SLOW SEDAN

iTrader: (13)

True, but even the ZR1 is fairly low powered in the big scheme of things, double it's power and how many keep the MAF. Personally I want nothing to do with a car that costs almost $5k to tune.

G Atsma

I have to agree. Once you're at that high a power level, the added refinement MAF brings becomes irrelevant.

ddnspider

iTrader: (26)

The MAF isn't why that thing costs 5k to tune....but I agree I can't fathom what these people charge for tuning the new stuff. And forget the euro/jap cars that you don't even own the tune, everything is always locked. Forget that.
​​​​​​​
Said from experience? There is always a limit. But for south of 1000whp a maf can be turned quicker and drive better. If someone is so concerned about the maf as "a restriction" it's because they're NA and don't make enough power. Even FNB's 468 still has a maf on it.

G Atsma

I was actually referring to some of the more experienced operators around here. it seems the more power made, the less apt to having MAF.
I'm sure it can be done, but it seems many making more power don't feel the need for the added complication it brings.

ddnspider

iTrader: (26)

Thats certainly 1 interpretation.

SLOW SEDAN

iTrader: (13)

For sure, its mostly paying for access to the ECM, but still a bunch of credits beyond that are needed. Its about to the point standalone is cheaper then HPT credits on new cars.

I still don’t know exactly whats better about drivability, I’ve never noticed much of a difference between map and maf referenced tunes assuming they are done properly. Plus you dont have to worry about intake pipe sizes, sensor placement, proper airflow over the sensor, scaling tunes for airflow limits, etc..

ddnspider

iTrader: (26)

Was just thinking the standalone stuff lol. I guess the market is set based on what people will pay. There's people who complain about the price of efi live and hpt credits for their 4th gen so it's all relative.

TrendSetter

So does mine!

TrendSetter

The scaling turns the tune into a puzzle. I spent an afternoon just trying to figure out what the deal was with my stoic af being in the 20s when I first got my z06. If I didn’t know it had been dyno tuned at a shop I would have assumed it was just destroyed and needed to start fresh.
first thing I did with my evo was go sd. It’s nice not being disabled any time a pipe blows off.

This thread does have me curious about the hybrid stuff but my car idles at 85kpa so it would be interesting to see if low speed drivability is any better than a maf.

ddnspider

iTrader: (26)

I was waiting for you

turbolx

I have an LS3/7 MAF element in a 3.5" tube on my TT C6. I only hit about 10,600Hz at an actual airflow around 70#/min (~700 flywheel HP gross), so you'll have plenty of headroom. Just remember that the IAT has a completely different transfer function.

ddnspider

iTrader: (26)

How much boost? That is surprising.

turbolx

Please bring me the data showing how much pressure drop you see across the new slot style (LS3/7/9) MAF element in a large (3.5"+ diameter) tube. I bet it's a lot less than you think and the air filter itself is a bigger restriction.

MAF's are wonderful steady state devices that are already compensated for temperature and pressure. If the system is already structured to use one, I can't imagine wanting to throw that away. The biggest challenge with them is transient tuning (manifold filling, strong pulsations), where GM already gave you a good fallback option on the SD calculation. I can't tell you how many times we wished for a MAF during development when I was calibrating Ford Ecoboost systems (that are SD only) because we couldn't really be sure what the actual airflow was.

TrendSetter

check out the latest power and speed podcast, he talks about it. very interesting stuff about falling off the right side of the map.
the way he was talking, i guess hes running single port wastegates?

turbolx

Boost pressure is irrelevant when talking about Mass Air Flow.

But, for reference, I was talking about ~7psi on top of a stock LS3 engine (APS twin turbo kit) making around 600RWHP on e10 91 octane.

turbolx

"HE" is me.

Yes, I have single port internal wastegates on the GT3076r turbos in that kit. With the snow and cold, I haven't been especially motivated to install the new Sirhc Labs boost controller and go back to the dyno for testing to prove we can hold the desired pressure. This is a whole other story than MAF vs SD though.

TrendSetter

Sorry Greg, I'm well aware, that post was directed to ddnspider, i wasn't sure how long you would stay in the conversation, you're a busy guy.
A little off topic on the wastegates, i just havent used single port gates before, only dual ports and the problem you described sounded like that was a factor in your control problems and needing the Sirhc Labs controller.

Do you have a map cutoff for where you feel like SD is helpful at low speed? my car idles at 83-88 kpa and is currently maf only. obviously i can just go find out on my own, but I'm curious if you have insight you would like to share. the car drives 'ok' but it does get a little jumpy at low rpm, and i stall it now and then.

ddnspider

iTrader: (26)

Yes I agree, 10 psi from a T67 and 10 PSI from a T88 are not the same....I should have asked in terms of power not PSI. Still surprised the MAF freq is that low at 600whp.

turbolx

I would consider single port gates the "normal" for most turbo applications, as I've used them more than anything else. The second port is obviously an advantage when it comes to boost control flexibility unless you're dealing with a modern continuously variable electronic wastegate actuator. Most turbo kits start with relatively simple configurations, which often means single port gates like my APS kit. The real problem for me came when I tried to turn it up by doing something more than just tightening the wastegate arm preload. The manual boost controller has a check valve that continued holding pressure on the diaphragm after the initial break-free point was reached when a direct connection to the boost reference (without a manual controller in the way) would have allowed the gate to close a little again as airflow demands from the intake rose sharply with RPM so that boost could remain constant.

An astute observer might just ask "why not remove the check valve then?" This is a valid solution on the boost control side, but it unfortunately also creates a vacuum leak if the manual controller is venting to atmosphere. So my solution becomes a PWM controlled MAC valve where the default position is still sealed but a controlled leak exists ONLY when actively controlling boost above the static gate pressure.

There's not really a MAP threshold. It's more a question of when the signal to noise ratio gets bad for the MAF. At idle, there will be pulsations that register as +/- disturbances on measured MAF. Excessive filtering on this to get back to the correct "average" MAF signal then runs the risk of having sluggish response to real transients (like when the driver tips in to leave idle or if idle speed dips on a trans/AC engagement).

Idling at 83-88kPa would make me nervous. It's a good thing you don't live in Denver, where that would be WOT! Are you sure you adjusted timing correctly for a reasonable torque reserve from MBT? If you cam is big enough to have such a high idle MAP, it probably also has a lot of natural EGR there from overlap. Hence, it probable needs/wants significantly more idle advance than stock just to hit the same torque reserve relative to MBT at idle.

Regardless, all spark (including idle) starts from speed and load in g/cyl. If you don't give the ECM a valid number for g/cyl, your first spark advance guess is likely wrong. This is where getting an accurate blended g/cyl number comes in handy. It's circular logic, as airflow affects spark, yet improper spark makes it hard to have stable airflow. All of that also ASSumes that you are able to keep fueling stable at lambda=1.0, which also requires an accurate g/cyl number that is best estimated from the blended logic. Changes in AFR result in changes in torque, which will have you chasing your tail on idle control airflow and spark.

aaronc7

That's good to hear, ambient pressure here is 87 kPa, my fear is I will run out when I go back to sea level; just trying to future-proof the setup. I have a reducing coupler on the way for test fit, if I can make this work, I'll move ahead with the switch. I would hate to spend the time and money welding up my 3.5" pipe for MAF, only for it to not work, something to think over.

Yep, I made a CAX file to reveal the IAT table for my car and converted IAT data from a C6 LS3 stock tune.

Thanks for chiming in