Has any one ever seen any data on cyl psi
on a motor?

Not from a compression gauge but the psi spikes
as the motor running.

 

Do you mean something like dynamatic compression ratio? How would you see what psi you are running while its running? I mean generally the sensor for the gauge is in place of the spark plug so how would that work...?

Would you have it run on one less cylinder and measure one at a time? I'm a little bit of a noob at turbos, but I'm willing and wanting to learn. I've been reading a great book "Maximum Boost - Designing, Testing and Installing Turbocharged Systems" by Corky Bell. Great read IMO.

 

Let's say that you put a psi gauge in a running cyl
what would the max psi read?

I've had that book for while.
It's is a very good book.

 

I'm not sure about the max pressure, but according to Vizard, the pressure peak should occur about 10-20 atdc.

http://www.gofastnews.com/board/technical-articles/ find the in cylinder combustion dynamics articles, they're a good read, hell just about all of it is.

 

There are many variables that can influence max combustion psi. Static compress, dynamic comp, volumetric efficiency, boost, combustion chamber design , timing, fuel curve , fuel , etc, etc.
I came across some numbers awhile ago but cant find them.
In fact the info I had read was giving Psi #s under detonation and they where scary high compared to a normal combustion event. I can understand why detonation can kill a motor so fast.

I do know that top fuel motors are in excess of 10,000 psi. The people that know wont give up anymore than that cuz of contracts that forbid them too.

I do know that most of the large car manufacturers have been using pressure transducers installed in the heads during motor development and tuning.

 

I'm just looking for somthing in the ball park.

 

2500 psi

Tom Vaught

 

Seem's a little high IMO. Probably more like 800 psi.

 

Tom's number is reasonable, as a peak pressure. I use 3200-3400 psi, 640 bmep as a max limit with my simulation work on my project.

 

After some testing in "engine analyzer pro":

Engine: stock Ford 302 (N/A)

At 1000rpms around 720psi
At 3000rpms around 870psi
At 5000rpms around 790psi
At peak power around 900psi

Engine: stock Ford 302 at 7 pounds of boost from a simulated MP-T70 .68 a/r

At 1000rpms around 720psi
At 3000rpms around 1010psi
At 5000rpms around 1060psi
At peak power around 1200psi

Take into consideration that it is a program, i dont know how accurate it can be.

 

Shouldn't peak cyl pressure occur at peak tq not HP?

 

Yes. You are correct.

 

Indeed you are correct, after looking at the cylinder pressure that the program gives me at the engine peak torque:

Engine: stock Ford 302 (N/A)

At peak torque between 3000-3400 rpms 920psi

Engine: stock Ford 302 at 7 pounds of boost from a simulated MP-T70 .68 a/r

At peak torque also between 3000-3400 rpms 1280psi

 

Double the boost pressure and what do you get?

Tom Vaught

 

Engine: stock Ford 302 at 14 pounds of boost from a simulated MP-T70 .68 a/r

Peak torque at 3200 rpms:

720 crank degrees: 1090psi
724 crank degrees: 1333psi
728 crank degrees: 1522psi
732 crank degrees: 1635psi
--736 crank degrees: 1663psi --
740 crank degrees: 1610psi
744 crank degrees: 1496psi

Graphic at 736 degrees:

#ad



Note: I do not know how accurate this program can be or if I am using it 100% correctly, take these results with that in mind.

 

Here is a company that takes pressure readings on running engines:

http://www.tfxengine.com/

Have a good day!
Michael

 

We use the Kistler Pressure Sensors on some of our dyno engines

http://www.kistler.com/

Tom Vaught