How do all of you guys tune your boost controllers? I've got mine peaking at ~23 psi in 3rd gear, but it spikes to about 24.5-25 in 5th. Do you guys tune off peaks in 5th? 3rd? 1st? Just checking to see what your methods are.

 

you can't really tune a mbc with nothing. you set it at what you want and thats it. but damn thats a rather large spike. i hade mine set to 22psi.. if you haven't experinced it already it will turn on a ses light.

 

I think 25psi is to high of a spike.

 

^^ yea thats overboosting

 

With a MBC, you can't really do anything after you set it, just like the rest are saying.

I edited my post. You got a X and I am sure it is not tuned yet. 25 psi un-tuned is a little hi. Turn it down a little bit.

 

mbc= no frills, but it does it's job. Wait for a reflash if you want precision.

 

Isn't having a mbc/ebc a good idea anyways when you tune/reflash?

 

No, I'm not asking how you tune it on a regular basis. I tuned my mbc based on readings from 3rd gear ~1500rpm on up. I'm asking what gear you guys tuned yours in. The last turbo car I had spiked in higher gears as well. It's usually when I'm in 5th and hit WOT at a lower rpm.

So should I be tuning off a situation that I hardly ever put my car in or should I tune off 3rd gear? Just to make it clear, it is NOT spiking in 1st through 3rd gear, and when it actually spikes in 5th it lasts for an instant (only see it on one update of the Zeitronix setup, which updates at least twice per second). This is not boost creep, and it is not holding 25psi for an extended amount of time.

 

The boost spike is a constant issue with MBC. Tuning the MBC in 3rd or 4th gear is ideal. With an EBC, I always tune in 3rd gear, then modify the DC for 4th and 5th gear to fix the over shoot. Since you arent hitting boost cut (26psi), its up to you how to deal with it. You could always turn it down, but then you lose peak boost in lower gears.

 

^^ Exactly the kind of answer I was looking for. Thanks PDX!

 

IMO, the above advice is at best dubious and potentially hazardous to the life of your engine. You should approach the issue of peak boost with extreme caution. Tuning for peak boost in an intermediate gear is only safe when there is no boost creep or boost spike in top gear.

You need more information than that provided by the dial face of your boost gauge. Is there any engine knock present at 25 PSI in 5th? Are your AFR's within the safe range? What octane gas are you running? Even the ambient air temps can impact significantly on your peakboost level. If the weather were to get colder all of a sudden then you'd be boosting a couple PSI higher still in top gear.

If you are hitting 25 PSI in 5th, then simply, your MBC is set at a 25 PSI peak. Proceed with caution on pump gas. If you want to run 23 PSI max then you'll just have to turn your MBC down a notch.

 

Without logging ignition timing numbers, AFR and knocksums, all of the answers fail.

 

I think everyone in here is reading too deep into this. All he wants to know if how he should set it because boost is different in each gear and at different loads. Theres 2 ways to set it. How you do it depends on how you drive:

1. If you like to lay onto it alot on the hwy in higher gears, then take the car up to like 30 mph, then put the car in 4th/5th gear and floor it. the car will boost up and overboost. Set it to 23 psi accordingly. But if you floor it in 1st, 2nd and go through the gears it will only be around 19-21 psi.

2. If you like to just go through the gears and you dont mind downshifting on the hwy to accelerate instead of just flooring it, you can set your mbc a little higher. This way you can set it at 23 psi in lets say, 2nd gear, but if you ever lay into it at a lower rpm in 4th, or 5th its gonna overboost

 

Some guys use mbc's with reflashes, but I've never understood why. MBC's are for mechanically adjusting boost, and aren't necessary or practical if the ecu has been tuned. As far as ebc's are concerned, they are better because they electronically adjust the boost, and some even let you adjust the boost depending on load and rpm to better control taper. However, if you reflash the ecu, then you are doing everything that the ebc coud do and a lot more. The ecu can be tuned to control the wastegate duty cycle mapping, the boost targets, boost gains, etc, and they are all adjusted for different rpms and load. A big thing also is that whenever the boost is adjusted, so too should the timing and air fuel ratios to be all balanced with one another, and this just isn't possible with an mbc or ebc alone. As I mentioned before, I am not sure why people use MBC's or EBCs with a reflash because if the car is properly tuned then it seems unnecessary and counter productive. When the wastegate duty cycle mapping is adjusted it is altering how the solenoids bleed off boost pressure to the wastegate actuator, and when using an mbc the solenoids are usually bypassed and the boost is adjusted on a pure mechanical basis with no electronic control. So, perhaps people that use this kind of setup just have the reflash control the other aspects of the ecu and let the mbc run the boost curve independently. Why someone would want to do this is beyond me, because the boost taper would be nowhere near as precise with this setup, but then again many people who modify their cars have no clue what they are doing.

 

You tune for the boost level you have set with the MBC. You don't boost with the MBC for the tune you have programmed in your ECU.

There is nothing wrong with MBCs. Some of the worlds fastest cars as well as some of the fastest Evo's for 2008 use manual controllers. Buschur loves them.