Question about HP ratings of turbos, rainy day ramble

[Pronto]

It's kind of crappy day out and I was reading some posts on the new billet turbos and such. Since I have first got involved with the TBs I never really understood how a turbo manufacture comes up with a hp rating on the turbo. It pretty easy to see that just because a turbo is rated at 600hp that not every car with that turbo makes "600" hp. Just check the signitures. Is that number a best case senerio with perfect tune? How do they figure in things like ported heads or different cams? Is it just by the total volume of air moved compared to totally stock TB using some formula? At one time I had a book on turbos and it explained about the maps. Unfortunately I've lost that book. Is there any good sites that explain turbo maps for people that are not engineers? How do you get a map of the new TB turbos out there? With all the claims out by vendors on this turbo or that turbo's capabilites it's next to impossible for me to figure out what works with what mods. Old school, ball bearings, water cooled, billet; I wish there was one complete list that would get updated from stock on up of all the turbos and their options so I could get a real idea how one compares to another and what mods would be needed to support it. Sorry for the ramble...

 

[street6]

a little puzzled myself, however some of the older turbo literature or spec charts provides a cfm rating as well as a horsepower rating which I would think is obtained at an acceptable boost level for a given turbo before the turbo is just forcing hot air due to efficiency reasons or creating unacceptable back pressure.

 

[bison]

They come up with them from customer feedback. Some seem like they may be hypothetical since they give hp ratings before the turbos are even available main stream. Based on the #'s Precision gives it looks like only about 2% ever hit that number or exceed it. Its usually heads up racers and the limitation is usually the turbo. Most cant even come within 15% of those numbers.

 

[bison]

a little puzzled myself, however some of the older turbo literature or spec charts provides a cfm rating as well as a horsepower rating which I would think is obtained at an acceptable boost level for a given turbo before the turbo is just forcing hot air due to efficiency reasons or creating unacceptable back pressure.

To hit the numbers Precision gives they will all have unacceptable back pressure with 3 bolt housings imo

 

[Pronto]

So your saying basicly those hp numbers are theoretical and most people won't get near them?

 

[SS_Sean]

They are bs and don't mean anything. It's about like saying a certain intake manifold will add X power, and a certain cold air intake will make X amount of power...

 

[GNBRETT]

Well, if a given turbo has made say 950 hp. after running a given mph in the 1/4 and the manufactor measures how much air it flows I would think they would have a guage as to what flow numbers will equate to hp numbers based on track runs. So if a new design is flowing more air then the previous one then it should make more horsepower respectively.

I don't think the numbers are BS but to reach them in our cars I think one has run extremely high boost which would grenade most TR motors.

Look how fast some of the TSM guys have gone. Based on the power they are making I would say they exceed what the manufactor has reported and I would assume those manufactor numbers come from a 4 bolt design and the TSM guys all run 3 bolts.

So I think the hp numbers are real and attainable but only by a small fraction of racers using them who have deep pockets experimenting with what works and what doesn't to reach that much hp.

 

[sugarandopium]

How do you get a map of the new TB turbos out there? With all the claims out by vendors on this turbo or that turbo's capabilites it's next to impossible for me to figure out what works with what mods. Old school, ball bearings, water cooled, billet; I wish there was one complete list that would get updated from stock on up of all the turbos and their options so I could get a real idea how one compares to another and what mods would be needed to support it. Sorry for the ramble...

Yeah, there is a great list/chart of the TE/TA with what works with what stalls and mods.
Would be great to have something like this for the all the new ones.
Trying to figure out what works with what and make a decision for my next turbo, but there is so little info on them all.


If someone can get me all the info on the stall/fuel/mod needs of all the billet and dbb turbos, I would be happy to make a spreadsheet on them for everyone's reference.

 

[bison]

So your saying basicly those hp numbers are theoretical and most people won't get near them?

Not theoretical. They were based on customer feedback. Most people on this board havent got near them. I can think of about 5 that have hit those numbers and they are/were heads up racers. So big $ and time in R&D on their part.

 

[49-blues]

I always understood that the HP rating turbos made were made at 30 psi boost, so if you re running at 24 psi-that would mean 80% of the horsepower rating. so a turbo rated at 900 hp running at 24 psi boost would equal 720 hp. right or wrong?

 

[OneQuikSix]

I always understood that the HP rating turbos made were made at 30 psi boost, so if you re running at 24 psi-that would mean 80% of the horsepower rating. so a turbo rated at 900 hp running at 24 psi boost would equal 720 hp. right or wrong?

I believe that statement is incorrect. Boost pressure is more of a relative thing. In other words, your car and my car running the same amount of boost with the same turbos, at the same AFR, may make different amounts of power. It all depends on the rest of the combination. A car with upgraded heads/cam/etc... will require less boost than another car with the same turbo running an unopened motor. Someone jump in here if I'm wrong

 

[bison]

I always understood that the HP rating turbos made were made at 30 psi boost, so if you re running at 24 psi-that would mean 80% of the horsepower rating. so a turbo rated at 900 hp running at 24 psi boost would equal 720 hp. right or wrong?

I dont no where you got this info. It doesnt make much sense since the engine rpm has a lot to do with hp. If you read the sigs on here you will see that almost all that you read except the heads up racers arent even coming close to 80% at 24psi. Most wouldnt come close at over 30psi.

 

[87natl]

I always figured it was just a guidline as well. I dyno-ed well over 600 HP on a turbo rated to 575. So...what does it mean??

Seems to me the best way for a manufacturer to represent the abilities of different units would be to run them on an identical motor with the same hard parts for all tests, and only making changes in the fueling to keep up. Run them all and rate them all at the same A/F on that same motor, and change nothing else. At least you would have a reference point as to what turbo was making more or less power on a similar setup. And of course it would probably have to be tests run on an engine dyno to elimate driveline changes especially stall changes.

Think somebody is going to do all of that????

 

[bison]

I always figured it was just a guidline as well. I dyno-ed well over 600 HP on a turbo rated to 575. So...what does it mean??

What is your quarter mph and race weight?

 

[87natl]

Didn't get to run it with that combo. I went ahead and upgraded since then. Had that combo together for only about a month after I did my stroker build. Just pulled one of my old sheets out.....dyno-d 627.9 hp at only 21.3 psi on a superflo dyno....with a TE-60.

 

[87GN_70GS]

The maximum ratings come from the compressor flow maps. They tell you the maximum corrected air flow that a particular compressor is capable of, and can't be exceeeded. Hp is rouhgly flow in lb/min multiplied by 10. Obviously, you can arrive at a lower power rating just by lowering the pressure ratio (boost). If you really want to nail it down, you overlay the turbine map on top of the compressor map and their intersection(s) will determine operating point(s).