LukeG

Haha, good eyes! He snuck that in there without saying anything.

HarryB

I literally have not seen it there...nice!

ThePass

iTrader: (3)

Well someone finally noticed!

C38-92. The biggest one they make. Massive packaging challenge for everything involved. Have been working on this for a while.

mx5-kiwi

Sweet, power goals?

ThePass

iTrader: (3)

Haven't set any... seems a pointless exercise. Venturing into the unknown here. So few examples of boost of any form on this motor, and zero of them on E85, or with a Rotrex, or that are track-focused. There's a lot of question marks. Going to build things 'right' on paper and then go see what's what. Could say I want "X" number but that really means very little... ultimately it will make what it makes. Will be beginning with three pulley sizes to test. Very likely that the limitation will be fuel flow with E85 and direct injection, but there's only one way to find out.

griff

You are going to LOVE that engine on boost man! My only issue was the heat it added to the overall system. Last track day put temps into the 260s. Added another heat exchanger in the back of the car and hoping the next track day it runs at a reasonable temp when being pushed hard.

I'm on a DW255 with e85 and at the pretty mild 7-10psi on the track I have logged zero signs of fueling issues on the low or high pressure side.

Really excited to see what a capable driver like you will be able to compete against now!!! GO GET UM Ryan!!!

emilio700

iTrader: (3)

A few notes on my experience with Rotrex.
-The C38-94 doesn't tolerate abrupt speed changes when it's spinning really fast. Heavy mass of the compressor wheel tends to snap the shafts. So you want a soft cut rev limiter. You also don't want to plan a build or boost target around spinning it past recommended max rpm. The smaller ones can be beat on with impunity but as they get bigger they become a bit more fragile. Kept below its Max RPM and run with a soft cut they're pretty much indestructible though. If you add a sequential or dog box, keep this in mind.
- Rotrex like high compression, provided it's on corn. Even on e70 "E85" we ran 10 psi on a 10:1 BP to make 300whp at 22° ign timing. That's a lot. the base compression will help with low and mid range torque which our BP build had.
- I'm sure you would already do this but good idea to put a temp sensor in the cooler system. Rotrexes do not tolerate heat well. I forget the exact number but I think they want to be kept below 180 or so.
- Rotrexes put relatively little heat into the intake charge through the compressor housing, mainly just the heat from compression.

So so much fun to drive. You're going to love it.

ThePass

iTrader: (3)

That's very promising. I'm on a DW300.

Water cooled turbo in your case, right? That should add some heat to the cooling system that mine hopefully won't. Still, I'm bumping my oil cooler size up a notch. The radiator's job is made a bit tougher with the an intercooler and the rotrex cooler added to the nose.

ThePass

iTrader: (3)

Great note about the soft cut and sequential/dog box. Regarding impeller speeds, C38s max at 90,000 rpms. Have done the math and chosen three pulley sizes for testing that are all in the "safe" zone. The smallest of the three still spins the Rotrex at a safe margin below that 90k at the engine's 7200 rpm redline. There's no reason to run it for all it's worth and risk damage to the blower. The C38-92 flows some serious air and I expect I'll be getting all I want without needing to go for broke.

Rotrex specifies that the oil should not exceed 176° F at the inlet. I'll have a temperature sensor at the inlet and the Racepak programmed with a warning. (re-purposing the same temp sensor that previously measured power steering fluid temp, now that the blower has superseded the PS pump).

The LFX is 11.5:1. I consider the E85 mandatory for that reason. Given E85, hot damn that compression should make this killer.

There are a lot of reasons I chose this particular path. Right now I'm equal parts excited and apprehensive since there are some unknowns in the mix. It's a lot of work to do without knowing how it will all work in the end, or if it will even work well at all. But, I have faith in the recipe I've dreamed up. Ultimately the same reasons I chose the LFX in the beginning compared to some other ways to make similar power (big turbo or V8) are what are behind this choice. The strengths of the LFX and the Rotrex should complement each other very well.

emilio700

iTrader: (3)

With that much base compression I don't think torque will be an issue at all. It's a common peanut gallery criticism of the Rotrex but anyone who's driven one properly set up up know that torque is plentiful and instant. It's going to be a monster, but surprisingly easy to drive. If you end up with more cylinder pressure than you want on top end you can experiment with big blow-off valves on the manifold like we did. I don't think you're going to have that issue based on stock cams, how that engine flows and the airflow of the blower you chose. I agree it should be a perfect match.

HarryB

Exciting times! Do you know if you could swap DI injectors for higher flow ones, possibly straight from another GM engine? Big power VAG guys do that quite often, along with upgrading the high pressure fuel pump to up the pressure and flow rate.

griff

Correct, I have coolant lines running to/from the turbo but no oil lines.

LukeG

I know on the Overkill supercharger kit if you run E85 you have to upgrade the injectors fyi. But that seemed like the only change on using it with E85.

Edit: in the video he says they had to change the direct injection pump too.

ThePass

iTrader: (3)

I'd like to figure out the PNs for the HP pump and injectors they found work. I'd order them in a heartbeat just to have on hand.

LukeG

I'll bet money the high pressure fuel pump is from the ats-v LF4. Not sure about the injectors, but they may be as well.

This looks like the HP pump.
https://www.gmpartsdirect.com/oem-pa...-pump-12652441

Injectors:
https://www.gmpartsdirect.com/oem-pa...ector-12622473

And they used new rails for the injectors...
https://www.gmpartsdirect.com/oem-pa...-rail-12642953
https://www.gmpartsdirect.com/oem-pa...-rail-12662756

I'm not 100% certain this is what they used, but all of that is from the 2016 ATS-V and it might be worth a shot.

griff

Or here...
https://weaponxmotorsports.com/colle...f4-fuel-system

LukeG

This is the new hp pump they had in the video and one of the ats-v hp pumps on ebay.

LukeG

I didn't see an hp pump on their site, just the low side.

ThePass

iTrader: (3)

The LF4 pump certainly looks correct. I got the same PNs looking up a 2017 ATS-V:
HP Pump 12652441
Injector 12622473

With two spare LFXs sitting here (one good one, one paper weight) the easiest way to find out if they're compatible, at least physically, is going to be to just order them and test fit. I emailed Overkill just on the off chance that they're willing to share some info (and offering to pay for the info), but not holding my breath on that one.

I wish specs were available, we called our GM guy and he said he had nothing in the system with regards to max pressure of the pump or flow rate on the injectors. The tuner I'll be taking the car to had access to a 2016 ATS-V calibration and he says it has 126 lbs/hr plugged in for the injectors.

From that video above, I didn't get that the rails needed to be changed. It sounded like they swapped the injectors into the existing rails.

LukeG

Yeah, rewatched it and they did just swap out the injectors on the rail. Also, if you play it back slowly, when he flips over the new hp fuel pump you can see a "200" on the side for a split second around the 2:16 mark. That matches the long FF # on the ATSV pump that ends in 200 in the same spot.

That sounds about right on the injectors. I've read the oem LFX injectors are 109#.

This might save you some money... was digging around on the camaro5 forum and there is a build thread for a 650whp LFX camaro.
https://www.camaro5.com/forums/showthread.php?t=258249

In this post he says he is using the stock injectors and pushing almost 600whp and they were only 50-55% duty cycle.
https://www.camaro5.com/forums/showt...rs#post6385413

In a later post he says he is using the HP pump off of an LF3. This was before the ATS-V LF4 was out though.
https://www.camaro5.com/forums/showt...f3#post8095345