Lotus Elan and Lotus Elan Plus 2 Forums

Dear All

Just spent an enjoyable morning in the shed swapping out the old EFI throttle bodies....





to the new (rebuilt ) plenum....





It went like stink but had to remove it last year ( or was it the year before ) due to difficulty tuning ( later found to be an ignition wiring fault ) and it exploding....the problem was ( is ) that due to the ignition being wasted spark and the plenum being fed by a throttle body that fuel in there was ignited by the wasted spark due the inlet valve being open at 10 BTDC...( Exhaust stroke/overlap)
Have now re-built it with a pressure relief valve...let's see if that works...



John

P.S.

Does anyone know of a fix?

Top of head thoughts to remove wasted spark
1) revert to distie ignition
2) use the cam cover with cut-out for distil drive, and rig up a cam sensor

Peter

Peter
No thanks,don't want to go back to a dizzy

The dizzy was used at first as a cam sensor but now I have the HT block there and I do like the wasted spark setup..

John

P.S.

Someone is bound to say Dellorto or Weber...

john.p.clegg wrote:
P.S.

Someone is bound to say Dellorto or Weber...

Actually I was thinking you come and plumb up my new boiler...

?6.00 per hour and unlimited tea and I'll call it a deal...

John

John- Have you run it yet on the new throttle bodies? I'm just curious to see if that helps. I'm planning to use bike injectors on my conversion (Zetec) but don't like the distance they place the injectors away from the valves. My thoughts are that that the closer to the valves (heat) the less chance there will be for fuel pooling in the manifold on shut off and causing problems on restart. Your new throttle bodies seem to somewhat correct that. I'll probably add injector bosses to my home made manifold near the head and plug the bosses in the bike injectors.

I haven't read of any problems with TBI's and wasted spark ignition in other applications. Are you pretty sure that's the problem?

Bud
You may have it the wrong way round , I have been running the GPZ1100 throttle bodies sine Jan 2009 no problem,just fancied a single throttle and plenum for simplicity,saves all that butterfly balancing and had much better response off the throttle stop...but also when I encountered the wasted spark problem..all the valves are "connected " to the plenum unlike with the four butterflys and forms one plenum full of an explosive mix...

John

I did misinterpret it. I saw what looked like a mass air flow sensor in both pics but didn't realize you'd gone to a single throttle body. I enlarged the photos. It's clear to me now (follow the throttle cable) Duh. I was following your old thread but it's been awhile. I didn't realize it exploded after the switch to the plenum. I'll try to keep up.

Hmmmmmm makes a pair of webers look trouble free in comparison

No No No No No no no no no
It's just a piece of pipe with a door at the end to let some air in......the complicated bit is firing some ( a metered amount of ) petrol down the pipe to create combustion....

John

john.p.clegg wrote:No No No No No no no no no
It's just a piece of pipe with a door at the end to let some air in......the complicated bit is firing some ( a metered amount of ) petrol down the pipe to create combustion....

John

What a brilliant idea, metered petrol to create combustion, next thing you know someone will invent the Carburettor , and no need for 15mm water pipe / fittings, but that will be soooo far in the future !!!!!

Say how about making something round with rubber on it that the car can ride on ???

I could call it the ......... wheel?

John

"What a brilliant idea, metered petrol to create combustion, next thing you know someone will invent the Carburettor,"

Untill the day that someone does invent a carburettor that provides accurate fuel metering over a wide range of load and RPM changes I'll stick to my EFI thanks.
Cheers
John

funny wasted spark is pretty common, wonder why in this case it is exploding.