Jeff Stevens' Noble M400 web site

All pictures are thumbnails.  Click on them for a larger version.

First Major Mod

As I mentioned on the insulation page, my first unpleasant Noble discovery was how much heat enters the interior through the firewall and the tunnel.  Nobles are fitted with a transverse engine with twin turbos.  The turbos are mounted on very short headers, which is good for performance, but it places the front turbo close to the firewall.  In fact, if the firewall weren't there, the driver could reach back between the seats and grab the turbo.  I figured that red hot cantaloupe being so close to the interior was a big part of my interior heat problem.

First trial fit

The solution was to replace the factory twin turbos with a larger single turbo mounted in the rear of the car.  The turbo is a Garrett GT35 twin scroll.  The exhaust is 3" with a 3" CoastFab stainless muffler that is amazingly light.  I completed installing this upgrade in my garage before my California license plates arrived!

Intercooler heat shield

Before giving up on air/air intercooling, I fabbed this heat shield to block radiant heat flow between the turbo and the intercooler.  There is a small air gap between this shield and the bottom of the intercooler box to minimize conductive and convective heat transfer.  I covered both sides with DEI aluminized fiberglass cloth.

Intercooler heat shield

Another shot on my intercooler radiant barrier, this time from below.  It was still in pretty good shape when I removed it as part of my air/water intercooler conversion.

Intercooler air box foam

I glued high "R" value rigid foam from McMaster to the underside of the intercooler air box.  This was intended to slow down heat soak.  After a couple of years of driving, the foam is slightly discolored directly above the turbo, but otherwise it still looks like this pic.

Intercooler air box air gap

This pic may not be clear, sorry!  You are looking at the air gap above the intercooler radiant heat shield and the foam I glued to the bottom of the intercooler air box.  This air gap still existed when I pulled the air/air intercooler apart for the air/water conversion.  The foam is still there and the glue held up fine (pun intended).  The air gap is intended to encourage cool (compared to a turbo) ambient air to flow between the radiant shield and the foam.

Oil pan insulation (again)

Here's another shot of the radiant heat shield I glued to the bottom of the oil pan.  It shows how close the exhaust pipe from the front header to the turbo gets to the oil pan.

Studs 'n' gaskets

I hate exhaust leaks as much as any car guy.  That's why I replaced the factory header studs with these ARP studs.  My header gaskets are by Victor Reinz and were bought from RockAuto.  I replaced the single layer stamped turbo gaskets with this Nissan 4-layer part.

A/C bracket clearancing

One minor tidbit.  It turned out that the a/c condenser mounting bracket blocks access to one of the header studs.  I used a lot of tape and a lot of newspaper to mask everything, then attacked the bracket with my die grinder.  Presto!  Instant clearance!  It also makes tightening the nut easier.

Coolant expansion tank

The single turbo 4" air inlet interfered with the (ugly!) factory coolant expansion tank.  This part is a 4' aluminum tube with end caps welded on, and internal baffle, and nipples for the rubber hoses.  Easy peasy!

Done! (temporarily)

This pic is from 2010, when I finished the single turbo conversion.  It was just the beginning of a long (maybe endless!) series of upgrades.

That inefficient intercooler has to go!

I tried hard to make this air/air intercooler work.  But my ECU logs (closing in on 1000 logs!) showed that my intake air temperature went from OK to too high on nearly every drive.  And if I parked for coffee or lunch after a spirited drive, my intake air temp would be through the roof from heat soak, and it would never come down.

cold air baffle

One of my recent upgrades to the single turbo conversion kit was this simple baffle to isolate the air filter from hot engine bay air.  A simple thing overlooked by the kit supplier.

Exhaust design flaw

There is one glaring flaw with this single turbo setup, and that is the enormous difference in exhaust path length between the front and rear cylinder banks.  Those of you with tuning experience will recognize that this large length difference turns into a large time difference in your air/fuel ratio logs.  Exhaust from the rear bank gets to the O2 sensor quickly, while front bank exhaust arrives much later.  When I log an air/fuel event (too rich or too lean), do I "back up" in time by 300 milliseconds to see what the rear bank was doing, or 1000 ms to see what the front bank was doing?  In reality, the trigger for air/fuel events is "smeared out" in time by the wildly mismatched exhaust lengths.  I will fix this!

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