Pettit twins max hp?
 

I'm considering upping the max boost. Have Pettit upgraded twins with full intake and exhaust. No dp, no cat converter, no air pump, big intercooler, hard pipes from cold air intake thru turbos to intake manifold. RotorSports stage II engine. Running 14 psi and get 395 rwhp. Did a dyno run ten years ago when I first got the Petit turbos and ran 20 psi briefly with stock injectors maxxed out. Can't find the dyno sheet, but think it was about 425 hp. Does anyone have the Pettit turbos and what hp are you getting? Max boost? How long running at that psi w/o engine failure? Before I change the injectors and fuel pump I want to see what add'l hp gains I can expect. Any help appreciated.

No replies yet. Was hoping someone out there is running 20 psi with upgraded injectors and fuel pump and gets 500 plus rwhp. Just hoping.....................

What I have noticed on stock and modified stock twin turbos.

People have made ~400hp on stock twins.

People have made just over 400hp on modified stock twins with everything thrown at them.

Someone has made 475 with parallel modified stock twins and external wastegate.

I propose that you can do whatever you like to the motor or the stock twins compressor and exhaust wheel and not gain much peak system flow because the restriction is in the primary to secondary turbo's exhaust outlets.

Just look at them. They dead head (point right at each other) and then make a very tight 115 degree turn to meet a downpipe that must make a very tight 90 degree turn.

I propose this exhaust merge/outlet is the real choke point limiting flow to around the 400rwhp level and the reason why adding an external wastegate for more exhaust flow makes such a big difference on the stock twins.

So... yeah, I predict you can push the Pettit twins to around 400rwhp.

Did a dyno run ten years ago when I first got the Petit turbos and ran 20 psi briefly with stock injectors maxxed out. Can't find the dyno sheet, but think it was about 425 hp.

Stock injectors should max ~305rwhp (that is 85% duty cycle).

You can upgrade the pump and push them to 100% duty cycle and get ~360rwhp.
You can jack up the fuel pressure and get ~375rwhp out of them- but these are bad hacks.

Perhaps you are running 4x secondary injectors? That would get you ~370rwhp (85% duty cycle) or up to ~435rwhp at 100% duty cycle/hacks.

Anyways, sounds like you found a "happy" dyno. Go back to that dyno and tuner or you might face disappointment with your new numbers.

I'm like Ron and it's been almost a decade, but I easily got 300hp outta my Pettit twins with stock injectors (and a street port). The printout sheet is long gone and I have absolutely no proof to back me up.

It did happen though. It was right after I got my rats nest done (Rotorsport...best in the Bay), Steve Kan was in town and and I wanted to see if everything was hooked up properly. It was.
Mustang Dyno, right around 18 psi, 300 and climbing. I got scared and shut 'er down.

Natey- I'm like Ron and it's been almost a decade, but I easily got 300hp outta my Pettit twins with stock injectors (and a street port). The printout sheet is long gone and I have absolutely no proof to back me up.

It did happen though. It was right after I got my rats nest done (Rotorsport...best in the Bay), Steve Kan was in town and and I wanted to see if everything was hooked up properly. It was.
Mustang Dyno, right around 18 psi, 300 and climbing. I got scared and shut 'er down.

Sounds fairly typical- no proof needed.

ronarndt- Running 14 psi and get 395 rwhp. Did a dyno run ten years ago when I first got the Petit turbos and ran 20 psi briefly with stock injectors maxxed out. Can't find the dyno sheet, but think it was about 425 hp.

Does not sound typical- proof or more information necessary for me to accept.

See the 100+ hp discrepancy between posts?

max hp
 

Thanks for the info. Hate to admit that one reason for asking how much addl hp is out there with the twins is my decision whether to squeeze out another 10-20 hp from the FD or go with the bargain priced Vette C6 z06 that are showing up on the used car market, now that the new C7 model is out. Would love to get one of the new z06, but you cannot find a stripped down version and all of the loaded ones are going for over $100K . However......you can get a low mileage 2008-2010 for $35-45K. Starts with 505 hp and Edelbrock makes a bolt-on supercharger that gives another 100 hp or more. With tinkering with the cpu and the boost, 700 hp is not that tough. Amazing what 7 liters of displacement can do. Will probably keep the FD, since there is no way I can sell it and get even a fraction of what is invested in it. Friggin money pit, but like a woman you put up with cause occasionally she curls your toes.

425whp on the twins is pretty possible these days with sufficient cooling and fuel support. I made just over 325whp on stock injectors with increased fuel pressure. Decided to swap out for square 850's to lower my duty cycles and probably would make 350whp but I cannot say for sure.

Honestly, I rebuild pre and post 99 twins in my spare time as I haven't had a rebuilt one fail on me as yet. My daily fd that see's rain,shine, snow, etc plus harsh track events still hasn't leaked after I rebuilt em.I would say if stocks twins can make 400whp, pettit's might make 420 or a bit higher. I haven't seen them in person before but I have played with BNR's stage 2 and have seen amazing results imo but then again, it is all in who is tuning it and how conditions of your engine and etc... You did say you dynoed that ten years ago, so I wonder if it could do so again without a rebuilt or light fresh up :)