BNR S4 - Can not pass 24-25psi? Boost Issue...

Hello All,

I recently ran into an issue with not being able to get boost past 24-25psi on my BNR S4 tune.

I am not quiet sure what the issue is so I wanted to reach out to see if anyone else had the same issue or saw something in my logs that looked familiar. I fixed an exhaust leak and have tightened down all hose clamps to make sure it wasn't something easy to fix but the issue still persists. I have a fully forged engine so it can handle the power. I also run a 3 port EBC and 3 BAR MAP and can upgrade to a 3.5 BAR, I just need to install it.

A little background, when doing my first logs on the set up I hit 16-16.5 PSI with 0 WGDC. (Log attached)

If you look at the attached logs you will see my PSI reach 24psi at 70 WGDC and it can't get any more boost even when the WGDC is at 99-100, which should not be the case from what I have seen BNR S4's give out.

If you can help, please chime in.

Forgot to add I am spraying meth through a D014 nozzle and the g/s for the MAF has been adjusted to compensate for the extra fuel.

 

More mods list...?

 

I have an S4v2 and it has no trouble at all hitting upwards of 30psi. You most likely have a boost leak.
[doublepost=1508077330][/doublepost](In an effort to deliver thorough information):

you can make your own boost leak tester for about $10. Pick up a tire valve from your local tire shop (bolt in ones cooperate the best but not absolutely necessary. Spend the extra dollar), then make a trip to your local home improvement store. Grab a coupler that has one end the same size as your intake. The other end can be whatever you want it to be, but 2" seems to work well. With coupler in hand, go get a PVC end cap that fits snugly inside the end that will not be going on the intake. Get hose clamps for both ends. Take the whole lot home and drill a hole in the end cap for the valve to fit through. Install the valve into the end cap, RTV for good measure. put a dab of rtv around the cap and clamp it into the end of the coupler. You now have a simple boost leak tester. You generally pull the MAF housing off and test from there but hey, I was a cowboy and hooked mine up pre maf and found I had a bad o-ring on my maf sensor. If you don`t have a compressor, with a little practice you can get the tester on and off in barely a minute. Go to QuickTrip and use the free one there. Sometimes they`re elusive so have a spray bottle with soapy water in it to assist if need be. Took me 45 minutes to find a leak in my system (which is a story unto itself and best served another day)

 

It could also be a clogged cat if you have a catted downpipe.

 

Mod List:
- Manley Rods
- Speed performance custom pistons
- L11 Head studs
- BNR S4
- XS Power V3 Exhaust Manifold
- ATP 3" Catted Downpipe
- Custom 3" exhaust
- HDI FMIC
- 3.5" Aluminium JBR intake
- Snow performance Stage 2 MAF Meth (D014 nozzle)
- CP-e Stage 1 Clutch
- Speed performance transfer case caps
- CP-e rear diff mount + SURE front diff mount
- Damond stage 3 OCC's with PCV plate
- Techna-fit SS clutch line
- DSS Axles

If it was a boost leak wouldn't I see some weird AFR? I was thinking it was the preload on the waste gate not being enough so it's never shutting all the way.

Edit: I should mention I have hit 26psi but never held it above 4500 rpm. I spike to it but then it comes down to 24.

 

Generally a boost leak can go undetected under normal driving circumstances, its vacuum leaks that's cause weird afrs. I would check with a boost leak test first since they're pretty easy, then move on to other options if no leak is present.

 

I agree with that but I was was thinking if there was a boost leak I would see weird AFR because of the metered air escaping. I would think with a boost leak I would be running a little rich above 24psi. I will get it tested just to be sure it's not a boost leak.

 

What's your target AFR?

 

WOT AFR is 11.8

There is some fine tuning in the MAF curve to be done still, as I get very repeatable AFR's on WOT pulls.

 

So what should you be expecting boost wise? Like how short are you falling? If it's a small boost leak that would definitely go unnoticed.

 

I can`t get to excel files from here so I can`t see the logs but also look for anomalies in the throttle position values. It`s not probable but definitely possible that if you`re hitting your load targets you`re getting throttle cut but not the accompanying cut in wgdc. Who`s tuning it?

 

Rob - Hypnotic is tuning it and he said it may be the preload. He hasn't advised on anything yet so I am waiting on him to get back to me.

Not sure what this revision was targeting but it seemed weird that I needed 100 WGDC to get 24psi approaching redline. Especially when others have been getting well above that boost on the BNR S4.

 

Got a look at the first log. Nothing out of the ordinary other than wgdc. Where are you in the tune process? IE, how many revisions since the base map? Which Gen of car? Also, log vehicle speed instead of coolant temp.

You can definitely try putting a turn of preload on it. It won`t hurt anything and you can do it in ten minutes from under the car ( it can be done from the top but it`s WAY easier from the bottom).

 

We just got the the stage of the tuning process where AUX fueling has been accounted for & additional boost has been added.
Basically, we are trying to top out the AUX fueling I have with the turbo with a safety zone being accounted for but I can't increase boost.
I would think we are 2-3 revisions out from being done once we hit boost targets now that AFR's are settled.

Mazdaspeed 6 2007 and it has all the mods to hold 500 whp. The only thing holding me back is not being able to get above 25psi.

 

Nice. It'll come close, for sure. The awd eats up more hp and the original S4 tops out around 470 on a Speed 3 but it'll definitely rip. Pretty similar setup to mine. Leave the oem intake manifold and crank up the torque and let that awd do what it was designed to do!

And given that it's a 6, disregard what I said about adjusting the preload from the bottom. Lol.

 

Good luck with getting that nailed down.
I was having an issue with a leak because a I wasn't getting a good enough seal on my boost tubes nor my TIP and I had a bolt from my DP come unthreaded and backed off. Thankfully I had a replacement. I think I was also battling a dirty fuel system that needed cleaning - 160K miles

 

I am going to buy some C-clips today and try and add some preload to the waste gate when I get home from work.
2 additional turns seems like a good starting point but I'll see if Rob responds during the day with his recommendation.

I had my injectors cleaned and new screens installed by Precisionline Fuel Injectors before I did this build. The only dirty part that went on the car was a intake manifold which gummed up my MAP sensor once I sprayed meth lol... had to use some sensor cleaner to make it work properly.

I'll post my results, but if anyone else has input let me know.
[doublepost=1508188129][/doublepost]Added two turns on the waste gate, managed to not lose or fumble to E-clip... not sure how I finessed that.

Going to do some logs tomorrow at lunch. Tightened down any hose clamps I had access to, without over doing it and stripping threads.

 

Assuming no leaks, I can almost guarantee the problem is the catalytic converter. Punch it out and the problem should be solved.

Where was the exhaust leak that you had?

 

You think a High Flow Catt from ATP is the problem? Do you know this from experience?

The leak was at the turbo and exhaust manifold flange. Warped exhaust manifold flange meant a lot of gas was escaping and not spooling the turbo + throwing off AFR's.

 

I had the same problem with this manifold, which is installed on my current car. Did you have it milled? How did you fix it?

No experience with ATP high flow cats clogging, but seen it plenty with other brands. Catalytic converters are not a good thing to have installed on these cars, especially low quality ones like those found on most catted downpipes sold for this platform.