Previous Thread
Next Thread
Print Thread
Page 2 of 2 1 2
Re: How much does ignition timing affect 1/4 mile MPH. [Re: Mick70RR] #984850
05/05/11 09:37 PM
05/05/11 09:37 PM
Joined: Feb 2005
Posts: 4,321
Prospect, PA
BSB67 Offline
master
BSB67  Offline
master

Joined: Feb 2005
Posts: 4,321
Prospect, PA
Without DA data from both days and wind conditions, it is hard to say if its timing or a combination of things. Everything else being equal, 4 mph sound like a lot to me. My iron headed-no quench 440 liked 40 to 41 total timing. The et fell off more than the mph down at 35 to 36. Next time you go, try both settings to see the effect and let us know.

Re: How much does ignition timing affect 1/4 mile MPH. [Re: Mick70RR] #984851
05/05/11 10:28 PM
05/05/11 10:28 PM
Joined: Jan 2003
Posts: 16,932
NC
440Jim Offline
I Live Here
440Jim  Offline
I Live Here

Joined: Jan 2003
Posts: 16,932
NC
IMO, most of the mph loss was the weather (temp, humidity, baro pressure, DA, and the wind). The ignition timing will effect the car/power/torque, but I don't think you will see that much from those two settings by itself.

Just to show how little it can effect things, and each car is different, this is my track testing. Now this engine doesn't need much timing; likely because it is flat top piston, 0.039" quench, good combustion chamber shape (Indy 440-1), 13.5 CR, on E-85 ethanol.

Re: How much does ignition timing affect 1/4 mile MPH. [Re: 440Jim] #984852
05/05/11 11:15 PM
05/05/11 11:15 PM
Joined: Oct 2003
Posts: 7,506
Az
Crizila Offline
master
Crizila  Offline
master

Joined: Oct 2003
Posts: 7,506
Az
Interesting stuff, and I agree. I run flat tops, good chamber and a tight quench on my 408 and I have done some timing testing with the same results - little change in ET / speed. I think this scenerio can be different when you have something impeding the flame front, start getting in to detonation, run way rich or lean, etc.


Fastest 300
Re: How much does ignition timing affect 1/4 mile MPH. [Re: Crizila] #984853
05/28/11 05:04 PM
05/28/11 05:04 PM
Joined: Oct 2007
Posts: 288
Birmingham, England
M
Mick70RR Offline OP
enthusiast
Mick70RR  Offline OP
enthusiast
M

Joined: Oct 2007
Posts: 288
Birmingham, England
Just to let you all know, I was back at the track today with the timing set at 38 degrees and the mph was back to normal. Had a slight tail wind this time so I'm not sure if it was the headwind or the timing or a bit of both but I'm happier than I was a few weeks ago.


1970 Road Runner 505 cid MCH CNC ported Stealth heads MP 528 camshaft 4 speed GV overdrive 11.98 @ 117 on street treads
Re: How much does ignition timing affect 1/4 mile MPH. [Re: Mick70RR] #984854
05/28/11 11:06 PM
05/28/11 11:06 PM
Joined: Oct 2003
Posts: 7,506
Az
Crizila Offline
master
Crizila  Offline
master

Joined: Oct 2003
Posts: 7,506
Az
Quote:

Just to let you all know, I was back at the track today with the timing set at 38 degrees and the mph was back to normal. Had a slight tail wind this time so I'm not sure if it was the headwind or the timing or a bit of both but I'm happier than I was a few weeks ago.


Weather changes can make it difficult to sort things out, especially when you don't have a weather station


Fastest 300
Page 2 of 2 1 2






Powered by UBB.threads™ PHP Forum Software 7.7.1