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.

 

[Wildside22]

Even if he has a junk, knock-off BOV that is allowing boost to leak, it would not cause the turbo to spike up since its being regulated by the waste gate. The boost gauge is showing the spike and that tells us that the bov is holding since he is seeing pressure in the manifold where the boost gauge is reading it. That leads back to the waste gate or the wastegate actuator and/or adjacent lines. Now I would argue about the lines being the issue because you can run with no line on the wastegate actuator and the internal spring pressure will hold boost until its value is reached where the pressure would force the flapper open. I would look at the wastegate actuator itself as previously stated or the flapper unit.

 

[AngelOfPassion]

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

I don't see where he said it was better than a 1g BOV. He was just saying the type s was ok. Which I agree with. Most of the knockoff type s bov's fix the leaking issues that the original has anyways. Either way the BOV isn't the best place to look for a boost spike issue and if it was causing pressure build up he would notice it in the boost gauge right away and know it is a problem with the BOV. On a side note: I think the attidude in the beginning of this thread was terrible...

 

[Dert]

OP, forget all this bs about your bov, your bov has nothing to do with boost spike, a crap bov will leak air causing little to no boost bein made. Like stated earlier, check lines for split, check actuator, run a line from the turbo to the wastegate bypassing the boost control solenoid. And for those knocking on the fact that it's a type s knock off, if it's a NGR type s it is actually more reliable and built better than a lot of these "name brand" pieces of sh*t that are being sold for double the price...

 

[AngelOfPassion]

Finally someone with some sense besides Wes.

 

[Beaubo]

I also agree that the attitudes of some of these DSMers is poor. The hostility and demeaning responses to probationary members is totally uncalled for. Just because there is a title underneath their user name specifying their introduction and activity on this website doesn't mean they have no expierience with these vehicles.

 

[JusMX141]

The OP came here looking for advice, not a tongue-lashing on a topic he's likely unfamiliar with.

Consider the fact that there is no boost controller listed that he's likely still using the factory BCS which may be seized or not functioning otherwise, and that's the reason for the 16psi spike. I've seen T25's spike to 22psi when hooked to a non-functioning boost control solenoid when using a blow-off valve that actually seals.


Negative rep and rule infractions will be handed out- this is bullshit. Help the guy or don't post.

 

[izzieDSMER]

Yeah I am running the factory boost control solenoid. I didn't know it could also be at fault. Is there anyway to check it?

 

[AngelOfPassion]

Yes. Run a line straight from your boost source to the wastgate actuator nipple and see if it fixes the problem. Then you know it is either the solenoid or the line to the solenoid which are very easy/cheap to replace.

 

[Wildside22]

I agree that you should remove the factory BCS from the equation. Do as previously stated and run a line from the boost source to the nipple on the wastgate actuator.

 

[Dert]

If its not completely clear how to hook up the line from turbo to wastegate, here's a lil diagram I dug up, ignore the "boost dial" in the middle of the line ...

You must be logged in to view this image or video.

 

[Black-Out]

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).

I would also say that the other half to this behavior is in the factory tune if it hadn't been reflashed. 2g's have higher compression and with that they need less boost to achieve the desired torque delivery from the engine. When the engine is at higher RPM a lot of manufacturers will drop boost pressure to reduce the heat the turbo is trying to introduce to the air charge but they will re advance the timing to keep torque flatter- the engine speed is higher and a flatter curve can be achieved by dropping boost pressure slightly, adding a touch more fuel to keep things cool,and adding a little timing to maintain the torque delivery up high. I have yet to see a factory tuned car that doesn't spike high then peel back boost pressure to protect the engine from heat soak under extended exposure to wide open throttle. Mind you this is a practice for the FACTORY's tuning, not necessarily the aftermarket but that's the principle behind it as far as repeatable performance and reliability are concerned. If you have access to a proper scan tool that can relay real time data you can high light the fields of manifold pressure,Ignition timing,injector pulse width in milliseconds,and lambda and watch it as you make a 3rd or 4rth gear pull. You can see the way the car is programmed to behave as the w.o.t. time is extended beyond 10 seconds- boost will come down timing will go up slightly until the computer senses a lean condition or pre-ignition and then it will lop timing again add fuel till the noise disappears and re-apply timing again and so on till it finds the safest timing and fueling and plateaus there. Race gas will allow the computer to reach full advance as the computer will never hear see pre-ignition because the fuel burns so much differently.
The T25 runs out of puff for sure, but I've seen this scenario played out on vehicles with much larger turbos and the management was programmed to operate the exact same way-



By the way O.P. My factory waste gate control solenoid was bad when I first got my car- The electrical portion or "coil" was good but the actual mechanical portion was sticking periodically- if it hasn't been mentioned check it out by pulling the hoses off of it and then trying to blow through it. if you cant or if it's difficult to blow through then the valve is more than likely stuck and it needs to be replaced. Got mine replaced with one from an RX-7 ......mitsubishi supplied parts to everyone to help them get their cars built-

Will-

 

[izzieDSMER]

Problem solved! It wasn't the waste gate flapper or the lines. It was the stupid boost controller solenoid. It wasn't doing a damn thing so the car was boosting like hell. Hooked up a line from the turbo to the wastegate and no more boost spike. Now its a steady 9-10 psi all the way across. Thanks guys!

 

[AngelOfPassion]

You are welcome! I don't know why they put those darn things on our cars anyways . I have always thought that running wastegate pressure is always more reliable until you want to turn the boost up with a controller. They should have just put 12psi wastegate actuators on our turbo's to begin with and just not used the solenoid.

 

[izzieDSMER]

Yeah the stupid thing is stuck I blew on it like you said and nothing came out.

 

[Dert]

Glad to hear you fixed it. Happy boosting

 

[poizondsm]

Im having a problem were ( first off my boost is set at 24psi with a hallman MBc and a greedy type s) at whatever throttle as soo as I hit like 15 psi my bov just starts goin off!! What the heck is this, did my bov just crap out??

 

[WES_393]

Does the car buck at the same time? If so, the engine is misfiring or the ECU is cutting fuel. Do you have the proper supporting mods (injectors, fuel pump, etc) to handle over 15psi?

 

[Dert]

Im having a problem were ( first off my boost is set at 24psi with a hallman MBc and a greedy type s) at whatever throttle as soo as I hit like 15 psi my bov just starts goin off!! What the heck is this, did my bov just crap out??

The spring might be weak and letting the valve open at a certain boost instead of holding it shut. And for the record it's greddy not greedy. Not sure why but I'm always reading people typing greedy .