My DIY Turbo build

Discussions relating to Turbochargers, Superchargers, Induction, Engine Mods, Exhaust Mods, and other items specifically to make your MX5 or Roadster put out more power.

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Habanero666
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Re: My DIY Turbo build

Post by Habanero666 » Mon Oct 05, 2009 4:38 pm

poison wrote: If the IC is too large you'll get more lag and slower initial boost, that's the only downside. I have quite a big IC on mine and wonder if it's partly responsible for boost drop off at higher revs. I hit 12PSi then it tapers off to about 9 by the red line. Mine is a T25 being about the same size as a TD04.

Hi there Gazza, I was bored today and spotted this from you. I would have to say the wastegate actuator (AKA the "can") you are using is not able to hold at the higher rpm range and is just a simple matter of going down the " helper spring" path or increasing the hold off spring threshold. 12psi boost is 4psi above the actuators standard 8psi rating on the t25. Even with EBC the weakest link will be the mechanical component in this set up. Sing out if you want to know more.

Jim Hartley
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last_resort14
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Post by last_resort14 » Mon Oct 05, 2009 6:33 pm

Funny you bring this up as it is now my main drama

I am trying to hold 12 psi but Im just spiking 12 quickly and tapering back to about 8.
I have tried sourcing the wastegate signal from just before my throttle body as I had heard this helps but its no better.
The Greddy kit TD04 comes with a 5.5psi wastegate spring, so like you say I am working in a range that doesn't suit.

How are you controlling boost on your setup Hab? Or are you just running wastegateless to get your 21psi?

Habanero666
I count 5-s in my sleep
I count 5-s in my sleep
Posts: 408
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Location: NZ

Post by Habanero666 » Mon Oct 05, 2009 7:14 pm

last_resort14 wrote:Funny you bring this up as it is now my main drama

I am trying to hold 12 psi but Im just spiking 12 quickly and tapering back to about 8.
I have tried sourcing the wastegate signal from just before my throttle body as I had heard this helps but its no better.
The Greddy kit TD04 comes with a 5.5psi wastegate spring, so like you say I am working in a range that doesn't suit.

How are you controlling boost on your setup Hab? Or are you just running wastegateless to get your 21psi?

Hi there, I can suggest a quick solution; Pack up the wastegate actuator bracket with washers between the bracket and where it bolts onto the compressor housing.
This will put preload on the spring, also you will need to wind out the adjustment fully on the linkage arm. With this you will be able to use a bleed type Boost controller (boost tap) to acheive around 16-17psi if needed.

The 1.6 I had with the TDO4H-15g (pre 19T compressor housing swap) would run upto 17psi before the intake temps went highish. Also you will need a dump pipe like the one I posted earlier with the divorced wastegate and exducer bore pipes.This is what really made the difference to controlling boost at higher engine speeds. I am selling that pipe and a complete TD04H 15g separately. PM me.
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Habanero666
I count 5-s in my sleep
I count 5-s in my sleep
Posts: 408
Joined: Tue Nov 13, 2007 5:00 pm
Location: NZ

Post by Habanero666 » Thu Nov 26, 2009 10:47 pm

last_resort14 wrote:Funny you bring this up as it is now my main drama

I am trying to hold 12 psi but Im just spiking 12 quickly and tapering back to about 8.
I have tried sourcing the wastegate signal from just before my throttle body as I had heard this helps but its no better.
The Greddy kit TD04 comes with a 5.5psi wastegate spring, so like you say I am working in a range that doesn't suit.

How are you controlling boost on your setup Hab? Or are you just running wastegateless to get your 21psi?

Throw that waste gate actuator on trade me next to mine! They are only designed for 5.5psi.

DO NOT take the signal from the throttle body as you are not accounting for the pressure drop through the intercooler and will overheat and compromise the coolers efficiency with respect to intake air temps.

Ever seen how a headless chicken still runs?
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poison
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Post by poison » Tue Dec 01, 2009 11:30 pm

last_resort14 wrote:I am trying to hold 12 psi but Im just spiking 12 quickly and tapering back to about 8.
I have tried sourcing the wastegate signal from just before my throttle body as I had heard this helps but its no better.
The Greddy kit TD04 comes with a 5.5psi wastegate spring, so like you say I am working in a range that doesn't suit.
I missed this one, I have the Garrett T25 and am having exactly the same thing, I hit 12 pretty fast and then it falls off and never makes it back up past 8PSI, end reuslt I should be on 235HP not 200 :( I'm being robbed.

Hananero666 has been giving me some tips via PM. But I had a wee fall and broke some body parts so am unabel to try them just yet.

So Luke did you make anyprogress? I am confused over the wastegate spring limit of 8PSI as I have also read this about the T25, if it was 8PSI why does it make it to 12PSI in the first place? I need to do a slow run to see if it can hold 12 and still falls off as I think that would negate the spring issue. ALso the BOV is something I have been told to look at.
:twisted: Gazda in the white HOT Mazda :twisted:

Habanero666
I count 5-s in my sleep
I count 5-s in my sleep
Posts: 408
Joined: Tue Nov 13, 2007 5:00 pm
Location: NZ

Post by Habanero666 » Wed Dec 02, 2009 1:47 am

WARNING the following post is little bit techy. Please feel free to go to the * section if feeling cranial congestion.

The reason why you get a CREEP up to 12 psi boost above the can rating of 8psi and then see it weasel its way down again is :

Boost pressure rises to 12psi on the inlet manifold side (using a bleeder type boost controller to alter the signal to the actuator diaphragm), this creates a massive jump in exhaust gas pressure in the turbine housing caused by the cylinder pressure increase from denser air/fuel intake charge,
Turbine Housing exhaust gas pressure overcomes the actuator tension (holding the wastegate valve shut) and blows the wastegate valve open, dropping the boost pressure at the inlet side by lowering the turbine speed.

*That is simply put; while all the exhaust gas roars out the wastegate port the boost is limited.
It's a bit like opening your car door on a windy day in Wellington; your arm is the actuator and the door is the wastegate valve and the wind is the exhaust gas pressure. Untill the gust of wind slows or stops you cannot hold the door shut.

When the wastegate valve is forced open boost goes v
When the wastegate valve is shut closed boost goes ^

Important note techy again

When you fit a a bigger diameter Dump pipe to a turbo you can get a higher boost ouput of 1-3psi and faster spooling. This is because you are removing BACK pressure at the turbine housing exit, allowing more exhaust gas to flow from the cylinders, through the exhaust manifold into the turbine housing, spinning the turbine faster/ sooner and exiting efficiently out the exducer bore into the dump pipe (untill this reaches peak flow through the turbine housing exducer bore).

This explains how pressure in the turbine housing effects the wastegate operation and subsequently boost.


Hope this clears it up.

Jim
Tires aren't cheap!

sprsta
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Post by sprsta » Sat Jan 29, 2011 2:54 pm

the only mx5 at the nationals

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