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Discussion Starter · #1 ·
hey there,

it would seem as though my engine (v6) looses power, noticeably, above 5000. this isn't so apparent through 1st and 2nd but pulling through 5k in 3rd and 4th there is a noticable loss of accelleration up there. it's almost as though someone put their hand in front of my air intake... could this be a timing issue? i'm not sure if i need my timing belt replaced. i've very recently replaced my plugs, cap, rotor and wires although the problem was apparent before this.

any thoughts?

thanks!
 

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Try this:

Use a tie-wrap (or bailing wire) to tie the #2 VRIS plate open. This is the VRIS just behind the throttle body. Make sure your wire is secure and won't get fouled up in the throttle linkage. Take the car for a spin and see if your power comes back.

You'll likely lose some torque below 4250 during this run, but the intent of this test is to see if the #2 plate is closing prematurely (or not even opening). If your power is magically back in the 5000 range, check the vacuum hoses, actuator and solenoid for the #2 valve.
 

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Well isnt the peak horsepower at 5200 or 5300 rpm? So thats where the most hp (164hp stock) happens and ya above 5300 there is no more power to gain... Maybe I'm totally off...


LaTeR...




:eek:
 

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After around 5500rpm you start to loose power.
 

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Discussion Starter · #5 ·
actually peak power comes closer to 5800, however the problem i was having came pretty much right at 5000. turns out my #2 VRIS vacuum actuator was flakey. replaced it and zoom zoom!

thanks for everyone's help.
 

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MexySexy said:
Sorry, but what is the #2 VRIS? What does VRIS stand for?


THanks.

:eek:
KL-series V6 engines have extra butterfly valves in the intake manifold that serve to vary the effective length of the intake runners in a system Mazda calls VRIS - Variable Resonance Intake System. There are two sets of butterflys: a single plate over by the timing belt side of the engine called the "#1 plate" and a dual butterfly near the throttle body called the "#2 plates".

The intent of varying the runner lengths is to maximize torque through the RPM band and it works quite well (when it's working :E)
 

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So doesn't it "hurt" the engine to rev it that high anyways? (Over 5800... rpm) Like can't the head gasket blow and other bad things? Of course if you do it a lot that is.


LaTeR....


:eek:
 

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Discussion Starter · #9 ·
MexySexy said:
So doesn't it "hurt" the engine to rev it that high anyways? (Over 5800... rpm) Like can't the head gasket blow and other bad things? Of course if you do it a lot that is.


LaTeR....


:eek:
if the engine wasn't made to rev that high, then yes you would be hurting it. if you're engine is tuned up and running well, there's no reason for things to fail if you give it the juice often.

:)

cheer,
 

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MexySexy said:
So doesn't it "hurt" the engine to rev it that high anyways? (Over 5800... rpm) Like can't the head gasket blow and other bad things? Of course if you do it a lot that is.
No, 5800 isn't that high for the KL V6. Mazda engineered the bottom end pretty well and it is, by some accounts, 9000RPM-capable. The valvetrain (heavy HLAs mainly) and camdrive are what limits the RPM on these motors...that and the fact that the intake/exhaust/cams are not designed to breathe anywhere close to that RPM.

Even still, the tach redlines at 7000 and the fuel cut in the PCM is set at 7500RPM for a reason; it can take it. It's not wise to live at 7000RPM but on-ramp and drag-strip bursts to 7000 won't hurt an otherwise healthy engine.

Headgaskets blow mainly because of two reasons: people neglect the cooling system and overheat the engine, resulting in severe enough distortions in the heads and block that the seal is broken and second, people overuse nitrous or turbos. On these engines, head gasket failures are almost unheard of (compared to say, the old Olds Quad-4 that ate head gaskets for lunch.)

Continuous high RPM can cause fatigue in the rod bolts, which can loosen ever-so-slightly, reducing bearing crush resulting in a spun bearing. Oiling can sometimes be a problem too. Imperfections in rods and pistons (e.g. casting flaws) are more likely to show up under high RPM (remember, these are production engines with mass produced parts...bad stuff can get through once in a while).
 
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