The engine has undergone some "upgrades". I put that in parentheses as I'm unsure of how effective they were. 34 lb/hr injectors and new fuel rail.
The injectors appear to be mostly a waste of time and money. Last year, running the (supposedly) 27 lb/hr injectors the injectors were running at 94%. The new ones are running 60%. Well, 60% of 34 is NOT 27. Maybe the old ones were 18 pounders. Can't believe everything you read on the internet. The fuel rail came about because I decided to reroute the fuel line and the old rail just was not configured correctly. The new one does look nice. The old was make do and looked the part.
#2 upgrade was a larger (stock!) throttle body.
The new one is on the right and caused throttle issues. WAAY to sensitive off idle. Had to use the cable snail off the old TB. That helped, but was not enough. Made a new bell crank with a slightly different orientation. It has the same overall ratio, but now is quicker at the end of the stroke.
When I made the intake manifold I was concerned about the impact the long (19") narrow (1.5") runners would have on power output. Here are the 3rd gear performance results. I offer them as evidence of the power curve, not to impress.
These are acceleration times as recorded by the data logger. This is not the end all timing method. The computer seems to be capable of logging a max of ten lines per second and most of the data points come out between logged rpm's. But it is a pretty good representation of the engine power curve.
twenty mph = 1576 rpm
20-25 mph- .9sec; 1970 rpm
25-30 mph- .9sec; 2364
30-35 mph- .8sec; 2750
35-40 mph- .9sec; 3152
40-45 mph- .8sec; 3546
45-50 mph- .9sec; 3940
50-55 mph- .9sec; 4334
55-60 mph- 1.0sec; 4720
60-65 mph- 1.2sec; 5122
65-70 mph- 1.5sec; 5516
70-75 mph- 1.6sec; 5910
75-80 mph- 2.0sec; 6304
As you can see, acceleration is very linear from 1500 to 4300, then drops off pretty quickly. It does not feel that way. It feels like the power maxes from about 2700 to 4000. So much for the butt dyno! If I use 6K as the shift point, the engine is well past its power band and acceleration is not good. Shifts are best made at about 4500. That gives much better acceleration as well as axle hop in 2nd and 3rd!
Total elapsed time for 20-80 is 13.4 seconds. That is a very solid number as it is taken directly from the log. I am pretty sure the drop in power is due to the long 1.5" I.D. intake runners. While there is little I can do about the length, it is possible to make up an intake with 1.625" diameter runners. That would be a very interesting exercise and is something I am considering.
A person can very legitimately say this is a mismatch with a torquey engine in a sports car, but I must say that is not all bad. 40 mph in 5th is 1845 rpm, which is the bottom of the power and extends to 4300, 104 mph! It does not run out of the power band in 4th until 80 plus. While not well suited to the racer crowd, it really is a cruiser's delight, especially in hill country. I recently took a friend for a ride. He commented that he kept expecting to hear the dump valve. I took that as a compliment.
In short, if you must use very long intake runners, don't make them out of 1 1/2" I.D. tube unless you are not interested in top end.
Bill