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Internal Mods For More Torque From A Rb25

The Bogan

By The Bogan,
in Engines & Forced Induction

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The Bogan Grand Master

The Bogan

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To go the 30 would mean more $ for modding, ic piping, exhaust and dump, oil pump, waterpump, plus more machining costs.

The only thing cheaper was the piston cost.

If i was just looking for big numbers the 30 would be the go but im not.

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bubba Grand Master

bubba

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To go the 30 would mean more $ for modding, ic piping, exhaust and dump, oil pump, waterpump, plus more machining costs.

The only thing cheaper was the piston cost.

If i was just looking for big numbers the 30 would be the go but im not.

Umm, why more costs? is this what the guy you want to build your engine said?

Are you not putting a decent oil pump and a new water pump in there anyway?

The only difference in machining costs would be getting a spot for the tensioner drilled/tapped and maybe oil/water fittings if a non turbo block.

Why are the pistons cheaper? was he going to do you a standard non-turbo build?

30's aren't for big numbers, they're for people who want lots of torque/drivability. They do help if you do want big numbers though as you can spin up bigger turbos.

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MBS206 Grand Master

MBS206

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To go the 30 would mean more $ for modding, ic piping, exhaust and dump, oil pump, waterpump, plus more machining costs.

The only thing cheaper was the piston cost.

If i was just looking for big numbers the 30 would be the go but im not.

Um... Are you not the water pump and oil pump etc?

As for the dump, cut it and get 38mm longer added into it...

IC Piping, is usually change one pipe.

More machining? What more machining? Skim the head, deck the block... Are you not doing this on the RB25?

I had my head modified to retain VVT for my second head (DIdn't have it on the first, still torquey as hell down low) Cost me $20 to have the stuff welded, and tapped.

And has cost me $250 in external oil lines, but that's including doing oil drain mods, which you'd be HIGHLY advised to do on the RB25 also...

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bubba Grand Master

bubba

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I understand that, but it seems someone has given him the impression that building a 30 is cost prohibitive.

Do you actually have anything constructive to add?

Edited by bubba
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R33S2 Grand Master

R33S2

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Well yes I prefer to have a 25 as it is more than capable of producing huge power, the 25/30 conversion is fairly straight forward and I did consider it but in the end I decided that the extra mods (to everything) arent neccessary for what I want.

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maximajim Community Regular

maximajim

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Ive got all my bolt on,s done(i think :( ) now I'm going to have the internals done, what should i do to to maximise my torque down low.

Or have i got this wrong and just need to up the boost and tune it when she is rebuilt, I'm getting pistons , rods, bearings, head rebuilt and adjustable cam gear on the exhaust side, What else should i look at.

Ive got, TO4 High mount, Greddy inlet Plenum, 800cc injectors, FMIC, Link ECU, Greddy Profect B Spec 2, Bosch 044 fuel pump.

I don't want a Rb30 bottom end and will be using the 25 crank.

Ive searched around but couldnt find much on making torque only kw.(or are they hand in hand)

Thanks for your help.

Generally longer intake runners= more TQ, so your better of with the standard intake manifold rather than the greddy. You'd want to increase stroke as much as you can and also possibly the smallest turbo that can reach your desired power levels..

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The Bogan Grand Master

The Bogan

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I dont want more stroke, I dont want a 30, I dont want a 26, I dont want to change my bolt ons.

Im keeping my 25 bottom end.

I wanted to know if there were other thing i could do with what ive got to get more torque when i get it rebuilt.

Thanks to the 1 or 2 people who gave me some usefull info, you know who you are.

Sorry if I sound harsh.

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maximajim Community Regular

maximajim

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I dont want more stroke, I dont want a 30, I dont want a 26, I dont want to change my bolt ons.

Im keeping my 25 bottom end.

I wanted to know if there were other thing i could do with what ive got to get more torque when i get it rebuilt.

Thanks to the 1 or 2 people who gave me some usefull info, you know who you are.

Sorry if I sound harsh.

Why bother then?There's only so much torque you can get a from a short stroke 2.5ltr i6 without major changes. It doesn't sound like you want to do anything reasonable to increase TQ.

Edited by maximajim
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