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November 2013

Robert Burnett

medusa technical info

November 12, 2013

Hi, Veronica here with a bit of an explanation.

Here is some good Medusa technical info off some queries on Robert’s various forums:

– re the two engines. I will be running them off two xj6 distributors ,with points no less , so no ecu needed . I have one distributor off bay for a tenner ,and will probably make the other one from a v6 one.
fuel will be lpg , propane ,and use a normal vapouriser and ring in each inlet . so no ecu there either . I have 2 doughnut tanks to put in the tail inside the fishy bit .

– im not worried about the engines fighting each other at all at all ,if you imagine the situation ,taken to extremes , one engine puts out 50 bhp , and another puts out 300, you end up with a simple addition of the two when running steady state . and a strange slight percentage difference in the two steady state outputs as they accelerate . (this is how I imagine it anyway)
its a little like any engine , there are cylinders doing more work , due to being favoured in the manifold pulse ram tuning etc , and other ones doing less work , they all combine at the crank to contribute what they can , its the same here , just the cranks are connected externally .

in this instance , bhp of each engine is 220 and 240 ,with full quiet inlet and exhaust , I think a fair estimation of 500 bhp unrestricted is likely , chassis is 480 kg ,and each engine 165 kg… if I can get the whole thing at less that 1000 kg that will be fine , twin rear wheels here we come !!

firing order wise ,after a fair bit of research and reading , into the world of tractor pulling and other combined engines , I have found there seems to be a consensus that it doesn’t matter a hill of breans if they are synchronised in any special way .

so I thought ok , how can I use this to medusa’s advantage … I decided to run it so the back engine fires between the firing on the front engine .so prob 45degrees after each no1 engine firing , no2 will fire .
there are two ideas behind this.

1) it will be easier to crank the engines with a remote starter on the gearbox if there is only ever one compression to cope with .

2)it will sound unique , as far as I can work out , you could not make a single crank engine sound like this will sound. :-0 😯 😀

are the newer 24 valve ally block versions , ones a 4 litre and one a 3.6 litre.

– the great thing about running lpg ,apart from it being 69 pence per litre as opposed to 1.40 a litre for petrol , is that the emission rules are 4% co and 1200ppm hc .this makes it very easy to get through . my present runabout ,a diy turbo 1.4 astra estate running solely lpg, was 0.85% co and 341 ppm hc . and thats just a crude system .

to get it on the rd , because I have the v5 for the chassis in my name ,and I will retain the 8 point necessary to get it iva/uva exempt , it will nedd a simple visual to show I have retained the chassis as is and suspension etc . and that should be it . it will then be renamed in the v5 by dvla.

– re danger , my bike is around 768 bhp/ton .my Austin min is 406/ton ,and so on , im fairly used to violent machines lol. this will be my first personal non turbo project in years . im trying to devise a rotary valve so I can have proper 12 cylinder flamage out the top!! oh yes .

my dream is to have a picture of the car , in the dusk , totally sideways with smoke pouring off the tyres ,and twelve stacks of flame jetting up in the air ..then I will be wearing a smoking jacket,a fez ,and a pencil moustache , smoking a hookah . still trying to book my Canadian model for the passenger seat in a flapper dress and pearls . 😀

are you running through a reduction drive ,? if so that will drop your tq by the ratio , if its a 3;1 then down to a paltry 500 lbs ft , if a 2;1 then a grunty 750 .

I think we need to book a drag race? we should be able to obliterate the track with tyre smoke whilst just sitting there ….sniggering .

– yup you’re right, a twin starter would be most effective …the way I see it , this starter ,off a transit diesel with a 20:1 cr , should hopefully cope well with the jags 10:1 odd. it appears to be much heavier duty than a petrol starter ,much heavier teeth and flywheel diameter. my only concern is if it won’t spin fast enough …time will tell.

– in fact I may use 7.50 16 tyres due to the huge expense of going proper vintage spokeyness . and the highest speed rating I can find on those is around 100mph odd . so yes spectacle and drama is the path . something to bear in mind is , your drive train only has to cope with what the tyres can hold . so even if you had 2000 lb/ft ,if the tyres can only hold 250 lb/ft ,then that’s the drivetrain max load .