Tuning Newb - VE values nearing 200%

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Tuning Newb - VE values nearing 200%

Postby goodysgotacuda » Wed Oct 11, 2017 5:20 pm

I have been focusing on getting my Hemi reliable on the road and it has been running very well. The table still needs a bit of work, but my AFRs are inline for where they should be as I run the engine around the map.

Seeing numbers get up around 200% seems wrong, like I have a fuel calculation wrong. Can someone confirm my thought process? I have a pretty basic 5.7L Hemi with a cam, naturally aspirated with larger than stock injectors. I expect a proper VE table for something like this to not exceed ~115-130%, is that true?

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Re: Tuning Newb - VE values nearing 200%

Postby Matt Cramer » Thu Oct 12, 2017 6:16 am

Try adding in "Incorporate AFR Target" - this requires slightly lower VE numbers.

The highest the table can go is 255.
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Re: Tuning Newb - VE values nearing 200%

Postby ChevelleFan » Thu Oct 12, 2017 6:53 am

One problem I had years ago when I had some very large VE numbers was a failing fuel pump. I had a rail-mounted gauge and everything seemed fine when I would look at it idling, even quick revs. But under load, the pump couldn't deliver enough fuel, pressure dropped, and the VEs got larger trying to compensate. Finally, I had a friend in the driver's seat brake-torque like doing a burnout while I watched the pressure gauge, and that's when the pressure drop was revealed. Just something to consider/verify.

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Re: Tuning Newb - VE values nearing 200%

Postby goodysgotacuda » Thu Oct 12, 2017 8:15 am

ChevelleFan wrote:One problem I had years ago when I had some very large VE numbers was a failing fuel pump. I had a rail-mounted gauge and everything seemed fine when I would look at it idling, even quick revs. But under load, the pump couldn't deliver enough fuel, pressure dropped, and the VEs got larger trying to compensate. Finally, I had a friend in the driver's seat brake-torque like doing a burnout while I watched the pressure gauge, and that's when the pressure drop was revealed. Just something to consider/verify.

-Dave



That's something on my list to check. I plan on adding a fuel pressure input to the ECU so that I can log it as well. Thanks


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Re: Tuning Newb - VE values nearing 200%

Postby goodysgotacuda » Thu Oct 12, 2017 8:17 am

Matt Cramer wrote:Try adding in "Incorporate AFR Target" - this requires slightly lower VE numbers.

The highest the table can go is 255.


I have it off because I had issues with what it was doing.

I had a dead steady 13:1 AFR at idle and my idle cells in the Target AFR table were also 13:1.

When I turned on "incorporate AFR target", my idle AFR would increase by an entire point. I tested this several times and determined I was better off leaving the incorporate setting "off".


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Re: Tuning Newb - VE values nearing 200%

Postby goodysgotacuda » Thu Oct 12, 2017 8:18 am

If I change the injector flow rate in the fuel required calculation, is there a way to have my VE table scale according to that change?


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Re: Tuning Newb - VE values nearing 200%

Postby jsmcortina » Thu Oct 12, 2017 8:31 am

goodysgotacuda wrote:When I turned on "incorporate AFR target", my idle AFR would increase by an entire point. I tested this several times and determined I was better off leaving the incorporate setting "off".

Turning the setting on or off requires the VE table to be changed because it is multiplying in (or not) a scaling factor.
Normally it is best to enable it, then tune.

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Re: Tuning Newb - VE values nearing 200%

Postby billr » Thu Oct 12, 2017 9:31 am

"Change the flow-rate"??? Does that mean they have not been flowed for rate and DT with your fuel system and injector drivers? If the have been flowed, and you know the correct number, then leave it at that. Anything else will only add to the confusion. If you haven't flowed them, then having odd VE values is kind of to be expected...
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Re: Tuning Newb - VE values nearing 200%

Postby goodysgotacuda » Thu Oct 12, 2017 12:55 pm

billr wrote:"Change the flow-rate"??? Does that mean they have not been flowed for rate and DT with your fuel system and injector drivers? If the have been flowed, and you know the correct number, then leave it at that. Anything else will only add to the confusion. If you haven't flowed them, then having odd VE values is kind of to be expected...


I don't have a flow rate number, but let's say I sent them out to get that.

Once I get the number and input it into tunerstudio, will I need to retune my VE map? Or can it be scaled according to my changes?


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Re: Tuning Newb - VE values nearing 200%

Postby billr » Thu Oct 12, 2017 2:01 pm

If you send the injectors out, you really need to send your MS and fuel system with them. Testing yourself is far more practical, and costs little. For flow rate, all you need is some way to measure either the weight or volume of fluid delivered during a period when the injector is held open. There are many common throw-away food containers that can be measured to give an accurate measure of volume collected, I like 5-qt ice cream tubs...

Yes, once accurate flow rate is known, the req_fuel may have to be corrected, and then the VE table should settle out (using VEAL) with more realistic values.
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