Intercooler kit for Rear Turbo GM 6.5 L Turbo Diesels

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SKU: GM 6.5L turbo diesel intercooler kit

A "Van Motor" intercooler kit !!!  What a difference it makes on hot days - and every other day too.

The price now includes a $200 deposit because you must return to us your exchange and un-modified and fully servicable  GM 10238859.  The pic above is NOT  a picture of the item - just a represenation of how it is done to attach an intercooler.

This is a listing for a FULL Intercooler kit and adapter for 1994 - 2003 + Hummer)  GM 6.5 Liter Turbo diesels van or truck engine.  The van kit comes with a special GM 10238859 - "F" or "R"  adapter and crossover for either rear or front piping 2.25" lines and intercooler, and piping.  and has five 1/8 / 27 NPT plugs for water injection nozzle mounting on each side and three in the center..  Water injection system not included.  Two 1/2 gallon per hour nozzles included for 1/4 inch (recommended aluminum)  tubing as compression fittings.  The adapter is a Genuine GM  Aluminum casting.  The side turbo mount truck version uses an elbow and rotated inlet.

Van version uses GM 10238859-F is front hook-up set up and GM 10238859-R is rear hook up (recommended - and ships by default)

Air density loss from 27° F hotter intake air equates to a 5% loss in power. For example a 235 horsepower engine would produce 223 horsepower.  The OEM plastic air box is a good insulator in keeping the air cool inside the box. The thermal conductivity of plastic is 22 times less than steel.  Aluminum is a heat sink.  The intake manifold itself with a warm engine will actually HEAT up the air with warm engine heat soak to 160 to 180 degree heat of the engine, so an Intercooler delivers even COOLER air back to the intake after compression by the Turbo.

If you think this does not mean anything - "much" - think again.  Our 6.5 L Turbo Diesel went from average IAT of 125 to 145 F to 100 to 118 F and average horsepower of 60 HP on acceleration to 100 on light acceleration.   This is unscientific - but the pressure required on the accelerator pedal is way less to move in traffic.   The Turbo previously would "surge" and would not stay in constant boost with IAT's in the 130 to 140 range, but with the Intercooler IAT's actually DROP further on acceleration from 120 to 125  to around 115.  The GM ECM de-fuels around 125 degrees and no boost much after that.  This is because more air is moving through it faster that never had a real chance to get hot - and more cooler ambient air is moving past and through fins of the Intercooler with higher speed on acceleration.  If the vehicle would be parked for a trip into a store of any kind - a return to it found the IAT at engine temperature - about 160 F, and it would not cool down much to 140 with driving.  With the Intercooler, it drops to 118 within about a block of driving - let us call it within a half of a mile.   With water injection even faster.

This is critical because if you do not know - the GM Diesel ECM has software bugs and also will "de-fuel" the Injection Pump with high IAT's, and the engine will never develop much HP in that mode and the Turbo will not kick in above 125 to 130 F.  It assumes high IAT will equate to High EGT's and thus it is programmed that way to protect the engine itself and the Turbo with pre-Trubo EGT's.    Generally this is a fair and correct assumption especially under load.    You can feel it and you can hear the noticeable absence of the Turbo whine.  With the Intercooler, not only does the Turbo stay in boost - it can be heard clearly in constant boost even when gears shift, and the vehicle runs much smoother and with better overall power.  No other changes were made, 

Unless you have an air intake temperature gauge - like an OBD-II reader-gauge like an Ultragauge - or are using a program on an Android phone across Bluetooth like "dashcommand" or using an ultragauge, you cannot see how radically the air intake temperatures swing.

Air intake cold in the morning (a southern California July morning) once started at 80 F and would go to around 116 F to 125 F and hold there as long at the vehicle is moving. Mid-day I could never get it much below 140 F. So long as it stays UNDER 125 F it would run fine - but the first long stop light will end that hope - it will get to 135 to 140 at the light.  . If you park say to go into store - the engine heat soak will cover the whole engine - when you start it back up the air intake will be the engine temperature approximately - usually 160 F. You cannot cool this back down by driving without an Intercooler.

If you push for hard acceleration - it will not cool down the intake air, and combustion temps will be too hot for good performance.  Most all research shows a diesel likes no more than 60 C or 140 F for air intake temps.  75 F is ideal. 

Over 125 F ours would run like crap and the turbo will not kick in or stay in steady . More boost is MORE heat to the intake air temperature. ULSD does not help - even though it burns cooler - it just means less power.

With the engine warm  and an Interooler - it can sit and idle until the IAT rises to 150 and then  pull off and start moving, and using an Ultragauge you can literally watch the horsepower developed go UP, with no change on the accelerator pedal - as the IAT temperature cools down    It will literally accelerate by itself.

This happens FASTER if we turn on the mist spray feature we installed in front of the Intercooler, and faster yet if we turn on the intake mist cooler inside the intake crossover corners.

A Diesel is a balancing act engine.

You can also use the twin water injection feature to cool the intake internally with straight water - or methanol injection.  You can also spray the outside of the  Intercooler with a mist as you drive for a greater temperature drop at the Intercooler as air passes through it inside.  You vary the amounts of both or either by varying the pressure to the nozzles.

We do not post a picture of the adapter - or our systems - because once we do -  once anyone does - Google picks it up and floods the web with them - and you may not post pictures of it either.   The pic shown is similar but not the same.  Pics promote unlawful installation efforts anyway.

Installation is straight forward.  You remove the existing cross-over portion and replace it with ours.  (six ten MM bolts)  You plumb the piping.  To the rear is best in a van - back towards drivers side and down past the Oil filter through the K member next to the oil pan over the tie rod and under the sway bar with a common two 90, two 45 and two U turn aluminum piping Intercooler kit.  You may need to have someone at a muffler shop etc - complete the 45 bends to 90 for you.   You will need two 2.5 to 2.25 silicone 90 degree adapter elbows, and four 90 degree  2.25 silicone elbows extra from the kit and about 16 extra radiator hose clamps,.  If you cut a 90 degree elbow from the center of the U turn pipe - that will give you two pipes with about the right angle and each side to go down the drivers side of the rear of the engine.  You can use standard turbo parts and elbows form many sources if you need more or a replacement.

2.5 inch piping with not make it through the spaces available on the GM van, and the internal diameter of the outlet of the Turbo is around 2" anyway, so you are not loosing anything really.

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  • Lower EGT: Cooler intake air is denser which allows the engine to make the same power with less fuel. Less fuel in the combustion chamber will result in lower exhaust gas temperature (EGT). An EGT reduction of 40-50°F is not uncommon.  Since cooler intake air lowers EGT, more fuel can be injected into the combustion chamber to increase power and still remain below the maximum recommended EGT.
  • Lower intake air temperature for more power: Intake air temperature an average of 7°F cooler than using the OEM snorkel alone, results  in 1.5% more power.  Cooler air intake temperature results in an increase in air density and allows your Diesel to make more power.
  • Faster engine cool down: Cooler air results in lower under-hood temperature and faster engine cool down prior to shutting down an engine.

This item is "functionally identical" to that of California Air Resources Board Execuitve Order  EO: D-140-29.   

In ordering this item you certify that your vehicle is completely "STOCK" with an OEM Trubocharger and no other modificvtions such as a non-certified aftermarket spring operated mechanical waste gate.

This kit produces a functionally identical part as identified at 13 CCR § 1900(20).  [California Code of Regulations] and is thus exempt under any California Air Resources Board (CARB) regulation or jurisdiction. 

When installed as instructed, this kit produces a "functionally identical" part to in minimum - but not limited to -  EO: D-140-29 and is thus exempt under further California Air Resources Board (CARB) regulation or jurisdiction in accord VC 27156(h) [California Vehicle Code] which reads:

""(h) This section shall not apply to an alteration, modification, or modifying device, apparatus, or mechanism found by resolution of the State Air Resources Board to do either of the following:

(1) Not to reduce the effectiveness of any required motor vehicle pollution control device.

(2) To result in emissions from any such modified or altered vehicle which are at levels which comply with existing state or federal standards for that model year of the vehicle being modified or converted.""


1.  As described above for the van only  - a special adapter and modified crossover manifold section  for front or rear piping and 27 inch by 7 inch tall intercooler as shown.

2.  Let us know in the notes which direction you want the piping to set up to pipe from.; 2 week lead time.

3.  Instructions and the item is considered - custom made - and is non-refundable.

4.  10 hours email support and a "how-to" set-up consideration for your vehicle

5.  We need the VIN of the application this is to be used on.


This is an exempted pollution control item - it is a direct purchase.

If you have a side turbo mount 6.5 L engines let us know in the note section at checkout


If you need info on how to buy with Bitcoin see => 

Price: $999.00
Weight: 30.75 lb
Dimensions: 36 in × 12 in × 12 in
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