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Noah Holcomb's Avatar
 
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Results with 3.2 Carrera heads on a turbo engine?

I have been messing around with a couple different engine software simulation packages along with crunching numbers on my own. Maybe I have made an incorrect assumption along the way but I am obtaining some unexpected results regarding 3.2 heads on a turbo engine. In fact some of the estimations based on the information available show the 3.2 headed engine not performing as well as the 3.3 engine! I did not expect this outcome at all!

So, for all those running 3.2 heads on your turbo engine who have a dyno graph could you please post those dyno results along with a basic engine build sheet containing key parameters.
Old 04-17-2007, 06:20 PM
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Heat is a killer in air-cooled motors, whether you're using 930 heads or Carrera heads. As long as you keep your boost levels to within moderate levels and have proper A/F's, EGT's, oil and inter-cooling, there's no reason why it shouldn't live on a race track.

Personally, I wouldn't go running sustained boost levels of 1.3bar on a race track, but 0.8 - 1.0bar would be fine I'd think.

My Carrera is purely street and has been turbocharged for many years. No issues with cracked/overheating heads whatsoever.
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Old 04-17-2007, 06:30 PM
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Re: Results with 3.2 Carrera heads on a turbo engine?

Quote:
Originally posted by Noah Holcomb
I have been messing around with a couple different engine software simulation packages along with crunching numbers on my own. Maybe I have made an incorrect assumption along the way but I am obtaining some unexpected results regarding 3.2 heads on a turbo engine. In fact some of the estimations based on the information available show the 3.2 headed engine not performing as well as the 3.3 engine! I did not expect this outcome at all!

So, for all those running 3.2 heads on your turbo engine who have a dyno graph could you please post those dyno results along with a basic engine build sheet containing key parameters.
Noah,
I'd take a good look at cam specs - I'd expect that the 930 cam won't benefit much, if at all from the 3.2 head's bigger ports. Also, from what I've done with engine analyzer, it didn't seem that the program simulated forced induction accurately, especially with respect to cam profile. Most of the blown cars that I saw seemed to make more hp and torque than engine analyzer predicted.

Good luck!

Pat Kelley
Old 04-17-2007, 07:16 PM
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The 930 cam didn't do well with the 3.2 heads according to my simulation results. Most of the simulations I have ran used the EVO GT2 cam and the 3.3 heads still seem to give better results. This can't be the case.
Old 04-17-2007, 07:25 PM
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How about large port SC heads with a 964 cam?

I was quite happy with a prety level torque curve and a nice HP line - 438 RWHP/413 TQ.

I am convinced that the SC heads help more than just a little.
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Old 04-17-2007, 07:28 PM
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It would seem to me that ported 930 heads should outperform stock Carrera heads due to the metalergy involved and the tiny 0.1L advantage.
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Old 04-18-2007, 05:47 AM
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I know it seems odd, but according to some of the top engine builders, it turns out that the metallurgy involved does not make a difference in any aspect.

I'd assume the Carrera head have larger ports and valves than a stock 930 head - the SC heads used on my car (from 78-79) certainly do.

In the old days, the inefficient turbochargers pretty much relied on gas velocity to produce power - the modern TCs are so much better and pump so much more air that sheer volume becomes an issue........and a "bigger pipe" to deliver the goods becomes a goal, of which a part is manifold, heads, and in a different aspect, the exhaust.
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Old 04-18-2007, 06:20 AM
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Quote:
Originally posted by Craig 930 RS
I know it seems odd, but according to some of the top engine builders, it turns out that the metallurgy involved does not make a difference in any aspect.

I'd assume the Carrera head have larger ports and valves than a stock 930 head - the SC heads used on my car (from 78-79) certainly do.

In the old days, the inefficient turbochargers pretty much relied on gas velocity to produce power - the modern TCs are so much better and pump so much more air that sheer volume becomes an issue........and a "bigger pipe" to deliver the goods becomes a goal, of which a part is manifold, heads, and in a different aspect, the exhaust.
The Carrera heads absolutely have bigger ports, but valve sizes are equal. I agree that the metallurgy has no effect on performance, it will/would only effect which head exceeds it's thermal load faster or at a lower temp.

I think the boat has been missed here - Noah is using a computer simulation (like the program "Engine Analyzer") to predict performance of different components, of which the program is NOT showing significant or measurable improvement when using the SC heads vs. the 930 heads. I expect that Noah has imput all of the specific parameters of each head and cam combination, along with intake and boost info, and the program is predicting TQ and HP.

Again, my experience with the specific program 'Engine Analyzer' was that boosted applications tend to be a bit conservative. The program seems to lessen the significance of port size and volume in boosted applications compared to looking at them in a N/A application. In other words, porting/enlarging the heads on a boosted motor produced bigger TQ/HP increases on the dyno than Engine Analyzer predicted.

The program seems to follow the old mantra that porting doesn't help boosted applications. While it's true that pressurizing the intake/cylinder will overcome some flow-related issues that would effect a similar N/A motor, the converse is absolutely not true - porting/enlarging a boosted motor's intake has just as much positive effect on TQ/HP as it does in an N/A application, and maybe more in some cases.

My initial comment regarding the SC head and 930 cam combo was related to what I expected the Engine Analyzer prediction to be - I expect that the 930 CAM cannot keep the valves open long enough to actually benefit from the increased port size of the SC head, irrespective of the boost or N/A application. I would expect that the bigger ports in the SC head need more cam to actually see any benefit, and I'd expect that a program like Engine Analyzer would predict the same thing.

I am curious if any Porsche performance shops are using programs like Engine Analyzer to work out the modifications they develop and/or sell. I do know that in many racing venues these programs are indispensible in developing engines for specific applications.

Pat Kelley
Old 04-18-2007, 06:56 AM
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I use small port SC heads on my 3.2ss motor. It runs fantastic and is fully boosted by 2600 rpm. I run a T4 though. I also am much lower HP levels@300+hp not 400+ I believe you want more intak velocity then anything. The bigger intakes slow velocity..
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Old 04-18-2007, 08:58 AM
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Kellcats521, I am using Engine Analyzer, along with another less powerful program. I think the problem is how this program along with others take such vast assumptions regarding the turbocharger. The data from the compressor map that is input into the program is the peak island efficiency, the pressure ratio, and cfm flow at the center of the peak efficiency island. The only data from the turbine side used is the A/R ratio, housing diameter, and approximate efficiency. Seems to me a large table of values obtained from the compressor map should be required be to generate reliable outputs.

Has anyone here used Dynomation software?
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Old 04-18-2007, 10:11 AM
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Velocity vs. Volume -- the two interact, but in general the older turbo inlet systems relied on velocity and the newer on volume.
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Old 04-18-2007, 11:47 AM
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Noah,

I have not done a lot with EA on turbo motors, but I have seen/done many with superchargers - mostly the centrifical blowers which should on the pressure side be similar to a turbo. As I said, our EA predictions were usually off compared to real dyno data. It was prolly operator error in not spending enough time getting the blower data input correctly.

It is a neat tool, but it can get you waay off without keeping some real-world experience in the equation.

Pat Kelley
Old 04-18-2007, 06:17 PM
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