will launch control work with a BOV?

Ya I know, thread title may be confusing, hear me out...

Stuff that may be relevant:

Car is pro-tuned.

Manual boost controller.

Eliminated egt sensor in uppipe.

3 inch turbo back exhaust.

Cobb AP2

Lightweight flywheel and super cool clutch for mad powah.

Just put a GFB TMS respons on it.

Didn't do any tuning.

Had the thing venting to atomosphere.

Turned on launch control.

Bogged the launch.

Upped the RPMs, bogged again.

Decided to forget a 3rd attempt.

I've used launch control successfully before, but that was a while ago, before the new clutch and flywheel.

Don't know if the bogging condition was caused by clutch issue or maybe something to do with the BOV causing a momentary rich condition (if that was even occuring) while the vehicle attempted to built boost and the computer going wonky.

So yeah, think the rich condition caused by the BOV could cause Cobb's launch control to not function properly?

I could always just close the BOV and try again, but it's easier to post about it and ask than beat up my car on the street.

MBC.... ugh.

Anyway, the thing you said about it going rich sounds plausible. Full VTA would certainly make it go pretty rich during a vent and it would be venting rapidly during LC I believe. Engine might not have the opportunity to burn off the excess fuel.

What RPM are you launching from?

Only one way to find out. Close the valve and try again, sorry.

Seriously though, MBC. I can't say enough how much I'm against those unless implemented in a 'hybrid' system.

New guy on here, but been a NASIOC member since 04/05. First I'll say there is absolutely nothing wrong with a manual boost controller as long as the car was tuned for it, and the owner knows enough not to just randomly add more boost to a tune that was done for xx psi.

Anyhow, about the launch control, I would first ask what rpm you were trying to launch from? what flywheel you have? and whats the launch surface? I have a GT now, but I came from a 460hp wrx and used to launch at 6200rpm. Yes it was an extreme setting and done for drag racing, but with the average legacy being what 3500+# with a driver, throw on a lightweight flywheel and a grabby clutch, your gonna need some rpms to get moving. Another thing that I'll bring up is that just having launch control does not always guarantee a good launch, your still gonna need to have the correct rpm set, and more importantly to you and your flywheel set up, your gonna have to modulate the clutch to get a good launch.

This is a speculative scenario, but lets just say you have a stronger than stock clutch and less rotating mass on the flywheel, then have the lc set too low, your going to bog. There are way more things involved, but it basically revolves around clamping force, inertia, traction and the mass involved. I can't see the bov causing an issue unless you didn't connect a boost line to it and it was just venting under any manifold pressure. I used a Tial 50mm atmospheric bov on my wrx at high hp levels, even on a stage 2 bugeye I had in the interim I switched a bad oe bov to an APS unit vented to atmosphere, and on the same basic tune, only changes involved tip in values which had no relevance to launching the car.

Every set up is different, but my ultimate suggestion if you have no other mechanical issues would be to raise the rpm some, then remember with a lighter flywheel and a stronger clutch you will need to slip the clutch some.

As an afterthought, I have always tuned with ecuflash, and the launch control settings had a mph allowance for rollout. Not sure how Cobb works with reguards to that, but using less mph in that setting will allow the car to get off the LC and rev higher faster thus helping not to bog kind of a balancing act and just more thoughts that may or may not help.

Bottom line would be what RPM your setting LC at and maybe what type of surface your trying to launch on. Setting your cars launch control to function well on a dusty road, then trying to take it to the drag strip would equal bogging also.

Trey

New guy on here, but been a NASIOC member since 04/05. First I'll say there is absolutely nothing wrong with a manual boost controller as long as the car was tuned for it, and the owner knows enough not to just randomly add more boost to a tune that was done for xx psi.

Welcome!

Respectfully, I strongly disagree with that last statement when it comes to our cars. I posted this before and I've had NUMEROUS debates here about the advantages/disadvantages of MBC vs EBCS and this is what it boils down to:

• MBCs are cheaper than EBCS
  
• It is easier to dial in boost control for MBC (turn the knob) than it is to dial in boost for EBCS (notice, I said BOOST control without regadrs to timing, fueling, etc.)
  
• MBCs respond a bit faster than EBCS
  
• MBC allows for better spool/response without the spike seen by a BCS setup that has an aggressive TD Proportional table.
  
• MBCs are adjustable on the fly
  
• MBCs bypass the ECU's ability for failsafe boost control
  
• MBCs may suffer from PTFB
  
• MBCs do not allow the ECU to compensate for altitude
  
• MBCs do not allow the ECU to compensate for temperature
  
• MBCs do not allow for a boost taper in the upper RPMs *
  

I put a * on that last one because it requires a bit more explanation.

"Why do you want a boost taper?" The answer is simple: because requesting 18 PSI from a VF40 at redline is not realistic. Above 5000 RPM, the VF40 dives off a cliff and trying to push 18 PSI at that point drives the compressor way out of its efficiency zone. You could likely weld the wastegate shut and the turbo would not produce more than about 13-14 PSI at best.

Let's say your turbo produced 18 PSI at engine speed 3KRPM and the turbine had to be spun at 100KRPM. Let's say now that your turbo produced 11 PSI at engine speed 6.5KRPM and the turbine had to be spun at 150KRPM. You are producing fully 7 PSI less, but the turbine is being driven fully 50% faster.

If you knew this and had an EBCS, you would dial in the WGDC appropriately at redline to create a taper and only target about 11 PSI.

With an MBC, you'd have no such control. The MBC would keep the WG shut still and drive the turbo harder. Instead of 150KRPM at redline, the MBC may make the turbine spin at 250KRPM to eek out 13 PSI.... a whole 2 PSI more than the EBCS. But the goal isn't to produce boost. The goal is to produce USEFUL boost. At those speeds, the turbo is acting like a flamethrower and superheating the air charge before sending it to your engine. Completely counterproductive and just flat out bad for your turbo.

With larger turbos, this is less of an issue because they are capable of maintaining higher levels of boost even at redline without becoming flamethrowers, but the VF40 is a TINY turbo.

Thanks for the welcome...and I'll not deny I agree with everything you pointed out. As silly as that sounds I guess you pointed out why already in your response. I used a Hallman on all the bigger turbo set ups I've done, 20g and larger. My above mentioned wrx was an ej207 with a 3076 .82a/r so I accept your point of view and honestly use the oe solenoid on my gt just revamped to make 17lbs at peak torque the have duty cycles fall off till I'm at around 12lbs at redline. I do still love the simplicity of a mbc but I guess for 95% of these guys some form of electronic control would be better.

And thanks for being kind lol I'd really still like to here what the op says about his launch control issues.

Trey

Uh...

Thanks for the replies guys.

Back to topic now?

Will the rich condition caused by a bov mess up Cobb's launch control?

I wouldn't think that a rich condition would mess with launch control. I would think what would happen with a rich condition is your legacy would just become a massive flame thrower. The engine wouldn't get bogged down by the rich condition necessarily as it is still firing it will just push any unburnt fuel out the exhaust ports. Like it has been said above I think you need to raise what your rpm limit is. I'm able to launch my wagon on gravel at 3000 rpm as there is less traction so its able to launch easily but on pavement I need 5000 or more depending on the pavement condition. That way when you come off the clutch your throttle is high enough that the rpm will drop to max torque and you will be able to get going.

BTW what part of the Bay Area are you in?

I am located in the east bay. 925.

If you're close you should come to our weekly car meet on thursdays.

I think the second time I launched I had it set at 4900rpms.

Road was pavement in good condition.

The first time when the RPMs were a little lower it was on shitty conditon pavement.

Like I said I've used LC successfully before.

I guess since no one else has experienced this I got some more testing to do.

Because it makes super cool noises and throws hella sick flames.

There really isn't much of a reason to run vta other than noises and to get flames in between shifts. The hybrids are best IMO. Honestly, my throttle response is up and my turbo lag between shifts is down.