Power FC - Confusing boost reading
 

Hi,
I'm still learning about my new FD (purchased recently). It has a Power FC standalone. I use it to monitor lots of things, which is very helpful, but the boost reading is very confusing. It reads mmHg instead of PSI. I did several pulls in several gears and can't seem to get higher than +0.32 mmHg.

According to several conversion calculators, that's only .006 PSI. What? The previous owner told me the PFC's current tune is for 12 psi. Am I missing something? I do feel some turbo kick, but it feels pretty weak. I expected it to feel at least somewhat similar to my stock mk4 Supra's turbo kick.

- seemingly no boost in 1st gear
- boost feels like it kicks a little bit in 2nd gear
- finally feels like there are turbos in 3rd gear (but still very weak)

- haven't tried 4th or 5th gear pulls


Any thoughts? Thanks!

Did several more pulls last night all the way to near redline but only managed to hit +0.43 mmHg. No real progress here.

you have checker the vacum sistem? all pipes?maybe you have a leak.and dont make boost

Does it feel like it did when you initially test drove the car?

Haven't checked yet... still new to the FD. I'll look at that as I learn more.



It feels exactly the same. I wasn't very impressed with the boost during the initial test drive, but I also didn't know what to expect cause it was also my very first FD experience.

my car its same.put i tink i have the same problem,but my gearbox is auto...i dont no its normal or not..:(

I just rode in another FD with a PFC. His mechanical boost gauge read around 15-16 psi while his PFC read no more than +.85 mmHg. Does this seem accurate to any of you?

mmHg is typically a measurement of vacuum.

On your commander, vacuum is reported in mmHg, but boost is reported in kg/cm2

You still have a problem - but hey, you're making boost.

You have some boost, sounds like about 6-7psi when you get to high revs.

Check your wastegate isnt stuck open.

Check all inlet manifold piping, you could have a split pipe join or intercooler pipe.

Check all vaccum lines are intact.

You would be surprised how much a small hole can effect how much boost you get. I left a 2mm vaccum hose off and I couldn't make even half full boost (on a 450RWHP FD running 24psi)

It's very possible that the issue is something simple, and as a rule of thumb it's always best to rule out the most simple possibilities first. There is a load of piping to look over, but I would start at the intake and inspect all the way to the intercooler, and then to the manifold. As other forum members have stated, move to vacuum leaks and so on from there, but from my understanding these things are often simple leaks that can be replaced with more durable aftermarket options. GL

I'm not 100% familiar with the PFC yet as its on my future purchase list, but does if let you monitor only vac, and monitor only boost by selecting what one you want to watch? On a typical mechanical boost gauge, it has the mmHg reading negative, then there is the "0" mark, then after that its reading PSI (boost). So you've got 2 gauges in one and it literally just reads what ever is going on in the intake mani. What I'm wondering if on the PFC, does it let you select to only read mmHg to say diagnose or monitor vac to use a tool to spot potential leaks at idle and will not automatically switch over to reading boost until the user actually goes in and selects to read PSI? As I said I've never used one before, but taking a guess sometimes the digital read out devices will literally only let you read exactly what you've chosen... so maybe try and see if you can select "Boost" or "PSI" to read and it will read your actual boost.

Update:
My mechanic found that turbo #2 wasn't coming online and that it was leaking oil pretty badly. Long & expensive story short, the turbos had to get rebuilt.

That explains the sluggish feel at higher RPMs plus low boost readings. But reading the PFC is still confusing anyway. Couple other things still need to be done, but I should have my FD back in a week or two. Thanks!

my pfc reads .74 but gauge shows 12-13 with second turbo online. im really starting to not like the pfc commander. wish it was in psi and F for temp.

Yeah- that'd be so nice. No idea how to accurately convert the mmHg readings.

I'm sorry to hear that , But long and expensive I dont know . stock FD turbos are dime a dozen , and if you went with upgraded twins . well thats the only reason I can see it being expensive .

Stock FD turbos Good (used) ones sell for 250 all day long .

concidering howmany of them there are out there I dont think tis worth rebuilding

as for the boost even if your secondary turbo wasnt working . your primary should of still been building boost during the first 4k rpms . and you should reach target boost easily . with only the primary .

there is more to this than a leaky turbo .

was there nothing else he found ? is the mechanic a specialist with FD's ? or is he just some guy

He's a specialist (builds rotaries and sends them all over the place). After the turbo rebuild, the leaks are gone. I have no way to determine what's a "good-used" turbo, and since mine came out at only 39k miles, I have a really hard time trusting that any used set would come from a doner with equal or lower mileage. Also, stock twins don't seem to be as abundant and cheap as you make them sound. But in any case, I went for the rebuild for better longevity-- didn't want to take any risks with a used set.

As far as boost: Yes, I can feel turbo 1 coming on, but the PFC doesn't really tell me anything meaningful (no boost gauge yet). So just based on the butt-gauge, it didn't feel like much at all.

the PFC will tell you howmuch boost you were making and the max boost it made infact .

lol I can go on craigslist and find them for very cheap I know of a few rotary shops that have them on shelves I understand you not trusting them . but they just aren't worth the price to rebuild them howmuch did he charge you if I may ask ? BNR has the upgraded twins for 2800 I believe . you send them your twins they upgrade them .


but to each their own! good luck!

as 7dust said the boost is in Kgcm^ and vacuum is in mmHg with the PFC, which .32 is equal to 4.5psi. so yes you have some boost issues to resolve.

use this to convert the boost in the powerFC to psi:
http://convert-to.com/conversion/pre...m2-to-psi.html

another easy way is to simply take the number and multiply it by 14.22 to convert it into psi, or 14.3 as i do(err toward more than less when boost and fuel is concerned).