Anyone care for a forum war?

Can someone clear up an argument I'm having with some idiots on PistonHeads as far as how the ECU controls boost? In short, there are a couple of guys who are saying the following:
- that on a stock engine you will see less actual boost on a cold day than on a hot day because the boost control solenoid will limit the amount of boost on a cold day to keep the engine producing stock power levels
- for the same reason, on a hot day the ECU will allow for more boost

To me, this is not correct. The ECU will not continue to pull back boost to achieve a certain hp target. Of course the solenoid will shut down the boost, and spark will be cut, if detonation occurs, but that's not what we're talking about. My understanding of the closed-loop system, is that there is room for the map values to deviate by as much as 25% which would make sense as bolt-ons clearly have a beneficial impact as far as power output even without a flash.

Using the logic of these PH guys, in the absence of new programming, if you slap on a bunch of bolt-ons and it's a very very cold day, the ECU would produce little to no boost in order to keep the power output at stock levels. This is clearly wrong, if for no other reason than the stock wastegate actuator springs can't hold boost to less than 8psi, but I'd just like to know for sure why I'm correct from an ECU perspective.

Oh yeah, they're also taking a lot of joy in slamming The6, our "drag cars" which clearly are some form of "cowboy tuning" and would never stand the rigors of a real track, as well as some of the tuners on here. Will be happy to post the thread link once we have the debate cleared up a bit.

Thanks

 

I believe my ECU and flash limit the amount of boost, either by proxy of timing control or some other factor I am not familiar with. Simply because during the hot Houston summers, I see spikes of 1.2 and sustained boost of 1.1 at times and 1.0 other times in all gears. During all other times of the year(average 60-70F), I end up with .9 in gears 1-3 and 1.0 bar all other gears. I have a UMW stock K16 flash.

I clearly don't understand the fundamentals of tuning.

 

I think that boost is made to stay consistant and not made to "limit" hp. we all know that our cars at say 1 bar boost run and have more hp on a cold day than on a hot day. due to air density etc. the controller is specifically designed to be consistant with boost not hp...
really need a Pro tuner on this board to answer your question!

PS tell them my car really does suck at the track how bout if they meet up with me and show me how to drive on a track....

 

Wow, car looks great Tom! It's been some time since I've seen pics - LOVE the rear wing!

Feel free to join in on the fun, there's all sorts of stupid comments to get fired up about...
http://pistonheads.co.uk/gassing/top...ost%20Question

 

In very very simple terms boost control works like this....

A tuner request a load (not boost). This request load is adjusted by inputs such as but not limited to IAT, knock, coolant temp, throttle position.

This corrected load is translates into a requested boost (Boost pressure set point in duremtric).

This requested boost is then archived through a PID loop (PID) that uses varying duty cylce (Boost Presure PD Factor) of the boost frequency valve to match actual boost (boost pressure at sensor) to requested boost (Boost pressure set point). There are of course factors that can intervene or disrupt this control if the ecu sees somthing it doesnt like.

This is as close to how it works I can explain it, with out write a book on it .
Now with that said, 50%+ of tunes on the market don't use the factory strategies to control boost

 

I think I see the point they are trying to argue, but it is wrong. An engine is simply a big air pump with fuel mixed into that air. There are a few factors that play into airs ability to take fuel better such as humidity, atmospheric pressure, and temperature. Dry air for example at freezing temp 0c has a density of 1.29 g/l, and with your engines intake temp the air gets heated fairly hot even on a freezing day. During days of Texas like heat the density of air at the throttle plate can drop over 30-40% no problem. Sorry for all this dry stuff but here is where it plays into your question.

It requires more air to yield the same a/f ratio and the dme see this and allows a higher pressure boost and less fuel. Closed vs open loop will yield that same result because temperature sensors will say its hot and therefore less air density, or the O2s will see it as there’s starting to be an overly rich condition. Boost pressure is allowed to fluctuate that few points because the map sensor is governing the overbosting of the car. Boost pressure cannot remain static because airs density changes. If you drive your turbo from Alaska to Mexico, you well probably see a lower bar up in the north but feel more power. When you get to the south you will see a higher bar but feel less power. Math is on your side if you need to prove to them they are wrong. Even the most advanced Bosch doesn’t have an onboard dyno to tell them the engine needs more power to meet up with what the brochure says. Hence we see 997tt’s with more then quoted power which is a good thing!

 

Tony, could you define "load"

 

I don't understand the science of engine tuning very well at all, but I do know from experience that early spring or late fall at the track, when temps are down, my car feels faster and my speedometer shows higher speeds than during the hotter months. Enough said.

 

Actual "load" is a calculation based on airflow.

Basically its a measure of the MAF reading in relationship to time(RPM).

 

thanks Jimmer and Tony thanks for taking the time to try to educate us!!