IgnaTech on a breathed on 2V engine

[RichardDDuke]

Am seriously thinking about using an Ignatech unit on my big-bore (944) '94 900 engine, and was wondering whether or not to order either a TPS unit to it or an air flow sensor to go with it.

Do either of these extras (TPS and AFS) help, or is just the IgnaTech unit happy to run without ?

Engine will be running with K&N filters on 39mm FCRs and a free-flowing (open ) exhaust.

[Dukedesmo]

I have the Ignitech setup on mine (944cc) along with FCR 41 carbs. Originally without a TPS and whilst it worked well, the throttle was very on/off particularly noticeable at low RPM and low speed city style riding (just when you want to be smooth).

Fitting a TPS to one of the carbs made it much smoother, more controllable and a big improvement for not a lot of money either.

So my advice is, yes go for it.

[900Rebuilder]

Cant directly help as mine is in bits at present but seriously tempted to find the Mikuni TPS for mine and fit that before it gets mapped as the ignition can run one.

I have the 40mm TDMR carbs as I wanted the luxury of the choke for more everyday use.

[Dukedesmo]

IMHO the reason the TPS works so well is that, although the map for the ignitech is programmable by RPM or RPM and TPS, if you programme by RPM alone then the transition between advance happens too intermittently/randomly when around the RPM switch point due to the engine RPM 'fluctuation' during the cycle.

If you watch the rev counter (the digital one in the Ignitech software) you will see the numbers fluctuating from cycle to cycle at steady throttle, especially at lower RPM due to the uneven firing sequence and this is worsened by having a light flywheel as mine does.

So, if you are switching from say, a 5 degrees advance to 8 degrees at 1500 RPM then what happens around that speed is the ignition switches randomly between advances causing it to be a bit on/off, in my experience.

Adding a TPS to the equation makes things more reliable due to not relying on just the fluctuating RPM reading but also the throttle position which will remain steady at steady throttle and not subject to 'pulsing' whilst the engine is running plus, cracking open the throttle will give you more advance, quicker.

If you have the Ignitech programme, open up a map and then switch between 'only RPM' and 'RPM and TPS' especially in 3D mode for a good representation.

I have switched between an RPM only and RPM and TPS programme in the bike, back to back and can definitely say it is an improvement at low speed running, no real difference at higher speeds as you're already at maximum advance anyway.

Don't know what an air flow sensor might add, if anything?

[Darren69]

I was wondering about the air flow sensor too, unless it's just providing backup to the TPS? Or is it if you can't fit a TPS that would make sense.

[Dukedesmo]

I would think an airflow sensor would be affected by the large pulses of air in the same way that RPM readings are, again particularly at lower speeds also I don't think the Ignitech has any input for such a sensor to be tied into the mapping?

[Darren69]

If they have that as an option maybe intended or would work better for the in line four guys with CV carbs? I'm not Ignitech savvy so I couldn't really say. TPS will work better I'm sure.

[RichardDDuke]

Thanks for your help in this manner. Wasn't sure about which option would be best so asked for people's opinion on both TPS and AFS.
Looks like I'll be getting contact with IgnaTech regarding getting an order sorted.

P.S. I might ask for some advice later when getting it set up, but hopefully all will go ok ....

[RichardDDuke]

I've been in contact with IgniTech and they are suggesting that the IAPS (inlet air pressure sensor) would be easier to fit than the Keihin FCR TPS route.

Does anyone have any advice as to how difficult fitting TPS to Keihin FCR carbs is, and whether I should simply take the "easy route" and go with what Ignitech suggests with the IAPS ?

Thanks (as ever) in advance ...

[Dukedesmo]

Originally Posted by RichardDDuke

Does anyone have any advice as to how difficult fitting TPS to Keihin FCR carbs is, and whether I should simply take the "easy route" and go with what Ignitech suggests with the IAPS ?

Fitting the TPS is fairly simple, don't know if you have banked carbs or singles? but either way you fit the TPS on the end of the throttle shaft but the shaft is not long enough so you need to buy a longer shaft that sticks out the end - at least you do with the single carbs, banked maybe different?.

I got the TPS, the longer shaft and a TPS mounting bracket from Frank MX in the Netherlands; https://www.frankmxparts.com/ but in the end I didn't use the bracket as I thought it a bit flimsy for my setup, so I made my own from a thick piece of aluminium (the pictures above show the assembly procedure).

Once fitted, the calibration is easy - simply go to the Ignitech programme and set 0 TPS when the throttle is shut.

I can't comment on the IAPS and I wonder it it might depend on whether you have an airbox or not? but I would expect it to fluctuate in sync with the engine speed, whereas the TPS will stay steady?

[RichardDDuke]

DD,
Thanks for the reply. Having looked at your earlier photos I could see the Al bracket and hoped it was a standard part as it looked professional. Do you have the dimensions or a drawing for the plate so I can get one made ?

I'll have another look at the Frank MX website for the TPS and longer shaft, but last time I looked the TPS unit was out of stock and no due date either. If Frank MX still don't have the TPS, then I'll get one from IgniTech as well as the TCIP4 and associated connectors and just get the longer shaft from Frank MX. Hopefully swapping the shafts is a simple task.

The carbs on my bike are banked and I've got K&N pod filters fitted. I used to have a Scott chain oiler fitted (now removed) so there's already a handy feed for an air input sensor, so it'll be an easy job if I do go down that route.

[Dukedesmo]

My TPS is a Keihin branded part and came with the electrical connectors and Keihin mounting bracket, not sure if others would fit as easily?

I made the Ally bracket because, due to the position of the TPS on the side of the carb, between the two where I have numerous cables etc. I felt the supplied bracket was too flimsy, being held with just one bolt but that's probably overkill on my part? I had the ally lying around and it cost me nothing to make something thicker so I did.

To fit the TPS I needed a longer shaft that sticks out the end of the carb and that has a groove in it for the TPS to locate and there is a 5mm threaded hole for the bracket by the shaft as per;



Removing the original shaft is a simple strip down job but I had to change the end bearing for an open version rather than the sealed original, see the original shaft, sealed bearing and TPS bracket here;



You can see where the bracket fits in the pic of the carb, using the one 5mm locating screw where my bracket adds a second, 6mm screw on an extra 'leg' in an otherwise redundant hole (I think there for joining carbs when using a banked setup?) and is made from thicker material;



The Keihin bracket is functionally the same and made from steel rather than ally so plenty strong enough but I like 'belt and braces' and wanted to add an extra support, I did consider adding a brace to it but decided it was easier to use it as a template to make a new bracket with the brace built in and the thick ally plate (needed the counterbore due to the thickness) was a convenient way of making it.

The bearings are widely available and only cost a couple of quid IIRC so no bother there.*

I've not seen the banked carbs close up so don't know what the shaft setup is? (one long shaft or two shorter but linked?) there may even be provision for the TPS? presumably it will go on the end of the bank which maybe a 'safer' position than on mine which has cable assemblies on both sides due to the carbs being split-singles?

In fact, I wonder if the bracket was made for a banked setup rather than a single and may be a better fit on them?

If you go down the TPS route and if it's any help you're welcome to the bracket as I won't be needing it.

*Edited to add, open bearing here; https://simplybearings.co.uk/shop/p8...duct_info.html