rons 00z

iTrader: (10)

m_t_o just made me think of something. now the maf is a heated resistor right? so im assuming the colder it gets (via more air blowing on it) the more resistance it's gonna show or tell the ecm. so if you took two maf's and wired them together in a series circuit it would double the resistance. therefore, you wouldnt max out your maf anymore because the ecm is seeing say 200 ohms instead of 100 ohms. although you would have to reprogram the ecm for it to understand the bigger sensor or increased value of resistance.

as for the maf's you can either mount them side by side to have more cfm and just y pipe it to the t/b (90mm fast) which then your maf will no longer be a bottle neck. or im guessing you could put them inline with each other to have more velocity into the intake which ever you prefer or however you want to do it. i have know clue on how to program so not sure if this would work or not.

does this make any sence or do i sound like the village idiot right now?

M_T_0

The sensor would still max out, if the sensor swing is from 5 - 1 ohms and you add 5 ohms to it then the swing is from 10 - 6 ohms and you havent accomplished a thing. a hot wire mass flow sensor works based on the the fact that air moving over a heated wire cools it, the faster and denser the air is the faster it cools it, if you do anything to slow the air down across the wire like enlarging the opening or bypassing air then you increase the range of the sensor. I dont think that enlarging the MAF will do enough but you can bypass air around it fairly easily. if the bypassed air is fairly linear across the flow range IE if the total flow is 200 cfm and 20 cfm is going thru the bypass then the sensor would see 180 cfm and report it to the PCM then at 1000 cfm the sensor is seeing 900 cfm and the bypass is taking 100 cfm. so lets say that the sensor maxs out at 1600 cfm but with this setup it would still indicate correctly (after calabration) all the way to 1760 cfm. what would be lost with this approach is the accuracy at low flow, because most sensors are not as accurate at the ends of there range, but if the low flow that the sensor is required to read is 100 cfm then it would only be off by 10 cfm at that point, and should still be in an accurate portion of its range.

M_T_0

also the sensor works in reverse the more air the colder the wire gets and the lower the resistance.

Team ZR-1

IMHO,

The MAF is not the only delimiting factor when using FI.
There is several timing lookup tables in the PCM calibration the adaptive stratagy software uses for making timing decisions.
The maximum amount of air/fuel these tables understands is 1.2 grms/cyc so no matter what you do as to the MAF output you still have to deal with the fact a cyclinder only has enough space for all that increased air/fuel.

Add the fact to fight off the lean AFR, hot IAT and knock issues you need to use larger injectors and the hardware of the PCM was not really designed to use narrow injector pulse widths to solve FI issues you either need to use another engine management subsystem to handle those issues or you have to do a lot of lying to the PCM via tuning and clipping the MAF's output frequency which also then fools the torque management and line pressure functions.

As to LPE, I have tuned 2 dual turbo C5s and 2 SC'd C5s that were tuned by LPE and none were tuned that great.

As to FI RWHP, I say lots of marketing hype, I know of at least one so called super duper SC shop who loves to claim 650 RWHP but when tested we found numbers greatly bloated where shop had put the weather station on top of the engine to give the "corrected" SAE values that they use to market themselves but I know of at least 10 engines they SC'd that are now trashed.

Using a Dynojet chassis dyno may be great to get pumped up RWHP numbers but are not the tool to use for tuning since you cannot do static loading, cannot get engine to 100% engine load and cannot allow PCM to function under high load for more then 15 seconds of a pull.

A load bearing dyno like a Mustang would be a better testbed path but frankly real world street driving while capturing the PCM with a good scanner will allow a FI engine to be dialed in with and without boost since the tuning values requirements will be like night and day

Rob Raymer

I agree for the most part. But you have to have some point of reference to compare things. And a Dynojet is typically pretty easy to find. But more importantly, I would hope you wouldn't need to pull an FI car for 15 seconds straight on the dyno in the first place.

We have done both. Tuned on and off the dyno with a Wideband. And for the most part, it's not that difficult to compensate for the variance. Even at the 700rwhp level, the variance isn't that great.

But overall, I agree.

cablebandit

iTrader: (37)

Rob have you ever used a Mustang dyno? I see you are doing things another way....street and dynojet for tuning. I did that last time with very good results as far as getting my tune right. The really cool thing about the Mustang dyno (as you may know) is you can tune your part throttle stuff too. You can have it setup to simulate 70mph on the interstate...going up hill...all kind of stuff. Also, if you have a full weight car, all your tuning is exactly the same as on the street. Boost will be the same as well as a/f. You can even do a 1/4 mile run on the dyno!!! You may know all this but I'm sure some don't so I slid it in here I am NOT debating your methods as they are working for you perfectly. Just want to offer up some more info since so many look at this particular thread. Are you going to SC next weekend? I hope to meet you there!

onfire

iTrader: (17)

Team ZR1, what specifically was not correct about the LPE tune? Maybe you can elaborate on how LPE can use a boost controller with 6psi and 15 psi settings on the same tune....I know three LPE TT's and all are perfectly tuned...never had a problem with idle,surge or wot.

rons 00z

iTrader: (10)

i can see how THE sensor would max out but not both. if you had two paths for air to go through ie. two maf's then you wouldnt be maxing out the sensor's. you would have 150mm instead of 75mm for air to pass through the maf's. basicly less air would go through one sensor because more is going through both sensors. the pcm wouldnt have a problem with the new values because you would just program it for the diffrence in maf value. as you would for a diffrent aftermarket maf.

Texas Terminator

man, where is the pissing match smilys?

so is there a viable answer to the original question? i am borderline with my MAF as well and would like to know and haven't seen much in the line of an answer anywhere in this novel.

M_T_0

yes that was what I was indicating, also there is no need to install a second sensor, just bypass a fixed % of the air around the sensor. The MAF signal would be proportional to the air flow and could be scaled to read correctly. looking on the various web sites I find a lot of larger aftermarket MAF's do these also max out at hi airflow?

slow

iTrader: (7)

2 75mm =/= 150 mm

aftermarket mafs give a lower output than the stock ones, so you can get a little more headroom that way.

bypassing a fixed % isnot a good idea, as it makes it hard to tune for idle, ect...

M_T_0

ok I hear you but what is the problem with idle tune? is it the loss of accuracy at the lower flow across the MAF? or is there something else that i'm missing?