JasonC SBB

GT2560
ETD shorty tubey manifold
BEGI custom divorced downpipe
Custom 2.5" exhaust with metal cat
VVT head, mild porting
VICS manifold
8.6:1 Supertech pistons
15 psi midrange, tapering to 14 psi at the top.

conditions: sea level, 31*C
SAE correction applied:



VVT produced large gains in torque.
15 psi likes more VVT retard than 10 psi.
Turbo didn't like moar boost. Gains were small beyond 15 psi, even in the midrange(!).

It didn't lose torque going down from 12.5:1 AFR to 11:3:1 AFR, and lost below that.

Note flat power from 6000-7300 RPM. I think this is due to VVT. Savington sees flat power with his VVT and Blox intake mani. I suspect it's due to VVT, not the mani.

160 ft-lbs @ 2450 RPM
200 ft-lbs @ 3500 RPM

I will miss that low end if I go to a bigger turbo.

18psi

iTrader: (76)

Very nice daily driver powerband

samnavy

iTrader: (7)

That **** is awesome, and should last forever.

JasonC SBB

dtalog

Savington

iTrader: (31)

Haven't I told you that this isn't correct before, Jason?

Purple line is my first built motor (84mm 8.6:1, BP4W head, GT2871R). Blue line is my second built motor (83.5mm 8.6:1, VVT head, GT2871R) with VVT at full retard.



Now look at the old motor vs. the new motor w/ VVT advanced under 4500rpm (huge low-end gains) and the Blox manifold installed (huge top end gains). VVT is at full retard from ~5000rpm up, just the same as it was in the blue/purple chart - if VVT were causing the top-end gains, they would have appeared in the blue/purple chart - but they didn't. The lighter lines under it are the lines from the previous visit, which was VVT and the Blox manifold at 14psi on 100 octane.



All four torque curves synthesized into one:



See how the torque curve extends flat to 6000rpm on both of the Blox curves, but the torque drops at 5000 on the stock manifolds? Now look at your torque curve - the torque drops at 5k.

VVT does not have any effect on high-end torque - the intake manifold makes that difference, and I've never seen any data to disprove that.

JasonC SBB

Ah cool, that explains things, thanks.

Anyone seen a bone stock dyno of a JDM or EUDM 2001+ motor?
The flat torque from 5000-6000 should be visible there too.

JasonC SBB

I started out having the same VVT angle vs. RPM curve, from 0 psi to 15 psi.
I used a curve that I had generated by logging AFR at 10 psi. I looked for increases in AFR, which topped out at a certain point.

So as I retarded the VVT curve at 15 psi, from the 10 psi settings I had before, I saw huge gains, up to a certain point. And then retarding by a further 4 crank degrees saw no change. I kept it there.

JasonC SBB

Its funny how the GT2560 will happily generate mid levels of boost from like 2700 to 3250 RPM, with a slow rise in boost and torque. Then suddenly at 3250 RPM / 160 kPa it turns the corner and boost rapidly rises to 200 kPa.

My 2560 makes 160 ft-lbs at 2500 RPM and 170 ft-lbs at 3000, which is more than Sav's 2871, then we both make 200 ft-lbs at 3500. And then of course the 2871 takes off after that.

JasonC SBB

BTW 262 tq at 202 kPa with a 1.8L yields:

72 ft-lbs per atmo per L. That's the magic number one has to hit.

JasonC SBB

Here's an interesting comparison. Ian has a GT2560 on a 99 head. We both have a VICS manifold. Note the same "turning the corner", albeit at 3100 RPM instead of 3200 RPM.
His spoolup on his 99 is better than mine on my VVT, and his HP droops above 6000 RPM and mine stays flat.



And then Hustler's 0.86 GT2860 :

150 ft-lbs @ 3000
195 ft-lbs @ 3500
Albeit with inflated dynojet numbers.

JasonC SBB

More comparisons against Ian's GT560 on a 99 head:

His 99 head spools earlier than my VVT, but my VVT holds power much better at the top:

(both have SAE correction turned on. Same shop same dyno, about a year apart)

boost curve again shows his 99 head has better spoolup; and I'm running less boost


Differences that may account for spoolup / topend power holding, aside from VVT head:
- ambient temps may have delayed my spoolup - 87*F vs 77*F (doesn't seem like much tho)
- I have an ETD shorty mani vs. FM mani (may explain better topend but not delayed spool)
- I have an exhaust cam gear, retarded 5* (crank degrees) - could help explain topend but should not delay spoolup

Faeflora

iTrader: (2)

Is this flywheel horsepower? The dyno chart at the top says it is flywheel.


You know, my 3071 does pretty much the exact same thing. Slow rise to 10psi then rapid rise to 25.

18psi

iTrader: (76)

same here:

3076 .82

Faeflora

iTrader: (2)

I see some SPOOOOOL nig!

y8s

iTrader: (8)

Jason,
What cam angles were you running right around spoolup?

JasonC SBB

Datalog of spoolup sweep, from 2200-4200 RPM.
I played with timing for spoolup, but ran out of time and forgot to check if VVT settings could produce better spoolup. I can check it on the street tho.

Bottom third of screen is cam angle, and wasategate duty cycle.


Note that the AEM displays VVT angle as degrees of retard. So 48* is max retard, and 0 is max advance. Right around spoolup, where the cursor is, I'm running at about 24*, so right in the middle between max retard and max advance. You will also see that the WG duty cycle is close to 100%.

JasonC SBB

It back-calculates it from the hub torque and gearbox/diff ratios. It does not attempt to add in estimated transmission losses. Thus it is "wheel torque", translated to the flywheel.

So does this VW / Disco Potato:
https://www.miataturbo.net/showpost....0&postcount=31

Slow rise to 3300 RPM / 150 ft-lbs, then rapid rise to torque peak.

hustler

iTrader: (6)

I need to cough up the coin and get a real dyno chart on a Mustang Dyno, instead of whoring that barrel-roller dyno chart. I bet the numbers would be a bit better for my car.

y8s

iTrader: (8)

I bet the cam angle accounts for at least some spool left on the table.

I run a lot of advance above 3000 and taper off as I get above 4000 and it makes a big difference in low end.

A lot = 38 degrees.

On my car it didn't make a big difference what advance I ran below 2500 but the dyno plot barely starts there so it's hard to glean any useful information.

were you at full retard above 6000 RPM? I get the same flat power curve from 6300 to 7k.

JasonC SBB

VVT through whole RPM range.
Hits full retard (48*) at 6400 rpm.