Turbo spool in neutral

[dsmgst1996]

Ok after hours of searching i can not find an answer I just put my 99 gsx back together and put a stock t25 on it for the time being . no when im in neutral rev the motor to about 3k the turbo spools to about 10 psi i know this is not normal what could cause this could my timing be off ???????

 

[dsmgst1996]

compressor nipple to boost controler back to wastegate after further veiw i took it out for a drive and if i drive faster than 60mph its starts boosting on flat ground as if i was trying to pull and i was just cruising

 

[thereef]

Uhh, I know the t25 starts to spool at about 2500 on stock 2gs.. Don't see a big problem here.

 

[COdsm]

Uhh, I know the t25 starts to spool at about 2500 on stock 2gs.. Don't see a big problem here.

Free revving at 3k should not make 10psi... they start to spool IN GEAR at about 2500.

 

[dsmgst1996]

the problem is they should not spool when not in gear with no load 2.5k in gear pulling i under stand that but spooling with clutch pushed in and free reving should not happen unless over the last 15 years all my other cars have not been right

 

[TurboLaserRS]

A car can spool the turbo without a load. It can't maintain the boost without said load though. Are you sure your boost gauge is hooked up properly?
If you can maintain boost, your ignition timing could be excessively retarded. That's essentially what anti lag does is retard the timing to the point unburned fuel is combusting as it hits the exhaust wheel to keep it spooled.
I'm pretty certain your car would run like crap if that were the case.

 

[dsmgst1996]

A car can spool the turbo without a load. It can't maintain the boost without said load though. Are you sure your boost gauge is hooked up properly?
If you can maintain boost, your ignition timing could be excessively retarded. That's essentially what anti lag does is retard the timing to the point unburned fuel is combusting as it hits the exhaust wheel to keep it spooled.
I'm pretty certain your car would run like crap if that were the case.

I can hold boost sitting there my fuel trims are at -10.4% short term and long term the same it does not run real bad it idles smooth and pulls ok its power is not up to snuff but im geuss that what ever is causing my boost issue is probaly cause my loss of power

 

[kidtsi]

What are you talking about? , that's like a dream... JK

Is your mechanical timing align?

 

[dsmgst1996]

What are you talking about? , that's like a dream... JK

Is your mechanical timing align?

well you are right i would normaly love this but when cruising at 60 and your boosting im sure that is going to eat up gas quick .... as far as mechanical alignment i will check it tommorow but i set this one the same way i have set the other million timing belts i have put on

one thing i just noticed is at idle im only at 13 vac and my other car runs around 20vac or so? odd

 

[Boostdriven]

Sounds like you need to check your mechanical timing. Set your crank pulley to 0* on the timing belt cover and look at your timing marks on the cam sprockets, I bet they are off.

 

[dsmgst1996]

problem fixed the exhaust cam was advanced one tooth now power is what i would concider normal and vac is at 21 at idle thanks for every ones input

 

[Boostdriven]

Glad you got it fixed

 

[clipto]

+1 on getting it fixed, timing can be a bi*** always trying to take power away even 1 degree of timing at that.

 

[solson1041]

Could someone explain exactly how/why bad mechanical timing could cause this? I don't have the problem, but I'm curious what exactly is going on here.

 

[dsmgst1996]

From what i under stand is the motor is firing and losing compression out the exhaust valves causing the turbo to spool using the pressure from the compression stroke not just exhaust. it was also causing it to run rich as hell and my long term fuel trim and short term was tring to pull almost as much fuel out as she could.

 

[Boostdriven]

One tooth off on the cam sprocket is 15* off on the crank. I'm not sure on the exact duration of stock cams but for example if you take an exhaust cam that normally starts to open and has 1mm lift at let's say 25* before bottom dead center (BBDC) and you advance it 15*, now you get 1mm valve lift at 40* BBDC. So when the piston is going down on a fire stroke and the valve opens early before most of the fuel is burned, that causes the fire blast to escape in to the exhaust with more force causing the turbo to spool up. That's a first part of the equation.

Another part is now that your valve opens 15* early this means it will close 15* early not allowing all of the exhaust to escape. As the valve closes there is still some hot pressurized gases left in the cylinder that gets compressed again and mixed with the intake charge as an intake valve opens.

Working on DSMs for some years now I've learned that if you're not careful its very easy to make a mistake and set your timing wrong, either one tooth off on either of the sprockets or half a tooth on both, but it is easier to make a mistake and set both cams half a tooth off on each. Mitsubishi didn't give us a mistake proof timing marks like I've seen on other cars. When setting up cam sprockets if your not careful you can set both sprockets either half a tooth rolling away from each other or towards each other and still have the marks look like they line up including the mark on the crank sprocket. I would say this is the more common mistake. You really have to get down and look directly at both sprockets and make sure that not only the inside two marks line up but the two outside ones line up with the two inside ones. So if you were to lay a straight edge across they would all line up.

In the case where only one sprocket is off a tooth then as you line up your cam sprockets to look like they line up your crank sprocket will move one tooth off either way depending on which cam is off. This is an easier mistake to spot if you double check your double checking

I'm glad you got it figured out, sometimes a lesson is learned best when it derives from our own mistakes

 

[jed344]

When i do timing on a dsm if i have extra set of paws will have them pull the belt so there is tension already on cams as well as pull them together as if to be half a tooth off. Then when pin is pulled on tensor and it pulls tight they line up exact.

 

[brandonclum]

I would say the nipple on the stock j-pipe and the wast gate being disconnected definitely fix that before you drive it again.

 

[dsmgst1996]

I would say the nipple on the stock j-pipe and the wast gate being disconnected definitely fix that before you drive it again.

hose runs from the jpipe nipple to the boost controller then to waste gate.It was always hooked up right