Perf Trends Engine Analyzer ?

Hey guys,

A thread in the cylinder head porting section got me messing with Perf Trends again, and for my life I can't get the fuel mixture to improve beyond 'very poor'. No matter what fuel, what octane level, what I do period, my mixture is apparantly crap. Anyone know what parameter directly affects that? Or how to make the calculations realize that the mixture is NOT Poor? lol

Cris

Are you reading from the little notes section at the top? You will always get poor mixture at low rpms, like below 2000, but above that, depending on the camshaft, it usually goes to good. Look at the chart of data for the "A/F Mxtr Qlty %" and you will see it goes to 100% at higher RPMs. Nothing to worry about... it's basically an indicator of too much carburetor or opening the secondaries too early.
[addsig]

just raise the rpm range

Ok that's a good thing...funny thing is it's telling me my carb's too small for my combo lol. I know with these programs you have to 'fudge' a little on a lot of stuff, guess carb size is one of them. I spec'd annular boosters, and an 800cfm carb, and it's telling me my vacuum is too high, and to give more cfm =). Once I get to about 1100cfm, it leaves me alone about it. Funny thing also, it says my 2.055 valves are too small! My MACH# is like .540 or something. It's taken a sick amount of playing around with specs to get a motor I know made 500hp, to make 500hp on this program =).

There are a lot of correction factors and options you need to change to allow you to enter certain data instead of letting it guess. I'm sure you discovered that by now.

Yeah...I did. Thing is, a lot of it I'm 'unsure' of, and the manual didn't do a lot to explain it lol. The motor did finally make about 501hp, but to get it there I don't even know if it's my motor or not anymore with all the minor adjustments etc =p.

What I'm trying to model is an 10.97:1 compression 347 with 5.315 rods, Probe flat tops, optimum quench, Pro Comp 210 heads (basically a Victor Jr...but my flow numbers show less power than the Victor Jr model head, due to more accurate flow testing), and 2.055/1.6 valves. Cam's a mildly aggressive solid roller, 286/246-296/256 adv/.050, .550/.575 w/1.7 rockers, 110LSA 106IC. Intake's a Funnelweb (try finding a model for that!), with an 850cfm Holley and annular boosters (which the program says is limiting my airflow!). 1 3/4 into 1 7/8 stepped headers w/3" collectors (Accufab). With that information it's making 498hp@6500 AND 7000, and 423trq@6000 (wierd spread on the torque/hp I know). Is it accurate? Who the hell knows? In a few months when it's finished I'll be able to tell you lol.

If some of you other guys who are more experienced with this program wanna try, I'd appreciate it. Makes me curious with all the tweaks you can make if I was actually tweaking the right ones =p.

I replicated my engine in that program, just out of curiousity. I went to the track a few weeks later and got some runs in, weighed the car, etc. With hard data in hand, I opened up the engine program and copied the engine into the drag racing simulator. Entered weight, tire size, axle ratio, shift points, etc, the times it gave me were within within .03 at all the incrementals, mph was within .25. I was impressed to say the least. I'd say its pretty accurate if you can enter accurate information.