EGR and propane

Propane, Butane, LPG, GPL, C3H8, C4H10
Post Reply
Oddy
Posts: 14
Joined: Sat Jul 26, 2014 10:32 am
Location: British Columbia, Canada

EGR and propane

Post by Oddy » Wed Oct 14, 2015 10:10 am

What are the pros and cons of the EGR system on a propane engine besides emissions and legalities? Does it improve mpg, cooling effect ect?


User avatar
Steptoe
Posts: 1482
Joined: Fri Feb 02, 2007 8:32 pm
Location: JAFA , New Zealand

Re: EGR and propane

Post by Steptoe » Wed Oct 14, 2015 4:07 pm

Recommendation is to block off ....I have used the thin block off 'pads' that come with valley cover sets but they dont seem to last the distance and made up heavier ones out of alloy.
Since the fuel is a gas and doesnt require atomising/ vaporising for efficient burn, pre heating is not required. And ideally a cold mixture works best.
And LPG is in effect 'pure' chemical not like other fuels that are a blend of hydrocarbons , many un saturated that produce emission gases....
LPG a saturated HC.. ie when u put a flame to it it has no smoke....unsaturated HC when burn also produce smoke.
Which in a very simplified manner is why some of the exhaust gases get recycled and re burnt.
My Spelling is Not Incorrect...It's 'Creative'

storm
Posts: 565
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: EGR and propane

Post by storm » Wed Oct 14, 2015 5:36 pm

Oddy wrote:What are the pros and cons of the EGR system on a propane engine besides emissions and legalities? Does it improve mpg, cooling effect ect?
You don't want to know about emissions and legalities yet you do want to know about things that directly affect emissions and legalities :roll:
Steptoe wrote:Recommendation is to block off ....I have used the thin block off 'pads' that come with valley cover sets but they dont seem to last the distance and made up heavier ones out of alloy.
Since the fuel is a gas and doesnt require atomising/ vaporising for efficient burn, pre heating is not required. And ideally a cold mixture works best.
And LPG is in effect 'pure' chemical not like other fuels that are a blend of hydrocarbons , many un saturated that produce emission gases....
LPG a saturated HC.. ie when u put a flame to it it has no smoke....unsaturated HC when burn also produce smoke.
Which in a very simplified manner is why some of the exhaust gases get recycled and re burnt.
Have to disagree with you there steptoe.
A properly working EGR has no effect on a system at any time except part throttle and cruise. EGRs are not designed to vaporise fuel they are designed to recirculate a small portion of exhaust gas and also to cool the combustion process. I have left it on in all post 1986 conversions (ULP Cars) and have not seen any issue that can be tracked back to EGR. In Australia and New Zealand it is illegal to disable the EGR, even with LPG only conversions, on post 1986 vehicles.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

User avatar
Steptoe
Posts: 1482
Joined: Fri Feb 02, 2007 8:32 pm
Location: JAFA , New Zealand

Re: EGR and propane

Post by Steptoe » Wed Oct 14, 2015 6:56 pm

EGRs are not designed to vaporise fuel
OK may have explained incorrect.. the egr exhaust 'tunnel' under the inlet causes heating of the of the charge.. not directly EGR function but certainly part of it and results in heating of the charge.
So with lpg .. these tunnels need to be closed off regardless.
My Spelling is Not Incorrect...It's 'Creative'

storm
Posts: 565
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: EGR and propane

Post by storm » Wed Oct 14, 2015 8:19 pm

Steptoe wrote:
EGRs are not designed to vaporise fuel
OK may have explained incorrect.. the egr exhaust 'tunnel' under the inlet causes heating of the of the charge.. not directly EGR function but certainly part of it and results in heating of the charge.
A couple of things are wrong with this. What you call the "egr exhaust tunnel" original had nothing to do with EGR at all. Infact GM were making manifolds with the exhaust crossover years before EGR was even thought of. (check the attached picture) They did this to help with drivability (especially in cold climates). There are V engines (note I didn't say V8 but I said V engines meaning V4 and V6 as well) that do not have the EGR coming off the inlet manifold but rather coming off the exhaust manifold and being fed into the engine via an EGR plate at the carb or EFI throttle body.. Next if you are worried about heat from the exhaust crossover (which we now know has very little to do with EGR) I would advise you to get a manifold without a heat riser http://www.edelbrock.com/automotive/mc/ ... p-sb.shtml
Steptoe wrote:So with lpg .. these tunnels need to be closed off regardless.
No they don't. I accept this is your personal opinion but it is not a categorical fact.
Attachments
$_75.JPG
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

Oddy
Posts: 14
Joined: Sat Jul 26, 2014 10:32 am
Location: British Columbia, Canada

Re: EGR and propane

Post by Oddy » Wed Oct 14, 2015 9:31 pm

What i was thinking of doing is filling the exhaust crossovers in the heads with aluminum to block them off( and those huge holes in the exhaust bowls). So was wondering if the egr effects the part throttle economy at all along with the cylinder cooling effect i read about and if this applies to propane. I could plumb it off the headers if i had to i guess like the vortecs.

storm
Posts: 565
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: EGR and propane

Post by storm » Wed Oct 14, 2015 11:09 pm

EGR can actually help, within reason, with part throttle/cruise economy because it helps to cool the combustion process and this can allow more timing. Remember, however, that LPG has quicker timing up until approximately 3000rpm anyway but after that it practically stops advancing while petrol timing can advance much higher in the rev range.

I, personally, don't like port filler in engines that are used on a regular basis. It is great for testing port designs but I question its longevity in street cars that are used on a daily basis. As I said in reply to Steptoe if you don't want a heat riser get a manifold (I even linked to one) that doesn't have one.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

C3H8
Posts: 1001
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: EGR and propane

Post by C3H8 » Thu Oct 15, 2015 1:02 am

Two different opinions but both not really related to each other. Steptoe is talking about the exhaust crossover port/tunnel used for helping cold gasoline to atomize in colder climates, which Storm is correct about. A temperature controlled gate forces exhaust through the tunnel for the first few minutes to improve driveability. It has nothing to do with the EGR. The exhaust crossover strictly reroutes hot exhaust gas over to the other exhaust manifold through the intake under the carb to warm the air/fuel mixture on a cold engine.

The EGR valve, again as Storm mentioned, is used to cool combustion temperatures by allowing exhaust gases to enter the intake manifold mixing with the air/fuel mixture during specific engine operation times. Older engines used vacuum with the flow controlled by a vacuum temperature sensor to control the EGR valve. Newer engine used an electric solenoid to send the vacuum to the EGR at a specific time, or, even newer engines use electric EGR's only controlled by a computer. Initially when we first started doing conversions we disabled both the crossover gate and disconnected the EGR vacuum line. After all, propane did not need that emission crap, right?

Wrong. Disabling the crossover was fine. The power on propane was better and being a vapour it did not have any of the atomization issues gasoline had. Plugging or blocking the crossover was even better but pulling the intake added several hours to the conversion so in most cases we did not do this unless the intake was pulled for something else.

The EGR on the other hand is a great device. It really lowers Nox (oxides of nitrogen) which contribute to smog. It cools combustion temperatures making life easier on the internal parts, especially the exhaust valve surface. It allows an increase in ignition timing to improve mileage during cruise when the EGR is open the greatest amount of time. We stopped disabling EGR's after we ran emission tests with the co-operation of the Canadian government. The tests proved EGR operation was just as beneficial on propane as on gasoline. The CNG industry ran the same tests on CNG and found the same results.

There is no logical or proven reason to disconnect an EGR other then if an engine is being radically changed from the factory.

Post Reply