lulu2003
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« Reply #15 on: June 24, 2012, 11:53:06 AM »
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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. |
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sn00k
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« Reply #16 on: June 24, 2012, 01:15:58 PM »
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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. Unless this engine has lots and lots of displacement, I think you are being overly optimistic with your power figures. 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? |
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« Last Edit: June 24, 2012, 01:22:51 PM by sn00k »
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@lq!
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« Reply #17 on: June 24, 2012, 01:49:44 PM »
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How many kg/h should be for 300hp? that can be calculated entirely correct?
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prj
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« Reply #18 on: June 24, 2012, 03:21:56 PM »
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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. 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? e85 or race fuel makes no big difference in the need of air! you only need a lot of more e85 That's exactly my point. The air remains the same. Spark timing is advanced 10 degrees or more at high boost. What happens? if you don't change lambda and ignition too much, you can perfectly estimate power with air mass flow. 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. |
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vwaudiguy
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« Reply #19 on: June 24, 2012, 03:31:58 PM »
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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?
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"If you have a chinese turbo, that you are worried is going to blow up when you floor it, then LOL."
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prj
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« Reply #20 on: June 24, 2012, 03:39:42 PM »
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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. |
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sn00k
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« Reply #21 on: June 24, 2012, 03:48:59 PM »
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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. Could you say what compression ratio you will be using and which engine as base? 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..  |
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« Last Edit: June 24, 2012, 04:01:11 PM by sn00k »
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lulu2003
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« Reply #22 on: June 24, 2012, 04:39:00 PM »
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Spark timing is advanced 10 degrees or more at high boost.
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.  |
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prj
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« Reply #23 on: June 25, 2012, 12:28:55 AM »
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10 degrees is not 150 HP like in your example. 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. |
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lulu2003
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« Reply #24 on: June 26, 2012, 08:28:53 AM »
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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. |
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prj
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« Reply #25 on: June 26, 2012, 08:47:39 AM »
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>>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). 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. >>Have you ever tuned engines over 600 hp? Yeah, 10 degrees can easily be 100+ hp. Yes, but not with 1.8 liter 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. Peak power is somewhere around 6000 and 7000 degrees. Let’s take the middle. 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. Many slightly tuned cars run that engine at 23-25 degrees at 6500 rpm from what I saw. 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. |
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« Last Edit: June 26, 2012, 08:52:31 AM by prj »
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silentbob
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« Reply #26 on: June 27, 2012, 01:06:46 AM »
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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. 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. |
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AndiS4
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« Reply #27 on: June 27, 2012, 01:45:50 AM »
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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.
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. |
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lulu2003
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« Reply #28 on: June 27, 2012, 03:34:51 AM »
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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 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 literI saw other logging data here in the forum IIRC. Can someone confirm?! |
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prj
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« Reply #29 on: June 27, 2012, 03:57:33 AM »
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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%... |
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« Last Edit: June 27, 2012, 03:59:25 AM by prj »
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