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?

 

.80 exhaust A/R...

 

That does seem a couple hundred RPM slow. What WASTEGATE ACUTATOR are you using and it set properly?

 

my spool-up sucks.

 

I get 11 psi at like 3700 rpm.. stop bitching haha.

 

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.

 

+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.

 

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.

 

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?

 

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.

 

two dynos with said turbo....






is nature of the turbo.

 

its a .64 exhaust housing, fwiw.

 

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...

 

Try a helper spring on the wg arm - that reduced spool on my internally gated t3/t4 3-500rpm across the board.

 

which is the T3, which is the SR20 T25?

 

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.

 

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?

 

NOS yo!