We need a 3D designer on this...Dive School had a few animations to explain some of this stuff, I thought it was pretty cool at the time.

Where are our computer nerds who know a lot about pressure and flow?

Be sure to post up when you can Jeff, I look forward to reading all the different takes on this, maybe my diving one is just got getting across quite the way I wanted it to.

 

Ok, I am with you so far.

 

speaking of intake design--has anyone looked hard at the difference between the front and rear rotor intake runners?
OD

 

Yes. We had this discussion already.
They are equal volume. Whoever (I think it may have been you or RG) that suggested that they are asymmetrical was incorrect.

This is the correlation/observational knowledge in a nutshell.

 

Just to add to my earlier posts and maybe get MM out of the blocks ....

Boost is the only variable we can actively measure acurately and easily and on similar setups will yield predictable results .

If we could all get an accurate measurement for flow and compare this against whp then flow would absolutely be the best variable to compare . No argument.

Unfortunately , due to intake variances and the ability (or lack thereof) of people to accurately calibrate the maf to account for these variances , flow is not such a good variable to compare.

So we are stuck with "how much boost you pushin' bro ?" , like it or not .

 

Well - if you look at MAP sensors - they are often several PSI off, so your still incorrect. They have to be calibrated.

 

Precisely and acutely incorrect.


The "error" in MAF calibration is easily calculated by comparing target lambda and actual lambda values.

 

How so ?


Tell that to followers of Fast and furious and see how far you get ..LOL

 

Because boost tells you less than nothing if you don't have the other variables accurately accounted for (and you don't since you are still grappling with the temperature delta problem as a theoretical value, rather than an absolute one) and the correlation between output and boost is coincidental, not a dependency.


I couldn't give a rats *** about an even more sophisticated audience than that, so why would the ricers concern me?

 

This whole thing can get vastly more complicated if we let it...the actual AFR in different parts of the combustion chamber and the relationships between that and combustion are hugely complex....especially in a rotary engine that has a moving and variable shaped combustion chamber



Face it....We have sensors that are compromises...some more than others that try and tell us simply what is going on in a very complex system...

The MAF is the closest we have in an ideal scenario to tell us what's going past it.....problem is there are things that can fool it if the flow isn't perfect...and it isn't calibrated perfectly.

It's amazing really that we can get all the variables to align to where the things even run at all in a consistent manner

As far as the Fast and Furious comment......I expected better out of you

 

You missed the point of that statement alltogether .

When I read the thread title it implies to me that this thread is all about which variable we should use in a general way to descibe how much power is being made .
Now you guys can spout off g/s numbers all you like but it means absolutely nothing to the "great unwashed" masses .
And the kicker is - even though you talk in g/s as if that is the number we should all watch . I see such massive variances of that measurement on this site that to use it universally as a measure of power is just ludicrous .

 

Boost is worse.......There is now way you can correlate boost with power without knowing a lot more parameters than you would need with mass flow numbers that are already corrected....

 

Yes i agree . If only we all had correctly calibrated maf sensors - we could make some pretty accurate comparisons .

 

The MAF on the car is much closer than we would ever get by trying to compare boost numbers..especially with different turbo's

 

Well my biggest point (while I agree with Ray about engine tuning), is that boost does have a reason to be measured for compressor management and Flow should be what you tune and measure power with.

I think that is why the F&F crowd gets all f-ed up in all of this.

Anything having to do with compressors (like....... uh Boost Controllers); HAVE to use boost as that is what the compressor is managed by. While at the same token - when you start to tune an engine; you have to mentally convert to flow....

Separation on concepts even though they are interrelated is the only logical way since we try to lump power production into "Tuning" - instead of two separate processes.

 

But think about this :

In the highest hp dyno thread there are a number of dynos with various sized turbos . If you look closely at those dynos and compare boost profiles you will find that the numbers match up pretty well .

How can it be that a small turbo can make near as damn the same power as a bigger turbo at the same boost levels ?
We need to think about the effect of the intercooler in all this .
The only boost number people are reporting is the one at the uim - this is AFTER the intercooler and all the pipework .
In doing this we , to a some extent , take away the variables of turbo efficiency .

These are all guesses - just trying to make a point here .
Air from a large turbo may be going in at 12psi and 40C then dropping to say 10psi and 30C
Air from a small turbo may be going in at 14psi and 50C then dropping to say 10psi and 35C

The intercooler is doing more cooling of the air from the small turbo because of the higher temp differential .

The Temp difference is not as big as we may think and therefore the numbers come out very comparable ....

 

That is actually a reasonably valid point - it's technically wrong. But given the small deviations we have in the RX8 today the correlation can made.

Now cruise over to the RX7 world and try that.... guarantee you are going to be way way off.

 

It's called old age!

 

Thought for a microsecond you may actually be agreeing with me there .

I've always been one to make assumptions based on observations of what does happen rather than what SHOULD happen . Then try and figure out why it doesn't happen the way everyone says it should .
As you can tell that puts me at odds with just about everyone - but it makes for a good argument . LOL

 

I mentioned the intake runner not because of a supposivly volumn difference, but because of the different shape/ different path they take.
Does everybody know about #7 cyclinder on the ls-1, ls 2 engine?
If we get enough flow going through this intake then I was wondering if the same could not show its little ugly head?
Turning flow adds up, and the more dense (or viscious) the flow, the more suseptable it becomes.
Now i realize terminology and therory is now being discussed to form a concensus baseline of approach to the discussion.
i just had to throw that out.
OD

 

So , is anyone game to post how many g/s we should see at say :

250whp
300whp
350whp
400whp

????????

 

Depending on a bunch of variables, it is about 1 g/sec per horsepower.

The Renesis makes about one HP per every 1.6 CFM at STP.

This is at the crank.

So, 400 g/sec is about 360 - 380 wheel HP.

 

cheers for that
And depending on another bunch of variables

every 1psi of boost makes apporx. 14 hp at 7500rpm
assuming you have a stable boost profile and average the following boost between 6500 7500rpm you will make approx.

250 @ 5.5 psi
300 @ 9.0psi
350@ 12.5psi
400 @ 16.0psi

 

Again, this is completely wrong.
Even on the same engine, your numbers can be off by as much as 90 HP (whereas my numbers are never off more than .02 of a gram).

I have seen 9 PSI make anywhere from 200 to 330 HP.

I really want to believe that you meant to say something entirely different, because your statement demonstrates a complete lack of understanding.

 

well if you can show me that dyno of a stock renesis that makes 330whp at 9 psi (6500-7500 average) I'll eat my hat (figuratively of course )