Steve@C56

does a 7000rpm pull show the exactly same psi when WOT in 3th gear and when a progressive rev in 1st gear (where the TB should perhaps not be full open) ?

ss4luck

huh?

So its building the same boost at 7K in 3rd that it does rolling through the RPMs in 1st?

What type of blower/engine setup/psi is it reading?

Steve@C56

lol
i dont know...
i just want to have a accurate psi reading with my news mods as soon as possible (3th wot is very hard on the street because rain period, traction and cops)
blower is overspun V3Si at 14psi
engine setup is velocitystack, handwork Z06 intake, 300cfm head, 11.1CR, large cam (638 lift), stroker, 2inch header, dual 3inch cut out, E85, 22-28 timing depending the goal (street or strip)

stevieturbo

If the throttle is closed....then you cannot expect the air to be getting into the engine to get the boost reading you want.

If 3rd gear is awkward, use 4th.

Steve@C56

thanks stevie, always here for help :-)

when i was tuning my TB, i have tune for never enter in PE mode, throttle was 35.9% open at 6krpm, so TB is not close, just 2/3 close.

as it's force induction, i was thinking the TB can only act like a restrictor (on another post, as i was looking for better MPG, everybody tell me retrictor plate will not improve MPG)

but, 34mm restrictor can get 350FWHP (rally rules)
so, with my math, 58mm can get +1000HP
and my 35.9% open TB is (because stock 78mm TB) #47mm
57mm is just 24% more than 35.9%

(shortsup) so, if i tune and drive for having a 44.5% open TB when drive slowly from idle to 7krpm (to have enough flow for hit +1000FWHP, does i can have a good psi reading ?

or is there something missing in my math ?

in fact, event if it's 90% accurency reading, it will be ok for me

i was already at 128mph at max rpm in 3th gear... dont want the cops arrest me at max rpm in 4th !!!
^^<

(hope all of this is clear.. but not sure lol)

stevieturbo

I do understand what you're saying about the size of the hole feeding the engine and largely you are correct.

Most TB's are oversized and yes at even mid throttle openings are probably more than adequate to supply full power to the engine....BUT..

If manifold pressure does still appear ok, full, whatever, but the pressure differential across the blade is quite high, this could also lead to a scenario where the BOV could be opening too, because you know manifold pressure ok...but you dont know pressure in front of the throttle. It could be a lot higher.

So when doing what you want to achieve here, ensure the throttle blade is fully open, or pretty near to it

In reality though shouldnt be a huge need to take it to 7k

Steve@C56

in fact, now, i have 1 bar MAP
i have installed 3 bar MAP and according HPT option tune, and never succeded to start (have log crap info, posted on HPT, noboby seen this before... have email HPT, never answer...)
so, i put back my stock 1 bar MAP

But i have also a mecanic gauge at the BOV, and it's the gauge i want try to read (on a video), pushing idle to 7000 slowly for different raison as i am street and i want the gauge give good information (a huge rev will probably give false value cause "needle" movement)
so... i read here pressure in front of the throttle !

(FMY : is needle is the right word ???)

In fact, i want this, with my spec : https://928motorsports.com/parts/ima...20vs%20RPM.jpg

stevieturbo

If you want to know boost pressure....which is normally intake manifold pressure, then a gauge reading before the throttle blade is not the correct way to do it.

And if the engine is not under load the gauge needle or reading will not be accurate for what you are trying to achieve.

Steve@C56

;-(

leo12

Why don't you just hook up a boost gauge, there cheap money

Steve@C56

i have already boost gauge, but difficult to stay on a public road on a 1000hp pull you know...