Twinscroll VF36/GT2871 hybrid dyno tune results

**unclemat** · #1: 12-20-2009, 07:16 PM

Ok, so I finally decided to take the car for a dyno tune at EFI Logics. Car was previously road tuned by a friend with excellent results, but Chris was able to extract some more power and make the car feel smoother. Btw, he is an excellent tuner and provides great customer service. Highly recommended.

Relevant mods: VF36 twinscroll ball-bearing turbo w/GT2871 compressor wheel (same wheel as in AVO380) w/15 lbs. AVO wastegate actuator, JDM STI twinscroll EL headers/uppipe, AVO catted downpipe, Perrin Y-mid with extra straight-thru Mangaflow muffler welded in, STI quad-tip cans, AVO CAI, Perrin inlet, 08 STI intake manifold/TMIC, TGV deletes, DW 740cc injectors, AVO fuel pump, Prodrive BCS. 08 STI 6MT transmission - 4th gear pulls on the graph.

The numbers are not too impressive, although this is not an optimistic dyno (stock STI puts 240 whp on it) - 292 whp peak (note the graph is corrected, it put 310 whp uncorrected, but it was pretty cold day, probably less than 40F in the dyno bay), but the power band is really nice. The car responds incredibly quickly and is a hoot to drive. Chris said something is holding the turbo back, likely restrictive exhaust (I wanted to swap the quad-tips for stright-thru Prodrives, but didn't have time to do it).

Dotted lines are the baseline, solid lines are the final tune.

The info has been also uploaded into their dyno database.

Comparison with 2008 SpecB stock (comparision should be made with SpecB because of the 6MT tranny):

And versus EFI's shop stage II SpecB:

And a comparison vs. an AVO380 on a 09 WRX (not clear what intercooler it used):

**Darkness of Death** · #2: 12-20-2009, 07:24 PM

that's not bad. the dyno i pulled on, an STi pulls only 198whp

why didnt' you pull on 3rd?

**unclemat** · #3: 12-20-2009, 07:29 PM

With the 6MT gearing typically the 4th gear is used in dyno tuning.

**Darkness of Death** · #4: 12-20-2009, 07:43 PM

i think my pulls were with 3rd (6mt)

**JoeFromPA** · #5: 12-20-2009, 07:45 PM

Looks like a beaut UM. It's showing peak torque hitting at ~3200 rpms....how big is this turbo compared to the JDM LGT twinscroll?

If I'm reading you right, you are hitting 300 whp on a twinscroll BB turbo with, essentially, an opened up exhaust, better inlet, CAI, and fuel support. No upgraded intercooler, pump gas.....?

Really nice.

Joe

**unclemat** · #6: 12-20-2009, 07:47 PM

The compressor wheel in theory is 44 lbs/min (20g size), but is limited by the compressor housing (stock VF36) and probably the exhaust housing. This is much bigger turbo than stock JDM LGT, even without the upgraded wheel. The stock wheel is VF39/VF52 size.

This is pump (93) gas. It has upgraded intercooler - 08 STI intake manifold and 08 STI stock intercooler.

**ScoobySTi07** · #7: 12-20-2009, 08:21 PM

Great numbers man.

It seems unlikely that the mufflers are the restriction but maybe. Looking at the rest of your upgrades I'm having a tough time seeing where the restriction might be. Could be the cat. Did you go with AVO's ceramic or metal cat? Does Boston require emissions tests?

**unclemat** · #8: 12-20-2009, 08:23 PM

Metal cat. But it's close to the turbo, so maybe that's not helping. I'll swap the muffers and have it retuned (also with alcohol injection, so we will see).

**ScoobySTi07** · #9: 12-20-2009, 08:40 PM

The metal cat is the higher flowing of the two but yeah you could still be seeing some back pressure build up especially with where AVO put the cat.

Have fun with the meth. Just don't blown anything up.

**unclemat** · #**10:** 12-20-2009, 08:41 PM

Quote:

Originally Posted by ScoobySTi07

The metal cat is the higher flowing of the two but yeah you could still be seeing some back pressure build up especially with where AVO put the cat.

Have fun with the meth. Just don't blown anything up.

Built engine + 6MT + ACT clutch. Should take it...

**ScoobySTi07** · #**11:** 12-20-2009, 08:49 PM

Should is always a fun word.

**LittleBlueGT** · #**12:** 12-20-2009, 10:03 PM

I am in for some road logs, I can learn more form them.

If you want to check back pressure in the exhaust, you can do it for about $20.

Get a MPT - barb hose adapter, some heat resistant hose, and a cheap pressure gauge (up to 15 psi for good resolution).

Then run the hose through an open window, in the car have the gauge, in the DP (where the O2 sensor would normally go) thread in the adapter.

Quickly go out and do a WOT run. I did this, and got in about 5 WOT runs before the heat killed the gauge. At WOT above about 4000 rpm my relative pressure in the DP was 4-5 psi. It was pretty consistent.

I don't know if that is good or bad, but it gives you a starting point.

**f1anatic** · #**13:** 12-20-2009, 10:35 PM

very nice numbers...and i bet no noticeable lag.

**unclemat** · #**14:** 12-21-2009, 07:35 AM

No, no lag, really, this thing flies. Full boost at ~2900k rpm in 4th. Even in 2nd or 3rd, punching it at 3k makes it take off right away.

**unclemat** · #**15:** 12-21-2009, 07:55 AM

Quote:

Originally Posted by LittleBlueGT

I am in for some road logs, I can learn more form them.

If you want to check back pressure in the exhaust, you can do it for about $20.

Get a MPT - barb hose adapter, some heat resistant hose, and a cheap pressure gauge (up to 15 psi for good resolution).

Then run the hose through an open window, in the car have the gauge, in the DP (where the O2 sensor would normally go) thread in the adapter.

Quickly go out and do a WOT run. I did this, and got in about 5 WOT runs before the heat killed the gauge. At WOT above about 4000 rpm my relative pressure in the DP was 4-5 psi. It was pretty consistent.

I don't know if that is good or bad, but it gives you a starting point.

Thanks. For some time I was thinking about getting exhaust backpressure tester. Just ordered

one

, we'll see what it reads.