morkusyambo

The voltage drop is a throttle lift. As for the AFRs, the drop down to 11.17 is intentional. I still have a stock exhaust, except for the straight pipe. Intake VDI is closed. Stock ports. I don't know for sure yet why I am seeing these numbers. I think that the key isn't so much the top end tuning(i'm running the same 20degress at max load you are....for now), as much as the rest of the powerband. What I will do is share with you guys as soon as I figure it out.

-Yambo

morkusyambo

OD, what reasons did Ric give for keeping the side seal tolerances loose?? I know a few respected rotary guys make them tighter when doing rebuilds.

Rote8

Maybe the previous line explains it:
"He laps ALL his side plates--they are NOT TRUE from the factory.
The Renasis has lose side seals for a REASON--dont try and tighten them up."

If the side plates are not true, the side seals would need to be loose.
Lapping the side plates may allow for tighter side seals.

/Just a WAG....

olddragger

iTrader: (3)

Mork--aint doubting ya man--please understand stat---just like you wondering ---hmmmmm? What the heck? Same a/f's and timing---same pressures---basically the same set up? but pushing a bunch more air---what the heck?
Any dyno sheets?
Maf volt drop didnt make sense--thanks.
Really looking forward to more exploration dude!

Ric DID NOT SAY OUTRIGHT that Mazda's factory tolerance standards are not what they used to be but i think we understood.
Side seals stay like they are for temp fluctuations and because of the way the exhaust port works with them. I dont know all the details ---if Ric says dont mess with them--i dont need an explanation. He put more emphasize of lapping all the plates.
OD

morkusyambo

Hmm. Do side seal tolerances have anything to do with compression?

morkusyambo

The thing is, I am running significantly more timing than you guys on the bottom end and midrange. My guess is this is increasing the overall efficiency of the motor, but I cannot prove that without a dyno, which I'm not willing to do untill its time for a rebuild.

-Yambo

morkusyambo

I'm gonna go out for a while to try a more aggressive tune. Be back in a few.

Kane

iTrader: (1)

Just stopping by.. good reading so far.

Brettus et al; just keep thinking FLOW not Pressure! The same size pully will flow different masses of air based on temp; restrictions, motor compression, etc... even at the same PSI numbers.

Brettus

iTrader: (2)

sure - but not 70-100 g/s more on the same pulley ..........................
Has to be another explanation .

joff

I'm pretty sure morkusyambo's higher MAF readings are due to the fact he rescaled his MAF voltage to g/s table with the accessport. This is a kludge I'm told you're forced into with tuning on the AP. Its not that he magically unlocked significantly more boost or flow with simple fuel/ignition tuning -- thats just silly.

The unmodified MAF table doesn't even have voltage -> flow mappings above (IIRC) 365 g/s (approx 4.7 volts) You can change/add entries into the interpolation table for voltage/MAF pairs above 4.7V/365g by extrapolating the curve, but its anybody's guess what the real MAF values for voltages above 4.7V really are in stock diameter MAF housings. Even if you did have access to calibrated flow bench equipment to extend the voltage -> flow table, my experience with other types of sensors is that when you get close to the limits of the sensor, they become wildly inconsistant and will vary from sensor to sensor so reports of any readings above 4.7V/365g should be taken with a grain of salt.

In light of this fact, what everybody probably should be comparing instead of MAF numbers is MAF sensor voltages in stock diameter housings.

Thinking in terms of flow versus pressure is a compromise the turbo folks bad at math make because of inaccurate pressure measurement. Turbo's create variable exhaust backpressure that not only can impede power, but it re-expands in the carry-over volume from the exhaust -> intake cycle and fights boost in the manifold. This, combined with the aerodynamics of the sensor placement, seems to me whats making turbo tuners distrustful of boost measurement. The exhaust backpressure in a supercharger setup is 1) much less and 2)more predictable and boost tracks with MAF much better than on a turbo from the logs I've seen.

Brettus

iTrader: (2)

/\what he said

morkusyambo

So if I set my MAF to see 260g/s at 4.06 volts. Then on a datalog i record 255g/s, how do I know if that # is accurate or wrong?

If we cannot trust any reading above 365g/s, like you say, then does that also mean every turbo owner who has recorded #s above that are also wrong?? I only ask because I am trying to learn and am looking for productive answers....

morkusyambo

...as opposed to the opposite end of that spectrum

Brettus

iTrader: (2)

Not sure if you took that the wrong way morkus - i'm interested to learn about all this as well so take it with a grain of salt

morkusyambo

No worries. Your response proves you meant no harm. Its kind of frustrating to try tuning a car for several months and every time you think you're making progress, you end up going back to square 1 again, or being confused.

Kane

iTrader: (1)

That is why I go off of fuel.

ALL of these measurements are relative; even fuel is since injectors have a variance and not everyone get's theirs flow tested. But I find the fuel volume to be the most accurate for tuning.

IE - if you flow 1 lb/min of fuel and your AFR's are 10:1 then you can be pretty sure your moving 10 lb/min of air.

The problem with the AP is that is doesn't read injector durations directly... I am still trying to figure out if we can work around that.

As for the flow vs pressure thing....

Um, no - a) we have no port overlap b) if you can prove that 10 PSI of pressure is the same flow rate regardless of other variables - I'll give you $100.

I may not be that good at math; but I have forgotten more about air pressure than most people will ever know.

joff

As long as your A/F ratios are all good and ignition timing is what you want it to be, it doesn't matter if that g/s number is true-to-life accurate or wrong. Its just a number you're using for tuning and if it gets the results its doing its job. After modifying that table though it unfortunately can't be used anymore for comparison with another car unless its using the same table and same MAF setup. I personally found out that it also has side-effects with idle quality and stability.

FWIW, I don't think Pettit's reflash does this manipulation of the MAF-- I think they tweaked other tables and left the MAF calibration stock.

I wouldn't trust a lot of AP turbo owners MAF values as I'm pretty sure they are all tuned by Jeff and I'm pretty sure he plays around with that table to get the results he wants and then keeps it secret (?). Its also probably the quickest and easiest way to tune.

The only way I can think of to get any reading above 365 accurately would be for someone to calibrate our sensor/MAF/ECU setup with a more accurate flow bench. Simply extrapolating out the curve from 4.7V to 5V is tempting, but not accurate enough for comparison between cars until proven with something more substantial than "it seems to hold the AFR I wanted up there" -- fuel injectors and combustion efficiency are not something to calibrate a MAF against.

As far as your tune goes, what you've done is great and I look forward to hearing more!

I knew somebody would bite. :-) Such a sensitive bunch and that makes you fun to pick on...

I'm not talking about port overlap -- I'm talking about clearance volume. Do you really think all 1.3(654cc per rotor) L of volume is evacuated each turn of the rotor? How do you squeegee all that pressurized combusion gas out of the rotor bathtub? Port overlap doesn't help you there.

Ooh, I can make $100?

Lets say you have a intake manifold sitting at constant 10psi of boost measured right at the closed intake port of the engine. Now lets say the exhaust stroke happens to clear out all combustion gas (impossible) and is in perfect vacuum. The intake port opens. Air starts flowing because there is a pressure differential between the manifold (+10psi) and the combustion chamber (-14.7psi). At this point, the pressure in the combustion chamber will asymptotically approach +10psi (ignoring helmholtz effects) while the intake port is open. The longer and more area the port has, the faster this pressure rises in the chamber. The turbo compressor utilized to create this +10psi in the manifold has absolute no bearing on how much air is transferred in the intake stroke (assuming perfect intercooling). The turbine side does however -- it determines how much residual gas was carried over from the exhaust side due to the pressure it creates in the exhaust manifold.

Can I have my $100 now?

Kane

iTrader: (1)

Good info (brings up the intake tuning stuff again; which I am weak on but would love to develop further) - but an incomplete analogy.

EDIT:
First you have to prove the exhaust pressure from the turbo of choice caused enough backpressure to increase the air reversion from an NA motor... I am not going to bite on that one cause there are too many snails in the world.

Assuming that the transfer of that pressure (a.k.a. Pressurization of the combustion chamber) were to take place at the EXACT same ambient temperature (impossible with two different compressor set-ups, also impossible as every millisecond the air tract is at a slight pressure and temperature variation) - then the speed of air movement would be the same (same pressure differential); on two identical engines with the same intake timing - the final PPO2 would be identical as the intake port closes and begins to compress the air fuel mixture for the power stroke. At this point - you can directly measure pressure and equate it to power... all you have to do is set up that nice sterile test.


For the rest of us; we ultimately have to look at the MASS FLOW RATE - <- flow over there see it... not the PRESSURE - because the PPO2 (the part that makes power when combined with fuel) is entirely variable based on VOLUME, TEMPERATURE AND PRESSURE - (See General Gas Law - Physics 101) - but 20 moles, molecules (insert mass measurement of choice) of oxygen.... is always 20 moles, molecules (insert mass measurement of choice) of oxygen.

10 PSI of AIR <> 10 PSI of AIR unless all other variables are identical.

See www.ppo2performance.com to do the math yourself.

Kane

iTrader: (1)

I was actually defending the SC (in the SC thread of all places)... so I am going to go on a limb and say I am not particularly sensitive... I just don't like stupidity.

I am also not a huge fan of your tuning recommendation to ignore the calculated values of the MAF and just work your own scale. If you have the means (which we do) to get all of the pertinant info into a tune; then you need to by all means do it.

By messing with your Calculated Loads (via the MAF g/sec); you affect fueling, timing, OMP volumes... basically the whole motor in ways that not all of us can forsee (as the entire PCM is still not open to us)... so; I am thinking that is bad advice.


No $100 for you; sorry. But hey you made a friend! The clearance information was a nice touch.

olddragger

iTrader: (3)

good conversation--i too have learned something here as I didnt know folks were messing with the maf scale!!
Correct me if i am wrong but dont we have a small amount of seal leakage from chamber to chamber going on also?
Damn--just got news someone is using my cc number---i hate thieves. I have never lost it and only use it to buy car stuff. Well i shut her down tonight. Damage less than $100 which i shouldnt have to pay for.
olddragger

Moon Assad

Yeh, it would be nice to have the MAF scaled to match HP output to the wheels or atleast come close + or - 10 or so. If that happened a dyno would be rendered usless.

Brettus

iTrader: (2)

yeh - thanks for the party money OD

Brettus

iTrader: (2)

with a turbo car I think it is already ......... pretty much . SC car pehaps down 20 whp on maf numbers ?

Moon Assad

So if its making anything under 380 HP its a stable tune as mentioned before about false reading anywere above 380 on MAF was it.

Brettus

iTrader: (2)

/\ sorry don't understand the sentence