when does boost start?

[97ebaygst]

I'm still kinda new to turbos and I don't know if I have a boost problem. When I take off my boost doesn't build up until about 3000 rpm plus I have to really get on it to go above 10psi and i max at 17psi . Is this normal on a car with a small 16g or do i have a problem? also there are 2 bolts on the down pipe and 1 on the manifold missing I don't know if that would cause this problem. I have done a blt and had a leak at the throttle body and biss that I fixed, I think that I got them all fixed. any advice?

 

[rlacasse1]

You should definitely get the bolts fixed.

My car doesn't hit boost til around 28-3000rpm and it has the stock 14b.

 

[LiquidX]

This will inform you on turbos.
HowStuffWorks "Turbochargers and Engines"

Secondly, fix the bolt on the housing as it is prob. causing an exhaust leak as well. Extremepsi or STM should have the bolt. Shop for the best price.

Next, TURN DOWN THE BOOST. 17psi on the stock fuel system is too much especially for using the 16g - 15psi max.

Do a boost leak test again with a spray bottle of soap and water to be sure you got everything. Not all leaks will make a noise. Spray EVERYTHING that recieves pressurized air or vacuum.

 

[GsXdSmKingGsX]

definetly replace the bolts...please

 

[97ebaygst]

This will inform you on turbos.
HowStuffWorks "Turbochargers and Engines"

Secondly, fix the bolt on the housing as it is prob. causing an exhaust leak as well. Extremepsi or STM should have the bolt. Shop for the best price.

Next, TURN DOWN THE BOOST. 17psi on the stock fuel system is too much especially for using the 16g - 15psi max.

Do a boost leak test again with a spray bottle of soap and water to be sure you got everything. Not all leaks will make a noise. Spray EVERYTHING that recieves pressurized air or vacuum.

thanks for the website. I know how they work just never had one before. i used soapy water the first time but i guess another won't hurt even when i turn my boost controller down I still hit 17 at wot above 6 grand it just changes how early i hit boost if that makes any sense what could cause that? and is it normal for me to not hit boost till 3000? when it finally hits its only about 5 psi

 

[Bender]

It all depends on your turbo. I don't start seeing boost till 4k, and reaches 25 psi at 6,000 (S372). My old 54mm turbo (SCM5031) started building boost at 3500, and was at 20 psi at 4k, and 30 psi at 4300.

If you are boosting that late on your T-25, I suspect you have a crack in your manifold, especially if it is your stock cast iron one. They are small, so you will have a hard time seeing it with it installed.

Edit: I see you say you are only running 5psi at full boost now. That is a cracked manifold/ bad wastegate / bad BOV. More than likely the manifold as that is VERY common.

 

[97ebaygst]

It all depends on your turbo. I don't start seeing boost till 4k, and reaches 25 psi at 6,000 (S372). My old 54mm turbo (SCM5031) started building boost at 3500, and was at 20 psi at 4k, and 30 psi at 4300.

If you are boosting that late on your T-25, I suspect you have a crack in your manifold, especially if it is your stock cast iron one. They are small, so you will have a hard time seeing it with it installed.

Edit: I see you say you are only running 5psi at full boost now. That is a cracked manifold/ bad wastegate / bad BOV. More than likely the manifold as that is VERY common.

I think you read me wrong i max at 16-17 and don't hit 5 pound till 3000. plus i have a small 16g. but thank you for taking time out and posting on my thread.

 

[LiquidX]

If you PSI drops down after it hits 17PSI I would suspect you spike otherwise it sounds like boost creep. Creep is very common on the Evo3 16g, not sure how much so on the other 16gs. What size exhaust piping are you using or is that stock as well?

Fix any preturbo exhaust leaks or missing bolts and if you want to, you can spray some Sea Foam into the motor while running via a vacuum hose on the manifold itself (PCV). After you follow the directions with it, you'll have a mega smoke out. You'll also see any place in the exhaust that is leaking even a invisible hairline crack in the exhaust manifold. I found 2 on my old one when I did that and didn't even seem them there at all.

 

[97ebaygst]

i'm running what i believe is a 3in turbo back exhaust(i bought the car with it on there)

 

[Zdrummer15]

It definitely sounds like you have boost creep. That would be why it still hits 17 psi even with it set lower. A nice free-flowing turbo-back exhaust like you have will cause that a lot of the time. Do a search on it and you'll find solutions for it.

You should be hitting closer to full boost at 3k not 5 pounds though.

 

[Bender]

Misunderstood because of this:

and is it normal for me to not hit boost till 3000? when it finally hits its only about 5 psi

If you set the boost, and at higher rpms it starts rising, you are experiencing boost creep.

If you boost high, then it tapers off, you are experiencing boost spike.

It sounds to me like you have a wastegate problem.. which is common for the 16g's as poor quality control didn't allow them actuator arm to be properly fit to the frame.

Take the two bolts out that hold your wastegate to the compressor housing, and place 2 small washers between the actuator bracket and and turbo (one for each bolt). Then put the bolts back in, and take the car out for a spin, and see if you spool any quicker.

Also, what is your a/f while spooling? For best results, you want it to be 12.3-12.5:1 on a wideband, or 0.910 volts on a narrow band.

 

[97ebaygst]

ill do the washer suggestion. But I don't have an A/f meter so I don't know what I'm running. I think the arm isn't stock though. It doesn't have a bend in it.

 

[LiquidX]

Don't waste your money on a narrow band A/F gauge, they are worthless. Get a wideband o2 I prefer the Innovate LC-1 and can be had for under $200

 

[Bender]

Your slow spool may very well be power related.

The problem isn't with the arm being bent, it deals with it being too long. It leaves a gap between the wastegate flapper and the turbine housing, allowing exhaust pulses to leak out instead of going into the turbo. Shimming the bracket out with washers puts more pressure on the arm, allowing it to close the wastegate all the way.

The downside is the wastegate wont be able to open as far, so you may get boost creep, although it is very uncommon if you don't have it to begin with.

 

[97ebaygst]

i'll try adjusting it first then if that doesn't fix it then i'll do the washer mod. As far as my boost max when should i feel that? and when i hit 17 psi the car doesn't run any different then 10 psi should i still be worried about detonation?

 

[Bender]

You are probably running lean then. The stock ECU pulls timing down if you start knocking. That means you are detonating, but luckily your ECU is compensating. It isn't good for it because it needs to knock first, but it has saved your motor. I would turn your boost back down to stock until you get some gauges to monitor what is going on.