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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 01-26-2016, 12:22 AM   #21
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So I followed Cyotanis suggestion to lower overboost protection and unplug the wastegate.

I will post the data logs later, but it resulted it only a 200 +-50 rpm better spool.
I then changed out the filter for the rx8 one I have (it'd quite a bit bigger) no difference on the data logs. I also plugged the pcv port on the the manifold, as it is a boost leak I have yet to fix, and that too made no difference.

The turbine spins quite freely, had to check as I have seen that being an issue, so we can knock that one out.

I did notice a bit of soot coming from the exhaust manifold gasket which is mated to the head, though not much at all.

Anyone have any advice on what to check now? Could it be the way I have my IC piping routed?

At this point I am really looking for suggestions of anything.
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Old 01-28-2016, 12:24 AM   #22
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Was looking at other peoples build threads and I realised that my GT2560R from ATPTurbo is a bit different than the rest.

I have a .80 a/r compressor housing with a 60mm wheel, instead of the .60 a/r compressor housing with a 60mm wheel.

I do however have the same 53mm turbine wheel with the .64 a/r housing.

Would this be the culprit causing the slow spool response?!?

Last edited by HexRX; 01-28-2016 at 11:56 AM.
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Old 01-28-2016, 12:34 AM   #23
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I think I read on Garrett's website that a/r isn't very important on the cold side. I like ATP turbo, they post their maps. Sadly, it looks like 4psi @ 3000 and [email protected] is about what the maps predict.

Maybe you should post some videos. I'm always glad to see turbo miatas tearing it up
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Old 01-28-2016, 12:39 AM   #24
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Haha, I'll get one recorded soon.
The turbo feels great, its just the onset is quite late. As I approach 4k rpm, the car begins to pull extremely hard. That is wonderful but I was really looking for a bit earlier onset of power, the useful powerband feels quite limited because once it hits peak boost it rips through the next 2k rpm and I have to shift.
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Old 01-28-2016, 12:45 AM   #25
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If you want the best wastegate control, get a dual port external gate, or dual port wastegate can for your current turbo. Then use a diagphram pressure regulator on the top port to regulate boost pressure. Set preload as high as you can if running a can type wastegate.

When I ran an external 38mm gate nad diaphram pressure regulator, the wastegate stayed 100% shut until you were within 2 PSI of target boost. GT3271 hit 28 PSI at 4,500 RPMs on a 1.8L.
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Old 01-28-2016, 02:05 AM   #26
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that big a compressor wheel is not helping......given everything else seems to be what we all think should be okay...I would say it is the culprit.
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Old 01-28-2016, 07:15 PM   #27
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Thoughts on his tune?

A bit of extra fuel at 3K can help spool. Or even dialing back spark timing a tad at that point. You loose some 'response' in a sort of subjective way, but get earlier spool.

Extreme measure may be to advance the intake cam 1 tooth or use adjustable cam gears. It'll shift the powerband left at the expense of top end - which this car seems to have plenty of.

More than anything, a collection of little tweaks is the order of the day.
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Old 01-28-2016, 07:19 PM   #28
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Hmm, that is an interesting thought. I'll try dropping the fuel a point, from 12.5 to 11.5 through that rev range, worste case it won't help, best case you will help. I've found a few more leaks here and there, its now hitting 10psi @ 3800.. So 200rpm increase, if the additional fuel and less timing can add another 200, then the 3" taking another 200-300 off should put me right where I want to be.
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Old 01-28-2016, 07:21 PM   #29
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Wouldn't advancing the intake cam give it 12 more degrees of overlap? I'd thought about getting a cam gear to play with cam timing, but I'd always considered going the other way

I like the tune idea for sure. I'd love to see the data logs before and after
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Old 01-28-2016, 07:23 PM   #30
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Quote:
Originally Posted by squeegee View Post
Wouldn't advancing the intake cam give it 12 more degrees of overlap? I'd thought about getting a cam gear to play with cam timing, but I'd always considered going the other way

I like the tune idea for sure. I'd love to see the data logs before and after
I'll post all of the data logs I've taken through this process this weekend, I have midterms at school right now.
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