I would assume that's low. It's about 20*F outside.
Potential Causes of Overboosting
- Thread starter Batmobile_Engage
- Start date
you have a ram or cai?
Ram. However, my MAF is in a blow-thru configuration, post IC core.
interesting. i have a similar configuration but i was getting iat's of 70-72 with outside temp of 65...i guess youll have to see what it looks like when its hot outside this summer...
Hmmm...another thing I need to check when my AP comes back from Cobb. My header is all wrapped up, can't imagine its transferring a lot of heat. Man, I better start making a check list. :lol:
Mind blown. I can't believe I didn't know about this before. Anyway, I managed a couple good runs on the way home. First run was getting on the highway in 4th gear. For once, there was no one around, so I was at ~4,000 rpms when I put the hammer down. Boost went up to 20 for a split second and then settled at 19psi. I ran it up to ~6500 and went into 5th WOT. In 5th, I was still showing about 22psi so I lifted. As I turned down my road, I stood on it in 2nd gear and only hit 19psi.
How did I not know this before?! Damn, I feel kind of dumb today.
How did I not know this before?! Damn, I feel kind of dumb today.
lol told ya 
Grinder34
Track Monkey
So i believe everything you say about the ecu and tunes when its hot, but it just blows my mind. I know there are like 100-dimensional lookup tables, but wtf, one of them cant be an "oh shit, the boost is too high. lets open the wastegate just a smidge and adjust everything else accordingly" even in closed loop operation.
In a similar vein.... I know that original tuning is done with a bunch more sensors than are included on a production car (widebands right at the exit to the cylinders and egt probes for example).... But for the most part, all the tuning that people do on dynos is based on a set procedure and logic. I dont understand why cant be coded into the ECU more. Especially aftermarket ones that can be hooked up to egts, widebands, etc....
In a similar vein.... I know that original tuning is done with a bunch more sensors than are included on a production car (widebands right at the exit to the cylinders and egt probes for example).... But for the most part, all the tuning that people do on dynos is based on a set procedure and logic. I dont understand why cant be coded into the ECU more. Especially aftermarket ones that can be hooked up to egts, widebands, etc....
That's what I thought!!! I figured the factory boost control system would open the wastegate a little bit and even out the boost to match the target.
How are more people NOT blowing up motors from this?
There are a number of explanations here that we can talk about and consider and i understand that we want to know the answers to everything, but simply put, thats the logic subaru engineers chose to calibrate the with in the first place and its not meant to be tampered with. Thats why aftermarket parts void the warranty and it takes a bit of know how to keep everything in check. Not every tuner tunes the same and not all parts or even the same parts will always net the same results especially when you take into consideration the external factors such as elevation and weather. that's just the way it is. that is why aftermarket parts such as 3 port ebc's and manual boost controllers are available for us to use making our lives and the tuner's lives easier. so all you can do is take it for what it is and figure out what you want to do from there. Bottom line is the stock turbo is so small and responsive that people get caught up in wanting the boost and are too lazy or complacent to downshift. which is understandable. so to avoid this if you want to accelerate and boost just downshift. The reason why overboosting in the longer gears is so likely to happen is because as your pushing the gas pedal to the floor your telling the ecu hurry up and accelerate and since it cant do that because you are in a longer gear the TD is trying to adjust accordingly to compensate for the longer gear acceleration which isnt what it is designed to do in the first place and that is where you get your overboost. You can combat this action by lowering the duty cycles but now you are moving into the territory of underboosting and losing responsiveness. Its hard to explain and i know im not very technical but i tried my best...
Grinder34
Track Monkey
yeah i mean i know what you're saying (i think). But I have an pretty much unmolested engine (gr ic on a gd, and thats it), and i still run into problems. It even seems weird (to me, an outsider to the tuning world) that you have to have tables for the wastegate and its not just a feedback loop. Like the target boost would be in a table, and the boost controller would feedback with the boost sensor and make all the adjustments. Maybe it just cant tweak fast enough and you'd end up with more problems, but if i were designing a system that would be my first attempt.
Speaking of overboosting in higher gears: Is it just higher gears at lower RPM? At one of the tracks I go to im maxing out fifth and having to run in 6th. Its rpm-range-appropriate (i can literally redline in 5th and must use 6th)...should i be worried about overboosting?
Speaking of overboosting in higher gears: Is it just higher gears at lower RPM? At one of the tracks I go to im maxing out fifth and having to run in 6th. Its rpm-range-appropriate (i can literally redline in 5th and must use 6th)...should i be worried about overboosting?
I agree completely. I guess in the whole scheme of things, I know nothing about tuning...other than what some of you guys have taught me. :lol: But I still
assumed, because it makes the most sense, that it'd be a feedback circuit.
This is a great question, I'm glad you brought it up. I ran through 4th all the way to redline before shifting into 5th, so I was doing about
104 at the time, only then did I go into 5th. So even at over 100, there is still too much load on the engine to go WOT without overboosting?!?!
For you Grinder, I think you're probably a little safer than I, because you are still on the stock turbo, correct?
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No, this wont happen when running through the gears. its only if you decide to throw the hammer down at 1.5k rpm in 5th or 6th gear where you will run into the problem. like i said this can be tuned out to a certain degree and the best time to do it is early spring late fall but for places like michigan and how its been stupid cold this winter for it to take him to finally realize that this has happened is a little more of a special circumstance. nothing to really flip out about yet. This scenario is drastically different if you go catless downpipe versus catted stock.
HolyCrapItsFast
Drinks beer!
The turbo's output is governed solely by load along with variable like atmosphere and temp and the ECU can only do so much to compensate. The problem is the tables we need to compensate for gear are not available to us on the GD but they are available on the GR in AccessTuner so there is really no excuse if you drive a GR. I'm not sure if those tables are available in RomRaider though.
For AIT the tables are available for both so there is really no excuse for that either. My previous statement about tuners tuning for different times of the year are for tuners that don't really know what they are doing with the factory turbo control.
I revised what I wrote previously so you may want to go back and give it a re-read :tup:
I myslef have to experiment a little more with the AIT comp table because you really can't know for sure that your values are solid until you actually reach the temperatures you are compensating for. In this respect my original though on tuning for different seasons holds true.
For AIT the tables are available for both so there is really no excuse for that either. My previous statement about tuners tuning for different times of the year are for tuners that don't really know what they are doing with the factory turbo control.
I revised what I wrote previously so you may want to go back and give it a re-read :tup:
I myslef have to experiment a little more with the AIT comp table because you really can't know for sure that your values are solid until you actually reach the temperatures you are compensating for. In this respect my original though on tuning for different seasons holds true.
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I had a Grimmspeed 3-port EBCS brand new in the box when I took the car to my last tuner. He said "I don't use those.
The factory boost control system is more than capable."
In hindsight, maybe I should have asked if he knew how to use them.
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Alter3go
New member
Always challenge them scrubs. Seriously though like Fuji was saying they all tune differently and some of these guys don't quite treat your car like it was there so they miss minute things or tell you something bogus. I usually try to stay involved, but without being annoying if that's possible ??
It can be difficult, especially if the shop has multiple projects going on. I can't sit still, I can hardly leave the car
there and go somewhere. I just want to be there to see everything happen, which of course isn't always practical.
I trusted the shop and the tuner at the time, but now that I know more than I did then, I'm sure I'd have more in
depth questions and requests for the tuner.
Alter3go
New member
Yeah dude I know what u mean and it's true it isn't always practical and healthy lol
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