Jesuscookies

iTrader: (1)

Maybe I did not phrase my question correctly.

I am talking theortically. If I have a NA rotary engine. I then put an average street port, and all of the necessary supporting mods to keep it as free flowing as possible. I end up with an engine that on average will put about 190 to the rear wheels. So, a street ported NA rotary is good for about 190 to the wheels.

If I then turbo charge this very same engine, and feed it 14.7 pounds of boost, or 1Bar. I should be limited to exactly double the horsepower under ideal condtions, or 380RWHP. Follow me?

I want to know how any turbo can flow higher than this at 1 bar of boost?

If the R85 makes 469RWHP at 1Bar. doesn't this mean that the engine had initially had, at 100% effeciency, 235RWHP?

Sorry if this question sounds retarded. I am just having trouble understanding the concept.....and I am retarded

CCarlisi

Output is determined by the amount of air the motor can combust. To determine the amount of air being processed by the motor with each combustion cycle you must look at two factors: (1) the amount of air going into the motor and (2) the amount of combusted air/fuel exiting the motor.

Two factors go into (1): volume of the chamber and the density of the air in the chamber. The density of the air in the chamber is effected by temperature and pressure(boost).

Next you must consider how much air is exiting the motor with each combustion cycle. When the backpressure is reduced the rotor chamber empties more completely. This in turn increases the volume of air the rotor can process on the next intake stroke.

Therefore, two engines running the same boost but with different exhaust systems will process a different amount of air with each combustion cycle. I believe this is why you can go from 190 to 469 at around 1 bar. It's also possible the temperature of the turbo car's air is lower, however I think that is unlikely assuming the NA motor has a cold air box.

POM HB

When will we know the brand of the R85's turbo? As Max's concern, I'd love to know the cost for rebuilt.

POM HB

allrotor93

iTrader: (126)

it will be cheap and you probably will not know the tubo unless you buy it

BoostedRex

I see what you are saying Jesuscookies. But I believe that the size of the compressor wheel makes a difference with that. CFM is different at the same boost level depending on CFM through the compressor. That's the only logic that I can think of to answer your question. But then again I'm far from the smartest turbo guy in the world. Just my .02

Zach

BoostedRex

I see what you are saying Jesuscookies. But I believe that the size of the compressor wheel makes a difference with that. CFM is different at the same boost level depending on CFM through the compressor. That's the only logic that I can think of to answer your question. But then again I'm far from the smartest turbo guy in the world. Just my .02

Zach

DCrosby

CFM and PSI, are like Voltage and Amperage... and like water hoses / pipes...

CFM = Amperage = Size of the Pipe
PSI = Voltage = Pressure In the Pipe

So just cause you have Lots of Pressure In The pipe, doesn't mean it's a big pipe... while a Big Pipe needs less pressure to get the same CU" (Cubic Inches) of air into the combustion chamber...

maxcooper

Jesuscookies is talking about engine power scaling somewhat linearly with absolute intake pressure (assuming turbo efficiency is good, etc.). At 0 pisa, the engine makes 0 RWHP, at 14.7 psia (NA, zero boost) the engine makes X RWHP, and at 29.4 psia (14.7 psi of boost) the engine should make around 2*X RWHP.

I understand what you are saying, but I don't have a good answer about how the engine could make 460 RWHP at 15 psi boost other than an assumption that perhaps it would make 230 RWHP if it was NA. Perhaps the IC does such a good job at cooling that the intake air is cooler than you would have on an NA engine, perhaps the ports work better under more pressure, people might be more careful with A/F tuning on the turbo motors, the engine revs out quite high where it would make more power if the flow is still good, etc. Also, I have never been able to dyno my car with an absolutely constant boost pressure -- it always seems to drift a bit as the engine revs out. And sometimes the boost gauges aren't very accurate.

However, this certainly wouldn't be the first dyno I have seen where the car seems to make more power than you would expect by extrapolating the absolute intake pressure of a 190 RWHP NA setup. My car made 367 RWHP at 12 psi or so at the power peak, which beats the extrapolation expectations (NA would be 367 * 14.7 / (14.7 + 12) = 202 RWHP by interpolation). I didn't watch the boost gauge during the dyno, but they said 0.7-0.8 bar and my boost curve on the street would rise to 15 psi around the torque peak and then fall to 11 psi at redline with the wacky boost control setup I was using at the time. Perhaps NA cars can make more than 190 at the wheels, or there is some other factor at work that we haven't considered on the turbo cars. I don't know quite what is going on, but it doesn't seem to be a new phenomenon.

-Max

little rotor

What Jesuscookies is talking about would be true if all other factors remained the same.

I think the answer is that VE does not remain the same.

RETed

If we're solely basing engine load to MAP sensor readings, then yes you're correct.

The problem with this is that it ignore the parameter called "air flow", which is actually MORE important than boost.  How do you think bigger turbos make more power?  If it was all dependent only on boost, then we would all run just ONE turbo model and change the boost!

DO A SEACH - it has been covered MANY times in here.


-Ted

Jesuscookies

iTrader: (1)

Please post this info as soon as you get it. I am very interested in the #'s....As I am sure everyone else on this damn thread is!!!

maxcooper

There may be two issues:

1. How does a bigger turbo make more power at the same boost level?

2. How can turbos make more than twice the power at PR=2 than you would expect based on the same engine at PR=1 (no boost)?

Issue #1 has been covered many times -- less exhaust restriction from a bigger turbine and bigger compressors being more efficient at higher flow&boost levels will make more power than a smaller turbo at the same boost.

But I haven't seen much (or any) coverage of issue #2. I am not totally sure that issue #2 is "real", but I haven't seen any convincing arguments that it isn't real.

-Max

Nuvolari

iTrader: (4)

RD85, from what I saw it was a very solid turbo.( huge snail) I didnt see his manifold but the turbo "from my understanding is :


Compressor is from a non ball bearing Garrett turbo, the turbine side is made by Borgwarner .I am not sure who makes the wheel inside , but its made of inconel. Thats very cool .So I would say its a hybrid .

Jesuscookies

iTrader: (1)

You are right on both accounts.

I understand, and was not really asking about situation 1. Simplistically, more efficient, better matched turbo = higher horsepower. That is easy enough to understand

On the second account I agree as well. I do not know if it is an issue or not, but I am curious how a turbo could cause a situation like this, when physics seems to suggest otherwise.

BoostedRex

Did the dyno runs happen today or is that scheduled for tomorrow? I can't wait to see what kind of magic Kan pulls out of a GT40R setup.

Zach

RETed

That's a really complex answer, and it has to do with engine VE and turbo (compressor) efficiency.  There's a lot of complex engine dynamics that's going on that's way over my head, so I can't present a thorough presentation for you.  Keep in mind that the turbocharger presents a slight restriction to the intake system (Corky Bell quotes 10% to 15%), so that might hint to the drop in power while not in boost.  The turbocharger allows you to "recuperate" some of the lost energy that shoots out the exhaust that would normally be totally lost in a normally aspirated application.  I've seen graphs that claim anywhere from 30% to 40% of the combustion energy is lost out the exhaust.  With the turbo, even claiming 5% to 10% is a LOT of energy being applied back into the engine that would normally be lost as exhaust energy and heat.


-Ted

rusty's_silver_bullet-7

Alas, the dyno run was today - didn't go as well as planned and I think it would be unfair to judge the full potential of this turbo set-up based on one day (that didn't go very well.......)

This is my car BTW and as you can tell, I'm a little dissappointed.

Wasn't really a turbo issue - the engine actually lost compression during the tuning session. Steve didn't get to complete the tuning cause the engine was losing compression with each run.

That being said, we did manage a 371 rwhp (Dynojet) at approx. 1 bar of boost before we pulled the plug.

I am pretty impressed with the turbo and believe it will perform as predicted when the supporting cast is up to the challenge.

Back to the drawing board.....

Russ.

CCarlisi

That sounds eerily familiar to my friend's problem with his 35R and street port. So far it has claimed 3 motors and we still don't know the cause. Hopefully yours is not as mysterious.

-Chris

maxcooper

Sorry to hear things didn't go as planned, Russ. I was hoping to hear some dyno numbers, but it is clear that the results of your dyno session aren't representative of what we should expect from the GT40R.

Do you know what happened to the engine? Was it a fresh rebuild?

-Max

CCarlisi

I believe Pettit built the motor.

"Thread: Who wants Steve Kan tuning?

Just installed a GT40R kit from A-Spec and I should be run-in by then......new Pettit Street Port engine as well. . .

Russ. "

maxcooper

The 190 RWHP number we have been using comes from NA 13Bs with the intake and exhaust opened up. Surely a non-functional turbo (e.g. cut the shaft in the middle) would hurt the power due to the intake and exhaust restrictions, so that isn't really the baseline we were comparing against, though in some ways it would perhaps be more appropriate.

The idea that the turbo harnesses some power that would otherwise be lost out the tailpipe seems like a reasonable culprit for the greater-than-expected gains when you add a turbo. I would figure that some power is lost due to the intake and exhaust restrictions that the turbo adds, and then those losses are more than made up for by harnessing the additional energy in the exhaust. I guess that some of the energy used to run the compressor is essentially "free" and shows up as power on the output shaft. I can't say it is all crystal clear in my head yet, but that does make a lot of sense.

-Max

BoostedRex

Do you guys think that there is some type of correlation between the GT turbines and engine failure?? I can't see how that could have anything in common with each other. Maybe I'm just dumb and can't see something that's in plain view.

Zach

maxcooper

Lots of people are running GT35Rs without popping their engines (I think), so I don't think there's a correlation.

-Max

rusty's_silver_bullet-7

Yes, the engine was a fresh rebuild - 1500 miles.

Not sure - yet -what happened to the engine - although it did have some peculiarities before the dyno pulls. At this stage, I'm not ready to conclude any correlation between the GT40R and the issues with the engine.

Investigation pending.....

modrx7

iTrader: (1)

When are we getting R85 numbers... as well is there anybody else who is gonna put up numbers for the GT40R soon?