DIY Turbo Discussion greddy on a 1.8? homebrew kit?
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Turbo lag?

 
Old 07-01-2008, 07:56 PM
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Default Turbo lag?

So my new setup is with an SR20 (.80/.64) T25, begi mani, FM cast dp. My spool seems slow, especially compared to my previous setup- ebay mani/dp, .48/.49 DSM T25. Car has 1.6L, 2.5 inch exhaust, test pipe, BTW.

New setup spool: 11 psi at ~3500 rpm
Old setup spool: 11 psi at ~2700 rpm
The numbers above were checked by pulling in 5th gear, just to reduce factors like timing/fuel/etc.

I just rebuilt the SR20 turbo with the kit from gpopshop, but the compressor wheel showed a tiny bit of damage (slight bends at the inducer blade corners).

Is this the reason for the turbo lag, or is this considered normal spool for this turbo?
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Old 07-01-2008, 08:17 PM
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.80 exhaust A/R...
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Old 07-01-2008, 08:18 PM
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That does seem a couple hundred RPM slow. What WASTEGATE ACUTATOR are you using and it set properly?
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Old 07-01-2008, 08:33 PM
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my spool-up sucks.
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Old 07-01-2008, 11:21 PM
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I get 11 psi at like 3700 rpm.. stop bitching haha.
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Old 07-02-2008, 12:04 AM
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12 psi @ 3200 rpm and i'm running a t3... you either have a leak (exhaust pre turbo or boost) or a crappy wastegate. i'm pretty sure you should spool faster than that.
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Old 07-02-2008, 08:35 AM
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Originally Posted by y8s View Post
.80 Exhaust A/r...
+1 While the two turbos are similarly sized, they have completely different A/R that will affect spool.

First example I could find and not a miata but here is the same turbo on the same car only changing the exhaust housing from A/R 0.63 to 0.82. ~500rpm diff in spool.
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Old 07-02-2008, 09:02 AM
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Originally Posted by cardriverx View Post
I get 11 psi at like 3700 rpm.. stop bitching haha.
Originally Posted by Arkmage View Post
i'm pretty sure you should spool faster than that.
Originally Posted by brgracer View Post
+1 While the two turbos are similarly sized, they have completely different A/R that will affect spool.

In the multiple setups I've seen with that turbo, it seems very on point. The larger a/r allow for better top end with a slightly slower spool than a .493 a/r housing T25. Enjoy the top end and enjoy the traction.
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Old 07-02-2008, 09:06 AM
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Tom when you say "~500 diff in spool" - do you mean onset of spool? The blue is first out of the gate at <3250 but the red pwns everything else. Can't imagine the red is the smaller AR given the power difference... boost levels the same right?

bryantaylor- any spool plots? specs on the t3/t4?
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Old 07-02-2008, 09:11 AM
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Originally Posted by m2cupcar View Post
Tom when you say "~500 diff in spool" - do you mean onset of spool? The blue is first out of the gate at <3250 but the red pwns everything else. Can't imagine the red is the smaller AR given the power difference... boost levels the same right?
Right, bad example as it was the first convenient one I could find with the same turbo/same car in a quick search, but I do believe that the red is the smaller A/R, but at much higher boost. Just trying to note that the diff A/R tends to shift the whole curve and could account for most of his spool difference.
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Old 07-02-2008, 09:56 AM
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two dynos with said turbo....






is nature of the turbo.
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Old 07-02-2008, 09:58 AM
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Originally Posted by y8s View Post
.80 exhaust A/R...

its a .64 exhaust housing, fwiw.
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Old 07-02-2008, 01:26 PM
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Originally Posted by brgracer View Post
+1 While the two turbos are similarly sized, they have completely different A/R that will affect spool.
Yes, I knew that when I decided to go with the .80/.64 turbo, but by that much (onset of boost at ~800 rpm later)? I can't imagine guys running GT28's or larger. BTW, if I go to the ball bearing version (GT2554R), what could I expect to pick up in spool? ~300 rpm or so?

Also, the wastegate I have is the original actuator at around 10 psi or so. I do have a MBC that is set at 14 psi right now, and it doesn't seem to help spool much if at all. In regards to boost onset, I would think that a MBC would override a bad wastebate actuator...

Last edited by soulcarving; 07-02-2008 at 01:37 PM.
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Old 07-02-2008, 01:47 PM
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Try a helper spring on the wg arm - that reduced spool on my internally gated t3/t4 3-500rpm across the board.
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Old 07-02-2008, 02:03 PM
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Originally Posted by soulcarving View Post
I can't imagine guys running GT28's or larger.
which is the T3, which is the SR20 T25?



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Old 07-02-2008, 06:39 PM
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Originally Posted by m2cupcar View Post
bryantaylor- any spool plots? specs on the t3/t4?
i dont have any plots, it get a couple of pounds starting at about 3k, but not fully spooled till after 4k, but when it does get fully spooled it hauls ***!

its just a regular turbonetics t3/t4, bought it second hand, but i assume its a 57 trim.
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Old 07-02-2008, 06:55 PM
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Once I get my 60 trim running I'll try to do a comparison between a .48 and .63 exhaust housing. All I have are .48 housings, but I'll snag a .63 off ebay or something. Why would you even want such a large exhaust housing on a 1.6?
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Old 07-02-2008, 07:35 PM
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Originally Posted by zoom2zoom View Post
Once I get my 60 trim running I'll try to do a comparison between a .48 and .63 exhaust housing. All I have are .48 housings, but I'll snag a .63 off ebay or something. Why would you even want such a large exhaust housing on a 1.6?
.64 a/r, but a small 53mm 62 trim T25 wheel...

So it sounds like I'm spooling like I should. I'll try the helper spring though. I suspect that I'll have to get a 3" exhaust and EBC. Anything else that helps spool?

Last edited by soulcarving; 07-02-2008 at 07:51 PM.
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Old 07-02-2008, 07:41 PM
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Originally Posted by soulcarving View Post
Anything else that helps spool?
NOS yo!
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