Rb26/30

[chairman]

Hello

whats everyone running wit there twincam rb30 comp ratio ?

unleaded and race fuels

cheers Gerry

[luke gtr]

approx 9:1 static, using 98 octane.

[Shoota_77]

9.5:1. Will probably run predominantly E85 but it's bloody hard to get it outside of Melbourne....

[chairman]

7.8 too low ?

pretty sure rips around 7's

[Piggaz]

Why so low?

[Shoota_77]

7's would be an absolute pig (no disrespect Piggaz!!) to drive.

Fine for a drag queen auto car that you can build boost on the line but useless to drive as a street or track car.

Less comp means you can throw more boost into it but at the sacrifice of off boost driveability.

[Ben C34]

7.8 is what vl turbos were. totally crap off boost.

[luke gtr]

7's would be an absolute pig (no disrespect Piggaz!!) to drive.

Fine for a drag queen auto car that you can build boost on the line but useless to drive as a street or track car.

Less comp means you can throw more boost into it but at the sacrifice of off boost driveability.

pretty much this.

mine is pretty responsive, even off boost.

which is a good thing, because I have to wait a looooooong time for boost.

[chairman]

yes its going into a vl

just seeing what twincam run there days

for single cam 7's massive pig off boost

[luke gtr]

depending on fuel.

if using pump fuel, run 8.5 or 9:1.

its quite nice to drive as I stated.

if going ethanol, you can bump it up a little more, but careful if you want to cruise to places that dont sell it.

[Piggaz]

7's would be an absolute pig (no disrespect Piggaz!!) to drive.

Fine for a drag queen auto car that you can build boost on the line but useless to drive as a street or track car.

Less comp means you can throw more boost into it but at the sacrifice of off boost driveability.

Errr? I'm asking why so low? I wouldn't want it that low. I wanted 9.3:1 in my own engine.

Edit. Oops, read out of context. Haha!!

[Shoota_77]

Sensitive!!!

Continuing Lukes post, E85 is always going to be a challenge if it's your only fuel choice. Flex fuel is always a great option. 98 and taking it easy on cruises, E85 and cane it for track work.

[chairman]

good range would be around 8.2 to 9.5 ? depend on fuel

[StevenCJR31]

7.8 is what vl turbos were. totally crap off boost.

Yep, these were comp ratios that were from a time of (all that was available at the pump)low octane ULP and non intercooled motors :-(

[Shoota_77]

Yep, these were comp ratios that were from a time of (all that was available at the pump)low octane ULP and non intercooled motors :-(

Yeah good call and totally correct. Fuel was shite back in 1986! No premium or ultimate back then.

You need to work out what turbos you're running and what is the intended purpose of your car before you choose your comp. If you're running a massive single and focussing on drag racing or a HP dyno hero then go a bit lower comp and pump in huge boost. If you want a driveable street car or track car with good response and minimal lag out of corners then go a higher comp and smaller turbo/turbos.

Do what works for you, not what everyone else has done as we all have our own goals and uses for our cars!

[chairman]

just getting some ideas input what they run wit cars , some say low or high comp - work shop says low but I would prefer some info from owners first how it drives ect.

42r 1.01 rear 3L block full race head 260inlet/270ex 10.25 lift powerglide

[Ben C34]

Need more info man. What is the car going to be used for and what do you consider high or low comp?

Edited August 3, 2013 by superben

[luke gtr]

just getting some ideas input what they run wit cars , some say low or high comp - work shop says low but I would prefer some info from owners first how it drives ect.

42r 1.01 rear 3L block full race head 260inlet/270ex 10.25 lift powerglide

I have gt42 china, 26/30, 256 9.15 lift, 9.0:1, 4" turbo back zorst.

turbo is thrust bearing, so takes a while to kick in.

still driveable due to comp ratio.

6 speed box helps too. (manual)

but, as stated, what use?

track weapon?(guessing with glide).

[chairman]

track and more street weapon

[KiwiRS4T]

I don't think you can get pistons that will give you more compression that you can use on the RB30 so higher the better (unless you're getting custom pistons made).