Volmetric Efficiency

[Davezj]

Does anyone know the volumetric efficiency for the 6A13TT engine

i know it is estimated that a 4 valve per cylinder engine is about 90% but I wanted to know if anyone had the exact value. I am talking about a standard engine not modified.

[paulg23]

Don't know it but if you can log some ecu parameters you will be able to calculate it. Guess you will have to disable the turbos.

http://installuniversity.com/install...n_9.012000.htm

[Davezj]

i would have thought some might know this

[Kenneth]

Assuming your MAP sensor scaling is OK, then 2.6 bar is 1.6 bar of boost absolute (1 bar atmospheric + 1.6bar boost). Are you sure your MAP pressures are reading correctly?

However, you should try working in kPa. Why? Because 100kPa = 1 bar and, conveniently for us, 100kPa @ 100% VE ROUGHLY translates to 100% load

VE is therefore easy to calculate from your ECU logging. If you get 100kPa at 100% load at any RPM, then you effectively have 100% VE.
If, on the other hand your MAP pressure is 260 kPa but your load is only 200, then VE = 200 / 260 * 100 or 76% VE

I would expect that VE on a 6a13 to exceed 100% by a reasonable margin, probably 110% or more at peak torque.

yes i have the map senor fitted to rear O2 pin on ecu and i can monitor it on request 3C in evoscan.

kenneth the MAP sensor is saying the boost pressure is 2.6 bar, is that 1 bar atmospheric + 1.3 bar boost or 2.6 bar of boost.

OK i understand what you are saying about starting a new thread.

[Davezj]

thanks kenneth,
if the VE is around the 100%+ mark in the reagion where the turbo is at full spool, say 3000 rpm to 6000rpm then that would make a massive difference to my other calculations that i have been working on.

i will have to start logging the data to see what it reviels.

thanks again kenneth.

[Davezj]

Ok so If I understand this correctly, if I am using a boost controller and it is set to 1 bar (100 kpa) and get into the 160 load cell, which I don't believe is a difficult thing to do.
the VE is 160% at that point in the rev range surely that can't be right.


Sent from my space-aged gizmo

[Kenneth]

No, that isn't right.

Remember what I wrote. 100% load is effectively the same as 100kPa at 100% VE.

This is the major difference between MAP and MAF, and why MAF is, at least on a production vehicle, a better solution.
160 load could be 160kPa at 100% VE. It could also be 100kPa at 160% VE (given constant temperature, which isn't really going to happen). A MAF is designed to measure mass air flow, which coupled with mass fuel flow, is able to give consistent AFR over a wide operating range and also be tolerant of changes in VE over time.

MAP on the other hand, requires VE to be a known constant so that it can use the MAP pressure and temperature (plus baro etc) to calculate fuel requirement. As soon as VE changes, you have a change in your fuel because the air mass flow changes.

Anyway, back on track.
Lets say 100% load = 100kPa at 100% VE. When you are pushing through more boost, you are increasing the kPa value as well as the load value. So all you do is re-arrange the formula and get something like 160 load at 160kPa = 100% VE.
This is why you log MAP and Load @ RPM. by knowing load (and assuming load = kPa at 100% VE) you can then calculate the VE.

Does that make sense?

Ok so If I understand this correctly, if I am using a boost controller and it is set to 1 bar (100 kpa) and get into the 160 load cell, which I don't believe is a difficult thing to do.
the VE is 160% at that point in the rev range surely that can't be right.

[Davezj]

So it is

(load / kpa) * 100 = VE %

(100 / 100 ) * 100 = 100% VE

100 kpa @ 100 load VE = 100%

160 kpa @ 160 load VE = 100%

I get that above ,
so the below must be true.

120 kpa @ 100 load VE = 83%

100 kpa @ 120 load VE= 120%

100 kpa @ 160 load VE = 160%

Which is what I said above isn't it.....

or am i still missing something?

i have sent you some rep points for being so helpful and understanding when i probably asking some stupid questions.

Sent from my space-aged gizmo

[Kenneth]

1 bar of boost = 200kPa absolute, roughly. So that is about 80% VE

[Davezj]

1 bar of boost = 200kPa absolute, roughly. So that is about 80% VE

yes ok i missed that fundamental point that the kpa is absolute pressure so atmosphere plus boost pressure.

so using that info,

200kpa (1 bar boost) @160 load VE = 80%

so at any given load value as you increase the boost pressure the VE goes down.

the 100% VE at 160 load is 0.6 bar boost.