Dual Fuel Maps and VVT

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jalava
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Dual Fuel Maps and VVT

Post by jalava »

We are planning on using FSIO for controlling on/off type modified VVT on Renault F4R engine.
This sets us for another problem however, because we are turning VVT in 4000rpm range instead of just bit over 1500rpm like it is now on stock solution, engine characteristics change so much that setting up VE table is very hard and tuning the switch over point requires constant modification of fuel tables. Also because VE changes on crossover so radically, you would need few tightly setup columns for preventing invalid interpolation in map.

I would like to have two fuel maps (and possibly two spark maps) that I could tune separately and then swap between maps based on FSIO state while I energize the solenoid that turns the camshaft. This way we could run the engine with VVT and without and then just set the crossover point bit below torque curve crossover rpm (it is probably not instant).

Another thing this brings to my mind, is possibly some enrichment required if we suddenly change to overlap on WOT, this might cause jump in MAP?
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AndreyB
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Re: Dual Fuel Maps and VVT

Post by AndreyB »

Shorer story - would it help to change X axis points?

You have a major change at 4000 and interpolation between default axis buckets, for example 3600rpm value and 5000rpm value, does not seem smooth enough?

Can you change axis values and have a special transition bucket from 4000 to 4010? that case instead of interpolation in a wide range with sudden change, you would have interpolation in the cells before the "4000/4010" step, and interpolation between cells above 4010?
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Maxi
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Re: Dual Fuel Maps and VVT

Post by Maxi »

russian wrote:Shorer story - would it help to change X axis points?

You have a major change at 4000 and interpolation between default axis buckets, for example 3600rpm value and 5000rpm value, does not seem smooth enough?

Can you change axis values and have a special transition bucket from 4000 to 4010? that case instead of interpolation in a wide range with sudden change, you would have interpolation in the cells before the "4000/4010" step, and interpolation between cells above 4010?
I think you did not understand what he was talking about. Interpolation is needed between two different VE maps - not points of one...
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AndreyB
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Re: Dual Fuel Maps and VVT

Post by AndreyB »

Why would we interpolate between two maps for an on/off VVT device? How would we be weighting between two maps for an on/off VVT device? I can see this for a multi-position VVT but not getting it for the on/off device.
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Maxi
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Re: Dual Fuel Maps and VVT

Post by Maxi »

Cam traweling time model from on to off and back giwes weight for interpolation. just so in Sirius34-F4R stock do.
stefanst
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Re: Dual Fuel Maps and VVT

Post by stefanst »

I'm going to question the whole premise of this idea.
The underlying assumption is that we're switching VVT to maximize torque and VE, not to optimize fuel consumption in some area of operating conditions and torque in others.

The usual way of tuning VVT is to record a torque curve with it on and another with it off. See image.
VVT switch point.png
VVT switch point.png (12.06 KiB) Viewed 3957 times
The switchpoint should be where to two curves cross. At that point the VEs of both states are identical, so there should be no sudden changes in VE.
jalava
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Re: Dual Fuel Maps and VVT

Post by jalava »

I don't really need interpolation between two maps, but two actual fuel maps, one with VVT on, one with VVT off, so that when I set VVT on via FSIO, I can also swap to secondary fuel map at the same moment.

When done this way, you can configure both maps separately and then afterwards change the VVT activation point and maps themselves should retain pretty good stability. We are planning on turning the cam only about 5 degrees.
jalava
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Re: Dual Fuel Maps and VVT

Post by jalava »

stefanst wrote:I'm going to question the whole premise of this idea.
The underlying assumption is that we're switching VVT to maximize torque and VE, not to optimize fuel consumption in some area of operating conditions and torque in others.

The usual way of tuning VVT is to record a torque curve with it on and another with it off. See image.
VVT switch point.png
The switchpoint should be where to two curves cross. At that point the VEs of both states are identical, so there should be no sudden changes in VE.
At least from my experience working with Honda VTEC, I always got huge jumps in torque activating VTEC and hence I'm expecting similar to happen when VVT is activated (or rather deactivated as it loses oil pressure and turns the intake to later angle increasing overlap in this case). Though with VTEC also lift and cam duration changes, so maybe it is more stable with regular VVT.
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Re: Dual Fuel Maps and VVT

Post by stefanst »

jalava wrote:At least from my experience working with Honda VTEC, I always got huge jumps in torque activating VTEC and hence I'm expecting similar to happen when VVT is activated (or rather deactivated as it loses oil pressure and turns the intake to later angle increasing overlap in this case). Though with VTEC also lift and cam duration changes, so maybe it is more stable with regular VVT.
That's interesting and a bit unexpected. Do you by any chance have dyno curves of this behavior? Also VE tables?
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AndreyB
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Re: Dual Fuel Maps and VVT

Post by AndreyB »

jalava wrote:I would like to have two fuel maps...
I think there should be RAM in the stm32f407 chip to add a couple of more maps.

Unfortunatelly there is no chance that I would be able to work on this code any day soon :( You would need to fork rusEfi and make these improvements in your own version.
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jalava
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Re: Dual Fuel Maps and VVT

Post by jalava »

stefanst wrote:
jalava wrote:At least from my experience working with Honda VTEC, I always got huge jumps in torque activating VTEC and hence I'm expecting similar to happen when VVT is activated (or rather deactivated as it loses oil pressure and turns the intake to later angle increasing overlap in this case). Though with VTEC also lift and cam duration changes, so maybe it is more stable with regular VVT.
That's interesting and a bit unexpected. Do you by any chance have dyno curves of this behavior? Also VE tables?
Already sold my Hondata S300, but I think I still have the dyno printout somewhere. It was quite curious, moving the vtec activation point around even after maps were done always caused this dip and spike in torque where ever the switch point was. My dyno guy says that always happens as engine takes a gulp of air at that point.
atntpt
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Re: Dual Fuel Maps and VVT

Post by atntpt »

is dual map feature in the plans ?
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