RV8 Camshaft sensor

DaveEFI · Post by **DaveEFI** » Sat Jan 07, 2012 4:35 pm

daxtojeiro wrote:
Sorry, didnt explain that well. It wont revert to wasted once its running. It ignores the cam input once its syncronised onto the crank / cam signals, but if it doesnt see a cam signal then it will run wasted spark and seq fuel, but the fuel may not be on the correct sequence, but this wont make any real world difference in the running,
Phil

Is there any real point in going sequential injection on an RV8? And or sequential ignition over wasted spark?

stevieturbo · Post by **stevieturbo** » Sat Jan 07, 2012 4:44 pm

DaveEFI wrote:
daxtojeiro wrote:
Sorry, didnt explain that well. It wont revert to wasted once its running. It ignores the cam input once its syncronised onto the crank / cam signals, but if it doesnt see a cam signal then it will run wasted spark and seq fuel, but the fuel may not be on the correct sequence, but this wont make any real world difference in the running,
Phil
Is there any real point in going sequential injection on an RV8? And or sequential ignition over wasted spark?

There are certainly no downsides aside from initial setup work.

I couldnt be arsed with that myself, so I'm still batch fire and wasted.

daxtojeiro · Post by **daxtojeiro** » Sat Jan 07, 2012 8:43 pm

DaveEFI wrote:
daxtojeiro wrote:
Sorry, didnt explain that well. It wont revert to wasted once its running. It ignores the cam input once its syncronised onto the crank / cam signals, but if it doesnt see a cam signal then it will run wasted spark and seq fuel, but the fuel may not be on the correct sequence, but this wont make any real world difference in the running,
Phil
Is there any real point in going sequential injection on an RV8? And or sequential ignition over wasted spark?

There are no power gains and no real gains from the ignition, except that the coils dont work so hard. On a 4cy then sequential fuel has advantages when reving at high speeds, due to dwell time.

But the fuel side does have some advantages.
First off you can tune each cylinder to run at the same temperature using EGT sensors, as each injector can be mapped individually. This can give a little more power, not loads, but some.

Also it allows the ECU to correct the fueling quicker for sudden changes in engine speed. So the engine will react quicker to a sudden change in throttle position.

It also allows the engine to run more economically, as the fuel can be timed to injected into the inlet whilst the valve is shut, so the fuel gets more time to evaporate and therefore mixes better. We have played with this on the dyno, and we couldn't get it to make any more power at all! But the theory says it should be more economical,

Phil

adamnreeves · Post by **adamnreeves** » Sat Jan 07, 2012 9:49 pm

Thanks guys for the replies I understand a bit more now. Phil I didn't notice any difference on the cam wheel when I installed it but that was a few years ago and I wasn't looking for it.

stevieturbo · Post by **stevieturbo** » Sat Jan 07, 2012 9:58 pm

Unless you are going to bother messing with injection timing and fine tuning individual cylinders, I would say there is little point bothering going sequential.

Unless of course it is very easy for you to do it.

The only times I would say it becomes important and needed. Is if you are running large injectors and/or relatively big camshafts.

But I'm talking bigger than say 750cc per cylinder and a camshaft with a noticeable rough idle which affects airflow at low speeds. And with big injectors firing twice per cycle it's simply more fuel than the engine can handle. So despite having a 750cc injector as it fires twice it looks like a 1500cc.

Dropping to sequential and only firing the injector once per cycle cuts that in half.

adamnreeves · Post by **adamnreeves** » Sun Jan 08, 2012 9:52 am

stevieturbo wrote:Unless you are going to bother messing with injection timing and fine tuning individual cylinders, I would say there is little point bothering going sequential.

True but I have to remove my timing cover to replace the gasket has it has a little oil oil leak. However the main reason for doing this is just because it can be done. Having said this I have noted that you can trim individual injectors and would want to try this as some of my cylinders do run hotter but I appreciate this may not just be down to fuelling. In the end I want to run full sequential, Coil on plug, EGT probes. Twin Lambda sensors (I am only running one at the moment, Twin Knock sensors (have none at the moment). Later I want then to try implementing launch and traction control which I can then do as I will no longer be using EDIS. This will be a few years in the making, the fundamental reason being learning.

DEVONMAN · Post by **DEVONMAN** » Sun Jan 08, 2012 10:24 am

Quote "It also allows the engine to run more economically, as the fuel can be timed to injected into the inlet whilst the valve is shut, so the fuel gets more time to evaporate and therefore mixes better. We have played with this on the dyno, and we couldn't get it to make any more power at all! But the theory says it should be more economical"

Phil
_________________

Hi Phil.
Like Adam, I will in the future be playing with sequential injection mainly to keep the grey cells working.

I'm not clear on your comments above about injecting when the inlet valve is closed.
Is there not the likelyhood of fuel dropout to the port walls while the mixing is going on.
If you hadn't made the statement I would have assumed wrongly or rightly that the injection should occur just as the inlet valve opens so the the fuel does not slow in the port and mixing then occured due to swirl in the bore and squish.

Your comments on this would be very welcome.

Regards Denis

stevieturbo · Post by **stevieturbo** » Sun Jan 08, 2012 11:24 am

Nope, it seems to be a misconception about firing with the valve open.

Motec and others have suggested it is best to fire against a closed valve. I actually read another article online just a few days ago stating the same. Damned if I can remember where it was though !

Whether the entire injection event is against the closed valve or some open, I cant recall.

But either way it is all speculation in this case. The only way you will find out what your engine wants is with extensive testing on the dyno.

shaunod · Post by **shaunod** » Sun Jan 08, 2012 1:25 pm

stevieturbo wrote:Nope, it seems to be a misconception about firing with the valve open.

Motec and others have suggested it is best to fire against a closed valve. I actually read another article online just a few days ago stating the same. Damned if I can remember where it was though !

Whether the entire injection event is against the closed valve or some open, I cant recall.

But either way it is all speculation in this case. The only way you will find out what your engine wants is with extensive testing on the dyno.

Couldn't agree more Stevie. There are theoretical gains to both methods and also theoretical losses ... at the end of the day .. if you had a BMW research budget you could probably get a very accurate answer to which is better .. but in the real world with our limited budget, diagnostic equipment and time .. it is more a case of 'suck it and see' and go with what works best for you.
There is definitely some mileage in fully sequential for low engine speeds and high lift / duration cams that make idle and low rpm driving difficult, but by the time you are 6000 rpm and the injectors are acting more like hose pipes than anything else, the gains / losses are going to be far less obvious. IMHO!

daxtojeiro · Post by **daxtojeiro** » Sun Jan 08, 2012 8:24 pm

DEVONMAN wrote:Quote "It also allows the engine to run more economically, as the fuel can be timed to injected into the inlet whilst the valve is shut, so the fuel gets more time to evaporate and therefore mixes better. We have played with this on the dyno, and we couldn't get it to make any more power at all! But the theory says it should be more economical"

Phil
_________________

Hi Phil.
Like Adam, I will in the future be playing with sequential injection mainly to keep the grey cells working.

I'm not clear on your comments above about injecting when the inlet valve is closed.
Is there not the likelyhood of fuel dropout to the port walls while the mixing is going on.
If you hadn't made the statement I would have assumed wrongly or rightly that the injection should occur just as the inlet valve opens so the the fuel does not slow in the port and mixing then occured due to swirl in the bore and squish.

Your comments on this would be very welcome.

Regards Denis

As Steve says, its a myth that injecting to an open valve is the way to go. From experiments that have been carried out on the MS forums, the best method is to finish injecting the fuel just before the valve opens.

But me and ShaunOD have played around with firing angles on my engine on the V8D dyno and we couldnt get any increase in torque by adjusting the angle over the whole 720 degrees.
Having said that, its probably an efficiency affect rather than power.

To tune it I have found the best option is to adjust the timing for the richest mixture as read by the lambda. That should be the most efficient angle for your engine. Then simply fire the injectors 20 degrees earlier for every 500RPM,

http://www.extraefi.co.uk/Seq_MS3.html

Phil

dnb · Post by **dnb** » Sun Jan 08, 2012 10:05 pm

You should always be injecting against closed valves IMO.

The fuel hits the hot valve and vaporizes. This causes the valve to be cooled. Both factors are important - the valve cooling is certainly a good thing due to the very thin contact area between a closed inlet valve and the head, which is the only other way of cooling the valve...

As Phil suggests, the best strategy is to inject such that you just finish by the time the valve is opening. I have tested things and come to much the same conclusion.

As an aside, if you configure sequential injection but have no cam sync then you can still fire one injector at a time - there are two opportunities to inject against a fully closed valve in a cycle, and they are 360 crank degrees apart. It therefore doesn't really matter how the injector cycle syncs up to the engine. Therefore there is no pressing need to double up the injectors if you don't want to unless the ECU insists that you do.

DEVONMAN · Post by **DEVONMAN** » Sun Jan 08, 2012 11:13 pm

Thank you guys for the feedback.
All sounds logical.
It's good to learn something new every day.

Looking forward to playing with sequential in the near future.

Regards Denis