Turbo map

[SimonUK]

Soon our turbo setup will be ready for mapping on our EFI Euro 1 ecu.

Just wondering if anyone could let me know how they are dealing with the fueling under boost conditions. I will probably go for a Alpha-N setup with the MAP corrections to deal with boost.

1bar absolute being 1x correction and 2bar absolute(1 bar boost) using a 2x correction. All other pressure sites going on this basis.

This will be done before any mapping takes place and shuld allow a good map to be created.

How does this compare to what other teams are doing? There are a few of doing it, but the restrictor complicates matters. I was advised against a speed-density system as apparently it is difficult to map without an air compressor in the dyno cell to provide a constant pressure.

Thanks

Simon

[Dan Deussen @ Weber Motor]

I'm gonna let you in on a little secret. The Alpha-N setup with MAP correction works well if you don't plan to use Anti-lag strategies later on, at least not on our systems. If you are using a turbo with an integral wastegate, disconnect the linkage and leave the wastegate wide open and create a calibration based on this setup with minimum boost. Then connect a throttle cable to the wastegate and you can now manually control boost levels. This setup should allow you to tune your MAP correction tables quite easily.

I hope this helps.

[SimonUK]

Thanks for the reply Daniel.

On my understanding an engine at twice the pressure needs twice the fuel to maintain a stoichmetric (or other) mixture. Air temperature correction tables will cover any inlet temperature increases do to the compression of the air.

How do you mean tune the Map correction tables, would my assumptions not be correct for when the engine is running, I have read some of this from the DTA manual which gave me this idea initially. It recommends to set the MAP table corrections as suggested and then map the engine.

Obviously if there is a better way of doing it i will try that.

This setup should also cut the fuel right down when the throttle is closed which will be handy for saving a bit of fuel on the endurance.

Cheers

Simon

[Dan Deussen @ Weber Motor]

Simon-

I am not quite sure how the software works that you are using but let me try to explain again what I mean by tuning the MAP correction tables.

First, I don't think that your assumption is correct that twice the MAP will result in the engine needing twice the fuel. Twice the MAP does not result in twice the cylinder filling as there are pumping losses involved which exponetially increase with pressure. At lower boost levels the assumption might work, but the more you boost the engine the more it will be likely to be incorrect.

When you disconnect the wastegate linkage and leave it wide open, you will have an almost naturally aspirated engine. Tuning this engine with the alpha-N system should be quite easy. Then when you have this base map calibrated you should connect a throttle cable to the wastgate and then in order to have the ability to manually control boost. You can then calibrate your MAP correction tables accordingly. I would not recommend running this setup if your MAP correction table is only 2-dimensional, as your corrections would be applied across all throttle and rpm ranges, which might not be correct. If this is the case I would tune the entire system only based on MAP.

Also, don't forget that when increasing the boost, you will have to retard the spark advance.

[SimonUK]

hi Daniel

This is what must of confused me... The Map correction table is only 2 dimensional on our software. http://fsae.com/groupee_common/emoticons/icon_frown.gif

I was suggested a method by one of the university contacts who works at AER (advance engine research. He suggested mapping it with no boost by having the wastegate open as you sggested and then having the MAP corrections for fuelling as 1 for pressures less than and equal to 1 bar then increase the Map corrections as the pressure increased above this. Similar to what you suggested

I was planning on 2 deg of ignition retard for every 3psi of boost.

Thanks for your advice, i shall investigate further i think.

Regards

Simon