Uprated turbos for N54 in an E89 35is

pbondar

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May 30, 2020
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I’ll pass on the E85 here in the UK….it’s around 100 USD for 20 litres…ditto on the Octane booster..

Our 98 ron is either 100% petrol or a max of 5% ethanol…

They just have moved our 95 octane to 10% ethanol.

i’ll just have to limp on with 98/99 Ron…first world problems..
 

Torgus

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Nov 6, 2016
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ACF 6466 E92 + METH
I’ll pass on the E85 here in the UK….it’s around 100 USD for 20 litres…ditto on the Octane booster..

Our 98 ron is either 100% petrol or a max of 5% ethanol…

They just have moved our 95 octane to 10% ethanol.

i’ll just have to limp on with 98/99 Ron…first world problems..

Water/Meth is usually relatively cheap and really helps pump gas increase it's AKI. Also, the kits can be fairly inexpensive all things considered.

Might be worth considering after you finish your pump gas tune.
 

pbondar

Sergeant
May 30, 2020
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Water/Meth is usually relatively cheap and really helps pump gas increase it's AKI. Also, the kits can be fairly inexpensive all things considered.

Might be worth considering after you finish your pump gas tune.
Thanks I’ll climb my personal learning curve with straight petrol…once I’ve mastered driving 500bhp around the country roads of Scotland I may then revisit ..😂👍
 

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Neg89

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Jul 4, 2021
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If someone want to buy 6.000km used set of TTE500 from my e89 LHD, pm.Then ibmaybe upgrade to tte600.
 

pbondar

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May 30, 2020
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If someone want to buy 6.000km used set of TTE500 from my e89 LHD, pm.Then ibmaybe upgrade to tte600.
Sadly just got these babies two days ago…🙈
 

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Darke Peak

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Aug 23, 2022
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Ehanol blends lead to higher fuel consumption as simply the energy content is declining the higher your ethanol mix gets.
As you consume more fuel you naturally generate more exhaust gasses. The advantage is that with that your turbos start spooling quicker because the exhaust gasses are starting to move faster as new ones are coming fast from new burned fuel.
Sorry to dredge up an old post. I’m fairly certain that turbos don’t spool faster on E-blends just because more fuel was burnt. It’s air volume, and the resultant pressure as it is restricted, that spools a turbo, not the quantity or type of chemicals (gasses) in that air. Simply, the engine RPM dictates the volume of air available to spin the turbos.

E-blends may feel like they cause faster turbo spool because they generate more power, which leads to an increased rate of change to the RPM, thereby causing turbos to spin faster.
 

wheela

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Jun 4, 2021
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Sorry to dredge up an old post. I’m fairly certain that turbos don’t spool faster on E-blends just because more fuel was burnt. It’s air volume, and the resultant pressure as it is restricted, that spools a turbo, not the quantity or type of chemicals (gasses) in that air. Simply, the engine RPM dictates the volume of air available to spin the turbos.

E-blends may feel like they cause faster turbo spool because they generate more power, which leads to an increased rate of change to the RPM, thereby causing turbos to spin faster.
It's been > 20 years since i've had to calculate turbine power (what spins the compressor) so the details aren't fresh. But to do so, you need to know the pressure and temperature both upstream and downstream of the turbine, as well as the mass flow rate through the turbine.

Ethonal blends require a lower AFR for stoichiometric. So at a given MAF, an engine running e85 will need more fuel injected than one running 93. Since mass is neither created or destroyed in the combustion chamber, the engine running e85 has a higher mass flow rate in its exhaust stream than the one running 93 because more fuel (which has mass) is injected to the combustion chamber, despite both engines consuming the same amount of air. So at a given MAF, the engine running e85 produces more exhaust mass flow to drive the turbine than one running 93.
 
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Darke Peak

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It's been > 20 years since i've had to calculate turbine power (what spins the compressor) so the details aren't fresh. But to do so, you need to know the pressure and temperature both upstream and downstream of the turbine, as well as the mass flow rate through the turbine.

Ethonal blends require a lower AFR for stoichiometric. So at a given MAF, an engine running e85 will need more fuel injected than one running 93. Since mass is neither created or destroyed in the combustion chamber, the engine running e85 has a higher mass flow rate in its exhaust stream than the one running 93 because more fuel (which has mass) is injected to the combustion chamber, despite both engines consuming the same amount of air. So at a given MAF, the engine running e85 produces more exhaust mass flow to drive the turbine than one running 93.
This is interesting. I went searching and found a flex fuel site (point 4 at https://eflexfuel.com/us/blog/does-e85-make-more-power-heck-yeah)claiming that turbo spool is faster with ethanol because of “increased exhaust gas flow”. It’s also been >20 years since I studied Physics and Chemistry at uni. Your “conservation of mass” argument initially makes sense but then it makes me wonder if the “conservation of energy” is counteracting it. If you believe that there is a greater mass of fuel and air in the chamber for an ethanol blend then it is also going to take some extra energy to accelerate that additional mass to eject it. That website also claims in the same point that ethanol has higher combustion pressures so does that mean you are more likely to lift the head while running E85? Less chance of a hole in a piston but more chance of stretching head bolts?
 

wheela

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Jun 4, 2021
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For the energy balance, your main inputs are the energy from the fuel (energy density of fuel x mass of fuel) and energy added from the compression stroke compressing the mixture. The main outputs are heat loss through cylinder ( cylinder walls, head, piston, etc.), frictional losses, the work done by the piston moving, and whatever is left is what's going out the exhaust as heat energy.

E85 has an energy density around 29.7 kJ/g, while gasoline is around 46 kJ/g. So per gram of fuel, e85% has about 35% less energy. However, you need more fuel to hit to hit stoic with e85. For example, assume an engine consuming 100g of air. To hit 14.7 stoich with gasoline, you need 6.8g of fuel. To hit 9.7 stoic with e85, you need 10.3g of fuel. This is 3.5g, or 51% more fuel (mass basis, not volume). So with e85, you have about 35% less energy per gram, but you need about 51% more fuel mass at the same airflow and stoichiometry - this is a net energy gain for the system running e85 (at same mass air flow and stoichiometry).

I don't know how the combustion temperatures differ from e85 to gasoline, but that will be a factor in cylinder pressure generated during combustion.

As far as lifting the cylinder head, I'd correlate that mostly to the torque the engine is producing, as that is directly related to cylinder pressure, which is what would lift the head. E85 is more knock resistant, so you can run higher engine loads (airflow expressed as a percentage of cylinder fill per stroke), and therefore higher torque/power with e85. So you have a greater potential to lift a head with e85, but that's mostly because it allows you to push the engine harder.

EDIT: I forgot a key output in the energy balance above, which you touched on - work done by the piston pushing against exhaust gas pressure during the exhaust stroke. Back pressure is a killer!!!
 
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Darke Peak

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Aug 23, 2022
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Thanks for the detail wheela. So if we are talking about the effect of additional kinetic energy due to higher mass of fuel with e85, then we can’t ignore the mass of the associated air. It might be 51% more mass of fuel but that is the minor ingredient. From your example:
100g air + 6.8g gasoline = 106.8g
100g air + 10.3g e85 = 110.3g
Therefore 3.3% extra mass for e85, not 51%.

I don’t think a 3.3% increase in mass would make a noticeable difference to turbo spool.
 

wheela

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Thanks for the detail wheela. So if we are talking about the effect of additional kinetic energy due to higher mass of fuel with e85, then we can’t ignore the mass of the associated air. It might be 51% more mass of fuel but that is the minor ingredient. From your example:
100g air + 6.8g gasoline = 106.8g
100g air + 10.3g e85 = 110.3g
Therefore 3.3% extra mass for e85, not 51%.

I don’t think a 3.3% increase in mass would make a noticeable difference to turbo spool.
51% was relating to fuel volume, not total mixture volume (6.8g + 51% = 10.3g). Though I did mis-calculate the total energy in fuel charges; 6.8g of gasoline has about 312.8 kJ, which is a little more than 10.3 of e85, which only has about 306 kJ.

I haven't run e85, so I have no personal experience with how spool compares to gasoline. However, my point is that if people running it are noticing better spool, I don't see any technical reason to question it, as there is more exhaust mass flow for a given load when running e85.
 

JohnDaviz

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Jan 6, 2019
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Aren´t we overlooking the state of aggregation here?

1 liter of water turns into 1700 liters of steam (volumetric expansion during the change from fluid to gas).
I would assume that also fuel injected is liquid and turns into gas.

Weight should be less important than the added gas volume.

BTW. This questions is probably asked under turbo guys similar often to "what is the best oil" and answered for ages now..
 
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Darke Peak

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Aug 23, 2022
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51% was relating to fuel volume, not total mixture volume (6.8g + 51% = 10.3g). Though I did mis-calculate the total energy in fuel charges; 6.8g of gasoline has about 312.8 kJ, which is a little more than 10.3 of e85, which only has about 306 kJ.

I haven't run e85, so I have no personal experience with how spool compares to gasoline. However, my point is that if people running it are noticing better spool, I don't see any technical reason to question it, as there is more exhaust mass flow for a given load when running e85.
Thanks for your comments. I am running E50 now for a few months. The car has more power but I can’t say it has noticeably faster spool time. Maybe there is something in it.
 
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