Cylinder pressure? Help.

blue missile said
fishy68:
at your suggestion I went back and put the following cams through the Sim.
Mopar Purple: 280/280, 284/284, 290/290
Lunati: 276/284, 284/292

only the Lunati 284/292 had any improvment in the numbers by increasing HP<6000 and decreasing the Tq>6000. This by about 15Hp & 15FtLbs

I cannot tell you how many cams I have tried with this combo and I keep comming back to the XE285HL.
Thanks for the suggestion though
Andrew

Hey Andrew,

I dont' have the high lift series in my desktop dyno but I'm sure they are better than the standard xe series and quite possibley close to the same as a Lunati. Since I don't have them in the program I forget about them and didn't realize that's the series you were talking about. To compare them you can use the lobe intensity calculator in the cam portion of the program which will show which cam has the greatest intensity.

I have played with desktop dyno alot also with all the cams you mentioned except the xe285hl (didn't have the specs on it or I would've done it too) and noticed they are all pretty close. A 15 hp gain is a pretty large gain if your comparing cams of similiar size. But I have to ask about your statement that the Lunati showed a 15 hp gain at 6000 but also 15 ft.lb tq loss at 6000. How can it loose torque when the hp is greater? I don't remember the hp formula right off hand but I know hp is just a figure arrived using the torque and rpm and a given figure. If the tq was lower the hp would have to be lower wouldn't it? Did you possibly mean a tq loss down low and hp gain up high? Feel free to correct me if I'm wrong.

I'm sure you know Desktop Dyno is a very good guide but isn't all knowing. I first modeled my engine with the Comp XE274 and I had all the head flow numbers and exact compression ratio to put in it for correct readings. Put the car together with it and had problems with their junk lifters twice in 700 miles. Kept draing down terrible after sitting. Got tired of hearing clack, clack, clack for 2-3 minutes when the engine was cold so I modeled other cams and came up with the Lunati 60404 which is just slightly larger. Installed it and even though desktop dyno showed only a 11 hp increase and 10 ft. lb tq increase you'd sware it was closer to 30 ft. lbs and 30 hp it runs so much stronger. I haven't taken it to the track. Just used the G-tech. It dropped from 13.53 @ 105.6 to 13.01 @ 108.8. This was on street radials thus the reason for the slow times compared to the speed.

BTW if you have the specs for the 285hl handy and don't mind please pm them to me. I'd love to have them. Thanks, Tracy