NefMoto

what is the flow limitation of an RS4 MAF?

ive heard figures around 700hp? can this be increased by underscaling?
 
are there other good MAFs to use for this kind of power? aftermarket ones with calibration data to intepolate for the MLHFM?

any ideas are welcome.

I'm thinking only aftermarket and then calibration.... But for that youd have to basically test and log what voltage output maf sensor gives at what airflow...

Pro-M.

RS4 MAF maxes between 500 and 600 hp on pump.

"testing" 900whp+ worth of air into a 4-cylinder engine running on alcohol = explosion and total failure, this data needs to be 110% accurate from the start, and so that is not an option.

i dont know of any flowbench available to handle this kind of airflow.. not in the near vicinity.. so a calibration with the sensor out of the car will be most troublesome.


ah, Pro-M looks like the way to go.. them have 9 or even 30 point calibration data sheets available.. thanks prj!

The output voltage of my RS4 MAF on dyno is exactly 4.95V at 7.400rpm with 1.75Bar holdboost and 639PS.

4,99V = 1996 Kg/h airflow is the absolute limit of the RS4 MAF.

The inner diameter of a original RS4 MAF is 81mm (5153mm²)
If you increase the inner diameter to 90mm (6362mm²) the MAF can measure until a airflow of 2464 Kg/h.

(http://www7.pic-upload.de/22.06.12/gn7jaxozkf7.jpg) (http://www.pic-upload.de/view-14785023/MAF.jpg.html)

(http://www10.pic-upload.de/22.06.12/uaux4f6mwnkb.jpg) (http://www.pic-upload.de/view-14785063/20120619_175501.jpg.html)

(http://www7.pic-upload.de/22.06.12/6kvhdiszdwwo.jpg) (http://www.pic-upload.de/view-14785117/20120619_175142.jpg.html)

Good info  ;D

RS4boost, using your example, you increased the diameter of the MAF by 23.4% and therefore increased the metered flow of the 4.9902v value by 23.4%.  I assume you scale all the remaining values by the same constant?  I've never had to scale a MAF before, so I was just confirming that this is how it's done. 

this is nowhere near enough flow nor accuracy for this tune.. which will be 900whp+.. but thanks for the info! =)

That`s right.

To use a 90mm MAF was only an example to show you how to calculate the max airflow and the right values for MLHFM.

Of course you can also build a sensor with its own mass.

The only thing to keep in mind is that you need to mount a grid in front of the MAF sensor to stabilize the airflow.
If you don`t do this, the air pulsates with high turbulences and the sensor will give you bad values.

(http://www10.pic-upload.de/23.06.12/1vdu932x276y.jpg) (http://www.pic-upload.de/view-14791140/20120619_175209.jpg.html)

me7 takes the LMM table minus 200kg/h for real air mass. so it maxes out at 1800kg/h which is good for up to 650 HP

I don't like how you guys throw HP numbers around.

They are meaningless, because fuel is different...

I've maxed out RS4 MAF's at 570hp on pump fuel, and I've done over 650 on E85 and race fuel without it maxing.
Saying a maf is good for "xx hp" is completely wrong, because fuel octane rating makes a huge difference.

I disagree again with you.
air mass is a very good indicator for estimating max power and at least to find out the right HFM for your tune.
even with different fuels.

well, the question was formulated as in topic, what to use for a given power.. ofc these engines are made to run on pump gas, so no e85 fueling needs to be discoussed here.
(sure, you can raise the VE even more with race fuel, vp, e85, methanol etc etc..)


and im pretty confident the RS4 MAF will be too small for this.. and will not need to be able to calculate this flow accurately.. unless MANY hours is spent calibrating one and fabricating new tracts, air straighteners etc.


this engine will be running on pump gas, 98.4 oct, with a boost of ~43.5psi, and the VE will be very high.. so ive decided to find me one of those Pro-M 92:s.. with a 30 point transfersheet made and calibrated in flowbench.. which should be perfect for this build.

So according to you, ignition timing makes no difference right?
Do you realize there can easily be a 150hp difference at high power outputs due to ignition timing?

Have you ever mapped a car on E85? :)

Air mass only shows how much air is going to the engine, it does not show what you are doing with it or how efficiently you are using it.
It's a good estimate on two equal engines with equal fuel type. It's completely useless for comparing engines with different compression ratio and fuel type.

Unless this engine has lots and lots of displacement, I think you are being overly optimistic with your power figures.

e85 or race fuel makes no big difference in the need of air!
you only need a lot of more e85 ;)

if you don't change lambda and ignition too much, you can perfectly estimate power with air mass flow.

snook:
for 900 whp you roughly need 700 g/s air, that's more than 2500kg/h.
I doubt there are so many HFM in that range or increasing housing so much, so best precise way would be 2 RS4 HFMs in two 81mm Stock housings.

youre correct in this, i made a pretty grave misscalculation there in my rough estimate, lol! =D


..and well.. using e85 you will reach the same power with less air due to advanced timing, which, up till a certain point where the torque starts to drop off, correlates to higher VE, sure this is correct.




This engine does not have lots and lots of displacement, this is no old low-efficiency V8, so why would it..
it does have a ton of efficiency and a concept compund setup tho.. which should be able to fully spool 43.5psi by ~2500rpms.. without surging.. using a turbo capable of 900whp figures in one of the stages.
implementing a very special cylinderhead, 5-valve tech, custom camshafts designed for VVT, etc etc.


and yeah, i might sound optimistic.. but still if it should ONLY put down ~800whp now, id rather not boost into the limit of the MAF or something similar, running lean att full power.. just staying one step ahead here.


the Pro-M 92 should be able to support ~1500 flywheel hp, with much higher precision, and a 30 point transfersheet to interpolate into the 512 point HFM table.. so it should be well suitable?

How many kg/h should be for 300hp? that can be calculated entirely correct?

So if you are not talking about a V8. Are you talking about 2.7? Or things based on that?
Could you say what compression ratio you will be using and which engine as base?

That's exactly my point. The air remains the same. Spark timing is advanced 10 degrees or more at high boost.
What happens?
Why on earth would you run E85 or race fuel if you are not going to take advantage of the fact that you can run much better timing?

So once again. With the same amount of air, you can make 500hp or you can make 650hp.
The MAF is going to max out exactly at the same spot - meaning all these so called "hp ratings" are pointless.

Maybe we can assume the ign timing will be very close to MBT, which it should be anyway if tuned correctly. Using that scenario, we can again express hp vs. mass flow..There IS going to be a range, and I think that's all the OP was asking for?

Unless you are running very high octane fuel, timing on boost is never anywhere close to MBT, it's always knock limited.
How close to MBT you are is governed by the fuel's resistance to detonation (octane rating), the engine's compression ratio, and a plethora of other factors.

On high output engines, which are very knock limited on pump fuel, the difference between running straight pump, high octane race fuel or E85 is very pronounced. The more knock limited you are, the bigger gains you get. The difference can be easily 25% and more output in power for the same air flow.
So yes, there will be a range, but the range is about 500 to 700 crank hp on a RS4 MAF.

Yeah, it will be too small for the application of the OP, but my point still is, that you can not predict when the MAF runs out based on a hp number.

prj: im going to say that you are correct, but as a rough estimate for pump gas this works, i just wanted to know what the upper limit was.. so saying <600 on pump gas and ~700 on E85 would suffice.

im 110% with you that we should be speaking FLOW here and not hp or pressures, flow is the only thing relevant.



1.8l base engine. static compression ratio 8.8:1, if that is what youre asking.
(but there is more to it.. this engine will be unique in many ways.
for one; it will be a fully built race-engine.. and not just a tuned stock engine, with its own valve-timings and measures to keep the dynamic compression and cylinder pressures under control)

in n/a form it should be good for about ~185+hp.. which at best would produce somewhere around 700hp at the flywheel at said boost.. based on previous tunes and testing.
but since this one is specifically built for boosting at high levels.. tis where it will shine.. and so, yes.. im very optimistic in my calculations  ;)

Thanks for all your input people, ill post pictures of the blown engine later on..  ;D
 

10 degrees is not 150 HP like in your example.
e85 can help to heal extreme retards at very high boosts.
but you can still estimate max power from air mass flow, even if it is a narrow range.

how would you aim to size turbo/compressor wheel and HFM? rule of thumb +10%. period. :)

Have you ever tuned engines over 600 hp? Yeah, 10 degrees can easily be 100+ hp.
Really, from what you are writing it seems you have not seen the same car on different fuel types, have not tuned them on dyno, and have not seen the differences it makes.

I'll leave it at that.

Let me be a bit more precise now that I have some time:

>>Unless you are running very high octane fuel, timing on boost is never anywhere close to MBT, it's always knock limited.

If not given any special information I speak for normal premium gas (pump) which is around 100 octane in europe.
But since Mr. Ottos invention is converting energy from fuel into rotation it depends a lot how far you are away from MBT.
And both, MBT (lambda1) and f_eta(delta ZW) is in every ME7 application.

>>How close to MBT you are is governed by the fuel's resistance to detonation (octane rating), the engine's compression ratio…

Correct and I guess nothing new to anyone here in the forum. 

>>On high output engines, which are very knock limited on pump fuel, the difference between running straight pump, high octane race fuel or E85 is very pronounced. The more >>limited you are, the bigger gains you get. The difference can be easily 25% and more output in power for the same air flow.

This is what I wrote before, yes. Now that we know that knoob wants to gain 900 HP from a 1,8T engine, my argumentation ist a bit weaker but still valid.

>>So yes, there will be a range, but the range is about 500 to 700 crank hp on a RS4 MAF.

But then you can still say that RS4 MAF is always enough for 500 hp. And that was the initial question (900).

>>Have you ever tuned engines over 600 hp? Yeah, 10 degrees can easily be 100+ hp.

Yes, but not with 1.8 liter ;)

But I am willing to show you that 10 degrees is not that big deal in every “normal” situation:

Peak power is somewhere around 6000 and 7000 degrees. Let’s take the middle.
Considering KFZW as a good source close to MBT, it suggests ignition is optimal at RS4 e.g. states 30 degrees.
Many slightly tuned cars run that engine at 23-25 degrees at 6500 rpm from what I saw. This is a perfect deltaZW of 5-7 which is only losing 0,5% efficiency.
Now you add a lot of boost and power and running ignition at a safe 10 degrees less (13-15) due to knock, according to ETADZW you now lose 7,5% due to ignition efficiency.
Assuming 650 HP at 1,6 bar this is roughly 50 HP only.

Yes, you can describe it like that. But your statement of precisely estimating horsepower figures from airflow falls flat on it's face in this case.
And I can see that from your statements. 90% of the tuning I do is for applications where the engines make more than 200hp per liter.
This is true for naturally aspirated cars. Not for turbocharged cars.
At 200hp per liter, VAG turbocharged engines tend to make peak power at about 5500-6000 rpm with correct tuning. As you go higher and use more radical setups in the head, you start to move this along. Only at 300hp per liter does it start to get close to 7000 rpm.
This is where you go completely wrong.
On pump fuel a B5 RS4 can only run about 10-12 degrees timing at 6000 rpm with 19 psi boost on K04's.
And that only makes 450hp. so about 170 hp per liter. And a 300hp/liter engine is everything else than "slightly tuned".

It depends a lot on combustion chamber design, but even at a CR of 8.0:1, engines that are above 250hp/liter rarely can run more than 9-10 degrees timing at that RPM on pump fuel.

You can make calculations, and try to say that it will not be 100+ hp difference all you want.
I have experience with 200+hp/liter engines on the dyno with different fuel types, and I have real world hard numbers, how much they gain from switching from gasoline to E85, or from adding heavy water/methanol injection.

But since your ignition timing assumption is 2x wrong, your calculation stacks up pretty well. 100hp is just about the ballpark for 10 degrees of timing on a 280hp/liter engine.

I recon you mean KFZWOP not KFZW.
Don't make the mistake to try to calculate something out of the ECU maps on operation points that are far away from stock calibration. ETADZW is one big compromise that is suited to the relevant regions for the torque structure because ignition efficiency is highly dependant on the load point.
Even KFZWOP (contains AI50) is only "accurate" for stock operating points and a bit higher. All other values are extrapolated.

 

Yes and no,

The fuel makes a big difference in the context of HP and Airmass. Not The Octane.

Chamically Ethanol is a stuckture from C-H-O, ordinary fuel only exists of C-H structure.

That means, that every bit of Ethanol brings Oxigen into the engine without beeing measured by airmass...

This is one of the points that make it necessary to put more ethanol into it to get the aimed afr.

So all in all you can make more HP with ethanol without adding more oxygen (by air) through the afm, because the oxigen is in the gas.

yes right, I meant KFZWOP2

for the rest I am still convinced that it is ok to take these numbers to do some estimations. I do not talk a about 1% precision.
But if you try to size compressor wheel and MAF, these estimation should be very suitable.
IMO KFZWOP is independent from big turbo mods and still true if you don't mod displayment or compression ratio. of course you run more and more into knock limitation. the first 10-15 degrees away from ZWOP are much less restricting than any further, this is true. So if snoob is aiming >400 hp/l that's beyond my experience, but I guess the estimation with ETADZW is still true, as far ZWOP is not already knock limited (which it probably can be regarding FR).

On pump fuel a B5 RS4 can only run about 10-12 degrees timing at 6000 rpm with 19 psi boost on K04's.
And that only makes 450hp. so about 170 hp per liter

I saw other logging data here in the forum IIRC. Can someone confirm?!

What's there to confirm? This is general knowledge. 23 degrees at 6000 rpm is naturally aspirated engine or VERY low boost engine timing in context of pump fuel.
Anyone who tunes cars on a regular basis can tell you this.

The log data you saw was probably from a car using heavy water/methanol injection.

And water/meth injection if running a lot gives hp gains between 15-20%...

i have to say i like this discussion..  ;D

well.. ill add this.. try to think outside the box for once..  ::)

im going to state that you can build an engine which is allmost impossible to make detonate, due to homogenization of the air/fuel mixture.. which would run a timing close to TDC and still get ~170% more then a conventional engines power converted from fuel to mechanical energy within the first 14 degrees of crankshaft movement(which is vital.. to those who dont know this.. after 14 degrees allmost everything is wasted in heat and not converted into mechanical energy)
also, this can be done in a very lean environment, close to 22:1 to one, on normal pump gas.

so, beeing hang up on older techs and "facts" doesnt really get you anywhere.. fresch thinking does.. i dare you to build your own concepts.. and yeah, i will be aiming for 400hp+/litre with this thing.. its not like thats something new around here.

//Sn00b

What displacement/engine is this going into?

I talked about 6500rpm all the time.
exactly 12 hours ago I had a car on the dyno, rpm 6500: Lambda >0.85 and Ingition >20 and boost at 2300mbar, pump fuel.
now what?

2300mbar absolute pressure or boost pressure? What compression ratio?
If it's absolute pressure and 1.3 bar boost - then you are probably below 200hp/liter... We are talking about 300hp/liter engines here.
We are also talking about port injected engines. With direct injection things are different.

Also, I don't know what engine you are talking about. I just stated what timing my RS4 does, and what timing 600hp engines that I tune do before knock comes in.
The 250+ hp/liter engines all run over 2 bar peak boost.

1,3 bar boost, compression ratio 9:1, slightly below 180PS/liter, classic port fuel injection.

very similar to the RS4.


what is your RS4 doing at 6500?

to come to an end:
let's state that HFM Sizing depends a lot on Mean effective pressure and that below 200 HP/Liter there are very good rule of thumbs as I said and extreme tunings above 2+ bar boost can vary a lot with ignition optimizing and fuel.

But for both cases you can estimate a HFM size that will always be enough for xy HP or even more.

seeing as the op has'nt confirmed what displacement he's referring to.. and I guess its  4cyl...
I have run 33degrees advance previously.. pump fuel, with 50/50 wmi, 1900cc 20v, 35psi boost, 9000rpm
zero det.. pump fuel shell vpower

however...

It lifted the head.. lol..
cylinder pressures is all I will say

a few posts back i wrote 1.8l base engine, and ofc a 4cyl 20v.. static compression 8.8:1.. and yeah.. VVT and custom control for dynamic compression, etc.

if your engine lifted the head id call that no more then a contruction and tuning mistake.. and yeah, extreme cylinder pressures is what im after.. but at the right time.. ~8-14degrees on the crank, after tdc.

timing is NOT one of those things where MORE is better, and id imagine that is why its called timing..
running too much advance and reaching peak expansion/pressure before the piston reaches TDC wouldnt be benificial to anyone.. and as the piston closes in on TDC it would most certainly be able to lift the head/blow the gasket.. normally it would detonate way before that.. but water/meth can supress detonation extremely well.

ive ran 38psi boost in an 1.8l 4cyl 8v engine, at 8:1 static compression and pump fuel, v-power, with good timing.. and id imagine this engine with way better combustion chambers, 5-valve tech, VVT, custom highpressure fuelsystem etc would coop real well at these pressures, should be no problems at all.

Yeah, exactly. 180 PS/Liter...
Add 100 PS/liter, and you will see what I am talking about.
Also, if you use big hotsides, with slow spoolup, you can also run more timing - but it makes the dynamics of the car bad.

As for my timing, have a look...

One thing is funny, that people say "pump fuel" when they are running meth injection.
Meth injection is NOT pump fuel, it's like running race fuel all the time. When one says pump fuel, it means straight pump. No water/meth injection of any kind whatsoever.

As for MAF sizing, I know for a fact, that my RS4, which probably makes around 440 PS right now, would make 500PS with meth injection.
And if you notice, this thread was from the start talking about 300hp+ liter engines, that's why I said that it is nigh impossible to size the MAF without knowing more details about the engine or match it up to horsepower. The only thing you can say is a conservative estimate for how much horsepower it will 100% be enough in these cases and estimating horsepower from mass flow won't work.

Hmmm.
you will have to consider cylinder pressures, as your power goals (unrealistic imho) from the spec tou elude to, are not going to be fulfilled..
Det threshold was no indication of the pressures being produced, and despite tensile head studs being in place the engine whilst fine when being tuned on the dyno, over many runs, it did let go when on track on its higher boost.
You will have fun getting to your goals.  I suspect you wont get close however.

and as for trying to use a MAF on this project, and scale a maf, whilst the rest of the me7 will be blind to boost levels etc..... you are asking a lot.


good luck ;)

regarding MAF, yeah, me7 uses this as primary source for measuring airflow, which is 110% vital, and then MAP for diagnostics and reference.
so it doesnt matter if the map cannot register over 2550mbar.
ofc i know that i will have to run open loop based on flow and n75 dutycycle after 1.5bar boost, that isnt asking alot, that is childsplay, and yeah, i sure will be using MAF.. removing this vital part would make the me7 truly blind.

i suspect you dont have a clue as to what the specs are of this engine, and id imagine from your replies that you wouldnt understand half of whats going into it, as you havent ever ran a compound setup and definitely not designed your own system, with variable valvetiming, custom grind camshafts and a custom designed fueling system for extreme atomization etc.. or have you?  :)

not trying to be rude, just trying to state that this is NOT a tuned oem engine where you would hook up a big turbo and boost the crap out of things till its blown to pieces.


high cylinder pressures at the right timing in the otto-cycle = power.

running these boostlevels you would look to o-ring+copper gasket or even labyrinth seal the head to the block.

an interesting fact is that bmw once used a compound setup in an old f1 engine.. which produced 1400hp in an 1.5litre engine at 3.9bar boost.



thanks  ;D

Good luck from me too looking fw to read news on this topic  ;)

as for specs..  not a clue.. as you have'nt mentioned them.. and I am not a mind reader ;)

I am well aware what old F1 turbo motors did..

...and as for what I know and do, and have done, you are equally as ignorent..

hope your project goes well.  maybe you will share the results if they happen.

no offense man but you are trolling your own thread with parts of this response.
however you definitely get credit for how awesome a read this thread has been.

fresh thinking is what's up, hells yeah.