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Old 21st September 2018, 06:54   #1
Ste.Sales
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Default Power issue after swapping to alloy inlet manifold 1.8t

Hi all,
Got sick of changing IMG on plastic manifold so I obtained an alloy one to finally cure the leak.
All ran fine until I floored the accelerator a couple weeks later. It accelerated very swiftly until 4000rpm when it started to misfire and splutter.
After investigation, I found the spark plugs gapped at 1.1mm so I changed to 0.6mm. misfire and spluttering now gone. But:
When the revs reach 4000rpm full throttle (2nd and 3rd gear), the car takes off like s**t off a shovel! In fact the acceleration is so severe that the clutch has now started to slip when hitting 4000rpm.
I used torque pro to monitor boost levels. It climbs to 12psi at around 2000rpm then drops off back to 10psi by 3000rpm and holds steady thereafter. I am not getting any boost cut, and there are no fault codes stored.
Any ideas why this has started to happen? Anyone experienced anything similar? Or should I drive with a lighter foot?
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Old 21st September 2018, 07:42   #2
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So are you saying that you are getting (much) more power over 4000 revs? If so this probably indicates a more efficient induction, and more efficient combustion in general; which is the aim of fitting the alloy manifold. ( Is it not?) Just because you have the extra power, though, doesn't mean you have to use it every time you hit the throttle...so a lighter foot may help as you'll stress many additional components otherwise.

I would think that the engine and injection is closely mapped to the original manifold, so possibly a remap to more suit the new one with its different airflow characteristics may be possible.... Others may be able to advise more comprehensively here...based on their own experience and knowledge.
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Old 21st September 2018, 11:22   #3
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Yes. I have much more power coming in at 4000rpm. It's almost like a VTEC system jumping to the hot cam, but more violent.
The only reason I swapped to the alloy manifold was to stop coolant leaks at cylinder 1 and 4.
I don't drive with my foot glued to the floor all the time, but, my work journey involves two hairy right turns across and onto busy dual carriageways. I'm curious, has anyone else noticed a huge increase in power after fitting an alloy manifold? I can't see this being normal.
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Old 21st September 2018, 12:22   #4
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I think it illustrates that the plastic manifold is a compromise, maybe better suited to the non-turbo rather than the turbo engine. They perform very very differently, and I have one of each so I can compare... I think you should be happy with the result...you may even get more economy if you drive with this in mind, rather than outright power, which is useful in tricky situations, as you say, but you don't need it all the time... I'd say you have a successful swap....!
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Old 21st September 2018, 21:19   #5
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Check the boost solenoid, sounds like it isn't doing its job properly. 12psi is high for a standard map, should be around 8. Unless of course it has been mapped?
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Old 21st September 2018, 21:33   #6
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Did you change all the sensors and injectors from your original inlet manifold?
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Old 21st September 2018, 23:03   #7
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The later plain Jane variant is required to accommodate the MAP sensor for MEMS3, as the early MEMS2J manifold is different John.

The turbo has a different throttle body and injectors, so the originals must be used.

Finally don't fit the VVC manifold without the support bracket, and yes I've fitted a turbocharged K series with a VVC head, but converted to solid inlet cam, as the output on the ECM for VVC mechs and Turbo boost control clash

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Old 22nd September 2018, 09:27   #8
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Quote:
Originally Posted by marinabrian View Post
The later plain Jane variant is required to accommodate the MAP sensor for MEMS3, as the early MEMS2J manifold is different John.

The turbo has a different throttle body and injectors, so the originals must be used.

Finally don't fit the VVC manifold without the support bracket, and yes I've fitted a turbocharged K series with a VVC head, but converted to solid inlet cam, as the output on the ECM for VVC mechs and Turbo boost control clash

Brian
Any ideas on the dates for the introduction of MEMS3 ? I guess you could identify with the extra wire going to the sensor?

I think have seen some TFs without the support bracket in the past, would this have been removed in project drive or perhaps just some lazy so and so couldn’t be bothered to fit them/it?
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Old 22nd September 2018, 13:59   #9
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Are the holes for support bracket already there?

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Old 23rd September 2018, 02:17   #10
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Sounds like a boost control issue - Solenoid failing or Vacuum hoses disconnected or connected to the wrong ports maybe - Symptoms sound like what I experienced (Prior to fitting the Alloy Manifold)

r.e the Alloy Manifold - I have a Positive view since fitting mine - along with a K&N panel filter it sounds Good too Alloy is more tuneful than Plastic

My only Technical Concern would be - I'm pretty sure there is a slight port size mismatch between the VVC Head and the standard K-series Inlet Ports I haven't noticed any compromise since fitting mine

I accept it may well be the Placebo affect However I did feel that throttle response was better(even prior to the K&N filter) I'm sure the VVC Plenum is bigger volume wise - maybe this affects turbo spooling ?




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