What kind of numbers (whp & 1/4 mile) are u putting down?

 

310/310 whp on dyno dynamics. Waiting for my clutch to go in to get some times.

 

Just to add another data point, my setup holds 19-21 psi at redline (7500-8000) depending on temp. Spike will also vary with temp, but ranges from 25 psi to 28 psi. With the stock and the Forge actuator with the highest spring pressure that was available I could max out the turbo's airflow at 42-43 lbs/min across the entire RPM range of every gear. I don't see how messing around with the actuator more can improve anything, regardless of what boost is, airflow is what makes the power (or more accurately, power potential). And if the turbo is maxed out at 42-43 lbs/min, boost is an afterthought, you have no control over it. The higher your VE is, which is a good thing, the lower the boost pressure will be, but airflow will remain the same. I originally thought the internal was blowing open, like on other 16G turbos, but this simply was not the case with my 05 turbo. Other versions may be different though.

I can provide a screen capture of logged airflow on the stock turbo with the forge actuator if anyone is interested. I don't provide any boost source to the actuator at the track, so it's a good example of what the turbo and actuator themselves are doing. There is also a little more info in this thread from last year when I decided to try this actuator.

Not that any of this has much to do with efficient boost levels, but in reality with good fuel and a solid setup, efficiency doesn't mean as much as poeple think. A key point is intercooling, which is absolutely key on pump gas. To make an extreme impossible example just to illustrate the point, with 100% efficiency from the intercooler, compressor efficiency will not matter Of course this is impossible (notice I said it's impossible twice now), but it makes the point clear. Add in race gas and it's even less of an issue. I'm able to run the full 42 lbs/min on pump gas with moderate timing and 11:1 AFRs on the current setup with no appreciable knock. I wouldn't worry too much about compressor efficiency, if your setup is good.

 

Lbs-min is not an accurate measurement of airflow via a karman vortex sensor. Many factors will affect this reading. A karman vortex sensor really does not measure air at all, it measures noise. The amount of noise it measures (frequency) translates to karman vortecies and in turn given to the obdII port as lbs/min. Something as simple as a intake filter will add or detract from this figure.

 

I always thought the point of the Forge actuators was too sustain more boost near redline but it seems people w/stock and people w/Forge still are only holding 21-22 at redline... am I missing something? Or is it just that the Forge (and any other aftermarket ones) are made to hold that boost up higher LONGER then eventually taper down to what the stock can do at redline.... someone... anyone! lol

 

Good question....

 

That may be true at part throttle, but no matter what filter or intake pipe I run, or none at all, that value at WOT has never changed on any of my cars in the last 5 years. I find the Karmen meters are just as repeatable as the hotwire units I use as well. Maybe even more repeatable than hotwire MAFs in some cases (despite also relying on temp and pressure sensors), since Karmen meters are not affected by humidity. The Lbs/min values are repeatable to within a couples tenths of a lb/min. Even across dozens of cars turbos max at the same exct lb/min values on Karmen meters. Everything I refered to above in lbs/min was related to WOT. ***ume whatever you want to about me, but I don't post things because I heard them from "vendors" with fancy signatures, I post from personal experience.

I explained the reason for this in my above post. At that boost level the turbo can not flow any more air, so it can not raise the boost any higher. If the WG was blowign open, the actuator would help. But this is not the case, as I mention in the above linked to thread.

 

Ok, I checked out the other thread and I am still a lil confused.

If I set my MBC to 28-29 psi will an upgraded actuator keep my boost from tapering down to 20-22 psi? If yes, what psi would you expect? If no then what would the benifit of upgrading the acutator be?

 

You have to stop and think for a second what boost actually is. Boost is simply airflow that the turbo provides and the motor has not used. If the turbo can not flow more air, you can not raise boost. And by "you" I also mean your MBC, EBC, actuator, etc. You can set it as high as you want, but boost will still taper as the turbo's max airflow is maintained. No matter what actuator and boost controller/setting you use, you can't make the turbo flow more than the compressor wheels max airflow Well, at least not more than a pound or two, and certainly not enough to raise boost from 21 to 28 psi. At lower RPM the motor consumes less airflow, so the excess airflow and therefor boost are higher. As RPM increases, so does the motor's airflow consumption, and boost drops accordingly while the airflow is maintained in a nice flat line.

Anything that increase the amount of air the turbo moves without raising boost (cams, intake manifold, stroker, etc) will also reduce the maximum boost you hold at redline. Does this mean you make less power? Of course not Airflow (and proportionate fuel flow) is power potential, boost is heat. My point here is simply that the taper down to 21 psi is not a bad thing if it is because we are at the compressors maximum flow rate. Once you have the turbo maxed out, and enough fuel to go with it, how much of that potential power you actually make depends on the setup and the tuning. And the fuel as well, since that determines how agressive you can get with the tuning.

I'll bring the laptop in tonight so I can post some screenshots showing the airflow vs boost relationship that I'm describing here.

As far as benefits of upgrading the actuator, I really don't see any as far as performance goes. No fault to Forge or other maufactures, the factory turbo, at least on the 05s, is just really well setup from the factory. Or more specifically, the internal WG does not appear to be blowing open at high airflow levels. But, there are other benefits of the upgraded actuator that Forge outlined in that other thread. Whether or not any of those other benfits seem worthwhile, that is up to you. I personally don't like to try to run more than double the WGA spring pressure, so a 16-17 psi spring works well at the boost levels our turbo is capable of on our typical setups. As a stock to upgraded actuator comparison, at least as close as I can make it, a local NEDSM club member has the same setup as me, and even the tuning is nearly identical, but he is on the stock actuator. I'm running 12.0s with best trap in the 115s, he is running 11.7s at 118-119. His stock actuator doesn't appear to be hurting him At least not as much as my tranny's inability to shift is hurting me.

 

Here is the screen shot I mentioned earlier. Picked a random run from this year. Note the boost (blue line) starting at 25 psi and tapering to 20-21, while airflow (green line actually rises a bit, from 42 to 43 lbs/min. Airflow per revolution drops across the gear. The key take away is that airflow is maintained, since the WG is not opening (no signal provided to the actuator), at the turbos max capacity, and boost is just along for the ride.

Screen capture

 

Thanks for clearing that up man! That makes way more sense to me!