Restriction In The Exhaust

[rondofj]

Well that problem was there in the first full tune when I swapped to PowerFC from Nistune, I asked them to fix it this time, it was only a touch-up tune and 'massaging' it in this time after the exhaust fix, nothing major. Its definitely a 3-4sec major power drop with downshifting, sounds tune related aye?

[Ben C34]

Well it's a result of the ecu doing something dumb, which it determines by how it is tuned. So yes, it is tune related.

I would be cranking some more preload on the actuator. They wouldn't do it while tuning due to the heat around the manifold and turbo scaring them away, but letting it cool on the dyno to try it out would have been cheaper than another tune.

[89CAL]

Seen as the problem wasnt there before and youve only improved the flow of exhaust gas leaving the turbo, then I'm not sure what else it would be?

[rondofj]

Thanks guys I will ask them to have a re-look, lesson learnt is that no matter how reputable the tuner, they never get it right in the first tune, not in my experience anyway

[Ben C34]

Unless they do all the work and truly know the car.

It's hardly their fault.

[rondofj]

Its a 40mm wategate off housing, T boost controller so no actuator. I also dont see why its dropping 4psi up top now when before it was going from to 20-18 and 18-16 with the jem tune/nistune.

[89CAL]

Do you have a boost controller?

If not, what spring do you have in the wastegate?

Only other thing could be the smaller turbine housing (maybe it needs a .8?), but I dont know alot about the precision turbos so I'm not even sure what size the turbo is lol. Anyway if no boost controller then that might improve it, if it alread has a boost controller then it might need some adjusting due to the change in exhaust flow

[XKLABA]

The external waste gate is you actuator ( its all in one unit ), I believe he said he has a T boost controller so its a bleed off setup, so the EBC will help to a point at both ends

[GTSBoy]

Boost drop is easily answered. Reduced back pressure in total means less restriction all the way back to the inlet and less boost required for a given amount of flow. Choke off the exhaust again and the back pressure will report back to the intake side at high revs again and Bob's your older male relative....less boost drop off at high flow.

[rondofj]

Oh that explains it then..4psi drop is a bit much though.. Yes I have a turbosmart T controller off gate and other end connected to nipple in compressor housing, 18psi spring in wastegate so not lacking in that department. One nipple on the top of the gate is unconnected though?

[scotty nm35]

With an ebc you can route boost to the top port to help hold the gate shut.

[GTSBoy]

Yeah, a manual boost T type controller will never be able to stop the top end falling off if that's what the turbo wants to do. You need an EBC to take it by the scruff of the neck and force it to do what you want.

[rondofj]

Cheers-mite be my next mod- will any ebay electronic boost controller like cheap china hdi do or only apexi avcr/ greedy profec spec 2 etc? Hope touch up tune wont be required as its already tuned to 22psi- Im about sick of all this tuning which isnt leading anywhere much..

[Ben C34]

Gizmo have one for 290. I would look at that.

A trader on here has then for that price delivered in the four sale section.

[XKLABA]

The best and easiest EBC I have used is the HKS EVC 4 ( jap version ) 5 ( US version ), as with any thing car related " you get what you pay for "

[89CAL]

Yeah better way to do it, holding boost on top and bottom then bleeding the top pressure off. Id say the boost control is the issue with the boost tapering off up top but still doesnt explain the hesitation when downshifting

[hy_rpm]

How's your intake ? 3 inch all the way and free flowing as Tao from hypergear has tested at 250kw there is a difference of 13kw going from 2.5 inch intake to 3inch

Also .63 rear housing may becoming at restriction on a 6cylinder and that power level and boost

[rondofj]

3" metal intake, 40mm gate, plumb back bov and plumb back screamer to 3" dump

[iruvyouskyrine]

#@rondofj trying to send you a PM but your inbox is full.

[hy_rpm]

Well can't be the intake then

But might be good to search how much power people been getting using .63 with a rb25