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Rb26 Inlet on RB20DET ?

discopotato03

By discopotato03,
in Engines & Forced Induction

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discopotato03 Grand Master

discopotato03

Posted
  • Author
Posted

Excellent , I'd like to hear how it goes . I may have found an R32 25 lower half to work with . I gather you cut it off out past the rail mounts and weld on plates to match the throttle bodies profile , then drill and tap the through bolt holes , make port holes then bolt it up .

Chow A .

  • 3 weeks later...
Munro Experienced

Munro

Posted
Posted

Well I would like to throw a spanner in the works here.( have not read whole thread, but noticed comment about single throttle conversion)

Any modified car, no matter what it is, is only as good as it's weakest link.

If a car is setup for a particular purpose then compromises are made.

I am by no means an expert in these matters, but would like to add my opinion.

Often I have seen (& driven) modified cars that have been built with "killer" parts lists that "on paper" should kick ass. BUT, they have not been greater than the

"sum off the parts", in other words, they have been built with all the "name" bits & pieces, but the overall application has been overshot in some areas.

Massive top end power is totally useless on the street if mid range torque is sacrificed to find it. If you are building a drag car then it doesnt matter, but the street is where it's at.

For example - the latest engine build on my street GTR (& I hope it's the last) has been a realistic downgrading so I can actually use it on the street. I reluctantly swapped the HKS step proL 288 cams for a pair of much more sensible 272s.

With the 288s, the car was a total pig in traffic off the line & couldn't even sit happily at 60 unless I kept it in 2nd or 3rd gear. Now the car has much better bottom end response, still will pull well into the revs, & I can use the car.

It does has a single throttle conversion(85mm), & with the single turbo, custom valves, conservative tune at 1 bar on PULP, it makes 375rwkw(500hp) & is responsive, well behaved & just what I wanted.

Big number parts are fun to talk about, but what we all want is a reliable, fast street car. If a single throttle conversion is done in conjuntion with the RIGHT parts

and tuned accordingly then it CAN be an advantage.

I have seen articles on Jap GTRS that run low nines still using the original 6 throttle bodies & a std plenum!!! So go figure!

Munro Experienced

Munro

Posted
Posted

At the drags, who cares about mid range.

The race GTR has a single 100mm throttle body & 292 cams.

Boost will start around 6500rpm.

The engine is built & the car is nearly finished.

So close, yet so far away.

Cant wait to get it finished. Been a long time between drinks.

And I like a drink as much as the next guy!!!

discopotato03 Grand Master

discopotato03

Posted
  • Author
Posted

I started this thread so I'll put it to rest . My original drama with the RB30 DET was clearence of the inlet manifold and the throttle body facing the wrong way . I guessed wrongly that the RB26 head and inlet system would cost a motsa . Since the RB26/30 have the same bore size and coolant passages getting the 26 head on a 30 block is easy (don't forget larger dia head bolts) . So for what I consider very reasonable money I bought a complete RB26 head/inlet system . So in other words I have the best performing factory option which solves the above probs as well . If I had grafted the GTR inlet system onto an RB25 (R32) head along with the GTR cams and springs it would have cost more for less performance . Also not having a RB25 bottom end to trip over helps .

Cheers A .

Sydneykid Grand Master

Sydneykid

Posted
Posted
I started this thread so I'll put it to rest . My original drama with the RB30 DET was clearence of the inlet manifold and the throttle body facing the wrong way . I guessed wrongly that the RB26 head and inlet system would cost a motsa . Since the RB26/30 have the same bore size and coolant passages getting the 26 head on a 30 block is easy (don't forget larger dia head bolts) . So for what I consider  very reasonable money I bought a complete RB26 head/inlet system . So in other words I have the best performing factory option which solves the above probs as well . If I had grafted the GTR inlet system onto an RB25 (R32) head along with the GTR cams and springs it would have cost more for less performance . Also not having a RB25 bottom end to trip over helps .  

Cheers  A .

The right decision A, let us know how it goes. :D

kwazza11 Rising Star

kwazza11

Posted
Posted

this thread's got me thinking about what i should do when my motor goes back together.

ATM i've got an rb24det with standard bolt ons but to go back on it, is a k27, trust manifold and gate and a modded GTR manifold. mines alittle bit different though, its had the rb20det runners cut before the injectors and the gtr manifold has been cut and rewelded to erase the 6 throttles and keep the injector holes (uses 12 injectors, 6 gtr and 6 rb20), then the standard throttle has been mounted on the front.

now you've got me thinking i should leave the standard manifold on and dont worry about throwing the gtr manifold back on, do you think zoom lost all that power from the 6 throttle setup, or the whole design of the manifold (shorter runners, plenum size etc)?

Sydneykid Grand Master

Sydneykid

Posted
Posted
this thread's got me thinking about what i should do when my motor goes back together.  

ATM i've got an rb24det with standard bolt ons but to go back on it, is a k27, trust manifold and gate and a modded GTR manifold. mines alittle bit different though, its had the rb20det runners cut before the injectors and the gtr manifold has been cut and rewelded to erase the 6 throttles and keep the injector holes (uses 12 injectors, 6 gtr and 6 rb20), then the standard throttle has been mounted on the front.  

now you've got me thinking i should leave the standard manifold on and dont worry about throwing the gtr manifold back on, do you think zoom lost all that power from the 6 throttle setup, or the whole design of the manifold (shorter runners, plenum size etc)?

I think 2.4 litres compared to 2 litres (as per the Zoom test) will make a lot of difference. The GTR inlet system is designed for 2.6 litres, so you are not so far away from its design parameters. I reckon it's a goer and you should use it. :D

I have a question though, why did you go away from the mutliple throttle bodies?

kwazza11 Rising Star

kwazza11

Posted
Posted
I have a question though, why did you go away from the mutliple throttle bodies?

it was done in japan, to be honest i dunno why they did it! probably wanted the 6 extra injectors more, or mabye they did the same as zoom, tried it with them on, saw a loss so went to a single throttle?

:headspin:

kwazza11 Rising Star

kwazza11

Posted
Posted

well think about it this way.. you can either get an rb25det from a 33 thats done probably 80,000 ks or you can build a fresh motor with .4 of a litre more (than the rb20). personally i'd prefer the fresh motor with Tomei forgies!

but on another note the cars 16 years old with 60,000 kms, so it could of been done back in the 90's when rb25s were still fairly new and pricey.

anyway i've got the best of both worlds! a huge turbo and a stroker! :headspin:

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