LFX Engine Swap (GM V6) at GWR

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Re: LFX Engine Swap (GM V6) at GWR

Postby Ryan @ GWR » Thu Jul 11, 2019 11:02 pm

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Re: LFX Engine Swap (GM V6) at GWR

Postby Ryan @ GWR » Sun Jul 14, 2019 11:11 pm

Fresh 22k mile MV5 transmission going in. One of the few times I can say something cost less than the Miata equivalent. :lol:

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Went to drill and tap the case for the temperature sensor and turns out that unlike the MV7, the MV5 has a temp sensor just below the fill port, very similar to the place I added a sensor on the MV7. One 1/2" to 1/8" NPT adapter and the sensor's mounted.

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Re: LFX Engine Swap (GM V6) at GWR

Postby Ryan @ GWR » Tue Aug 27, 2019 10:03 pm

In Miata terms, we're making good power. But we're the underdog by a huge margin against the cars we compete with. No doubt, we make the most with what we have, but with the largest Time Attack event moving to Circuit of the Americas where horsepower reigns supreme, I knew we needed to turn the wick up. We'll always be down on power compared to the other guys, but that doesn't mean we can't give David a bigger rock against Goliath. However, save for some transmission hiccups, reliability has been one of our strengths and I did not want to sacrifice that. I had an idea.

This didn't happen overnight. I've been working on the solution all year in the background.

A year ago, I placed a Rotrex on a box beside my spare motor, and got started:

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The first time I took this C38-92 out of the box I realized the challenge I had ahead. I'm used to the C30 units used on Miatas, and had that size in my mind when I was initially looking at the space in the engine bay, placement, etc. The C38 is a behemoth. It would turn out that packaging would be one of the largest challenges at just about every step in this project.

In July I posted this teaser, focusing on the new rolling engine lift. Only a few people noticed the blower hanging on the side of the motor :wink:

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That was after months of work on the bracket, and the final is actually version 3 after scrapping two prior. That gets expensive when you're cutting 7000 series aluminum, but it has to be perfect. Clearances are mere millimeters everywhere, and rigidity of the bracket is critical to avoid having belt issues.

The frame rail had to be cut substantially and reshaped, with care taken to add new internal structure to ensure loads from the suspension are still transferred through the frame rail appropriately.

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The subframe also had to be cut. :shock:

Did the math on pulley sizes and picked a few final candidates to test. We will not be spinning the blower to its redline, no running on the ragged edge here. Then ordered lots of belts and worked out a suitable belt for every pulley:

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The packaging challenges continued with the coolers. I needed an intercooler and a cooler for the Rotrex fluid in addition to the engine oil cooler. I also wanted the shortest charge piping possible, made a bit more complicated with the throttle body at center top of the V6 rather than on the side of an I4. Off the shelf intercooler options weren't going to work, I was going to have to make it. I chose a Vibrant core with the right dimensions for what I had in mind:

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To hang everything in place I had to toss the old radiator mounts and make an entirely new frame to hold everything tightly together:

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I’ve never made intercooler endtanks before. This project was going to give me a lot of practice on the TIG welder. Drew up and cut pieces to make up the endtank:

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The top tank took a while with a tube hand notched mid-bend to merge into the curved tank:

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Finished intercooler after quite a bit of welding.

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Welding the tanks to the core was a next-level learning experience; you’re welding a butt-joint with the core quadruple the thickness of the endtank, and the core by its nature is trying to suck all the heat out of the weld as you go. Rather proud of how it turned out.


New coolers in new locations meant making all new lines:

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On to the intake, and more packaging challenges. I did the math on filter size for expected flow. The filter I had was big for a Miata. The new filter is massive:

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The intake tube for the C38-92 is 3.5” and that does not want to fit… anywhere.

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More fun welding:

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In terms of sensor and component locations, there was some debate about what locations would work best. I made a couple different configurations for charge piping to try the options:

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Using a TiAL QRJ blowoff valve, configurable for either recirculating or vent to atmo. Which MAF sensor location we found worked best would determine which config we wanted, so I did both VTA and recirc setups:

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The recirculating config uses a hard line that was fun to bend:

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The Rotrex points the air inlet straight back, directly at the downpipe. So inevitably, the silicone bend is riiiiight by the exhaust. To give the coupler the best darn shot at nice long life possible, both coupler and downpipe are wrapped, and then separated by a titanium shield with a reflective layer on the hot side:

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Crankcase ventilation becomes critical when adding boost. A direct injection engine really benefits from catch cans even naturally aspirated, so it had been on my to-do list for a while. Since this is a race car only I simplified things a bit. Eliminated the PCV, drilled out and tapped both valve covers, and ran lines to a pair of catch cans that vent to atmosphere. With so little space in the engine bay, I ended up placing the cans in the hole that the HVAC system pulls air from on a street car:

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The fuel side is tricky. Direct injection can’t be easily upgraded with aftermarket parts the way a traditional fuel injection setup can be. Expecting that we might find we need more fuel than we could flow on the stock system, I preemptively bought a high pressure pump from the Cadillac ATS-V (which runs the twin turbo LF4 engine), to see if the pump would swap in on the LFX:

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It is almost identical. The only difference is that the plunger is ~0.100” shorter.

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After some measuring we felt pretty sure that the lowest point on the cam lobe that drives the high pressure pump was tall enough to maintain contact with the LF4 pump so we swapped it in on the motor in the car. That is not a fun job. Think coolant reroute but with the engine even closer to the firewall and more stuff in the way.

Colder spark plugs were in order:

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It’s all a big paper weight without tuning. That is outside my wheelhouse, and I wanted someone who really knew their field and would give the car the time and attention it needed. For this I teamed up with UMS Tuning. I consulted with Tony through the final stages of the build to ensure everything was configured the way he felt would get us the best run at all things working smoothly. With everything done he made some tweaks to the calibrations of a few sensors on the old tune for startup. It fired first try and idled pretty well.

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Pulled it out of the shop, first time sun hit the car since February!

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Then loaded up for the 350 miles tow to Arizona to get tuned.

More to come...
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Re: LFX Engine Swap (GM V6) at GWR

Postby Ryan @ GWR » Tue Sep 03, 2019 12:35 pm

Off to AZ to take the car to UMS Tuning. They weren't the closest option for me, but that wasn't my priority. I wanted to put the car in the hands of someone who I knew understood what I needed and would do the job right. Tony knows we aren't looking for a number to brag about or just a full-throttle tune to get me down a drag strip. It needs to drive smooth, be predictable at partial throttle and in transitions, and be reliable.

I had already been consulting with Tony on configuration details, tapping into his experience with tuning modern GMs so that the ECU would be happy with everything and give us the best shot at all my hard work translating into positive results. So I towed the car 300+ miles through 110° F Arizona summer to get Hyper in the right hands. With swamp coolers, temps in the shop were a humid ~90° F which is about worst case scenario for what we'd see on track.

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Hyper was on the dyno all day. Like, 9:30 AM to 9 PM. Lots of time spent on details, playing with cam timing, swapping things back and forth to see what worked best, different pulley sizes, etc.

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Now I know EVERYONE wants numbers, but that is going to remain confidential. I'm extremely happy with the results so far. I'm considering where we're at now 'stage 1', with two pulley sizes available dubbed "extra conservative" and "conservative". We're up against a fuel flow limitation on the current hardware with E85, so cannot run any more boost until we sort that further. Once we do, we can throw a tad more boost at it for a 'stage 2'.

I will say that I had been expecting a rather peaky setup with the Rotrex, going by what I am familiar with on BPs, but the setup has exceeded my expectations there - it retains a very flat torque curve similar to naturally aspirated, just with much more torque than before. Horsepower grows linearly with rpms with the largest gains up top, just like expected with the Rotrex. This is exactly what I was aiming for: all the good stuff about the engine package we have, just turned up a notch or two.

To avoid the pitchforks and riots I'll give this away: we're currently putting better power and more torque to the wheels than a Ferrari F430 on similar dyno.  :twisted:

Since we have Miata Reunion @ Laguna Seca coming up where I'll need to run the big muffler, I have the alternate down-the-center rear exhaust on the car. One of the few times I get to hear it sounding more like a traditional V6:



Can't wait to get in the driver's seat and start shaking it down. First up is a local autocross this coming weekend where I can make sure nothing major is falling off the car and things are operating as expected, then I'll be scheduling some track testing time in the next few weeks.
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Re: LFX Engine Swap (GM V6) at GWR

Postby Ryan @ GWR » Wed Sep 18, 2019 4:54 pm

So I did some autocrossy stuff just to shake things down and see what wants to fall off. The answer turned out to be absolutely nothing, ran flawlessly. It was pretty goofy trying to tip toe this thing around cones in a bumpy lot with it set up for the completely opposite end of the spectrum. Only a few short spots I could really use throttle but for those brief moments, oh man, it's moving.

Track testing this weekend. Much excite.

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Re: LFX Engine Swap (GM V6) at GWR

Postby Ryan @ GWR » Wed Sep 18, 2019 11:33 pm

Oh yeah, almost forgot. Two years ago at Laguna Seca I was having trouble passing the 104db sound limits with the side exhaust. So last year I put together a Laguna Seca specific exhaust; entirely different config with downpipes going down the center tunnel and merging just behind the transmission, then 3" all the way out back, small resonator in the tunnel and then the largest Magnaflow muffler I could find under the trunk space. I didn't end up going to Laguna Seca last year so I never got a chance to use it.

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Always improving:

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Local autocross is a strict 91 db limit, and with Miata Reunion right around the corner it was a good opportunity to make sure this exhaust was doing the job. No issues during the autocross. I daresay I could probably even run this car on a normal 92db sound limit day up there!

This config is obviously much heavier than the usual side exits, so those will be back for GTA Finals at Buttonwillow.
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Re: LFX Engine Swap (GM V6) at GWR

Postby GlennR342 » Sat Oct 05, 2019 10:59 pm

Do you have any issues with oil surge? I haven't read the entire thread but can't remember if you were running a dry sump?
Is the oil pan stock? Any mods to the pickup?
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Re: LFX Engine Swap (GM V6) at GWR

Postby Ryan @ GWR » Mon Oct 07, 2019 8:43 pm

GlennR342 wrote:Do you have any issues with oil surge? I haven't read the entire thread but can't remember if you were running a dry sump?
Is the oil pan stock? Any mods to the pickup?


Still a stock wet sump. The oil pan is modified by V8R for ground clearance, but that just means the lower inch or so has been chopped off. The stock baffling is still intact. I'm quite pleased to say we've had zero oiling issues at sustained 2 g's laterally... very drama-free, quite unlike the Chevy V8s. :wink:
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Re: LFX Engine Swap (GM V6) at GWR

Postby Ryan @ GWR » Tue Oct 08, 2019 10:11 am

Got a shakedown in at Streets of Willow, working out some kinks and relearning the car. Even over weight with the Laguna Seca exhaust and a passenger I was thinking the car felt quick, drag racing with an Audio R10 down the straight, and then in a later session I switched over to a secondary page on the dash display and saw I was only making about half the boost I should've been.

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Worked out several other details while there, and towed home with a new top priority: find my boost!

Made some DIY caps for the intake piping so that I could pressurize the system and started the hunt. The primary issue was immediately obvious; there was a significant leak in the intercooler core itself. I couldn't put air in fast enough with the shop air to even build up any pressure.

Pulled the intercooler off the car and tested it alone, and found there were a dozen or so points in the core where pressure was leaking out between the bars significantly. So I had put a chunk of hours into building this custom intercooler, not knowing that the core was defective from the start. We suspect it was leaking less initially which is why it made pressure on the dyno, and then worsened after being bounced around and stressed. Not the news I wanted, but I was glad to have something in my hands that I knew was the cause (the worst part of an issue is not knowing the cause).

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I dove into making intercooler #2, and because we had seen super happy IATs with the first intercooler I decided to take this opportunity to use a smaller core for #2 to try to cut a few pounds. This time I used an off-the-shelf intercooler that already had endtanks to try to cut down on fabrication time a bit... but the inlet and outlet still had to be modified so it really didn't save much.

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Intercooler #2 held pressure perfectly:

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With the new intercooler in place I was able to pressure test the full system and pinpointed a few more smaller leaks. The seal between each coupler and pipe can be quite finicky. I'm using a combination of Murray clamps on the thin wall aluminum tubing and T bolts clamps on a couple of the thicker wall connections, like the outlet of the supercharger. The T-bolts actually deform the thin wall aluminum tubing, which I saw first hand on one of my pipes, so the Murray clamps are better in those locations, but they aren't without their finicky nature either. The one connection that never had any issues was the Vibrant HD clamp in the cold side piping. I also found a small leak in the blowoff valve fitting.

A quick side note, this highlights one of those inherent differences between turbos and superchargers that you don't really think about until you're dealing with it. A supercharger is far more sensitive to boost leaks than a turbo; up to a point, a turbo will compensate for leaks in the system by just spinning more until the wastegate sees the target boost achieved. A supercharger has no way to compensate, it spins exactly the same as it did without leaks, and any pressure lost to a leak is just lost. All in all, this was a good learning experience about how sensitive things can be to leaking, and I'm making pressure testing a routine step in the future any time anything in the charge pipe system is disassembled and reassembled.

Switching to fuel, at the track datalogs showed fuel was struggling a bit more than before. Then a few days later while idling in the shop the pump quit completely. Rather than swap in another Deatschwerks DW300, to be sure the low pressure side of the fuel system could supply anything we asked of it I decided to switch from a DW300 pump to a DW400. The DW400 is a big pump that doesn't really fit the Miata, but I modified the pump fixture and brackets to make it work. Then I redid the high current pump circuit with heavier gauge tefzel wire, larger fuse, etc. so that we can run the pump properly, even at the 20+ amps it draws at high pressure if needed.

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Booked a local dyno to verify everything was sorted. Numbers didn't matter, just wanted the data logs from a few pulls. Everything is back in the green, but seeing 1.0-1.5 psi less now than in our first round of tuning at UMS, with a small but definite delay in the ramp up in boost when plotted by RPM.

Leading theory at the moment is that the smaller intercooler is causing a more significant pressure drop. To test this I'm going to add a second boost sensor in the hot side charge pipe so we can see the delta pre and post intercooler, and depending on what we find I might have a third intercooler build in my near future. We'll see.

But for now, it's running well and making decent power so it's buttoned up and going in the trailer tomorrow for Miata Reunion at Laguna Seca.

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Re: LFX Engine Swap (GM V6) at GWR

Postby Brian » Mon Oct 14, 2019 4:56 pm

New Miata Lap Record at Laguna: 135.2
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