Ok so after this past weekends drag racing outting I wanted to bring the discussion from my head into evom to see what all the gear heads had to say.

This sunday's event was at bandimere speedway in Denver, CO. The altitude is roughly 5800 FT above sea level.

Here is the weather conditions for the day.
http://www.dragtimes.com/da-density-...t+Weather+Data

The event began at 9am and went until about 5pm. Most of my runs were made between 11am and 2pm.

Im running a stock 9 turbo with short ram intake, e85, street target boost of 30 psi and track target boost of 28 psi using hallman MBC.

During my first two runs boost didn't exceed 24 psi. I suspected a boost leak so went to the pit to double check and retighten all my couplers and vacuum lines. The 3rd pass I didn't get to verify boost but power was better then the 2 previous runs.

On the street the car has no problem hitting target boost but at the track is where things get hard.

So on the drive home I thought really hard about it.
I thought about the track conditions vs street conditions.
With the relation of air density to boost pressure. The lower the air density the lower the boost you can make. I was thinking that in a drag situation you wait in line to make your pass.
So you have everything getting nice a hot while sitting and then you got the track which absorbs heat making the air on the track even hotter and less denser.
Now with the short ram it picks up all the hot air inside the engine bay, and then you have the turbo that tries to compress all that hot air into boost.

Then you also have your mechanical limitations. Which are turbo efficiency, intercooler efficiency, and VE (both exhaust gas flow and intake air flow).

I was talking to some of the guys running bigger turbo's. One of them was running a PTE 6262, running 32 psi of boost. He said his boost controller was almost all the way cranked down at that boost level just to hit target.

Now while the mechanical limitations have an affect on boost compression, I think that air density is the biggest factor on boost.

One solution I thought of was using a enclosed intake box with a air ram intake coming into it from outside the car to grab the coldest and most possible air. I also figured that a few changes to the engine would assist in the turbo generating more boost such as better cams, better flowing exhaust manifold, and intake manifold.

Thats about all I have for now, i might add more or edit it later.

I want as much input as possible, but please try to keep this technical.

Thanks

 

Its always that way and has been for a long time. Mechanical Boost controllers just dont spike the same at the track as they will on the street or the dyno. On a stock turbo the spike to get 30 at the track will generally be almost 38-40 on the street. My 3586 loses about 6psi at the track with my Hallman set at 29 on the street.

 

So would ecu or electronic boost control be better?

Im surprised that I only got one comment on this so far...

 

Depends on the electronic. Some will work vs target boost (also depends on engine management) and other are little more than a glorified MBC and are targeting just a duty cycle and no tangible number.

I just always crank the Hallman a few extra turns and log to see where I end up, then turn it down the same amount it was turned up when I get back on the street.

 

Thanks for the input JB, its too bad the rest of evom has no resire to have a technical discussion.

Do you think any of the other factors affect the boost at that altitude though? Cause my MBC was almost maxed down and it was struggling to make boost.

 

There certainly are numerous external factors that you have to take into consideration when trying to make boost, and besides air temperature, ic efficiency & pressure loss, compressor efficiency, surely air density is one of them!

In the case of MBC vs EBC(ecu or separate device), the physical limitations of the EBC are mostly dictated by how well the boost solenoid works. Also, compared to mechanical control, the EBC uses the advanced algorithms of PID-control, which admittedly are more difficult to tune, but in my opinion, will always give better overall results.

What I did while I was still running stock(turbo&ecu), and what I recommend to you, is to get your hands on a Greddy boost solenoid and an upgraded wastegate actuator, and thus switch to the boost controller of your ecu. It's a relatively cheap way to go, and it will most likely improve the way your car will make boost.

 

It's also differnt when your doing 3rd gear pulls on the highway starting from a low rpm. Then banging threw your gears from a stop and keeping you rpms high..