Hellephant exhaust design questions

[GARY C]

There are several documented 7 and 8 second 1/4 mile cars running stock bottom end LS engines in the neighborhood of 30 psi of boost.

My thought is, OEM stress test x Drunk Red Neck stress test divided by actual rods thrown = OP made safe decision providing he doesn't factor in and Drunk Red Neck engineering.

7 seconds is nowhere near the kind of stress testing that gets done at the OEM level.

When you buy a "crate" with PCM package, you're not just buying the engine, you're buying the engine package and calibration. THAT is worth its weight in gold.

Relevant to the thread, I've seen <1psi backpressure on a single 3" exhaust system with two mufflers inline, on a similar powered supercharged 6l. No matter what you do, you'll be fine.

I understand that I was just pointing out that when you have stock 4.8 and 5.3 engines taking that kind of abuse on a weekly bases and living an entire season and more it is a testament to the strength of todays factory engines.

[Olds455]

You're actually planning on spending what will likely be $35k for 1000hp gen 3 hemi? Serious question here. Are you on crack? Guys build boosted 1000hp LS engines for about 1/17 of that price lol. I just can't see spending $35k just to be able to say it's a hemi. That's the only thing you get with that 35k, imo, that you can't get anywhere else for way less.

I'm mostly interested in reliability, warranty, and of course a drop-in replacement for the current motor. I have friends who have made over 1,000whp on turbocharged LS3s, and all have lifespans best measured in quarter mile passes. Meanwhile the Hellephant is said to have been in durability testing for the last few months on premium pump gas. I realize I could build and sort my own motor for a lot less (though not anywhere near $2,000), but time is money. I'd rather pay more for a proven solution that won't leave me stranded on the side of a road or toss a rod out the side of the block.

Larry, hydraulic roller, and 1,000 crank hp is what it's rated at. I'll email you my PipeMax file. It's possible I screwed something up as I haven't used the software in ages. Great to hear a 3.5" exhaust will be enough, thanks! What exactly was the bug?

Harry, the runner volume conclusion is interesting. I'm building a NC Miata to go endurance racing in WRL and ChampCar. We're running shorty 1.8 headers because that's what everyone makes the best power with. In fact I think we have a dynojet record for an unopened NC longblock by at least 5 hp (it made 171whp). The diameter is a lot bigger than PipeMax recommends, and the runners are obviously shorter, but it works. I was debating trying a custom tuned-length header but you've convinced me not to. With this in mind I'll try to contact Mopar and see what they've tested.

Thank you for the well thought out response. I just want to say sorry for being so abrasive. I realize it could've been toned down a bit so I just wanted to apologize for that.

[Grant]

Larry, I emailed you my PipeMax file.

Is there something dimensionally different about this engine that makes you think it will be less likely to throw a rod?

I'm not sure why you mean by dimensionally, but the prime advantage of the Gen 3 hemi over the LS is the presence of oil drain back holes on the exhaust side of the heads. The valve covers should be a lot less prone to fill up with oil during cornering, which starves the sump. All the LS motors found in the C6 Corvettes have big problems with oil starvation, though it's not likely a Magnum is going to run into this issue as commonly as a sports car would.

The hemis also have oil-fed, shaft-mounted rockers. The rockers on LS engines are known to spit out their bearings. Hemis also have piston oil squirters, which I'm guessing are important when making bigger power on pump gas. They also have 6 thou more bore spacing than LSes, for whatever that is worth. I'm not sure if the Hellephant will use Chrysler's hemi VVT system.

I don't know what other changes Mopar may be making to the Hellephant to reliably support 1,000 bhp. I simply don't have the capability to build an LS or hemi on my own to the level Mopar is capable of. I don't have an engine dyno which can vary intake and coolant temperatures to tune for all conditions. I don't have access to a Spintron. I certainly don't have the necessary experience, nor do I know anyone who builds powerful engines at the level of dependability I'm looking for.

[LoganD]

This "Hellephant" is just the current hellcat redeye engine with a bit more displacement. The redeye is rated at 797 hp SAE, and that means it makes 797 hp with a full air induction system, full exhaust, full accessories, and hot coolant. All they did with this engine is take that stuff off, make a cold pull, and be a bit more aggressive with the tune up. The displacement took care of the rest. The cylinder pressure in this engine isn't any greater than a regular hellcat redeye.

A good exhaust will help this engine, do not confuse "boost" with cylinder pressure. That being said, I have never seen reduced exhaust back pressure affect boost significantly on a supercharged engine (within reason). Obviously exhaust back pressure can have a big effect on turbocharger boost pressure, but a supercharger is in no way connected to the exhaust system and this engine does not have significant valve overlap. You want good overall mass flow, boost should be a result of that not the goal. From a reliability standpoint, having low exhaust back pressure is very very good for the life of the exhaust valves and seats as it will reduce EGTs.

[Newold1]

Grant it seems somewhat obvious by your posts that you are a person of strong financial means to be planning what you are talking about here and your other concurrent projects just seems to support that. You will need that for this proposed project!

I do however have a few questions and comments about your plans for your car and engine.

First you mention warranty? I am suspect that Mopar is going to sell a 1000hp supercharged engine of any kind and provide any meaningful warranty on how it survives whatever use? I sure would want to study and question any warranty as to how it will apply when it's race use creates issues?

I have been involved in a few road race type engines and vehicles over the years and I have never been exposed to or seen a car that effectively doubled or so it's horsepower and managed to still to run on a closed course where that huge increase in power level would translate to good performance on the track. I suspect if this is a current street driven vehicle that it's going to have to undergo a lot of major mods in both drivetrain , suspension ,cooling, set-up etc. to even begin to handle that major increase in power & TORQUE in your Magnum. Just oil heating and cooling alone under power on a track environment will most likely call for dry sump oiling and I don't know how the Hellephant engine is equipped or sold in crate form? Just thinking about those power and torque levels on the cars factory transmission and rear axles alone is a big issue.

This is a cool sounding project and as is sounds like a exercise in extremes and and such it will be interesting to see where your resources can take it. I hope you achieve your great results but the road ahead will need them as the time and effort here to achieve a good result is a huge one I have seen fairly major race teams undertake and really struggle.

You're heaping a lot on your plate and I hope you will keep of informed how this project proceeds. Best of Luck!

[Grant]

Newold1, I completely agree: doubling stock horsepower on an open track car is almost always a dumb idea. That's really more of a time attack move. Though in my case the driveline will be suitable for modified Hellcat power in a much heavier car, so it won't be quite as ridiculous as it sounds. Even still tracking a Hellcat is dumb. The costs per hour of run time would be astronomical. These cars are good on the street, but are simply too heavy to be serious track machines. That's not my goal anyway.

Lapping a car with this sort of absurd power / grip ratio is just something I want the experience of doing every now and then, probably one hot lap at a time with a cooldown in-between. I won't make a habit of it, and if for some crazy reason I do I'll run a larger supercharger pulley to lower the boost on track.

When I have the car out at my local track (usually because I'm driving something which actually belongs there) I will sometimes do some laps at its current ~540whp level. It does pretty well for what it is and it's fun to pass people in a giant wagon daily driver.

As for the warranty, I re-googled that and saw FCA thought it would be unlikely to be warrantied by Mopar, but a final decision hadn't been made. Damn.

[MadBill]

Update: WardsAuto reported today that FCA sold out their 100 unit stock of Hellephants in 48 hours.

[steve316]

48 hrs. that will make the next ones higher