Dyno Comparison Text: DBX VS PMAS MAF

[Addermk2]

I see. That's a good point - I hadn't thought about that when I was running through this in my head.

Couple things here:

1) I have to agree with modo on the bypass/BOV comment. Functionally they do the same thing. A speed density setup (i.e. one in a FAST or AEM) will not care where the vented air goes to. In a MAF setup, the situation would obviously be different.

2) I think Addermk2 raises a good question about why Ford elected to move the IAT sensor from the #5 runner on foxbody cars to the air inlet pipe before the throttle body on the 94-95 5.0s. Fundamentally, my preference would indeed be for the #5 runner, but it does beg the question... why did a room full of engineers at Ford move it to the inlet?

3) I still don't know why a 90mm LMAF will peg at such a low horsepower number. What is so different between that meter and a similarly-sized aftermarket meter that one outperforms the other to such an extent?

Paul.

Ultimately, it doesnt come down to a matter of port size. 76mm, 80mm, 90mm, 97mm.. wtf/e Its how the electronics are set and what values and resistances are carried over for the "calibration" of said piece... X voltage = Y air flow

think of it like the difference between a narrow band and wide band O2 sensor
both measure exhaust gas content. one goes from 0-1v, one goes from 0-5v... both do the same job.. they just read different

 

[modo]

i have been playing with mustangs since the mid 90s. you see that car in my signature. 9.20s on pump gas, self tuned.

now, a bov and a bypass functionally are the same, one dumps it back to the inlet, since it is metered the other dumps it. they both prevent compressor surge. now here is a fyi, all vortech and paxton kits today come with bypass valves. procharger kits come with bov due to the blow through maf

the inlet temp sensor is suspended in air and insulated, as long as it is functioning correctly it is not going to be heat soaked. i don't know about you but i want the readings controlling my ignition timing as close to the intake valve as possible. putting the iat sensor in out of the intake imo is bad practice. i like my pistons

i meant to type iv... i forgot i am on a sn board. only thing you got me on

lets get away from the bov vs bpv talk for right now because you clearly arent picking up what im putting down.
I can totally understand wanting to read IAT as close to the actual cylinder as possible. In a perfect world. yes, you are correct.

but what kind of velocities do you recon the air charge is moving at.. lets say... 4500RPM's, WOT...

now at at 900' down the 1/4... after the car has been sitting in the staging lanes for a half hour.do you really think the ECM is gonna read two terribly different things from the IAT vs the ACT? Sure there may be SOME variance.. but from a tuning perspective... its already covered.

if you took the temps from the discharge temp to the #5 runner i would bet there is a solid difference between the two regardless of velocity. here is a prime example on how not taking the reading close to #5 will bite you in the ass. you are taking your reading in your inlet tube and the motor has fogger nozzles screwed into the runners of the upper intake.
do you really think the tuner is going to feel comfortable putting timing tables in without knowing what effect the n20 had on the charge temps.

i'll tell you what a tune like that would have to have a lot more fuel in the cooler months then in the warmer ones

 

[Paul]

I see what you're saying Adder, but the tables that were posted show the MAF reading 4.6xx volts at over 1400 cfm of airflow. That should be more than adequate to cover 450 horsepower, shouldn't it? If perhaps the transfer function in the LMFA was programmed to send a max 5 volt reading at like 850 cfm, then that would make more sense to me.

Modo - I'm not sure I understand what you're saying about resolution vs injector size. I can see the resolution of the meter affecting drivability and idle quality since there are fewer data points (voltage points) vs the intake airflow cfm, but I don't understand how that relates to injector size.

Paul.

 

[Addermk2]

if you took the temps from the discharge temp to the #5 runner i would bet there is a solid difference between the two regardless of velocity. here is a prime example on how not taking the reading close to #5 will bite you in the ass. you are taking your reading in your inlet tube and the motor has fogger nozzles screwed into the runners of the upper intake.
do you really think the tuner is going to feel comfortable putting timing tables in without knowing what effect the n20 had on the charge temps.

i'll tell you what a tune like that would have to have a lot more fuel in the cooler months then in the warmer ones

exactly why my fogger nozzle was BEFORE my IAT :thumbsup:

 

[Paul]

Oh, and P.S.

This thread went from The Suck to The Awesome in no time flat. See what happens when we share? Don't all of you feel better now? :tongue3:

 

[LAFENATU]

LOL...

A Plethra(sp) of knowledge up in this b1tch haha...

 

[modo]

if you took the temps from the discharge temp to the #5 runner i would bet there is a solid difference between the two regardless of velocity. here is a prime example on how not taking the reading close to #5 will bite you in the ass. you are taking your reading in your inlet tube and the motor has fogger nozzles screwed into the runners of the upper intake.
do you really think the tuner is going to feel comfortable putting timing tables in without knowing what effect the n20 had on the charge temps.

i'll tell you what a tune like that would have to have a lot more fuel in the cooler months then in the warmer ones

exactly why my fogger nozzle was BEFORE my IAT :thumbsup:

yeah and im sure it was a tiny shot not a big boy shot... one thing about the efi sbf intake design is number 7 and number 8 get a lot more air then the rest. take a egt reading on a dyno between all cylinders and i bet money every time you will see 7/8 are leaner. it only gets worse with a power adder. i have to add almost 2% more fuel on them two cylinders to keep the egts down to prevent a ring land from lifting

 

[Addermk2]

LOL...

A Plethra(sp) of knowledge up in this ***** haha...

lol.. dont worry... i cant spell either!!

SPELL CHECK FTMFW!

 

[Addermk2]

yeah and im sure it was a tiny shot not a big boy shot... one thing about the efi sbf intake design is number 7 and number 8 get a lot more air then the rest. take a egt reading on a dyno between all cylinders and i bet money every time you will see 7/8 are leaner. it only gets worse with a power adder. i have to add almost 2% more fuel on them two cylinders to keep the egts down to prevent a ring land from lifting

yea.. 150 is indeed a tiny shot... however some of us actually use old school tricks to our advantage... I'm running a Victor single plane with an eddy elbow. and my EGT's are pretty even. I get a bit hotter in #2 actually

 

[modo]

alright ladies its almost 1.30 on the right coast and i have work in a few hours

 

[LAFENATU]

Peace out dudes. Work in...7 hours

 

[Addermk2]

woohoo... day off tomorrow!!!

 

[Paul]

I have to wake up at 5:30. F U C K.

Till tomorrow gentleman!

 

[Venom351R]

well good for the LMAF, I could care less how much power it supports or does not support. The fact is its sitting on the bench in the garage and thats where its going to stay as far as Im concerned. Im not saying its a crap meter I just didn't like it, Im not saying a PMAS is better just b/c its more expensive, what I am saying is that a PMAS meter is better just b/c its flat out a better meter.

 

[Venom351R]

Here are the results. It was tuned w/ a base timing of 12* moved up from the previous 10* Picked up a few HP over all but the power increased quite a bit throughout the RPM range. Still pulls really hard to 6,000

 

[96_SVT_Cobra]

nice #s

 

[BruhBrahBrad]

Not trying to be rude but aren't those numbers maybe a lil bit, Iono, not worth the extra cubes? I would expect more from a 351w with those mods.

 

[duh09]

So have you finannly got it running good now? I'm happy for you. That car's a beauty.

 

[Venom351R]

Not trying to be rude but aren't those numbers maybe a lil bit, Iono, not worth the extra cubes? I would expect more from a 351w with those mods.

The heads are not the best for the combo, Im running cats and shorty headers. With that said the numbers are right where they should be.

Thanks to everyone else

 

[Paul]

Glad it's running well dude.