New to EFI - few questions

[motthomas]

Hi guys,

I'm new to this EFI thing so trying to learn a few bits before actualy putting it into practice. I own an mc22 Honda CBR250RR which is currently carburetted as standard. A few years ago I came across a website where a few guys allegedly attempted to fuel inject the earlier model CBR250 (mc19) by building an ecu from scratch and writing the code etc. While this is way out of my league, it got me thinking about what it would be like to EFI the 250. Its a small, extremely high-revving IL4 engine in a pretty light and nimble frame. They are capable and responsive as they are but what if you could successfully EFI it?! After discovering Megasquirt I think it is about as accessible as it can get now. Programming I can deal with, that level of electronics... no!

Anyway, few issues... Most of my questions are hardware related since the manual pretty much answers all my software questions for now anyway!

The first is the rev range. I think after some research I have found the answer to this. The megatune code only allows for a redline rpm of 15,000. The mc22 revs out at 19,000rpm. I believe the megasquirt ecu can handle the rpm but the code cant but that I can change the .ini file to increase the max rpm. I have done this but cant test it without the unit. Has anyone done this successfully?

The second issue is throttle bodies. I would prefer to run an ITB setup as all bikes I see have ITB and the mc22 currently has individual carbs so I'm thinking stick with the tried and tested method. The problem is space. The stock carbs barely fit inside the frame as it is so I have my doubts about getting a set of cb400 or gsx400 throttle bodies to fit. If I cant go with ITB then I could possibly go with a single TB and manifold. How do the two setups compare? Is there a reason this setup isn't used on bikes? Also with the single TB system, is it more normal to have a single injector located in the throttle body or is it possible to mount four injectors just before each intake? I have read a bit about ITB vs single TB on cars and the general consensus is that a single TB is easier to tune. But then how come all performance bikes run ITB?

I will aim to setup the megasquirt to handle fuel only to start with but I would like to allow for it to be able to control spark also in the future. So for now, it should be sufficient to use the coil pack terminal to read engine rpm from right? In the future, I have read that you need a trigger wheel to read crank position and rpm from. In my cbr, the ignition is controlled by a pulse rotor which is a wheel with 7 teeth and 1 tooth missing. Would it even be possible to use the output from one of the pulse generators to read crank position for the megasquirt? Space is very limited in these little engines so there isnt much scope for fitting extra sensors inside engine casings.

Does the ecu require a coolant temp sensor with a digital output or would the stock analogue sensor work? This is the sensor which provides the input for the temperature gauge. The sensor is located away from the engine in the thermostat casing but the coolant will pass it before the thermostat. Here is a picture of it:


What is the normal injection sequence for IL4 engines? Is it almost always simultaneous injection or would there be any advantage to injecting on 1&4 and 2&3 separately since these pairs reach TDC together?

I know its possible to map and tune without using a WBO2 sensor but is it possible to set one up in Megatune just for datalogging? As in to not have a closed loop injection map but be able to log AFR when tuning the maps? Does a WBO2 sensor need to have the controller to hook it up to the megasquirt ecu or does the sensor plug straight into the ecu? ie, do I need to have something like the LC-1 controller for what I want to do?

Finally... Megatune or TunerStudio? They both look pretty similar from the offset but is there an advantage to using one over the other? I'm leaning towards Megatune since the MS manual references it so I reckon it will be easier to learn.


Cheers guys! I appreciate any help I can get on this one and hopefully I will be able to help others with this one day.

[Bernard Fife]

mm,

19000 rpm is no problem, and you can edit the gauge in the INI to show any limit you like (below 65535 rpm).

TunerStudioMS is what you want to use for tuning, MegaTune hasn't been updated for years. We are working on removing references to MegaTune from the manuals (it's a slow process).

For sensor info and lots of other things, see: http://www.megamanual.com/mtabcon.htm

Lance.

[motthomas]

Thanks Lance! I'd better get more familiar with TunerStudioMS so.

It looks like I will need to do some tests on my stock sensor to see if it can be used. I see in the manual that sensors without a separate earth connection (grounded to the frame) are not reccomended... I wonder if I were to solder a separate earth wire to the body of the sensor would it work as a more stable earth... testing will need to be carried out! I would prefer to use my current sensor as it is much smaller than the GM sensors. I would need to machine an adapter to fit into the hose between engine and thermostat housing if I were to use the GM unit.

[Bernard Fife]

motthomas,

If you grounds are good, the 1-wire senor should work okay. I ran one like this on my car for quite a while with no problems. If you find out later that you get an unacceptable level of noise in the CLT signal, you can add a separate ground then (but run the risk of creating a ground loop). Coolant temperature is only used to control the warm-up enrichments.

The intake air temperature (IAT) sensor (aka. MAT) is a different matter, as this affects the fuelling at all times and must be a fairly clean signal.

Lance.

[motthomas]

Ok. That sounds good. It makes things that bit easier from a hardware perspective. Were you sharing the sensor between the MS unit and the temp gauge? I'm wondering if the sensor would like being shared...

he IAT sensor isn't a problem. I will just buy one of the GM sensors for that and since I will be changing the whole intake system, I'm sure I'll find a place to mount it!

Thanks Lance! Further research is definite required!

[Bernard Fife]

motthomas,

Sharing a sensor with a gauge is just like sharing it with another ECU. For sharing the sensor, see this: http://www.megamanual.com/v22manual/sharesen.htm

Lance.

[EWflyer]

All I can say is wow, a CBR250RR. Honda didn't build many of them and there certainly aren't many left on the road any more. Your bike is a rare and amazing piece of Honda engineering.

I'm a fellow "small bike" guy, I've got a Kawasaki EX-250 running "fuel only" with a Microsquirt. I'm jealous of your CBR250RR. Hope your project works out well.

[motthomas]

Thanks EWflyer! Its an amazing bike alright and I love it to bits! So much so that Ill be buying a second one come Christmas time! They arent as rare here in Ireland as you might think though. There were quite a few imported in the 90s from Japan but they are starting to get rare again as they tend to be ridden as learner bikes and people dont take as much care of them. Hence the lookout for the second bike! Got to love the small bikes!

I hope it works out too. Ive plenty of time to research it so hopefully that will help things.
Cheers for the link Lance. Ill have to give that a look when I get the microsquirt unit.