Exhaust heat wrap (R400D)

[John Vine]

Your advice please, chaps....

I plan to wrap my R400D primaries before the summer arrives, mainly in an attempt to help keep my pixie boots from melting.

What would be a good choice of wrapping tape?  And how much would I need for the inboard pipework (between head and sideskin)?

JV

[Dr Slotter]

IMO it is better to insulate the pedal box rather than lag the primaries.

[oldbutnotslow]

IMO it is better to insulate the pedal box rather than lag the primaries.

I agree. There is an air gap aluminium heat shield on many of the 400d'd which your should have.

[John Vine]

IMO it is better to insulate the pedal box rather than lag the primaries.

 

I agree. There is an air gap aluminium heat shield on many of the 400d'd which your should have

Thanks for that. Is this what you mean?

JV

[elie boone]

A bit more expencive is to Zircotec the header to lower the under bonnet temp. and it loks neat.

[Grant_7]

L7C member Token Jock has just heat wrapped the primaries on his R500d and reports a noticeable improvement. It would be worth contacting him direct for further info.

[7 wonders of the world]

I wrapped the primaires on my Duratec - problem solved, used the 2" wrapped with 50% overlap and lockwired the wrap in place.

[John Vine]

Thanks 7wotw.  Can you recommend a particular brand?  I've seen a couple of possibles:

 

Demon Tweeks

Merlin Motorsport

 

Is that the type of stuff you used?  And should I consider the high-temperature silicone coating?

 

Browsing the archives, there seem to be pros and cons in wrapping exhaust primaries.  Some say don't do it (possibility of silencer and valve damage), while others say they've never experienced any such problems.  What's the current view?

JV

 

[ECR]

Can't remember the details but seloc Had a convincing "anti" wrap thread. It argued tha wrapping causes heat induced degradation of stainless. I had wrap but took it off when I noticed the stainless looking greyer and grainier ...

[DJ.]

I know a Seven owner who wrapped the primaries and replace it after a couple of years. The stainless was severely corroded. He had now gone for ceramic coating.

[Dr Slotter]

IMO a Duratec, either in its original installation(s) or in a Caterham, was thermally designed with uninsulated primaries. This means that with insulated primaries it is likely that the heat load that the cooling circuits needs to remove from the engine to maintain the designed temperature is greater. To what extent that is on a Duratec I don't know, and YMMV because amongst other things...

- the cooling circuits may be designed to offset that;

- there may be enough margin in the original thermal design (e.g. thermal distortion) that it doesn't matter;

- ditto the thermal requirements of the catalyst (if you have one) and subsequent emmission performance;

- ditto the efficiency of the engine's thermodynamic cycle and subsequent output/economy/emissions performance;

- the damage an engine running slightly hot would occur might never be the primary reason of a failure;

As an example of how it can go wrong without changing very much, when I was with Ford I did some work on a V8 engine that had an order of magnitude worse exhaust valve wear on a corner cylinder for apparently no reason. It turned out that there had been an in-production change to the cylinder head casting which had moved a cooling channel a few mm which raised the local temperature in that area. This meant that the cylinder head was in turn locally distorting which dramatically increased the valve wear.

Edit to add - obviously lagging and other thermal treatments such as Zircotec, which I have experience with, are great in their place. They just to be part of the thermal design of the installation.

[7 wonders of the world]

Some interesting points,

I would however consider that in like for like power comparisons the 7 would probably run a cooler exhaust as the FWD install in a Mondeo / Fiesta has the manifold tucked down the back allied with this they both tun a cat directly under the manifold so this will increase local temperatures.

so even wrapped primaries are likely to be lower than this.

Cooling system wise I take my steer from Cosworth who apart from using an 82 degree stat, still in the OE location make no other changes to the cooling system, yes they use different outlet elbows purely for differing install but most still even use the OE modene cooler.

The increase in primary temperature with also offer a useful increase in gas speed too.

If your running full beans then you may suffer some degradation on the primaires, however most are wrapping primiaries in order to prevent their toes resembling a chocolate bar in a kids pocket, allied with the low usage of most 7's it highly unlikely that this will be an issue.

[John Vine]

Thanks for your comments, chaps.  I've decided to proceed with the wrap, so I'll let you know how I (and particularly my feet) get on.

JV

 

[metal mickey]

You will likely see accelerated degradation of whatever exhaust packing material you use if running at sustained high revs. 

[John Vine]

Thanks for the warning, m-m.  My car has the standard CC non-repackable silencer.  Is that likely to be less vulnerable, or more?

JV

[metal mickey]

No experience of the std non repack able one from CC. I have tried wrapped primaries as a direct comparison to unwrapped and the packing material in a repackable silencer suffers higher degradation. In my experience with Raceco silencers the packing burns away from the front, obviously where the hottest gases first reach the silencer.  Wrapping the primaries does what it says on the tin and retains the heat within the pipe with the result being hotter exhaust gas reaching the silencer thereby producing the higher degradation rate of the packing material I experienced. Personally I would look to insulate the pedal box and any other items close or susceptible to heat on an individual basis. 

[7 wonders of the world]

The other benefit of wrapping is that it helps reduce underbonnet temperatures, especially for those applications which have an internal air intake possible from an noise reduction aspect.

 

[7gineer]

Hi all. No results as yet but the insulation to my starter solenoid cables started to melt so I have wrapped primaries using grey bandage from Demon Tweaks - needed most of 2 rolls of 50mm, and damping it with a small spray water bottle made it much more flexible around the bends!

I also used insulated reflective sleeving for cables, and routed them under the solenoid initiallyas far from primaries as poss.

 Tip given to me was to leave a gap of about 25mm between the top manifold flanges and the start of the tape.

I intended to try to wrap them in situ (silly idea in retrospect) but ended up taking primaries out to replace starter motor. Apart from having to use a variety of sockets and spanners and extensions etc., to get at nuts (and one stud came out as well) much easier to wrap individually. Found it easier to temporarily  tie start with a cable tie at bottom end then replace with a metal strap band. Finish at manifold end.

Initial start up was veeeeeeerrrrrrryyyyyy   smoky - so outside recommended!!!!!!!!!!!

Agree that gases will reach silencer hotter, but will have to wait for longer term results.

 

 

[John Vine]

Thanks for all the feedback, chaps.  I've now completed the wrap and this is how it turned out:

 

 

I've done about 80-odd miles so far (loads of smoke when I first fired her up!) and the cockpit is definitely cooler.

For those tempted to do something similar, this is the stuff I used:

Wrap (2x 15-ft rolls of 2" natural -- just about enough)

Silicone coating (in black)

Plus lockwire to hold the ends of the wrap in place.

It was certainly much easier with the primaries removed and clamped in a vice.  I used a Jubilee clip to hold the first loop of tape -- that way, I could get the wrap really tight.

JV

[LouisFeakes]

Anything to report on the wrapping John?

Pros/Cons - am thinking of doing the same so interested how the past 6 weeks have been.

Louis

[John Vine]

Thanks for the timely prompt, Louis.  After about 800 miles, including a trip down France, I can report a big improvement. The tunnel sides are much cooler (or, at least, less hot) and I can touch them without burning my fingers. The cockpit is now a much more pleasant place to be and my feet are much happier little bunnies.

JV