Why no exhaust wrap

[Rob Walker]

Does anyone know why Caterham or any other manufacturer never uses exhaust wrap or insulating socks on the primaries, even when underbonnet temperatures are known to be high and that there are problems with heat soak through the peddle box and transmission tunnel panelling ????????????

[robmar]

cost, effort to do, asthetics, SVA, ability to charge for an upgrade...

 

take you pick 😬

[Rob Walker]

Rob I can except all of the above but I feel that there must be a technical reason and suspect it may have something to do with concenrating the heat on the first 12" of the primary pipe and this excessive heat damaging the stainless steel pipe.

[akakubi]

I am going to install the jackets over the primaries and attach padding to the outside of the footwels. I totally agree with you - insulation must be there. I have an oil expansion hose going right above the exhaust manifold. Now how long will that last before cracking?

 

I also have a metal cover (Ford part), but I am too lazy to remove the steering column now to ft it in. I'll see how it goes with the jackets first.

 

 

[John Howe]

ability to charge for an upgrade...

 

Catches my eye...

 

JH

Deliveries by Saffron, the yellow 230bhp Sausage delivery machine

[Claire Voyant]

Is there enough evidence to make it worthwhile?

Also, from caterham's POV it would have to be entirely manual work so unlikely to be worth doing. If you think it helps then DIY.

[7 wonders of the world]

There are arguments both ways on wrapping primaries, the NASCAR teams used to wrap but I understand they no longer do as the additional heat was destroying the primairies at a great rate of knotts!

 

That said mine are wrapped

 

Too young to be old !

[Rob Walker]

I have just asked Cheesman the manufacturer, who said it is ok to wrap their primaries as they are made from 304 stainless steel and should cope with the extra heat without a problem..

[S47zz]

Rob

I use to wrap the S/S primaries on my Dut, but within a short period the primaries had rusted through I believe the wrapping absorbs moisture when cold and on start up this gives steam which rusts the pipes at an amazing rate

I mentioned this to DJ who said he'd never had any probs?? Maybe its down to the grade of S/S used

[I.Mupferit]

It is, indeed, down to corrosion caused in mild steel pipes by moisture absorption and retention within the wrapping when the engine isn't running. It has nothing to do with the heat insulation qualities.

 

304 grade stainless is a relatively low grade of material used in general fabricating applications requiring rust resistance and will offer good resistance to corrosion.

 

Brent

(aka Arfur Nayo)

 

2.3 DURATEC SV You know when you've been AMMO'd 😬

R470.69 😬

[Doug]

I'm in a slightly similar predicament. The primary pipes on my Zetec are appx 8 inches from the rear of the alternator which, when the car is in traffic on a hot day, has a tendency to cook the regulator on the back of the alternator.

 

An engineer friend, who developed a 'factory approved' turbocharging kit for Mazda MX5s tells me that wrapping the primaries does two things: It transfers the heat further down the pipe, making the part outside a Caterham very hot indeed. Over time it also makes the primaries brittle and prone to cracking.

 

I am toying with making some sort of heat shield to protect the alternator instead since I don't fancy having to buy new primaries now or in the future!

 

'Have you any idea what it's like to have the wind rushing through your hair!' (Quote:Sq Cdr the Lord Flashheart)

[Casbar]

Loads of post before on this

 

I've had my CC 3:2:1 primaries wrapped for about 6 years now, with no adverse effects.

 

 

[7 wonders of the world]

 

I've had my CC 3:2:1 primaries wrapped for about 6 years now, with no adverse effects.

 

 

What about the other one 😬

 

Too young to be old !

[Casbar]

left the other one unwrapped so I could do a controlled experiment

[BBL]

I recall reading a theory that w/ wrapped primaries, excess heat might cause the silencer packing to deteriorate at an accelerated rate. No idea whether it is a viable theory or what, though.

 

Sean

[Colin Mill]

Hi Rob

 

I suspect part of the reason is that, as far as under-bonnet temperature is concerned it may not make that much difference. I did some sums on this thread and you see that the total heat exiting via the exhaust is only about 50% of that being dissipated via the radiator.

[CageyH]

I seem to remember it was due to the increased temperature in the exhaust, and the fact that the gas flow effectively eroded the primaries away over time.

 

I did a search on google and found an interesting, if brief article.

 

Only dead fish go with the flow....!

[AMMO]

The only reason to use header wrap is for under bonnet temperatures and for driver or passenger comfort. If there were performance gains to be had they would use it in MotoGP, WSBK and F1. They don't.

 

In the old days the only people I knew who used exhaust wrap were people whose welding resembled chicken sh1t. It was used to hide ugly exhausts headers.

 

On a Caterham if you wrap virtually all the way down to the collector, or the whole amount of the exhaust under the bonnet on an exhaust that exits the side skin expect to re-pack your silencer frequently because you will be putting a lot of heat into the front of the silencer.

 

I've never used exhaust wrap and probably never will. I don't recommend it be used with Raceco silencers but people will use it to stop their feet from roasting. Personally I don't have a problem with heat in my Duratec engined car and don't ever feel that the heat in the footwell is too much to bear. I have some asbestos cloth type material that I intended to stick to the outside of the pedal box but still haven't got around to using it.

 

I wouldn't use it or recommend it, but you guys can do what you like. Just be aware that you might have some problems if you do.

 

Just my opinion.

 

 

 

Ammo

Raceco.com

[Paul McKenzie]

Ammo,

 

Back to Basic Physics, which i can't really remember 'cos it was a long time ago ☹️, but doesn't an increase in temp increase gas velocity, ergo... wrapping exhausts should increase exhaust gas temp and speed which should increase flow through the engine, which should result in increased induction flow ...which I thought was the factor you are always trying to improve ....or am I wrong ...again

 

Paul

 

 

 

Edited by - Paul McKenzie on 8 Jun 2008 21:28:33

[Stationary M25 Traveller]

I was having a play with my new digital laser thermometer after our blat this morning ... to check the accuracy of the water temperature gauge. The gauge was spot on, when compared to the rubber heater hoses either side of the submarine rail. But - the metal rail itself - directly over the primaries (K-series) was showing as some 40C higher !! That explains why this bit is a metal tube !!

 

7 related photos

[Golf Juliet Tango]

Rob at Ratrace takes an attitude similar to Ammo's. I would not do this unless there was clear and compelling evidence of its value; which is not apparent to me at the moment.

 

Dave Pariss at Powerspeed just said something along the lines of "some people do, others don't"

 

_{Democratic dissent is not disloyalty, it is a positive civic duty.}

 

Edited by - Golf Juliet Tango on 9 Jun 2008 14:19:40

[AMMO]

Paul

 

Why not just design the exhaust to the correct shape, dimensions and length to take advantage of the head, cams, induction system etc. Then you will have good cylinder filling.

 

Good thread elsewhere about insulating footwells. This is what I would do rather than lag the headers.

 

Ammo

Raceco.com

[Casbar]

That nice chap from Emerald, wrote an article in Circuit Driver, saying exhaust wrap was a good idea. So there are experts in both camps

[Vole Sunset]

Have a look here

 

Stops sweaty feet. RIF provides a very good product. Driver side footwell got so hot one summer that the rubber bit on the clutch pedal melted off.

 

I have also covered the wiring for the alternator and the starter motor, before they get completely cooked - I'm driving in Europe this summer.

 

Not sure to what extent wrapping the exhaust will improve power output. (I reckon zilch).

[Rob Walker]

I am aware of the performance advantages etc but my worry is more about the damage that excessive heat could cause to the metal that the primaries are made. Are they likely to become brittle and crack or become anealed and prone to distortion. What is certain is that the properties of the ss tube change, it becomes black and oxidized and cannot be polished back to the same colour as the primaries that have not been wrapped.