Rb26- Enlarging Std Throttle Bodies

[sucram]

It will give gains, but you wont hit 600

5 hours ago, Predator1 said:

bump.

Anyone had this done? either 49 or 50mm? Been pondering what to do while mines in storage. Been thinking of DBW but if I do that, then might as well do this too. Want to retain 6 throttles.

I have a fully build head(CNC, OS valves, 286/278 cams, etc etc still running squish), and a Greddy old school intake with port matching.

Head bench flowed 300cfm. Wondering whether bigger throttles will give me any gains. Makes 563kw.

It will give gains but it wont get you to 600 imo. You will also sacrifice low down and you will be adding extra volume if you port match it, more so if you port the plenum runners depending and how its done

I think the only time youre going to see about 100hp gains is if the car is making well over 1k kw

I do have a spare set that I was going to test with, but i dont actually think there is anything worth getting going larger. I did a fair few S14/S15 and the standard TB is fairly small, I went to 60 and in some cases 64mm which is significant over the stock unit. You can also get some weird ratio changes. I think 20kw will be a stretch on a roller dyno. If I had it apart I might mill the shafts a little and not expect much, I think the stock size is still pretty good for a street/track car even with larger capacity. I might change diameter it if its a drag only car

[LaurelPWR]

On 14/3/2025 at 6:09 PM, Predator1 said:

bump.

Anyone had this done? either 49 or 50mm? Been pondering what to do while mines in storage. Been thinking of DBW but if I do that, then might as well do this too. Want to retain 6 throttles.

I have a fully build head(CNC, OS valves, 286/278 cams, etc etc still running squish), and a Greddy old school intake with port matching.

Head bench flowed 300cfm. Wondering whether bigger throttles will give me any gains. Makes 563kw.

Hey mate, thread dredging hahah

To answer you directly, yes I had my itbs oversized and custom butterflies etc made by EFI Hardware in Sydney back around 2017-2018 if memory serves.

My setup had a vast amount of other changes too though, so no direct comparisons unfortunately.

i went from oem itbs, HPI manifold and internal gate hks 2835 pro S;

to 49mm itbs, cnc port matched Nismo plenum, RB25 Neo lower runner adapter hand port matched, r31house v2 Takoashi MAX equal length twin scroll manifold with twin 38mm tial gates and a FP HTA3076 with 1.01ar twin scroll real hosing.

feom power Fc to a link fury wired by 12volt, r32 gtr fuel tank conversion with frenchys twin 460 / surge tabk fuel hanger combo kit, 1659cc injectors, full 4 inch turbo back stainless exhaust, Z34 6 speed, Tomei 2way with 4.3 final drive and a ton of other shit.

ive posted elsewhere here with complete run down, but here's a graph from its initial tune with no boost control on, 20psi gate springs only and e85.

 

Edited 12 hours ago by LaurelPWR