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boost level.

2416 Views 13 Replies 8 Participants Last post by  Obike
alright. after all the different things i've read about the tc and how much boost people have put into them on the dyno i'm trying to figure out if anyone knows what a safe daily driving boost level is. i know that people have taken the boost up to 12 and 14lbs on all stock internals and made a good bit of hp and tq. but i'm wondering what is a safe boost level that can be run daily without having to worry about the motor blowing up after a couple of months driving it. i need to know if i can set my car at 12lbs and be able to run it all day every day for 2 years or more or should i only set it at 8 or 9 for daily use and have a high boost setting of 12. i know about how the drivetrain is week and all that good stuff. i'm not worried about that. the way i look at it is when something breaks it just means i get to fix it with something better. if anyone knows the answer to this question please enlighten the rest of us.
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The boost level itself doesn't mean much unless you know the size of the turbo or supercharger that you are running... also having compression maps is a huge help. For example, on a pea-sized turbo (for example, GT22) it'd be safe to run a higher boost setting than what you'd run for a GT28RS. It is also highly dependent on the tune, because if it isn't tuned right no matter what size turbo and boost level you are running you can blow the motor.
i'm going to be running a TDOH-18G. it will be ran with a front mount bigger injectors the whole 9 yards. when i install it i'm also going to get it dyno tuned hopefully by element tuning. he is the same guy that tuned my buddies sti to make 380hp at the wheels with 20lbs. of boost on pump gas. no he isn't running the stock turbo either. that also isn't an aggressive tune. when it comes to my car i was thinking about just getting it tuned to 8lbs. but if i'm going to be able to set it up to 10lbs and still be safe then thats what i want to do. thanks for any help guys i appreciate it. i know a descent amount about turbo set ups but i don't know it all. id like to learn as much as i can before i put one on this spring.
Is that adjustable boost? I would say 5-7 will give you an extra little jump day to day...more than that and it will just wear daily too much im afraid. I wouldn't push it to much more than 14-15 or you are going to go KABOOOM!
Most of what was said here was right on the money but one critical thing that always seems to be left out is this:

If you run the crap out of you car constantly you will wear it out sooner.

That said, a fairly high level of boost, properly tuned, can give years of service as long as you are not thrashing it 24/7.

A low level of boost improperly tuned can lead to disater quickly, as mentioned is slightly other words.

A moderate level of boost that gives you great usable power when you want or need it can easily be driven normally most of the time and yet be alot of great fun when you want to go for it.

Big numbers are for dyno queens that see very little real world use, go for reliable power, which seems to be in the 300WHP range, then just do not hammer the car all the dang time and you should have all you really need or can use on street tires and on the street safely, it should be capable of quite a life span.

BUT, things can always go wrong, nice to know there are alot of doner cars out there with our motors in them, cheap to replace:)

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so far all i'm hearing is things i already know. the one thing i want to know is, aside from taking in cfm as a factor what is a safe boost level for this motor. about 75% of my driving is casual driving to and from work style. especially in the winter. thats only bc nobody is out wanting to mess around and i really don't feel like going out to mess around. so would it be safe to say that i should be able to set the boost at 10lbs and not have to worry about it. i already said i'm going to get it dyno tuned. not to be a dyno queen, but just to make sure i'm getting what i paid for.
The thing is, when you are daily driving... you'll most likely be staying out of boost the entire time. So that isn't really related to boost level as one would think (unless you floor it everywhere you go, then I'd say go for a low boost level).
unless he gets a turbo timer, which can be set for turbo to kick in at ...2500 rpm? id say stick to no more than 9lbs for daily commutes
Originally posted by NavyDoc05@Dec 14 2005, 02:04 PM
unless he gets a turbo timer, which can be set for turbo to kick in at ...2500 rpm? id say stick to no more than 9lbs for daily commutes
You mean an EBC, as turbo timers exist to let everything cool down when you turn off the car.
Boost controllers don't determine when boost comes on. The wastegate stays shut until a preset boost is achieved. I have yet to see one that holds the wasgegate open until a preset rpm, then closes it to build boost. It's a novel idea, but I don't see a practical application for it.
Considering everything that has already been disscussed, if I were you I think I would keep it around 8-10psi and not have to worry about it.
There are two considerations for boost level: fuel quality and the engine's mechanical strength.

1. 91 or 93 octane can only support a certain amount of cylinder pressure before it autoignites and starts detonating. If you are willing to run 100 octane fuel all the time, then you can run higher boost. If you can afford to run 100 octane, you wouldn't be asking these kinds of questions.

2. The engine can only support a certain amount of cylinder pressure before the cylinders crack. Open deck blocks are not as strong as closed deck, so if you don't modify the block, there is a certain amount of boost that will cause the cylinders to expand past the Young's modulus of the materials (cast iron and aluminum) and cause permanent deformation leading to cracking. To find this pressure you need to do a hydrostatic test on the block itself, and once you've determined this pressure, you know you can never exceed it without expecting the throw the block away.

You have your homework now. Go find the answers.
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i hate it when lance gives me homework. he grades tough.
Originally posted by inevitablegod@Dec 18 2005, 01:47 PM
i hate it when lance gives me homework. he grades tough.
At least you don't have to worry too much, you sleep with the teacher. Us that work for our grade tend to get the shaft... and not in the way that you and Greg's mom tend to like so much.
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