Forum » Boost Control » MX5 MZR Duratec - GTX3071R Gen2 - Tial Housing 0.86 + 44mm EWG - Boost Creep over 6000rpm

MX5 MZR Duratec - GTX3071R Gen2 - Tial Housing 0.86 + 44mm EWG - Boost Creep over 6000rpm

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Hello Guys,

I've heard there are many knowledgeable people here so thought I see if any of you can advise/help me please.

I hope I did this under the correct forum location.

Right.. I do a little back story.

I turbo'd my MX5 NC/mk3 which is a 2.0 MZR (Duratec engine)


SCH10 1.25" manifold

GFB EWG 38mm (vent to atmosphere)

GTX3071R gen2 + Garrett 0.61 V-Band Turbine housing.

2.5" Downpipe into 3" system.

This made 304WHP @ 14psi. Yay! and held boost well.

due to extremely bad luck the car ended up getting written off due to being pulled out on.

So I ended up purchasing another one but I did a different route with the turbo setup (Moving the ABS and alternator to free up room)

Spec of new setup;

SCH10 1.25" Manfiold

SCH10 1.5" EWG take off

Forge EWG 44mm (vent to atmosphere - Has a 38mm outlike pipe?!?!)

GTX3071R gen2 + Tial 0.82 V-band Turbine housing.

This setup pulls like a train, it hits spring pressure of 12-14psi then over 6000rpm it ramps up hard to 18-19psi, this was in 4th gear I've not done a 5th gear to redline so can't comment on if it will creep even further.

The boost ref for the EWG is right on the 90degree elbow where the previous setup was further down on the aluminium pipe to the inter-cooler if this makes a difference.

I'm a little stuck, I have a few ideas, well kinda thinking outside the box;

1. The EWG outlet pipe of 38mm is just not man enough (Odd considering old setup with 0.61 was fine)

2. The 3" downpipe over the 2.5" is enough to cause the problem.

3. The barb for the boost ref. to the EWG is just too small? It's a 1-2mm hole but the OD of the barb is 4-5mm

4. As the map is being dialled in my old setup ran 15 degrees at peak RPM. currently after 6000rpm it drops from 13.5 to 12.5

I hope you guys have an idea or advise. I've attached a log from ecutek if that will help. I didn't hit redline in this log as the car is still in the tuning stage but it gives you an idea.

I've attached photos of old setup and new setup.

Don't get me wrong.. It's not a bad thing as it top rpm and if anything keeps that torque curve flat if not goes up. But it's just nice to have the control rather than a run away train.

Thanks :)

Attached Files
  • LFH9EF_TL-adj-_SD-3-4_LINDSEY-DEAN_10.10.18-10-10-2018-19-57-53.csv
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Sorry for the slow reply. The thing that jumps to mind is the way the wastegate is taken off the collector. You've got the wastegate in the new setup coming off a beautiful v-band collector at 90 degrees. The exhaust flow won't want to make the turn into this and hence it's very likely to promote high rpm boost creep. The pics of your old setup don't really show the wastegate integration so I'm not sure if that setup was better.

In general I'd normally step up to about a 44mm wastegate for this combo which would help but if the wastegate isn't coming off the collector in a smooth fashion you can have trouble irrespective of the wastegate size.