Vacuum at highway speeds

[Neski]

Hey guys,
I seem pull very little vacuum while on the highway (-.2x100 KPA). Do RB26s create little vacuum?
When idle or taking off of the throttle it stays at a solid -.7*100 KPA

To maintain a constant speed on the highway I stay at -.2*100 KPA, but whenever I want to speed up, it needs to boost which is kind of annoying and a gas guzzler.

RB26 Engine with GT3582r turbo.
G/M 3.5 BAR MAP Sensor
Vacuum Block located with a T-off from brake booster after check valve. Block goes to MAP sensor, WG, WG Control Box, Boost Controller + gauge (last 2 are tee'd in the dash)
The nipple off the intake plenum (Front most cylinder) is routed to my BOV, and the vacuum tube at the front is routed to my FPR. The one at the rear of the vacuum tube engine is blocked off (OEM boost gauge source)
The two pipes going down off the vacuum tube go to the IACV and the other goes to a piece that I forget the name of (facepalm)
Everything else is capped off.

Is this all proper? Or could something in my tune be the culprit? Still running a very mild break in tune on 7PSI.

Thanks for any input

[Dragon Humper]

Skylines are shaped like a brick and have a crap load of drag. Drive under 100kph and the mileage will go up markedly. I barely pull any vacuum at 110kph on flat ground. Nature of the beast with that amount of drag and a motor with only 8 to 1 compression.



Once you clean up your breakin tune you can play with it to keep you nice and lean at hiway speeds to help that out....worked wonders for me. Went from 20mpg at 100kph to almost 30mpg. Once the speeds increase though, she tanks like crazy.



Jon.

[Neski]

I got the RB in a 98 Silvia. Little more aerodynamic than the skyline. I'm sure it helps a bit. I'll finish up the break in and get my tuner to clean it up. Thanks for the input.

[MikeyRHD]

Hey Dragon, what afro and timing do you run at highway cruise?

[Dragon Humper]

14 to 16-1 afr up to slightly under boost. Then it goes to 12.6ish to 2lbs then crashes to 11-1 at about 4lbs. All at 30 - 36 deg. There aren't too many areas in there where it drops below 30 deg. Thats how she gets up on the turbo so quick for a gigantic single turbo car. You want to maximize your exhaust energy as much as possible...and all this on only Cheveron 94. That caps me at only 1 bar of boost though...if I want to crank her up to 1.5 bar I have to have race fuel in it.




Jon.