VE "dip"

[Calan]

Has anyone else noticed a dip in the VE at around 3500 rpm (specifically on a stroker, but on any setup in general)?

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No matter what I've tried to do with smoothing and manipulating values on either side, the VE at 3500 rpm has always been lower than I would expect, and the VE at 2500 rpm much higher...even on different turbos, intake, etc. I also see a similar dip at 2000 rpms and very low loads, but not as much.

It doesn't matter if I run the CombinedFT wizard in link, or do the math by hand and adjust them all manually at various points. IAT's, type of fuel, and coolant temps also have no effect on it. I always get the same results.

Any idea why? What would cause an rpm-dependent restriction at low loads like that?

 

[bastarddsm]

Hmm thats odd, I haven't noticed a dip like that, but I run ds-map, and I never spent much time in that area of the map. Maybe others with different ems will chime in. It probably has somthing to do with the turbo starting to work there, possibly some sort of resonance thing with the intake.

 

[Calan]

It's also low before I start building boost though. That table is indexed in atmospheric pressure; notice the dip below 14.7 apsi where boost begins.

It's weird (but normal for my car. I'd be worried if the VE table looked like a typical DSM...or any motor for that matter. )

 

[architechnik]

It's funny that the topic has come up as a Dip at 3.5k, instead of a spike at 3k. I've always considered it an unusual increase right there. I'm guessing there is just some special efficiency difference between those two points.

I noticed it much more on my old engine than my current build, but at the same time I replaced the alternator. I get the feeling that it's more of an electrical balance than the actual engine. Perhaps the coil dwell or injector response matching up with the alternator/regulator kick-down. Does anyone know what the stock points are for the alternator?

 

[Lofty]

Possible you're bottle necking somewhere?

I don't know a damn thing about tuning, I'll start there, but maybe you need more porting

 

[Calan]

...maybe you need more porting

Hmmmm....

 

[Sam@RRE]

what injector size are you using? global settings and dead times. that dip area is being effected by fuel trims and the VE wizard in link is based off fuel trims. If you got and incorrect global/deadtime/voltage vs latency tables it will mess with it. Best way to build a proper VE table is set entire fuel map off boost to 14.7 and under boost to 10.5 and disable any o2 feedback (lock in open loop) and adjust VE until reported AFR on the wideband matches closely to target AFR.

 

[Ravenous]

Calan my friend, you are not alone...

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Same spot and everything but I am on a 2.0 with 8.5:1 pistons. If I do the calculations by hand or have my tuning spreadsheet do it, I still end up with the same results.

 

[Sam@RRE]

Here's a screenshot of my VE table

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[Ravenous]

Is that ran through a smoothing algorithm? It looks way to purty to be made by just flattening out the fuel table and adjusting the VE till the AFR matches the fuel table.

 

[1990AWD]

Here's a screenshot of my VE table

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How the heck did is yours so smooth? Mine is all over the place.

 

[snowborder714]

Here's a screenshot of my VE table

I'd be interested to see a 3rd gear pull log of this car.

 

[Calan]

what injector size are you using? global settings and dead times....If you got and incorrect global/deadtime/voltage vs latency tables it will mess with it.

They are accurate for my injectors (see my profile for details). Verified against flow and latency data from FIC.

that dip area is being effected by fuel trims and the VE wizard in link is based off fuel trims.

I know.

Best way to build a proper VE table is set entire fuel map off boost to 14.7 and under boost to 10.5 and disable any o2 feedback (lock in open loop) and adjust VE until reported AFR on the wideband matches closely to target AFR.

Yep. That's how I do it. I use the CombinedFT as a verification tool or to get into the ballpark quickly. For the most part, I run an AFR table with two values in open loop as you described, and I manually look for points in the log that match up with the table break points that have multiple occurances of good repeatable data. Then I adjust from that and interpolate between them as needed.

Regardless of how I get there, I always end up very close to something like that table I posted.

Here's a screenshot of my VE table

That looks like a theoretical best case; not something out of a running car.

BTW - is that a 2.0l or 2.3l?

Calan my friend, you are not alone...

You mean there is another car as possessed as mine?

I'd be interested to see a 3rd gear pull log of this car.

Me too. And normal idle/cruise for that matter.

And a plot of which points were actually being hit on a load dyno would be cool as well. Come on Sam... pony up.

 

[Sam@RRE]

Heres an old one on a E316G 91 octane only. The above posted in a base VE map I throw in every car I tune and it usually doesn't require much tweaking.
Heres a 3rd gear log from waay back when I was still on Link. Been on AEM S2 for some time now. Even my fuel and timing maps on AEM looks "too perfect" but I assure you it drives beautifully.

Ill see if I can get a recent log with the 50trim meth off my tuning laptop. Half the times I dont save my logs.

 

[Calan]

2.0l or 2.3l?

Why are you adding fuel with the sliders?

 

[Sam@RRE]

Another one on the 16G with boost turned up to 29psi on Meth and 91. Boostest and MAP sensor values only differ roughly 3%~4% at these boost levels.

 

[turbosax2]

Heres an old one on a E316G 91 octane only. The above posted in a base VE map I throw in every car I tune and it usually doesn't require much tweaking.
Heres a 3rd gear log from waay back when I was still on Link. Been on AEM S2 for some time now. Even my fuel and timing maps on AEM looks "too perfect" but I assure you it drives beautifully.

Ill see if I can get a recent log with the 50trim meth off my tuning laptop. Half the times I dont save my logs.

So you tune with the VE table and MAF compensation? That's from an older firmware release that didn't disable MAF compensation with SD operation.

 

[Sam@RRE]

Log of cruising home I think maybe...only time I log the car that long.

 

[Calan]

What size injectors and base pressure were those on?

(Thanks for sharing BTW )

 

[Sam@RRE]

So you tune with the VE table and MAF compensation? That's from an older firmware release that didn't disable MAF compensation with SD operation.

check the 2nd log. That was taken care of, and VE table didnt change if at all not by much.

 

[Sam@RRE]

Screenshots of my AEM timing and fueling.

On AEM once you get your fueling right, it should look like your torque curve.
FYI, everything is flat across load cells under boost due to the map being a boost comped map which applies a multiplier to the base fueling vale defined the the map. It works as a crazy trim to add fuel/pull fuel depending on boost level. Theoretically you need twice the fuel at 14.7psi at the same RPM vs 0psi and at 29.4psi you need 3 times the fuel of 0psi. So that value in the fuel map gets multiplied and modified by 10~20 other trims.

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Plot of my hp and torque curves. Solid lines is power/tq on AEM vs Link on the dotted line.

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Good stuff...worth the $1500? Not really, honestly Link is what 98% of the community can use. And if you have trouble learning Link....good luck with the EMS. Tuners charge a premium to tune EMS and even then they can only spend so much time on it. Most likely you'll have a car with startup and basic daily driving issues. DsmLink...none of that, true plug and play, throw in your basic global settings and it starts right up and works solidly.
You'll be lucky to get the car on EMS to drive out of your garage after messing with it for 3 hours. But they both have their place, I'm on EMS just to learn it to the best of my ability and i love the hours of internal logging at a REALLY FAST DATA RATE. Currently trying to figure out the speed sensor calibration and do gear calculation to do gear based ignition trim and gotta add a few % of fuel to cylinder 4 on the individual cylinder fuel trim due to the unequal distribution of meth in meth injection setups.

 

[Calan]

What size injectors and base pressure were those on?

2.0l or 2.3l?

(For the the ECMlink logs)

 

[mindset]

I hate acronyms.

 

[Calan]

I hate acronyms.

Huh?

 

[Sam@RRE]

(For the the ECMlink logs)

You guys will hate me for this, NO FUEL PRESSURE REGULATOR, just 255lph and whatever pressure it goes to.

Evo 560cc injectors.

Calan -In regards to slider adjustments, cmon..its ~3% could be fuel pressure related. Check the boostest plot vs actual boost read by the 3.5bar map. Got lazy and didn't want to turn shut the motor off, flash it, and start it back up. I would of made the change in fueling in the DA tables not the VE tables. That 3% in the sliders are only applied at WOT open loops, thus DA=open loop fuel.