Peak Boost varies depending on ambient temperature?

[eric.marsh]

Im new to noticing this and I'm wondering if everyone experiences this? I live in a super hot and humid area. In the early morning or late at night when ambient temps are low, my car will hit 1.6 bar relentlessly. However when its hot ill only hit 1.2 bar. I expected the car to be sluggish when its hot out. But this is a dramatic change! I think I will be focusing on cooling for future upgrades.

 

[Alin]

[MENTION=1507]Spamby[/MENTION] [MENTION=662]Batmobile_Engage[/MENTION] [MENTION=652]Grinder34[/MENTION] [MENTION=1]IGOTASTi.COM[/MENTION] [MENTION=9]HolyCrapItsFast[/MENTION] [MENTION=3416]WRB_STi[/MENTION] [MENTION=1069]35r[/MENTION]

Colder air is denser. Im not sure exactly why but one of these fine gentlemen will tell you why denser air boosts higher.

 

[eric.marsh]

it makes sense, i guess i just wasnt expecting this big of a difference. I also spelled "varies" wrong lol.

 

[Alin]

it makes sense, i guess i just wasnt expecting this big of a difference. I also spelled "varies" wrong lol.

One of them will tell you how big the difference can get.

Also fixed it for you.

 

[Batmobile_Engage]

(For reference: 1.2 BAR = 17.4 psi, 1.6 BAR = 23.2 psi)

That seems like quite a big difference in peak boost levels due to ambient temperature alone. I feel like something might be wrong. What turbo do you have installed? My old IHI turbo developed the infamous hot side crack near the wastegate port. I would hit my target boost just fine until the car had been running for a while or driven hard. Once the turbine housing got hot enough, the crack would expand and my peak boost numbers would drop to ~14 psi (20 psi target).

@HolyCrapItsFast should be able to expand on this, but I'm pretty sure the stock MAF also takes temperature readings. I'd imagine that if the temps it's reading swing widely enough, the ECU could adjust some tune parameters which could explain this problem. Unfortunately, I don't know enough about tuning (or your setup) to make that call.

Between summer and winter temperatures ~80*F -to- ~10*F, I sometimes notice a difference of 1-2 psi; higher boost in the winter.

Also, try to measure your peak boost levels in 4th gear....or at least 1-4, not 5th or 6th. 5th or 6th can often overboost a bit because of the difference in load (and the tune was done primarily in 4th gear). For example, I hit 19 psi in gears 1-4 and ~21 psi in 5th and 6th.

 

[eric.marsh]

Thanks for the info dude,

I am running a stock EJ207 with a VF37 twin scroll turbo. Ive read that 1.5-1.6 bar is normal. The Okinawa is pretty harsh on vehicles to include the tempurature and humidity levels. My turbo, actuator or even boost solenoid may be on its way out. Or it could be just the weather taking its toll. Maybe this issue is linked with that vibration noise i posted a video of. For now I'm just babying her, i need to save up $ before anything brakes lol.

 

[Batmobile_Engage]

How are you measuring these boost levels? Cobb AP, boost gauge, etc.? Just curious. I know of people getting bad readings on gauges in the past.

 

[WRB_STi]

@Spamby @Batmobile_Engage @Grinder34 @IGOTASTi.COM @HolyCrapItsFast @WRB_STi @35r

Colder air is denser. Im not sure exactly why but one of these fine gentlemen will tell you why denser air boosts higher.

A short and easy way to explain this is cold air is denser (more molecules). When you force it through a turbo and it compresses the air, it will expand due to heat. Therefore; colder air will expand at a faster rate when compressed causing higher boost pressures. When the air is warmer, the intercooler is doing its job by keeping the air at a constant temperature with a less rate of expansion.

If you upgrade an intercooler, keep in mind that it will keep the colder air more dense (more oxygen) and you will need to add fuel. You can actually run lean from an efficient intercooler.

 

[eric.marsh]

I am only using the stock genome boost guage. It would be nice if access port worked for JDM. Life would be more simple that way.
As it stands im setting money aside for anything that breaks. Next upgrades will be rims and tires, Z2's or AD08R. Then air fuel guage and a tactrix cable for a tune.

^^ I would like a better top mount intercooler someday. However, I will need to do my research. I want to maintain the quick spool of stock turbo if not improve it.