johnisenglish

I've been avidly reading this forum for several months, and I've been buying parts for a 20B swap into my FD for just as long, but there a few nagging questions that I haven't been able to find answers to yet. I'm just trying to work as much out in my head as possible, in an effort to save myself some trouble once I get down and dirty. That said:

Does the stock 20B turbo manifold downpipe flange match the downpipe flange from the 13BREW? I know that even if it did, a stock FD downpipe would still have to be modified, but that'll save me the time to make a flange when I'm fabbing a downpipe up

What is the firing order of the rotors? I know they're 120 degrees apart, but is it 1 - 3 - 2?

I plan on using the stock 20B front plate, but what does that mean in terms of pulleys? I can use a pulley kit for an FD without any trouble? (That's really just a hypothetical question, but I'm curious nonetheless).

With Haltech E11, you have four programmable outputs (PWM 3 and 4 and AUX 1 and 2) that can be setup as VTEC outputs, and thus based off of load and rpm. Couldn't these be used to control the solenoids necessary to get the stock turbos to run in sequential mode? I don't see why it couldn't, and I'm planning on giving it a shot (despite all the issues I've had with running sequential in my stock FD), but so far I keep reading on this forum that only the stock Cosmo ECU can run the turbo in sequential.

Whats the deal with the crank trigger? I've read several conflicting posts about it, so what exactly do I set it up as under Haltech? I'd prefer to use the stock unit, since its already there...

RETed

I think the shape is the same, but the bolt pattern is different.  I think the FD bolt pattern has an extra bolt (or the other way around).

Quote:

[B}What is the firing order of the rotors? I know they're 120 degrees apart, but is it 1 - 3 - 2?

Ours fires 1-2-3.


A whole FD front "section" (i.e. water pump housing, water pump, pulleys can be used; you'll need to pull and replace the water pump housing studs, as the stock 20B ones are longer (like the FC ones).  The same can be said with a full FC front "section".

If you're going to do through all this trouble, you might as well go single turbo...


The 20B CAS is identical to the FC CAS.  It fires the same as a "Mazda multi-tooth".


-Ted

johnisenglish

Thanks for the fast reply!

So the firing angles for the rotors are 0 - 120 - 240, correct?

For using an FD "front section," an FD water pump, water pump housing, thermostat, main pully, and alternator would work, correct? I've heard that there's an issue with the position of the alternator, (I'm also planning on keeping A/C and P/S, just to make things easy ), so perhaps its not worth my effort to switch things around and I'll just keep the Cosmo water pump and modify the Cosmo thermostat housing.

As far as the sequential setup goes, the idea is appealing to me because running the 20B with the stock twins in sequential offers an even broader powerband then using the stock twins in parrallel. A single trouble would ceraintly open the door for making gobs more high end power, but that not what I'm looking for, at least not while I'm still running stock ports and dealing with just getting the engine mounted in the car and running. A besides, setting up four solenoids and the corresponding vacuum work is nothing compared to the full hose job for the FD (which I did last month), not to mention the rest of the 20B swap...

t-von

iTrader: (8)

If you use the Fd water pump and housing you will have to remove the upper filler neck. Thats the part that hits the hood if you are using a Pettit style subframe.

j9fd3s

iTrader: (3)

k2rd makes both flanges for the stock dp.

you could run sequential, but its an extra hassle to setup and tune. you can basically set it up like the fd, except the cosmo transitions around 3500rpms, and it should work.

if you think the fd rack was complex you have another thing coming with the cosmo one....

RETed

For a 0-360 complete cycle, yes, that is correct.


-Ted

Jeff20B

iTrader: (13)

I don't mean to confuse anyone here, but you know how the FC and FD fire their leading plugs twice per rotor face? How do you think that could be accomplished on a 20B?

johnisenglish

I was actually wondering the same thing. I know its not nessicary, but if its offers a more complete combustion and helps me pass the sniffer test for emissions I'm all for it.

I understand how split can done though the E11, but I don't know how one would go about doing that in the software, if its even possible?

j9fd3s

iTrader: (3)

if you set it up like the instructions it will run an l&t split. i guess you could setup the 0-120-240 screen wierd so that the t fired the second time, but i really dont see what the point of that would be.

johnisenglish

The stock FD and FC ignition systems fire the leading a second time, after the tailing fires and as the tailing apex seal is about to pass over it to create a more complete combustion. I'm not sure if there's any power to be gained from it, but I do know that it helps at least somewhat with emissions. However, I really haven't seen much said about it with either the 13B or 20B in terms of tuning with non-stock ECU's, so I don't think its of terribly high importance.

j9fd3s

iTrader: (3)

i dont think it matters, and it would be a lot of work to do on the 20b, because you cant waste spark it, like you can with a 2 rotor.

RETed

You can't do that.
If you want leading + trailing for all 3 rotors, you need 6 discrete ignition channels.


-Ted

johnisenglish

Having split timing isn't the issue though - that can fairly easily be accomplished with the AEM EMS, Haltech E11, Microtech somethingoranother, etc, its having the leading plug fire right before the trailing apex seal passes over it thats in question.

Jeff20B

iTrader: (13)

I have a modified FB distributor on my 20B that will fire each leading plug at its normal time and also right before the apex seal passes over it, like the FC and FD.

I've noticed a substantial improvement on my REPUs and Cosmo with two leading sparks per rotor face, so I figured I'd give it a try on my 20B.

The basic timing on the leading plugs of a stock or aftermarket ECU set to run a 20B is:

1=0
2=120
3=240

Pretty simple.

I'm going to try my luck with:

1=0
3=60
2=120
1=180
3=240
2=300

Oh, and my stock 4 cylinder tach will work fine without modification.

j9fd3s

iTrader: (3)

this is opinion but i think mazda wastsparked the fc because that way they can buy 1 coil, and use 1 output from the ecu. remember they really went out of thier way to maximise the really slow ecu instead of buying the faster one. the fd is also ecu limited

Jeff20B

iTrader: (13)

The Eurospec FC had an FB style distributor; at least at first.

j9fd3s

iTrader: (3)

and the nuclear reactor, their s4 smog system is like our 79....

Jeff20B

iTrader: (13)

No way! That's disturbing. It would mean the trailing ignition would probably be semi-firing, with the tach hooked to the leading coil. Man, DLIDFIS would be great on one of those cars, I'd think.