LFX Engine Swap (GM V6) at GWR

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jboemler
Posts: 304
Joined: Fri Oct 10, 2008 6:15 pm
Location: Mukilteo WA

Re: LFX Engine Swap (GM V6) at GWR

Post by jboemler »

Hmmmm, glad to see the progress, but it doesn't strike me like a great design. Unlike the Mazda design, where the shifter is a part of the trans, this one will get bolted to the tunnel. That means that when the drivetrain twists or vibrates, it will be translated as angular movement to the shifter, and multiplied by the ratio of top to bottom lengths of the shift lever. Bottom line, the car is going to shift like American Iron, when it could have been made to shift more like a Miata. :cry:
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Engine Bay Modification

To gain clearance for the wider V6, there are some adjustments to be done to the engine bay particularly so that the engine can sit as far back as possible for the best weight distribution. One very nice thing about this swap is that this motor and transmission do not need any modification to the transmission tunnel/firewall to clear the bell housing like the V8s do. With the V6 you only need to make a few changes to the engine bay itself.

The below pic is a stock photo of a stripped engine bay on which I've marked where the work is done.

The primary change is to the rear corners where the frame rails meet the firewall, these areas get squared off via cutting and welding as marked. The area around the heater hose holes in the firewall (circled area) just needs some massaging with a mallet to clear a protrusion on the rear of the V6's driver-side head:
stock bay cuts.jpg
After some cutting, we can see the internal structure. There is still a bit more cutting to do, as marked by the green lines:
Driver side engine bay cut.jpg
Passenger side engine bay cut.jpg
With the final cutting done, we made new plates in house to seal this area up, with accommodation for the steering rack to still pass through the driver's side section:
DR side bay cut 3.jpg
Px side bay cut 3.jpg
Lots of welding later, we have plenty of room for the V6:
Squared engine bay.jpg
Because this is a race car, it made sense to take this opportunity with the engine bay stripped to also stitch weld several key areas while in here. This adds a lot of time to the project, but it's worth it - stiffening the chassis with essentially zero weight added. (Sorry for the photo quality, this was taken late at night in the shop with low lighting so it turned out grainy):
Stitched Engine Bay.jpg
In these photos you can also see the new subframe, courtesy of V8Roadsters, which is a tubular unit lighter weight than the factory subframe yet super strong and with the proper engine mounts for this new motor:
V8R LFX Subframe.jpg
For now all of the welded areas in the engine bay have some primer sprayed on them to prevent rust, the final paint will be done later once all of the test fitting of various parts is complete. With the subframe installed it's looking almost ready for the motor to go in for the first time:
Engine Bay ready for motor.jpg
Note in that photo the area by the heater hose holes hasn't yet been "massaged" for clearance.
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

jboemler wrote:Hmmmm, glad to see the progress, but it doesn't strike me like a great design. Unlike the Mazda design, where the shifter is a part of the trans, this one will get bolted to the tunnel. That means that when the drivetrain twists or vibrates, it will be translated as angular movement to the shifter, and multiplied by the ratio of top to bottom lengths of the shift lever. Bottom line, the car is going to shift like American Iron, when it could have been made to shift more like a Miata. :cry:
We shall see! This setup is already running in V8R's own test mule and shifting great I'm told. If I'm not happy with the shifting feel in this car, I'll revisit the design and see what needs changing, but only time will tell.
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Differential

We'll be using the tried and true Getrag limited slip differential for this - the same differential used in many V8 Miata conversions. It's a clutch type limited slip with smooth engagement that can handle all the power we can throw at it. Sourced from the 2006-2008 CTS and several other GM cars, it's available with a 3.23, 3.42 or 3.73 ratio. Those all sound long in Miata terms, but with the short ratios of the transmission we're using it's actually a great set of options. This particular unit is a 3.42:
Getrag_1.JPG
As a bonus, the Getrags all have their ratio labeled on the back side, so it's very easy to know which ratio you've got:
Getrag_2.jpg
Temperature sensors

We're expecting that this new motor should run with much less heat than my last setup but I never want to leave anything to guessing. This car will see lots of extended hard use on the track so it's a perfect platform to put everything through the torture test and answer lots of questions.

To keep track of the temperature of the various parts in the drivetrain we'll need gauges that can be monitored at the track. The Accutech SMI gauges that we have in our catalog are a favorite of mine - super accurate and yet affordable they're perfect for the job. I'll use four in total; one for engine coolant temperature and another for engine oil temp, and then two more oil temperature units for the transmission and differential.

For the diff and trans we used a scope to investigate inside the unit for a safe place to drill and tap the case to install the sensors:
Getrag_Sensor1.jpg
The differential has a perfect location in a casting circle on the passenger side of the unit (note it's the rear circle of two). These sensors have 1/8" NPT threads:
Getrag_Sensor2.jpg
For the transmission, a spot just below the fill hole was selected (red X):
MV7_Sensor1.jpg
The Accutech SMI gauge's included sensors have high quality sealed wiring, which is part of the recipe for their accuracy. Gauges are very sensitive to resistance, so wire-it-yourself sensors usually end up with the wrong resistance and are inaccurate from day one.
MV7_Sensor2.jpg
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Getting into the motor!

The new motor and car getting closer and closer in proximity...
Hello new motor.jpg
With engine on the stand there's a bit of prep to do, and I also wanted to poke around and get familiar with this new engine.

Going through the engine, cleaning each part as it comes off. Intake manifold is removed in these pics, wiring harness is off and crank pulley is removed (because we'll be swapping the pan), and you need to order a new crank pulley bolt as it is torque-to-yield:
LFX_1.jpg
On the back you can see the high pressure fuel pump and hard lines for the direct injection (1600psi!!!)
LFX_2.jpg
Intake manifold and throttle body drying after cleaning - the intake manifold is a composite to save weight, with just a small aluminum portion on the underside. Just about every part I remove from this motor impresses me with its weight, some parts are even lighter than the Miata's equivalents:
LFX_3.jpg
Front cover removed to get a look at the timing chain layout. Three timing chains which should be good for the life of the motor, no belts here. Variable valve timing on all four cams:
LFX_4.jpg
Some sockets that usually lie in the toolbox untouched in a Miata shop are getting some action on this new motor... 1/2", 15mm , 18mm, 22mm, etc.

Flipping the motor over with the pan removed we get a good look at the forged crank, very beefy 6-bolt main bearing caps (4 from the bottom plus two going in through the sides of the block) as well as the internal crank trigger wheel:
LFX_5.jpg
We're swapping oil pans to a modified unit supplied by V8Roadsters which has better ground clearance. Here's the stock pan beside the V8R pan. Convenient that we're swapping pans anyways since our LFX arrived with a big puncture in the bottom of its pan!:
Pan_1.jpg
Pan_2.jpg
Before the pan went on we drilled and tapped for the Accutech SMI engine oil temperature sensor just above the drain plug:
Pan_3.jpg
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

With the engine buttoned back up, first test fit in the engine bay!
LFX test fit.jpg
iniazy
Posts: 8
Joined: Fri Mar 30, 2012 10:13 am

Re: LFX Engine Swap (GM V6) at GWR

Post by iniazy »

Awesome build!
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Transmission and differential!

With the engine in place I can finalize placement of the rest of the drivetrain downstream.

Utilizing V8Roadster's frame rails and transmission crossmember which are intended for the GM MV5 (Camaro) and MV7 (Cadillac CTS) transmissions. The frame rail braces are great additions to just about any Miata because the factory rails are thin and get damaged over time, so it's a win-win to add these and have a mount for the transmission that is already figured out for us:
V8R Framerails and Crossmember.jpg
**Note the ratcheting strap: the chassis is strapped to the lift front and rear, with everything down to the subframes going in/out multiple times you don't want to need to keep track of how much weight is on each end of the car so it doesn't fall off the lift!

Transmission bolted up without issues. The transmission's rear mount bolts to the V8R crossmember which ties in with the frame rails, so leave the frame rails unmounted until you have the transmission bolted up to dictate their placement, and then drill and bolt the frame rails in.

V8R uses an energy suspension poly bushing in the rear trans mount. Here's the mount bolted up without the crossmember in place:
MV7 Crossmember Bushing.jpg
Here's the crossmember added. MUCH better ground clearance with this transmission than the T56s in the V8 swaps. :)
MV7 with crossmember mounted.jpg
Even with bolt-on parts sometimes there is a need to tweak them to work for your car, and here was a good example of that. Because this kit was designed around an NB, the crossmember interfered with the passenger side corner of the transmission tunnel and floor on this NA, which you can see in the above pic.

Looking at the pic below, taking this notch out of the crossmember fixed the interference and then everything could square up:
Crossmember notched.jpg
With the crossmember bolted up, the framerails could be bolted in their final resting place. Lots of drilling and then torquing bolts (2 person job - one person in the car with a wrench on top):
MV7 Installed.jpg
Checking the transmission angle. It's sitting at 1.7° nose-up here. With the rear trans mount torqued down it cinches down to 1.6°:
MV7 angle.jpg
Moving on to the diff!

V8R's diff mount kit includes a bracket that bolts to the two ears on the back of the Getrag diff which then slide up on to the same two long studs in the rear subframe that the Miata diff bolts to. The kit also includes two bare steel tabs that get welded to the subframe for the Getrag's front mount:
Getrag mount kit.jpg
V8R's instructions are to weld the front mount in so that the pinion angle is 1.5° nose-up, which looks perfect now that we know the transmission's angle.

Bolt the rear mount to the diff and then bolt that to the subframe. I forgot to specify I wanted the diff's factory mounting bolts when I got the diff from the yard so I had to source some - they're M14x2.0, two 45mm long for the rear and one 90mm for the front plus lock washers for all three and a nut for the front.

The rear mount has roughly the correct angle preloaded into it, so with the diff mounted to the subframe you just shim the nose as necessary to dial in the exact angle. I needed to shim the nose down a bit, you can see the shim stack in the background of this pic:
Getrag front bushing 1.jpg
Also pictured is the fun discovery that the front factory bushing was completely shot - it just popped out in my hand. Obviously this had to be replaced. Despite most of the bushing already being out, the tough part of the bushing removal was still to be done. You have to remove the steel sleeve that the bushing was once connected to. It does not come out gently:
Getrag front bushing 2.jpg
The factory design is prone to fast wear under hard use because it's soft and has a lot of air gap around the center sleeve. On a street car you'll want the factory bushing (Moog PN K200641), but for track use I chose a polyurethane replacement. There are a couple on the market, I settled on one from Creative Steel - this is the "street" durometer which is 75A. We air-hammered this in which was nice and easy. I don't envy someone trying to press this in considering the proximity to the housing:
Getrag front bushing 3.jpg
With that lovely side-track behind us, back to the front mount...

The two steel front mounting tabs are a "starting point" but need some grinding to clear the housing better. The front just got a bit of clearancing on the outer radius by the hole. The rear tab needed to be notched:
Getrag front mount 1.jpg
More than one way to tackle setting the pinion angle prior to welding, my method to eliminate variables as much as possible was to set the whole assembly on the bench and shim the subframe to dead level and then shim the diff to the 1.5°:
Getrag angle 1.jpg
Then tack-weld the tabs in place:
Getrag front mount 2.jpg
Rear tab tack welded in, you can see why the tab was notched:
Getrag front mount 3.jpg
These are tack welded ONLY at this point. Always test fit in the car and measure before finalizing. The car might not be dead level on the rack or jack stands, and that transmission angle that was measured is relative to actual horizontal, not to the car. Measure many, many times and weld once.

Turns out, the car is level on the rack :idea: Diff sits at 1.5° nose-up, matching the transmission's angle within 0.1°:
Getrag angle 2.jpg
Subframe comes BACK out again, and final welding can happen. Diff is removed from the subframe for this of course. I cut a length of steel tube to match the length of the diff's front mount and bolted that between the tabs while welding to prevent warping. Don't leave the diff in there to serve that purpose, you'll melt the bushing.
Getrag front mount 4.jpg
That's it! Subframe will get cleaned and painted now along with some other parts.
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Camaro gas pedal conversion

The LFX, like most engines these days, is drive-by-wire. That sounds good to me since I've lost a couple throttle cables over the years from nearby turbo heat. Naturally, the Miata pedal fixture needs some modification to accommodate the GM pedal.

The first and always lovely step was of course removing the drivers seat and spending what felt like an eternity removing the pedal assembly from the car while being jabbed in the back by harness eye bolts, seat brackets, etc. etc.

Stock gas/brake pedal assembly clamped to the table with some alignment marks for pivot point and such, and Camaro pedal nearby:
Pedal Conversion 1.jpg
The Camaro pedal is very similar to the Miata's in some ways such as length, angle and travel. However, the mounting layout is entirely different of course so a custom mount is needed in order to place the new pedal in just the same position as the one it replaces.

Stock pedal removed and unneeded mounting fixture cut off leaves the assembly on the left, plus a new additional mounting plate for the Camaro pedal to be welded on:
Pedal Conversion 2.jpg
The added plate welded on as well as a brace along the top to help keep the mount from flexing and studs added:
Pedal Conversion 3.jpg
New pedal mounted up. Pedal position matches the old setup with identical pivot placement and angle.
Pedal Conversion 4.jpg
With it finished, the fixture was bead blasted and powdercoated. Ready to be re-installed:
Pedal Conversion 5.jpg
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Location found for the SMI water temp gauge's sensor in the engine. This port is plugged with an allen head bolt, confirmed it goes to a water jacket because I got a face full of coolant when I pulled the plug despite having had the motor upside-down a dozen times..

That port is 1/4 NPT threads so with a 1/8 NPT Female to 1/4 NPT Male adapter the sensor fits perfectly.

Right side of the block:
coolant sensor.jpg
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