Can someone run a engine dyno program......

Ron Earp · 02-03-07, 07:59 PM

Our beloved TR8 is about halfway through a head swap with some flowed and ported heads. I would like to know what sort of flywheel hp that is the maximum theoretically possible for the motor, if someone can calculate that or estimate it.

I'm not sure all of the parameters that you'd need, but here are some basics:

Compressoin 8.6:1
Displacement 3.5L, 215 inches
Bore 3.5" x 2.8" stroke
Max valve lift 0.400"

Now, don't laugh, but the best the head will flow, with intake, is 70 cfm/min on the intake side at 0.400" lift. I have the flow numbers by lift and will post them.

Max RPM will be about 6000. Head design is decent, 1.5" primaries, about 25 to 30 inches long to collector, four into one on each side, then joining into a single 3" exhaust. No muffler. All mandral bends.

What else would be needed? Induction is two Zenith Strombergs, each one 1.75" bore, and they definitely aren't the limiting factor on the motor, that crappy intake is for sure.

Ron

Colin Artus · 02-03-07, 08:59 PM

Well using what info you give I get Bhp 237/ Tq 207 @ 6000 , peak Tq 228 @ 4500. Usefull info to make it more accurate would be valve sizes, lifter type, dual or single plane manifold, cam intake and exhaust duation @ .050 and
lca. The prog I have is crude but it does the job.

Ron Earp · 02-03-07, 09:59 PM

A poor dual plane intake, and hydraulic lifters, flat tapets. I'll get the cam specs and flow numbers tomorrow AM. Thanks for giving it a shot!

Ron

Alex Hirsbrunner · 02-03-07, 10:56 PM

I know these programs vary a lot in their accuracy, so here is what I got (using only the one flow value) that you can average into the mix...

I noticed after I ran the numbers that you mentioned open headers into 3" collectors, this boosted the #s to 183HP@5250/198TQ@3500

Regards,

Al

P.S. I know you probably don't care, but it should run a 15.29 Quarter mile @ 87.6 MPH based on published weights (the car's, and yours

)

Jac Mac · 02-04-07, 01:22 AM

I dont have a program, other than the space between my ears,but already it has told me your primaries are too short. Now if your care to divulge your valve timing events( @ the seat ) and tell me that 8.6/1 comp is a misprint I could work out what you need. In any event you should be able to extract up to 220/230 hp before the carbs @1.75" ea become a problem.

cheers
Jac Mac

Ron Earp · 02-04-07, 08:41 AM

Al, you might be about right on! The last rear wheel dyno event recorded 159 rear wheel hp, and about 180 ft/lbs of torque, at 5200 and 3500 respectively. Al, did that program have stock TR8 cam info etc in there?

Jac Mac I'll get the numbers when Jeff brings back over the sheets. We've got to finish up the head swap today, right now there are TR8 bits littering my garage and we're on a tight schedule. I'll measure the primaries with a tape instead of guessing. They might be longer than I think. Or shorter.....And no, it is 8.6 CR........

R

Alex Hirsbrunner · 02-04-07, 10:56 AM

Hi Ron,

No stock info for the TR8 cam, but I will see what I can dig up. Most simulators (at least in the range that I can afford) are really best used to compare the relative difference between scenario A vs B, and are not that great at giving you a right on-the-money HP and TQ curve.

If I had the opportunity to choose, using the program in "the space between Jac Mac's ears" is what I would go with!

Al

Alex Hirsbrunner · 02-04-07, 11:18 AM

Most of the "stock" replacement cams for the TR8 I have found fall into the range below.

Al

Jac Mac · 02-04-07, 03:21 PM

Why are you fitting the heads then? Have you got the piston to head clearance down to around 0.040". You need to deck the block to obtain this dimension- once that alloy block warms up the deck clearance will increase.

Jac Mac

Ron Earp · 02-04-07, 07:46 PM

Hey Al,

your cam numbers match what it in the TR8 book so that has to be it, but I'll find all the real specs for it. Compression ratio has been calculated and heads cc'ed, gasket taken into account etc - it is right at 8.6:1, actually a tiny bit over like 8.62:1, but that is the max allowable. The primaries are actually approximately 33-35" long, or thereabouts, not what I estimated eariler. Pulled a tape down on them when I was undoing the exhaust today.

The intake flow is like this:
0.050 11.92
0.100 24.35
0.150 39.32
0.200 46.64
0.250 55.04
0.300 59.07
0.350 62.84
0.400 69.26

The exhaust flow is not much different from the intake flow on the bench.

Alex Hirsbrunner · 02-04-07, 09:16 PM

Hi Ron,

Using your flow numbers and bumping up the CR to 8.62 gave these results (1 more lb-ftTQ)...

Regards,

Al