Holly or flapper inj on 3.5 rr with bigger geads and cam?

gulf blue rsr · Post by **gulf blue rsr** » Sun Jan 31, 2010 2:03 pm

Hi, before I go mad and rip the holly and manifold off to put the injection back on, I'm intending to put lpg on.

Which will give the best results?

I see that RPI as well as others do a top hap cover to go on the holly with a mixer on the side, I also see that these cost £££££££££££££!!

I was thinking that it would not be too difficult to make my own and just put a mixer on the side job done!!

What size mixer would I need for best performance, anyone able to help?

The other thing is that the holly is running way too rich but I've not got the time or energy to start messing with jets...also not got any other jets!!! This was the 1st reason for just putting the injection back on just for easy life.

Then I got to thinking that if I'm going to be running lpg most of the time surely the jets don't really matter I can just leave it rich??

What do you lpg experts think? Carb or inject??

Thanks

STEVE

ChrisJC · Post by **ChrisJC** » Sun Jan 31, 2010 6:54 pm

It depends on a lot of things.

Carbs will be more reliable than a Flapper EFi for the simple reason that the EFi system will over 20 years old.

And with regard to mixing and matching LPG components, I tried that, and it took an awful lot of effort to get the system to work anywhere near right. The simple issue was that the mixture adjustment wouldn't go lean enough to get it any better than about 12:1, usually closer to 10:1. I ended up blocking up about 50% of the holes in the mixer ring. It still had a flat spot when coming off idle, and it leaned out as the engine got over 4000rpm. The best I could do really was get it to 14.7:1 whilst cruising.
On my Landie where it's a complete kit, it works brilliantly, cruise at around 15:1, down to 13:1 whilst accelerating, and shuts off on overrun.
Motto: Buy a known good combination!

Chris.

Chris.

badger · Post by **badger** » Sun Jan 31, 2010 7:59 pm

I'd suggest avoiding that elbow mixer and source a proper "moving plate mixer" that fits on top of the carb with its own air filter element. Can't remember the name of the maker just now, but memory says they are imported from Australia...... Bottom line is this - coupled to an OMVL R90E mixer it will work perfectly on your engine.

gulf blue rsr · Post by **gulf blue rsr** » Sun Jan 31, 2010 8:43 pm

Hi, thanks for the responses, I have several kits on various dead Range Rovers but none with 4 barrel carb, so need to use one just to keep the costs down, I think people on here have had some bad experience from this link/seller but I just did a google search for "moving plate mixer" and came up with this link, 10th picture down, says it is for 4 barrel carb.... with adjustable plate...., is this what you are on about badger?

http://www.lpg-kits.com/mixers.htm

Thanks again, keep the help coming!

Steve

badger · Post by **badger** » Mon Feb 01, 2010 6:22 pm

Nope, memory says it was made by sprintgas or somesuch, but I can't find any links, I've been looking!

badger · Post by **badger** » Mon Feb 01, 2010 6:24 pm

Ta-daaaaaaaaa!

http://www.jaymicsystems.com/catalogue/cat18b.htm

That's the baby!

gulf blue rsr · Post by **gulf blue rsr** » Mon Feb 01, 2010 6:53 pm

Superb effort

Thanks for that I have just emailed them asking for a price delivered to my door!

I assume that all I then need is rob the rest of the kit out of one of my scrappers and just connect up to the Vapouriser, bit of fettling and job done!.......easy as that!!

I have a couple of the omvl tandem vapourisers, I take it it would be best to use one of these?

Thanks again most helpful!

Steve

badger · Post by **badger** » Mon Feb 01, 2010 9:13 pm

There's a vacuum switch that has to be connected as part of the sprintgas mixer, its purpose is to use vacuum to lift the mixer's plate out of the way when running on petrol so there is no restriction. Obviously you'll need petrol shut-off solenoid valve and gas control switch etc etc, but as for the tandem vapouriser, try it and see.
Good luck.

gulf blue rsr · Post by **gulf blue rsr** » Mon Feb 01, 2010 10:43 pm

Ok will try the tandem, will let you know how I get on and what the jaymic people come back with.

Is my thinking right that as for the jetting for petrol I can leave it alone as the gas will not be affected by them? I know that for petrol it is all wrong running too rich, but it is running and starting, so good enough, the plan is to start on petrol and run on lpg, the 1st Range rover I had was on twin stromberg carbs with the springs etc taken out, I had no petrol tank or petrol at all, started and ran totally on lpg did 17k miles in the year with no probs! I originally went with the holley just for a play to see what the performance gain would be like, but obviously with out spending the time to set it up properly with the right jetting it is not very good!! hopefully it will be better with lpg, I'd be happy to spend the time setting it up properly to get some performance and economy!

Thanks for the help!

STEVE

Quagmire · Post by **Quagmire** » Tue Feb 02, 2010 8:28 am

How the car runs on petrol due to mixture will not affect the mixture on LPG and vice versa. The vapouriser and mixer plate/ring are in effect a second separate carburation system so you can have one fuel running rubbish and still use the other.

My car runs OK on petrol (running slightly rich), but could run muuuuuch better. However, as it starts and runs on petrol well enough and i hardly ever drive on the expensive stuff i have never got round to sorting it out fully.

That and the carbs will soon go, replaced with EFi

Then when i do run on petrol it will be as good a setup as the LPG

Dual fuel is great!

gulf blue rsr · Post by **gulf blue rsr** » Tue Feb 02, 2010 9:14 pm

Quagmire wrote:How the car runs on petrol due to mixture will not affect the mixture on LPG and vice versa. The vapouriser and mixer plate/ring are in effect a second separate carburation system so you can have one fuel running rubbish and still use the other.

!

Thank you! I was pretty sure that was the case but good to have it confirmed!

I've not had a reply from the Jaymic people today, hopefully get one in the next day or so.....

Going back to the comment by Chris at the start of the thread, yes the flapper efi setup will be 20years old, but again as I am after running nearly always on lpg coupled with the fact that I have several complete efi lpg setups, would I be better going back to efi to save spending more £££ buying extra parts to run with the carb? which setup will give me the best performance and or reliability assuming that again how it runs on petrol with the efi was not high priority just a means of starting with a back up fuel when out of lpg?

Sorry for all the ??? I'm reading and taking on board all arguments and open to all offers of advice!!

Thanks

Steve