Preliminary Hellion Back Pressure results

[TurboX]

While these are not the results I was hoping for I have something to go on and might not need to get another Turbo after all. My car has a Hellion Kit with 38mm wastegate, PTE7675CEA .96AR and stock exhaust with flow thru axle backs. I made [email protected] psi and [email protected] psi but peak HP RPM fell by 1000RPM at higher boost level.

First, I bought a pressure gauge with a needle that will show max pressure. I then tapped a O2 bung fitting and put a 6 foot ¼" copper tube from rear 02 sensor placement to the gauge.

So far with 17.5 psi I have recorded a max pressure of 43 psi, this is reading of 2.45:1. I was expecting to find a 3:1 ratio, I might remove move my gauge to where I have wideband mounted(12" prior to Turbo Flange) and see if results change after the 2 banks merge into 1. Manuel(Lito) would also like to see how much it changes after I crank boost back up to 20-22 psi. After I am confident and can back up my results, I also intend on disconnecting the exhaust after the down pipe and seeing if there is any drop. By some stroke of luck, I might be able to make 3.5"-4" down pipe and then Y to a dual true 3 inch out the back.

Ive been reading Maximum Boost by Corky Bell but to be honest its way over my head, I need Cliff notes or Turbo for dummies. I did find it interesting to know that a single 3 inch pipe flows more than dual 2.5" pipes. My waste gate placement is adequate but I have a idea to make it a little better.

 

[Onelildude]

920ish!! What were you hoping for?

 

[TurboX]

To be honest, I could probably live with the 920 but I need more RPM than I am currently getting and want it done efficiently.

I have 3 goals, 200+ in Texas Mile, A Honest 1000RWHP on Mustang Dyno and 135 MPH Average Speed in Big Bend Open Road Race.

 

[toorbeenee]

I would say you would reach 1000 mark. would you be able to disconnect the exhaust system (after the cats)? you will see the turbo spooling faster.i would say you will gain more HP by removing the exhaust system. give it a shot

i had the same issue with 2013 GT500 mufflers. alot of back pressure

 

[LAStang1234]

Sub'd

 

[007GTCS]

Sub'd

 

[weather man]

OK, I'm punching way out of my weight class here! Could the A/R at that HP level be holding you back? For my Garrett, there is quite a bit of flow to be had with A/R's higher than .96.

 

[Kalatrax]

Any possibility of making a 4" y pipe and following that with 3" ota pipes? That would to give you plenty of flow.

 

[JPO8GT]

I agree with Toorbeenee
I do know the hellion single kits suffer from more back pressure than ideal i think i seen a post you had about larger down pipe i personally would drop the exhaust side first test it open exhaust first. Then check for improvement. That's the best place to start in my opinion.
And it's no extra cost in parts then go from there.
The turbo is good for your power level desired.

 

[Department Of Boost]

I agree with Toorbeenee
I do know the hellion single kits suffer from more back pressure than ideal i think i seen a post you had about larger down pipe i personally would drop the exhaust side first test it open exhaust first. Then check for improvement. That's the best place to start in my opinion.
And it's no extra cost in parts then go from there.
The turbo is good for your power level desired.

This^^^^^^^^^^^^^

 

[JPO8GT]

With the power your making your probably not running cats.
But if your running Cats at this power level and boost your asking for problems.
If so you really need to lose the cats.
If cats are installed removing them should alone improve things.

 

[CPRsm]

Yup, drop exhaust and make sure your back pressure isn't caused from post turbine pressure. I think you can go up 1 AR housing size from there if you want.

 

[TurboX]

Thanks all, Let me try and fill in some blanks. A bigger AR probably would not hurt, but this is 100% street car so I fear the bigger AR might hurt spool. I agree with everybody that next best step is going to be to drop exhaust, this will tell me if its the AR or stock type exhaust that is hurting. I am hoping that its actually a little of both and a simple modification from down pipe all the way back will fix my issues enough.

I say enough because if it doesn't I am going to have to pretty much rebuild the hot side and purchase a new turbo as well. Money isn't the biggest issue, its the fear that a bigger Turbo is going to increase lag beyond where I want it to be. I can be happy with 920-950rwhp but I need it to spin beyond 5500. I had 2.73 gears for the Mile and just went back to my 3.31s and the car is totally different animal. I finally got finished rearranging my garage and will raise the boost to 22 psi to see where back pressure goes to and then try and disconnect the exhaust and retest. I do need to make a small extension to point exhaust down, if I disconnect it now, I will blow torch my entire steering rack.



Thanks for all the replies

 

[toorbeenee]

Good luck to you, and wish you all the best

 

[Stinger]

Measure exhaust pressure in the downpipe to see if there's a restriction (or how bad the restriction is).

 

[GB10]

I may have missed, but what trans do you have? I agree that you should temporarily drop the exhaust to have the downpipe as short as possible to see how much of a change there is. I bet with a 4" downpipe you would notice a pretty drastic difference in the hp/tq curves on your graph.

I'm assuming you aren't floating valves either? What valve springs do you run or what is the seat pressure and spring rate?

 

[Flapjack]

Just got your PM. Sorry I didn't see this earlier.

While I've made good power with my car, I give most of the credit to Jim at THP and Lito. They helped me plan things out.

I would like to see your boost curve. I think that would give you a pretty good idea of what is going on at the turbo. I could see going up one AR size, but if the problem is your exhaust downstream of the turbo, that's not gonna help much.

I agree with everyone else in that you need to pull the exhaust off and see what it does. I know that going from a dual 2.5" setup to dual 3" exhaust made a helluva a difference in the way the car performed. I'm not sure how much it affected what RPM the turbo spooled at... but it did make the car feel much, much more smooth. I really haven't found a scientific explanation for why. It just felt like the engine didn't have to work as hard. I envisioned it mentally as everything on the exhaust side, starting at the exhaust valves, having less restriction and flowing smoother. All I know was that even if it didn't make any more power, it still 'felt' better, and was definitely worth the money.

 

[Bobby]

Subed.

 

[TurboX]

I have a TR6060 trans, I do not think I have a valve float problem but cannot rule it out with 100% certainly. My heads really have a lot of work done by JPC, while I do not know spring rates I can say Eric and Rich were fully aware that I had big plans for this motor.

I have been lazy and haven't had time to turn up boost to see what happens to back pressure. I almost think its a waste of time and I am going to just go ahead and disconnect after down pipe and hope for the best. If it drops to decent levels, then its not the exhaust Turbine and I can either purchase the dual 3 inch back or have something bigger fabricated.

If I can't get this under control, I will go with Jim or Bobby if he can get a sway bar

Bobby, thanks for that chat yesterday. I know we have had our differences but appreciate the time you made to speak to me.

 

[CPRsm]

You're getting up there in power lever for that turbo as is. A lot of headwork and cams could just be showing the limits sooner. That's normal. Might be time to step up to something in an S400 frame and get yourself a larger turbine