WTF?! MAP Latency!!!

[ProTools4]

I have a new combo I am working on and am seeing .1 - .2 seconds latencty or delay in the map sensor readings?
Has anyone had issues / concerns / data about this?

E67 Erod computer and harness
MAP just behind the throttle.....

[5FDP]

How many things are you logging in the table??

Having alot of stuff in there, like anything over 24 will slow down the readings alot.

[ProTools4]

seeing a decent OFFSET between Throttle openings and changes in the MAP

[ProTools4]

This is a Major issue for any SD LS!!
in the last 24 hrs I have tested stock and modified cars!!!

Look at something in your bay and report back!
I dare you!

[ProTools4]

vamnumber2 whackasaurs AD.hpl

here is a log off a stock 2013 C6 DS GS

[DSteck]

What exactly is your basis for saying there is a delay? There is a manifold fill time dictated by fluid mechanics.

[ProTools4]

What exactly is your basis for saying there is a delay? There is a manifold fill time dictated by fluid mechanics.

DStech,

You are a super sharp guy and I have mad respect.
take a zoomed in look at the log I posted and tell me what you see.
that is a 100% mechanically factory stock C6 DSLS3 GS

[DSteck]

I understand that, but air is a fluid, and it cannot instantly pressurize a given volume. I would never expect it to instantly track actual throttle position.

[10_SS]

Whatever causes it, "DELAY" is the proper term and problem, but for whatever reason the cylinders see more air before the MAP see's it, and goes lean... so delay is a big problem.

I also had this problem, people with M6's will notice it more than the auto guys of course. GM realized it too and the ZL1 and other LS3's uses TPS to enable PE, not MAP since it's too slow to respond (delayed) (MAP enable real low, like 15kpa)

I just checked a handful of GM LS v8 files dating back to 2002ish... they all enter PE based on TPS, not MAP. In fact, some of the older ones basically go into PE based on RPM since MAP = 15kpa, TPS = 3%, above 5000rpm.

That's not a bad strategy... maybe I'll change to that.

[10_SS]

then theres the Whippled GM Copo seen at the Woodward cruise... two old school map sensors (giant ones from the 80's and 90's! Wonder why they didnt use the newer ones... Any why are there two? from what I can tell is one is on right side, and one on left side of the base of the Whipple.

2Map.jpg

[Montecarlodrag]

What is the problem with that delay? it's completely normal
As DSteck said, air is a fluid and you can't expect an instant and linear response in its behavior.
The air is flowing into a closed space where the cylinders are causing a vacuum, of course the cylinders will fill first, until then the pressure inside the manifold can raise. That is the purpose of a MAP sensor, because TPS can't accurately predict all possible situations much less when the engine has transitory states, like going from idle to a sudden WOT. TPS is not a good method to calculate airflow but MAP is.

Check if MAP reading is correct, then datalog only the PIDs you really need. Nothing to worry about

[10_SS]

What is the problem with that delay? it's completely normal
Nothing to worry about

Running lean under boost is nothing to worry about? LOL

Just enter PE early, based on TPS since the MAP delay cant be fixed.

Also setting PE MAP enable to 85 helps... but then your in PE early under normal driving.. So TPS/RPM is the way to go (as GM does it, with a 100,000 mile warranty).

[DSteck]

You would benefit heavily from understanding what transient fueling is and how evaporation and wall wetting come into play.

[BigDaddyCool]

Running lean under boost is nothing to worry about? LOL

Just enter PE early, based on TPS since the MAP delay cant be fixed.

Also setting PE MAP enable to 85 helps... but then your in PE early under normal driving.. So TPS/RPM is the way to go (as GM does it, with a 100,000 mile warranty).

Transient Impact Factor? Charge Temp Bias vs Filter Rates........ both can be tweaked to create a richer response to cover x issues........ Maybe 'over compensating' on VE just outside WOT where your about to enter full throttle to enrich the mixture....

Enter PE SUPER EARLY and have a slower enrichment rate? Set a higher enrichment/pe/afr value to ensure on full throttle gear kick backs it stays within certain AFR's......

Dont mess with GM's setup? ....... MAP is SLOW, its a fact it wont change. Question is how can you make it work for you......

If you want to try and make a MAP based pe setup......... set 5% Throttle by 70kpa....... across the board...... If you look across alot of tunes you will see that on the ls2 & ls3's 70kpa seems to be the average end spot for any type of fuel compensation........ past that its mostly the same.

My 2 cents.......... and oh yes tuning is frustrating

Transients ........ Feed me more.

[10_SS]

You would benefit heavily from understanding what transient fueling is and how evaporation and wall wetting come into play.

I've tweaked the crap out of those settings... In the end, they only fill the gap where PE delay due to MAP occurs. Fix the problem correctly by removing the PE delay.

[edge04]

If you want to try and make a MAP based pe setup......... set 5% Throttle by 70kpa....... across the board...... If you look across alot of tune you will see that on the ls2 & ls3's 70kpa seems to be the average end spot for any type of fuel compensation........ past that its mostly the same.

Not sure I understand this. I assume this is based on NA cars. I had mine set to 5% and 90kpa and would enter PE far too early on my boosted 2 bar SD tune.

[DSteck]

Lol. Ok. The rest of the world makes it work.

[MikeOD]

If you want to try and make a MAP based pe setup......... set 5% Throttle by 70kpa....... across the board...... If you look across alot of tunes you will see that on the ls2 & ls3's 70kpa seems to be the average end spot for any type of fuel compensation........ past that its mostly the same.

If I did this, I'd be in PE...almost 100% of the time.