Hello, I am looking to make 500 crank horsepower with a 2.5inch downpipe with a length of 22 inches. It is a 3 inch straight pipe after the downpipe. 2.5 inch it the biggest I can use due to clearance issues. 4.0L jeep engine. Garret 60-1 .70 comp .63ar exhaust.

I know that 2.5 is not ideal but it is the biggest I can use while retaining 4x4. Is 500 crank horsepower possible? I have enough fuel for roughly 600hp and a big intercooler on 93. I am currently running 14psi guesstimated 400 chp. Thank you.

 

I don't want to say it's impossible, but it will come with some very difficult hurdles to leap. Any chance you could split it into two 2.5" and go on either side of the obstacle?

 

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Thank you for the response. My whole engine bay is the obstacle lol. I am very space limited and 2.5 barely clears the firewall engine block and drive shaft. My waste gate is dumping to the atmosphere which should help some. I have a 4 port boost solenoid so I can run more boost but I know that’s not always best. What is an acceptable boost to drive psi ratio. I may install a drive pressure guage. Thanks

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What's on the other side of the firewall? Can adjust it some? Hammer? Pry bar?

 

I think you're on the right track. The open dump will help a lot. For drive ratio, I would start to worry once I saw 3:1. The ratio isn't an absolute, but it's a good measurement to take. That ratio will determine octane and timing limits.

Got pics of the install?

 

how about 3” oval tubing

 

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Thanks for the responses. I thought about 3 inch oval but I already made the current setup and I don’t know if it will fit. I will just keep raising the boost and tuning till drive pressure or egts begin to rapidly climb. I think I can get close to my targeted 500chp goal. Turbo is under the intake (fun and easy to work on...) Thanks

 

I already did the “adjustment” the drive shaft is my biggest obstacle.

 

500hp @4500rpms will require 32psi/3.18 pr. This will require a 2.26 expansion ratio through the turbine. This comes out to a corrected flow of 33lbs/min in the exhaust manifold @1500°egt. I looked at a gtx35 for its turbine flow chart since it is pretty close to same size, it is waaaay over what your .63 a/r housing will do, 52% too small actually. A .83 a/r housing will leave you with only 20% which will be alot easier on drive pressure and won't require so much wastegating.

Also, 3.18pr is over what the 60-1 compressor map has, but experience says it will do it, those older turbos kept to modest shaft speeds.

 

Someone with some math, I like it. So what you are saying is 500chp is not possible? What is about the max my setup can flow? Thanks for the help.

 

500hp is definitely possible, just not with that small .63 housing. Need to bump up to .83 or 1.0 is even better if the spool up isn't too bad. The compressor will be pushed, but it should do it.

 

Cool build man.

Bigger housing isn't going to help on a jeep 4.0.
They are redlining at 4k rpm. It's a glorified tractor engine. That .63 housing is probably making it a torque monster though. Which is what actually gets you moving.

Are sure you need 32 psi to make 500hp..? That doesn't seem right. If the engine makes 180hp stock, 14psi would double its output.. So seems like 18 to 20psi would put him at the 500hp range.

Maybe split the exhaust into two 2" pipes ir use a round to oval 3" or bigger transition.

If emissions/smog aren't an issue. You could make a dump valve or wastegate that opens the exhaust up after whatever psi you want underneath to relieve backpressure.

If the drive shaft is the biggest hurdle, why not shoot under the oil pan and bring the exhaust down the passenger side? This is probably why the banks sidewinder turbo system is mounted on the passenger side of the engine bay, for more clearance.

I'm in a similar boat, only place my turbo will fit is the side with the driveshaft in my CJ7

 

A .63a/r housing is choked after ~22lbs/min corrected flow. He'll be at 33lbs/min, which means his wastegate will have to bleed ~50% of the exhaust. This also raises drive pressure since a wastegate requires a pressure and temp drop, which isn't 100% efficient. Just swap to a .83 housing and it'll help the entire situation.

If you want double the power, the air density has to be doubled, not pressure. 15psi is a 2:1pr, and assuming a 74% efficient compressor going through a 70% efficient intercooler... we end up with a 1.84 density ratio. 180hp x 1.84= 331hp. So yes, I do think 32psi would get him to 500hp. If he wants it before 4500rpms, boost will need to be even higher.

If we run the 3.18pr at 68% efficiency and 70% efficient intercooler again, we end up with a density ratio of 2.75. 2.75 x 180hp =495. This will be reduced though since the small turbine housing will be causing higher drive pressure than boost, reducing the engines ve. A 1.06 housing flows exactly 33lbs/ min, so he would be at either 1:1 or possibly more boost than drive, but spool up would be laggy.

 

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Thank you for the responses. I like the characteristics of the ball bearing .63. So I really don’t want to change my setup too much if it is not needed . I can build 12 psi by 2500rpm and by 3000rpm I can hold 15psi to 5000 rpm.

My motor is 9.5:1 compression with forged parts and ported head so it probably makes around 210 horsepower by 4700 naturally aspirated.
Looking at my tune at 4500rpm/15 psi my computer opens (2) 1600cc (152) lbhr injectors to 50% duty cycle. These 2 injectors can supply 500 horsepower at 100% duty cycle (according to FuelTech’s calculator). 50% of 500 horsepower is 250 horsepower. My afr is 11:1 so this calculation of air to fuel should be fairly accurate but we can estimate that with the richer afr is only enough for 210 horsepower.
My factory ecu controls the (6) 21lbhr stock injectors to what it thinks is 0psi at any given rpm when in boost. This is well enough for 210 horsepower.
Add the 210 horsepower plus the 210 horsepower and it gives 420 horsepower at 15psi 4700rpm. My combination makes about 14hp per lb of boost (210/14.7)
I am fairly certain that my combination will not need 32psi to achieve 500 horsepower. Garret lists a t3/60-1 as efficient up to 550hp. I use the formulas in the posted picture as well and it seems pretty accurate within reason (horsepower doubles at 14.7 psi if things are tuned correctly).
Please correct me if my thinking is entirely wrong. Thanks again for the responses.

 

That would of been useful information to know lol. So your engines ve is 96%, really good. Now we're getting somewhere... your now at 24.6psi, might as well say 25psi, so 2.7 pressure ratio. Density ratio coming out of the intercooler will be 2.36. 210hp x 2.36= 495.6hp. This is right at the upper right edge of the turbos compressor map. Downside to this is the exhaust isn't as dense, so corrected flow goes up to 40lbs/min in the exhaust manifold, more wastegating required, dumping to atmosphere will help.

Double the pressure is not double the density, which is what you need to make power. At 15psi your only getting ~1.84x's the power. So 210hp x 1.84= 386hp. In a perfect world, or with really good water to air intercooling, you could get 2.0 density ratio with 15psi.

You can't rely on turbo manufacturers published hp numbers. Pressure ratio changes with the displacement of the engine, so although they advertise "efficient" 550hp, your engine may require a pr that is above that particular spot in the compressor map, which it is.

If you put 55lbs/min @2.7pr on the gtx3576r, which is the modern version of your turbo, it does it at 74% efficiency instead of your 70%. This puts you at 502hp on the exact same setup. If it was me, I'd run the 1.06 divided housing with a flow diverter valve, that would cut the housings a/r in half for spooling, so .53a/r, then it could open to full housing for lowest drive pressure and wastegate. But that's just me, and I realize it'd be expensive vs what you already have. Just giving ya something to chew on....

 

I understand what you are saying. Pressure is not density. The diverter valve thing would be very cool and if I was loaded I would definitely try it. Could you please explain where you are getting your numbers for your density and flow calculations? Is it entirely from a compressor map? This stuff is cool, I’m taking calc in high school and this would be nice to be able to do. I should have included my fuel consumption before, sorry. Thank you.

 

Diverter valves aren't very expensive. Gtx3576r's you can pick up used at a pretty decent price if you watch for a deal, I've seen them for $1200. Or here's a 1.0 divided housing for your turbo... https://www.atpturbo.com/mm5/mercha...&Product_Code=ATP-HSG-016&Category_Code=GTHTS

Man, it's taken me awhile to get all the equations, especially the turbine side ones. And there's a difference between doing the calculations, and understanding what the numbers are telling you. If your taking calculus your way ahead of me, I barely passed my math classes.

 

Again, another post waiting for approval.

But first you have to figure out how much air you need for the hp you want to make, then how much boost it'll take to get that in the engine. You already have the turbo, so it was just a matter of seeing where 55lbs/min @2.7pr fell on the map. From there you can calculate the temp rise out of the compressor, temp drop out of the intercooler, and that gives you your density.