heat affect on.........

[tanoga]

.............modified as opposed to standard stock car.
I am opening this thread from the track/meet forum.
After the rolling road day at G-Force I would be interest to know peoples opinion as to the affect of the cars performance as a result of the outside temprature being 30C.
The figures from the rolling road showed that the stock RS4's suffered no power loss whereas the tuned cars appeared to be well down. Mine was about 15% down.

[Simon]

I was speaking to Chris about this, and his thoughts were that the 'standard' cars were probably pushing out a bit more than the offical figures and then with the heat loss showing what was expected.

however because people were expecting more from the tuned cars there was more suprise when they didn't reach it.

He did also say that they can only flow enough air to simulate about 55mph so more powerful cars suffer much more in the heat. I was suprised at that considering the size of the thing and the noise it made!

Simon

[DuncS3]

interesting point about the 55 mph airflow - Interpro use two big fans and they told me they simulate 80 mph

Are N/A cars affected by the heat like the turbo cars are?

Dunc [img]images/graemlins/s3addict.gif[/img]

[JohnW]

Are N/A cars affected by the heat like the turbo cars are?

Dunc [img]images/graemlins/s3addict.gif[/img]

Nope. Well, not to the same extent.
This is due to them (N/A) not having a heat sourse in the inlet pipework (the turbo) and so not needing charge coolers.
Basically the turbo gets hot and heats the inlet air, so even though it is compressed it is not as dense as it would have been. The charge cooler attempts to act as an air to air cooler (in a similar way any radiator works) to bring the temps back down.
People have mentioned intake temps up around 60degrees, compared to free air being about 30 on Saturday.

Blowing the air at the front of the car helps in a few ways:
gets air through the charge coolers,
gets circulation around the engine bay,
produces similar intake pressure to road driving.

HTH.

Cheers,
John.

[JohnH]

Had the water spray fitted to my Impreza STi7 and presumably this helps when the air gets very hot. Anybody bothered to fit one of these to an RS4?

[sitas3]

Karl,

I posted my answer below on the other thread but it will hopefully apply here also..

My stab at this - tuned cars increase the boost/engine load significantly - therefore greatly compounding the heat problem - If you remember Mitch's data logging on Phil's car, this showed the engine load dropping off substantially whilst under max boost conditions (and about the time the intercooler temp shot up!) - therefore the ECU pulled back the engine load/power.

Whilst logging your car going down the road, your max intercooler temp rose to nearly 62C

The intercooler temp for Nick's stock RS4, stationary on the rollers, was about 40C - this rose to a max of 59C for the first run, then a max 63C for the second run at about 6600 revs, but only using about 1.1 bar of boost

[clived]

Sorry to hijack the post slightly, but a couple of points raised have given me some questions:

1) VAG-COM - what is "engine load" really a measure of?
2) Engine (coolant) temperature - does anyone else with a modded 1.8T based car suffer from coolant temps rising to approx 105C when pushing hard on hot (25C-30C) days - returning to normal when you ease off? I'm wondering if my FMIC is restricting the enginge cooling airflow...

Cheers, Clive

[Simon]

Clive,

I was 'making good time' all the way back from Aylesbury to Nottingham on saturday with the DIS showing 27 degrees outside temp and noticed no abnormal engine temps..... (A4 1.8ts)

Simon

[clived]

Simon, sorry to ask what might be a stupid question given you're on this forum, but is your car chipped? I'm pretty sure that the engine is capable of keeping itself cool in standard form, but when it's pushing out 320+ ft/lbs with a FMIC plonked in front of it, it seems to be struggling - mine is at least - or it's a faulty temp sensor, which is what my dealer said last time, but a 2nd failure after a couple of K seems odd to me... [img]images/graemlins/confused.gif[/img]

Cheers, Clive

[Nickm]

From what I understand the whole ECU runs from calculations based on engine load - even rpm is calculated from it!!!!

I was told engine load is derived from foot pedal position (because it is not mechanically linked to the engine) and volume of air going into the engine!!!!!!!!!

Regarding the poor Dyno figures for chipped cars, a standard RS4 runs a much lower boost - 0.9 to 1 Bar I believe. A chipped car has the boost at about 1.4 bar. The upshot of this increased boost is that the air becomes far hotter as it is compressed. It seems that with30 degrees ambient temprature this just tips over the limit for the temperature sensor which responds by cutting the power!!!!!

On the road it is a different story because there is loads more air around to keep the charge cooler. So the chipped cars really are much faster and more powerful - even tough it might not seem it from the dyno results!!!!!!!

I hope that this helps. I also hope it is correct!!!!!!!!

[Andiroo]

Another point to consider regarding the RR temperature effects on bhp measured, is that increased bhp on a chipped engine equates to more heat generated inside the combustion chamber, this heat then flows through the turbo cycle, added to higher air temeperature from running higher boost - sort of vicious curcle really [img]images/graemlins/frown.gif[/img]

AmD have got the Aquamist Water Injection running on my car now, pick her up Friday - let's see if there is a difference when she's logged against another modified car - hoping for an inlet temp drop of 18C on full chat [img]images/graemlins/wink.gif[/img]

Andiroo

[Riz_RS4]

Just curious, hasnt anybody converted the standard audi cooling system into the same type that evo`s and scoobies have. i.e. dump valves?

[Andiroo]

Hey Riz, dump valves maintain levels of boost between gear changes, but unfortunately dont have an effect on inlet charge temperature. Are there other dump valves I haven't come across mate?

Andiroo

[Riz_RS4]

Well im no expert on tuning etc but was just thinking.

Audi systems circulate the air flow.
i.e. ic1 - ic2 - dv - turbo - engine - ic1 - ic2 etc..... something along those lines anyway.

Jap systems just dump the air after use.
i.e. ic1 - turbo - engine - dump

Wouldnt this work on audi engines?

[JohnW]

From what I understand the whole ECU runs from calculations based on engine load - even rpm is calculated from it!!!!

Nope, rpm is calculated from the crank/cam position sensor, which is also used to ensure correct timing, and also advance/<beep> the timing based on load.

One of my mates works for a compant that produce ECU software, so I'll give him a call and see if he can give a more detailed/complete discription.

Cheers,
John.