Gerald81

I recently swapped my VF42 out for an SC42. The before and after dyno charts are attached.


It seems strange to me as, although the power is up as expected, peak torque is lower than before. It also comes in at a higher rpm which is probably expected for a larger turbo, but I'd thought the SC42 billet should be relatively quick-spooling.


Another thing is the power delivery now seems to be increasing all the way to the redline - is this normal? It almost looks as if the turbo is too large for the engine. I guess the comparison between the VF42 and SC42 is not helped by the fact that the VF42 was logged in 4th gear whereas the SC42 was logged in 5th.


The engine is a 2.1L stroked up GRB engine, which was originally dual AVCS but since my car is originally a single AVCS 2007 STI, the AVCS exhaust cams are run in a fixed setting. Not sure if this compromises anything compared to a factory single AVCS engine?


Other setup notes: 4032 Mahle pistons, stock twinscroll headers and uppipe, 3" turbo back, stock intake and TMIC.


What do you guys think of the SC42 dyno chart?

SmurfyBhoy

Road Dyno vs Real Dyno of my SC42 tinkered by OD on my stock 2003 STI

Also have it now on Ethanol 20%

Road dyno with same settings claims 466 so if out by same margin its now around 430 ish

Gerald81

Thanks for sharing!


If I'm reading it right, before adding ethanol, you were hitting peak torque at between 4500rpm (dyno) to 5000rpm (road)?


And after adding ethanol, peak power and torque are both higher but peak torque is still only coming in at around 5000rpm? I would have thought the ethanol would help it spool faster.


Also I'd always thought the SC42 typically delivers peak torque between 3800rpm to 4000rpm?

SmurfyBhoy

Don't get hung up up peak figures,

Comparing just road dyno data to save any confusion -

On Ethanol (Red Lines)

It makes more power and torque right through the rev range,

V-Power (Blue Lines) "Peaked" @ 384 @5081rpm

Ethanol makes that same figure @ 4500 (ish) rpm & goes on to peak at similar rpm.

SmurfyBhoy

Comparison for same settings on Road dyno + same shop Dyno

With VF35 turbo



And for an easy comparison of the 2

My VF35 data with V-Power SC42 together

You can see that before 4500RPM the VF35 pulls alot harder but gearbox fixes that.

My SC42 has been machined for bigger billet wheel by Owen Developments and has 8cm exhaust housing so not really suited to a stock 2.0 but when it gets goin it's fun




What I can say tho is the SC42 is less laggy

The VF35 has lower boost threshold

Gerald81

Thanks again for sharing - I just realized yours is a single scroll setup, and since your SC42 has a larger than standard hotside, it does make sense in terms of the power delivery.


However mine is a twinscroll and also given the engine is a 2.1 stroker and my SC42 has the standard hotside, I was hoping it would spool a bit quicker.


Since my old VF42 and new SC42 logs were done in different gears, I tried to manually overlay them in the attached picture. Basically what I can see is that the SC42 hits full boost later, with lower maximum torque, but makes better power at higher rpms (>5500rpm).


I know what you mean about not getting hung up on peak numbers, but still isn't it strange that my SC42 would have lower peak torque compared to my VF42? In your dyno plots, it seems that the SC42 outpunches the VF35 in peak torque (as one would expect).

SmurfyBhoy

I see,

Yes i would have expected it to follow the same gains as mine

Lose some bottom end torque,

For a higher peak with a higher torque figure,

Yours doen't appear to be following that trend

bustaMOVEs

iTrader: (31)

A bigger turbo will obviously have a bit of lag, but the sc42 should see full boost just before 4000rpm or there and more so on a TS.

Smurf, is that your 42 on meth at 466hp?

SmurfyBhoy

Yea its the road data from the 20% Ethanol setup

It's not really much in common with Sc42 other than outside looks of compressor housing,

Infact i think it's a Blouch because AFAIK SC had 7cm housing

Mine is 8cm

Also re-machined to fit bigger 73HTA billet wheel with metal caged bearings and heatshield by the guys at Owen Developments

Bit of a Frankenturbo and not at full potential on a stock 2.0


Also folk confuse lag with boost threshold



Mine has less lag but 1000 rpm Higher Boost Threshold than my VF35

EG.

Both setups sitting at 5500rpm (well inside VF35's boost threshold)

SC42 will hit full boost quicker = Less lag

The SC42 not spinning at 2500rpm isnt actually lag by definition

Your outside the boost threshold

Gerald81

Do you reckon it could be due to having the exhaust AVCS in a fixed position? Could it have that much of an impact on turbo spool? The intake AVCS is still controllable.

SmurfyBhoy

I'm sure mine being the 2003 mine only has AVCS on Inlet

would still have some effect tho i imagine

Gerald81

Yup what I meant is, would running the AVCS exhaust cam in a fixed position make it perform WORSE than a non-AVCS exhaust cam? Meaning my setup, which is effectively single AVCS, would perform worse than a standard single AVCS engine?