Losing Boost at about 5000 revs

[J Alesi]

Hi Guys

Got a bit of a tricky problem that I can't work out

Last week went to Chequed Tuning in South Dandenong to get my car re-tunned for the first time in 3 years. He told me it was set very very rich, and that I was losing boost around 4,500 revs. We changed the spark plugs, then checked all the intercooler pipes to see if they where tight. They where.

Then is said to change the catalytic converter which I did it was really dirty full of black smoke (which was fuel). It is still loosing boost at around 5,000 revs.

Im going to ring mazda to check the oxygen sensor, I think this is burned out.

Whould this cut out boost?

Is there anything else it could be because I am stumped!, and it is not the solenoid on the turbo because I just replaced it.

If anyone can help that would be great.

Hope to hear from you soon.

[rogwick]

Have you got any mods installed mate, or running stock?

[bd581]

You said you changed the spark plugs.
Did you check the gap?
If so, set them properly?

[Toddy22587]

does the boost slowly drop off a few psi at 5000rpm or is it a big drop? the standard turbo can cause a small drop in the high RPM range because it cant flow enough air. Also the throttle plate begins to close up but i thought this only happened after about 5500.

[J Alesi]

Have you got any mods installed mate, or running stock?

Hi mate

I have had the following mods
front mount intercooler
dump pipe
3"exhaust system
turbosmart BOV
standback chip series 3
stronger fuel pump

---------- Post added at 11:58 AM ---------- Previous post was at 11:58 AM ----------

You said you changed the spark plugs.
Did you check the gap?
If so, set them properly?

The spark plugs are all good mate

---------- Post added at 12:01 PM ---------- Previous post was at 11:58 AM ----------

does the boost slowly drop off a few psi at 5000rpm or is it a big drop? the standard turbo can cause a small drop in the high RPM range because it cant flow enough air. Also the throttle plate begins to close up but i thought this only happened after about 5500.

yes it suddnely drops off, Trenton at Chequered tuning has done about 5 MPS and he says they didn't drop off after 4,500 revs

[rogwick]

That's actually slightly less mods than me and I only get a problem above 5,500RPM as Toddy mentioned. Have you got a DashHawk or access to borrow one? Perhaps get some information from it and see what's going on at 5,000RPM?

[Doug_MPS6]

Pretty much the same mods as mine. I haven't noticed a drop off in boost. Are you sure its a boost drop, or are you talking about a reduction in "urge". If so it could be one of a few things, such as fuel starvation due to pump shortcomings (less likely as I see you have beefed up yours, but possible), your SB tune programmed to start retarding ignition (more likely), and so on. Do you have a stock inlet pipe or did it get amped up with the FMIC?

[Caffeine Fiend]

Maybe check your MAF sensor and give it a clean?

If it's dirty it could be giving false readings that the ECU is trying to compensate for.


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[J Alesi]

We where doing tests at 15 pounds boost, it was holding that all the way to 4250 revs when it got to 4500 revs it lost 5 pounds of boost to go to 10 pounds.

Trenton told me it should hold this all the way to 5500

[J Alesi]

Im taking it to Mazda today, I think it could be the waste gate that is not woring properly , please wish me luck as most Mazda mechanics don't know there spanners from there screwdrivers.

[rogwick]

wish me luck as most Mazda mechanics don't know there spanners from there screwdrivers.

Lol its like how folks don't know "their" from "there" haha, all the best for the service, hope they sort your problem

[Doug_MPS6]

From your description it sounds like premature waste-gate opening

[J Alesi]

From your description it sounds like premature waste-gate opening

I think you are right, how do I know for sure.

Mazda didn't find anything wrong, but when I ask them to look at it properley they didn't want to waste their time!!!!

Can the waste gate be tuned or does it need to be replaced?

[Doug_MPS6]

Depends on the tuning software. I assume the Mazda system can do it.
You can specify maximum boost with the Standback, which I assume determines waste-gate function. Others here have had waste-gate issues and have replaced the operating solenoid. Suggest you search the threads with "wastegate". Chs.