To be fair it depends on you as a person and how you work.
My honest answer based upon my usage is 4 channels is the way to go.
If you think of a customer who brings a car in for lack of power, lets say a Common Rail Diesel engine, No Fault Codes present, where do you go?
Well you could connect the scope as follows:-
Channel A: Digital MAF
Channel B: Fuel Rail Pressure
Channel C: Boost Pressure Sensor
Channel D IMV Valve.
In one simple WOT test you get a picture of the Intake/Fuel system which potentially allows you to see all the parameters which could cause loss of power in one hit. Now we know these may not be the issue all the time, but its a quick way of seeing whats going on.
With 2 Channels you would probably want to run a combination of multiple tests which takes longer in the long run potentially making the job last longer then it needs to.
In reference to our customers, most customers who purchase a 2-Channel Scope always come back for the 4-Channel model and by doing this costs a lot more long term, so if you can budget the 4423 or one of the 4 Channel kits then this really is the way to go.
I own a repair shop and find that the infromation you provided usefull but I do not get to many diesels in my shop. Is there any other things I can get out of a four channel If I was working on a 4, 6, or 8 cylinder EFI gas engine?
Hi Jarrod if you can afford go for the four channel, i bought 2channel less than 2years ago and have now ordered a 4channel upgrade as Lee said costs a lot more in the long run.
Damian
OK, let's say you wanted to check the sync on a Ford EDIS cam sensor. Maybe there was recent work done and now there is a hesitation with no codes. You know that this can be a result of the cam sensor being installed 180 degrees out of phase. You also know that the PCM will not know there is a problem and the cam and crank relationship will be identical to one installed correctly.
So...with a third channel you can simply observe the secondary with the cam and crank to immediately know where the engine is in the cycle. Done. Sure you can get it done with two channels but more steps are needed.
Almost without exception, our customers that get a two channel later wish they had the four channel when they discover the possibilities.