You're partially correct on this. At lower boost, you do get lesser thermo eff, however, the change of thermo compared to max eff is very small. When you get into the max flow condition, thermo eff will play a larger role. I think there're books and/or links out there that'll give you the formula on both volumetric eff and thermo eff.

I'll find it later for you.

 

Here's a link that will describe everything you wanted to know about turbo and how to choose turbo



http://www.gnttype.org/techarea/turbo/turboflow.html

 

thats a good article. This topic is often confusing for some people.
See the volume of air changes because of air temp. doesn't matter how big or small your turbo is. 15psi at the same air temp is the same amount of air no matter what turbo you got.

 

Great read thanks for the info!

 

I opened a can of worms with this one. I read the artical

Sooooo 15 psi @100 degrees willl net the same HP? no mater what turbo ?

Thanks everyone for your answers

Johny

And Steve you will have to show up at DE. to see if I bring Ms. Hottie

 

Hey Johny,
this is only true assuming that both turbos have similar eff and flow charterstics. Car A will not produce he same hp as Car B because of many other factors that I mentioned on my previoius reply. Also, the turbo has to size right so that it'll flow (maintain the boost at higher rpm), this is where you'll see a major difference in hp since hp is directly proportional to rpm. so as long as both turbos can maintain the same eff at max rpm, you won't see much hp difference assuming you're not changing the rest of the system.

I'm looking forward seeing you and the hottie.

 

I remember that link from way back. I'm certainly getting confused reading all this. The volume does change because of density which was what I was saying, but the turbo does effect this, 18lbs on 30R is less than 68% on a 42R over 78% the 42R will have more dense air from being heated less. Saying it would stay the same no matter what turbo you have would mean the intercooler was the equalizer, and that no matter what all air coming out of it is always 100* I don't agree with this. There used to be guys running around saying a cold air intake makes no difference on a turbo cuz it's going to get heated anyway once compressed, that's garbage hot air in, hotter air out. The hotter the air the thinner it is. Maybe I'm misunderstanding you here.

Edit**

Exactly!

 

you guys are missing the point i was trying to get at.

Im not saying you'll make the same hp with different turbo's.
remember turbo's directly effect the efficiency of the motor

Im saying that 15psi of air at the 100degrees is 15psi of air at 100degrees.
Its the same amount no matter what turbo. its still the same amount of air. it's still the same volume. and it's still the same airflow. or whatever else you wanna call it.

 

Uh, no?

We're still talking about turbos, right?

If we're talking homegeneous gas that's static, then you're correct.
But with turbos and boost, we're talking about taking a derivative or snap-shot of the airflow at any one point in time, and you just threw away the whole dimension of airflow out the window?


-Ted

 

I understand what your saying but it doesn't answer the question originally asked.

 

Actually he did answer the question as I have also on my previous replies. If you're looking at a snapshot at 5000rpm, it doesn't matter what turbo you're running, the hp will/should be the same as long as they're still within the same operating eff and flow. Now, if you're talking about at higher rpm where the smaller turbo will get out of the eff range and the larger turbo stays within its eff range, the answer is no, they won't produce the same hp because the smaller one will get saturated and out of eff range.

 

i think just like steve said we both answered his question with our early posts.

 

I understand this, and maybe I'm not seeing his question the same way. But If your asking a difference of 135hp between the two turbo's and asking why they are rated such. It seems your asking about two completely different sized turbos at their peak hp rating no?

I agree and it certainly shows how confusing it can get.

 

I have temp guage on both sides of the FMIC and I have an idea to cool down the turbo side, before the I/C. I hope to have it up this weekend if all goes well.

And I feel privledged to have all the experts replying

Johny