E30 Cobb Maps - Eflex (e70) & e85

[adrian@vishnu]

Originally Posted by Drawn05

Yeah, I am not too sure though now. Apparently the timing corrections I was concerned about are quite normal. They occurred whilst cruising at 2500-3000rpm which isnt important - only when going WOT.

My last 2 logs of 3rd-4th pulls had little to no corrections at all so maybe it just took a little bit of time to adjust. Power feels great. I got 2 more 20 litre jerry cans so I can fill them when I go to Sydney next.

But yeah, getting the latest hpfp installed can only be a good thing.

Yep... you can ignore any timing correction at cruise. I would ignore anything below 5psi boost.

[DR-JEKL]

Originally Posted by adrian@vishnu

The thing is that you can't accurately measure torque on a chassis dyno. Dyno measure the torque at the wheels. This changes with the gear used (lower gears read much higher), so there really is no point in comparing torque figures on a dyno unless both cars run identical gearing and even then you can't compare that result to the flywheel torque figures quoted in car specs. I think my car would be around 600Nm flywheel, and I am quietly confident that my car would have no probs out punching Michael South's car. I challenged him some time ago to a race at the drags. He did not accept.

Ahh huh, so 600nm+ from a tune and exhaust in a sti is pretty much BS/guesstimate?

Thanks again for yours words of wisdom!!!

[335i-boy]

Wow. The 1er section is leaving the e90 side dead when it comes to modding discussion these days. Good to see.

Adrian speaks the truth regarding Caltex Eflex E85. My car dynoed 280rwkw until it started running out of fuel with a fuel mix of 50:50 Caltex E85 and Caltex 98oct in Dec 2012. Max boost @ 15psi. Car is more or less FBO (DCI, AR Catless DPs, Helix FMIC). I don't currently have a backend flash, Procede or other wise.

I am actually glad to hear that Caltex's Eflex E85 is more like E70. Theoretically this gives me some headroom when it comes to fuelling. A safety margin so to speak. If Caltex E85 has less ethanol than United's E85 or the E85 you purchase in drums from the refinery, I won't need as much to reach a certain power level when tuned with Caltex E85. Granted though it won't make as much max power as is possible on a true E85 mix. I have heard lots of good things about in tank pumps to help feed the HPFP. Its not something I will be looking at.

Does United have a non-ethanol based 98oct?

My car is a DD. Having to measure specific Ethanol content because the car is specifically tuned for it is not an option for me.. mainly because I couldn't be frigged. I run the car down to about an 1/8th of a tank, I pull up to a Caltex, fill with 25L of Eflex, 25L of 98oct at the same pump. Done.

Here is a dyno graph of the 280rwkw run. Spero at Autotech has flashing capability to manipulate the DME's fuel table like the Procede and BMS flash. When life gets out of the way and I get a chance to see him, hopefully we should get another 10-15rwkw with just a backend flash and no auxiliary in tank pump.

[Drawn05]

Originally Posted by 335i-boy

Wow. The 1er section is leaving the e90 side dead when it comes to modding discussion these days. Good to see.

I am actually glad to hear that Caltex's Eflex E85 is more like E70.

1addicts Australia has always been way ahead of its e90 counterpart.

As far as the caltex=e70 thing, I must admit that I have no proof that it is consistently 70% ethanol and not 85%. It is just widely rumoured to be the case.

I have ordered some of those glass bottle testers to conduct some of my own trials to see what the 2 local caltex eflex bowsers serve up.

[flinchy]

Originally Posted by adrian@vishnu

The thing is that you can't accurately measure torque on a chassis dyno. Dyno measure the torque at the wheels. This changes with the gear used (lower gears read much higher), so there really is no point in comparing torque figures on a dyno unless both cars run identical gearing and even then you can't compare that result to the flywheel torque figures quoted in car specs. I think my car would be around 600Nm flywheel, and I am quietly confident that my car would have no probs out punching Michael South's car. I challenged him some time ago to a race at the drags. He did not accept.

yeah, since power is just a product of torque, all the torque figure should be (when the dyno isn't screwing up) is power without the formula conversion - so technically it's torque minus your diff multiplication, but it reads out as measured at the wheels... which makes no sense in writing haha
- http://liveimages.carsales.com.au/ca...Pad&width=1050 this dyno for example is pretty well impossible >_>.. that torque figure is totally pulled out of thin air hah

considering dyno's work out gearing with speed/rpm, properly setup it shouldn't be anything like HUNDREDS of horsepower different as alternate gearing would actually be no?

[adrian@vishnu]

Originally Posted by flinchy

yeah, since power is just a product of torque, all the torque figure should be (when the dyno isn't screwing up) is power without the formula conversion - so technically it's torque minus your diff multiplication, but it reads out as measured at the wheels... which makes no sense in writing haha
- http://liveimages.carsales.com.au/ca...Pad&width=1050 this dyno for example is pretty well impossible >_>.. that torque figure is totally pulled out of thin air hah

considering dyno's work out gearing with speed/rpm, properly setup it shouldn't be anything like HUNDREDS of horsepower different as alternate gearing would actually be no?

90% of the time the Dyno does not know the RPM with most operators. They either need to connect an RPM probe which can be fiddly and has differing results for different cars, or they can enter the diff ratio (and most do not know how to do that).

What you say is true about the calculation between Torque and RPM. But the fact is that most dynos do not even try to read engine torque. The Torque graph they display is that at the wheels. You can see this as you do a dyno in 3rd and it will have like 20% more torque than the same car dynoed in 4th. Now some dynos can be set to do an estimated flywheel torque. To do this, they estimate the drivetrain losses to convert wheel power to flywheel power. Then they need an accurate RPM reading to be setup by the operator (normally not done), and then they do the calculation of torque from power and RPM. It is probably not a bad method and would yield good results, but as stated, the torque graphs you see most of the time do not use this method, and if they did, they would need a good dyno operator to setup the dyno correctly to get a semi-accurate result.

So really, most dyno graph torque figures are useless for the actual numbers, although the shape of the curve can be quite telling on how the car would drive.

Also... it is still power that is what makes the most difference in any type of drag race. Power in the RPM where you use it. There is no point having a massive torque figure at 4000RPM in a race where you do not go below 5000RPM. Torque at low to medium RPM will give a good feel to drive but will not be of any benefit in most forms of motorsports (assuming you know how to change gears!!)

[drjekl]

Originally Posted by Drawn05

1addicts Australia has always been way ahead of its e90 counterpart.

pfft!! When was the last time babybrother 1addicts discussed something as technical as this:

http://www.e90post.com/forums/showthread.php?t=834212

[flinchy]

Ahhhhh so when you see a dyno with 3x the torque it should have it's because it doesn't have an rpm probe attached or anything to tell it it's not 1:1?) So it's reading the multiplied torque from the diff?

That makes so much sense! Thanks (seriously thanks haha) i have no idea why i didn't think of that!

Considering you can work out how it will feel given a power curve, gear ratios and final drive, it's not a big loss, and in many cases just misleading then - though it could also mean the power figures are inaccurate? Mm

[drjekl]

Originally Posted by 335i-boy

My car is a DD. Having to measure specific Ethanol content because the car is specifically tuned for it is not an option for me.. mainly because I couldn't be frigged. I run the car down to about an 1/8th of a tank, I pull up to a Caltex, fill with 25L of Eflex, 25L of 98oct at the same pump. Done.

Here is a dyno graph of the 280rwkw run. Spero at Autotech has flashing capability to manipulate the DME's fuel table like the Procede and BMS flash. When life gets out of the way and I get a chance to see him, hopefully we should get another 10-15rwkw with just a backend flash and no auxiliary in tank pump.

That sounds like an ideal scenario to me also, but I thought the pump stopped so to speak once you placed the fuel nozzle back in the cradle at the servo?

Nice dyno curve also

[adrian@vishnu]

Originally Posted by flinchy

Ahhhhh so when you see a dyno with 3x the torque it should have it's because it doesn't have an rpm probe attached or anything to tell it it's not 1:1?) So it's reading the multiplied torque from the diff?

That makes so much sense! Thanks (seriously thanks haha) i have no idea why i didn't think of that!

Considering you can work out how it will feel given a power curve, gear ratios and final drive, it's not a big loss, and in many cases just misleading then - though it could also mean the power figures are inaccurate? Mm

Yep... dyno curves with torque are not that useful for much other than the shape. You certainly can't use them to compare to factory specs for other cars like people tend to like to do on forums. They can be useful if dynos used are of the same type, and the cars are of the same type, and the gear ratios are the same. Often people compare torque figures of N54s, and it is probably OK to do this as it is mostly the same dyno type and same car type in the same gear selected. I don't see the point myself, as torque does not mean that much in the real world. It is pretty easy to get ridiculous torque numbers by just pumping up the boost at as lower RPM as you can get it. Stock turbo cars can produce insane torque numbers, but are not actually that quick compared to modified cars with less torque.

Mostly the diff ratio data in the dyno is set from whatever car it was last set properly in, so it is probably not 1:1. It may be the ratio for a small 4 cylinder. Also it is not actually the diff ratio. It is the combined ratio of diff, gear, wheel/tyre size. It is pretty easy to work out on the dyno. You just go to 100kph reading on the dyno, and read the RPM off the tacho of the car and do a quick maths calc and enter the result. But you have to bear in mind that the RPM will actually change under load as the tyres distort so it will be out by a few %. I always do this when I operate a dyno, but I find that most operators don't bother and just use the wheel speed as the x axis on the dyno curve.

Power figures are not inaccurate because the RPM is out. The power ATW has nothing to do with engine RPM. The dyno can accurately measure the torque applied to the rollers. It also knows the RPM of the rollers. With torque and RPM it can then calculate the power applied to the rollers. Unlike torque, power does not get multiplied by gearing, so the power applied to the rollers (which is accurate) is the same as the power the wheels are putting into the rollers, and this is the power produced by the engine minus drivetrain losses. As stated, it has nothing to do with reading engine RPM accurately.

That is not to say that you cannot do things to inflate a power figure. The dyno is very accurate at reading the power being applied to its rollers, but there are things you can to do to get the car to more efficiently put its power into the rollers with less drivetrain losses. Higher tyre pressures, looser tie down straps, select a lower gear for the dyno run. All these things and more can inflate the power figure... but the dyno is still reading power to its rollers accurately.

[flinchy]

Originally Posted by adrian@vishnu

Yep... dyno curves with torque are not that useful for much other than the shape. You certainly can't use them to compare to factory specs for other cars like people tend to like to do on forums. They can be useful if dynos used are of the same type, and the cars are of the same type, and the gear ratios are the same. Often people compare torque figures of N54s, and it is probably OK to do this as it is mostly the same dyno type and same car type in the same gear selected. I don't see the point myself, as torque does not mean that much in the real world. It is pretty easy to get ridiculous torque numbers by just pumping up the boost at as lower RPM as you can get it. Stock turbo cars can produce insane torque numbers, but are not actually that quick compared to modified cars with less torque.

Mostly the diff ratio data in the dyno is set from whatever car it was last set properly in, so it is probably not 1:1. It may be the ratio for a small 4 cylinder. Also it is not actually the diff ratio. It is the combined ratio of diff, gear, wheel/tyre size. It is pretty easy to work out on the dyno. You just go to 100kph reading on the dyno, and read the RPM off the tacho of the car and do a quick maths calc and enter the result. But you have to bear in mind that the RPM will actually change under load as the tyres distort so it will be out by a few %. I always do this when I operate a dyno, but I find that most operators don't bother and just use the wheel speed as the x axis on the dyno curve.

Power figures are not inaccurate because the RPM is out. The power ATW has nothing to do with engine RPM. The dyno can accurately measure the torque applied to the rollers. It also knows the RPM of the rollers. With torque and RPM it can then calculate the power applied to the rollers. Unlike torque, power does not get multiplied by gearing, so the power applied to the rollers (which is accurate) is the same as the power the wheels are putting into the rollers, and this is the power produced by the engine minus drivetrain losses. As stated, it has nothing to do with reading engine RPM accurately.

That is not to say that you cannot do things to inflate a power figure. The dyno is very accurate at reading the power being applied to its rollers, but there are things you can to do to get the car to more efficiently put its power into the rollers with less drivetrain losses. Higher tyre pressures, looser tie down straps, select a lower gear for the dyno run. All these things and more can inflate the power figure... but the dyno is still reading power to its rollers accurately.

yeah i can see that from stock/stock frame N54's making insane torque in the low-mid then dying in the ass lol

ahh right so you still put in a ROUGH estimation of the RPM/tire size via speedovs tacho just a couple of points?, but it's really really rough? i guess it's a lot easier lol

everything i can find on how dynos work though, states that torque is measured but power is calculated... so if it's not reading the torque right, how does it get the power?

since all power is is torque over time, if you have a 2:1 gear compared to a 1:1 gear, the 2:1 would show twice as much torque, therefore twice as much power?.. even with roller RPM and torque applied... wouldn't it still be effected by the variance in gear/engine, since you can have the roller spinning at the same speed in either 3rd4th/5th etc... with different torque applied?

or is that just how dynojet's work and DD's are a vast amount different? - ED: uhhh mhmmmmhhhh because DD's are load based ... and jet's are inertial, since the load is varied on the DD it WOULD calculate WAY differently to a jet, as as far as my mind is working, the faster you spin up a jet the more power/torque it'd think you have if it didn't know your RPM or gearing no? where something something something i'mnotentirelysurehowdynamicswork

i think id need to spend some time around dynos a bit more to actually work out what's going on the whole time properly. pity there's so many different types.

[adrian@vishnu]

Originally Posted by flinchy

yeah i can see that from stock/stock frame N54's making insane torque in the low-mid then dying in the ass lol

ahh right so you still put in a ROUGH estimation of the RPM/tire size via speedovs tacho just a couple of points?, but it's really really rough? i guess it's a lot easier lol

everything i can find on how dynos work though, states that torque is measured but power is calculated... so if it's not reading the torque right, how does it get the power?

since all power is is torque over time, if you have a 2:1 gear compared to a 1:1 gear, the 2:1 would show twice as much torque, therefore twice as much power?

or is that just how dynojet's work and DD's are a vast amount different?

Yes... torque is measured... but not torque of the engine. Torque of the rollers. What is also measured is the RPM of the rollers (which is how it gets roadspeed). Both these things are known accurately. Then Power = Torque*RPM*Constant. Very easy calculation.

Now when torque/power is transmitted between two shafts (in this case one being the axle of the car, and the other being the dyno rollers), the torque transmitted is dependant on the gear ratio between the shafts. But the Power transmitted is constant (minus losses) regardless of the gear ratio. This is simply derived from conservation of energy (and power is the rate of change of energy). This also applies to every transfer of power in the car from flywheel to gearbox input shaft to output shaft to diff to wheels/tyres. At each transfer, the output power will be equal to the input power minus losses regardless of the gear ratio. This cannot be said for torque. For torque you need to know the gear ratios to calculate the torque transfer, and this information is not normally known by the dyno unless it has RPM and can then calculate the effective total gear ratio. But even then it can only guess the losses. The same applies for power with guessing the losses. We never know exactly what they are, and that is why we generally just talk in kW ATW which is the power after losses are taken out.

Also, although power at the wheels is relatively constant with wheel size and gear ratio, and the dyno can display torque at the wheels also, but the torque at the wheel will vary wildly with wheel/tyre size, gear ratio etc. Therefore torque at the wheels is not that useful when compared to power at the wheels.

[flinchy]

Aaaaahhhhhh right that makes sense

Torque geared out not power, righto!

Would it be correct that inertial dynos don't calculate that in the same manner though since it's done with rate of change in acceleration between two rpm points?

[335i-boy]

Originally Posted by drjekl

That sounds like an ideal scenario to me also, but I thought the pump stopped so to speak once you placed the fuel nozzle back in the cradle at the servo?

Nice dyno curve also

You get to 2 attempts at each bowser before it locks you out. I remember the 2nd time I filled up with E85/98 I was watching the "dollars" or something or other instead of "litres" when filling up with 98 after filling with E85. I ended up over filling 98 and wanted to have a 3rd attempt to put some more E85 in to even up the mix. I had to go in and pay for the 2 fills then come back and add some more E85 then go back in and pay again. Won't make that mistake again.

Yeah. You want that power curve looking as much like Ayers Rock as you can. Mine could do with some work on that front

[335i-boy]

Understand what Adrian is saying. After I got the car dynoed though, I really wanted to get a figure for engine torque. I pulled out some old uni books and saw you could figure out engine torque if you calculated some other numbers first.

- Engine RPM from road speed, tyre diameter, gear ratio and final gear ratio

- Gear Reduction Factor (R) from rpm, radius of tyre and road speed

Engine torque* can then be calculated using gear reduction, tractive effort, and radius of tyre.

* Tractive Effort and Road speed are measured values (measured by the chassis dyno). Their use in this calc therefore does not incorporate any drive train losses as per Adrian and Flinchy's discussion. Real engine torque (measured on an engine dyno) would be higher than the figure detailed here.

Here is a screen grab of the excel worksheet I used. The fields in red are the required inputs, Tractive Effort, Road Speed and tyre diameter. Tractive Effort and Road Speed are drawn from intersects on the paper copy of the dyno print out (I had no other electronic data). Tyre diameter from http://www.1010tires.com/Tools/Tire-Size-Calculator. The rest of the numbers are calculated. I figure the maximum torque my car produces at the engine should be around 615Nm @ 3168rpm.




Apologies for the continued thread jacking Drawn05

[adrian@vishnu]

Originally Posted by flinchy

Aaaaahhhhhh right that makes sense

Torque geared out not power, righto!

Would it be correct that inertial dynos don't calculate that in the same manner though since it's done with rate of change in acceleration between two rpm points?

Load bearing dynos use a retarder to slow the rollers down. They then have some strain guage force sensors which measure the force applied by the retarder at a known radius to get torque applied to the rollers. This torque along with the roller RPM is used the calculate power.

Inertia type dynos use a much larger roller with alot of weight and therefore momentum. The dyno knows the rotational momentum (inertia) of the rollers from initial calibration and assuming it does not change. It also knows the RPM of the rollers. It knows the rate of change of RPM by sampling the RPM often and seeing how much it changes in a given time period. It can then calculate how much force (tractive effort) must be applied to the outer diameter of the roller to get the change in RPM. So it can then calculate the torque applied to the roller. Knowing the roller RPM it can also calculate power (which is simple once you know torque and RPM).

So although Inertia dynos work differently, the calculation is much the same and starts from knowing the torque applied to the roller. Of course the bad thing about Inertia dynos is that you can only do power runs as there is no retarder, so you can't hold a constant load. I like tuning much better on a laod bearing dyno where you can twiddle a knob on the controller to get the engine where ever you need it for tuning.

[adrian@vishnu]

Originally Posted by 335i-boy

Understand what Adrian is saying. After I got the car dynoed though, I really wanted to get a figure for engine torque. I pulled out some old uni books and saw you could figure out engine torque if you calculated some other numbers first.

- Engine RPM from road speed, tyre diameter, gear ratio and final gear ratio

- Gear Reduction Factor (R) from rpm, radius of tyre and road speed

Engine torque* can then be calculated using gear reduction, tractive effort, and radius of tyre.

* Tractive Effort and Road speed are measured values (measured by the chassis dyno). Their use in this calc therefore does not incorporate any drive train losses as per Adrian and Flinchy's discussion. Real engine torque (measured on an engine dyno) would be higher than the figure detailed here.

Here is a screen grab of the excel worksheet I used. The fields in red are the required inputs, Tractive Effort, Road Speed and tyre diameter. Tractive Effort and Road Speed are drawn from intersects on the paper copy of the dyno print out (I had no other electronic data). Tyre diameter from http://www.1010tires.com/Tools/Tire-Size-Calculator. The rest of the numbers are calculated. I figure the maximum torque my car produces at the engine should be around 615Nm @ 3168rpm.

Attachment 865211


Apologies for the continued thread jacking Drawn05

That way should get you a reasonable result, but I prefer a simpler approach. I take the kW ATW and estimate the power at the flywheels. I find the best way to do this is to get the factory claimed power and compare to a standard car's kW ATW. So with a BMW, factory power is about 225kW. Dyno power ATW is around 190kW. Therefore there is about 35kW in drivetrain losses (Note that drivetrain losses is another topic altogether, but I feel it is closer to constant offset than to constant %, but it would be less at lower wheel speed). Then I look at the tractive effort power curve to see at what RPM max Tractive effort is. Then get the power off the power curve at that RPM. Say it is 215kW ATW at 4000RPM. Then add the offset of 35kW to get to 250kW at 4000RPM which is the power at peak torque.

Torque(Nm) =(power(kw)*9549)/RPM = 596Nm

The main source of error in that approach is the estimation of drive train loss.

My WRX has 275kW ATW at 4300RPM (max torque). Because it is AWD, drivetrain losses are around 50kW. So that is around 325kW at flywheel at 4300. That is around 720Nm. It spins all 4 wheels when it hits boost in 2nd on all but the cleanest/dryest road surface. And that is with enough grip for a 1.58 60 foot at the drags with road tyres:

http://www.flickr.com/photos/pdjames/6165758110/

[Drawn05]

So I got the car dyno'd today at Advan to see what was going on with the 'numbers'. Did about 5 runs with 17litres of United E85 to rest of tank BP 98RON and all bar one was clear of any timing corrections. Perhaps the power figure would have been higher had I not had 255 R888s on the rears.



Quite happy with that result but what was rather unpleasant was the performance of my default/street map - Stage 2+FMIC Aggressive 402. It is a rubbish map that boosts way too high an yields very poor power. The logs of this map were full of timing corrections, so wont be running that map anymore.

Grabbed another 17 litres of E85 for Rozelle on the way home too.

[drjekl]

Not bad at all!

Why do you think the R888's potentially lossed you power?

[flinchy]

390whp not bad at all! Not sure on your exact mods, but that's definitely comparable to many other stock turbo n54's i believe

[Drawn05]

Originally Posted by drjekl

Not bad at all!

Why do you think the R888's potentially lossed you power?

Peter pointed out that there was quite a lot of rubber on the rear rollers that must have been deposited by my tyres, possibly because of wheelspin. There is a definite plateau in the power which was evident on both the 98RON and E30 maps, which Peter said could also be a result of the tyres. Next time I need a dyno I will put the practically unused stock wheels/runflats back on.

[flinchy]

Originally Posted by Drawn05

Peter pointed out that there was quite a lot of rubber on the rear rollers that must have been deposited by my tyres, possibly because of wheelspin. There is a definite plateau in the power which was evident on both the 98RON and E30 maps, which Peter said could also be a result of the tyres. Next time I need a dyno I will put the practically unused stock wheels/runflats back on.

but if it's because of wheelspin... the runflats having less grip would spin even more so you'd make less power?

290rwkw shouldn't be able to spin warmed up wide-enough R888's in (4th?) gear surely?!