To 30/26 Or Keep The 26?

[GTRNUR]

What you need is one of these:

I had one of these CNCed to run a S15 turbo master cylinder, it makes it bolt straight on and the rod length is perfect, and the pedal feel is no different with my twin plate clutch, I have a Greddy Plenum and there is plenty of Room on my RB30

......RIPS now buys these off me for some of his builds.

If I had known you were selling them I would have considered this option. I looked at what you had done here on the GTR UK forum and decided that I wanted to keep the booster (in part because I was too lazy to move the brake booster to put in a billet adapter.

My solution was to use a smaller OD 5/8" clutch master cylinder, and then attack it with an 4" flapper disc to put a flat spot on it where it would have made contact with the greddy plenum. I have less of an interference issue to worry about too with my motor being 20mm taller than a rb26, not 38mm.

A last option would have been to make up a smaller billet clutch master cylinder. I started on that too but the above option was the easiest.

[sky30]

^^

What's "full boost", 10 psi or 25?

N1GTR put a set on his Rb30 and it was farking stupid. Any gear, any time, it was ON!

20psi plus.

Sounds good, has he posted results on here?

[XGTRX]

Point being were they similar sized turbo, which you say they are. I just find it hard to believe that with similar turbos the rb30 isnt faster, and has better acceleration out of corners than the rb26, are they both at same power levels?

Ive always wanted -5s on my rb30 what rpm do they make full boost?

Never said it wasn't faster of course it is with the turbos always on but the torque also needs a lot more throttle control out of very slow corners. Other than that through all the faster stuff the corner speed and exit is all to do with chassis and suspension, and tyres didn't matter 26 or 30.

But yes a big difference down low. Where you are pulling hard in 3rd you would be still be revving the 26 in 2nd.

[XKLABA]

Never said it wasn't faster of course it is with the turbos always on but the torque also needs a lot more throttle control out of very slow corners. Other than that through all the faster stuff the corner speed and exit is all to do with chassis and suspension, and tyres didn't matter 26 or 30.

But yes a big difference down low. Where you are pulling hard in 3rd you would be still be revving the 26 in 2nd.

I have/had two 26s, one in my 32 and one was in my 34, the 32 is stupid responsive and the 34 was quite laggy given its setup( to my standards anyway), I have/do track both cars and the better response is MUCH easier to control and much more predictable and is unbelievably easier to drive at normal street speeds, both where making within 20rwkw of each other and the 34 transitioning on to boost later in the rev range was alot harder to control coming onto boost at pace and no where near as nice to drive on the street

I have since built a 2630 for the 34 and have done so for a reason, if you are so worried about breaking drive lines then best you don't modify your car at all or even drive it hard cause any of that increases the chance of breaking stuff, a bit of mechanical symphony goes a long way as does knowledge of changing gears correctly

anyone that does modify there car like Paul, myself and many many others have, all realise that at some point the driveline is going to need the same sort of upgrading the engine got

[sky30]

A well built 26 at 350 to 380kw is bullet proof shifting under 8200rpm and in the gtr's sweet spot for the drive line around the track for the smart driver.

And if everything else in the setup is sorted not much will beat it in average speed and reliability.

Plus 26s sound better too

When i read that it sounds like thats what you meant.

Do you know how many rpm sooner the rb30 gets the -5s on boost compared to rb26?

[GTRPSI]

@ Suboy32, or anyone else who has built and used a spacer, how much heavier is the pedal without the booster with this conversion?

Reason i ask is because we are planning to lift the body with subframe spacers and keep the booster.

In our case we are running a JB 5700Lb pressure plate and i was a little scared about how heavy the clutch might be without the booster.

[XGTRX]

I have/had two 26s, one in my 32 and one was in my 34, the 32 is stupid responsive and the 34 was quite laggy given its setup( to my standards anyway), I have/do track both cars and the better response is MUCH easier to control and much more predictable and is unbelievably easier to drive at normal street speeds, both where making within 20rwkw of each other and the 34 transitioning on to boost later in the rev range was alot harder to control coming onto boost at pace and no where near as nice to drive on the street

I have since built a 2630 for the 34 and have done so for a reason, if you are so worried about breaking drive lines then best you don't modify your car at all or even drive it hard cause any of that increases the chance of breaking stuff, a bit of mechanical symphony goes a long way as does knowledge of changing gears correctly

anyone that does modify there car like Paul, myself and many many others have, all realise that at some point the driveline is going to need the same sort of upgrading the engine got

Agreed with everything you have said, and you can set up a 26 correctly for response as you have suggested which does make it quite capable around a track.

And I am not suggesting that you cant break the driveline...but you are far less likely than an engine with more than double the torque down low applying so much more force to the driveline to overcome vehicle inertia, so you cant use a $700 gearbox like I can.

look at the guys running v8s or vls or xr6Ts, they are always twisting drive shafts and breaking diffs if they hook up especially now with G6s they are ripping out the zf gearboxes and putting stalled T400s in them and only making 450 kw but the torque is huge.

My view is that if your the average jo bo that wants a gtr as a good reliable allrounder, with spending $25k you can have a well sorted 350kw responsive 26 setup with decent handling upgrades that you can drive at the track and drive everyday.

Can I ask you what gearbox are you using now and is your 34 significantly quicker than a 26 that has its handling well sorted, and is the 34 street driven regularly.

When i read that it sounds like thats what you meant.

Do you know how many rpm sooner the rb30 gets the -5s on boost compared to rb26?

dont know but they are always on .XKLABAwill probably be more accurate

[XKLABA]

Agreed with everything you have said, and you can set up a 26 correctly for response as you have suggested which does make it quite capable around a track. more so, the 32 runs 15psi on the track which gives about 250rwkw vs 20psi on the 34 giving 313rwkw with the old setup which has better tyres-brakes-suspension and is 2 seconds slower around wakefield and about 8 around EC, that's the difference torque and response makes

And I am not suggesting that you cant break the driveline...but you are far less likely than an engine with more than double the torque down low applying so much more force to the driveline to overcome vehicle inertia, so you cant use a $700 gearbox like I can. that is right but if you want to make your car stupid fast then you have no choice but to upgrade the box and anyone that pushs their car that far knows that they are going to have to do the box, it's the only way to get the car that fast, so it really comes down to how fast you want to go, driving style has as much to do with broken boxes as power, I have seen stock cars break boxes just cause the driver is clueless

look at the guys running v8s or vls or xr6Ts, they are always twisting drive shafts and breaking diffs if they hook up especially now with G6s they are ripping out the zf gearboxes and putting stalled T400s in them and only making 450 kw but the torque is huge. oranges and apples really, you can't compare the GTR to a ford/holden as far as drive line goes, the engineering in the GTR is completely different and is so for different reasons

My view is that if your the average jo bo that wants a gtr as a good reliable allrounder, with spending $25k you can have a well sorted 350kw responsive 26 setup with decent handling upgrades that you can drive at the track and drive everyday. my 34 had poncams -7s and the normal supporting mods making 313rwkw@ 20psi and the difference in response between it and the 32 was massive, throw another 35+rwkw at it will mean going -5s so you don't have to run massive boost to get the 350rwkw which will make the 26 even less responsive and even slower around tight tracks unless your prepaired to rev the shit out of it which brings on another problem, syncros don't like big revs and having the to speed match gears with that much difference in gear speeds

Can I ask you what gearbox are you using now and is your 34 significantly quicker than a 26 that has its handling well sorted, and is the 34 street driven regularly. still the Getrag ATM but will either do the PPG set or bite the bullet and get the OS88, the 30 with GT-RSs so far responds like the 26 with -7s, just alot more drive off and on boost and even with 7psi it felt faster the the old setup, and was running around with the old tune, I have just completed the fuel system and changed the computer but haven't had it tuned yet, hopefully next week, and yes daily driven

dont know but they are always on .XKLABAwill probably be more accurate in my 34 I think the RSs respond like -7s on a 26 so the -5s IMO would be like my 32 with stock turbos just with a puck load more power

[Piggaz]

When i read that it sounds like thats what you meant.

Do you know how many rpm sooner the rb30 gets the -5s on boost compared to rb26?

He only did one run off actuator pressure then turned a bearing but it was 15 PSI at 3000 RPM where as the RS's were 1200 RPM later. SPewing he didn't had it all wound up. On the road he said it was just silly, boardering on insane. Look at the throttle and the boost needle is flying around.

[sky30]

When i read that it sounds like thats what you meant.

Do you know how many rpm sooner the rb30 gets the -5s on boost compared to rb26?

He only did one run off actuator pressure then turned a bearing but it was 15 PSI at 3000 RPM where as the RS's were 1200 RPM later. SPewing he didn't had it all wound up. On the road he said it was just silly, boardering on insane. Look at the throttle and the boost needle is flying around.

Sounds good, mite even be slightly more responsive than my hta3586 which is 20psi at 3200-3300rpm.

Was that on stock manifolds?

Ive always thought about the -5s on mine for a stock looking engine bay.

[Piggaz]

Sounds good, mite even be slightly more responsive than my hta3586 which is 20psi at 3200-3300rpm.

Was that on stock manifolds?

Ive always thought about the -5s on mine for a stock looking engine bay.

Stock manifolds, cams that were too big and a small exhaust and on first pull on the RS tune, so there was ALOT more left in it.

[sky30]

What do you call too big?

[Piggaz]

270's.

[XGTRX]

XKLABA: do you know how much faster you are lapping Wakefield with the 26/30? Valuable to draw comparisons for everyone. Thanks.

[sky30]

270's.

Any idea of lift?

[Piggaz]

Any idea of lift?

10.25

[XKLABA]

XKLABA: do you know how much faster you are lapping Wakefield with the 26/30? Valuable to draw comparisons for everyone. Thanks.

Not yet, still have to have it tuned, the car did a 1.09 on the old setup but with some more correction of the setup and better suspension and tyres I think a high 1.06 wasn't out of the question, with this setup I would like/hope to see a flat minute which I believe will be possible once it all finished

[Sub Boy32]

@ Suboy32, or anyone else who has built and used a spacer, how much heavier is the pedal without the booster with this conversion?

Reason i ask is because we are planning to lift the body with subframe spacers and keep the booster.

In our case we are running a JB 5700Lb pressure plate and i was a little scared about how heavy the clutch might be without the booster.

I didn't notice any difference in pedal feel going from the factory master to the S15 turbo one on my Nismo Dual Plate Coppermix Clutch.....but then it is a bit of a softie anyway. I haven't tried it with any other clutches, I'm not sure what RIPS uses when he gets the adapters off me.

[Country Cruzin]

Q. i'm currently needing a rebuild, an only bn to one happy laps in the 5n a half years ive owned the car. An yes I do like to listen to my car sing to 8000 before changing gear n not running out of puff.

currently have a rb26, -5's n 270 cams. but as its my weekend driver (when its going) it can be a lil annoying with lag round town. Im glad someone pointed out some of the head aches of a 30/26. I know drag 32/26's will happily rev to 9000+ but a purpose built. I'm not after super quick laptimes...

I know a 30/26 would fix down low problems, but worried what the difference is from 6000-8000rpm, as ive spent time in an xr6 turbo, an no lag is great, but just got more boring towards the limiter the harder u revved it instead of getting more exciting, didn't seem right. an maybe I should get out more an go to more skyline meets, but how bad can a 30/26 sound

[r32-25t]

An rb30 will rev to 8 without an issue, the fact that you need to lower the factory redline is a myth