griff

Any word on how the fuel kept up with the airflow Ryan? Still trying to decide if a HPFP is worth the hassle to change it... given its difficult location.

ThePass

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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.



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.



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.

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.

alpinaturbo

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Ryan

Understand the confidentiality in terms of competition, but you could have thrown a basic number, to keep us from suffocating from curiosity. Even on pump fuel if you tuned on pump, before E85.

ThePass

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I'm seeing results very similar to what you described here:


@ 8.5 psi fuel juuust begins to fall behind. Commanded rail pressure is 20 mpa (2900 psi) and that tapers to 15 mpa in the last 1,000 rpms. Doesn't appear to be a shortage on the low pressure side because pressure there is 120 psi tapering to ~95 psi. When we checked that low side pressure we were really surprised to see it that high. The Corvette fuel filter is supposed to be pulling that down to ~60 psi, so it seems my filter is bad. That's getting replaced this week. But at any rate we weren't wanting for fuel on the low side. We have some curiosity about whether the LF4 HPFP might be under-driven by the LFX cam, but with the difficulty of swapping them, it wasn't something I could do while we were there. But, the fact that the LFX HPFP operates at 15 mpa, which is what we were tapering to, up top, makes me doubt that we'd see any better results on the LFX pump. I could be wrong about that, not sure yet.

I've ordered a LF4 exhaust cam (on national backorder) to check it against an LFX cam whenever it finally arrives. I've also ordered one LF4 fuel injector so see if it fits the LFX. We'll figure things out, just need to work through the variables. At this time I wouldn't suggest the LF4 HPFP until we know more.

LukeG

The NA numbers are in this thread somewhere. You gotta respect the man's desire to keep it quiet though. He is in a very competitive field and is trying to get close to the top.

Rough guess based on what we have seen on FI LFX setups is that he is 450+ whp on E85 and probably 400 with pump gas.

ThePass

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Thought about this a bit, and added this line for you:

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

LukeG

Scuderia or base model

ThePass

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I don't think there's much difference. But either way, they're 3000 lbs, and Hyper... well, isn't. So it should scoot.

griff

The LFX really is solid and capable with a bit of boost man and I can't wait to see what a driver like yourself can do with it in a chassis like Hyper. I get a little giddy inside when I think about the power and reliability my "cheap" stock junkyard v6 motor puts down compared to other platforms that EASILY cost 2 to 3 times as much.

In keeping with your comparison... we are pretty much a F430 GTC ;-)

Blackbird

ThePass

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ThePass

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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.

LukeG

Looks great and I'm dying to hear how it sounds.

ThePass

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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.







Always improving:




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.

Padlock

I can't imagine the looks on some of the peoples faces when your bringing a Frankenstein's track monster of a miata build to an AutoX like that

vehicular

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Out of curiosity, how does it sound?

LukeG

Hey Brother, how did you secure the carbon fiber V8R engine cover so it doesn't fly off at high speed?

ThePass

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Typical Rotrex, not significantly different - just a bit more air "wooshing" at WOT that's mostly coming from the intake, and then the most obvious thing is the loud rushing air sound any time you aren't on the throttle so decelerating or even at idle because the supercharger is always trying to make boost so the vent to atmosphere blowoff valve is what releases that pressure constantly.

ThePass

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Super fancy... 3M adhesive-backed high grip velcro on two flat spots on the intake manifold (and I think I remember shaving some plastic ribbing down to get a flatter surface). Also, a few small pieces of black "racer's tape" under the edges near the front, since the air wants to pick the cover up from the front.

ThePass

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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.



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).



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.



Intercooler #2 held pressure perfectly:



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.





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.