Allot have asked me what modifications I have made to the Hellion kit and why so here it comes.

1. Air Filters: They attached like a dryer hose and with enough boost, they actually suck themselves closed. The fix is a filter mounted directly to the turbo.
http://i861.photobucket.com/albums/ab175/PW-Racing/Hellion%20Kit/AirFilter.jpg
http://i861.photobucket.com/albums/ab175/PW-Racing/Hellion%20Kit/AirFilter2.jpg

2. The scavenge tank setup: Oil drains out of the turbo and into a tank. There is then an oil pump that pumps the oil from the tank back into the crankcase. This design is a nightmare and if the pump were to fail, so would the turbos. You also have to add a timer to keep the pump running for 30 seconds or so after the ignition shuts off in order to completely get all the oil out of the turbo so that it doesnt leak past the seals. My fix was to replace the Turbonetics turbos with Comp oilless turbos that do not use engine oil and are cooled via engine coolant.
http://i861.photobucket.com/albums/ab175/PW-Racing/Hellion%20Kit/OilTank.jpg
http://i861.photobucket.com/albums/ab175/PW-Racing/Hellion%20Kit/2011-05-19_13-40-09_170.jpg

3. The 2.5" piping: Might be ok for 500rwhp, but its way too small for high boost applications. Replace all this piping with true 3" piping instead. With my new turbos, we spec'd them to have a 3" V-Band outlet to make mating with the down-pipes easier.
http://i861.photobucket.com/albums/ab175/PW-Racing/Hellion%20Kit/2011-05-19_13-39-26_686.jpg
http://i861.photobucket.com/albums/ab175/PW-Racing/Hellion%20Kit/Piping.jpg

4. Wastegate Ventilation: With the 2.5" down-pipes already being too small, the last thing you want to do is add even more exhaust gas into that pipe via the wastegates especially at a 90* angle like this. With the 3" pipe, it may be OK, but I have chosen to vent the wastegates directly to atmosphere. If this is too noisey for you, you can route the vents into the exhaust, but do so at an angle so as not to disrupt the flow of the exhaust.
http://i861.photobucket.com/albums/ab175/PW-Racing/Hellion%20Kit/Wastegate2.jpg
http://i861.photobucket.com/albums/ab175/PW-Racing/Hellion%20Kit/Wastgate.jpg

5. Intercooler: The standard 3" thick intercooler doesnt cut it at high boost. You need a 4" intercooler. To make it fit, you simply notch the bumper support and your ready to go.
http://i861.photobucket.com/albums/ab175/PW-Racing/Hellion%20Kit/167216_10150373441860391_897475390_16714436_4484581_n.jpg


With all these changes, you will have yourself a 1000hp or more capable system. I hope to have finalized dyno results for you guys in the near future. As of right now, we have seen right at 850rwhp with the down-pipe, intercooler, wastegate modifications but this particular car is still using oil fed precision turbos.
http://i861.photobucket.com/albums/ab175/PW-Racing/Dyno/johnstwinturbo91octane.jpg
‪300c srt8 twin turbo dyno‬‏ - YouTube



My conclusion is that the Hellion kit is great up to about 650rwhp. If you wish to make more than that, I would consider having a local shop build it for you.


Some side notes:
The standard Hellion kit at 15psi had 40psi of back-pressure on a 392
The standard STS kit at 9psi had 42psi of back-pressure also on a 392

Both of these kits are probably great on stock engines with low-boost, but once you start cranking it up, thats when issues begin to pile up.

im impressed andy.. now if you can get those things into the engine compartment and away from the tranny !

Great write up Andy. Can't wait to see the car in person and run.

oh and somethings wrong with your intake manifold.. looks like it has a bunch of metal on it.. better look into that.. and maybe get a catchcan too.


great job

This manifold? :)
http://i861.photobucket.com/albums/ab175/PW-Racing/Andy%20Underwood/hemi008.jpg
http://i861.photobucket.com/albums/ab175/PW-Racing/Andy%20Underwood/028-1.jpg
http://i861.photobucket.com/albums/ab175/PW-Racing/Andy%20Underwood/027-1.jpg
http://i861.photobucket.com/albums/ab175/PW-Racing/Andy%20Underwood/012-1.jpg
http://i861.photobucket.com/albums/ab175/PW-Racing/Andy%20Underwood/005-8.jpg
http://i861.photobucket.com/albums/ab175/PW-Racing/Andy%20Underwood/004-9.jpg
http://i861.photobucket.com/albums/ab175/PW-Racing/Andy%20Underwood/001-11.jpg

that is one sexy manifold!

Very good info Andy. I do have one suggestion I found to be a great improvement on clamping your pipe. You need to see if they come in 3" size. These have two bolts - one clamps on the two fitted pipes and one end clamps just the smaller diameter pipe. These are worth buying one and seeing what they can do for your set-up.

Exhaust Clamp Torc Tite Preformed For Lap Joint 5" Stainless Steel, 20S-500, Heavy Duty Exhaust (http://www.ryderfleetproducts.com/ryder/af/ryder/core/content/product/srm/key/S48%2020S500/pn/Exhaust-Clamp-Torc-Tite-Preformed-For-Lap-Joint-5-Stainless-Steel/erm/productDetail.do;jsessionid=7B0CBA7504E3032E75499EDB5A5DFD29 )

Once the car comes back to me, all the connections will be replaced with these.

http://i861.photobucket.com/albums/ab175/PW-Racing/Andy%20Underwood/cat_1125_WEBL.jpg

Geez, the welds on that thing are sick! Who makes that?

Some side notes:
The standard Hellion kit at 15psi had 40psi of back-pressure on a 392
The standard STS kit at 9psi had 42psi of back-pressure also on a 392

Both of these kits are probably great on stock engines with low-boost, but once you start cranking it up, thats when issues begin to pile up.Wow, thats some serious backpressure. Great info Andy.

For anyone wondering, once you have twice the backpressure in your downpipe as you have boost in your intake, you are done making power efficiently. and you are really just heating up the air and causing the turbos to work overtime. On either of the examples above, I'd bet they'd pick up 30-40 rwhp (or more) from a better flowing exhaust without adding any more boost.

At that back-pressure we were only gaining about 10-13rwhp per psi of boost. Very inefficient.

So with the mods you suggest, how much backpressure are we talking about?

Not sure, havent measured it yet. Ideal is less than 2:1

OK I got you. I suppose we can measure it on mine after we get the tune from Johan.

I would say that the modifications worked flawlessly.

http://www.challengertalk.com/forums/f18/1087rwhp-1072rwtq-dyno-results-63961/

http://www.challengertalk.com/forums/f121/archtaans-twin-turbo-423-build-28029/

Hellion says their turbo system has no back pressure problem when using the stock 6.1 camshaft.I wonder if anyone has tested the stock cam up to 18-20 psi boost?It's nice to see the cheaper Turbonetics turbos outperforming the high dollar ones on other builds:thumbsup:

Im tired of hearing those comments. Ask them to provide dyno results of a stock 6.1 cam and 18-20psi.

Nag1, FYI, at the recommendation of Hellion, King Motorsports ran a stock profile cam on my 08 SRT8 300 W/Twin Precision BB 62MM Turbos, ended up pulling it, only after it stopped making power at a little over 700rwhp! Andy sent Brad King his own, in house, custom ground cam, and my build made over 1000 rwhp on race gas! sad to say, Hellion really didn't bring much to the table, it's really simple to throw out piss poor advice! it sure didn't cost them anything, however, it cost me plenty, to have the cam switched out!!!along with all the custom fabrication of the piping for my build! after a couple discussions w/ Hellion, they never once mentioned to me, that the piping that came along with the kit, would not build power! it seems that ,stock engine, low boost, your all set!!!!If your looking to build 1000, follow the information provided in this thread, and you have a winner!!

We are making the same improvements to my kit that we did to yours. I hope to be racing in Florida in Feb. Time will tell.