Turbo help needed...
#76
Addict
Rennlist Member
Rennlist Member
Join Date: May 2004
Location: Undecided
Posts: 1,990
Likes: 0
Received 0 Likes
on
0 Posts
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Originally posted by Geoffrey
There is something called the A/R number of a turbine. It determines the velocity the exhaust gasses exit the turbine and enter the turbine blades. In general, a lower number = higher velocity = less lag, but there is more to it than that. I believe that the k16 has a .8 a/r and the k24 has a 1.0 a/r, but I'm not positive on the k24. By changing to a lower a/r, the turbo will spool faster, but will create more backpressure and overall turbine rpm will increase.
You can "clip" a turbine which essentially makes the turbine blades smaller (the RUF pictured earlier looks to be clipped) so it doesn't "bite" as much air, again, helping spoolup, but trading some efficency.
There is something called the A/R number of a turbine. It determines the velocity the exhaust gasses exit the turbine and enter the turbine blades. In general, a lower number = higher velocity = less lag, but there is more to it than that. I believe that the k16 has a .8 a/r and the k24 has a 1.0 a/r, but I'm not positive on the k24. By changing to a lower a/r, the turbo will spool faster, but will create more backpressure and overall turbine rpm will increase.
You can "clip" a turbine which essentially makes the turbine blades smaller (the RUF pictured earlier looks to be clipped) so it doesn't "bite" as much air, again, helping spoolup, but trading some efficency.
Thanks for the info. By trading some efficency would you say at top end or through the continuing pull to the red line between gears.
#77
Nordschleife Master
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
With a clipped turbine, you are not getting as much energy turning the turbine as a nonclipped turbine. You can think of it as having a house fan with 5" wide blades, now you shave the blades to only 4" blades. It has the same diameter, but less surface area to push air. Clipping is relatively old school, and with the wide options available today, you can match a turbine/compressor combination for most applications. I like to stay away from clipping, to me it means that you've not chosen the correct turbo.
#79
Nordschleife Master
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Let me clarify my statement about clipping being "old school". There are probably times when it can be useful, but those are probably few and far inbetween. The turbo on my 930 has a clipped turbine wheel which was done as we were developing the turbo and having difficulty with overspinning and destruction of shafts. It no longer needs a clipped turbine with the latest compressor wheel and I'm probably giving up some turbo performance by having it clipped.
#80
Addict
Rennlist Member
Rennlist
Site Sponsor
Rennlist Member
Rennlist
Site Sponsor
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Goose.. If you are going to change to a smaller hot housing, and a different diameter turbine wheel, well you have the makings of a K16 already....
Clipping is not needed for the K16's at our displacement levels, most people will install no cat, or muffler bypasses... We want MORE energy to turn the turbine wheel... it's called LAG reduction.. IF someone is hell bent on having clipped wheels, that's not a problem, I clipped Geoffrey's.. The reason was that we were working with a very tight A/R.. You trade something and give up on something else... It has proven to be a good design!
Clipping is not needed for the K16's at our displacement levels, most people will install no cat, or muffler bypasses... We want MORE energy to turn the turbine wheel... it's called LAG reduction.. IF someone is hell bent on having clipped wheels, that's not a problem, I clipped Geoffrey's.. The reason was that we were working with a very tight A/R.. You trade something and give up on something else... It has proven to be a good design!
#81
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
I was not referring to the dyno you posted. Someone posted a dyno not too long ago on a completely stock 993TT and there was a drop in both hp and torque at 4000 or 4500--that is the dip I was referring to.
The one thing in common between the dyno you posted vs what I remember seeing is that there is drop off shortly after 5K. If the K16 hybrids will hold 28psi to redline, and if the ECU is not pulling timing, I don't see why the car would not continue to make power to, say 6000 rpm.
The one thing in common between the dyno you posted vs what I remember seeing is that there is drop off shortly after 5K. If the K16 hybrids will hold 28psi to redline, and if the ECU is not pulling timing, I don't see why the car would not continue to make power to, say 6000 rpm.
Originally posted by Geoffrey
I'm not sure what you are confused about. What are you defining as the dip? Where are you expecting torque and HP to peak at? Redline?
In the graph you posted, the torque falls by about 125ft/lb between 4000 and 6000. I would not call that consistent. In the graph from my car it falls only 80ft/lb of torque at the wheels (about 100fw) from peak torque at 5000rpm to 6000rpm.
Also, with the way Dynapack displays the graphs, it is squished left/right compared with the RUF graph shown above.
I'm not sure what you are confused about. What are you defining as the dip? Where are you expecting torque and HP to peak at? Redline?
In the graph you posted, the torque falls by about 125ft/lb between 4000 and 6000. I would not call that consistent. In the graph from my car it falls only 80ft/lb of torque at the wheels (about 100fw) from peak torque at 5000rpm to 6000rpm.
Also, with the way Dynapack displays the graphs, it is squished left/right compared with the RUF graph shown above.
#82
Addict
Rennlist Member
Rennlist Member
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Originally posted by Geoffrey
TB, What does your dyno sheet look like from RS Tuning?
TB, What does your dyno sheet look like from RS Tuning?
My motor has over 500fwhp between 4250rpm and 6800rpm (I am not at home so can´t post actual sheet) - The dyno run you posted shows what I have been talking about, that is the k16s cannot hold near the peak power to the red line. My K24s do and this is all I have been arguing about. I would love to believe that a K16 based turbo could do this as I would be first in the queue for a pair. When I was speccing my motor, RS gave me the option of K16 based hybrid turbos - they said the car would feel very fast since the K16s would spool up very quickly and put on a lot of torque/power between 3000 and 5000rpm making the car very fast in street driving. and the curves they showed me were similar to the one you posted with the power peaking at 5000 rpm (as high as 540hp in one chart) then dropping thereafter to the red line - I am not arguing that this is one way to go for a fast 993tt, and indeed is probably very suitable in the US where you may not get much opportuninty to get over 120mph, but a K24 car which will hold near its peak to 7000rpm will have much bigger area under the curve between 5000 and 7000rpm and will ultimately be quicker. Not to mention the thrill of taking the engine to the red line
![Big Grin](https://rennlist.com/forums/images/smilies/biggrin.gif)
I appreciate your continued posting and I am not in any way trying to put down what Kevin is doing, just trying to understand it better with a few more facts.
What I really want to see is a dyno of a properly specced 993tt with K24s which have been "breathed on" by Kevin
![Cool](https://rennlist.com/forums/images/smilies/cool.gif)
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
#83
Addict
Rennlist Member
Rennlist Member
Join Date: Apr 2003
Location: NC
Posts: 868
Likes: 0
Received 0 Likes
on
0 Posts
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Kevin,
Thanks for the clarification. Great posts as always.
TB,
I would think with your engine internals and tuning your car would be a prime candidate for some of Kevin's turbo's. I bet that with help from the folks at RS Tuning you could ring out some additional power with more efficient Turbo's be it K16's or 24's and not much else.
The pound to dollar exchange would make the cost efficient as well.
Thanks for the clarification. Great posts as always.
TB,
I would think with your engine internals and tuning your car would be a prime candidate for some of Kevin's turbo's. I bet that with help from the folks at RS Tuning you could ring out some additional power with more efficient Turbo's be it K16's or 24's and not much else.
The pound to dollar exchange would make the cost efficient as well.
![Cheers](https://rennlist.com/forums/images/smilies/beerchug.gif)
#84
Nordschleife Master
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
TB, the torque and power drop are NOT from the turbos not flowing enough air or not being efficient enough. As you can see from the datalogging, the turbos maintain boost pressure to redline. The engine falls of because that is the natural power curve of a 993tt engine. The car was also set to run at significantly less boost pressure than you are running.
#85
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
If that is the natural power curve of a 993tt engine, what is the point of turbos being able to hold that much boost to redline? Which line is the boost line again, the red line nearest the bottom?
#87
Nordschleife Master
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Hatchy, I don't mean to sound argumentative, but I think you are not understanding fundamentals of how an engine works. Both the car I dynoed, and the Ruf Turbo R have peak power roughly at the same point 5100 give or take a little. I don't know of any car that produces peak torque or HP at redline. Redline is a function of engine stress, not HP or torque.
The point of having turbos that flow efficiently to redline is that it will produce more torque than a turbo that is falling off. The more torque at a given RPM will produce more HP at the same RPM. Remember HP = torque * RPM / 5250. Even though the torque is falling off after its peak, an efficient turbo, maintaining flow will lessen the torque drop.
The point of having turbos that flow efficiently to redline is that it will produce more torque than a turbo that is falling off. The more torque at a given RPM will produce more HP at the same RPM. Remember HP = torque * RPM / 5250. Even though the torque is falling off after its peak, an efficient turbo, maintaining flow will lessen the torque drop.
#88
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
I don't understand a lot of things, so maybe you are right.
I am sure there is a perfectly good reason--one that I simply can't understand--why turbos making full boost to redline, doesn't make
any more power or torque after 5K with proper tuning. If the K16s
slow the drop off torque after 5K, it isn't reflected in the dyno you posted.
z06 seems to make peak power at redline
so does the yamaha r6
Honda B18C5
NSX
E46 M3
I am sure there is a perfectly good reason--one that I simply can't understand--why turbos making full boost to redline, doesn't make
any more power or torque after 5K with proper tuning. If the K16s
slow the drop off torque after 5K, it isn't reflected in the dyno you posted.
![](http://www.racetek-engineering.com/images/taldyno.jpg)
z06 seems to make peak power at redline
![](http://www.c5frc.com/graphics/dyno/Dyno%20Base.jpg)
so does the yamaha r6
![](http://www.mototuneusa.com/R6PortingDynoSheet.gif)
Honda B18C5
![](http://www.dynospotracing.com/images/TypeR.jpg)
NSX
![](http://www.dynospotracing.com/images/97nsx3.2liter.jpg)
E46 M3
![](http://www3.sympatico.ca/hhtuner/cars/HagensM3dyno.jpg)
#90
Addict
Rennlist Member
Rennlist Member
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Originally posted by Geoffrey
TB, the torque and power drop are NOT from the turbos not flowing enough air or not being efficient enough. As you can see from the datalogging, the turbos maintain boost pressure to redline. The engine falls of because that is the natural power curve of a 993tt engine. The car was also set to run at significantly less boost pressure than you are running.
TB, the torque and power drop are NOT from the turbos not flowing enough air or not being efficient enough. As you can see from the datalogging, the turbos maintain boost pressure to redline. The engine falls of because that is the natural power curve of a 993tt engine. The car was also set to run at significantly less boost pressure than you are running.
As hatchy has conclusively illustrated above, quite a few cars produce their peak power at the redline - I suspect you made a typo there
![Wink](https://rennlist.com/forums/images/smilies/wink.gif)
Scott
Yes, I would love to see Bob´s dyno but I think he has been too busy to get a run in.
Last edited by TB993tt; 07-11-2004 at 07:11 AM.