It should not throw timing off because the load in theory should not change, well not in my case. Fuel definetly yes, it will either go lean or rich, dependant state of tune.

While we are discussing making more power, surprisingly around 4k-5k rpm I found reducing boost (from 2.2bar to 1.95bar), after tuning/de-tuning mivec, made it further leaner with no knock also. Advantage here I was able to run leaner, less boost and more timing, in theory making more power.

This is on pump fuel.

 

it will throw off timing due to hitting different load cells. I have seen tunes that have very specific cells tuned so if you alter the MIVEC it could go to an "untuned" cell.

 

I still need to confirm the lower MIVEC improves power at high boost/flow, but I've been thinking about it a bit more. The issue has got to be high exhaust gas pressure causing flow reversal when the intake valve opens. At high boost levels, the exhaust gas pressure goes up because the turbine has to do more work. At high exhaust gas volume at higher rpms (but perhaps lower boost), the exhaust gas pressure goes up again because there is so much exhaust gas being generated that the turbo becomes a bottleneck.

 

guys unless you have access to a dyno - you should all be logging 2byte airflow to see what MIVEC changes are making.

if airflow increases then you are making more power

 

exactly Dave.

2 byte airflow can tell you alot...I still think it will tell you when you hit peak power if you look for it closely. Just watching the airflow increase and drop RPM is a sign that something either works or doesnt...then add in 2byte load and it can be confirmed.

 

really depends on where you are looking at 2byte airflow. Up top is much different than down low, espically on stock or variant turbos.

I've seen the 2byte up top stop gaining far before I reached max HP on some setups. (non-octane limited)

 

how do you mean?

ie same airflow = different dyno numbers?

 

I stand corrected. On the turbos I have done its always linear, unless you mean something different than I am understanding. It seems that it will be really consistent on gains and then suddenly revert, when it does that (other than measurements off the map as it were, 35R or 61mm) it usually coincides with peak power.

this is interesting

 

Yes, maxed out 2byte airflow but more power to be had. I.E from timing/AFR/etc, non-octane limited.

Let me try and find some logs...

 

Here is data from a FPred I just did on Friday

91octane @ 7500rpm:

Airflow2byte: 2192.46
lb/min: 43.83
Boost: 22.45
Horsepower: 358whp


100octane @ 7500rpm:

Airflow2byte: 2178.60
lb/min: 43.53
Boost: 22.83
Horsepower: 398whp

 

maybe power should be defined as airflow/time

ie same airflow but in less time = more power

 

Well more airflow usually means more power, I am just saying it's not the end all of power. Which was my point. Up top where some turbos just can't flow anymore, the airflow will not increase anymore, even if more power is being produced by other means...

 

yeah sure... I mean if you take out of the equation timing or octane then airflow = power

You want to get the most airflow and then try and make the most power with it... (with a correct AFR and best timing).

^ this is all my opinion, based on what i have read and my own experiences (which arn't much) - please dont take it as gospel (i know RL and JB dont) - i could be and probably are wrong.

 

Hey mate,

You're not far wrong... All things being equal, you want to get as much airflow through the engine as possible... Once you've dialed that in, then by maximising the AFR's and timing, you *should* be able to make more power.

That's why I'm making more than anyone else around here on the stock turbo on pump fuel!

 

Dave, that is how I understand it as well.