CDI vs TDI

[Boneswig]

Did a lot of reading lately. Everywhere it is said that a CDI and a TDI are not the same. Can anyone explain to me what the difference is. What I have read, they both do exactly the same thing but noone can explain as to why you cannot fit a CDI in a TDI's place.

[IanDMacDonald]

Well, if you researched CDI vs. TDI, I highly doubt you found any similarities, Let alone TCI

No, they are different ignition systems. Polar opposite actually. You'll find CDI's on higher revving bikes, vs. TCI that voltage falls off after certain revs. Plus, CDI's have consensers to store energy, where-as TCI's are just transistors in-place of points. There is much more different between the two, but that's the short & sweet on it. Every forum has a thread on it.

[TopCatGr58]

Hey Bones,

Like Ian and you both stated, they control ignition, but are quite different in how they do it. I don't know the inticracies involved. But I do know that you can't use the coils designed for a CDI on our TCI machine.....they have too low primary resistance.....ie. 0.7 ohms vs. the 1.5-3.0 ohms our bikes have/use. If you use them, you'll burn up the TCI fairly quickly.

T.C.

[3Phase]

Bones,

Don't mix the two types of ignitions.

A regular ignition coil has too much internal resistance and is designed to operate at 12V DC. and it won't be able to handle the hundreds of volts from the capacitor that will destroy the coil.

A CDI ignition coil has very low resistance to handle the huge inrush current from a capacitor and it's designed to handle hundreds of Volts. A CDI coil will burn up old style ignition points or the transistors in a TCI.


TCI (Transistor Controlled Ignition) is like the old-style points and condenser. The 12V ignition coils are on all the time until the points open or the transistor turns off the circuit, then the coil makes a long spark to light off the fuel.

TCI and points and condenser ignition coils are fairly large with some resistance to keep them from burning up by being on all the time while they build and store energy until it can be released to fire the spark plugs.


CDI (Capacitive Discharge Ignition) is the opposite, it's off and there is no voltage to the coils until the controller tells it to fire, then a capacitor dumps current through the ignition coil at several hundred volts and
BANG!

CDI makes a very fast spark so the controller usually fires it multiple times at lower engine RPM to make sure the fuel lights on fire and stays on fire.

CDI ignition coils can be very small because they're usually off most the time and they must have low resistance so the current from the capacitor can create the magnetic field as quickly as possible to fire the spark plugs.



.

[Boneswig]

Ok so if I change the coils and change to cdi it will work? If you guys remember correctly I am busy with the bobber. I know the original XS has a tci and is why I went reading up on everything but all I could find was a curcuit diagram for a cdi, and no where for a tdi. A friend of mine is building a "controller" box for me which will have everything in one and wil fit perfectly under my seat. Inside the controller will be my static relays, cdi's, voltage reg & rec, and and and. He wants to close the whole thing (heatsink outsde) and then light it up with LED's. All sound like a great plan, was just worried about the cdi vs tdi thing. So I will be using two cdi's and then suppressor cap coils (don't know if that is the right name for them, but are found on the newer bikes where each plug has his own coil inside the suppressor cap. So my question is, will this work?

[3Phase]

... So my question is, will this work?

If your friend builds it for you? Maybe. You haven't shown a schematic, the actual parts your friend will be using or the design for the CDI.

CDI voltage and current is dangerous. Homebrewed CDI and gasoline could be a lot of fun for everyone outside of the blast zone. There's no way to know if it will work, burn up the parts, kill you and anyone else with fifty meters of your bobber when you try to fire it up or if it will do all of that at the same time.

.

[Boneswig]

Ok I'm more into PCL's than electronics. But here is what I understood from him. There wil be a 12? Section and a 220v section. They will be isolated. Then there will be the trigger side, and the the coil side. He actually recommende denzo suppressor coil caps with some specific rating when he showed me the list. So what he told me is that the voltage from the stator cannot be used because it is not a constant supply, so there is a stepup transformer from the battery to have a contant 220v (as per his calculations). I do remember him mentioning a mosfet ic but numbers of it is a mystery. I however will build a simple 555 flasher relay for my indicators and the wil build SSR's for my driving lights etc. That's more my field of work. I am just worried I am paying the guy for the work and then its a failure. Then I would rather aim for another solution to the problem. I have found a TCI in bloemfontein (600km from me) for some rediculous price. To be honest I can buy a power commander for my ex-up for that price and then there is no guarentee that it is a working TCI. If there is a possibility that it will work, I can tell him I'll pay after testing on the "control" box. I will try and get the diagram from him and run it by you guys.

[Boneswig]

Just had a chat with Frank. He gave me the following web address. He says its basically the same thing he will be building except it wil be tw next to each other to accomodate both pickups.

http://homemadecircuitsandschematics...discharge.html

Will you guys have a look at it and tell me what you think please?

[TopCatGr58]

An alternative approach!

Hey there Bones,

Okay, I went back and looked at your first thread....saw that you said that the bike was an 81SH frame...but it's a Euro/African XS 1.1 , but your profile or signature doesn't specifically state the year, so it will help us in the future if you will edit your profile/signature adding the year.

Next, you're looking at replacing the ignition TCI....so I have to assume that yours is bad or non-existent??? If it truly is the 81 series then it has/had the 4R0/4R1 style of TCI which Yamaha made programming the cent. adv. curves into the TCI, but still uses the Vac. Adv. pot.. This is why there are no mechanical cent. adv. parts on it.

SO...If the TCI is bad(not easily repaired IF the IC's are damaged), but sometimes it's just the solder joints to PCB and external plug are corroded, etc., and can sometimes be fixed by just resweating the joints! But if it's truly damaged...and as you've stated, the next nearest unit is some several hundred clicks away....and you will have to verify that it's the same type of TCI...Yamaha made 3 types. 78-80 is the 2H7 which is a fairly simple triggering system and utilizes both mech. cent. adv. and vac. adv. parts.
The 81 as stated earlier has programmed cent. adv., uses the vac. adv..The 82-84XJ is the 10M series, and has both cent. and vac. adv. curves programmed into it, and uses just a vac. sensor to provide input data to it for monitoring and control, and NO mech. timing parts aside from just the PU coils and trigger shaft.

This CDi project seems like you're trying to build a space ship to throw a rock!
Both expensive and complex and as Scott stated dangerous!

A simpler way to replace your ignition control box TCI would be to convert the 81's timing parts into the simpler 78-80 series parts by adding the mech. cent. adv. along with the vac. adv. components. THEN you can build your OWN SIMPLE TCI triggering device that uses relatively cheap and easily attained AUTOMOTIVE ignition components, along with standard ignition coils/wires/plugs....but you could always spring for the HI POWER 30+KV style coils ie. Accel/DynaTek.

Here's the link on our site about how to build your own TCI from auto parts.

http://www.xs11.com/forum/showthread.php?t=9753

You might be able to find some other folks with broken 78-80 series XS11's for harvesting the Mech. Centrifugal Adv. components locally and at a modest price!

That's my 2 cents!

T.C.

[3Phase]

If you really do have an 1981 XS11 with no mechanical advance, the engine will run without a mechanical advance but you will not like it. You need a to find a mechanical advance for the earlier XS1100s.

I agree with T.C., you're making this way too complicated. Don't try to reinvent the wheel. The CDI your friend Frank is planning to build will probably work but how are you going to fix it when it stops working while you're out riding? All of the surviving auto and motorcycle manufacturers have spent a lot of money to make ignition parts that can run 24/7/365, rain or shine, hot or cold. Pick a system and install it.

I think you had a VW ignition you were thinking of using but you can also use two of the billions of GM ignition modules scattered all over the planet like the ones T.C. linked to in the Tech Tip.

It might be a little tight but you could also use a pair of old Chrysler electronic ignition boxes. They're designed to work with 150 Ohm to 900 Ohm pick-up coils and the XS11 uses 720 Ohm coils.

Have fun!

.

[Boneswig]

There is a vacuum unit on the bike, will check if it has the centrifugal unit in as well. Unfortunately I did not get a tci with the bike. I basically saved her out of a garage who was about to chop her up and throw her away for scrap metal. Once the ignition part is solved all I am short is the starter and she will be ready. I did the topend, cleaned out everything possible. Did the carb's, did the intake rubbers, did the frame. Electrical I'd almost done and then its just ignition and starter. I'll only be able to check the gears once she is running. Once she is running I can start wih the fibreglass side panels and the spray work. I made it a 2 months project and think I'm getting over eager now. I'll pull the pickup unit tomorrow and see if it has the weights etc. I traced het to a 81 according to the engine number and after doing the frame found that the motor and frame is matching........will slow down a bit. Might have to extend my deadline with a month.

[3Phase]

Bones,

The vacuum advance is not the same as the mechanical advance and you need both of them. The mechanical advance changes the ignition timing based on engine RPM, the vacuum advance changes it according to engine load so you don't need your own personal oil well to feed your bike.

As T.C. said, there is a special one-year-only TCI for the 1981 XS11s. It's fairly rare and it's usually expensive but it does the ignition advance electronically instead of using the earlier mechanical advance with weights and springs. I just checked eBay and there isn't one up for sale today.

You can use the mechanical advance from a 1978 to 1980 XS1100 to replace the 1981 ignition reluctor/trigger assembly, then you can use the earlier -- and much less rare and expensive -- Yamaha 2H7 XS1100 TCI or you can roll your own ignition controller.

Here's one for a 1979 XS1100 Special:-
http://www.ebay.ie/itm/YAMAHA-XS1100...-/121162390214

Here is the 1979 TCI:-

http://www.ebay.ie/itm/YAMAHA-1979-X...-/131572012165

I think the 1981 has a full Timing Wheel but here is a 1979 Timing Wheel:-
http://www.ebay.ie/itm/YAMAHA-1979-X...-/131572040219

.

[Boneswig]

Finally a break!!! Got hold of a guy about 8 miles from me. His words "you can take anything XS in my garage, don't have one anymore" amongst the stuff he told me about, is a '81 TCI. I will know by the weekend if he has a starter as well. Sooooooo she will be starting this weekend if there is a starter.