This is the make or break issue for me with adding forced induction to my car:

Can you still track it, reliably, w/o excessive heat soak, on a hot track?

My pit mate in my last DE was running a Saleen Mustang (roots-type blower). It was over 100 degrees on the track (texas world speedway). He suffered from heat-soak that was so bad, that he decided that he's no longer fussing with the car and gonna dump it. For you TWS guys, he went from a top speed of about 130 on the front straight to barely managing 95 (from over 350 hp to under 200 hp).

All that, and he was running an water-air intercooler!

Now, I'm not saying that forced induction is bad, as there were some factory turbo'd cars there running fine (twin turbo porsche, audi TT), but I'm hesitant about exposing a car with non-factory induction to the extremes of a DE, where you run flat out during multiple 20-30 minute runs in a day. Quite a different environment than even the most spirited street driving.

What do you FI guys think?

(woops, should have been capability in subject heading)

 

any supercharger guys out there been to the track? anyone?

 

[QUOTE]Originally posted by frayed
[B]any supercharger guys out there been to the track?

 

My last track day was a two day event here in Phoenix at or above 100 degrees. At the end of the second day I was still out running C-5 Corvettes at the end of the main straight. Ok, it was just one C 5 corvette.

No significant drop in performance and I was carrying a passenger most of the time.

 

Frayed,

I do not own and have not raced a SC'd S2K on track. However, let me say this.

Any time you make substantial power modifications to a car, you have to consider upgrading other support systems to cope.

When you add a forced induction component to a previously normally aspirated car, many things have to be considered.

First of all, more hp means more heat dissipation required. This component is pretty much linear. If you increase hp by 40%, then you will increase the heat you need to dissipate by at least 40% as well. Modern cars are usually designed with some overcapacity in this area to compensate for particularly hot climates, high altitude, traffic, etc. Whether or not the S2K has enough excess capacity to handle 40% more hp is an unknown. On an open, fast racetrack without traffic in front of you, things may be o.k. What you have to watch out for on track is following too close behind another car for too long (not enough airflow), or getting back on track with a heat soaked engine after letting it sit in the pits for a while. Slower racetracks with high loadings but low absolute speeds can be problematic as well - the Streets of Willow course is one of the best tests of a cooling system I've seen. At 2000 ft of altitude cooling efficiency is reduced. Furthermore temps in the summer regularly exceed 100 F. Finally, the track is full of lots of 2nd and 3rd gear corners, but speeds rarely exceed 70-75 mph for street cars.

The second thing to consider is that even intercooled FI systems will create additional heat beyond the simple more power = more heat factor. This is because they heat charge air to some level above ambient. For something like the Comptech system, its probably on the order of 40-50F. But that means your cooling system takes on more heat, your exhaust temps are higher, etc.

The third thing to consider are abnormalities or tuning mismatches in the car. These usually result from running a subpar engine management scheme (stock ECU for example on a NA to FI conversion) or from improper tuning even with a good management system. On the S2K, we are fortunate enough to have a pretty good knock sensor and what appears to be an aggressive ECU when it comes to temperature sensitive changes. This may make the stock F20C more tolerant to modest FI. In the case of your friend's mustang, I'm wondering if he didn't have to retard his ignition timing quite a bit to make the car run properly. Retarded ignition timing prevents detonation, but it also increases engine temperatures. And I'll bet he didn't have a knock sensor either. Oh, and BTW, magazines running lapping tests of the Audi TT (225) have noted that it seems to pull back power after a few laps as temperatures build.

In the grand scheme of things, I'd say that if you plan to regularly track a SC'd S2K, and are an aggressive driver, you should plan to upgrade the cooling system. At a minimum I'd want a bigger radiator, an oil cooler, high pressure cap and maybe a cooler thermostat/fan switch. But the primary cooling items are radiator and oil cooler. They're what really matter in thermal capacity.

UL

 

UL, solid input, as always.

What's interesting, and something that I did not realize, is the relationship b/t generation of heat and generation of power (directly proportional). I had always thought that the heat generation issue was due solely to the added heat to the intake charge caused by (i) compression of the intake charge, following the ideal gas law PV=nRT, and (ii) the intrinsic thermal ineffeciency of the FI compressor.

Thanks.

 

TWS even is this month, I'm going. I will be able to monitor exhaust temp to see if it gets high throughout the day, but that's about all I have to monitor temps.

What exactly is "heat soak", and what are the symptoms?

Wesmaster

 

Perhaps one of our resident thermal guys can explain the term more precisely, but...

As I use the term with cars, heat soak is the process by which an engine, usually sitting in the pits turned off, actually reaches higher temperatures than when it is out running. This is due to residual heat from operation and no effective cooling. On my CRX this is particularly problematic with the oil temps which can soar to over 300 F. In some cases, this heat can be difficult to remove even if you get moving again (there are minimal provisions for oil cooling on a factory CRX engine for example).

In more general terms, heat soak is just that. A component is getting "soaked" by heat. Hopefully someone who is more knowledgeable than I will provide us with some more insight.

UL

 

Are you referring to God?

As always a good reply full of knowledge, thanks Lurk.

So, as long as I let the car run and cool down, I should be ok - at least that's what I'm hearing.

Wesmaster

 

I'm certainly no expert, but given the relative conditions, wouldn't all cars suffer the same basic effects, thus, still being "equal"??
Dunno,
Aaron
p.s. Having forced induction has to be more HP than having none... or so I would think.