S12OC UK Forum - FJ20 with Bike Carbs

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- - FJ20 with Bike Carbs (http://nissansilvia.co.uk//showthread.php?t=5757)

ok from what ive read it will fit but it will either be tight for space or difficult to fit engine....
still after fj20 bonnet anyone kinda desperate for one

and i also believe bens fj is a turboed one so the intake maybe smaller?
my one is an na one

have you tried to fit the engine with the manifold yet ?

Nop, weather not great at the moment but measurements show it will be a tight fit (cant remember measurements of the top of my head) and i know someone else who tried it and said it was a difficult fit

Quote:

Originally Posted by nedge2k (Post 39512)

Bogg brothers are well known in the NA world for fabricating manifolds for bike carbs and bodies. you see it a lot on the C20XE and the like. Its not the proper way to do it but it works.

Not sure on the FJ setup but the dizzy on the CA is not a "proper" dizzy - it has what is essentially a crank sensor in it which the factory ECU uses to fire the coil so if you were hoping to ditch the factory ECU and run carbs, you'll still need something like a DTA S40i to control the ignition timing. The C20XE has a similar setup but uses a proper crank sensor - people often replace the XE 16v dizzy with a "proper" 8v points dizzy when converting to bike carbs.

Throttle position sensors are usually used for calculating engine load in an EFI setup but to be honest it can be left disconnected in an ignition-only ECU.

So in short, you need an ECU or a proper dizzy from another Nissan that will fit the FJ. Either way you'd need it all setup on a dyno / RR and using a "proper" dizzy from another engine may have mixed results as the ignition curve will be different - but this is usually just controlled by weights and springs or vacuum.

If you want to do it properly, get some jenvey SF ITBs, a DTA S40, a fabricated manifold and mount a 138mm trigger disc and ford type crank sensor to the front of the engine (or get the flywheel "toothed" and mount a sensor in the bellhousing).

nice info there

Quote:

Originally Posted by nedge2k (Post 39512)

if you were hoping to ditch the factory ECU and run carbs, you'll still need something like a DTA S40i to control the ignition timing.

You are saying you need something to control the ignition timing. But the L Series from the Datsun 240z run carbs and no ecu and nothing electric to control the ignition timing and i know that for a fact as my cousin owns one.
So why would you need something to control the ignition timing on the fj20.

The FJ dizzy controls the timing, with bobweights like an L-series one did. The ECU does fueling only.

Only the FJ20ET uses the ECU to control the timing and it uses the dizzy as the crank (360 slots and optical sensor) and cam (four slots of differing widths and a second optical sensor).

The FJ24 came from the factory with Solex 50mm carbs and a normal dizzy of course.

With some fabrication, BMW E30 M3 throttle bodies can be made to fit but the stock injection won't work with them. In that case it would then be worth fitting something like a DTA.

I have some parts I can take pictures of if you want me to?

Hi mate
Do you have an FJ then?

I have a few engines and lots of bits but only one in a car at present.
I have had several over the years. I did circuit race a Gazelle RS/X for a little while.

What are you using the FJ for? What chassis is it in, an S12?

I've got a spare S12 inlet manifold I'm sure if you just want to EFI it. ITBs are going to be expensive whichever way you go about doing it.