Basically yesterday when it was around 40ish degrees outside, once my oem water temp gauge reached the middle I started boosting. I always look at my boost gauge whenever I boost, and for the first time ever after my recent vacuum hose job, im seeing 12.5-13 psi This only happened for a spit second since I let off the gas extremely fast.

Looking at my after market water temp gauge, I then waited for the temps to get around 170ish before I boosted again, and when that happened, the spike was gone, and I was back to normal 10 psi. I tried it again when I got home from work with temps outside about 30's, I did not boost at all until engine temps reached 170ish degrees, and everything was ok, and I was back to 10 psi like normal. Now that I know this, im NEVER boosting again with engine temps below 170 degrees EVEN if my oem gauge shows the middle.

I just finished a major vacuum hose job a few months ago, so i'm finding these things out for the first time. My car is basically stock (aka my sig)

Question is: Why would my boost spike only when engine temps are below 170ish degrees, even though the oem gauge shows fully warm (aka the middle)

 

my question is why are you boosting your motor colder then fully warmed up (180-195) and sorry but i dont know the awnser.. maybe a goodfellafd3s could chime in~

 

I think you should pm arghx. He knows alot about fuel/air mixture at certain rpms etc. He could help you for sure. Also I heard boosting on a cold engine is terrible for coolant seals.

 

It is most likely the lower intake temps (because the engine bay itself hasn't fully warmed up) that is contributing to additional boost. There may also be some logic in the factory ECU contributing, we just don't understand it.

Are you running a stock exhaust system and stock intake system?

 

My personal experience with spike was that it is unpredictable. Essentially identical conditions on the same car and same load didn't always result in spike...or the lack of it. I guess that's why they invented BCs.

 

12-13 psi at low rpm isn't going to hurt anything.

 

My experience as well. For that reason, I bought a Greddy Profec Type S ebc. It does a better job of controlling boost than the stock solenoid. Having a cat also helps control creep and spike.

 

170 is fine...In the UK mine didn't ever go above 170 unless I sat in traffic....

This was the first winter for my new boost controller...It took a WOT pull to adjust for the cold temps & now its fine.

 

boost spikes aren't uncommon prior to warming the car up fully.

this just shows how bad the stock coolant temp gauge is, it will sit in the middle range from 170-225*F before moving to the next step prior to overheating. so, boosting when the gauge just starts to move isn't a great idea, but as said, 13psi in the middle of the RPM range isn't generally going to cause any issues.

cold ambient air, cold intercooler, cold intake pipes and cold turbos = a few psi of additional boost. for safety, just make sure it's warmed up.

 

Yes I have both stock exhaust with both cats still on, but the mid cat is a high flow metallic substrate. The intake system is 100% stock, just a few silicone couplers. Thanks, that was the answer I was looking for. I never boost until the car is fully warm anyway, but the difference between the aftermarket gauge showing fully warm and the oem gauge showing fully warm is a BIG difference, and thats gonna help me in the future.

I've read a thread somewhere that the stock ecu can properly adjust the fuel mixture for boost up to 12ish psi max, before you would be considered running lean, is that right?

 

Before I realized my wastegate nipple was accidentally left uncapped, I was having crazy boost spikes. Which would cause fuel cut bucking as I was entering the high rpms. I sometimes saw a crazy number like 18psi!!! I am so lucky nothing happened.

That being said, accidental spikes are sometimes forgiven, depending on car it seems.

 

I doubt you'd have much of a spike if you had the factory converter installed. If you are really worried about the engine you can install a wideband o2 to monitor AFR. I'm sure it's fine though. There are many people who have run a setup similar to yours for years with no problems.

 

So you know you can get spike with a cold intake tract and possibly because the car isn't completely warm. That suggests to me that with a cool ambient temp, you can get spike too....stock intake or not. So what happens on a particularly cool morning or evening?
Just get a BC.

 

Ive noticed that it really doesn't matter how cold the ambient temperature is, the car will never spike if its fully warmed up. The only time it ever spikes, is when coolant temps are below 170 degrees during warm up, and of course in freezing weather it would spike more.

Im guessing this might be due to the high flow mid cat. That's the only modification that would possibly cause that being that everything else is 100% stock, including the pre-cat. I will never depend on the oem water temp gauge again lol

18 psi???

 

Yeah 18psi lol. I could never really stay "in it" so i never had the chance to let the engine **** itself up. Everytime i get into boost, it would stutter and i would back off. Nevertheless im sure i still could have destroyed it but im glad nothing happened.

Capped off the wastegate and now i just the boost off my BC. Now i get a solid 10psi.


Yeah water temp and boost gauge were my first mods. Then i added in the HKS DP later on. I still have the stock cat though but its getting old, i have another lower mileage cat sitting in my shed. I still gotta install that lol