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Discussion Starter #1
Hey all,

I'm hitting boost cut (12psi i think) in 3rd gear at about 100Kph.
There is a small hose running from the turbo to the boost sensor (i think that is what it is) on the firewall. I was bored on the weekend so I mucked and installed a small ball valve on this line and close it a little. This has stopped the boost cut for now, but can this do any harm?

I know it would be better to upgrade the ECU with Chiptorque or something, but I want to avoid the $600 cost. The car is still running full rich when it hits boost cut, so it not leaning out or anything.

Any thoughts?
 
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u mean the map (manifold air pressure) sensor on the firewall perhaps?

and that hose should come off the throttle body...

where in that line have u installed the bleed valve? close to the map (and in which colour striped hose) or closer to the turbo? but to the best of my knowledge there is no hose running from the turbo to the firewall...let me know after you have had a look :)

it just seems odd as the boost cut usually occurs when the air flow meters internal flap maxs out for more then 3 seconds - which is why it boosts so hard then cuts out.

that can be stopped by opening the AFM up and adjusting the little slide so that it doesn't max out - but again - then u have completly eleminated the boost cut, and if the wastegate jams u'll end up with way too much boost/air and no where near enough fuel - and PING! PING! PING! melt and crack....lol

in one of my earlier posts a few of us are looking at upgraded computers...probably the EMS at this piont is lookin gthe best bang for buck so maybe register some interest there even as we are looking at much cheaper prices in bulk..?

and just so u don;t think i'm an idiot....one thing i've noticed anyway is there is no piont in more then 10-12psi of boost anyway!

past this the turbo is working out of its effective range and radically increasing inlet tempurates - which requires more ignition retard off setting the power gain - not completly - but working things too hard...nothing but a stop gap solution tomore pwoer.

not only that the stock intercooler pipes change diameter drastically from as large as 3 inchs and more at the AFM and TB, annd yet - in other places i.e. turbo outlet, ic inlet and out let - less then 2 inchs - with the increased air flow above 12 psi these pipes don't help either and infact to get 16psi in the manifold - the turbo is putting out over 20! Which is of course way way out of its band, with turbo outlet temps well over 140 degrees!...

so i've done enough lecturing now - i'll leave it up to you - if u need any information etc i'm quite happy to help :)
 

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Discussion Starter #3 (Edited)
i just checked, and I was incorrect.

The hose comes out of the wastegate actuator hose (from a T piece) and goes back under the inlet manifold. This is as far I can track it..

I installed the valve (its not a bleed) in this hose. Its disabled now (ie. completely open) as I didn't want to break anything. I was just doing some testing.


Pics of the valve arehere


If it helps, when it cuts out, the car loses all power and something beeps continous from behind the dash until I ease off the accelerator, and then everything is back to normal straight away.

I also have completely redone all intercooler and intake pipes, replacing them with 2.5" mandrel bends. I don't really want to run more boost than now. It maxs at 12psi then drops back to 10psi at higher RPM. At no stage does my A/F gauge read lean.


Perhaps a dyno tune can give me a bit more power without raising the boost by leaning it out a bit. How much scope for adjustment does the AFM have for this?
 

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i gained about 4kw by adjusting the air fuel mixture b/c i was also running rich under boost. Do this dy drilling out the plug on the airflow meter and adjusting the mix a bit.
Have a sparkplug gap of about 8-9mm also. This was all done by the guy who owns EVO on his dyno.

P.S. hows my IC pipe kit going
 
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hmmm ur selling intercooler piping upgrades?

if so please let me know!

my biggest killer is not having a car on thr road 24/7 to make the mods I want and bolt would be easier :)



now back to the topic - the beep is to let u know u have hit the overboost cut.

there is no way around it other then ai i said before.

so perhaps naths on the right idea - for now get a dyno tune completed and see how it runs :)
 

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I have drilled a hole with 1.5 drill piece and inserted a little nail and used selleys needit metal to holed it in place. It has removed the boost cut and now i am running about 13psi. If you boost too high and get knock the ecu will retard the boost and timing to stock 7psi (well in my car and i run optimax).

Works great, i highly recommend it!
 
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