Hi all:

I am developing code for a 2 button product with an Interface much like the AEM truboost or Turbosmart Eboost2

It contains a boost controller. However, the use of the tps angle is included to offer better boost control than other devices in its class. Not a full RPM/TPS map though, as a 2 button, 4 digit, interface is too cumbersome to manage/view such a data matrix.

I wanted to bounce the following approach off the forum for your thoughts as to the workability of the approach.

So please read and comment:


RPM is a so-so reflection of the engine loading without gear position data.
TPS is a reflection of driver intent & RPM vs TPS angle is a better reflection of engine loading.

Taken together they should balance the boost levels as mapped for a particular vehicle.

I have a possible implementation as follows:

RPM map all the max desired boost pressure /duty% thru the 19 cell 1000,1500,2000,2500.... to 9900 rpm range.
This will take surge control into consideration over any particular user mapped rpm range.
Apply a TPS factor ( to ALL RPM cells between a 2nd user mapped Hi/lo rpm range) based on the following calculation:

Formula: ( Max RPM_mapped Boost) * ((TPS-MinTPS)/(MaxTPS-MinTPS))

So 20% throttle gives 20% of the max boost as mapped for the current interpolated rpm . Which could work out to 2psi for a 10psi max or 6 psi for a 30psi max. RPM Cells outside the 2nd User mapped range simply apply the Boost limit as mapped with no TPS influence.

Real world application:
This handles the road conditions as determined by the driver. Coasting downhill at a particular RPM with a small throttle angle or maybe geared down while approaching a corner at 4000 rpm with minimal throttle, will not make boost. Going uphill at 4000 RPM and max throttle WILL make MAX boost as mapped for 4000 RPM. Or coming out of the corner with the throttle at 50% will give 50% boost at the current RPM mapping easily ramping up to 100% based on your foot.

From where I sit this seems superior to just RPM based boost maps or much better than a fixed duty cycle for a fixed boost limit.

Thx for reading!!

 

bump!

 

In practice I wonder if it will have any true benefit. When driving you tend to use the TPS for load control (as you stated). That works fine as far as I am concerned - the TPS based boost control seems redundant.

 

The problem I see is that a boost controller only adjusts what is seen over the wastegate pressure, and arguably its best to set the wastegate pressure so it by itself will get the boost to with in 10-20% of the desired level. Then let the MBC or EBC control it to get to the set point.

So with that said, you're only controlling what is above WG pressure and most of the low boost from the throttle based controller is overcome by the wastegate anyways.

 

Yes, if u do it that way u remove some of what an ebc can do as the WG creates a minimum 'floor' of boost. However, this approach IS more for an mbc leak system.

Sometimes that approach is required if exhaust backpressure is overcoming the WG spring making preload necessary.

The best approach with an ebc is to ONLY apply more WG preload IF the WG can't hold the desired peak pressure, or a pressure fall off is seen at high rpms.

The advantage of having the TPS influence the max boost at any given rpm is driveability. RPM only or duty cycle based ebc's will get u to your peak boost retarded only by turbo flow limitations. With a good turbo setup it's easy to see max boost at 5000 RPM and 50% throttle in a low gear. Chances are max boost isn't what u want /need when u're at 50% throttle in a low gear. This I know having shredded an auto transmission in 2nd gear.

That is the reason for the Tps influence, but its overall benefit is reduced the closer the wg 'floor' is to the actual max boost.

Let me add this though. The system we are talking about has hybrid capability and has integrated the boost control and BOV/CBV control into 1 unit. SO it is quite possible to apply boost control on the COLD SIDE using the BOV/CBV as a WG, eliminating the limitations of the WG PREload on the range of boost that u can set. That being so, the avg BOV/CBV tension is around 7 psi, and can be lowered to about 3 psi with the adjustable ones. Thus a much larger boost control range is possible allowing for (rpm mapped) partial throttle surge control and true TPS/RPM governed boost for drivability.

The advantage with the cold side management is that the BOV/CBV WG is pressure compensated by the actual controlled pressure, making the spring preload only necessary for keeping the BOV/CBV shut during soft vacuum. Even this soft vacuum issue is removed when the BOV/CBV vacuum line is under 3 way solenoid valve control.

 

I'd also like to point out that cranking the WG preload up high negatively affects the throttling ability of the WG. It takes large changes to get a small reaction from the WG which manifests as spikes & creep.

Properly applied ebc ought to get around 100% more boost than the stock wastegate preload.
So a 15psi gate = 30 psi boost under good ebc .