Next gen. BOV control

[Mosaic]

Hello All:

 

I've been ghosting on the forum but the recent chat about BOV theory (now in the T shed) has compelled me to make this post.

 

I am an engineer/CEO in the final testing of a new standalone Boost multigauge/BOV controller. I deal in facts and empirical evidence.

 

Turbocharger Background.

A turbocharger is an energy converter. It takes kinetic/thermal energy from your motor exhaust and transfers it to the intake. It also then converts the kinetic energy of the now accelerated intake charge into slower moving higher pressure air. The adiabatic heating of the intake charge is a consequence of the pressure change. Intake charge heating is also due to friction between the air & the turbine as well as some transferred via the turbo housing & shafts from the exhaust charge. The intercooler cools some of this excess heat to provider a denser air charge to the motor. A denser air charge has a lower pressure than the hot air charge, therefore the cooler outlet pressure of the intercooler will always be less than the hot inlet pressure. As you know a denser air charge delivers more oxygen to the cylinders, which, in combination with more fuel builds more power upon combustion. This is the justification for turbocharging - more power from a smaller displacement.

 

 

Placement of the BOV/CBV after the IC thereby improves the effectiveness of the BOV/CBV by venting denser air for a given orifice size. Also, in the case of the CBV, cooler air is recycled to the intake, thus improving turbo performance.

 

Compressor surge has to do with the flow capacity of the turbo design. A larger turbo compressor wheel flows more air for a given pressure. If your engine cannot consume this air volume you will get compressor surge as boost rises. THE BOV/CBV cannot help here, UNLESS, it is designed to leak some of that air volume. If you replace a 'designed to leak' factory CBV with an aftermarket no-leak device it is possible to experience compressor surge as boost builds if the turbo was sized to take the leak into consideration. Solutions here are,1)- Downsize the compressor wheel, 2)-replace new CBV with old leaky CBV, 3) install a CBV bypass hose with a valve to recreate the 'leak'.

 

Compressor surge also happens when you lift off the throttle causing the air flow to choke off and revert through the turbo. In this case the BOV/CBV vents this excess surge. So the bigger your BOV/CBV the better? Well no, because we also want good throttle response, and dumping all the pressurised air charge means that boost has to be rebuilt for you to see power. This takes a little time. Lost time loses races. That's why race cars don't use a BOV/CBV at all, but then they don't mind killing the turbo after one or two races- it's all about winning and keeping sponsorship. Not about turbo longevity.

 

Well, we don't want to kill the turbo, but we also want good throttle response. Now, let's think for a moment. Turbo lag affects throttle response but it's no longer the main reason for it in any meaningful way. Modern turbos use lighter materials and better bearings so they can spool and despool quickly, thus turbo lag is small. That's why racecars don't mind if the turbo despools due to surge.

 

So what we want is throttle response, forget about turbo lag. Racecars like a pressurised IC & pipe system for best throttle response. Therefore a good BOV/CBV install SHOULD vent surgeshock AND SHOULD pressurise the IC BEFORE you complete your gearshift. It is KEY to note that it is only the high pressure INITIAL surgeshock that is damaging to the turbo. Low pressure (<5psi) surge is of NO consequence. But having 5 psi in your IC as you lift off the clutch IS of consequence to your throttle response. That is the crux of the matter.

 

To summarise then, a good BOV/CBV install shall vent the high pressure wavefront as quickly as possible while ensuring some pressure is maintained in the IC to deliver good throttle response after the gearshift.

 

Alas, quick response and maintaining pressure in the IC is a balancing act. More spring tension in the BOV/CBV increases the pressure held in the IC but it also decreases the response time for handling the damaging surge. So what manufacturers do is try to oversize the orifice of the BOV/CBV to compensate for the slower response. But the larger the BOV/CBV piston/diaphragm the more inertia you introduce so that also has diminishing returns.

Further, when you set up an adjustable mechanical BOV/CBV it doesn't know whether you're doing a time attack or city driving. So you have to compromise your performance for street driving.

 

 

Thus the only competent solution that addresses all these criteria is electronic/digital control of the BOV/CBV. This allows for fast response, which means a smaller orifice is fine. This permits calibrated open/close operation to ensure throttle response appropriate to the DRIVING CONDITIONS. Thus we see that modern vehicles are coming with stock ECU controlled solenoid BOV/CBV like the Ford Taurus SHO ecotec series.

 

That's jolly good. But what about the rest of us? Read below for the specs on what's coming to the market shortly for the rest of us:

 

 

The product has been designed, prototyped and road tested. Dyno tests are about to start to evaluate detailed throttle response benefits.

Following is a list of features:

 

Option (1) : Backlit 80 mm gauge/controller in various powder coated colors.

 

Target market: Factory turbo cars and conversions.

 

Feature Set:

 

a) Electronic boost gauge ( two ranges, vac/15psi, vac/30 psi linear)

NB A/F lean/rich indicator tuned to 15:1 at vac and 12:1 under boost (based on psi setpoint).

c) Tunable boost psi setpoint with relay driver & LED indicator.

d) Lean-boost LED alarm & relay drive based on items ( & c)

e) Smart turbo timer/ setpoint breach indicator based on item c). Led display.

f) BOV/CBV controller with Sensitivity & Duration tuning. Includes a scramble switch for max sensitivity suitable for time attack runs as opposed to moderate streetable tunes.

g) Ruggedized map sensor suitable for harsh marine environments.

 

Item © in concert with (f) will deliver overboost pop off.

 

 

Option (2): Backlit 52mm gauge/controller / gauge cup included.

 

Target market: High performance Turbo cars - STi/EvoX/GT-R etc.

 

a) Electronic Boost gauge (vac to 40psi linear) , 540 degrees sweep, 100% more sweep than normal.

Tunable boost psi setpoint with relay driver & LED indicator.

c) BOV/CBV controller with Sensitivity & Duration tuning. Includes a scramble switch for max sensitivity suitable for time attack runs as opposed to moderate streetable tunes.

d) Ruggedized map sensor suitable for harsh marine environments.

 

Item ( in concert with c) will deliver overboost pop off.

 

This product caters to the serious motorsports enthusiast/racecar, featuring compact size, full size LEDs, 540 degrees of sweep and ruggedized 4 bar map. It reorients & repackages the key features of option (1) above.

[hoov100]

Ok?

[proxlamus©]

Im interested to see what Tony D has to say about this.. "turbo lag"

 

Where did the magic number of 5 psi come from?!

 

There are quite a bit of fallacies in this post with poor information and grammar.

 

Would you mind cleaning this up a little bit and maybe explaining your product in more detail rather then telling us how and why you feel a blow off valve works?!

Edited May 31, 2010 by proxlamus©

[djz]

I'm fairly certain I have seen "race cars" fitted with blow off valves before, or is this some change that has happened overnight?

[Mosaic]

Im interested to see what Tony D has to say about this.. "turbo lag"

 

Where did the magic number of 5 psi come from?!

 

There are quite a bit of fallacies in this post with poor information and grammar.

 

Would you mind cleaning this up a little bit and maybe explaining your product in more detail rather then telling us how and why you feel a blow off valve works?!

 

What fallacies do you observe?

5 psi is just an example of low boost for which compressor surge has negligible impact on modern turbos.

Forgive my grammar, as I said I deal in empirical facts not excess loquaciousness

 

On the issue of turbo lag. What the average person considers lag is not the fault of the turbo. It is the lag to charge the IC. Turbo lag has to do with the inertial & frictional delay of the compressor wheel in spooling up, once sufficient exhaust energy is achieved. Remember when heavy metal flywheels were 'shaved' to improve engine 'spool up'?

 

Basically if you upgrade from a 2" line and small IC to a 3" line with a large FMIC your will introduce lag, the turbo spools up independently of this. The lag you introduced is not Turbo lag. When engineering a solution to this 'other' lag, we are not engineering a method to spool the turbo faster, but a method to keep the IC charged without compromising other parameters.

 

For simplicity we can call this lag 'Volumetric lag' as it differs from turbo compressor wheel inertial lag.

 

I hope that makes the discussion a bit clearer.

 

If you have specific questions about the product, please keep it technical and not commercial.

Thanks for your comments.

Edited June 1, 2010 by Mosaic

[Tony D]

Does the fact that this product possibly already exists in the marketplace get this post classified as a 'techinical' or a 'commercial' comment?

 

I think my engineer has returned from China, I will call him Friday morning and see if he likes the way I left his cubicle, and get more details on this. I don't believe he sourced his BOV/Boost PID controller from Trinidad.

 

The control you propose is a simple PID loop with surge points mapped into a controller and a dual output to Wastegate and BOV. Once venting via BOV is possible, acceptable sizing paradigms of compressor wheels for low speed operation change dramatically.

 

There is nothing new, only a rediscovery of another application with suitable reapplication to a new application...

[Mosaic]

It's not new insofar as the individual elements.

Its new insofar as the combination of features and the method of implementation.

 

I'd be interested in hearing about a similar product. There really aren't many out there. BTW its not a PID, its Model Predictive Control in action.

Edited June 4, 2010 by Mosaic