Hi all, a light went on in my head as I read the enlightening thread about Craig's car.

I noted with much interest the inverse relation between ambient temperature and horsepower. It's something the layperson perceives with his butt dyno, but to actually view the graph...kewl.

That said, I am running a GT700 kit, no internals, no V-Flow due to MAF issues. I'm naturally on the 91 octane setting, and have the luxury of pumping 94 octane up here as a margin of safety.

The car is a daily driver. I live in the moderate Pacific Northwest, where it seldom gets below 30F in the winter. That said, there are definitely clear, cold, dry evenings in that temperature range.

On nights like this the increase in power from the cold air is obvious but it broaches the question: is driving aggressively under such conditions a riskier proposition for your motor? As a layperson, I was always under the impression that cold air was not only enjoyable, but also desirable in terms of engine reliability.

In plain English: when I floor it in the wintertime, is that distant noise Sleigh Bells Ringing? Or detonation?

Thanks in advance for your tutelage.

VB

 

I had the same thing on my EVO 8 ... but I was at 30psi and turned out to be bad C16.... its like popping popcorn... so If thats the case call ur tuner asap... thats not right...
I had to change my head gasket the next day

What boost are u running in this cold weather? 4rth gear full throttle?

u can take out the plugs and check for detonation... that would tell u for sure.

 

That is also my concern and I have been much more careful about being too aggressive on the throttle in cold weather. What boost (sustained/peak) does your GT700 run?

This is one of the main drivers for me thinking that variable boost control is needed to adjust for these types of situations. Of course, there could also be a custom version of the program.

 

Vanboost with your 94 and "91 octane" file (the middle button heh) you're not going to be in danger. As much power as it makes it won't boost more than 1.4 etc so enjoy your bells! Because you're not "forcing" the boost level with a boost controller and GIAC leaves the knock supression and other features in tact you're not going to get knock. If it were to get into the danger zone the ECU is still able to pull timing etc... and make things safe albeit by loosing power

 

That's good to know. So do tuners besides GIAC defeat the knock supression and other safety features? From what I understand, the other tuners like UMW and Protomotive also leave those features intact. I would like to get some clarity on whether the other tuning methods are also able to pull timing, etc.

Which tuners REMOVE those safety features?

Just the facts please

 

Some do and usually when they do, the rewrite and do their own to co-incide with a MAP sensor, boost controller and external waste gates. GIAC, UMW etc... has the same sort of programing with internal waste gates etc... I believe that Protomotive has their own because they change over to a MAP sensor and use manual/electric boost controllers in the car, which would NOT work with the stock boost supression etc.. Hence they do their own.

 

Thanks Sharky!

So bottomline, at least between GIAC, UMW and Protomotive, all have the knock suppression and the ability to pull timing?

Because of the use of the external boost controller, Protomotive does not have boost suppression (since that becomes a factor that can now be manually controlled). However, Protomotive uses a MAP sensor? What are the benefits of using that sensor?

The way I understand the info (I'm new to this so pardon the ignorance), Protomotive uses a much larger table of pressure vs rpm to determine the calibration and the other approach that the other tuners use only Idle, Part-Throttle, and Full Throttle maps.

 

Thanks Alex.

So bottom line = cold air coincidentally increases power by virtue of its density; the ECU acts as chaperone for all conditions; and boost levels are somewhat static and unrelated. I'm not getting more boost in the cold, just more power.

BTW to clarify I am NOT experiencing any knock, it was hypothetical.

VB

 

Boost levels are related, depending on where the boost is set. You are correct in that cold air increases power because of higher density - which in turn uses up the 'safety margin'. The car runs leaner. If the boost pressure is set such that there is a big safety margin, it won't be a big deal. If you're already close to 'the edge' with your boost settings, this may just be what takes it over.

It's great that the ECU can play 'nanny' but I don't think we should have to rely on that for temperature differences. What kind of temperature ranges are the GIAC programs tested for?

 

Keep in mind that for a knock sensor to work to "protect" the engine there has to be knock. A safe tune is the only way to insure that the chances of knock are minimized. Its also worth pointing out that the only knock a driver will hear is of the severe type.

 

In terms of knock it's more likely to have issues under high load and very hot weather.. that's when you want to watch out. In terms of getting more boost, the colder air can allow for more boost assuming the conditions (aka gas, timing etc...) are all safe. On my car for example, in the hot summer it'll do 23psi and on a really cold winter knight that same program will do 25psi.

 

There's more than just a knock sensor when it comes to knock supression and other safety features on the bosh motronic in our cars

 

I know that GIAC and UMW's does leave those tables/code in tact yes. From what I've seen Protomotive uses external waste gates, a manual/electric boost controller and external waste gates so the "safety" is done differently than how the factory intended. It's also down to the owner of the car to be "wise/safe" and not go crazy with the boost controller because then you're at your own mercy There are nice benefits to MAP sensors for sure. Easier to tune for more HP that way as it's less sophisticated than a MAF. I would say it allows you to tun closer to the edge.

 

Before anything, thank you very much for helping clarify the situation.

A few more newbie questions:

1.) What's high load? Are we just saying hard acceleration (WOT) at the higher gears (4th gear, etc?) vs accelerating in 2nd or 3rd?

2.) how does the ecu determine what 'safe' is? Does it just allow the higher boost or more aggressive timing until it senses knock and then backs it down?

3.) 25psi is 1.7 bar right? (using 14.7 psi as atmospheric pressure). WOW!

 

Where are you located?