Hi guys:

I am about to begin testing a proposed solution to three regular problems at once!

1) Part throttle surge

2) Sluggish/ improper, hard to tune, BOV Action

3) Throttle response .

I'd like to share the system design with u as a forum since these problems seem to occur when tweaking quite often.

The system is based on a hybrid, intelligent, user tunable, BOV & Boost controller & Boost gauge, AFR display & Tachometer. 80 mm dial gauge interface with both LED sweep and Digital readouts. The sweep display & digital displays can tie into different signals as desired. Eg. Show a boost sweep and digital RPM is one option.

Anyway , I am focusing on the areas that speak to the heading here.

Part of the difficulty with part throttle turbo surge is that it can happen lower than the 7-11 psi wastegate spring rate. This takes the surge solution out of the boost controllers' capabilities.

So if u have surge at 5 psi , part throttle, what can be done? Other than changing your turbo/housing/wheel.

The solution is to run the hybrid BOV/boost control simultaneously on the cold side BOV. Any decent BOV is fine.

Steps:

1) Reduce the BOV spring rate to 2-3 psi (by shortening it or replacing it or adjusting the tension in the adjustable BOVs)

2) Tune the RPM/boost map in the boost controller to limit boost during the RPM range that matters.

3) Tune the BOV controller to snap the BOV open and closed based upon your desired sensitivity and duration.

Benefits:

1) No Surge.... & smooth acceleration
2) A VERY responsive BOV - low spring rate gives this.
3) Better post gear-shift IC pressure....tuned BOV duration gives this.
4) Resulting in overall better throttle response & boost spool etc.

What do u think? 3 steps to 4 benefits. A decent new tool in the ever changing world of performance tuning?

 

Is this for a evo??

 

Hi,
Thanks for your question.
It's for any performance vehicle. I will be doing specific EVO testing as well.

 

Seems like it may be pretty easy to overspin a turbo trying to do this?

I assume you could actually use this as a form of anti-lag by opening the BOV to help the turbo free wheel when off boost?

 

wouldn't boost control via TPS and RPM solve this?

 

^ no because it would have no action at boost levels under the wg spring pressure as stated above. . .

 

you could run a Synapse BOV then...

 

RSMike, I'm afraid no mechanical BOV will solve part throttle surge unaided. A lot of confusion surrounds BOV and surge but simply, a BOV handles OFF throttle surge ONLY. Boost control handles ON throttle surge ABOVE the stock wg spring rate.

The solution we are discussing intends to HANDLE ALL surge. With Superfast (sub 40 ms ) low spring rate BOV - fully open response for OFF throttle surge.


That statement has merit. In the case of part throttle surge, unloading the turbo on the cold side will develop somewhat higher turbo RPM. Notably though this is at relatively low boost pressures otherwise a regular mapped boost controller could manage it. Thus 'overspin' which implies exceeding the turbo rotational spec isn't the right word.

Antilag or improved throttle response is part of the systems deliverable results

 

trying to electronically control a BOV sounds like a pain in the ***. You'd be far better off to use a solenoid to meter recirc flow to control surge, much like a honda controls idle.

 

Hi Griceiv:

While it is simpler to directly control a solenoid valve, AND the system can do it if u like by replacing the BOV with a full electric solenoid valve, there are caveats.

It costs more, and u have to do custom plumbing/alum welding, and a 1" solenoid valve weighs quite a bit as they tend to come in brass. The alum/Asco ones are also bulky and cost upwards of $300 USD ea. Then it's just kinda inappropriate for a 'show' car to have plain jane industrial valves under the hood. Looking good is part of the package in performance cars.


As electric BOV become more common / readily available that paradigm might change.

On the matter of electronic BOV control, it's no different than the wastegate boost control. You control a pneumatic signal to a valve using PID algorithms.

 

i wasn't suggesting replacing a mechanical bov with a solenoid valve. I was suggesting adding a solenoid valve (<1") in addition to a normal bov. You could ditch all the complicated PID control and just have a boost switch shut your calibrated leak off above your surge threshold.

if you're going to go through all the hassle of designing an electrically actuated valve, might as well go to the source of the problem and do a wastegate actuator.

 

Could you please be more specific at what ranges we are talking about?
0psi, 15% throttle while accelerating?
or 4psi, 25% throttle etc?

My FP Red used to surge something cronic coming onto boost @ 4000-4500rpm.
We could use boost via tps/rpm to solve that.

I can go up a hill @ 20% (ish) TPS, at zero or low boost. The Synapse is expelling air while the car is still accelerating. I'm assuming this is because the compressor is flowing more air than the engine is willing to accept - This would have surged if the BOV wasn't open...

 

^ yep, this is exactly the reason the stock valve does not surge - it opens partially under conditions just as you mentioned. Just does not hold much pressure as you crank up the boost.

 

Aha! An electronic wastegate actuator using an electronic solenoid rather than a vacuum/spring operated system. Could vary WG duty cycle infinetely from 0psi to 100psi based on throttle, speed, gear, whatever inputs you wanted to have. . .

Sign me up for one!!

 

If the synapse is venting air while u are accelerating, AND under low boost, then when does it stop venting boost?

And what stops it?

If it doesn't close properly u are ALWAYS venting boost. This being so would affect your upper RPM /post surge performance negatively as you are venting useful boost. If you have a boost limit that your turbo can make (albeit a bit more slowly) even with the venting, then you can run with the 'lost' boost. Your intake charge might be a bit hotter than necessary due to higher than necessary turbo RPMs to make that boost though.