Ecotec Powered Triumph TR4

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This is my cousin Jim’s Ecotec Powered Triumph TR4.  Currently for sale on Bring a Trailer – CLICK HERE.

Jim passed away about a year ago.  He was a machinist and built many cars in his shop in Greenville, SC. This was his personal car, having built it about 14 years ago. The car weights 2100 pounds – read more HERE. The odometer in the speedo states 21,784 miles. The speedo was brand new when installed at the time the car was restored (zero miles). The paint scheme was inspired by the 1959 ex-works Sebring Sprite – Jim owned a Bugeye Sprite back in the day, and he used to talk about it a lot!

The body shell was locally sourced in Greenville SC and was for the most part rust-free. The body was stripped, primed and painted in Jim’s shop. Bad spots were fabricated and repaired then welded where needed. The hood and the trunk lid are all aluminum, formed with an English wheel in his shop. The hood and trunk lids both have custom fabricated stays. Finally, a custom hardtop was also made from aluminum. The car does not have the convertible soft top frame nor soft top.

Inside, the car has a roll bar mounted to the frame. In addition to the hard top, the car comes with an “Alumakini” that can be used instead of the hard top (read more HERE and HERE). In the nose of the car is a custom aluminum air dam, stainless mesh, and aluminum front grill. At the rear, the bumper is custom made from aluminum, as well as the tail light bezels. All body panel fit is consistent and there are no big gaps between body panels.

The car rides on a set of 185/55R16 Firestone FR740 tires mounted on Panasport 16″ wheels – read more HERE.. Wheels are free of scars or curb rash. The tires have code “V698 ADR 2820″”; no cracks on the walls; no cracks on the tread. The 2820 date code indicates these tires were manufactured in the 28th week of 2020.

Jim made a new frame from square steel tubing to match the dimensions of the original frame. The frame was designed to hold Triumph TR6 IRS front suspension components, TR6 steering rack, Aldan coil overs (front and back) and a modified rear axle. The rear axle housing is a narrowed 8” Ford with Motive posi-traction and a 3.80 to 1 ratio. Axles are special order Moser. The rear end is held in place by a 4-link design. Once all was fitted, it was taken apart and painted black and re-assembled.

The frame was also designed to hold an LE5 2.4 GM Ecotec 4-cylinder motor. The motor and transmission came from a 2006 Pontiac Solstice. The engine/gearbox was purchased from a lot of engines/gearboxes sold by Mallet Cars. Mallet at the time was doing LSx conversions on Solstice/Sky cars, and we bought 3 “take out” motors with almost zero mileage. The engine and transmission in Jim’s car originally had less than 20 miles on it. The engines came with the Solstice harness, and that was later modified at Jim’s shop to fit the engine compartment of the TR4. The gearbox is an AISIN 5-speed, as fitted to the Solstice/Sky. The engine did not come with an ECM, so an ECM from a 2.4 Cobalt SS was used instead. Using HPTuners, the base Solstice 2.4 tune was downloaded to the ECM as a base and then, further tuning was performed. The E67 ECM fits inside a custom aluminum box in the engine compartment. Various relays, circuits and main fuse panel can be found there. The Ecotec has variable-valve timing (VVT) and it is noticeable when accelerating.

The engine is for the most part stock. However, the Solstice intake is too big so a custom aluminum intake was fabricated by Jim. The new intake was mated to a GM sourced flange that matches the intake ports. Four aluminum runners were welded and the new intake made to match. The original fly-by-wire electronic throttle was adapted to the new intake. Due to space restrictions, the headers were fabricated from stainless steel and welded to a GM sourced exhaust flange, including provision for an O2 sensor. This was welded to a low restriction muffler and a single stainless pipe exiting at the rear of the car. Just because we wanted to be different, the end holds two Supertrapp diffusers with removable rings. All this gives the TR4 a very distinctive exhaust note. The driveshaft is custom-made by a local manufacturer and adapted to fit the AISIN 5 speed gearbox and narrowed Ford 8″ rear axle.

The E67 ECM has been set up by a local LSx tuner. He set the mapping based on several hours of real-time driving; the TR4 was never put on a dyno. We used HPTuners to remove VATS and also to set the engine mapping. The Solstice was originally rated at 177 HP and with the new intake, exhaust and tune, the tuner estimated it would be good for 200 HP. Perhaps this can be improved with more tuning/dyno time.

Engine cooling is handled by a Griffin Thermal Products aluminum radiator. It has a custom-made shroud holding a SPAL curved blade high-efficiency puller electric fan. The fan is controlled by a temp sensor that has a potentiometer that can be dialed in for whatever temp you want to set – this is inside the aluminum box housing the E67 ECM. At the time we put the car together we did not have the fan figured out to run with the ECM. However, with a little work, this can be achieved.

Due to the fuel requirements of the Ecotec, Jim made a new aluminum fuel tank for the TR4. This tank is fitted in the trunk and holds a modified GM LSx electric fuel pump. There is also a fuel regulator mounted in the trunk for dialing in the correct fuel pressure. If you look at the frame pictures, you can see all the stainless tubing for fuel lines and brake lines held in place with special brackets. The tank holds approximately 15 gallons.

As stated previously, the Solstice engine harness was modified to fit. The rest of the car’s wiring was made at Jim’s shop. All wires, relays, switches and breakers were sourced from Waytek. All joints and connectors were soldered and shrink wrapped. Gauges are all VDO and are fully functional. Lights all work, turn signals work and brake lights work (see video). The instruments are mounted on an engine-turned plate on the wood dash. The VDO speedo has a problem with the LCD for the odometer in that it goes blank from time to time, although to the best of my knowledge the counter continues to work.  This seems to be a known issue with VDO speedos and there is a fix available on youTube – CLICK HERE for the video.  I have contacted AK Speedo and they have told me their repair kit will work with the VDO speedo.

There is a fuse box mounted in the passenger’s side dash area. The master switch is on the wood dash, with a key. There is a momentary on/off toggle switch next to it, and that starts the car. There is also a switch mounted on the dash for the turn signals. Mounted underneath the edge of the dash (out of sight) is a horn push button, light switch, windshield wiper switch (with low, fast and intermittent settings), heater switch and fuel pump switch that acts like an extra security because the engine won’t run without the pump running. To turn the car off, just turn the key back to the “off” position. I provided a video that explains all this too.

There is an adjustable steering column! This is controlled by a small lever that unlocks the mounts and allows free travel up and down. The four spoke steering wheel is custom made and hand stitched. The shift knob came from brass stock, and was turned by Jim on his lathe. This compliments the very short-throw shifts by adding a little more mass to the shifter. Installed is an aftermarket street rod heater. Jim made several trap doors that are manually operated to help distribute warm air to either passenger side or driver side or defrost to the dash. The headlight high/low beam is controlled by an old-school foot switch, mounted vertically on the side because there is no room on the floor. You can press it with you left knee. There is also a lever near the heater that opens/closes the air scoop on the dash. There are factory openings behind the dash that allow air to come in.

Brake calipers are Wilwood Dynalites in the front and Nissan in the rear. The rotors are TR6 in the front and matching Nissan on the rear and they are not vented. The hand brake mechanism was fabricated and it engages he rear brake pads – however this might need to be adjusted. The brake master cylinders are Wilwood with two reservoirs and a balance bar on the pedal, so this allows bias adjustment. The clutch master cylinder is also Wilwood. Also to note, there is no power booster and as such, requires a bit of pedal pressure to stop the car. The pedal box is also Wilwood. There are pressure residual valves on both front and back brake lines. This provides a constant minute pressure reducing the amount of pedal travel. A keen eye will notice the VIN plate is not where it is supposed to be: in the area where the Wilwood pedal box is currently installed. The VIN plate has been relocated to the driver’s side door sill.

The bodywork was all done at Jim’s shop. The body was primed, sealed and painted with single-stage automotive paint in Gulf sky blue. The aluminum top is painted in gray, and has a small crack on the passenger’s side. Overall, the paint is not show quality. It has aged, shows some orange peel (mainly on the top) and has a faded patina. Perhaps in the hands of a professional, the look could be improved. There are several small cracks in the paint and there is a damaged spot on the passenger’s side door. There is a small ding on the hard top, but since it is aluminum that can be repaired with a hammer and dolly.

The aluminum top was shaped to resemble the hardtop on a TR6. The side windows do open and have a fabricated latch that allows the window to swing and lock in the closed position. The side and rear window are all acrylic, and while the side windows are still clear, the rear window is very foggy. The rear window can be replaced by removing screws holding it in place.

Jim fabricated the aluminum bomber seats. The bottoms have a rubber insert with springs around it, reminiscent of old Jaguar seats. The back-rests are held by screws. All the upholstery was made by a local automotive upholstery shop. The seats currently in the car are “version 2”: they have a longer seat cushion and are very comfortable. Included with the car will be the “version 1” seats; they have a shorter bottom cushion and different backrest design. Lap seat belts are provided and are bolted to a post extending from the frame. This is the same post that the roll bar is bolted to. There is a small box in the back deck between the roll bar posts for holding registration papers, etc. This small box is made of aluminum and has a lock, however I don’t have the key for that lock. The carpet throughout the car was sourced from a local upholstery supplier and was cut and shaped to fit.

The fuel tank is made of aluminum with an in-tank fuel pump accessible through a bolted cover. The tank holds approximately 15 gallons. The tank sits in a recess in the trunk so the bottom of the tank is not exposed. In the trunk area is a separate small fuse box that controls the rear lights as well as the fuel pump. Inside a fabricated enclosure sits a red-top Optima battery. The fuel tank has a spout with a custom turned aluminum knurled top that screws on. The trunk lid does not have a key, instead there is a small cable that extends underneath the back bumper, that when pulled, opens the latch. Closing the lid requires very little effort.

In summary, this car is a blast to drive! As shown in the photos, the car has room for improvement aesthetically. There is a lot of TLC but the mechanical systems and quality is absolutely first rate. The car has not been driven much over the past few years, and the underside could benefit from cleanup and paint to get rid of the surface rust. I have several ignition keys. The car has a clean South Carolina title and is in my name.

Finally: There is more info in the TR4 section – there are several articles about the TR4 there as well as a ton of information about my Ecotec powered Triumph TR6.

We built my TR6 first, and after Jim saw how much fun it was, he built the TR4 for himself. If you want even more information, you can read about the the TR4 and the TR6 in this blog.  The details of the construction of my TR6 are very similar to the TR4 since they have the same basic frame, engine, gearbox, rear-end.  The TR6 of course is a bit different but you get the idea.

If you have any questions, feel free to leave them on this page and I’ll do my best to answer them.

 

1985 Chevy C10 Silverado Squarebody

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1985 Chevy C10 Silverado Squarebody

This post is about my 1985 Chevy C10 Silverado Squarebody pickup, powered by an L98 Tuned Port Injection (TPI) engine from a 1990 IROC Camaro.  This is an old-school conversion, that my late cousin Jim Thompson did many years ago.

I have put about 800 miles on the truck during the last few months and so far, it has been a blast to drive.  The Frost White (RPO 12) paint is not as shiny as it was when new, but it is original.  For a 40 year-old truck, the body is still free of dings and most important, no rust.  The interior still has the original blue carpet and the bench seat has a stylish ‘blanket’ cover – as George Takei would say, “oh my!”.

Short History

The truck was driven by it’s first owner until sometime in January of 1988, when the second owner acquired the truck with 32k miles.  Second owner was a friend of Jim’s and sold the truck to JIm’s mom in the fall of 1993, with 101k miles.  Since then, the truck has been a member of the family.

According to the RPO build sheet in the glovebox (see below), the truck was born on April 26, 1985 powered by an LE9 5.0L V8.

Google Search result for the LE9 5.0L V8…

According to Jim’s documentation I have found, the engine started to give trouble and somewhere around the 130k mile mark, Jim decided to pull the tired engine and update it with an L98 Tuned Port from a 1990 IROC Camaro.  The gearbox is a 700R4, also from the IROC.  From the notes I found, Jim bought the IROC engine with about 32k miles.

Today, the truck shows 175k miles.  So doing the math, the Tuned Port has about 77k miles.  Barely broken in, right?  Hehe…

This is the RPO build sheet in the glovebox.  Unfortunately, I do not have the window sticker – wonder what that would look like?  No telling what this truck sold for back in 1985.  I’ve found some videos on youTube from the day, and the Silverado was “the” truck to have.

More About the Truck…

Jim had a thing for Squarebody C10’s.  He had two, actually.  The ‘shop truck’ was a tan 1985 that was once-upon-a-time in the US Forestry Service.  It was a plain-jane C10.  No carpet, no headliner.  Jim put an LSx in that one, and it was a ton of fun.  I could not keep it all, so the ‘shop truck’ has a new owner now.  This is what it looked like:

Dig that custom aluminum front bumper…

Thes second Squarebody is the Frost White C10, and has always been a bit special, perhaps because his mom (my aunt) drove it for many years.  After my aunt passed, the truck did not get driven much.  That would account for the 175k miles after 40 years.

The interior is a bit tired…  Blue carpet and blue accents on the doors – all original.  The seat cover – well, can’t beat the ‘blanket’ cover look…Next, high tech from the 80’s…  Dig those power window and power door lock switches.  Too bad the boys from GM decided to run full voltage to the window motors and locks through the switch.  Not so good after 40 years because the windows would barely move up or down.  I re-wired both doors with relays and now the windows go up and down smooth as they did in 1985.  The door locks work flawlessly with that period correct “click”.

The dash is still decent under that blue cover…The radio still works. When it wants to.  And there are four (4) speakers that work very well, mind you.  I’ve noticed when the radio gets a bit warm, it will play intermittently.  On the list to fix is a new period correct replacement.  All instruments work, even the clock.  Speedo is off by about 5 mph.  I suppose the reluctor wheel on the 700R4 is slightly different from the one that was in the original tranny.  No worries, I’ve checked this with the iPhone app and it is consistent across the range.  Lucky it shows under rather than over actual speed…

Tilt wheel works, turn signals, headlights, check.  There is no cruise control though – who needs it?  Ditto for the windshield squirter thinggies.  And there seems to be some malfunction with the dome light.  Oh and the horn does not work either.  I need to add all that to the list of things to fix.

Check this out…  Sliding rear window!  Oh and it is nice to lower the windows, open the rear window and have a nice breeze in the cab.

About that Tuned Port Injection L98…

I think the L98 has always been a favorite of mine.  The L98 powered Camaros and Corvettes of the era.  Yeah, it ran out of breath quickly but that intake with those 8 runners each going to the intake ports of each cylinder was sexy as it gets.

But wait a minute…  The photo above shows four siamesed runners.  What’s up with that, where are the 8 runners?  Well, back in the day this intake was very special.  This is the SLP high flow version.  This was supposed to gain you a ton of foot-pounds and make your car run better.  This setup was not cheap.  Does it live up to the hype?  Who knows…  Hehe…

I do have a set of original runners, but they are a major pain in the ass to swap.  Given this has not been touched in years, I will leave this alone thank you very much.  The last thing I want to do is break a bolt and then be up the creek.

Engine management you ask?  This is controlled by an OBD I ECM.  There was an outfit called Street & Performance in Mena, Arkansas that made a killer wiring harness.  Jim had a contact there that was on speed-dial on his phone.  Tony was his name.  We used to call Tony and he would help us out with L98 and LT1 setups.  That guy was a genius.  No telling what happened to Tony but that is who Jim got the harness from.  I don’t think Street & Performance exists anymore.  But back in the day, they where the shit when it came to this kind of stuff.

This photo shows a closeup of the siamesed runners.  They have a partition inside but the first inch or so, is the entire width of the runner.  Towards the back of the intake is a cover that hides the HEI distributor.  The Camaro came with a cheap, plastic version.  What you see in the photo above is the Corvette version – it was all metal and fits and looks nicer than the cheap plastic one.

“Does it have AC?”, you ask…  Well yes it does!

“Is it cold?”…  Hell yeah, it is!!!

Jim mounted an aftermarket compressor.  This enabled the use of modern refrigerant, not Freon.  Yeah, he added a big-ass condenser in front of the radiator and yes, it works.  We have cold air!  Not too shabby for a 40 year-old truck.

Another problem that I recently fixed was the vacuum check-valve leading to the vent system in the cab.  The only thing working was the heater vent.  The dash vents did not work.  Googling and watching some youTube videos pointed to a possible issue with the check valve.  Sure enough, a couple of bucks fixed that.  Now all vents work.  Even the defroster works!  Amazing what you can learn on youTube.

A keen eye will notice the absence of radiator fan.  Right?  Well, Jim was very fond of SPAL fans – that is what those Italian red cars with the little prancing horse on the hood come equipped with too!  This is what the air movement mechanism looks like…

Two 13″ SPAL electric fans keep things cool.  One is wired to a thermostat pickup plumbed into the bottom coolant hose and the other is wired into a trinary switch on the AC side of things.  So when refrigerant pressure reaches a certain point, it kicks the fan on and this keeps the refrigerant happy.  Brilliant!

Here is a picture of the red-top Optima battery.  I added the quick disconnect to prevent it from draining down.  Behind is the custom made overflow tank – Jim made that from aluminum.

Oh and check this out…

Lurking behind the grill is a MOCAL cooler.  Its plumbed as a transmission oil cooler.

And, I added the #3 tag.  Long live The Intimidator.  My friend Mike said this was a very “period correct” accessory.  So there.

What about cooling engine oil?  For this, we need to check out the oil filter.  Have no idea what this originally came on, but Jim decided to hang the largest oil filter he could find.  Check out this monstrosity of a filter:

8 inches long – this is a righteous sized filter!

This will hold an extra quart I suppose, and is also giving more surface area to keep engine oil cooler.  And we can get away with that because this is a C10 – try this on an IROC…  Yeah right!

The other side of the L98.  Unfortunately the cast iron headers were not JetHot coated.  They are rusty and I can’t imagine how hard it would be to get those bolts off.  So they stay put.

In Closing

When I first started driving the C10, it would shut down at red lights for no good reason.  Turns out the intake where the butterflies live was filthy, covered in carbon residue.  I took the idle air controller out and replaced it.  It helped some.  So I took throttle body apart and cleaned it in an ultrasonic cleaner.  What a difference that made.  Bought some new gaskets and put it back together.  That solved the problem.  If you don’t have an ultrasonic cleaner, get one.  Amazing what you can do with that piece of kit.

I bought a new set of tires and had them mounted.  The old tires were just unsafe.  Yes, I’ve thought about getting a set of drop-spindles and maybe relocating the rear spring to lower the truck.  I asked Jim about this time or two, and he would always say “leave it stock”.  So for now, it stays stock.

The truck is fun to drive.  I’ve had many thumbs’ up from other folks at red lights.  Yeah, this is a keeper.  It runs decent, just have to remember this is not a modern LSx and the 700R4 is dated, but for what it is, it does the job very well.  I also have to remember the rear-end is a 2.73 and is not a posi.  But, it is plenty fast for what it is.

Does anyone know where this dealership might have been located in the Upstate of South Carolina back in the day?

Thompson Wood Lathe – For Sale

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Please click on any image for a larger version of the picture.

For more information please check an entry in the American Association of Woodturners with more information about this lathe for sale – CLICK HERE.

New Fuel Pressure Regulator and Braided Lines

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On this 2023 July 4th weekend, bowtie6 got treated to a new fuel pressure regulator and braided lines.  The old setup consisted of a GM style non-adjustable pressure regulator and a set of E85 resistant rubber fuel lines – I wrote an article about that (click here).  I was never really pleased with the rubber hoses because the braided lines are much nicer and bullet proof.  So I pulled the trigger and ordered parts for the new setup.

This is what the old setup looked like:

The new regulator is a high pressure version from Aeromotive with a matching fluid filled gauge.  This is the setup after the first fitment.  However, with all this bling that bracket just did not look good…And this is what I mean…

We had to cut the old mount and in the process the aluminum mount got scratched up pretty bad.  I tried to sand this down but didn’t make much progress.  Instead, why not just use some carpet material?

Ah! Much better!  A keen eye will also notice the difference in pressure.  I checked what the E67 PCM expected, and that was 58 lbs/in, so I bumped that up a bit.

The photo above, shows the whole setup.

  • On the left the box with the silver lid holds the high pressure fuel pump
  • The line going up from the pump goes into the regulator and from there is a return line back to the pump container and to the left the line going to the engine.  That is a hard stainless line that goes under the body to the engine compartment.
  • And finally the lines that feed the pump container.

High pressure fuel pump inside this enclosure

I’ve written about this setup in a prior post Ecotec Fuel System and ECOTEC Fuel System – Part 2 in case you want to read more about that.

And this is what the front looks like.  This is another braided line going into the fuel rail.  The other side connects to the stainless tubing under the frame of the car…

How to Control Electric Cooling Fans with an E67 PCM

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E67 PCM and the C1, C2, C3 plugs

In this article I’ll go over how to control electric cooling fans with an E67 PCM.  I thought it might be nice to put this down in this long post in an attempt to help somebody else figure this out.  But first a little background…

HPTuners is our preferred method of modifying the engine computers (PCM’s) on the engine swaps I’ve helped my cousin Jim with through the years.  The tool consists of an interface that connects to the OBDII port on one side, and a USB adapter on a laptop.  There is the Editor and Scanner software components that let you do pretty much anything you want.  The proverbial catch is, there is so much to learn and not enough time…

I got an email from the good folks at HPTuners with an offer to upgrade our interface to the latest-and-greatest.  Included with the deal were several credits, so why not?  Well, this fired up my curiosity – once again – of getting bowtie6‘s PCM to control the SPAL electric cooling fan fitted to the radiator.  I say “once again”, because I have been down this path before with sub-optimal results.

The First Attempt

Engine management of the Solstice sourced ECOTEC in bowtie6 is handled by the  E67 PCM.  This PCM interacts with the engine by way of a modified Solstice wiring harness.  By this I mean, many circuits have been removed, such as anything to do with Air Conditioning – for example, the wires and plugs for the compressor, pressure sensors etc.  The wiring harness meets the PCM via 3 plugs:  the C1 plug has 56 pins and the C2 and C3 have both 73 pins.

When Jim and I prepared the wiring harness, we removed the wires that handled the fan relays.  We used a separate fan controller made by Centech as shown in the following picture:

Centech cooling fan controller

The controller makes ground and is connected to the fan relay.  The controller also receives a signal from an engine coolant temp sensor – NOT the one used by the PCM, instead Jim made a special adapter in the cooling system that houses the temp sensor for the Caltech device.  in the picture above you can also see a small knob on the left, and that is where you control when the fan “starts”.  So for all these years the fan has successfully been controlled by this device.  But in the back of my mind, the PCM has the ability to do this so why not let that control the coolant fan?

The Solstice comes with two coolant fans controlled by two separate pins on the harness.  The PCM makes ground, and in the stock setup they are connected to the control side of the fan relays.  I have only one fan installed in bowtie6 so in theory, I figured I could use the FAN 1 wire, connect it to my fan relay and that would control the fan.

Fully shrouded SPAL high-speed cooling fan

And much to my surprise, the PCM as it reached the fan “ON” temp, would ramp up the engine by adding a few more RPM’s and after a short delay, the fan started.  I thought “success!”:  the fan ran, extracted heat from the radiator and I was able to see the engine coolant temp come down.  But wait…  The fan refused to stop.

All this was done many years ago, soon after we got bowtie6 on the road.  I spent many hours trying to get this figured out, with no success.  I posted on the forums but went nowhere.  So, i gave up.  I left the wire in the harness, going nowhere.

The Second Attempt

A few weeks ago, after the new HPTuners interface came in, I decided to re-visit this issue once again, so I gave it a go.  I thought that surely, after all these years have passed there would be a solution somewhere on the web.  Well, not really.  I had to put together a few bits and pieces from several forums to find the solution:  turns out the E67 PCM needs to know how fast the vehicle is going and factors that in controlling when the fans turn OFF.

When we installed the Solstice sourced LE5 ECOTEC, we also included the Solstice’s 5 speed AISIN manual gearbox.  This gearbox was used in the Solstice/Sky as well as the Colorado pickup.  On the side of the gearbox is a reluctor that sends out the vehicle speed signal (VSS) to the PCM.  And this is done via a twisted pair of wires, a purple wire with the LOW signal and a yellow wire with the HIGH signal.

In my setup, I used the VSS signal to make the VDO speedo work.  The VDO speedo requires a constant pulse and the VSS signal worked perfect.  The VDO speedo has a “learn” mode where if you travel a mile it calibrates the pulses sent by the VSS and that translates to an accurate speed.  Sure enough, all this worked and is accurate when checked with a GPS signal on my iPhone.

Since the fitted gearbox is a manual, my research indicated there is no need to send the VSS signal to the PCM.  So we took out the VSS wires and pins when we modified the harness.  This left the PCM clueless as to how fast the vehicle is traveling.  And along with that, since the PCM had no frame of reference for speed, the fans would never shut off.

Solving this problem then, starts by splitting the signal from the VSS to a) feed the VDO speedo, and b) send the signal to the PCM.  It took a little effort but I did just that and found the correct location in the correct connector to supply the VSS to the PCM.  If you look at the photo of the PCM you will see I labeled with a Dymo tape, the three plugs – C1, C2, C3.  Suffice to say, it is much easier to modify the harness on a workbench than on a car already installed!  This can get confusing.

VSS Settings

I fired up the HPTuners Scanner and went for a drive.  The speedo signal was now showing but it was off.  And this comes as no surprise.  The PCM still had the original Solstice settings.  So the first change with the HPTuners Editor, was to enter the proper tire size and rear-end ratio.  Once I entered that in the Editor and downloaded that to the PCM, speed now shows dead-nuts on the Scanner.  I suppose for the purpose of the fans this might not be really necessary, but if we are going to go through all this trouble, might as well do it properly.

Fan Settings

The Solstice has two cooling fans.  They are controlled by relays and the ground on the control side of the relays is connected to two pins on the PCM.  One is labeled as “High Speed fan” and the second as “Low Speed fan”.

Since I did not want to go through all this trouble and still come up empty handed, wired up a spare relay base and relay, and connected a test light so I could make sure I had the right fan wire coming out of the PCM.  Using the HPTuners Scanner, there is a page where one can manually command a fan to come ON or OFF.  And sure enough, the test light came on when the high-speed fan was selected.  Next, I removed the test light setup and the fan relay instead.  I did the dry-run again and this time the relay clicked and the fan started up.

Now to the fun part.  First, the main Fans page:

Fan Settings

For starters, the Fan Type:  I have left the fan as “Discrete”.  The other option is Pulse Width Modulated (PWM).  The discrete fan settings is used when the PCM is controlling a relay for an Off/On type setting.  The PWM setting is for when a fan that can run at different speeds is installed.  For the purpose of this post, I am working with a relay to control the fan.

Also, note where you can select the Number of Fans Fitted.  In this case, I left it at two.  More on this later.

Next, comes the confusing part.  The E67 PCM has to two tables that control fan behavior:  Fan Desired Pct vs Engine Coolant Temp (ECT) and Fan State Transition Desired % vs Current State:

Fan Desired Pct vs Engine Coolant Temp (ECT)

Fan State Transition Desired Pct vs Current State

The top chart is used to set the coolant temp required to turn the fan ON or OFF.  The bottom chart is used to set when the fan should turn ON or OFF.  Confusing?  Join the club.

OK – this is what I have so far:  I have left the Number of Fans Fitted at two.  Therefore this means we have a “Low speed” fan and a “High speed” fan as far as the computer knows.  I wired the “Low speed” ground to the relay control side.  Since I don’t have a second fan, the “High Speed” fan is irrelevant.

The “ON” conditions:

  • By reading the charts above, the “Low speed” fan transitions to the ON position with a Fan Desired setting of 36 (the 0->1) and that translates to ~214 degrees on the top chart.
  • If I had a second fan wired in, then the second fan would be ON at Fan Desired setting of 56 (1->2) and that translates to ~225 degrees on the top chart.

And now the “OFF” conditions:

  • If I had a second fan wiring in, the second “High Speed” would be OFF at Fan Desired setting of 48 (2->1) and that translates to around ~221 degrees on the top chart.
  • Finally the “Low Speed” fan (which is fitted) turns OFF at Fan Desired setting 28 (1->0) and that is ~210.

BUT remember, the only time the fan actually turns OFF is when the vehicle is moving.  So at a red light, the fan would continue to run even though coolant might be below ~210 degrees.  It is only when the VSS sends a signal the vehicle is traveling at ~15-20 mph that the fan will actually turn OFF once the ~210 threshold has been met.

In Summary

I have been able to successfully test the above settings.  The one SPAL fan does kick in at roughly ~214 degrees.  Once engine coolant reaches 214, I can audibly confirm the engine speeds up slightly and then after a slight delay, the fan kicks in.  If you look at the Fan Settings screenshot, you can see there is a Startup Delay setting.  I compared that to the settings on my 2014 Camaro SS with an L99 V8 (I know, apples and oranges) and for the Camaro, the delay is zero.  But duh, double the cylinders so I suppose in that case it does not matter.  For an engine with half the cylinders, this gives it a few seconds to “ramp up” before the hit of the fan kicking in.

The next experiment will be to play with the Number of Fans Fitted setting.  I ran into self-inflicted error when I wired up the single fan:  I wired it as the “High Speed” fan.  Clearly that was a mistake because the first fan to kick in is the “Low Speed”.  Wha happened when I did this was the fan would turn ON after coolant had reached ~225 degrees.  So the take-away here when using only ONE fan, is to use the “Low Speed” pinout to make ground in the relay control circuit.

This is a very long-winded version of my experiment.  And I know, might be a little confusing.  Especially the last two charts above.  I am still trying to wrap my head around all this.

But what about PWM?

Ultimately this is where we want to be.  I had a very long talk with my friend Michael Y. and we talked about PWM fans.  Michael has extensive knowledge of this and I tried to draw from his experience in the matter.  Perhaps we might get lucky and he might give some words of advice in the replies section.

The big advantage of the PWM fan would be to try to keep coolant temps consistent, rather than the way I have them in my purely ON/OFF settings.  In my case, the primary goal is to keep the engine from overheating at stop-and-go traffic.  But, it ultimately it would be nice to have the one SPAL fan running as a variable speed setup.

Griffin aluminum radiator – image taken from the bottom of the radiator facing forward

Width of Griffin radiator