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Dax Rush ( 7 type kitcar ) with Suzuki RF900 engine

Posted: Sun Nov 13, 2005 3:42 pm
by MartinBright
Name: Martin
Vehicle: r/2003 DJ Sportscars Dax RushMC
Engine: Suzuki RF900RT 937cc Dax SS Exhaust 4 cylinder 4valve/cyl standard coils (wasted spark).
Injection: Port GSXR600K1 TBS, 240cc (I think) modified 80mm-94-80mm spacing
Description: Seven Type Kitcar fitted with a Suzuki RF900RT Bike engine.
Using a set of GSXR600K1 throttle bodies with an extra 14mm spacing between the centre 2 bodies.
GSX1400 Fuel pump fitted to a homemade Stainless Tank which doubles as a swirlpot.
Suzuki bike pumps fit in the tank and are complete with pump/43.5 psi regulator and filters.


After blowing up the opto 4N25. (400volt spikes on the coil ) I made a wasted spark coil interface board.
(on stripboard at the moment) to the Coil Input (Pin24).
This gave me a fairly clean 12V pulse
I conected 2x 1N4007 Diodes to each coil pack and connected them to a 100Ohm pullup resistor one end to 12v (Ignition)
The output was then connected to the Megasquirt Pin 24 coil input.

Then to starting the engine. 1st attempts. It fired but soon stopped.
I used to Megatune to calclate the initail value of ReqFuel as follows:-
2 squits/alternating 4cylinders 4injectors 4stroke port injection.
Req/Fuel 937cc, 4 cylinders, 240cc injectors and A/F ratio of 14:1 (slightly rich)
Which came to 6.9
After playing with the the setup I got it to idle well engough to balance the butterflies.
But I had to increased the Req Fuel from 6.9 to 13
I did incease the warmup enrichments slightly before this but had little effect.

Once the Idle was running smoothly (not calibrated to and Lambda settings yet) I tried blipping the throttle and it revved up cleanly.
Pleasing result for just 1 hour of playing.
I now seem to have the common problem using ITB's of 65-70Kpa MAP at idle.
so if I can't get it running better I may try the Hybrid AlphaN function on MS extra.

Website: [url] ... ushmc.html

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