[Fot] To thermostat or not to thermostat...

Tue Jun 14 09:49:15 MDT 2022

Dear Ken,

a really interesting discussion.

As far I know….F1 cars do enter air in the engine compartment and waste it through the rear diffusor together with the exhaust fumes.

But maybe I’m not up to date.

I only look at my car at speed. What is going on, which air is going where, what item needs cooling, what suffers from heat.

I would say that my car is one of the most reliable cars on the grid.

We don’t have desert races here but the temperatures can climb above 40°C in the shadow. Not often but occasionally.

I don’t look on my car stationary. Stationary cars might profit from wrapped  headers.

You’re right, Porsche did the measurements on the crossflow heads. Our heads are even more sensitive to wrapped headers because the header and intake are on the same side and close neighbors.

I gloss polished my intake header to reflect any heat radiation from the exhaust. As a result only conducted heat does heat it up.

Conduction takes place from the head side. The cooler the exhaust header and head is, the less the intake heats up, gives more power as the intake charge remains colder and more dense. 

To cool the exhaust header I need fresh air.

I don’t use an airbox as an airbox is a reflection chamber for all 4  cylinders and I don’t have the opportunity to calculate if the wavefronts of the intake process interfere in a bad manner or in a positive manner. Using no airbox is in my opinion the safe side.

I don’t rev my engine high. 5800 or maybe 6200 if needed. The overdrive is keeping the revs low.

My engine is designed to give good torque but not high power. It  produces about 170foot pound something and the curve starts from 3000 – 5800 rpm.

Cheers

Chris

Von: kknight at klaenv.com <kknight at klaenv.com> 
Gesendet: Dienstag, 14. Juni 2022 16:43
An: tr4racing at googlemail.com
Betreff: RE: [Fot] To thermostat or not to thermostat...

Chris;

All interesting points.  However, no modern race car puts any more air through the engine compartment than needed….at speed.  Notice all those F1 cars being cooled by dry ice fans at rest.  You want just enough air in to cool the radiator and this I have accomplished.  Never a cooling problem at tempartures your side of the pond will likely never see.  All the other componants have all worked well for years.  I do wrap the starter with an insulated blanket for extra protection since is sits right on top of the collector.

Several folks have done dyno runs on headers and found no HP difference coated/uncoated.  Comparing a cross flow Porsche race motor to our old lump is pretty meaningless in my opinion in this regard.  Since your carb and intake manifold is sitting right on top of the headers, certainly not the case in the Porsche, keeping them from getting cooked is the best way to  make power.   Even if there were a HP loss from coating, I would bet money on it being less than you get from heating carb/intake manifold.  There is plenty of data on coated headers being able to drop underhood tempartures by significant amounts.   Again, it works on my car as the carbs are getting the coldest air available from in front of the radiator.  The air box is insulated so that is about as good as it gets.  What remains of the air getting in under the hood is getting out.

Kas always talked about putting a floor pan on the car, he knew the benefits from when he took a TR4 to the Bonneville Salt Flats.  For what we do it is just not worth the trouble.  I run my car flat with a front dam and very low.  The cockpit is faired in and the car will pull just short of the 7,000 rpm redline with a 3.7 rear gear, which Kas figured was just about as fast as the brick can go for aero reasons.  All the rest of the setup is secret….Ha!

Anyway, great discussion and hope you have much luck racing this summer.  We are off until September and that is likely the last race for me this year.  I am retiring end of year and we have bought a 2 acre ranch property on the Central Coast of California, outside Paso Robles.  It is has shop but I will be expanding to fit the hobby.  Good news is Buttonwillow 64 miles, Willow 174 miles, Laguna Seca 107 miles and Sears Point about 200 + two Kart tracks under 60 miles (I have a TAG racing Kart).  The rest of the year is moving from Las Vegas to Paso and getting set up.  Much to do.

Cheers, Ken

From: Fot <fot-bounces at autox.team.net <mailto:fot-bounces at autox.team.net> > On Behalf Of Chris Marx via Fot
Sent: Monday, June 13, 2022 1:47 PM
To: fot at autox.team.net <mailto:fot at autox.team.net> 
Subject: Re: [Fot] To thermostat or not to thermostat...

Dear Ken,

Simple thing…..if air is entering from the front (with shroud or without shroud) the air Must go somewhere.

It can’t get in a status that the air can’t go anywhere then there would be no cooling on the radiator.

To answer, the air is going from the engine compartment under the car. And a small part along the gearbox tunnel and propshaft tunnel.

There is always air movement. Not sure about the efficiency of the side vents but they surely help and don’t hurt – if there is no connection to the wheel arches.

If the vents are open to the wheel arches they more vent the wheels and prevent car lift than engine venting.

And not to forget, you don’t get much air through these small vents, compared to the big hole under the car.

I did tafting the engine bay and videoed it to see where the air is going.

For that part I rely on having much air in the engine bay for cooling everything.

I never would coat or wrap headers…they would soak engine power of wrapped or coated.

How do I know? Porsche did many tests on this subject. The cooler the exhaust pipe is, the more power.

That’s why I leave everything open.

With regards to drag…..the floor of the TR4 is not slick, so drag is not an issue. If the drivers compartment is closed, that would rise the top speed significantly but not if the front is sealed. 

And for lift of the car……I drive in Dago Rake style…..low front , high rear. That creates a slight down force under the car from the wedge shape distance to ground under the chassis.

Cheers

Chris

Von: kknight at klaenv.com <mailto:kknight at klaenv.com>  <kknight at klaenv.com <mailto:kknight at klaenv.com> > 
Gesendet: Montag, 13. Juni 2022 16:02
An: tr4racing at googlemail.com <mailto:tr4racing at googlemail.com> ; fot at autox.team.net <mailto:fot at autox.team.net> 
Betreff: RE: [Fot] To thermostat or not to thermostat...

Chris;

If more air comes in than can go out, for instance at speed, nothing moves and there is no cooling.  There are only a few ways to get air out from under the hood on a TR, some cowl work, side vents as on factory racers and through the bottom.  With coated headers most of the heat goes down the pipe and the electrics are not that sensitive.  Only fresh ambient temp air reaches the carbs.  I have raced this setup at well over +100f/38c and all was good (water and oil temps).  Less air in means less exiting under the car with lifting and turbulence causing drag.

Hey listen, its more work and complex, likely worth only a tenth or so.  Kas liked it and it was fun to engineer.  Have a great summer racing, Ken

From: Fot <fot-bounces at autox.team.net <mailto:fot-bounces at autox.team.net> > On Behalf Of Chris Marx via Fot
Sent: Sunday, June 12, 2022 11:57 AM
To: fot at autox.team.net <mailto:fot at autox.team.net> 
Subject: Re: [Fot] To thermostat or not to thermostat...

I'm not unhappy to have some fresh air under the bonnet. 

It cooling everything,  exhaust headers, electric,  carbs, and stuff.

If all is closed only hot air comes in.

No advantage I guess. 

Cheers 

Chris 

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