Overboosting after BPV ...?

[nas711]

Hi all,

I getting a dyno tune in a weeks time to have a look at this issue, but thought I might post it to see if anyone else had the same experience. Ever since (I think) I replaced my BPV from stock to FORGE V1 (did not retune), my boost levels have increased about 2psi. Thought I would check this in, so they put it on the dyno and it didn't make it through a run and claimed to be "overboosting" with a CEL on the accessport (only has done this on the dyno though, I cannot replicate it on the street). Requested to book it back in and retune to correct issue as we ran out of daylight.

Any one else had this issue before? Could my old BPV have been leaky and the forge one corrected it and has taken it past the boost maps set by the old tune? My tune before BPV was max at 20 and now it goes to about 22.5 at WOT in 4th. I am just driving it under 21psi in the mean time to be safe. Spring etc is perfect as it vents nicely.

Also...Tuned in summer temps and now averaging about 10 degrees...VIC for the win lol

Thoughts? Thanks.

Edit: Now to think of it, I also added the custom CBE exhaust to it. However, I got them to totally remove any factory piping and ran a 3" mandrel bend SS from 3" COBB dump (with new 3" flange) straight to magnaflow muffler. So from 2 1/4 up to 3" change ...could this affect it also?

[SarcasticOne]

If you've got an unlocked map, just drop waste gate by about 5%...

[Lachlan]

Also be careful till you figure it out. 22.5 psi is the limit of the stock 2.5 bar MAP sensor. If you see 22.5, you could be boosting 30+psi for all you know.

[nas711]

Yeah I am, was just seeing if I could replicate the dyno on the street. I gave it a bit in 3rd and it slowly crept up to 22.3 and held. I check my codes and no repeat codes, so its not overboosting (or not catching it anyway). I have the feeling it has only over boosted once, and that was on the dyno where it was pushed to its limits. When I drive it normal/hardish, it sit at a max of 20. 22.3 was only when I went balls out for a tiny bit to see what I could spin it up to and see if I could trip a CEL.

Wednesday it is going it for a dyno/retune and a 3 bar MAP and 3 port EBC.

Question : If it is overboosting, I should get boost cut as it did on dyno? What does boost cut feel like? Because the car just drives amazingly...nothing that feels remotely like a power cut. Max airflow I can get it to is like 260 also...not exactly what id call high.

[nas711]

Also be careful till you figure it out. 22.5 psi is the limit of the stock 2.5 bar MAP sensor. If you see 22.5, you could be boosting 30+psi for all you know.

If the stock is 22.5, why did it spike to 22.8 on dyno (boost cut)?

... I have read 23psi is read by 2.5 bar and I have never hit 23psi.

But yeah...I am aiming to not go near the 22psi. Stick at 20 max then I know I am in the safe range!

[Lachlan]

If the stock is 22.5, why did it spike to 22.8 on dyno (boost cut)?

Margins of error I think. 2.5 bar (= 36.3 psi) - atmospheric pressure (14.7 psi at sea level, different at altitude) = boost pressure (21.6 psi). I also assume that 22.5 isn't exact, maybe it's 2.59 bar (boost of 22.8psi). Point is, 22.5 is very close to the max and you can't really tell when it's maxing out, it will just stop reading any higher.

[SarcasticOne]

The dyno operator might have teed the boost line and read it there...
Also, boost cut is violent, you'd know if you hit it, almost like running into thick mud...
Quick question, were you tuned on a really hot day? If so, could explain it...

[nas711]

Ahh ok then, well definately not hitting boost cut on the road then. Just a smooth powerband in what ever psi. Only hit the high boost on the road a few times really, i'll be honest, I am not sure I actually have hit this cars redline yet, I find the torque is so instant I can get great pulls between 3-4.5 and I am happy, any more and I am wayyy over the speed limit.

Yeah I was initially tuned in February....probably around 32 degrees. Today is is mild, so I noted on my commute to work I could crack no more than 19psi getting under it a bit (not complete balls out), but say on a colder day last week I could easily crack 21 without trying. Lets say in theory there is a 20 degree temperature difference down here between when I tuned it and now.

[SarcasticOne]

Yeah, depending on how you're tuned, that could be your issue...
Here in Canberra my car was tuned in winter (3-6* usually) and struggles a bit in summer to hit targets, so I made my own tune

[Lachlan]

Lol, 4th gear logs at 6600rpm are...interesting. You'll have to redo all your WGDC tables for the 3-port anyway, so that should fix it if it's just the cold weather. You should also be able to hold boost more consistently after you install it too. For future safety (with your new big turbo) maybe look into the guardian angel?

[nas711]

Lol, 4th gear logs at 6600rpm are...interesting. You'll have to redo all your WGDC tables for the 3-port anyway, so that should fix it if it's just the cold weather. You should also be able to hold boost more consistently after you install it too. For future safety (with your new big turbo) maybe look into the guardian angel?

So the three port ebc doesn't cap boost levels at what you set it at. I don't really know the tech behind it, but I thought they locked boost and wouldn't allow any shift really, unlike standard controller. Is the guardian angel a total boost cut past set targets...so say if you set it at 22psi, it will NEVER get past 22psi regardless of what happens? Will it basically shut down car fueling etc to stop detonation?

I though the mazda ecu cut boost etc, as it showed up in my CEL code as it did its job. Is it not consistent and the guardian angel is better?

[Lachlan]

Nope, that's a manual controller you are thinking of (not what you want, as you want to control boost through the rpm range, not just x psi all the time).

Took me ages to figure them out, so I'll try to summarise. Lol
3 port works similar to the stock 2 port. They both control how much boost pressure goes to the wastegate to compress it's spring and make it open (ergo lower boost pressure).

2 port has a line straight from turbo to WG and 'bleeds' pressure to control how much boost gets to the WG (aka bleed mode). If the spring takes 10 psi to open, and you want to run 15psi, the 2 port tries to bleed off 5psi to keep the spring from compressing and keep the WG closed.

Obviously, the little 2 port can only bleed so much before it maxes out (100% WGDC) and can't increase boost anymore. eg if you want to run 21psi, the 2 port would need to bleed 11psi of that 21 to keep the 10psi spring from opening the WG. If it can only bleed 10, not 11, your WG will open at 20psi and you won't be able to reach 21psi.to fix this, you need either a bigger 2 port or a different method. Enter the 3 port...

A 3 port can actually cut the line completely (aka interrupt mode) so that no boost goes to the WG, allowing the the spring to remain untouched and the WG to stay shut completely. This increases your boost. Your ecu uses duty cycle (series of on-off-on-off signals) to control how much either EBCS opens to either bleed or cut pressure to the WG.

A 3 port just cuts the line completely when the ecu duty cycle says 'on' so it will work on higher boost and needs less WGDC to do the same job, letting you raise the boost to meet targets.

Hopefully that wasn't all jibberish.

Yes, the Guardian works at a certain boost pressure, kind of like a circuit breaker or fuse. It just opens the BPV at x psi to save your engine, until boost drops below the limit. Eg you target 20psi, so you set the GA to 22psi so if you ever over boost by more than 2 psi your BPV will open and dump boost till you are back below 22psi. Much less violent and horrible than the stock fuel and ignition cuts (you won't face-plant the steering wheel or get left on the wrong side of the road if you are trying to overtake someone) and acts faster. You can have a wastegate line pop off and it will save you from zoom zoom boom. It also flashes up a little 'numbskull' light to tell you something has gone wrong whenever it activates

This helps explain with pictures http://blog.perrinperformance.com/bo...lained-part-2/

Edited for clarity

[nas711]

Trip home ...21.1psi wgdc 97% ...?

[Lachlan]

Can you take a WOT log, even in 3rd?

[SarcasticOne]

Do you know how a waste gate works?
Think of wgdc as how much "effort" a waste gate goes to in order to stay closed...
A 2 port has a shorter "range" than a 3 port... For the reasons stated above...
So, with a 3 port you can reach more boost for the same amount of waste gate duty cycle

Edit: the ECU boost cut takes a second or so to kick in... Whilst the GA happens instantly...

[nas711]

Yeah I knew roughly about the wastegate part, but yes I am no expert. I don't want to WOT log it...ill leave it to my tunerbut thanks for the info on guardian angel sounds good!

[Lachlan]

Each to their own. Who's tuning you by the way?

[nas711]

Tuned by HPF in dandenong. I have been happy with their work. We have been meaning to tune it after the mods, but I live a bout 45 mins drive so it can be tricky to coordinate. It's also very wet here, so I don't think I should go out and test the limits of the engine in aquaplane weather haha

[nas711]

Well I officially don't know how the wdgc works as when I start the car up and drove in slowly down the road and drove normally...max boost probably about 8 ....wgdc was 98 lol. I have no clue. I thought depended on pressure of turbo and efficiency of wastegate i.e under huge boost, wgdc was high.

On another note, I have ordered a guardian angel v2 from edge today to put on with corksport. No rush putting it on with k04 as thats just a tuning issue...

[Lachlan]

Read that page I linked before, it explains it. It's a measure of how hard the ebcs is working to keep the WG closed. 0% is completely closed ebcs not bleeding any air and boost is just controlled by spring pressure. 100% is completely open bleeding off as much air as it possibly can to raise boost.
You have an AP. Take a log and have a look (doesn't have to be law breaking fast, even 2nd gear to 80 or 100km would be fine and legal) and you will see how it works. Or just look at any other log posted on this site.