Thoughts On This Problem


Championship White

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The engine:

Skunk2 Valves
Skunk2 Retainers
Skunk2 Valve Springs
Skunk2 Stage 2 Pro Cams
Jenvey ITB's
Standard B16b Bottom End
Emerald ECU

The problem:

When VTEC engages something causes a lack of air and it splutters audibly, on the dyno graph it is stangled of air at around three points while in VTEC and is down on power everywhere after VTEC. In non-VTEC there is no lack of air. On the first dyno graph where everything worked there was a very slight dip in power where there is a very pronounced dip in power caused by a lack of air.

Everything outside the internals of the engine has been tested and were fine.

The cams have now been replaced with standard B16b cams to see if this is being caused by an unsuitable set-up (though this wouldn't explain why it would get worse) and will go back to the dyno on Friday or perhaps Wednesday. We'll also be experimenting with throttle opening to see if this makes any difference by allowing less air to the cylinder.

I'll post the old dyno up when I get a chance.
 


olly ek9

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Have you hooked it up to an afr meter so you can see whats happening to the mixture when vtec cuts in, mega rich would suggest the air starving you mention
 



olly ek9

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Wonder if the valves are still closing properly once its on the vtec cam,, are your valve clearances too tight? What clearances are you running?
 

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tama666

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Have you hooked it up to an afr meter so you can see whats happening to the mixture when vtec cuts in, mega rich would suggest the air starving you mention

...^I would look into the above...over fueling could be the issue.
 


Championship White

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It's the cause of the lack of air which I want to identify, richening is just a byproduct of the lack of air.
 


tama666

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It's the cause of the lack of air which I want to identify, richening is just a byproduct of the lack of air.

That is one way of looking at it. ;)
I would think that over fueling could make it sputter like lack of air would in other words.
You have checked the MAP sensor I assume and TPS?

edit: Sorry I only just noticed you have ITB's
 

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Rory

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Have you tried running it without the airfilter?

Does the car run fine outwith VTEC? Aye usual power and torque figures.

Cam timing ok?
 



Kozy

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Part throttle or WOT, or both?

Do Jenveys need balancing/syncronising?

Possibly a bad setup on the cam timing, too much overlap?
 


Championship White

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Have you tried running it without the airfilter?

Does the car run fine outwith VTEC? Aye usual power and torque figures.

Cam timing ok?

Nope, haven't tried that.

Yep, runs fine without VTEC.

With the Skunk2 cams, even a the slightest movement of the cams makes the problem alot worse, it's at the optimum setting at the moment.

it sound like the car need's tunning

We've had two experienced tuners try to diagnose the problem with no luck.

Part throttle or WOT, or both?

Do Jenveys need balancing/syncronising?

Possibly a bad setup on the cam timing, too much overlap?

It runs fine on part throttle.

The Jenvey's have been looked at but they're going to be gone back over today to try having them open less etc.

Could be a bad setup but that wouldn't explain how it got worse. The engine now has B16b cams to see if that is the problem.

Hopefully I'll have some more up-to-date graphs today or Friday.
 


Rory

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Odd one really, whip the air box off just to make sure the filter isnt being sucked into the trumpets.

Im presuming you have tried to lean the fueling out, via the emerald ECU, but to no avail?

Certainly something stupid, if the car works fine out with Vtec.
All settings ok within the ECU?
 


Gorbash12346

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possibility that one of the vtec followers is not locking in and staying at low lift? do you have a sports cat or cat that could have collapsed? other than that a massive air leak where the inlet seals against the head?

timing out is definately one i'd check and re-check

spark plug gap and impedance check of leads etc?

failing ignition coil or incorrect ignition timing

a few ideas to get you started
 


Vtec6000

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It doesn't make any sense, If there was a lack of air it wouldn't improve at some points whilst in vtec and not at others. What are your afr's for the most part at wide open throttle? A lean missfire can look like a rich condition on the lambda meter.
 


olly ek9

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i have a wideband lambda if you need it looked at whilst on the road etc,, let me know
 


Championship White

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The car's going back to the dyno on Friday with B16b cams and I'll get the old and new graphs and scan them so I can post them up for people to have a look at :nice:
 


Championship White

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I now have the old graph which I will scan in tomorrow. More info: B16b cams are just the same with the same lack of air at the same places.

A change of cam gears (from Skunk2 Tuner to Skunk2 Pro which were on their previously before they cracked [Skunk2 cam gears are rubbish quality]), the cam gears removed were slightly damaged on the inside as if they'd rubbed something. The change of cam gears made the engine run better but the problem was still present.

Ordered a new timing belt in case this was causing any issues as the cam gears seemed to have been defective, but I doubt it is the culprit.
 


type-r-dunk

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When i had a full S2 stage 2 setup in my dc2 the optimum cam timing was exactly 0 deg. So oem pulleys would have worked fine.
Your ITB's aren't too small or big are they.
Dunx
 



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