I wanted to see if anyone's Scangauge reads boost at a lower level. I have a vacuum boost gauge setup. The Scangauge reads almost 5psi lower than the mechanical boost gauge. I have the boost gauge setup per the NM boost tap.

I am going to get a dyno tomorrow morning to check actual AFR and Temps but wanted to see if anyone else has had this issue since i have an issue when rolling on the throttle and boost only hitting 14psi and then if i get off the throttle and back on fully then i hit full boost around 19psi. It doesn't do it all of the time but sucks if i want to roll into boost with out stomping the throttle from 0-100% right away.

Ex. Mechanical Boost Gauge reads: 19psi
Scangauge II reads: 14.7


Car: 2007 MCS
Engine Mods: AEM intake, DNA\Battle Stage 3 tune, CNT 200cel DP, Invida exhaust, Helix FMIC.

 

I can't help with the boost gauge, but I too am running Battle/DNA stage 3. I have the DashCommand App on my phone, I'll do some monitoring of my PSI in those two different scenarios. The last two runs I had were around 17.5 and 16.8psi (20 degree ambient temp difference between those runs). So I'll try out the rolling-WOT scenario and the 0-WOT scenario and see what kind of difference I have.

 

Have you adjusted your SG to offset for elevation? I think it is the last 2 or 4 numbers in the Xgauge configuration for boost.

 

-Thanks Grizld

-05r50 I will check the settings. I am in ohio as well thanks.

I will post the dyno results tomorrow after i get them. I am wanting to upgrade the turbo so just seeing what i am at now.

 

When the engine is off it is showing 0 for boost. When idling the Scangauge boost shows around -7 to -8 but the mechanical vacuum gauge shows -15 to -17.

 

Ok. Back from my lunch/data logging break. I did a couple pulls. I was in 4th gear; starting at 3kRPM; 55mph; Ambient Temps 74*F; Humidity 71%; Elevation ~810ft. On a flat road I did a slow throttle push, about 3-4 seconds to get to full throttle. I got 12.8psi . I thought I was running stage 3!? But maybe thats what my conditions called for? I also did the 0-100% throttle scenario. I got 15.67psi the first time. 16.08psi the second time. Still sounding low to me, but again maybe thats what my conditions called for?

No idea if that helped or not, but thats what I got today.

 

does your tune remove the gear based boost limits that supposedly exist? i know the stock ECU is supposed to limit the amount of boost in 1st and 6th, and i we all know it balances a lot of variables to determine peak boost.

what brand of gauge? its safe to say your computer is at least basing all its calculations off of what the scan gauge is reading from the ECU.

 

Thanks for checking this out. This is the type of readings that i see when rolling into it. So im wondering if some safeguard is in place or just how the tune is.

 

I'm using a vacuum Boost gauge and the Scan gauge. But my scan gauge reads around 5psi lower under boost than my vacuum gauge and when the car is off both read 0psi.

 

you didn't answer what brand of gauge. there is a big difference in accuracy between a $20 vato zone and $100 auto meter...

 

I have an Marshall Instruments boost gauge.

 

The Scangauge is actually reading a modified MAP sensor signal. It will read 1/2 of what vacuum is, and be pretty accurate under boost pressure. If it were me, I'd hook the mechanical boost gauge to a known pressure source and check it's accuracy first, before worrying about the car. You could use a Mityvac tool, a compressor with a outlet regulator, a cylinder leak down tester...

 

I will try an auto meter brand gauge i have after my dyno today. But i also see the change with the scangauge when the boost gauge shows 14-15psi the scangauge is showing 11psi. And then when boost gauge shows 18-19psi scangauge shows 14-15. I have the Battle\DNA stage 3 tune so i wouldn't think 14-15 is max boost.

So rolling into full throttle and then going to full throttle is where i see the lower boost to redline 11psi(scangauge)14psi(boost gauge) most of the time. But if just stomping on it from 0-100% throttle i can get full boost 14-15psi(scangauge) 18-19(boost gauge).


Also Grizld700 did a test at lunch yesterday and saw something similar.

 

Still searching to see if anyone has a scangauge II and a mechanical boost gauge to see if their scangauge reads lower than their mechanical.

Ex.

Scangauge II 14psi
Mechanical 19psi


I have ordered a BT OBD II so i can check that as well before chasing down if i have an issue with boost since it seems to vary if i get full boost all the time or if something is limiting the boost.

some times i hit 14psi and sometimes 19psi (mechanical and subtract 4-5psi for the Scangauge).

thanks!!!!

 

Did you get you Scangauge from WayMotorWorks? If not, it may not be perfectly set up for the MINI. Also after doing some research I've found out that out-of-the-box the Scangauge II displays absolute pressure. You can program it to show actual pressure. If you haven't already done this, then I would say thats your problem. If you have, then I'm at drawing board again.

 

I bought this one directly from Scangauge with the MINI configuration. This one shows the FPR,BST,EOT and a few others. When the car is off and IGN is on the BST shows 0. Guess what im wanting to know is what others see at idle and WOT on the Scangauge. Since im seeing only 16.7 max with a stage 3 battle tune but the mechanical gauge shows 18-19psi.

 

i don't have a mechanical gauge, but i should be getting my updated Scangauge back from programming pretty soon. I'll let you know what it displays at idle and such.

You do know that peak boost allowed by the ECU is controlled by many factors such as water temp, intake temp, engine load etc right? Doesn't explain the discrepancy between the gauges, but can explain why you see different "peak" boosts. For instance on a cold morning rolling onto an onramp for the first time you will probably see higher peak boost than if you did the same thing on a 110* day when the car's been running for an hour.

Battle would be able to tell you better how their tuning specifically affects this, but when I was talking to them about getting my car tuned, they sounded pretty confident that they weren't going outside factory parameters for peak boost, just controlling when/how it rolls on and tweaking the fuel/timing maps.

My guess would be just differences between calibrations on the 2 gauges. I have a feeling the Scangauge is more accurate, and probably the relevant one to go off of since that is what is being fed into your ECU.

 

Thanks for checking this out when you can..

But that's the just the thing i see lower boost when its colder out for the first few pulls (only 14-16psi. Outside temp:50f Car temp:180f) then after getting off and back on then i will get 19psi. I have even taken off my DP and checked the wastegate on the turbo. My MCS has 43k on it and not leaks and runs great so im wondering if its something to do with the tune. I have explained what im experiencing to them but nothing really stands out and the dyno looks good.

Here is a video of what my wastegate looked like yesterday and i adjustedthe actuator set nuts to the wastegate flap so that it pulls it a little tighter when closed. And it seemed to make some difference on the run i did right after but this morning still the inconsistency of 14psi-19psi on pulls. Only other thing i have read like this is when ppl were running AP tunes. So not sure if i should get another tune but really would hate to throw away the money i have with this tune.


WasteGate internals