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Over boosting

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I've put a few mods on it allready but it seems that it still spikes too about 10 - 12 psi at around 3500 - 4000 rpm and if I don't back off it hits boost cut and loses all power, goes into limp mode.

Can I get a flash tuner and take the boost cut off?

I want to be able to hold it at WOT and run all gears to red line with out it over boosting and going into limp mode.

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doing mods without a tune is just asking for the symptoms you've got.

 

you WILL need a custom dyno tune (whether you get a flash tuner box or not, but you will need a tune flashed to your car at minimum) to suit the mods you've done.

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It was a stock car when I bought it no mods done, but it was hitting boost cut just the same but was abit worse.

 

The exhaust was damaged when I bought the car. Turned out it was restricting exhaust air flow, I had the damaged section cut out and the cat gutted as it was ruptured and parts of the cat were lodged Futher down the exhaust, got that cleaned up and also had the middle muffler deleted.

Car seemed to run alot better after freeing up exhaust flow.

 

But still would hit boost cut if pushed too around 4000 rpm.

 

So I got a boost gauge installed and now I've found if I back it off when I spikes the 10psi it won't cut power.

 

Surely these cars in stock form shouldnt hit boost cut at 4000rpm??

 

Would a tune fix this?

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these (a stock BA XR6T) cars won't make 10psi in the OEM configuration.

 

the OEM injectors just don't support much more flow than stock.

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So your saying that it's been previously tuned?
and now it needs a retune to getting it to stop hitting 10 psi or smooth out the boost spike when it's under load or something

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that could be one scenario... or it's got a physical situation that is causing it to overboost, for example: an up-rated actuator installed, an actuator stuck closed, boost control not connected correctly or controlling correctly (tune/solenoid/sensor) etc.

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@k31th Regardless of previous dramas, won't extra flow from the gutted cat allow it to hit boost limit way earlier?

Let alone with 'other mods' mentioned

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Okay well where do I find the sensor? Thought it was just a solenoid controlled by the ECU didn't know there was a sensor.

More exhaust flow is better for turbos I thought?

 

I guess Ill look into getting bigger injectors / fuel pump ect before a tune.

How do I find out how big the injectors are in my car atm?

also not sure on how to remove them?

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Camo is correct, removing exhaust restrictions will allow the turbo to boost easier and hit boost cut. It's needs a tune, the factory ECU can't adjust for mods and the ba engines are fragile. Actuator and solenoid are the other problems that can cause those symptoms without the exhaust modification.

The ECU uses 2 MAP sensors, one in the intercooler piping under the battery and one in the manifold.

Injectors are easy enough to replace, but you can't change them for bigger ones without a tune.

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Also I should have mention that I can hit rev limiter in first and second if I launch it and it won't hit boost cut.

It only hits it boost cut once it gets to like 3500 - 4000 rpm in 3rd.

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Do you have a boost gauge? What boost is it hitting in 1st and 2nd? The vehicle is under more load and can produce more boost under more load.

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Yep,

Gauges are useless if they dont warn or have peak recall. Whats the chance you will be looking at the oil pressure gauge when the oil pump dies. ???

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Do you have a boost gauge? What boost is it hitting in 1st and 2nd? The vehicle is under more load and can produce more boost under more load.
So I guessing that in 1st and 2nd it's probably not building any more boost then 10psi, allowing it to rev out and not cut, I'll have to check it today.

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So yeah took the car for a drive the other day and I've confirmed it sits at 10psi WOT through first and second but as soon as I shift into third and plant it, it wants to sit on 12psi then it cuts.

 

could I possibly by pass the boost solenoid and stop the ecu boost cut?

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yes, that should limit the boost to what the actuator is rated to and get there as slowly as the turbo can build the boost, so that'll bypass the tune's boost control and allow you to diagnose it mechanically instead of electronically, in the first instance.

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Okay well I'll give it a go on bypassing the boost solinoid and try just it on waste gate pressure

 

Should I unplug the boost solinoid or leave it plugged in?

 

I'll just run a hose from the turbo directly to the boost actuator

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just leave it plugged in.

 

yep, from the front of hte turbo to the actuator is the bypass methodology.

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Screenshot_2019-11-24-10-28-30.thumb.png.6450a9b52dae81e4c4c6ec6b0b1774b0.png

 

A snapshot from a recent outing. Looks like the Turbosmart IWG actuator is misbehaving and allowing boost to exceed commanded levels of a recent tune. A common thing it seems from comments made previously by @JETURBO. Have NFI what spring is in there, maybe a 8-9lb spring would help? or back to a Garrett actuator?

GT3576/billet wheel has had flapper mod done, apparently.

Went out for a spin today and max boost was 18.8 (U98). AIT's were stable around 38-41C despite being a pretty warm day, so the CAI & Plaz 800 is doing it's job.

Question is, are these obd2 readings accurate as accel reading seems a bit odd.

 

Motor gets heat soaked after 6-8 pulls as standard 91C thermostat and high speed fans come on at over 100C. Prolly should go the 82C stat with the lower thermo fan activation setting in the tune for the tropics as per @BJC, although there was a bit of past debate, as I recall, over the value of doing this.

I hope this would be a quick and inexpensive job for the tuna to do?

No idea what the STFT1 reading means except near 0 is good at idle.

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My bad. Thanks for the heads up @El Andrew I did look at the conversion a while ago, but clearly that info went through to the keeper.

My simple error could be a good thing that car may not be over boosting, I'm certain it is way over 10 PSI though. 

Car was previously up to 21 PSI on dyno and recently retuned to 17, so hence my apprehension.

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Firstly watched a few youtube vids. Bought cheap ELM327 reader on Ebay, downloaded and opened torque app on phone, turned on wifi to pair etc etc. 

Will upgrade to Torque pro soon to access more info such as trans temp. 

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