Ignition Timing for a turbo'd big block
#980706
04/25/11 11:42 PM
04/25/11 11:42 PM
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Joined: Mar 2006
Posts: 49 Borden, Indiana, U.S.A.
wrenchinrandy
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Borden, Indiana, U.S.A.
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I think I am finally nearing a dyno visit to put some fine tuning on my 451. You guys out there with turbo'd big blocks, what kind of ignition timing should I expect to see under boost? The combination that I have is a 451 with ported Eddy heads and 9.5 C.R., SMPI (Autronic SM2), wasted spark ignition (M&W Pro-drag 4 firing eight coils), and a water-to-air intercooler. I am hoping to run 10lbs or better on 91 octane. If I can't make 10lbs, then whatever it will safely run wil be my limit. Turbo's (2ea) are T3/T4's with 60-1 compressors. If there is any pertinent info I have forgotten, let me know and I will add it. What I am mainly after is what those of you who have your cars sorted out are running. Thanks for any info!
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Re: Ignition Timing for a turbo'd big block
[Re: wrenchinrandy]
#980707
04/26/11 12:24 PM
04/26/11 12:24 PM
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Joined: Jan 2003
Posts: 28,071 Irving, TX
feets
Senior Management
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Senior Management
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Irving, TX
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Each engine is different. My engine was a 440 with 8.7:1 compression, Eddy heads, and a turbo specific cam. No intercooler was used. I had no problems running 12 psi on pump gas. If it wasn't extremely hot outside I could run 17 psi but normally shot some rubbing alcohol in the intake to cool it down. My turbos are hybrids too. T4 60-1 compressors and T3 Stage III turbines with Stage III wheels. Those are perfect for street engines but the turbine outlets will prevent big boost levels. They're simply too small to get lots of exhaust out. If I was making more of a drag/street car I'd use T4 P-trim turbines.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
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Re: Ignition Timing for a turbo'd big block
[Re: wrenchinrandy]
#980709
04/26/11 06:28 PM
04/26/11 06:28 PM
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Joined: Oct 2006
Posts: 200 AB
Efidart
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I run around 32 degrees at upto 10 lbs and bring it down closer to 29 to 30 at 13-15 lbs on pump gas. 9.3:1 572 with victor heads here.
I would start at around 26 degrees total and see how it reacts.
Sure hope hughes didnt give you a reverse split cam...
TT Predator headed 572 7 Second Street Car. Fastest Mopar Drag Week 2015 Fastest Mopar & Dodge Drag Week 2017 Pro Street Power Adder Champion Drag Week 2017
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Re: Ignition Timing for a turbo'd big block
[Re: wrenchinrandy]
#980712
04/26/11 10:45 PM
04/26/11 10:45 PM
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Joined: Jan 2005
Posts: 2,540 Milwaukee WI
TRENDZ
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Any dyno tuner should be able to help you with the timing. Tune for best torque to make the engine live. Don't add timing to make HP, add boost. Always tune for best torque at any positive load points. Don't limit yourself with a pre-determined boost number. You will kill a motor faster with timing than with boost.
"use it 'till it breaks, replace as needed"
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Re: Ignition Timing for a turbo'd big block
[Re: CW25]
#980714
04/27/11 02:49 AM
04/27/11 02:49 AM
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Joined: Jan 2003
Posts: 2,933 Finalnd, Perkele
jyrki
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Our starting point was 40 degrees initial and 20 degrees off at 30 psi. That worked fine, but in the dyno we were able to use even more advance under boost and that did help the power.
Plynouth VIP '67 TT IC EFI
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Re: Ignition Timing for a turbo'd big block
[Re: jyrki]
#980715
04/27/11 10:49 AM
04/27/11 10:49 AM
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Joined: Mar 2006
Posts: 49 Borden, Indiana, U.S.A.
wrenchinrandy
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Thank you all! I really do appreciate the info. Trendz, I don't plan on limiting anything to a certain boost level. However there will be a limit due to the self imposed requirement to run 91 octane. The car is a street car, and I want it to be able to go anywhere on readily available pump gas. I am not against alcohol injection, but as I prepare to go to the dyno, I don't have an injection system.
Randy
Last edited by wrenchinrandy; 04/27/11 03:16 PM.
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Re: Ignition Timing for a turbo'd big block
[Re: Efidart]
#980717
04/30/11 01:10 AM
04/30/11 01:10 AM
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Joined: Jan 2005
Posts: 2,540 Milwaukee WI
TRENDZ
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Milwaukee WI
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I'm not suggesting retarded timing. Peak torque is the indicator that you have a very safe timing curve that will keep an engine alive. If you tune an engine to peak torque, than add timing, you will make more hp at that load point, at the cost of torque and engine longevity. Peak torque indicates a timing curve that is using the energy of flame front to roll the crankshaft forward. If the dyno is showing torque falling off, but hp going up... It tells me that the flame front is happening a bit to soon, creating opposing forces on everything from the headgasket to the main caps and everything in between. Hp goes up with advanced timing because the torque lost to advanced timing gets "stored" in tdc dwell time(high cylinder pressure), and releases in the instant there is any rod/crank angularity after tdc. No problem if you have real strong components...but a very fine line to walk with stock based parts. Lets say you want a stock based 900hp engine. For discussions sake, say the engine is on the dyno and at 15pounds of boost it's making 875hp at peak tq. You could bump in another 3 or so degrees and get real close to your 900hp goal at the same boost level, OR you could give it a touch more boost and re-tune to peak tq timing. The first scenario gets you your 900hp with added internal stresses and less tq, with a more fuel efficient engine. The second scenario gets you the 900hp, added tq and lower internal stresses, with a less fuel efficient engine.
"use it 'till it breaks, replace as needed"
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Re: Ignition Timing for a turbo'd big block
[Re: TRENDZ]
#980718
04/30/11 11:17 AM
04/30/11 11:17 AM
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Joined: Oct 2006
Posts: 200 AB
Efidart
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Trendz, I agree with what you just said, timing is everything. The Problem is 9 out of 10 guys reading the posts on here will interpret less timing into starting at 20 degrees at 10 lbs for example when they should realistically be at 25. We aren't running LS1's or other engines that perform well with low timing, let’s face it 440 Wedge based engine combustion chambers aren't near as efficient..
I do like jyrki's ignition slope, which is an aggressive and safe place to start.
That stock blocked destroked 440 I used to run was very sensitive to timing, 3 degrees too little timing was 130rwhp difference.. (Going from 20-23 degrees.. when in hind sight should have been more like 25..).
TT Predator headed 572 7 Second Street Car. Fastest Mopar Drag Week 2015 Fastest Mopar & Dodge Drag Week 2017 Pro Street Power Adder Champion Drag Week 2017
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Re: Ignition Timing for a turbo'd big block
[Re: wrenchinrandy]
#980719
06/18/11 11:43 PM
06/18/11 11:43 PM
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Joined: Feb 2004
Posts: 1,417 Chicago, IL
blownEFI
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pro stock
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Chicago, IL
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Well I saw Randy's (wrenchinrandy) car run on the chassis dyno today (Hi Randy!) and I was very impressed. It's such a nice docile every day driver type car yet cranks out 730 hp at the wheels. Figure that's close to 860 hp flywheel and thats at only 5500 rpm. If I remember correctly this was done with only 19 degrees of advance and 15 psi of boost. The tuner tried adding a few more degrees but for some reason it didn't seem to like the additional timing. Anyways, very impressive car. Great job Randy.
"These go to eleven", Nigel Tufnel
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