8 squirts on a 4 cylinder engine with throttle body injectio

[jonfx4com]

I am injecting a siamesed port 4 cylinder engine using a wet manifold system. It runs very well if I use 8 squirts alternating. Since it's not port injected this would not seem to be a illogical setup as it does not matter how many cylinders there are since I don't have an injector in each port anyway. 8 squirts gives me nice fuel distribution and largely negates the problems of unequal AFR in the inner and outer cylinder pairs without going sequential. Problem is that all the code variants I have tested will not allow me to configure it that way unless I tell Tuner Studio I have 8 Cylinders and accept the RPM showing as half the real value. Is there some way to configure TS so it does not apply this seemingly unnecessary restriction when not using port injection?

[Matt Cramer]

You won't have 8 real squirts that way - it actually behaves the same way as if you'd set the correct number of cylinders and 4 squirts, since it can't interpolate between ignition pulses. If using 4 cylinders, 4 squirts doesn't work, it may be that your VE table is off.

[jonfx4com]

Matt, are you quite sure of that? When I change it to 8 cylinders and 8 squirts the change is nothing short of a miracle. No amount of tweaking of the VE table can get it to run that well, especially at idle.

[Matt Cramer]

Yes, both settings would give you one injection per ignition pulse. The AMOUNT of fuel it's putting in, though, is radically different. Same goes for ignition timing if you are controlling that.

[jonfx4com]

Thanks Matt. Looks like I had better do some more investigation then.

[DonTZ125]

I'm missing something here - if the number of cyls is set to 8, why would it NOT give 8 squirts? Assuming a real trigger wheel with sufficient teeth is in use, it should give a shot every 90 crank degrees.

[Bernard Fife]

Don,

It will give 8 squirts nominally, but it thinks it gets 8 tach events for 2 revolutions. Because it's only a 4 cylinder, those 8 tach events actually take 4 revolutions (which is why the tach gets messed up). So you still only get 4 injection events per 4-stoke cycle (= 2 revs).

Lance.

[DonTZ125]

That's why I mentioned a real trigger wheel - yes, a 4cyl using coil -ve will only give 4 events, but a MS with a trigger wheel generates its own tach events - a V-8 can use a 24-1 tooth trigger wheel (or an 8-1, for that matter) and get 8 tach events per 720deg of crank rotation.

I haven't seen an msq or previous discussions; if this fellow is using coil -ve, then I'll sit down and shut up.

[Bernard Fife]

Gotcha - agreed.

[jonfx4com]

so I was getting 8 squirts after all. Back to my original question, why can I not select 8 squirts with 4 cylinders and non port injection.

[jonfx4com]

yes, I am using a 36-1 trigger wheel BTW.

[Matt Cramer]

yes, I am using a 36-1 trigger wheel BTW.

If you are using the wheel decoder, you should be able to set up the decoder in such a way as to get correct RPM with it set for a phony 8 cylinder. I had thought you were using a basic distributor.

[jonfx4com]

Matt, can you point me in the right direction as to how to do that. Currently running 2.905 code, not had much look with the autotrigger code.