joff

You just don't give up do you?

What dya know -- I was right all along Kane. How do you like them apples?

Lets do some math shall we? How about we find out what needs to change in the environment to accomodate a 80-100g/s rise in MAF flow on a twin-screw. For exercise purposes, lets say we see what it takes for 80g/s rise to morkus's 411g/s reading.

Lets say baseline (-80g/s) MAF reading was done at sea level maybe at around 60degF.

80g/s extra air (331g/s -> 411g/s) ends up being about 24% more air density. Now, lets see how much the temperature would have to drop at the same altitude/humidity to realize this delta.

Density of dry winter air at sea level at 60degF(15C/288K) = 1.206 kg/m^3

Okay -- so this + 24% is = 1.496 kg/m^3

Air would have to change density to 1.496 kg/m^3 to accomodate a +80 g/s extra flow rate.

What temperature is that? ... solving for T in 1.496 = 100000 / ( T * 287.05) =

-42 degrees fahrenheit. Thats damn cold. Over a 100degF advantage in ambient temps would be required to accomodate that flow difference! Did it get that cold in lower Alabama yesterday yambo?

You can do the math for elevation. Keep in mind yambo seems to be in lower Alabama and the current best flow I think was taken in Florida.

Looking forward to hearing what inconsequential detail I left out this time...

Moon Assad

Its not scaled the same as Deon scaled the Pettit tune. No, I didnt ask anyone but its a thought.

morkusyambo

Come on guys. Keep it civil so we can all learn something here.

I don't know if it means anything, but it was less than 40 degrees outside when I recorded those #s.

Moon Assad

Also, did you notice a gain while tunning or on a colder day. was there an immediate change in maf when you dumped the base tune from Pettit to the AP, I think I remember Jeff saying somthing about he should do that because it was the rite thing to do, he hadent done it yet.

Bastage

iTrader: (1)

Check this out:

https://www.rx8club.com/showpost.php...&postcount=162

Had fun driving back home from Juan's (aka Smooth Jazz Rotary Yoda) Saturday night. The Sunday morning traditional drive to get fresh baked bread was even more fun. I can't wait to see what this car can do after a tune.

olddragger

iTrader: (3)

nice dude--nice. I love beta testers!!
The blues are holding ya? The temps staying down?
The real tests will be this summer.
OD

Bastage

iTrader: (1)

After beating the **** out of it the highest temp I saw was 208F. I think I can survive an autocross event this summer, but we'll see. By then I will probably have the JuanSport supplemental radiator mod.

I'm actually using modded yellows, matched at 570 ccs each. I'm getting 11.0-11.4 AFRs, so It'll definitely need a retune. I also need to retune my driving style.

olddragger

iTrader: (3)

AGGGGGG_--- does make one desire to be a beta!!!
OD

Rotr8

iTrader: (2)

Dont forget about these, I sent Pettit a brand new flow pan a month ago Cam and Moon are now working out all the kinks included a electronically controlled valve so I can cut the flow in the winter...

Moon Assad

Thread jack- Have you ever run out of gas and either pushed your car or costed to the next gas station, well!!!

http://www.youtube.com/watch?v=z985xdXW-3w

Kane

iTrader: (1)

I was originally not sure how to take Joffs last post; since I kinda wanted to get my Irish up... which is stupid.

Those that know me personally I think can atest to the fact that ego doesn't really drive my life (or they can all think I am a pretentious a-hole; you never know); and I could rather care less if I am thought badly of someone I will never likely meet... but what I do care about is the people who are trying to get into this stuff keep making mistakes because those that know WTF is going on are too lazy to speak clearly in a public forum... I have an FI-ed car... I don't need myself to tell myself how to build or tune it. But I want everyone to have as much fun as I do; and if I can get peoples head around the physics and math involved then maybe a few more will.

So - I am going to assume among all the cross talk we missed the actual timeline and the core of the argument in order for me to be called out for being a stupid, fanboi seeking individual... I have re-capped the issues in the assumption that I was misunderstood.

so a Delta from 330g/s to 400g/s.... but we now know things were scaled; kinda of a mute point anyway. But this started it all. An 18%-20% change due to timing / tuning and air temps???? Yeah that would be freaking Impossible.....

My original statement... that is the entire post; no other "turbo bullshit" was in there. I am not Jeff.

Now read my info....

So now we can go back to the PPO2 argument et al.... if you are bored. Or you can skip to the part where you agree with me....

So ultimately.... what you are TRYING to say is this...
So once more... no $100 for you.

If anyone doesn't understand what it is I am trying to say please let me know. If you disagree with my information show me the math so I can refine my thoughts.... if you just want to be a toolbag; then I'm gonna ignore you. If you wanna be an e-thug then don't beat around the bush... just call me a homo and we can skip to the end of the argument.

Brettus

iTrader: (2)

What's wrong with being a ...................

Kane

iTrader: (1)

HEH HEH....

I just bumped my own toolbag thread.

Brettus

iTrader: (2)

that is a **** load of cooling ya got there ......

Rotr8

iTrader: (2)

not yet but it will be going on my car in spring, thats actually Cam's car...

Phil's 8

iTrader: (3)

Not having been to Flordia in 50 or so years, I don't remember the high temps there during the summer and the road surface temps. I think it's a great idea, looks good but I'm not sure it would work here in Vegas during the summer. The heat reflecting off the road surface is too great. During the really hot days, the asphalt is soft it's so hot (trucks can leave impressions of their weight at intersections). There would be no water in the air to aid cooling. My first impression would be that it would aid heating not cooling (in the summer). I understand heat transfer and if one of you can explain how this would not do the opposite of what is intended I will listen very closely.

Bastage

iTrader: (1)

I would think that it would work even in Vegas, as long as your not sitting idle for long periods of time. Those radiators are oriented parallel to the ground, so as your moving, I believe both sides are getting blasted by the air, but it favors the air from above, as I think they have some plastic channeling the air downwards into the radiators. It wouldn't work as well, given the lack of humidity, but I still think it would help. Plus you have a greater volume of coolant, that probably helps some too.

joff

You are not a homo, stupid, or a toolbag (whatever that is) -- you're just fun. People take internet arguments so seriously around here. It will soon be a lost sport I fear -- sort of like how many sci-fi utopian visions imply we will ban all sports someday because everybody gets so emotionally hurt when the other team scores. At the end of a game, winners do not call the losers homos and the losers do not seek vengeance outside the arena -- they shake hands and say "good game"

In my experience, people that go on a soapbox about how ego doesn't drive their life -- well -- ego usually drives their life, and they just don't know it yet. Theres really nothing wrong with it as long as you are conscious of it.

Back to that $100 huh? I thought we were done with this. I did have a $100 challenge for you too ya know. Good argument tactic though -- it showed that you were very motivated by ego to prove me wrong and wanted to bring the full brunt of your credibility to the party, which made all this more fun.

Is this the point of this post? To ask if everybody understands? You are so keen on playing the teacher role here aren't you. Everybody understands flow vs. pressure here (its not rocket science) and that was never the debate, the debate was explaining morkusyambo's MAF readings.

If anything, in explaining the MAF readings, I was bringing up to the class a related discrepancy between flow and constant pressure, volume and temperature for turbo tuners. Normally -- in a classroom setting -- only the teacher is allowed to say when we're going to the next chapter and any student saying so is viewed as subordinate. Maybe thats why you raised the $100 challenge -- a last resort argument to regain control over the class from a troublemaker student on his first day at a new school.

I apologize to thread readers for this off-topic post (I really thought Kane was done with this). I talked to Cam at 7stock about that floorpan radiator setup he was cooking up -- very similar as a sort of hybrid V-mount setup which is very common and effective on FDs. Its great to see it real -- any idea when he's thinking on selling it? Is the floorpan still the same plastic piece or was that new too?

olddragger

iTrader: (3)

its the stock piece and they utilize two of the a/w intercooler heat exchangers for this job also. It works and all rx8's need it not just the fi guys.
OD

Rotr8

iTrader: (2)

yup, notice the top pic, this is where Cam and Moon are experimenting with how much air flow to direct down through the assembly with different sized scoops... also the final item upon my request was a way to deactivate it during winter(up here its cold) so at first they discussed a manual valve, now on the sketchboard is a electronically controlled valve that could have a switch in the cockpit...

olddragger

iTrader: (3)

for those that are unaware this system is feed through a non thermostatically controlled supply. Its the return heater hose. It is routed back through the radiator side gap to feed into the thermostat housing as the heater hose normally would.
The electronically controlled thermostat yall are speaking of would affect the heater as the heater would not have any flow until it opens.
I have ran mine (with the stock thermostat) when ambient is at 30F and it took only maybe 3 mins to warm up to 140F. I warmed the car for approx 2 mins idling after cranking and then 1 min of very low load driving(not over 3K). It did fully warm to 180F (coolant and oil) with in 5-7 miles at approx 45mph.
Northen folks may want more warming ability--but for the southeast its not needed.
OD

Red Devil

What cooling upgrades do you have? What water/coolant split?

Bastage

iTrader: (1)

From the original Pettit setup, only bigger intercooler reservoire with a rerouted return hose (away from the alternator), and water/methanol injection. I'm sure 208F is not where I'd be in the heat of the Florida summer if I drive it hard, as I'm now running signifcantly more boost. I will definitely get the extra heat exchangers before this summer.

I autocrossed June/July/August/September of last year at least once each month (with only 8-9 lbs of boost), and my engine still pulls 19 inHG of vacuum at normal operating temperatures.

morkusyambo

Well, I'm still not sure what to make of my MAF readings, but I created my own tune with the AP(took me a long time) and I am enjoying it. If Joff, or anyone else with an AP wants to try it, let me know and i'll send you the map. My disclaimer is that it is still a work in progress, and is VERY aggressive in the bottom 2/3 of the powerband. Use at your own risk. I take no responsibility for what happens.

-Yambo

joff

I think you probably did the right thing by scaling the MAF. My best guess is that the reason everybody is finding they have to scale the MAF is because at high flow rates our fuel pressure is dropping and the effective fuel pressure across the injector -> manifold junction is less because of the presence of boost in the manifold. The stock ECU algorithms probably (?) are not accomodating this sufficiently and we have to tell the ECU there is more air going into the engine than there really is to force the ECU to give us the right injector duty cycle. The injector flow may also be slightly non-linear with higher duty cycles which may not be figured in by the ECU either.

Basically, what you're doing is calibrating out fuel system inconsitencies with your MAF -- not the other way around (calibrating your MAF with your O2 sensor and fuel injectors) Your MAF in its stock calibration is as good as Mazda originally designed in -- hard to improve on that.

If you wouldn't mind, please send me your tune to joff@embeddedARM.com -- I'd very much like to see it.