Rb30det With A Cr Of 9.0:1 ?

[GTR_Junkie]

Hi Guys,

Im building my engine and i was wondering if anyone has built an RB26/30 engine using a CR of 9 or close to 9?

My engine mods are:

Top End

--------

RB26 Head fully serviced and mildly ported

HKS 272 Step 1 Cams

HKS Cam Gears

Bottom End (fresh rebuild)

-----------

RB30 Bottom End

Forged H-Beam Rods

Forged Pistons

O-Ringed Block

ACL Race Series Bearings

Oil Pump Drive Collar

R33 GTR Oil Pump

Oil Restrictors for the Head

Fully Balanced

Intake/Exhaust

------

Garrett T04Z 1.00 Rear

6Boost Manifold

XTR 55mm Wastegate

600x300x100 Tube/Fin Intercooler

ARC Air Box

3.5" Exhaust System

Fuel System

-----------

Bosch 044 Fuel Pump

700cc Injectors

Nismo Fuel Reg (Adj)

ECU

----

Apexi Power FC

Q45 Air Flow Meter

The reason i ask this question is if i can run a CR of as close to 9.0:1 as possible i hopefully can make my target power of 400kw at all four wheels with only using 16psi on pump fuel.This is going into an R32 GTR

I appreciate that this is very dependant on how good the tuner is, i will be using a very reputable tuner who has good experience with tunning GTR's

Edited November 10, 2005 by GTR_Junkie

[Abo Bob]

Sounds good to me.

I think you will have to be careful with your tune and with paying attention to your temperatures and other gauges if you are on the track but it sounds nice and responsive.

[SSS_Hoon]

my dad runs his gtr's at about 10:1 and is looking at making them even higher think he wants 11.5:1..

r32 gtr n1 spec engine and turbos it makes max power of 254kw at all 4 wheels at 5100rpm and full boost at 3700rpm of around 24-28psi.

has full motec ecu with logging race dash and according to the logging it should run mid 11's down the 1/4mile

SSS_Hoon

[GTR_Junkie]

What fuel does he run for 10.0:1?

[R31Nismoid]

mid 11's with 250awkw? and 250awkw on 24psi from N1 turbos?

good son of rajab something isnt right there... power should be over the 300 mark with N1's and that higher boost lvl

[StageZilla]

mid 11's with 250awkw?  and 250awkw on 24psi from N1 turbos?

good son of rajab something isnt right there... power should be over the 300 mark with N1's and that higher boost lvl

<{POST_SNAPBACK}>

LOL thats exactly what i thought :lol:

[SLY33]

my dad runs his gtr's at about 10:1 and is looking at making them even higher think he wants 11.5:1..

<{POST_SNAPBACK}>

over 9:1 is getting a bit high for a street car, and will be boost limited if using pump fuel IMO. The last time i heard 11.5:1 was when talking about a 350 Chev smallblock! Isnt that too high in a turbo RB application?

9:1 however should be great! You should easily meet your target, even with a lower CR. So far results from the TO4Z have been awesome (drool at R32-GTS's results). You "might" need a smidgen more boost than 16psi..

[TTT]

my dad runs his gtr's at about 10:1 and is looking at making them even higher think he wants 11.5:1..

r32 gtr n1 spec engine and turbos it makes max power of 254kw at all 4 wheels at 5100rpm and full boost at 3700rpm of around 24-28psi.

has full motec ecu with logging race dash and according to the logging it should run mid 11's down the 1/4mile

SSS_Hoon

<{POST_SNAPBACK}>

sniff sniff..

can anyone else smell that?

[blind_elk]

The Gibson Motorsport GT-Rs ran 9.2:1 @ 1.8 bar.

[Abo Bob]

Some of their engines ran 9.4 but the fact is that the higher you go the more dangerous it gets and probably wont last as long either.

[Fitzpatrick Speed Works]

Gibson also rebuilt their engines every race meeting, oh and it was a race car running race fuel, we are talking street cars here that have limited fuel choices. Anything over 9.0-9.5:1 in a turboed street car is stupid and dangerous when running upwards of 15psi!!! Its basically common physics that come into it if you look into the heating rate of compressed air, ie boosted air, then add to that compression ratios of 10+ you are running well over 180-190psi in each cylinder, and no fuels you can use legally on the road are going to burn properly at those pressures. In long 9.0:1 will be great for your application GTR Junkie, as yu will still have a nice car off boost that will be really responsive. How are you planning to run it in your GTR you should swing me a PM, as its good to start the mods at machining stage if possible!!!

[Fitzpatrick Speed Works]

Just checked something 700cc injectors are going to be stuggling at 400rwkw+, might wanna run 850's or 1000's!!

[lukits01]

What kind of piston would you have to use to get these compression ratios on a RB30?

[Cubes]

Custom pistons, obviously its all going to be measured then pistons ordered to suit what you need.

Sounds like a nice build up.

Edited November 11, 2005 by Cubes

[GTR_Junkie]

Pistons i have are CP's, my engine builder said that he will give me as close to 9.0:1 as possible he will even machine down the block to achieve this CR

Cheers,

[Fitzpatrick Speed Works]

just dont machine the block down to achieve a higher cr then sacrifice your squish you will have numerous problems then!!!

[Cubes]

How will he machine down the block if the pistons are running the 0 deck clearance as the pistons should be to achieve the correct squish.

Unless that is he decides to use RB26/rb25 pistons that have a different pin height, causing the piston to sit lower in the bore.

Then machining down the block to achieve a nice squish and resulting in a slightly higher comp ratio..

Why not simply order custom pistons to suit?

[Abo Bob]

How will machining the block sacrifice the squish?

[Fitzpatrick Speed Works]

Because if you machine te block to acieve a higher CR, most off the shelf pistons run at 0 deck height to achieve a good squish area with standard type machine work. If he machines the block lower to sit the piston higher in the bore the pistons will sit proud of the block and you will have less squish you can compensate by running thicker head gasket to get it back but then the CR falls as well and you end back to where you started!!!!

[Guilt-Toy]

We are building a 26/30 combo and need to know what pistons are needed to bring the compression ratio to 8.5:1 and 9.0:1

can someone help with this????