Boost related question

[izzieDSMER]

Okay I recently got a 2g gst spyder and when I stomp on it goes to 16-18 psi and if I keep on smashing it falls to 12 psi and stays there. My question is, Is that boost spike normal? I got a stock t25 and aftermarket boost gauge, upper I/c pipe and knock off blow off valve.

 

[ChiTownHussla]

U gave a 3 inxh exhaust right?

 

[Nicklepage1010]

Probably a boost leak. And get rid of that blow off valve.

 

[izzieDSMER]

You know what I haven't looked at it closely but it does have an aftermarket muffler. It looks like stock pipes though.

It shouldn't spike like that right? I mean I've a 1g talon that didn't do that.

 

[brownie956]

It may or may not be a boost leak, but it would be worth testing of course. From the mods info you gave, that sounds like normal T25 operation to me. The stock boost pressure is 10-15psi. Officially, a pressure of 6.4psi is acceptable according to the manual, but I've never heard of a stock vehicle producing that little boost, anyway, I digress. The 10-15psi can and does vary with a number of factors. I'll try to keep it succinct. First off, normal boost on a stock car in ideal weather conditions generally produces a maximum of 14.7psi and drops off to a low of 10psi at and near redline. The reason for this is the T25 is a small turbo and operating near its limits. With the stock intake and exhaust system incurring a significant amount of backpressure and resistance, the T25 simply can't supply the same amount of boost at 6-7k as it can at 3-4k, because the engine is taking in much greater quantities of air. Secondly, the weather conditions and engine conditions also have an effect on boost pressure. For example, if it's hot enough out the ECU will retard timing and lower boost pressure to prevent knock. During some of the hotter days in summer, I experienced this and saw my boost pressure max out at 12 and maybe even 11psi, when normally (like that very same evening) it would hold 16psi all the way to 6.5k (I don't redline my car).

 

[izzieDSMER]

Yeah that's what the car is doing Slammedndirty. I don't have the stock one because I bought the car like that. Wow U guys really think it could be that knock off blow off valve? I mean the car pulls hard and it doesn't fuel cut or anything. It's just strange to me that it would spike like that. I mean I don't have a boost controller or anything to boost more.

 

[Eagle96TalonTSi]

1. Find a 1g BOV - 20$
2. Check all IC piping clamps
3. BOOST LEAK TEST! 10$ in little parts from your local lowe's/home depot and a compressor
4. You have a T25, which in high RPMs can run out of air, causing your boost to come down.
5. Take your intake > turbo piping off and spin your turbo around, move it up and down and in all directions. If theres any play in it that could be causing the problem.
6. TURN YOUR FING BOOST DOWN DUMBASS. You should NEVER go back 12 psi on a t25... Youre just asking for problems. Its okay, youre a noob and everyones been there. Turn your boost down and save your engine.

Oh yeah, and turn your boost down. Did I mention that? Better yet, take the MBC OUT of your car if you want it to last more than 2 weeks.

 

[izzieDSMER]

NO BOOST CONTROLLER!!!!!!!!!!! I don't have a boost controller. O yeah again no boost controller.

 

[Colt4G63 also]

Check your hoses to and from the wastegate solenoid. you may have a leaky one.

Ps. Hey guys, did you notice the OP has no boost controller?

 

[AngelOfPassion]

Holy shit you guys are breaking a lot of forum rules in this post.

OP, since you don't have a boost controller something is causing you to spike. It's normal for the T25 to go back down to 10-12psi in high RPM's but it is not normal to be spiking to 18psi. I would search this site for causes of boost spike (not creep) and see if you can find some good info. Also, Colt made a very good suggestion right above my post.

Ignore the hateful posts in this thread and try to take some good info from the proven members.

 

[M4s73r]

Wow what a bunch of tool bags. Way to welcome new people.
here is a possibility. Your wastegate hole may have some cracks. sometimes the wastegate flapper will stick. so when it gets hot it sticks. once it reaches up into 18psi it then forces the flapper open and you return to 12 pounds.
There is nothing wrong with the BOV. and a boost leak wont cause that either. If it was a BOV or boost leak you would lose boost not gain 6psi.

PS get your BOV out of the trash and put it back on. The rude asses should calm down and have some dip.

 

[AngelOfPassion]

^^^^yea cause i have no idea what im talking about cause im not a proven member... hahahahaha

Obviously when you think a blow off valve can cause boost spike before any shifts/throttle let offs occur.

 

[izzieDSMER]

Yeah I got to check those hoses to the wastegate solenoid. One more question, Would a crack on the wastegate were the flap sits cause this too?

 

[M4s73r]

One more question, Would a crack on the wastegate were the flap sits cause this too?

YES. This is what I was talking about. There is your boost spike issue. BINGO!!

 

[AngelOfPassion]

Yeah I got to check those hoses to the wastegate solenoid. One more question, Would a crack on the wastegate were the flap sits cause this too?

I'm assuming you mean a crack in the housing where the wastegate flapper is? If so I'm not sure. It could go either way in my mind. My instinct would say that a crack would allow more air to leave through the wastegate passage which would help your spike issue, not cause it.

But also, the crack could cause some air to leave and prevent the flapper from working correctly by keeping it closed longer due to air having a way around it... Or keep it closed for other reasons.

Someone who works on turbo's more than I do would have to give their input on that.
EDIT: Ninja'd above me. I guess there is someone who is more toward my second theory...

 

[izzieDSMER]

Its getting more complicated than I thought.

I should just upgrade this turbo is on its last leg. I like how it spools though, anything bigger that spools the same? I've been reading on small 16g's.

 

[M4s73r]

heres a simple solution for you. Genuine MHI 16g Turbo | eBay



Great Minds Think Alike

(and ps thats mine, direct bolt in)

 

[Dert]

Check your lines running to your waste gate. If there is a split in it it can cause uncontrolled boost. With the t25 being small and inefficient, it's possible the spike is the uncontrolled boost and it bleeds off because the turbo can't handle maintaining that boost level so it falls off. Also could be boost leaks helping out bleed off pressure. Check all the lines, make sure the flapper isnt sticking and if all else fails, ditch it and get a 14B/16G

 

[izzieDSMER]

Man I wish I had the money. Chumash casino wiped me out. LoL! I took my turbo money. Now I have to save up.

 

[Dert]

Check classifieds on here, usually someone is selling a 14b or 16g variant for cheap

 

[izzieDSMER]

Will do Sir

 

[M4s73r]

This says it all.

 

[WES_393]

And get rid of that blow off valve.

throw the bov in the trash and put a stock one back on.

1. Find a 1g BOV - 20$

What exactly is the basis for this advice? The OP never mentioned what kind of BOV, just that it was a "knock-off". For all you know it could be a fake Type-S, which is a strong unit that can be recirculated. Some of these replies are just ridiculous. The advice and the attitudes are completely unnecessary.



OP- It sounds like you have a problem with the wastegate actuator. Cracks in the housing aren't good, but I've only seen that lead to more lag. Not to say it's impossible, but it sounds more like poor wastegate operation, like a sticky or leaking actuator.

I would start by inspecting the wastegate lines for splits. If the wastegate is still hooked to the factory boost control solenoid (little black box under the MAF), try running a line straight to the wastegate actuator. Also try disconnecting the actuator arm from the flapper and see if you can freely move the flapper by hand. If you have access to an air compressor, slowly pressurize the actuator with about 10psi. The arm's movement should be smooth, not delayed or notchy.

If you find a problem with the actuator, Garrett T25 actuators are a dime a dozen. Some knock-off actuators are set to 1 Bar (14.5psi) rather than 9-10psi, so be careful where you buy. But obviously any actuator is better than a busted one. Over boosting can cause some serious damage to the engine.

 

[izzieDSMER]

It is a fake type-s I found the receipt on the car. You Sir know what you're talking about.

It's also recirculated

 

[Eagle96TalonTSi]

What exactly is the basis for this advice? The OP never mentioned what kind of BOV, just that it was a "knock-off". For all you know it could be a fake Type-S, which is a strong unit that can be recirculated. Some of these replies are just ridiculous. The advice and the attitudes are completely unnecessary.



OP- It sounds like you have a problem with the wastegate actuator. Cracks in the housing aren't good, but I've only seen that lead to more lag. Not to say it's impossible, but it sounds more like poor wastegate operation, like a sticky or leaking actuator.

I would start by inspecting the wastegate lines for splits. If the wastegate is still hooked to the factory boost control solenoid (little black box under the MAF), try running a line straight to the wastegate actuator. Also try disconnecting the actuator arm from the flapper and see if you can freely move the flapper by hand. If you have access to an air compressor, slowly pressurize the actuator with about 10psi. The arm's movement should be smooth, not delayed or notchy.

If you find a problem with the actuator, Garrett T25 actuators are a dime a dozen. Some knock-off actuators are set to 1 Bar (14.5psi) rather than 9-10psi, so be careful where you buy. But obviously any actuator is better than a busted one. Over boosting can cause some serious damage to the engine.

Uhhhh wrongo!

A 1g > greddy type S all day. The Type S' rubber seal is straight garbage and will shit itself within a few months. The spring inside it is also poorly manufactured. Its probably right about the same as stock 2g which = trash. Not saying it is the problem, BUT if youre having boost issues... a shitty BOV would be a good place to start.

The reason I assumed you had a MBC is because it sounded like your boost was set to 18, but then dropped to 12. Idk how its even 12 either when stock 2g boost is usually reported at 7-9 psi and was 9 psi on mine.

And noone has a poor attitude, youre just "sensitive" I guess

With all due respect though, you always give good advice.

Except for the knockoff type S being a decent BOV, thats hogwash