RB20 or RB25 running triple webbers???? In a Datsun 240Z

[hunter]

Do you have a solution for running triple webbers on a RB20 or RB25?

here is a link to my post that is on auszcar.com It is an Australia wide car club for the S30 or Datsun 240Z 260Z 280ZX
The below post contains the reasons I want this conversion.
Also pics of this conversion that have been done mainly in Japan.

http://www.viczcar.com/forum/index.php/ ... 853.0.html

[hunter]

anyone?

[NITROPIXIE]

Hi hunter and welcome to the forum

There is no plug and play system to achieve what you are after but it can be done. The most difficult thing would be mounting a 36-1 triggerwheel to the crankshaft.

As for load sensing there are 2 methods, TPS or MAP. TPS would be more simple as there is a TPS available for webers. With MAP you would have to have 6 vacuum ports all running to a smoothing reservoir then onto the MAP sensor in order to reduce the amount pulsing sensed at the MAP sensor during low revs.

Hope this helps a little and come back with anymore questions.

[hunter]

I am used to running the L series engine, With the fuel injected L series engines it is just a matter of unbolting the fuel injection and bolting the carbs onto the motor.

I have installed a RB25DET intalled in one of my zeds.

I am not familiar with what would be involved with carbs on an RB engine .

Basically what I need to know is how much it will cost and how much is involved to install.

Now what would give me better results? MAP or TPS

I am thinking of installing a airbox on the webbers to make it look closer to the S20 Z432engine. If I were to run the MAP sensor off the air box would this not give me a smoother signal? or would I still need a smoothing reservoir.

Instead of using a 36-1 trigger wheel on the crankshaft, can the CAS give a signal to run the spark?

There is a fairly lengthy discussion in the post below about what I want to achieve with a few pics of cars in japan with this conversion done.
http://www.viczcar.com/forum/index.php/ ... 853.0.html

[hunter]

by the way thanks for the welcome and sorry for putting my first post in the wrong section, I am un familiar with this forum.

Cheers

[DannyP]

The MAP sensor MUST be plumbed on the engine side of the throttle plates. It must be somewhere in the intake manifold. If you have 6 Webers, just use a TPS. My engine has 4 Weber throats, and the carbs are oon opposite sides of the engine, all with individual runners. One TPS mount and it was done, no vacuum leaks to think about.

[hunter]

ok thanks for that danny, either way gives you the same relults I am guessing?

[NITROPIXIE]

It gives similar results. The best option i believe is MAP as it senses the load of the engine and so alters the advance to this variable. TPS is generally used with engines that are a little too cammy and don't give reliable MAP values to utilise a MAP sensor. MAP sensors are a must on forced induction but not so NA engines.

If you purchased a MAP megajolt and decided you then wanted to go TPS then it can easily be changed with just a few resistors soldered onto the board.

[hunter]

So basically what I will need is:

$161.95 Megajolt Lite Jr.
$15.00 Ford EDIS Module.
?????? 36-1 Trigger wheel.
Coil pack on my RB25, can I use this?

FOR MAP
Hoses to run MAP sensor
Fittings to mount vacuum hoses onto runners.
Vacuum smoothing chamber

FOR TPS
TPS to suit webers

Also with the trigger wheel does it matter if it is mounted on the front or back of the harmonic balacer?
As long as the sensor from the EDIS is mounted in the correct position to pick up on the Trigger Wheel it should work?

[NITROPIXIE]

For the coil pack, its best to stick with the OE ones for the EDIS system, as the EDIS is programmed for the correct amount of dwell for the coil pack. Then obviously some ht leads to suit. People have used the vehicles original coil pack to great success, so there would be no harm to try this, but it is something you should be aware of. I have done this on a Peugeot 205 in the past.

With the triggerwheel its best to have it solid mounted to the crankshaft in my opinion. Again, others have mounted it to the harmonic balancer but the trouble being is if there is any movement of the crankshaft harmonic balancer then you wont get dead accurate timing. I have used a harmonic balancer but i welded it so it could no longer move. I deal if you have a spare one kicking around.

It doesn't matter where it is located on the front or the back of the harmonic balancer, but some things to keep in mind are ease of changing the fan belt and length of VR sensor mount. The shorter the better as it is less prone to vibration, which can be a problem.

So long as when the engine is at TDC, the trigger wheel sensor is in the correct position in relation to the triggerwheel then it should be fine. If by mistake you have the triggerwheel 180 degrees out in relation to the VR sensor at TDC then you can simply swap the LT wires over to the coil pack.

Hope this helps somewhat.

[Spockie-Tech]

Hi Ryan and Hunter.

Sorry to butt in, but I'd reccomend against using the factory Ford EDIS Coil Pack down here in Australia.

Since we didnt have any locally released cars that used that style of pack, Ignition leads that fit the ring-lock terminals on the Factory EDIS pack are very hard to come by.

Instead, I have been using the Holden V6 style packs with great success.. I've done about 4 Megajolt installs with them so far and they are all running fine. Plus they are still available as new parts from Holden or Accell (which look exactly the same, but yellow). Leads are available everywhere in all lengths

The only drawback is you need to fuss about a bit making a mounting plate for the packs.. (The Factory mount plate is big, ugly, and has some weird blob of goo-immersed circuitry built into it).. they come as individually mounted units (1 coil per 2 cylinders) with 2 small diameter bolts holding them down and 2 spade-style sockets on the back for the electrical connection.

I use a plate of 6mm aluminium, cut to size, drill the mounting and electrical connection holes. Wire and push the spades into the sockets from the back through the plate, and then fill the wire-socket-holes with Araldite to hold the spades in place if you need to pop a coil off in future.

I'll be making another one in the next couple of weeks for my Triple-Weber'ed 265 Hemi thats about to get dialled in on an Engine Dyno, so I'll see if I can snap some pic's of how I make the mounting plate for you.

I'm really looking forward to seeing how much improvement the Megajolt will make to the Hemi, since they suffer from notorious spark scatter due to their "distributor driven from the rear of the sloppy chain-driven cam"..

Also with a tuned independent-runner ram-induction system like Triple Webers, there are likely several points in the RPM range where the induction system all starts humming away in sync, volumetric-efficiency goes up (past 100% if some weber info is to be believed), and I'm guessing the ability to pull a bit of spark advance back just at those rpms, without affecting the other lower-V.E. rpm points (something a mech dizzy cant do) will smooth out the torque curve significantly.

regards

Brett

[hunter]

Welding the harmonic balancer to the crank would not be ideal for me. As I would have to remove it to change the timing belt etc down the track. Even though it does have a fresh 100000 service kit installed at the moment.

With the timing belt off the crank shaft sproket. the sproket does have half a tooth play, but a new key may fix this. There is no noticeable play when the new timing belt is installed. RB engines supposidly have this problem from what I have heard from other people.

I think mounting the trigger wheel to my harmonic balancer is my only option.

Spockie I will look forward to seeing some pics of the holden coil pack.

Is there any specs on my current RB25 coil pack I should research for compatibility?

[hunter]

I am in Tasmania by the way

[Spockie-Tech]

I'm in Melbourne, Australia.. Close compared to the rest of the guys on here, but still a bit of a swim

You can see some closeups of the holden coil packs in a 4-cylinder configuration that I put on my Gemini (daily driver) here
http://www.autosportlabs.org/viewtopic.php?t=2705

I should have the 6 Cyl Hemi Coil Pack Plate made up this or next week if all goes to plan.. I'll get some pics and vids of us giving the Hemi a good caning on the pump and see what we can squeeze out it with the Megajolt. It made 280hp on a 4barrel some years back. I'm hoping for 300-320 with the the webers and bit of a broader-torque-curve (not peaky) cam.. They're factory-ish numbers.. if I get any more I'll be over the moon,. it would be nice to think the megajolt could pick up another 5 or 10% neddies by keeping the sparks in the right plance and time better than the mech dizzy could manage.. but we'll see.

I think the main thing you want to look for is to make sure they are "dumb" coils - ie, do not have internal driver ("Igniter") circuitry as some late model coils do... and that the primary coil resistance is approximately the same ohms (I forget the value - anyone ?) so you know that the EDIS module can drive the coil to near saturation without overloading the output transistors.

[hunter]

I have been told it has wasted spark coil pack (3 coils)