87400tpi

This seems to have been one of the major beliefs on this board.We all seen ski_down_it seems to be defying this well know "fact".Where the myth came from is not my consern.Is it fact or fiction?I'm looking for someone to respond with data,not with ASSumtions or personal attacks.here it is boys: I report,you decide

Grim Reaper

Yes, Ski obtained some great times. 11.15 @ 123 & 11.14 @ 123.27 suggest that Ski is producing some excellent HP. Now Ski doesn't mention his total race weight, but if I assume SKi's total race weight of only 3,400 lbs (including himself and fuel), his HP (based on more formulas) suggest 485-500 HP. If his total race weight is more than 3,400 libs, he's making more HP.

The HP forumlas I used were:

Weight/((et/5.825)^3) = HP and
(MPH/234)^3 x Weight = HP

both yield roughly the same.

What I find more interesting is Ski's ability to run only 24# injectors at turn those times. The "Injector Sizing Formula" say that even at 100%DC, he would only produce 384 HP. (24 x 2 x 8 x 100%). Increasing fuel pressure will make those injectors flow more, but to make up a 100 HP deficiency it will have to be a lot more than Ski's fuel pressure (45 psi). Using another formula, SVO 24#s (rated at 38 psi) = 26.12 @ 45 psi. This only equates to 418 HP.

According to more HP/ET formulas (for 418 HP), Ski would have to get his total race weight down below 3,000 lbs (driver and fuel included). That's quite light for a 67 Chevelle in my opinion (I'm assuming that's the car Ski's running).

So you basically have two conclusions: Ski is running a very light car or the formulas aren't always perfectly correct. I've always felt that "rules of thumb" should only be used for an "indicator" and not taken as gospel. Think about how many times people have said something won't work (based on current theories or formulas) only to be prove the formulas wrong.

Then you have all the mathematicians trying to rethink the formula to find out what factor is affecting it. Maybe it is best that racers are poor mathematicians so they won't know that they aren't suppose to do it.

SATURN5

I beleive ski is running a C4 vette. IIRC the chevelle has a big block.

Morley

He said they were 24# SVO's. In which case if he is running them at GM reccomended pressure (or higher) he is probably closer to 30#, which is better fueling than 24#'s (Bosch, accel etc) could supply.

Grim Reaper

You must have skipped over the part where I discuss the injectors. As I said, I acknowledge that they are SVO 24s, which Ford rates at 38 psi (GM uses 43.5). Ski already said he is running 45 psi.

Using the Fuel Pressure formula:
(New_psi/Old_psi)^SQRT x Old_Flow = New_Flow

24# SVOs @ 38 psi = 26.18# @ 45 psi.

To equate to 30#, the pressure would have to be 60 psi.

Grim Reaper

Thanks. Still I suspect the C4 has a total race weight greater than 3,000 lbs (including driver & fuel).

Morley

Why, yes, I did.

Einstein already proved that math isn't always correct (yes, I saw where you acknowledged this) and in fact can sometimes be 100% wrong. There are no absolute laws laws of physics...only what we perceive them to be.

For instance, Did you know that the F-4 (Phantom II) and B-52 (Stratofortress) were 2 of the last planes designed without the aid of computers?
When the designs were entered into the computers used for aircraft design (at a much later date) it returned the verdict that neither plane could fly. There wasn't enough lift to overcome the weight and not enough thrust to counter the drag. Oddly enough both planes fly quite well, the F-4 can hit near mach 3 and the B-52 used to hold the distance record for unrefueled flight (3/4 of the way around the earth) before the Rutan's made it all the way around the earth.

Math is nice for ballpark ideas, but actual pratical application is the only real teltale.

Grumpy

In another post, I mentioned there was a GN at Muncie running high 8 sec ETs. Using a stock MAF, and ECM.

Without a doubt he is making over 350 HP.
Without a doubt he is hammering the calibration since he has no resolution about what the engine is using air wise, as far as the ecm goes. Again, when you peg the MAF your running in Alpha-N mode. The only thing you have to taylor the AFR is a RPM correction.

Can you go fast on a MAF, heck yes.
But with the MAP system you have some resolution and better control of the fuel curve.

The is a huge difference from just stating facts, to saying one is better then the other.

If any actuals looks at the original quote, nothing has been an exception to what I said. All it says is that your OUT OF RESOLUTION, at that HP level. And if you run big enough injectors to just be at hammering the calibration then you may have BL problems. Glad to see that old quote is still correct.

It's when you try to read into what's being said and draw improper conclusions you can get lost. Careful reading shows no where in that quote does it say that the MAF will only support that HP, it's just that you run out of RESOLUTION at that level.

TRAXION

I think it's entirely possible, even according the formulas to run those times with 24# SVOs.

Ski's BSFC is probably not 0.5. I would bet he is somewhere around 0.42 - 0.45. Assuming 500hp he would need 26.3 lb/hr injectors for 0.42 BSFC and 28.1 lb/hr for a 0.45 BSFC. Both of those flow ratings are easily attainable from the 24# SVOs via pressure changes. You would need 52psi to hit the 28.1 rating with 24# SVOs.

This ASSumes 100% DC. I've run the 24% SVOs at 90% DC and was able to crank that up to 93% DC with a measureable increase in fuel.

I definitely think it's possible. Plus - I also know an LT1 guy with stock GM 24lb injectors that was running 119mph in the 1/4 mile ... I couldn't explain it - but he was doing it. The injectors were static but still delivering plenty of fuel to support 119mph in a 3500lb car.

Tim

Grumpy

Nice to see the old data still standing up to the test of time.

Have you read the other 3,000 posts of mine, and are clear on them also?. Go back a few years, and you can find some errors, but this ain't one of them. You know like 5-6-7 years ago when we were still trying to work out how an ecm worked. And what tables were even available to adjust.

funstick

are you familiar with PWM. id bet at 100% dc thats the way his injectors are behaving. either that or the theory ive been toying around with lately about injector sizing is correct.

the other thing to consider is engine rpm. ski has mentioned numersou times he shifting under 5500rpm. a good idea with a 406 to be honest.

there are plenty of factors to think about in all reality. there also an idea ive been kicking around that as PW goes up the static amount of fuel delivery follows a curve not linear line of flow. then again have you ever seen homw much presure thee is avaiable in your kitchen fuacet when you first open the valve as opposed to its steady state flow ?

there is most likely a good explanation. question is can people accept it.

also running quasi synchornos could be buying time as well.

87400tpi

I'm not convinced,grumpy.Sky has'nt even really modding/scaling maf tables.Nor did you even ask if he has hit 255gms @redline.Nobody has even ask him his gms@redline.This is a fundamental question overlooked here.He is flowing alot more than 450cfms.which leads me to the next thing.How can you say just because the code uses gr/sec,that = anything in the physical world.Just because the the last maf table maxes at 255 gr/sec does'nt mean the car is using 450 cfms.Again,ski has shattered that.He has alot more than 350 hp.No loss in drivability and a solid a/f ratio confirmed by a w/b sensor.No loss of nothing,in fact his engine runs great.Again you don't even have a clue if he has hit 255@redline.Even if he did it does'nt really matter.He has a torque monster.Why dont you guys see how much ms of pulse width it takes to support 400+torque @1500 rpms or so.He is winning this battle with gravity on torque.I'm sure if you do the math there is plenty of pulse width to support let's say 400+ torque from 1000-5000.What's that add up to?
hmm, seems like one of those times,huh?....

87400tpi

There is not one person that I know of on this board that is stating maf is better than anything.It is possible for maf to outperform SD in some situations.It is also possible to compare SD vs maf without confusing which system is more advanced.It would take a real idiot to think the 165 is more advanced than the 730.But the fact remains Ski retains full control of the fuel curve.So how is he losing resolution to the point of being hard on the engine,I must have missed that

87400tpi

Math is always correct,it's just the theoretical application of it that CAN be flawed.2+2 will always = 4,regardless of ones perception of their reality.

HighHopes85

Since I haven't seen the true equation posted, I'm gonna crunch it out.

The good thing about air is that it is predictable. Take worst case scenario and you suffocate in the room you are sitting in because all the air goes into the upper right-hand corner of the room. It could happen. It ain't gonna happen.

mass flow rate (m_dot) is related to volumetric flow rate (V_dot) through the following...

m_dot = density * V_dot

That's basic thermo stuff for you. It's what we as humans have grown to live by.

Like I said, air is predictable. If you take air at 1atm and at 80*F, you are going to be really hard-pressed to find a density that isn't 0.074 lbm/ft^3 under relatively standard conditions. This is just the sensor aspect of it. There's no Otto cycle theory in it (or whatever model you want to use), because the air hasn't hit the engine yet.

So if you do the math, you'll see where the constant that Grumpy used came from. So there was the equation, it matches Grumpy's constant...have at it.

Good luck, 85Y

Grim Reaper

No, I think Tim hit the nail on the head. The "Injector Sizing Formula" uses .5 BSFC. If you can improve the BSFC, then you would be able to run a smaller injector as you are burning less fuel for a given HP.

A BSFC of .42 would permit Ski to run 24 SVO injectors @45 psi and make close to the 500 HP (depending on weight). However, he is most likely close to 100% and risks going static.

Grumpy

The only time the gm/sec., stuff mentioned in the tables is when the intake tract is oem stock, along with the engine.

Once you change any of that the gm/sec math used as gm/sec math in the cal is trash.

It doens't matter what the gm/sec displayed on a scanner shows. Since it's just reporting what the ecm is calculating, and the ecm has no clue about if the intake tract or engine is stock.

You can scale it anyway you want to.

Someone needs to put all the accurate MAF stuff in one place, so folks can refer to it in masse, so they can get an accurate complete picture without this silly constant repeatition of just elements of it.

Just because you dump enough fuel in to get a decent HP doesn't mean you have enough resolution to accurately do it.

If you think the MAF has the resolution to support X hp, set the PE enable to 100%, and try to fuel the motor with just the MAF tables, and see where you get.

And peg the MAF does not mean 255, it means just as high as it will read in your application.

87400tpi

Ok,so the equation is technically right,but not correct?It fails to take in account bsfc.We are all assuming things with ski's combo.This equation is held together on the premice ski's bsfc being what?,.42 .He better have a killer fuel pump because his pressure would be through the roof.We need some hard data from ski to understand this monster of an engine.But intill we get info from him this subject remains inconclusive.I think we all can agree that,yes?He might be losing control of the calibration at this point.But like I have said,he appears to have total control of a/f and great drivability.This has been a good post.There is no bs just a solid discussion . .While we wait for ski to get back to collect the data I have another question.Oh yeah??Well that honestly is way off basic maf physics.It takes only certain amount of air for the maf to read 5 volts.If the maf is reading 5 volts then yes he is running out of MAF resolution.But the total calibration APPEARS stable.So how can you hammer the maf without reaching the 255.No matter what you do to the maf tables thew will peg to 255 if there is enough air passing the maf wire.

Grim Reaper

1) I assume you are talking about the CFM/HP formula. In revewing some results from "dyno programs" I have access to, there is indeed a relationship in the BHP, BSFC and CFM. The dyno programs show that a lower BSFC to produce a given HP will consume less air.

And example from the program with the same engine specs, shows an engine producing 236 HP @ 6,500 rpm has a BSFC of .675 and consumes 438 CFM. While the same engine producing 236 HP @ 4,000 rpm has a BSFC of only .505 and consumes 328 CFMs.

I suspect the formula you are using is simplified with an assumed BSFC of .5, much like the "rule of thumb" for injector sizing is: Inj_Size x 2 x #cyls = HP. The "x 2" is actually "divide by BSFC" and a dividing by .5 BSFC is the same a "x 2".

2) Yes, a BSFC of .42 is a very efficient engine for sure and tough to actual measure. The lower rpms of Ski's setup would tend to favor a lower BSFC than if he produced the same HP at higher revs according to the dyno program I used.

3) Yes, more info from Ski would be nice and eliminate some of the guessing and assumptions.

4) Yes, keeping to facts and having an open-mineded discussion without any emotionalism such as "SD vs MAF" does result in a more production thread.

Grumpy

I'll say it again.
When you run out of MAF, your in an Alpha-N mode.

Nope, you can set the scalers anyway you want. You can have the MAF read 131.8477653343 gm/sec at WOT, and still fuel the motor the same as if was reading 255.

If you were try some of what's been suggested you'd see what was going on. ie set the PE enable to 100% TPS. Try to run the motor without using the Alpha-N mode.
Better yet build a ecm test bench and with some good scanning software you could see what's going on, rather then speculating.

87400tpi

I'm not speculating nothing.I have set the pe enable to 90% with maf and gotten 128 blms across the boards.You can believe it or not but it is true.I did it some by tweaks to the maf+spark tables.This was done by trial and error.Not meticulous reading of the code.I have studied the haks for days/months,so don't get me wrong.But I could bet you a million dollars my maf system was tuned 110% CORRECT,better than OEM.

The tps% to enable pe will be on the list of questions to ski.It's hard to believe/verify his bsfc is .42 and consuming 450 cfms.That is some out of this world numbers,potentally.450 cfms,I guess my new 1000cfm tb is useless.This just doesn't add up.

If ski's maf sensor is reading 5 volts before redline then I will concede there might be problems with the code @ that hp level.But we need to get a list of info from ski.

I'll start,ski what is your maf gr/sec and pw at redline?I think the true way to get the maf data would be to tap the 5v maf wire, run it inside the car to a volt meter.See what the volts are at redine.If the volts are around 5v then run the next test.See at what rpm the maf output reaches 5v.What is your race weight,60ft times,altitude,?THere is a bunch of questions,guys help me out here.

Grim Reaper

Yes, but let's not make it the Spanish Inquisition either. I like to think of this a sharing of information discussion over a friendly coffee than a opinionated emotionalistic argument by a bunch of guys who had too many beers.

On the injector issue, it can be another "variable" in my opinion. I had a set of original 22# injectors that were rebuilt at one time. I recently swapped to SVO 24#s and I swear that my rebuilt 22#s gave more fuel than my SVOs.

87400tpi

I'm glad you brought that up.The reason of this post is not to call anybody out.I have alot of time working with maf.I still want to learn more though.Now I want to find out the effects ski's engine is having on the code.This will(I feel)aid in the spread of good maf tech.I can't count how many times I got bust maf info from some.I have had the 165 and now have 730.I like both systems.

ski_dwn_it

WOW guys, no wonder my ears have been ringing....:O

Let me first say thanks for the nice things you say about my car

I wish I could answer all your questions about PW etc, but I logged my runs at keystone during the runs and left the laptop on record between runs without saving the data, for some reason it did not save to the HD so the information was lost.

Since the exhaust is off the car, taking it out of my neighborhood for some street testing is gonna be less than possible in the near future, as I will have every cop in the tri-county area searching for me.

I can tell you some things though. First my race weight at NJ last year was 3350 with me in the car and ~1/4 tank of gas. My wife will vouch for me on this, I did not loose any weight this winter Instead I packed some on. I figured why go for the six pack when you can have the whole barrel :LOL....no its not that bad, j/k. Also at the track I used to be able to get away with 1/4 tank without pickup problems. With this setup I need to have at least 1/2 tank, about 4-5 more gallons to keep it fed. The gas must be plastered up on the back of the tank wall, away from the pickup.

As for the tuning methods I used: Here it is in the nutshell. I first set the injector constant to a value to achieve best BLM reading across the cell, nearest to 128. This is done in conjunction to spark table adjustments. Total advance on this now is ~38*

Other parameters like crank pulse width mult are adjusted to assist in startups, emmission equip delete is reflected on the tune as well. Idle is adjusted up to 950 RPM for the big cam, and to smooth it out a little.

This method worked VERY well for my 350 it took me a few iterations but it ran darn good, throttle resonse was great. On this setup, perhaps I got lucky, as I said the BLMs were 127-131 across the boards when I logged it for the first time. I really don't think it would be worth the effort get them all at 128. Do you? Now the throttle resonse is gross, if you have a passenger in the car and your not careful you can at nearly any RPM bounce there head off the headrest with a slight increase in peddle. increasing it sharply 1/8 throttle just lights up the tires, and it the TC is locked it sounds like it ripps the car apart it hit so hard. So personnally if Throttle response could get any better, I wouldn't even want it.

As for WOT, this is where I struggle with this whole debate of resolution etc. I am not fully clear here, I know what I do to get my desired AFR and it make perfect sense in my head, so perhaps someone can explain my wrong thinking if it is wrong.

We have got the part throttle tune, if BLMs are ~128 and the spark table is corrrect, let assume that. OK.

Now the deaded WOT. Here we rely on the WB02 for readings and adjust the open loop (PE AFR) vs RPM to get the desired FR for any given RPM. Right? Well that is what I do. Let me continue.

OK so you take the car to the strip or a place you can lay into it. You record the runs AFR in your head or log it etc. You review the readings vs RPM and increase where you need more fuel and decrease where your fat in the PE AFR vs RPM. Who cares what g/sec or CFM you are running. I don't even look at them at this point, or any point for that matter. I just don't see the relevance. IF the AFR is not 12.8 at a given RPM, then you change it however you need to to get it. Why would you need to know the air flow, if its leaner than 12.8 then you have too much air, if its fat then you have too much fuel.

Guys, why make it more difficult than that? Is it? Why worry about voltages of MAF wires, etc etc? If you reach a point in the tune where you can't richen up the system then yeah you have a injector problem or fuel problem, or if you can't lean it out (don't know how that can happen, but then you have an air problem. )

Obviously my engine has enough Air, obviously it has enough gas to maintain a given AFR, I am very confident I could make the AFR 12.0 or even 11.4(that is where it was after the first chip) then I did some figuring and got it up to 12.8. The air did not change any, so there must be quite a bit of injector left to have the 11.4 AFR before, without ever touching the FP of 45PSI. I have the stock fuel pump as far I know, unless someone else upgraded it when I was sleeping.

I have never touched the MAF tables on this tune. I did on my 350 for idle to get the BLMs to 128, but then it smelled more of gas and did not seem to idle as good so I went back to the 135-140 BLM. The 406 is around there too, but just as idle.

Please explain to me what I am missing? doesn't it boil down to this: You have x amount of air at any given instance, you need Y amount of fuel to achieve z AFR. You know that X is whateven the engine sucks in, and so you are basically just controlling Y (fuel) to achive the Z AFR.

Again please explain to me why I care if there is 255 g/sec incoming or 23000 g/sec? I know I need an AFR of 12.8, so you do what you need to with the PE AFR vs RPM? Both of them are independant of Air incoming or MAF meter reading etc. In the end they all work together, but in the end all I care about if an AFR of 12.8.

My person belief is that people make this 100X harder than it needs to be. I said it before in one of my posts, when has anyone seen an AFR graphed that went from:

RPM AFR
1000 11.8
1200 13.9
1500 12.2
1800 10.2
2000 12.8

But rather don't they have pretty smooth gradual transitions as the rpms increase? If they do then why would you need all kinds of control at each incriment. Think about what you are telling me.

If all this stuff I mention is wrong with my system/tune, you are telling me that I have probably a 9 sec car and I am just lucky that its running near 10s Yeah under closer observation the AFR might go +/- .2, but how much does that hurt, if it even is?

Please enlighten me to the resolution thing and why I care about the g/sec coming into my engine?

Corkvette and I are both doing the same thing. I would be happy at any of the trck we go to spend as much time as it takes going over our setups. We are not hinding anything, or have 5K dollar cranks and rods on out engines. You can go to the Corvette Forum and see my car go together from top to bottom and front to back if you like. All the components are readily available to everyone. What you won't see is the time in preperation making sure EVERYTHING was 100% from top to bottom, that the assmebly was balanced to under 1/2 gram, oil simulation weights were added during the balancing etc. These are the things that make between an engine that is a a 10sec one or a high 11s or 12s. 2 grams at 6500 RPM is like a 10lb hammer wipping back and forth, how many HPs do you think 8 of them fighting one another will cost you? I don't want to find out.

This will really blow your minds....Corky is only running 38psi on his #24 SVO injectors! He adjusts it up and down a pound for two depending on his stock o2 readings. Something even I can't figure out how he does, but it works for him, and believe me he is a contender in the eliminations where ever he shows up.

Look forward to hearing what you all have to say. I would be happy to share any and all information with you all.

Videos are posted in the TPI section of the runs if you like to see them, guess its a little more proof that we are actually doing that we say we are. I'm sure that is linguring in some minds.

TRAXION

IMHO - you are not missing anything. That's how I tune MAF cars for WOT too. As long as you can get the AFR that you are shooting for (very easy using the PE % Change to AFR table) and as long as you are not pulling any vacuum in the plenum (which happens rarely) then MAF is great. It's that easy.

Tim

OMINOUS_87

Glen
What is BSFC?

87400tpi

Not when someone is giving a bogus theoretical limit of 350 hp to the system.It looks like ski is going to be going high tens with maf.That is alot more than 350 hp.Now this guy's is going tens with 450 cfms of air.255 gr/sec might be 450cfm.But that has nothing to do with maf's calculation of gr/sec.This is the source of this bogus calculation.Just because the ecms displays 255 gr/sec does'nt mean the engine is consuming 450cfms of air,bottom line.

Grim Reaper

Brake Specific Fuel Consumption. It's a factor that indicates the quantity of fuel to make a specific amount of HP. The lower the BSFC, the less fuel an engine needs to make a specific amount of HP.

Generally, an engine produces it's best BSFCs at lower rpms. Thus an inherent advantage of Ski's setup (Superram) is that he has his engine producing it's HP at lower rpms than say a Miniram.

Because of it's difficulty in actually measuring, some people also call it Bull $hit Fudge Constant. But, when all the other factors are looked at (time slips, weight, dyno) then the data is so overwhelming that obviously the engine is very efficient.

Ski built an efficient motor.

RBob

iTrader: (1)

Ski, thanks for the writeup. I'd like to add some to it so that others may understand what may be (is?) happening.

In a nutshell the MAF is staying within the measurement limits as the vehicle is driven around-town. At the strip the vehicle is pushed to the maximum throttle with the fueling being handled N-Alpha.

In the case of your vehicle/engine/usage it works.

On another vehicle this type of tuning may not work properly. If someone were to do the same and use it on a road course the tuning would not work as well. This is due to the air flow area between the maximum possible MAF measurement limit and the maximum air flow at WOT.

As an example: if the maximum MAF airflow measurement limit were 450 CFM, and at a particular RPM the maximum WOT airflow were 750 CFM, how well does the fueling calc work when the engine is flowing 575 CFM (part throttle at that RPM)? If the engine were properly fueled at WOT for that RPM for 12.8:1, I believe that it would be quite rich with less airflow.

If you get a chance you might like to try some heavy part throttle passes and check what happens. It would be interesting to see what happens.

RBob.

Grumpy

Sigh,
the 350 is the top of when the MAF is used to read to 255 gms/sec., and after that your out of resolution. Yes, you can twist the numbers any number of ways. This has been covered in the MAF stickies and in other posts.

72tccracer

Quote:
On another vehicle this type of tuning may not work properly. If someone were to do the same and use it on a road course the tuning would not work as well

I basically do the same thing, just read the WBO2 sensor to get the desired AFR.
The car keeps up quite well with the MAP cars, in fact I did win the Championship last season with it.
www.tccracing.com
#72 Chuck MacTrinder

I have yet to have the car on the dyno or drag strip, but a couple of cars I race against are making 450-475 hp.

Chuck

RBob

iTrader: (1)

>>I basically do the same thing, just read the WBO2 sensor to get the desired AFR.

Would you elaborate? In your particular setup is the engine being used at various part throttle openings? And if so how well is the AFR controlled? Are you using the f-body MAF & ECM? How many HP is your setup making?

RBob.

ski_dwn_it

Rrob,

I understand what you are saying, but I tested my car under heavy loads, as we live in VERY mountainous area of PA. With that the lv8 was way up there and still the BLMs were near or at 128, in non-pe mode. As for road racign this car I think you would have your hands full trying to keep it from spinning out, you would surely need some sticky sticky tires and a whooooole lo of driving experience. This thing anywhere under 55mph in any 3 gears will smoke the tires off. Also remember what I built it for. Although in the right hands I think it would be a serious contender at any road course/autocross.

Although I understand also what 87400 is saying I have to say I don't think its necessary to fiddle with the MAF tables. I didn't and still have good blms, maybe to get 128 everywhere you would have to, but I don't think its necessary. But understand, Iam no saying that his way wouldn't/couldn't work. Just not the way I did it. I adjusted everything in the injector constants and the spark map to get mine where they are at. My thoughts are, if I can do it on this engine, with a .610 lift solid roller cam, anyone should be able to.

I did the same methed with my 219 SR 190 AFR setup with equal results, and also with the stock setup way back when.

Also, Rrob, if you would drive this car you would soon see that even at 1/4-1/2 throttle on the highway if held there for any appreciable amount of time, you are cookin WAY< WAY to fast for the highway. So very seldom do you encounter a high air flow through the MAF system without shakin afterwards, and feeling your adrenaline flowing.

You can search the board and see person after person struggling with their tunes. Yet I am nearly certain that with the MAF system using the technique I described here they would be running better ETs, with a tenth of the effort. not calling anyone out, but if 87_TA was running MAF on that new setup of his, which by all means *should* be, in theory, with a 406 + miniram, running quicker than corky or my setups. I would be right now with him just swtiching back to MAF, and even running my tune in his computer even with the different intakes he would pick up .5 sec, first time out with the car doing nothin else. And with a little tweaking he would have his car dialed right in. This is nothing against 87_TA, for we spoke down at the track the day I ran, and he is a really nice guy, its just an example of a car that is running no where near where it should be and most likely the cause is the complexity of the SD system.


Its kinda like this: If the goal is to add 2+2 and the choices are using a super computer (SD) or a calculator (MAF). Where the Super computer required 15 engineers and 90 algoithims to be developed and processes, any of which could mess up the calculation. And the calculator that works like we all know.

I know what one I am gonna choose if getting to the strip and racing depends on getting the answer.

resolution or not, again it boils down to what I said. if you can tune AFR for what you want, then what more resolution do you need. if part throttle is tuned to 128 blms what more is there to do there?

72tccracer

O.K I know i will probably get slammed here, but this is what i have done so far.
I have taken a chip that was modified by someone else for another road race car, I then adjusted the injector constant until I got the car reading 12.2 at wot. I beleive I got luck on this because with the video camera in the car it stays there sold through all the gears from 50 m.p.h. all the way to 160 m.p.h.
The part throttle is used some in the middle of corners or long sweeping turns and it reads 13.4 afr (if I remember correct).
As far as I dle I used a method that SKI posted some time ago to modify the maf table and it seems to be fine. I have it idling a little high due to .650 lift cam. I know i have alot more tuning to do I have only done about 12 chips, but the car is a road race car only so time testing is very limited.
It is a corvette MAF and ECM.
As far as H.P. I am totally guesiing at 450, like I said others have had their cars dyno betwen 450-475 and I can keep up just fine.

Chuck
www.tccracing.com

TRAXION

Whoa whoa whoa. That is not true at all. The real problem is that his AFRs are not nailed down at WOT via a WB O2 sensor. That's the beauty of what you've done. It's not hard or complex. You just look at the AFR and tweak the PE table. Cakewalk. It's just that people don't have access to or want to build a Wide Band O2 sensor. That's the real problem. Keep one thing in mind here ...

With both speed density and MAF you can tune WOT the same exact way. Put a WB sensor in the exhaust and adjust the PE % change to AFR vs RPM table. You can get the same results on both systems when taking this approach.

Now - the hardcore guys are gonna come out and say "Trax, dude, it's not that simple. With MAF you have to worry about this, and with SD/MAP you have to worry about that." True - but fact is - you can get the same horsepower / torque results at WOT if you just put a WB on each setup and tune the AFR. With MAF you are admitting to no resolution and instead feed in PE fuel. With SD you are admitting that you don't want to fully tune the 100kPa curve and feed in PE fuel.

You've made some awesome points so far. But - don't mess it all up by now saying that SD is the cause for why a specific setup isn't running well and that his car would go faster with MAF. That's just not true. If he spent the same amount of time on his BIN that you spent on yours and IF he used a WB O2 sensor then he would have the same ability to maximize his horsepower. Part throttle is a completely different story. But, with regard to WOT, SD isn't the problem. It's the lack of a WB O2 and the time adjusting the PE tables. You have to give me this one

Tim

ski_dwn_it

Trax,

I think you kinda read into my post more than I antisipated, guess that statement kinda lended itself to that.

The point I was trying to make was not that the end result would be better, with both systems tuned to their max. But I think that he would be running quicker with MAF out of the gate in the preliminary stages of the game. Hope that clears it up. I know you can tune that car to run equally as well as MAF. But with that being said, I think there are many more chips to come to get it that way.

This is based on the fact that when I first started my car I switched back to my 350 tune for giggle and the car ran still unbelievably strong. The AFR was off a tad from now, but was still about 12.2-12.7, for the short period i ran it.

Careful with that statement, I am only two chips into it with those runs

OMINOUS_87

Trax

Speaking of wide band. Are all the parts readily available now? What is the current total cost? Last I read people were having hard time getting this or that. There should be a DIYWB FAQ sticky.

87400tpi

Well traxx we see eye to eye on this one.It boils down to basically two or three tables to get dialed in close at wot with the aid of w/b.
But this is my gripe,I have been told anything over 350 hp would be "hammering" the resolution on a maf car.I have been told it's nearly impossible to go past 12 seconds in 1/4 mile with maf.Corkvette came in telling grumpy he was running 11s debunking that a year ago.There might be some underlying lv8 issues but wot ski has control of a/f ratio.Untill he makes more power and loses the ability to get desired a/f tuned,he is not losing "resolution".My calculations indicate he can go deep into the 10s w/o "losing resolution".That's more than 350hp and 450 cfms.Lets get real 450 cfms can't feed a car going that fast.The maf system is not a 1 bar map sensor.The maf system is not "restricted to aprox 350 hp.The maf system can go beyond 12 seconds,Concede...

85l98

i can attest to skis race weight my car is the other car he talks about mine weighs in at 3400 with me in it and i also have a roll bar which would make up the 50lb difference in cars the only thing out of skis or mine is the spare they are both fully optioned and working corvettes my 85 and his 89 yes we are both running 24lb svo injectors which mine are rich most of the time at 36-40 pressure have to turn it down in the chip and i allready went 124+ mph in the qtr with a non lockup converter there is no secrets on these cars just excellent matched components any non belivers out there can see either car race at tracks on the east coast i myself went to englishtown 3 times salem once keystone twice dragway 42 4 times norwalk once maryland international raceway once mason dixon once just last year alone i will be at beech bend on memorial weekend for the corvette cruise inn 4 and the other numerous tracks throughout the year iam not a bech racer just a racer who races every chance i can get skis car is an exact duplicate of my combo except for converter and header size and its first time down the track proves the combo works

87400tpi

I wonder if tcc would let me join?I have an 87 formula though.I bet I could put a spakin on you vette boys.My formula weighs around 3300lbs.

TRAXION

Ok - here's the key on this one:
Anything over 350hp is hammering the resolution on a MAF car. It's the interpretation of this statement that causes the confusion. I'll try to clear this up right here - right now.

At any point while you are driving the car if the car is producing 350hp then you are probably pegging the 16-bit ECM limit of 255 ... thus, you have no resolution. HOWEVER, the idea here is that you need to be producing 350hp going down the road. That's not going to happen at part throttle for anyone that I know It will happen at WOT. However, at WOT MAF guys don't care about resolution so it doesn't matter It's kind of like the whole - which comes first, the chicken or the egg. Yea - at 350hp you don't have resolution. But, the real point here is who cares. You don't need it. IMHO - with all my vast PROM experience with both MAF and speed density - you only need resolution at part throttle because you can use the PE tables for tuning WOT. Word. Does that make sense? If not - let me know and I'll try to explain it better.

Whoever told you that is smoking crack.

Again - you have to keep in mind what some of these guys mean by resolution. Technically speaking, Resolution means you know exactly how much air is coming into the car. The truth is - with MAF there is no resolution at WOT for high power applications because the ECM limit of 255 is reached. With MAF you are admitting that there is no resolution so you fudge it and add the extra fuel via Power Enrichment. The fact is - as stated above - it doesn't matter. As long as you have resolution at part throttle (which in most cases you do) the everything is great. The fudge factor used in the PE tables works.

IMHO - I think there is just a big miscommunication issue. YOU have to understand what is meant by resolution. OTHERS have to explain what they mean by resolution. Hopefully, I just cleared that up. If anybody here ever said that MAF can't go beyond 12 seconds then they are smoking crack. Who said that?

Tim

TRAXION

Admittedly - I probably did. I just really want to keep things cool. MAF and SD both go fast and, IMHO, to tune WOT on both cars can take the same amout of time. It's the whole part throttle thing where MAF really shines.

This could very well be true. Honestly, I don't know. It really depends on the cam/head combo that is being used. This ultimately determines the real question that needs to be asked in order to answer this question ...

How far beyond the 255 ECM limit is the MAF system flowing at WOT as compared to the error in the 100kPa region of the VE table. I think that we could make some general statements about this given certain head/cam combos.

Totally. Ultimately, IMHO, I think that part throttle is harder to tune on SD cars - but both cars are equally easy to tune WOT.

Doesn't take much when you have a WB. That is the ultimate key that not many here see.

Tim

TRAXION

AFAIK - everything has been available for a long time now. The only exception to this is that the actual NTK sensor is on national backorder A LOT ... probably because of the whole DIY-WB.

http://www.diy-wb.org

Tim

RBob

iTrader: (1)

ski_dwn_it, 72tccracer (Chuck), I appreciate the input. Between your input and some thinking it would seem that after the maximum MAF measurement limit has been reached that the fueling isn't so far off as to cause problems.

Sure, it may be a little rich when the engine airflow is greater then the MAF limit and less then max WOT airflow, but, the fueling isn't so rich that it causes a problem.

I think (danger here!) that this may also be because of your engines ~450 HP output. If the MAF maximum measuring limit is ~350 HP, how much is the fueling requirement going to be changing? Unlike an engine making 600 HP.

I also think (again!) that just looking at the maximum HP an engine is making is a mistake. The engine will be making less HP for a good portion of it's range. And it is repeatable.

(I would need to put a graph together to better explain my thoughts). However, in words, hypothetically, at 4000 RPM, WOT the MAF measurement limit is reached. So at any RPM and throttle position below 4000 RPM and the MAF reports the correct airflow.

At 4500 RPM WOT the increase in airflow is covered by the PE fueling. If the throttle is lifted a little, the change in the resultant AFR is very small as either the airflow change is small, or so large (lift even more) that it is back within the limits of the MAF (and non-PE).

And so on up to max RPM. At that point it's pretty much WOT or the engine won't be at that RPM.

Interesting. . .

RBob.

ski_dwn_it

Very well put Tim in your posts.

The 350HP limit/Loss of resolution is ONLY a concern when in closed loop situations when the computer is controlling the fuel trim etc via the O2 sensors. As Tim said and the reason I keep saying I could care less about it is the fact that very few cars ever experience 255+ g/sec under cruise conditions. If I for one was in my car and under cruise conditions it would be pulling 255+ g/sec, I would be clawing at the door to get the heck out because I'm sure you would be going 150MPH+. Any idiot that is doing that on a regular basis on the street should not be worrying about his ECMs calibration, but rather his heads calibration.

Now at the track I'm sure my MAF is reading 255+ g/sec out of the gate and all the way through. But like I said earlier. i am only concerned with one thing. That is AFR. I adjust the fuel in the PE vs RPM to achieve the desired AFR.

The key to being able to tune the MAF system under cruise conditions is the fact that you are still under 255 g/sec. But I will say it again, and Trax did also. You will not likely find a car that is on the street that is able to do that. So the 255 g/sec is fine.

If in a rare case you would find one that did, then you can just adjust the PE to kick in and adjust the Fuel trim via the Pe Curves.

If anyone is not clear on this speak up. Its really quite simple. If anything is confusing and it had me for the longest time, it was that people did not see this and kept saying you couldn't tune MAF effectively/efficiently.

You see I knew if I pushed hard enough, some people would start to understand.

ski_dwn_it

Rrob you grasped it! The clouds are staring to part for a few! :lala:

Keep reading it guys, you will get it too.

TRAXION

Word. My biggest miscalculation (oh my gosh - is he saying he's wrong?) was that I 'thought' a bigger cubic inch engine would peg the MAF during closed loop in situations where big hills were involved. Truth is - that just doesn't happen because you don't need 350+ hp to proceed up a hill. With that said - open loop and WOT have been an absolute no-brainer for years.

Tim

87400tpi

Here is he point,folks.The original statement is 350 hp,anything more your hard on the calibration.You have it right again,traxx.I have never seen a maf car read 255gr/sec @ part throttle every day driving,ever.That is where someone can run "out of resoution".But it is flat wrong to say anything over 350hp is going to be tough on the motor using maf.I will not say who said 12s is pushing it for maf.But I can say someone that thinks maf can't handle much more than 350 hp,might be inclined to think that.I think someone needs to be a big man and concede here.Anything over 350 hp is not pushing the maf code to the limit.That is flat out falses.Read the original thread the 350hp theory came from.This is bogus info and is misleading ,period.

87400tpi

My 406 runs at a lower throttle% than a stock 350 under all driving conditions.It has so much tq I can drive all day long and not go past 10% throttle opening.So The truth is the opposite ,for me.My car gained "resolution" in a sense,booya.

ski_dwn_it

Now that we have the MAF resolution put to bed I think. Lets look at the injectors again that came up.

I am sorta think out loud so be gentle with your bashing of my thoughts

The facts are I am running #24 SVO injectors @ ~45 psi that are supplying enough fuel to maintain a AFR of 12.8 through my runs, this in on a 450+RWHP car most likely. Corky is doing the same thing at 36psi (talked to him last night to verify).

Now isn't the PW whatever you tell it to be when you change the PE AFR vs RPM? This is also dependant upon the correct injector pulse width etc. Therefore if my part throttle tune is not on, and my injector constant is way out to lunch, then my pulse widths for WOT are not gonna be accurately reported. For instance, if I had my injector constant set to 22, instead of 24, wouldn't the duty cycle be reported incorrect if the injector are truely 24. Also pressures would have another huge impact on properly reported values.

I have never really thought about this in great detail, mainly do to the fact I never really had a problem getting the AFR I needed.

The main point I am trying to make is that the pulse width is whatever you tell it to be in a round about way with the injector constants etc. In closed loop, yes the injector pulse width is governed by O2 reading and corrections based on them. But I think we already cleared up, that like the 255+ g/sec situation, I highly doubt under cruise conditions I have a 100% duty cycle.

Furthermore even if I scanned my runs and reported a duty cycle, I doubt the numbers would be accurate to represent what is really going on.

I'm not sure if I was real clear on this. Nor did I spend a lot of time hashing through it in my mind. Just wanted to throw it out there for you all to digest and come back with comments.