Re-Graphing a Hitachi Dizzy for LPG

thedogzeus · Post by **thedogzeus** » Sun Aug 03, 2008 8:08 pm

Hi All,

Just convertered my '83 wagon to gas only. Need some help with re-graphing the dizzy to suit LPG.

My EA81 runs a Hitahi Electronic Type dizzy. From doing a bit of research, it seems LPG needs quick advance over the first 2000rpm then level out. Petrol has the opposite curve with slow advance over first 2000rpm then steeper advance at higher revs. In addition LPG requires an overall lower total advance than petrol. LPG requires around 7deg less total advance than petrol.

Currently I've got; 12deg inital static advance, then the dizzy gives me another 12.5deg, total advance = 24.5deg. Vacuum advance adds another 7.5deg, total = 32deg.

I'm thinking;
a) disconnecting vacuum advance will give me correct total advance
b) reducing tension of weight spring will give quicker (steeper) advance

Does anyone have any experience/thoughts on this and also any ideas where to get lighter tension springs??

Thanks in advance guys.

steptoe · Post by **steptoe** » Mon Aug 04, 2008 7:12 pm

I did mine by removing the post that the rootor button sits on and brazed the outer edges of the slot that the centrifugal pins slide in - all trial and error but it is easy to remove this rotor post. I counted on 28 maximum advance being initial at about 14 BTDC plus 14 mechanical. I kept vac advance connected figuring it drops out as soon as load comes on. Had good 5 years out of it.

Curious as to what system you have under bonnet, can you share ?

thedogzeus · Post by **thedogzeus** » Mon Aug 04, 2008 9:26 pm

Cheers Steptoe, but being new with re-curving dizzy's you're gonna have to hold my hand a bit!

I found an exploded view of my Hitachi (or near enough to), which bits did you mod and how does that alter the curve? Did it help a lot with power and economy? I'm hoping so as mine is chewing the gas.

I had a 32/32 Weber onboard but could not find an LPG mixer to suit, so I had to revert back to the old stockie peice of s**t. I've got a 2L Toyota throttle body that I will put on a soon as I get around to crafting up an adaptor plate.

Any more tips on dialling in the EA81 for gas would be greatly appreciated. As it stands she's stock as a rock. Cheers again for your help Steptoe.

steptoe · Post by **steptoe** » Tue Aug 05, 2008 4:48 pm

Not sure where yer hands have been, but here goes...

I have not done this for a while but I remember

1.0 Under the rotor button in the shaft, is a screw under a plug. REMOVE

2.0 I remember prising the electronics reluctor thing off with a flat blade screwdriver either side. This has a small roll pin that sits against the shaft, let it stay there and this should also indicate UP for you on reassembly

3.0 Maybe just the two screws at the side holding plate to body UNDO. NO NEED TO UNDO OTHER SCREWS holding components together

As the centrifugal weights fly out, they have fat pins going UP through the slots on the tangs at the base of the rotor arm. By limiting how far out they are allowed to travel towards the outer you are limiting the mech advance

As far as economy, best is 60litres 500Km, regularly do 540km to 68 - 70 litres
Search STEPTOE and HITACHI in last few months and you may find some good reading (maybe not!! )

steptoe · Post by **steptoe** » Tue Aug 05, 2008 4:54 pm

Ah, mixer ring set-up. Think efi throttle body adapted to somewhere off the inlet manifold ( does not matter ) I used a Volvo 2.3 litre TB adapted to the manifold inplace of a carby, it used to bog down too much on take off (too big ?) and oddly, would fire and stay running first thing every morning defying LPG theories ( it is said to allow gas to settle in air, making fist gulp too rich too ignite until new fresh mixed vapour arrives) Answer may have been in the 50mm PVC ducting stoping air from gong steel or alloy cold overnight ?

I'm sure any TB off 1.8 litre will do fine, I started to look for the two stage two throttlebody to fit up but ran out of time/desire and back to running LPG through twin hitachis

thedogzeus · Post by **thedogzeus** » Tue Aug 05, 2008 7:36 pm

Thanks Steptoe, I know where I'm at with the rotor arm modification now. How much did you braze up, from looking at a previous post that had a photo of the rotor arm you modded, I'm guessing about 2mm, would that be right?

Did you mod (reduce tension) the springs that hold the weights? I'm getting about 85km to 15L of LPG, which is CRAP!! I'm really hoping re-curving the dizzy is gonna make a BIG difference. I've had it back to the LPG joint for a readjust and they have leaned it off as far as possible, but economy is still bad.

The throttle body I've got is from a 2.0 litre Camry. I'm thinking I'll just weld the mixer ring to the top of the TB, unless you have any better ideas.

Thanks again for you time and advice.

YouTube · Post by **El_Freddo** » Tue Aug 05, 2008 7:53 pm

I've heard that the mixer ring isn't the best mode of delivery for gas. My mate has one on his rangie and he doesn't think much of it. My dad's Rangie has someother type of mixer that is apparently a better system to use.

Bennie

steptoe · Post by **steptoe** » Wed Aug 06, 2008 11:39 am

the slots have been reduced to a total of eight (8) mm from the extreme end of each end. I used a small diameter round file for the finish of the brazed outer end.

I have seen some very good results with mixer rings on a wide range of cars. The positive pressure converters use the mixer ring. Mine is Impco negative pressure set up and needs the Impco style mixer (I think) I have seen pos pressure feed just to inside the sealed air filter - no mixer, ring or otherwise. These were the set ups that gave gas a bad name for power outputs in my mind.

Reduce your spark gap by 0.2mm.

Did not play with springs at all in dizzy, try a bit more initial advance ?

What was compression and fuel consumption like before? Surely a better measure is going to be over the tank full? not just 85km

Can you find the name of the converter or number, country of origin cast into it somewhere?

thedogzeus · Post by **thedogzeus** » Wed Aug 06, 2008 10:20 pm

Converter is a Zavoli from Italy (oh s**t), the last Italian product I had was a gas oven and I dont even want to talk about what happened to that.....

The tank I've got is a small underbody one that has 38 usable litres. I'm getting around 220km from a full tank (hence the 85km per 15litre). I haven't measured compression yet, I guess I ought to do that eh, just to make sure all is good.

From Steptoe's numbers, I should be able to get 125km from 15litres.

Just to clarify Steptoe, you restriced both slots to 8mm each? I measured the slots as they are now and one is about 9mm and the other 11mm.

Any advise on the TB with mixer ring setup, any better ideas? If not I'm just gonna have a crack at it. I'll post some photos of progress and finished result for anyone who might be interested and might want some reference piccys.

steptoe · Post by **steptoe** » Wed Aug 06, 2008 10:53 pm

Now , you got me, what they were to start off with I cannot say, but they have both ended up the same ! Gees, they may have even different offsets to each other as in starting different distance from the rotor post - works anyway

Lots of the LPG stuff has come out of Italy, although I begin to wonder how big these manufacturers are becuse everytime I look thereis a different Italian name on the gear. We are just not used to the Euro stuff much in this country and i am sure the italians are ahead of in this game and it is reasonably priced too.

Under tray - well done !!

Fuel gauge read of the tank ? Depending on the dial on the tank if it is axiom or sidek, about an inch diameter, screw on top and bottom a sidek 110 - 3 ohms in the exact order 110-3, reads nicely with factory gauge, simple wire hook up.