Does max boost vary in different gears?

[Phill The Greek]

I've had a procharger on my car for a couple thousand miles now. My post install dyno pulls made 666 whp at 10 psi. I didn't have a boost gauge on my car but installed a Lund boost box a couple weeks ago. I also just recently installed the MAK stage 2 4" inlet. I took some data logs today in third gear up to 7300 rpm and saw a tad over 7 psi.

So, my queston is, does psi vary by gear at the same rpm? I'm trying to better understand the FI world and am wondering if this to be expected or if it is possible that I have a leak from the inlet install.

Thanks.

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[dubster99]

Unless you have some sort of boost by gear controller on a turbo setup, no.

 

[Crackerjack17]

Nope. Blower puts out same cfm (cubic feet per minute) based on rpm. Doesn't care or know what gear your in. Boost is a measurement of the pressure that your motor can't use, basically. More complicated than that, but that's easy answer. Increase the efficiency of the motor/exhaust and boost will go down, but the supercharger is still flowing the same cfm. Change cam timing boost # can change along with efficiency of motor. Lots of variables. And psi will vary based on the density of air. Don't get too caught up on boost #s. Somebody correct me if I'm wrong. I am by no means an expert.

 

[ahl395]

I remember reading about the Lund boost box being inaccurate for one or two people here. May want to get a mechanical gauge and see what that says.

 

[whatsup62]

I remember reading about the Lund boost box being inaccurate for one or two people here. May want to get a mechanical gauge and see what that says.

Also outside temp makes a big difference. How much difference was there in the dyno temp vs the Boost + pull temp? I have seen mine vary from 9.8 to 11.2...no other difference than outside air temp. The denser the more boost.
What kit, head unit and pulley size are you running?

 

[MyLilPony]

I remember reading about the Lund boost box being inaccurate for one or two people here. May want to get a mechanical gauge and see what that says.

I was one of those, 2 psi off, always read high. Verified with manual gauge and my eboost

 

[Phill The Greek]

It was about 75 degrees when it dynoed at 10 psi and 100 when the boost box read just over 7 psi. I'm running the p1sc1 stage 2 with a 4.38" pulley to hit 10 psi at 5000ft elevation.

I am sure the temp had some effect on the difference, but 3 psi seems like a lot especially considering the new inlet was advertised to add about 0.7 psi (I know, I know).

If the new inlet coupler wasn't mounted flush, could that cause the difference?

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