maxxdamigz

iTrader: (1)

The maf tops out at a certain mass flow over the sensor. The sensor, though, occupies a portion of the intake pipe. At 3.375" ID, the max reading ~5V occurs at ~360-370g/sec. At a larger intake diameter, it would take total flow to achieve the same MAF reading. Conversely, at a smaller ID, the maf sensor tops out earlier.

MazdaManiac

iTrader: (3)

1) Injecting W/M after the turbo does the exact same thing as doing it before the turbo. The turbo doesn't care if it is on or off an efficiency island. It just pushes air. It not like it goes off the edge and then stops - it just makes hot air. And hot air is a MUCH better candidate for charge cooling than ambient air. (RG - Stop with the nonsense. Just because some hicks in a garage settled on stuff like that standing around and FC back in 1989 doesn't mean it has precedent.)

2) The MAF can be extended out quit a bit by just using the last 1/2 volt Mazda left out of the calibration.

paulmasoner

iTrader: (1)

yes you can, there are members of this forum who are doing it on other vehicles right now

Brettus

iTrader: (2)

4.69V is approx 365g/s so you have another 0.31V that Mazda left on the table , as MM pointed out .
This would take you to 390g/s . Not sure how MM goes over that - pipe diameter ?

Brettus

iTrader: (2)

So this is your answer then ?
You wind the (3071) turbo way off it's efficiency island then cool the charge ...
Simple as that ?

paulmasoner

iTrader: (1)

i know you know how hot-wire MAF sensors work, and scaling, so this is more for others who i know are reading and dont quite get it....

simply, yes. the MAF doesnt actually measure every grams of air that passes through the intake. it measures a tiny percentage, based on the scaling(relationship between the tiny amount ACTUALLY measured/voltage from MAF, and the true total flow) in the PCM the actual flow is easily computed.

Now, increase the pipe diameter by some random amount. the physics and flow capabilities of the sensor itself havent changed, so it is still limited to measuring only a tiny representation of the total flow. but with a bigger pipe, total flow can actually be MUCH more. so you have to re-scale the Maf sensor. you are not making it report false numbers(if your doing it right) you're actually correcting it for the extra flow supported by a larger tube


now back to your regularly scheduled WTF does MM have under his hood discussion.... for the 9 millionth time(certainly not the last)

Brettus

iTrader: (2)

/\ what he said - lol

maxxdamigz

iTrader: (1)

The maf sensor its self may have a non-linear response. So, between 4.7 and 5 volts, you might get readings for more than just another ~30g but I guess you have to decide how comfortable you are using that range of the sensor. If a smaller change in that region corresponds to a larger mass flow change, any errors in your tune become more pronounced at probably the worst time. I assume there's a voltage vs. mass flow graph somewhere on here at stock intake geometry?

Brettus

iTrader: (2)

Very true . You can't really know for sure without doing exhaustive tests . As far as tuning errors - it really only matters that your fuel and timing are suitable for the actual MAF you are running . It matters more that you get the right result than having your scale 100% correct .

maxxdamigz

iTrader: (1)

https://www.rx8club.com/showpost.php...9&postcount=93

That's roughly the response I was talking about - whether that data is valid or not, I didn't read on, but the response shape looks legit. As far as tuning, I just meant that using a MAF sensor near it's peak where mass flow change per voltage change is at it's maximum may be why Mazda didn't use the upper spectrum of the sensor. Down the line at 400+ whp, maybe it'll become common place to run a larger diameter intake where you leave some headroom in the maf.

MazdaManiac

iTrader: (3)

To the crux of my argument. Who else here is up to the task before they open their mouths again?

And...

If the commanded values = actual AFR at a given MAF rate, then the scaling of the MAF table is correct. Its that simple. (Provided your injectors are properly scaled as well.)

paulmasoner

iTrader: (1)

yay, i love hearing that my concept of how things work is right.

rotarygod

There are certainly disadvantages to preturbo injection but it does have merit. Here's an excerpt from a website of what I can only surmise must be from a bunch of hicks. Incidentally I can't find an 89 FC anywhere around. I'll have to keep looking for it.

One reason for someone to inject at this location is the water/methanol mixture chemically alters the turbo compressor map. The water/methanol injection will dynamically shift the compressor map of the turbo so that it has the compressor map exhibit the characteristics of a larger turbo.

http://www.alcohol-injection.com/art...tion-nozzle-2/

I do find it interesting that you purposely want to use something horribly inefficient so you can develop a system to make it efficient again. I've got to say that is definitely thinking outside the box. I've apparently always been so closed minded and narrow that I'd just start with something more efficient and simple and then just not worry about added complexity of getting something less efficient back to where I would have started in the first place. This new modern precedent sure is intriguing! Let's expand this idea a bit. Why should turbos have all the fun? I can see it now. Roots supercharging; the next great breakthrough in forced induction through lower efficiency hot air charge cooling!

Brettus

iTrader: (2)

And provided your Ve table is not skewed to give you the result you want . So then, how do you know your Ve table is correct ?


Interesting that you choose to criticise rather than answer the simple question posed a few posts back .

BDC

Wow, I'm glad I stood around a 1988 FC back in 1989. I guess that counts me out!

B

BDC

Wrong. Before you make technical claims (yeah, sure, that'll stop sometime soon), perhaps you should actually mess with the stuff you're talking about.

Oh, good grief.

B

olddragger

iTrader: (3)

I have always heard that w/m striking the turbo blades will destroy them? Thats not correct?
I do know on s.c. you can inject before the compressor and that will increase boost because of better sealing and lowering the intake compressor temps. Now the rotors on a twin screw are going much slower than a turbo's blades and are not as hot?
But what do I know?
OD

Salamanth

Preturbo W/M injection can cause damage if the droplets are large enough, which is why "those who know" recommend running a low volume injector with very fine spray on a high pressure system for greatest atomization.

The difference between throwing sand and rocks through a fan
(Being somewhat facetious here, but you get the gist )

arghx7

I would say IBTL, but nobody locks **** flinging technical threads on rx8club...

olddragger

iTrader: (3)

i would be really be hesitant to do a water meth pre turbo on the street. Thanks for the info and I understand what you are saying, but after running a w/m system for over a year i can confirm that "deposits" do occur through the intake system and the jets do malfunction. Jets can get clogged and this affects the atomization substantially. That would be on the edge type stuff. Me too chicken!
Wouldnt any boost affect given by a pre turbo injection system would have to be by the cooler temps--not better sealing?
OD

MazdaManiac

iTrader: (3)

So, how is that FI RX-8 of yours going?

Thought so.

Instead of all the constant, transparent posturing, why don't you get off your ***, buy an RX-8 and try this stuff?
You will surprise yourself.

I do this stuff. You talk about this stuff.

Sitting on your (questionable) RX-7 laurels and second-guessing people from the nose-bleed seats isn't convincing anybody.
Least of all, anyone that sees through your nonsense.

The Ve table is a modifier. Anything other than a "1.00" isn't "correct".
Its an adjustment.
If you hit your AFR targets with MAF, you are "true". The Ve table is for corrections


Which question was that? I don't really read these things too throughly. I depend on other people to give me a heads-up on the things I need to answer.

Brettus

iTrader: (2)

Thought it was you who explained this table once as "volumetric efficiency . Which I took to mean theoretical airflow at that rpm/load vs actual or something like that .

Given the variance I see on the Mazda stock Ve tables (22% from one end to the other) and your assertion that anything other than 1 isn't "correct" I guess Mazda are really **** at scaling their maf

NVM I think you already answered .

MazdaManiac

iTrader: (3)

I think you are missing my point.

"Ve" does mean "volumetric efficiency".
But this Ve table does not actually follow the real Ve of the motor.

It allows you to nail a MAF scaling to a balanced commanded/actual AFR if you can't do it otherwise.
Since the Ve table is fixed to RPM but the MAF isn't, you use it to tweak the values.
But, if you can hit it without that, then you can.
Its like the windage adjustment on a long-range scope.
Some marksmen can compensate for windage on their own.

Mazda is straddled with having a MAF curve that is "standardized" and must work on a million RX-8s.
We do not have that limitation.

blackenedwings

The only question I care about an answer to, and you have not answered is if the advertised capability of the "3071R" from the upgrade page is accurate.

The concern is that the compressor map for a regular 3071 does not match that flow without running extremely outside its efficiency range. So either its just outside its efficiency range and something special is being done to make it work, or its not a regular 3071. I just want a simple answer, I'm not involved in a dick waving contest, I don't want a cryptic answer to go "figure it out"... I'm just a customer asking a simple question about the product I purchased and would like to take to the next level. You don't even have to answer here, I'm available 24/7 on my cell, email, and Facebook all of which you have. I have only posted here because it is quite frankly the ONLY communication method you respond to.

Brettus

iTrader: (2)

OK . That being the case you would expect that pretty much every RX8 engine (or series of engines) comes out with different numbers in the Ve tables to correct for engine variances .
Is that what you have seen ?

I just compared two maps in different ECU series and the Ve tables were identical .... (N3YMEC vs N3YMED)