the engine.

That is true.

Some say warm air performs less, so you have less power, so you get better mileage.

Not really true, but could be viewed that way.

Colder air does hold more oxygen, so it has the potential to create more power. But to make that extra power you have to use extra fuel. Hot air, on the other hand, uses less fuel (at a given throttle opening) and therefore makes less power, but you have to open the throttle further and use more air/fuel mix to make the same power. Quite the conundrum.

The ecomodding communities have been going back and forth over this topic for years now. Hotter air gives fewer pumping losses, but colder air is more efficient. Computer retarded timing removes any benefit of a hotter mixture, but computer controlled injectors can create an always-stoich mixture. Cold air holds more oxygen, but hot air atomizes fuel better. Back and forth, on and on. Unfortunately, there are a LOT of factors at work here, beyond just the temperature of the air.

Cold air generally makes more power at WOT because it allows/requires more fuel and because the carb/throttle body butterflies are no longer the primary restriction on the engine. At anything less than WOT the jury is still out. You may see an increase in mileage using cold air, but you may not. It depends on tons of factors like fuel vaporization, length and restriction of intake tract, engine operating temperature, etc. But something to keep in mind is that air that's too cold doesn't atomize fuel well, so cold intake air can often lose power over warm air.

There just simply isn't a "cold air is more fuel efficient" or "warm air is more fuel efficient" statement that can be made. If you're looking for fuel efficiency you should first look at timing, gear ratios, lubricants, exhaust efficiency, etc. before you worry about intake air temp being any sort of a factor at all.

[Cue-Ball]

Originally Posted by camshaftgsxr

wow this is as wrong as it gets... ditching the egr will improve gas mileage, but it will also make it non emissions compliant

the egr is an Exhaust Gas Recirculation valve, it pumps exhaust into your engine to keep the airfuel mixture from burning too hot while cruising down the highway, exhaust into an engine hurts the hell out of performance btw...

Exhaust into the intake tract would hurt performance, yes... but when the EGR is running you're not shooting for performance anyway since you're at idle/cruise!

Removing the EGR won't increase fuel mileage, it will make it worse since more fuel will be used at idle and cruise. The hotter air being introduced needs less fuel to burn at stoich. Less fuel = better mileage. When you push on the go pedal and are trying to squeeze power out of the engine the EGR closes (it's vacuum operated) and you're essentially running a non-EGR system.

The whole EGR system can be a pain in the butt, because they're failure prone... but it's a system that increases mileage (on a properly tuned engine), not decreases it.

[WILLD420]

What altitude are you at? That will tell you what you can do. Altitude determines allowable compression. At sea level, you will be limited to 8.0-8.5-1 compression with 87 octane unleaded. With propane you can run 9.0-9.5-1 pretty safely.

Assuming I had limited funds, say maybe $800 U.S. Here's what I would do.

Find a set of 305 Small block heads, from the mid 80's. They had smaller chambers that would bump your compression up. Rebuild them using 1.94" intake valves and do a mild cleanup of the port under the valve (Pocket Porting.) Install (Z-28) equivalent valve springs.

Buy a camshaft equivalent to a Comp 260H, or similar with duration at .050 near or under 210 degrees. Stick with a single pattern camshaft, ie. intake and exhaust the same duration.

Buy an adjustable vacuum advance can and install it. The oem can may be adjustable, check before you throw it away. (The oem can is calibrated for gasoline and a functional EGR which allows more timing at light throttle. But can be too much once EGR is no longer introduced.) If you set the timing to specs and you have spark knock at light throttle, an adjustable can will cure this and allow total timing to still be 35-36 degrees.

Throw away the factory high restriction muffler(s) and get a nice quiet free flowing turbo design. (Assuming you have the large truck type that are very quiet but don't flow well at all.)

The cam is optional, but will usually give more power and not hurt mpg at all, especially with a decent exhaust. The increase in compression will really wake your engine up, especially if you are at 3,000 ft elevation or higher. Make sure you have a 195 degree thermostat. As long as you aren't overheating during the warmer times, the hotter an engine runs, the more efficient it will be.

The vacuum advance will allow you to advance your part throttle timing as much as possible while still limiting overall timing to a safe point.

In your picture, it looks as though you have the free flowing stainless exhaust manifolds. Those are just as good as headers for general driving and mpg, don't waste your time or money on tube headers if that is the case.

Tall skinny all terrain or highway tread tires will get better mpg than fat tires, or aggressive mud tires.

Adding compression, free flowing exhaust and timing should net you 2-3 mpg minimum gain assuming nothing else changes. Especially with propane. At 8.0-1 compression, propane isn't going to be nearly as efficient.

[kikkegek]

guys!

thanks for the really extensive (is that corrdect?) answers. appreciate it.

I am at sea level, 15 minutes from the coast in the Netherlands (Europe) freezing my ass of at the moment.

The label is no longer on the car that reads the eact timing settings for my engine at idle and 2500 or 3000 rpms. Can somebody help me, how I should time it?

[lindstromjd]

Originally Posted by kikkegek

The label is no longer on the car that reads the eact timing settings for my engine at idle and 2500 or 3000 rpms. Can somebody help me, how I should time it?

I don't think there's a good answer to that question unless someone here is actually running LPG like you are. It's not a set-in-stone sort of thing. My 75 pickup calls for 4 degrees BTDC, and my 78 corvette with the exact same engine calls for 12 degrees BTDC. It's safe to say that my 350 runs a LOT better at 12 degrees.

I would say just play it by ear, but you probably want more specific than that.

[kikkegek]

oke, lindstromjd, but what you are talking about is initial timing. I am talking about total timing at about 2500-3000 rpm. Because that is the rpms I usually cruise at.

in a youtube vid I saw they said that 32-36 total timing at about 3500 is OK.

[WILLD420]

Gasoline you can run 32-36 degrees total at 3K rpm pretty safe. It all depends on the engine. Some like more, some less. Two identically built engines can desire 2 different total timing depending on load, carbon buildup, casting flash in the combustion chambers etc.

I would start with factory spec on initial timing and go from there. You may have to adjust the advance mechanism under the rotor for total advance. Sometimes you can tolerate a lot of intial advance, but the total advance allowed by the distributor will put you in excess of 40 degrees total timing. To correct this you have to limit the amount of total timing by either making a stop for the weights or brazing the holes in the advance mechanism then opening them up to the point where you get the desired timing.

You want to run on the ragged edge of detonation for maximum power and efficiency. Advance it till it pings, then back off 2 degrees. Take it for a spin, listen if you think you hear pinging/detonation, back off another 2 degrees. Repeat until you find the sweet spot.

I wouldn't get too upset if you can get up to 10 mpg on propane. I drive a 99 lincoln navigator for work and it's averaging 12 around town and 14 on long trips. That's with a 5.4 liter engine and all the modern fuel injection and better engine design.

[Psycho71]

Not much on LP engines. But I can offer up another vote for getting rid of that flex fan, in favor of a clutched fan or an electric fan. Seems like every older vehicle i get has one of those flex fans on it when I get them. And almost every time I pull them off and put a clutched or electric fan on, I can literally feel the difference. And I've never noticed one to cool any better than a good operating clutch fan. The only cool thing I've seen from flex fans are the dents in hoods (from inside out) and other damage they do when a blade decides to depart from the rest of the assembly. Usually at higher RPMs which makes things even worse.

[kikkegek]

ok, when the temperature goes up, I wanna look into total timing.

Right now I wanna focus on earning up the engine more quickly in this freezing weather using some stuff that is still on the engine.

I got the Heat Riser valve in the exhaust.


I have it currently hooked up to a constant vacuum to make sure it is always open. But could hook it up to the vacuum switch on the thermostat housing? So it stays closed untill the engine is warm enough?
But how to hook it up?



then I could hook up the EGR Valve. Does this work together with the heat riser valve?


or does this EGR valve operate on its own?
how should I hook this up?
can I use this small vacuum switch?

[WILLD420]

The vacuum fitting on your thermostat will work on temperature. That is the fitting you need for the thermostatic valve unless I am mistaken. You need to have it apply vacuum once the engine is warmed up.

The EGR, if I remember, works on ported vacuum with some one-way valves or regulators of some sort. Not sure, since we always disconnected them for more power. Shouldn't be too hard to figure out.

If you can't get it to warm up, make sure you have a 195 degree (Celsius 90?ish) thermostat. If you have one for a lower temp, you may never get any heat once the temps go below freezing. You can also cut a piece of cardboard or thin stiff plastic to cover a portion of the radiator during the winter. There are fancy vinyl radiator covers sold here in the states for the colder climates, similar to what the big rig trucks use in the winter to block most of the airflow through the radiator to keep the engines warm.

Don't be afraid to look on other brand vehicle information. EGR and the heat riser stuff are pretty similar from one manufacturer to another, just have to make sure you get the right side of the vacuum valves for your particular application.

[kikkegek]

Originally Posted by WILLD420

The vacuum fitting on your thermostat will work on temperature. That is the fitting you need for the thermostatic valve unless I am mistaken. Not sure how it works, as we live in the desert and usually cut those valves off for better flow when they quit working like they should.

okay, thanks, can you help me with the two way and the four wayt switch. Do they operate differently? Is the twoway normally closed and the fourway normally open?

and can you help me with the other questions?

[foamypirate]

Originally Posted by camshaftgsxr

wow this is as wrong as it gets... ditching the egr will improve gas mileage, but it will also make it non emissions compliant

the egr is an Exhaust Gas Recirculation valve, it pumps exhaust into your engine to keep the airfuel mixture from burning too hot while cruising down the highway, exhaust into an engine hurts the hell out of performance btw...

Actually, you are as wrong as it gets. Recirculating exhaust gas back into the combustion chamber cools the chamber (odd, I know, but it does) and leans the mixture, resulting in IMPROVED fuel mileage. WOT throttle performance and cruising are completely different beasts.

[WILLD420]

Easiest way to tell how those valves work is a piece of vacuum line. Get a piece long enough you can suck on one end and put the other end on the vacuum port. Then get busy figuring out which way the valves work. If you cant' get any air to go through the valve, it's probably stuck 1/2 way between positions.

The EGR and the Heat Valve work independently of each other. One is strictly for emissions, the other for quicker warmups which lead to lower emissions. The purpose of the EGR valve is to dilute the incoming mixture with air that has already been burned, leading to cooler combustion temperatures and a reduction in NOX emissions. Since you are running propane and I don't think you have to worry about the emissions part, the EGR is up to you, whether you run one or not.

If you hook it up and your MPG improves, then it's a good thing. If you hook it up and nothing changes, but you lose power, then it's a bad thing.

Also, since propane burns with less energy than gasoline, it will take a little longer to warm the engine up to operating temp unless you are making power by loading the engine.

Also, the EGR is more of a load sensitive thing, than a temp related mechanism. It should only be working at part throttle with high vacuum. At higher throttle and reduced vacuum the EGR should become inoperative, allowing more power from the engine.

I'm not a lot of help with the EGR part, as we usually don't run them on the engines I've built in the past.

[kikkegek]

Originally Posted by WILLD420

Easiest way to tell how those valves work is a piece of vacuum line. Get a piece long enough you can suck on one end and put the other end on the vacuum port. Then get busy figuring out which way the valves work. If you cant' get any air to go through the valve, it's probably stuck 1/2 way between positions.

The EGR and the Heat Valve work independently of each other. One is strictly for emissions, the other for quicker warmups which lead to lower emissions. The purpose of the EGR valve is to dilute the incoming mixture with air that has already been burned, leading to cooler combustion temperatures and a reduction in NOX emissions. Since you are running propane and I don't think you have to worry about the emissions part, the EGR is up to you, whether you run one or not.

If you hook it up and your MPG improves, then it's a good thing. If you hook it up and nothing changes, but you lose power, then it's a bad thing.

Also, since propane burns with less energy than gasoline, it will take a little longer to warm the engine up to operating temp unless you are making power by loading the engine.

Also, the EGR is more of a load sensitive thing, than a temp related mechanism. It should only be working at part throttle with high vacuum. At higher throttle and reduced vacuum the EGR should become inoperative, allowing more power from the engine.

I'm not a lot of help with the EGR part, as we usually don't run them on the engines I've built in the past.

thanks, thats some great advise and simpel method for figuring out how the switches work (why didnt I think of that?)!!!

I think I'll hook up the Heat riser valve then, to heat up the engine more quickly and see how the vacuum switches work.

I might testrun the EGR to see if it improves mileage. We cruise all the time and allmost never stress the engine, so we are all about mileage and not very hot on power...so the EGR might even help with that!

thanks man!

[kikkegek]

ok,
made a mistake!
When I adjusted the timing I also connected the Heat Riser Valve in the exhuast to the SMOG port. Thereby closing half of my exhausts as asoon as I started the engine.

Still got low 8 mpg...I changed it. plugged the SMOG port and disconnected the Valve so all my exhausts are open all the time.

lets see what this does? right?