HP guesses in the new year.....

XR7 Dave

Registered User
So guys, how much HP do you think our split port swapped XR7 will make with a turbo? Motor is stock and we don't want to break it so we aren't going to go crazy and it will be running on pump gas. Bone stock the split port made 173rwhp 194rwtq. Where will we go from here? :D


Registered User
how much boost is planned? isn't 15lbs close to double whatever NA hp. there is more to it but a rough number
Last edited:

XR7 Dave

Registered User
Come on guys, lets be realistic. It's a stock 99 split port 3.8L. It makes 173rwhp NA. It's going to run on pump gas.

It has stock hyperutectic pistons, a stock cast crank, and powered metal rods. It has stock valve springs and stock cam. Yes, it is STOCK.

On a good day 1psi boost can net maybe 15rwhp. So 10psi could maybe net 150rwhp. To get from 173rwhp to 500rwhp will require 500-173=327/15=22psi. Not happening. How much boost is safe with pump gas on powdered metal rods? There is no way we can run 20psi. Like I said, not an option to blow it up.

If everything works well at 10psi we might make 325rwhp, but I've also seen 1psi netting only 10rwhp in which case 10psi would net 275rwhp. If we do make 325rwhp, that would be pretty impressive considering the most I've seen an SC make (even highly modified) at 10psi is around 295rwhp.

It will be interesting to see how the motor responds in terms of HP/psi.

I guess I should rephrase the question - how much power do you think it will make at 10psi, and how much do you expect it will make at 14psi? I think that's as high as we will go on a totally stock 100k mile motor.


Registered User
You said "We don't want to break it." We never want to break stuff..... You never truly implied or I didn't take you as being SUPER serious "Its not an option to break it."

You can be very sneakily on these things.

305 to the wheels then......:p

pro street rich

Registered User
just a guess here...

I would look for 398 hp with of course that funny gas I know you will be putting on there some place...lol.....Rich

XR7 Dave

Registered User
Well first dyno session complete. This was with wastegate spring only, no boost controller so we were stuck with a measly 7.8psi but nonetheless, 310rwhp.

So Travis guessed 315 and Anthony guessed 305. We split the difference on purpose! lol Not really, it made what it wanted to make. We have gained about 17hp/psi so far but most likely gains will drop off a bit as we go up. We'd like to run 12psi I think on this motor which will hopefully be reliable. If we are lucky, that would mean another 60 or so HP. The goal is 350rwhp, but so we'll either stop at 12psi or 350rwhp, whichever comes first.

Anyone want to guess where we end up?