Hi all as title says really, just looking for some graphs if possible to help a friend out

I'm still currently scrolling through the scoobyclinic billet thread but not come across one as of yet so though it may be quicker to ask here

Also be quite interested to see what its like, I bet it should spool like a bastārd

Cheers all

Craig

 

i am also interested in this. I think it will be good for 420-430 bhp and spool quick.

 

Tis indeed a good question!

I was in a similar boat and with the standard 257 liners was torn between a 46 with a conservative map, or a 42 let rip.

In the end i went for the 46 as theres not alot of difference in cost. Im massively impressed with spool and top end does exactly what it says on the tin! ..... However the same setup (ported headers, harvey trick up pipe etc) with a 42 would be bonkers, probably spool from idle!

 

i'd hazard a guess at the 430-440 mark but as its on the 2.5 i wouldnt want to "let rip". its sometimes running high boost on the 2.5 that causes failure. I'd go sc46 and run lower boost

 

depends on 2.5 spec, mines got forged pistons and uprated rods so gone for sc46 over the sc42.

 

When you say low boost what do you refer to "low" as?

As I would imagine a forged 2.5 to be running around 1.6bar ish maybe more, so if both turbos where mapped to the same boost what are we saying? As the 46 wouldn't be able to break in to it's stride if it was mapped to such a state of low boost, so surely it would be better to run a 42 and make use of the extra low down possible torque to get up and away than to have a 46 mapped for low boost and not so aggressive if that makes sense I know the 46 is an excellent turbo I'm not questioning that and there are many proven 2.5's with them on, but what kind of difference do you think you would see with a 42 for lower down boost, as the 46 is on song circa 3300rpm give or take dependant on spec so would the 42 make better progress so to speak.

 

This is something I would imagine the clinic or one of the mappers may have to answer as they are the ones who see this stuff day in day out. Drop the clinic a call and see if they could forward you a graph or two of a sc42 and sc46 on a built 2.5ltr.

I am with your mind set, surely where the sc46 as you say hits boost at 3300rpm I would imagine the smaller sc42 should come in say 3-500 rpm sooner? and although it won't make the 460+ bhp, the 420-440 they make is plenty good enough on the road.

 

I'm trying to make this decision myself.

The problem is the technical minded are going for and pointing me towards the SC42 as its going to be a road car.

The other problem thing is the things that hang between my legs keep pointing me towards the SC46.

I think the additional problem is, you can keep searching and asking till you get the answer you want and not the answer you need

 

I don't run this set up but a 420 vs a 450
With a billet 46 I don't think there will be much diff in early spool running correct headers & up- pipe to match . Peak torque is pretty low down so I think all you will lose is a higher bhp figure using the 42
That's my guess , I await testament

 

That would suit me as the car I bought has a 46 on it yet I'm still curious to know from the likes of owners but more importantly the clinic as they will have back go back testing as results Could vary as different built engines may have different characteristics etc. I've popped a link up in the billet thread to see if someone from the clinic can shed any light on the subject.

 

This is exactly the same position I'm in, infact my sti is at api getting forged as we speak.

David sugested as its is pretty much only going to be a road car that the sc42 would be the more practical option, and I know I agree with him really. But heart still wants the 46!! Lol

Just to "throw a spanner in the works" have you checked out BIG FUD's spec c? (His graph is in the scooby clinic turbo section) he's running a built 2.1 with a twinscroll sc42 and making over 500hp with meth,I think 448 on Vpower. I'm pretty certain i read somewhere the hawkeye sti has the twinscroll sump so the conversion wouldnt be too much of a ball ache. I converted my bugeye wrx to twinscroll and I swear it's worth it for the noise alone!

Just my half a penny.

Tom

 

Mine is currently running a sc42 on standard 2.0 and its spools up nicely, with meth mine made 471bhp with 430lb tq. Full boost is around 3800rpm and its mental, so if you run this turbo on a 2.5 engine, I think that's gona spin up all four wheels around 3000rpm!

 

ignore headline figures, essentially the bigger turbo on a 2.5 will give you a lot more around 6-6500rpm where the 2.5 power curve drops naturally, so the 42 makes for a better road car, the 46 if you want the best for track and 1/4 mile.
Trev

 

Heres my 46 on a 2.5, by conservative boost i mean 1.5bar.

Great spool on the road, nice power for the track.... highly rated!

I held back the boost mainly to protect the liners as thats the weak link on the 2.5's .... forged pistons, standard rods, standard crank are all good, but the liners are the limit. (i assume your already 6spd?)

 

We have used 2 or 3 SC42's on 2.5 and have been very impressed with the result In fact I told Kev at the Clinic how good it was and he was going to knock up a test rig to get the data and see what l was going on about.

It does take the brute sting out of a 2.5, which not every one wants and in the case of the Legacy Blitzen we did, made up for the excess weight. The 46 struggled to spool decently when Bob R mapped it due to the sheer luxury it was trying to drag along .
SC42 fixed that and my customer is a very happy man.

In certain applications it is the better choice.

David APi

 

Thanks for that David, don't suppose you got any graphs have you of one in action?

I think this may get a few people thinking about it, as like said above how often can you use the full power of the 46 on the road? So my logic behind this is that the 42 as said would make a much better point to point car if that's what your wanting for the odd B road blast etc, its still not gonna be a slouch by no means top end either, but how often are you going to be running a road car on its limits, not too often IMO.

I've just shown this to one of my mates who's after a 2.5 and now I've got his mind ticking

 

I don't have a printout sorry, maybe my customer does, but we lost the hard drive on the rollers with all the data as well a while back and have just got Dastek [ bunch of turkeys ] to rewrite it, Seems they NEVER supply driver discs, if you lose your software, it 's back to them.
BUT the shape of the graph above [ I KNOW ITS A 46 ] loloks very similar from memory. I believe we saw 430 odd

David

 

Whichever turbo you go for, id highly reconmend the harvey up pipe for improving spool!

 

I've been running SC46 first on my 2.12, and now I run on on my built 2.5
I would not go any smaller than SC46, spool (while similar on both due to 79mm crank) is amazing, power is good. I might add some cams in the near future and tune the hell out of it, see what it's really capable of!

 

Totally agree already one on there with ported headers, made a noticeable difference when mapped

Need someone who is running a 42 to pop along now with some graphs and info

 

^
Remembering also if your running ported oem with Harvey's 2 bolt
& your chasing mid 400's
It would be advisable to use tubular with Harvey's 3 bolt

Vodka
Cams will make the 2.5 torque brutal
Just remember the liners are on limit at about 480

Good call tho