Power advice

[zero260]

I am very new to the S15 scene and need to know some basics when it comes to up'ing the power on my Spec-R safely.

The car is completely standard so I am looking at doing the usual basics like 3" full Exhaust system, turbo elbow, front mount, air filter and a remap. But before I do anything:

What power gains will I get from the above mods?
What is the limit on standard internals?
Is the ECU mappable? or do I need a power FC or something similar?

I hope someone can help in giving me the basics and also please feel free in giving any other info you think I could do with knowing.

Many thanks and I am looking forward to your advice.

 

[LuPix_S15]

Hiya mate and welcome to S15 ownership!!


With the mods you mention above you won't get very far without some sort of boost control in order up the boost etc. Stock runs about 0.7 bar but you'll want more than that once the cooling mods are in and it's safe to turn up the boost The list above is a good start but also make sure you get the Walbro 255 fuel pump upgrade sorted before you go for more power.

In my experience, I've got what you mentioned above plus fuel pump and electronic boost controller and running to 0.9 bar with Apexi Power FC remap. Cos it's been done safe without maxing out injectors, the top end is not above 250 bhp which is stock power. But I get a hell of a lot more power and torque in the mid-range

But if you wanted to push the limits from an early stage, I reckon you should see near 300 bhp if you wack the boost up to 1.2 bar or thereabouts. Just depends on whether you are comfortable with the car leaning out etc.

From then on, I'd say a set of 740cc injectors plus Z32 AFM and possibly fuel pressure regulator will get you to nearer 330 bhp but by that point, the stock turbo is really running out of puff so boost will deffo tail off at 1.2 bar and above.

Then we're in turbo upgrade territory, cams etc.

I'd say from what others say (not from experience) that stock internals are good for 400 bhp but it's the gearbox that's the weak link and going past 350 bhp is a worry for a lot of stock gearbox owners.

ECU can be mapped cheaper by using Jez's chips which come highly recommended. Take a visit on the web to 'Horsham Developments' or search on here. Power FC is fully mappable and I'm loving mine long time!!

HTH

James

 

[zero260]

I forgot about the pump, but the AFM's, injectors and fuel pressure regulator may be the order of the day as well as that power FC.

Either that or a RB26 lump.lol, that will have to wait till next year.

Many thanks for your advice bud.:thumbs:

 

[LuPix_S15]

TBH mate - from what I can gather the RB26 lump is not worth ploughing money into unless you are really serious about 400+ bhp. The SR can cope pretty well up to that point as it's strong enough with the right mods

It's just that for all the money spent on a transplant (and the RB is a decent choice), one should only consider this for serious horsepower applications. If this is your plan then fair play lol


No worries - helping and providing advice is what it's all about on 'ere :thumbs:

 

[DeanS15]

i ran 1.2 bar on the standard turbo with no injectors or z32 afm with no problems, in fact it was a very nice setup. the standard clutch should hold at this level - mine did and i suppose it was approximately 310bhp atf. the injector duty was high, but the turbo/afm/injectors are all pretty much at thier absolute peak then and the only way forward from there is to start uprating them. as said next step is new blower, 740cc nismo injectors (may as well, 555's arent any cheaper), z32 maf and to make the most of it uprate the head gasket and head studs with maybe a cam kit thrown in the mix for good measure - uprating the clutch with these mods is a must :nod:.

 

[zero260]

Thanks again guys. To be honest I have only ever driven a standard one so I have no idea what they are like at around 300 to 350hp. The scoob I had was at 372hp and 390lbs, the skyline before that was at around 700hp and evo before that was at 450hp. I am trying to achieve a nice drive with a nice punch, with smooth delivery, something very similar to what I had in the scoob where everything it did have went to the road.

I am thinking if I had around the 320hp mark (for now.lol) I would have something very nice to drive.

 

[Dan_Harris]

just on this note what sort of power can the stock box/turbos cope with? and whats the realistic power your can push the SR20 to before the RB becomes the better option?

 

[DeanS15]

standard turbo 330bhp ish
standard box significantly weakened after 350bhp (imo)

 

[LuPix_S15]

^^^ +1

But remember when you're pushing the stock turbo to the limits 1.2 bar etc there'll most likely be boost tail-off at the top end cos it can't cope with the flow


I'm really happy with mine and it's only had power and torque increases in the midrange but the S15 being such a light car, the PTW transformation is significant when you only up 50 to 70 bhp from stock so it's very noticeable!!

 

[LuPix_S15]

Remember to factor brakes and suspension mods as well lol!!!

 

[Dan_Harris]

so what gearbox options are there once you start approaching 400 then?

 

[DeanS15]

so what gearbox options are there once you start approaching 400 then?

not a lot :wack:

secondhand 6 speed - will break again eventually
z32 - bit of a bodge - gear stick position, open portions of bellhousing making it noisy
rb25 - bit of a bodge, as above
os giken 5 gear kit in s14 box - expensive and apparently quite noisy
nismo strengthened 6 speed box - mega expensive and not really proven
then theres
standard s14 - no stronger than s15, but cheaper to replace when it breaks, what i'm considering now as a spare would only cost around 250-00 for a good one and is far more widely available.

i'm actually getting annoyed with 6th gear now and starting to wonder whether its absolutely neccesary other than on long motorway journeys for fuel economy only, it loads the engine up something chronic at anything under 70mph and is way too tall to be truly useful.....

 

[Dan_Harris]

so i'm guessing it's at this point where it's a better option to go RB26 and be done with it or 2JZ as driftworks did

 

[DeanS15]

if i was going to swap the engine, which i will eventually, i'm going to ditch turbo altogether and bung in the corvette 6.2 ls2 v8 and tremec t56 6spd gearbox - fits well, 380bhp standard, close to 500hp with a cam change and not weak:nod:

 

[zero260]

Remember to factor brakes and suspension mods as well lol!!!

That brings me onto another question.

What coilovers? I was toying with the idea of BC coilovers as they were so good on my Scoob.

 

[DeanS15]

i cant comment from my own experience on the apex coilovers as i run tein flex which are very good imo - as far as i know apex performance are the main dealer fo bc coilovers and from what i gather thier own gen2 coilovers are rebranded bc's. lots of people on here run the apex coilovers and they are apparently very good for the money:nod:. if you are a member of the sxoc and are quick, they currently have a group buy running whereby you can get the gen2 coilovers for 486.75 as opposed to thier normal price of 649.00, then its just a case of selecting the right spring rate for your intended use. here is a link to the page which contains a lot of information about them and the list to join the group buy, it might be advisable to call apex too just to see if you join in at this point....

hope this helps buddy

 

[LuPix_S15]

I've only heard good things about BC coilovers. I run Tein Super Streets which are brill for fast road Make sure if you want drift/track spec coilovers with much harsher spring rates, you're prepared for some mad, bumpy journeys on the UK B-roads (and in some cases badly maintained A-roads!!)...

AS said a lot on here run Apex suspension and Driftworks sell the HSD package which seems popular as well.

 

[zero260]

Thanks for the info on that sxoc group buy as I have managed to get on the list and get myself a set of the Gen2 Apex Coilovers. Also while I was at it I thought I would also go for the Apex type-1 front mount and a few other bits and pieces.:thumbs:

De-cat system next.

 

[DeanS15]

good stuff mate - type 1 is a good cooler and fits great. get a quick tap boost nipple while you're at it to make running the boost hoses a lot easier/better, they are only about 8quid:nod:

 

[zero260]

Will do.:thumbs:

Cheers.

Gav.