Acceleration/Boost Question (WOT)

**event** · 10-07-2010 10:59 AM

Ok so this has been bothering me for a while since I got my boost gauge. When I push the gas pedal to that point where it settles just before you go WOT (I believe) I peak at 19ish PSI and hold at 15ish. Now if I slam the pedal and go WOT I peak at something like 15 and hold at below that.

What's going on here, is this normal? I've never had a boost gauge so this is the first I'm seeing my boost levels in plain sight.

**jimrobbington** · 10-07-2010 11:16 AM

That seems exactly like what mine does. As far as I have been able to find out, it is completely normal. I noticed my boost was peaking at about 13 psi the other day, and found out all my REVO settings had been set to 0 when I installed my stereo. It feels fast as shit again after getting used to it "slow" But, seems normal.

**deeznuts** · 10-07-2010 01:12 PM

event what mods do you have? the reason i ask is because i have the same thing with my car, except i spike 21-22 and hold at 19...and other times when im in a low gear WOT on the highway, ill get 15-16 and the descend down to 12-13 lbs...im at stage 2 all bolt ons with forge blowoff....i ordered stiffer springs for my blowoff valve, so i can see if that helps hold the boost a little more, and if that doesnt work i also have a boost controller laying around that im gonna install to bypass the n75 to see if that helps.....i dont like seeing 15 pounds when im on the highway haha, its a lot better when i see that 19-22 pounds

**jimrobbington** · 10-07-2010 01:19 PM

A lot of things will change these numbers. I have always been about 2-3 PSI under what a lot of people on here claim, and I believe that has to do with elevation. I am around 6k elevation, and everyone where I live has similar numbers. When I had Carbonio installed, I would peak 19psi. Stock intake I will peak around 17-18psi but hold 15.

**event** · 10-07-2010 01:32 PM

Originally Posted by deeznuts

event what mods do you have?

Performance wise (hp/tq) I have APR flash, 034 HFC and AWE FMIC. I think I might be leaking some boost after the IC install though, cause I didn't get a bump in PSI at all from it. I have a Stewart Warner gauge in my Podi, so maybe if I got something electrical I would get better readings, idk... the Warner buzzes like a mother****** too, even after the anti buzz adapter.

**Insane_Audi** · 10-07-2010 01:38 PM

Originally Posted by jimrobbington

A lot of things will change these numbers. I have always been about 2-3 PSI under what a lot of people on here claim, and I believe that has to do with elevation. I am around 6k elevation, and everyone where I live has similar numbers. When I had Carbonio installed, I would peak 19psi. Stock intake I will peak around 17-18psi but hold 15.

elevation does not affect boosted cars, only NA

**bskis1080** · 10-07-2010 02:57 PM

event, my stewart warner buzzes a ton as well. I dont know about the elevation where you drive and whatnot but I have APR 93 (assuming you have 91) and the same gauge in my car peaks around 18 and holds just below that like 16. Im installing my 034 HFC on saturday and I'm assuming I'll peak around 20 then. I can get back to you because at that point we'll have very similar mods other than the AWE, which is what you think youre having trouble with anyway. Plus monday Im moving west so I'll be on my 91 program for the rest of the winter and then it will be even more telling of whether you have a leak or not.

btw I have two anti-buzz restrictors, one at the tap in point and another ~14" from the gauge. I'm thinking of popping another in there closer to the gauge since I was mailed like 5 extras. Any thoughts on whether this will do anything at all?

**jimrobbington** · 10-07-2010 03:07 PM

Originally Posted by Insane_Audi

elevation does not affect boosted cars, only NA

Not true. The air is much thinner at elevation, causing the turbo to have to spin much faster to try to acheive requested boost, causing the air to get hotter than it should resulting in slightly less boost pressure. Other than that, yes, elevation has no effect on turbo cars like it does on NA and supercharged cars.

**event** · 10-07-2010 04:59 PM

Originally Posted by bskis1080

btw I have two anti-buzz restrictors, one at the tap in point and another ~14" from the gauge. I'm thinking of popping another in there closer to the gauge since I was mailed like 5 extras. Any thoughts on whether this will do anything at all?

I hope so, it's damn annoying, now I have two buzzing/vibrating effects at certain RPMs, one from the gauge and what was originally just my shifter area.

Elevation shouldn't be an issue with me, mine is only a few hundred feet.

**Alkemix** · 10-07-2010 10:12 PM

Originally Posted by Insane_Audi

elevation does not affect boosted cars, only NA

I know RimJobbington has already answered this, but elevation affects anything that requires oxygen. It only affects our cars a little less, since the job of forced induction is to make the air denser and compress more oxygen molecules together. Superchargers should also be doing the same thing, so supercharged cars should also fare better than N/A in higher elevation, but maybe not as well as turbos that hit higher PSI levels.

**jimrobbington** · 10-08-2010 05:56 AM

Originally Posted by Alkemix

I know RimJobbington has already answered this, but elevation affects anything that requires oxygen. It only affects our cars a little less, since the job of forced induction is to make the air denser and compress more oxygen molecules together. Superchargers should also be doing the same thing, so supercharged cars should also fare better than N/A in higher elevation, but maybe not as well as turbos that hit higher PSI levels.

I was reading an article, I'll see if I can find it again that was explaining how it all works. Superchargers apparently, have no way of "correcting" for elevation, meaning they acheive less and less power at higher elevations, whereas a turbo always tries harder to a point.

Ah, here it is. It's kinda long, so I'll link it, and not paste it.

**event** · 10-08-2010 06:26 AM

Originally Posted by jimrobbington

I was reading an article, I'll see if I can find it again that was explaining how it all works. Superchargers apparently, have no way of "correcting" for elevation, meaning they acheive less and less power at higher elevations, whereas a turbo always tries harder to a point.

Ah, here it is. It's kinda long, so I'll link it, and not paste it.

I'm pretty sure I seen a automotive site that had an RS4 in high elevation that lost something like 20+% of it's power and after slapping a supercharger in it, it was doing great.

**jimrobbington** · 10-08-2010 07:29 AM

Originally Posted by event

I'm pretty sure I seen a automotive site that had an RS4 in high elevation that lost something like 20+% of it's power and after slapping a supercharger in it, it was doing great.

My shop here in denver did a PES supercharger on am RS4, and did before and after dynos. It was not too impressive. Stock it only made about 280 whp, and gained about 100 hp to the wheels after. I'll try to dig that article up. I just felt very unimpressed that our car can be built to have more power.

**jimrobbington** · 10-08-2010 08:09 AM

ok, so Audi claims on the RS4 to have stock performance of 420hp and 317tq at the crank. Keep in mind, this car already has full exhaust and REVO tuning. They dynoed the "stock" RS4 at 281 whp and 256 wtq. That's less wtq than I have on my stage 2 A4! I cannot however find the link to the post-supercharger dyno.