HP on stock ports
 

Hey guys, trying to find some information here. I have searched but cant find the information that I am looking for. How much HP the stock ports on a s4 turbo will support with good spool up (4000 rpm or less). I have a hybrid turbo on my car but was thinking of upgrading. The car runs very strong and I have no intentions of opening the motor. I made 241 at 6 psi with this turbo but it spools really late. I don't know if a good MBC would help on this.

In the dyno section on this the 2nd gen tech section, I believe Jrat got 400+ HP on a stock port S4 turbo motor.

Yep, I made 401.15, but my spool wasnt all that. 401 isnt the highest done on an S4 that I am aware of, but I havent seen any dyno sheets. Getting to 400 on a stock port motor with a turbo that full spools before 4k would be quite a challenge, but I have no reason to think it couldnt be done.

aside from stock with the twin scroll you will just have to live with later spool up, it is just the nature with these engines that they really only begin to produce power after 4k RPMs, if you can't live with that then get a V8 swap.

hey J-rat, I think I read your using a t61 now, I thought I read you use to run BNR stage 4 before, with the BNR when do you see full boost? I would love to have full boost at 4k but as long as it does not take to 5500 to 6k I would be ok with that. On the highest hp on stock ports I think i saw a video of a guy doing 500 on a dyno a long time ago but don't know much more about it.

Karack, I am using an s5 hybrid so no twin scroll on this turbo.

My car is running 6psi as of this moment, but it gets there at 5k wich I think is just too late for the small amount of boost that I am running. I am just trying to figure stuff out before I run higher boost.

Thanks for the replys guys, just trying to learn and stay in the correct path for my goals.

you got a screwed up hybrid then or it has some wastegate issues, it should not be spooling that late.

Yeah that is what I am thinking, I just looked at my dyno sheet, and at 5k is at 9psi and then it bleeds off very quick. I was using a T to vent out the air from the wg. I've been told to use a real mbc and it should help with the spooling. Also on the dyno sheet it says that we lifted at 7500 ish but inside the car the tach would be at 8k, they could not get a good signal from the wires and they just calculated the stuff. My dyno sheet is on the dyno section if you want to take a look. Thanks for the insights guys

does your hybrid have an adjustable wastegate arm? most builders install an adjustable rod but they are never adjusted to any specification, try turning up the tension on that rod and take it out for a spin and see how it works.

Slow spool on a Hybrid is a function of a hybrid itself. You are basically sticking a larger compressor wheel on the same size turbine. Its not a match made in heaven.

Yeah, I went to a t-61 with a .96 AR hotside. Its still a bit slow spooling for me but I went that route because once I port my motor, that will enable the engine to better match the turbo.


I think my BNR fully spooled in the 4000-4500 area, it wasnt THAT bad, especially for a hybrid. I also think that this turbo HAS made 400 wheel on a ported motor. I made 350 wheel on it with a non-ported motor.

full spool by 5k is a bit drastic though, if the exhaust is bypassing the wastegate then basically it could be a combination of waste diversion and normal boost. like i said, almost every hybrid i have seen has had the wastegate arm barely snug against the housing, the door would blow open even under light boosting.

sounds like you have a major pre turbo exhaust leak or big boost leak my friend.

Oh sure, I dont debate that. But Hybrids by function will be slower to spool then a matched turbo/compressor from say.. Garrett for example..

Are there any numbers for maxing a stock port N/A? Don't laugh turboed guys, just wondering.

well yes, they do spool slower by nature, bigger will take longer to spin up. 6psi is pretty weak for a hybrid, most turbos really come alive after 10psi.

^

Yeah, but his turbo should still be fully spooled by about 4k if he is using the S5 turbine/housing unless he is using some crazy 78mm compressor wheel on the cold side. That, matched with the fact that he is only boosting 6 psi (or 9psi according to the dyno) and the boost is bleeding off very quickly after 5k. That is definitely not the nature of a hybrid to drop boost like that after 5k. Hell, my S4 doesn't start to drop boost until about 7 - 7.5k and even then it is a barely noticeable drop on my boost gauge.

Granted he'll have slower boost response on a hybrid, but something must be wrong with his because it isn't acting like a hybrid besides for the extremely late boost onset.

Check that wastegate rod.

And J-rat also hit the nail on the head, a matched turbo from Garrett would be an excellent choice for you if you are looking for good spool and higher power numbers.

I can't wait to get my GT35R kit.....

Karack,
Does your hybrid have an adjustable wastegate arm?
It has the same rod that the factory one has.

Like I said, almost every hybrid I have seen has had the wastegate arm barely snug against the housing

That is an interesting observation, is there a reason why my cold side would be clocked to the side a little bit? Mine is.

Well yes, they do spool slower by nature; bigger will take longer to spin up. 6psi is pretty weak for a hybrid; most turbos really come alive after 10psi.

Agree, that is why I am trying to figure this out, with the help of you guys 



J-rat- I think my BNR fully spooled in the 4000-4500 area.

What was the boost level for full? 15 psi?


Snowball- sounds like you have a major pre turbo exhaust leak or big boost leak my friend.

I have been checking and I can’t find any leaks.


Boostinmaniac- Granted he'll have slower boost response on a hybrid, but something must be wrong with his because it isn't acting like a hybrid besides for the extremely late boost onset.

Check that wastegate rod.

I was told yesterday that bending the rod would help. Any opinions on this?


BTW thanks for all the help guys.