Mythbusters - engine & dyno edition

[JeffMcKC]

I know of one builder who I think is always low on timing, his stuff runs like few others BIG MONEY AND POWER N/A and power adder stuff. 15* engine like mine he is at 27* I am at 33* thats huge. But he keeps how he does and gets close to the vest. Its not dyno power they run quick and very high mph wins championships that way too

[CDMBill]

So I'll add some observations from yesterday's Famoso outing. At the engine dyno session back in September we made best power on 100 octane VP unleaded by adding timing up from 26* to 27* at 6000 RPM, to 28* at 6500 and then 30* at 6800 through the end of the pull at 7500. This was worth 14 HP at 7500 with increases starting at 6100 over the flat timing.

On Saturday I had run consistent low 139 MPH, so for Sunday I decided to experiment a bit as I'd previously run 140 back in Topeka at the Sunday DW TnT. I was also running a 75/25 mix of Chevron pump premium and VP 100. I flatened out the timing staying at 26* all the way out the back door. I picked up an average of slightly less than 1 MPH to 140 and change at a higher DA. Depending on which calculator to believe this was worth between 16 and 20 HP. (I used the Wallace racing calaculator and the one that comes with RaceIQ)

[Barry_R]

I rarely say "never" anymore. The more I screw around with this stuff the less I think I know. My old Torino has literally thousands of passes on it and while comparatively slow (10s/11s/12s depending on the decade) it was about as thoroughly flogged as a combination could be. At one point I would bracket race it at as many as three local tracks in a given weekend without changing the dial-in.

That car, when running an iron headed tugboat engine, would leave significantly better on 45 degrees of timing. You could feel it, and see it in the 60 ft times. Pulling 4 degrees out in high gear would not change the ET enough to tell, but was ALWAYS good for 1 MPH in the traps. The launch was important and would show on the time slip, the MPH helped when I was chasin' or trying to hold someone off. I cannot tell you they "whys" and "hows" - just flat know that it worked better that way.

On my EMC junk I thought I was gonna open a whole new world of tuning possibilities with the digital ignition and then the EFI. Turns out that the two engines since then did not care - the best timing at 2500 was the best timing at 6500. Every time. Sound familiar?

[dieselgeek]

So I'll add some observations from yesterday's Famoso outing. At the engine dyno session back in September we made best power on 100 octane VP unleaded by adding timing up from 26* to 27* at 6000 RPM, to 28* at 6500 and then 30* at 6800 through the end of the pull at 7500. This was worth 14 HP at 7500 with increases starting at 6100 over the flat timing.

On Saturday I had run consistent low 139 MPH, so for Sunday I decided to experiment a bit as I'd previously run 140 back in Topeka at the Sunday DW TnT. I was also running a 75/25 mix of Chevron pump premium and VP 100. I flatened out the timing staying at 26* all the way out the back door. I picked up an average of slightly less than 1 MPH to 140 and change at a higher DA. Depending on which calculator to believe this was worth between 16 and 20 HP. (I used the Wallace racing calaculator and the one that comes with RaceIQ)

I'm surprised that nobody has jumped on this yet - an actual example of pulling timing from Mean Best in top gear and picking up mph!!

[A/Fuel]

Okay, why do you think that happened?

[JeffMcKC]

It would be interesting to see the MPH and ET between runs all the way down track before and after.

[CDMBill]

Using my handy RaceIQ i have this data to report. I added the corrected figures because the run comparison tool in RaceIQ gives you that data automatically.

Saturday Sunday with flat 26* timing
D/A 1164 10:42 AM 2252 12:29 PM
60 ft. 1.563 1.569
330 4.197 4.202
1/8 ET 6.401 6.394
Corr. 6.323 6.226
8th MPH 111.47 112.25
Corr. 112.86 115.36
1000 8.304 8.287
1/4 ET 9.918 9.891
Corr. ET 9.798 9.631
1/4 MPH 139.10 140.11
Corr. MPH 140.84 143.99

I basically believe the various timing timing curves or lack therof represent fuel changes. On the engine dyno mean best timing was a flat 28* with VP MS 109 oxygenated unleaded, when we switched to VP 100 unleaded we lost 22 at the peak. By adding back timing in a small ramp up to 30* at 6800 we closed the gap to 8 HP peak, 5 avg. over the affected range 6100 to 7500. I suspect this is because of the different burn rates. I snuck up on the fuel as this was a new motor and we pushed the static compression to 11.86.

At the track Sat and Sunday I was running 75/25 Chevron Cali Summer blend 91 and VP 100 as insurance as these were the first runs since my Drag Week fail. At Topeka we had 91/93 and 110 in it for Sunday Tnt with the ramped timing and ran nearly identical mph to last weeked. The Cali 91 doesn't need the timing appearantly.

[CDMBill]

There is a wysiwyg issue here with posting sorry for the eye chart.

[CDMBill]

So given I had realized that part of the new found consistency on the launch might also be explained by a newly too tight converter that was flashing to 5000 I thought I'd try another timing based fix, adding timing at the bottom end. Looking carefully at the graph in the upper left you see a red line representing total advance. When the green line, the Throttle Position Sensor jumps indicating full throttle off the approximately 2000 RPM footbrake you see the total timing jump in steps up and back down in a little stepped pyramid. This represents adding a maximum of four degrees to the base 26* right as the rpm comes up. The goal creating a bit more torque to improve the 60 ft. time. I tried this in two stages and it seemed to help by about .06 with 60fts falling form 1.56 to 1.5 on average over two days. I had used this same approach back in '07 when a new combination also had a bit too conservative stall speed. I don't know where this falls on the myth/bust curve but it has worked twice for me in these sub-optimal driveline hardware situations.