Stock '96 R/T TT boost curve - Is this normal?

Thanks for the replies although I'm still hoping someone with a stock car can look at their boost curve during a 2nd or 3rd gear pull from 1500. But then again, how many 100% stock cars are running around with a boost gage? To make these curves, I temporarily mounted the boost gage near the tach and video taped the runs with a high shudder speed. Then watched the footage in slow motion and jotted down the boost points vs engine speed at 500 rpm increments.

John M - I too thought there may have been a possibility I was boosting high and that's why I ran the test. Funny thing is that during my simulated 1/4 mile runs (if I ignore the low rpm first gear roll) I spent very little time above 10 psi. On both the 1-2 and 2-3 shift I spend just a brief moment at ~12psi and then it quickly drops to ~7.5 psi. With an agressive launch I don't believe I would have seen 14 psi in first either since I'm above 5,000 rpm the entire time. So I'm pretty sure I never see above 12psi on a typical quarter mile pass unless I bog out of the hole. I'm also not convinced that the 14 psi spike is abnormal and hope that someone else can verify or contradict this on their stock 2nd gen.

I will try to post some videos of my simulated runs as well as the 3rd gear pulls. I don't want to put any mods on my '96 but it's hard since I know nothing more than a boost controller will allow 12s! (in our cool ideal conditions). I'd like to hold more boost just after the 14psi spike until the turbos can no longer support it. This would make the car much stronger at the high rpm region especially just after shifts when the rpms drop.

shovel & others - ET & trap would be optimized if the car was run in such a manner that the maximum torque reached the drive wheels at all times. This doesn't mean drive the car at maximum engine torque however since the gear ratio you're in acts as a torque multiplier. Instead (neglecting higher driveline losses at higher shaft speeds) driving at peak power will give you the best times/speeds. If you had a CVT that allowed you to pick an rpm at which to run at, you'd want to run at peak power (again negelecting driveline losses due to higher shaft speeds). It is at peak power that you maximize the torque to the wheels. In my example in the original post, I indicate shifting at 5,800 rpm may be better. This may have been shifting too soon, but because of how much the boost fell off and the fact that I know the volumetric efficiency on a stock car sucks at high engine speeds, I may be better in the next gear (high torque with a lower torque mulitiplier) than spend time in the lower gear (low torque with the higher torque multiplier). This conversation would make much more sense to anyone reading it if you work through some examples on paper looking at an actual engine torque curve. Once you throw in increased driveline losses due to shaft speeds, you'll find that most torque is sent to the wheels somewhere between peak engine torque and power (likely closer to peak power).

In short, the optimum shift points for each gear can make definite improvements in both ET and trap speeds. I believe I was short of optimum (shifting just above 6,500 in each gear), so I should be able to improve my times.

Joe,
My '95 with no boost control peaked at 9 lbs in first
from a launch. 10 lbs in 2nd. 10.5 lbs in 3rd gear. In
all three it would drop back to 7-8 lbs very quickly. The
only exception was when I hit 4th. It peaked almost 11.5
lbs and held almost 10 lbs until I let off. I think this is the
reason we seem to gain more than the "10 hp/lb" of added
boost rule of thumb. We are really getting about 5 extra
lbs of boost over stock in most of the rpm range. And also
why we seem to gain comparatively more power in the first
3 gears with basic mods.
BTW,some fine driving regardless of boost.
Congrats!
Wayne

So we have some saying this is normal and others leaning towards a possible vacuum leak to the wastegates. I will check for the boost leak (easy enough with my vacuum pump) but I highly doubt it since I'm the only guy to actually turn a bolt underhood and everything is pristine.

I've got an offer for anyone in the area or willing to come near me (Westland, MI) with a stock car. I'll temporarily install a boost gauge and record a third gear pull at high shudder speed and map your boost vs engine speed like I've done on my car. A 2nd gen is preferred but I'll do any stock twin turbo. I have a feeling that our cold ambients favor a quick spool up (lots of exhaust energy to power the turbine) and as a result the wastegates allow a little too much boost initially. I want to either prove that my car is running like it did as it left Japan or make it as such.

If Alan Sheffield is willing to host a video for me (hopefully later tonight) I will post a link to my runs showing that I was only boosting 7.5psi for a majority of my 1/4 mile run with some quick spikes to ~12psi during the 1-2 & 2-3 shifts. I believe this would be normal boost for a 2nd gen car.