Racing Spark plugs? What about alcohol?

Typically when Ive gone racing I usually wind up with a cooler heat range spark plug. Is that still needed?   What about using E85?  

E85 fouls less than gas but can still leave carbon deposits after awhile. You only need to change from the OE heat range if adding compression, boost, nitrous. Methanol we usually just go to a cold plug because they won't foul no matter what.

Thank you.  Since E85 is 85 % alcohol   Won't I need to go colder even with the same 11.5-1 compression?  I'm planning on using racing E85 which uses a high octane gasoline for the 15% that is gas. Not pump grade E85 which might have up to only  51% ethanol and 49% low octane gas.  
   One other question. The later V12's went from 40 BTDC  ignition timing to 17 BTDC with the  later HE engine.   With E85  even though I'm using  the later 11.5-1  compression I'll be able to advance the timing from 17 degrees to about 38-40 degrees.  Is that cause to rethink plug heat ranges?  

Heat range is strictly a rating of how quickly the plug dissipates heat, or cools off between combustion cycles.  If it's too hot then you can get pre-ignition, which can destroy engines.  If it's too cold then you just get fouled plugs.  Modern gasoline, oil rings, valve seals and oils make fouling much less of a problem than it was back in the day.  I'd start with a heat range a couple steps colder than stock in your Jag and go warmer if needed to combat fouling.

Peak combustion temps for E85 is less than gas, by quite a bit.  And since there's just 15% gas, the gas based deposits will be much less.  Maybe one heat range cooler, but I don't see any real reason to do that- the cold plug is more likely to foul on cold fuel that way.

Spark plugs changes always involve alcohol here.

APEowner said:

Heat range is strictly a rating of how quickly the plug dissipates heat, or cools off between combustion cycles.  If it's too hot then you can get pre-ignition, which can destroy engines.  If it's too cold then you just get fouled plugs.  Modern gasoline, oil rings, valve seals and oils make fouling much less of a problem than it was back in the day.  I'd start with a heat range a couple steps colder than stock in your Jag and go warmer if needed to combat fouling.

When I turbo'd a junkyard V12 by kludging it, it wouldn't have worked with regular plugs but Champion had recently come out with Gold Palladium which with its broad temp and resistance to fouling solved my problems.  
   Are there any plugs like that still available?  

frenchyd said:

   One other question. The later V12's went from 40 BTDC  ignition timing to 17 BTDC with the  later HE engine.   With E85  even though I'm using  the later 11.5-1  compression I'll be able to advance the timing from 17 degrees to about 38-40 degrees.  Is that cause to rethink plug heat ranges?  

I would run whatever ignition timing works best for the combustion chamber.  Jaguar was able to run the compression up that high because the chamber burned fast enough that it needed less than 20 degrees of timing, not the other way around.

This is one place where the LS engines are great, because THEY have best timing down in the 24-28 degree range.  The mixture burns too fast for detonation to be as much of an issue, so they take very well to higher compression or boost.

In reply to Pete. (l33t FS) :

I haven't  studied the Chevy's head but I know the earlier Chevy head, the early six cylinder fireball.  It needed a lot of timing and still didn't make impressive power.  
  I fact I've probably worked with  more than a dozen different combustion shapes that I can think of off the top of my head.  
     Timing isn't a matter of combustion shape only. Bore,  stroke, Bore/stroke ratio, valve sizes port flow,  swirl, squish, fuel octane, fuel type, and about a dozen other factors tell you what timing is required for peak power. 

frenchyd said:

Thank you.  Since E85 is 85 % alcohol   Won't I need to go colder even with the same 11.5-1 compression?  I'm planning on using racing E85 which uses a high octane gasoline for the 15% that is gas. Not pump grade E85 which might have up to only  51% ethanol and 49% low octane gas.  
   One other question. The later V12's went from 40 BTDC  ignition timing to 17 BTDC with the  later HE engine.   With E85  even though I'm using  the later 11.5-1  compression I'll be able to advance the timing from 17 degrees to about 38-40 degrees.  Is that cause to rethink plug heat ranges?  

It's the opposite, you can probably run a hotter plug with e85 than you can with gas without causing an issue. Likely doing nothing would be best, but one colder tends to work totally fine. We do boosted engines two colder with no fouling even on gas and up to three on e85 and sometimes 4-5 on methanol. 

Pete has the right idea on the ignition timing. Give the motor what it wants, if timing is low for max power that's the number regardless of your feelings. 

50% is right around the knee point for diminishing returns with E%, you end up using more fuel with smaller gains. Also watch "race" e85s some are better than others. We see very different behavior from Ignite Red and VP C85, the latter really likes to detonate at very high loads. 

In reply to Paul_VR6 (Forum Supporter) :

Very helpful.  I do agree that the best way is to do a run on the Dyno until it tells you where peak power is. You said it better and simpler.  Don't use one timing as ideal for all engines.  
      I'm actually in a position where I need that dyno run. Both to figure out what needles  should be for using carbs instead of fuel injection  and what the two different combustion chambers need for timing.  
       
 Before I used a dyno I used a steep hill right next to my house and a stop watch.  I made a run starting at 2000 RPM with the first mark and a second mark to stop the watch just short of redline. 
     Thanks for that information regarding Different brands  E85. I doubt I would have caught  that myself.  I'd assumed they would all have been similar.  Any thoughts on what might be the reason?  Anything I should look for ( aside from dates) ? 

Finally, your thoughts on perhaps adding some pump grade premium to bring the gasoline content up?  My partners wanted to do some LeMons/ Champcar type racing. Better fuel mileage would be a definite help.  I'm thinking perhaps 15 gallons of pump premium  to 55 gallons of E85?  I'll have to jet accordingly.  Stock jets are .090 I'm using .100 for E85 but if I blend pump premium with E85 I should go to .096?  I'm pretty sure I have a ream that size. 

We still so most of our tuning at the track (dragstrip) as the dyno is just good to get a baseline but the engines do react a bit differently under different loads. We only have access to a dynojet so can't play around with different loads. We have roughed in fuel before on jackstands and on the brakes just using a wideband. It gets close enough to make a safe hit for most setups. 

On the E85 I am not sure, different additives in the gas portion most likely. I have found some documentation that a certain amount of lead may actually be counter productive, and MBTE can do some strange things to certain injectors. We notice it on setups around 100hp/cyl and it gets catastrophic between 150 and 200, you start eating plugs at first then the rest of the motor even with the same tuning approach. 

Not sure on your carby setup but blending in 93 octane pump into E85 shouldn't have any problems. You can do the math to see what volume mix gets you around 50% ethanol. 

The primary point of ignition timing is to get the peak cylinder pressure to occur at the optimal point in the piston travel to produce maximum torque.  That's typically around 8 degrees after TDC.  I'm talking about ignition timing as it relates to peak power under full throttle here.  You can do other things with timing to effect catalyst heating, fuel economy,  and exhaust emissions. 

The amount of time it takes for the pressure to rise in the cylinder is pretty constant compared to the variation in engine speed.  So, you need to start the combustion process earlier at higher RPMs to account for the faster crank rotation. and later at slower crank speeds.

There's a secondary consideration for ignition timing under full throttle.  As the pressure rises in the combustion chamber so does the temperature.  Under some conditions that temperature rise can ignite a region of the mixture that's not part of the primary flame front.  When the two flame front collide there's a sharp rise and the collision is often audible.  That's the marbles rattling in the can sound and and is known a ping or more accurately detonation.  A little bit of detonation won't hurt anything and it's not uncommon for there to be something in the owner's manual of a modern car saying something about that.  A lot of detonation can damage pistons.  If you see a piston with the edge burned away or the ring lands collapsed that's a sign of excessive detonation.  Retarding timing is one way to combat this condition.

So, the goal is ignition timing that produces peak cylinder pressure at the point in the piston travel that produces peak torque if that can be achieved without detonation.

The best way to set ignition timing is on an engine dyno with a pressure sensor in the combustion chamber.  Load the engine up and adjust the timing so that you get peak pressure at 8 degrees ATDC or just before detonation which you can see in the pressure sensor trace before it's audible.

Lacking a pressure sensor you can set timing using the Minimum Timing Best Torque (MBT) method.  Basically you have some way of measuring torque (dyno, dragstrip, hill and a stop watch...) and  advance the timing until torque stops improving or you hear detonation.  With a programmable ignition control and a dyno that can hold a fixed speed you set the timing at something like 500 RPM intervals and interpolate in between the data points.

With a distributor it's more complicated to come up with the timing curve.  Mot of the time you can make sure the advance comes all in around 3,800 RPM, determine your MBT and the base timing at which the engine starts and idles well and modify the advance curve so that it goes from your base timing to MBT and call it good.  There's almost always some power to be found by refining the curve further but that'll get you close.

A quick note on jets.  Drilling them is not a great idea.  Carburetor jets are manufactured, then flow tested and stamped with the rating.  Air flow through an orifice at a given pressure is effected by bore length, surface finish, diameter and the shape of the entry and exit geometries.  A sharp edge or a radius or a chamfer will all have a significant effect on the flow at a given pressure.  Obviously if there's no jets available in the size you need you'll have to resort to that but be advised that you may find the process somewhat frustrating as the changes from drilling won't be linear and it's even possible to run a drill through a jet and end up with a lower flow.

Starting with the last first. . SU jets are long tube like things the needles go in.  The needles are usually specific to a car/ state of modification. They can be easily modified by locating where additional fuel is required on the needle and then using very fine emery paper chuck the needle in a drill bit and spinning the needle lightly dress that area.  Gasoline it's pretty important to get exact but alcohol tolerates richness without losing power the way gasoline does.  This is just one needle of many dozen different ones for the HS4 SU carb.  Standard jet is .090. But  .100 and .120 is available.  Odd sizes do require ream  there is a tiny radius at the top which is easy to duplicate by hand. Yes fiddly work under a big magnifying glass. But like I said  alcohol tolerates errors.  Besides I spend next to no time at idle. 
  Luckily I have my own distributor machine.   So modifying a distributor curve is easily done.  Plus between American, European Union, and  etc. there are sources of various springs, weights, cams.  And what works where.  Besides with the camshaft I intend to use I won't care below 4500 where the timing is ( as long as it's not to far advanced).    Wheel to wheel racing we don't get that low RPM  if we do we shove in the clutch and coast. 

In reply to Paul_VR6 (Forum Supporter) :

You sure are very helpful.  Thank you. 
I'm surprised you use the drag strip that much?  I always assumed a drag strip is too variable? 
 My budget is far too modest to even hope to achieve even 50 hp per cylinder. So I'm in comfortable territory. Especially considering the strength of the components I'm working with. 

In reply to frenchyd :

ET is variable to an extent for the launch, but MPH is a good indicator of the amount of power being put down.  If MPH picks up, you are making more power. (This is where you see traction limited 60s cars running mid-high 14s at 105-110mph.  With traction that would be a second or maybe two quicker)

I tune at the dragstrip by running as quickly as possible into my trap speed gear (usually 3rd) and then doing a long WOT pull.  Spectators probably wonder what the heck I'm doing short shifting first and second.  If I get it into 3rd at the 330' mark then I also get a good indicator of time spent accelerating from 330 to 660 to 1000 then the 1320.  When I think I have a good handle of things, then I do a "normal" pass for ET.  Trap speed is usually within a couple MPH of my tuning runs.

Pete, you'll have to help me understand drag racing. Assuming a test and tune day how often can you run down the drag strip?  The reason I'm asking is I'm trying to figure the variables.  
 Can  I really figure out tuning enough at a drag strip to get the car ready to race?  Would I be more effective on a chassis dyno? 

In reply to frenchyd :

I assume this pretty universal, the strip we used to run had t-n-t night as you could run as many times as you wanted. Theys were open set hours, and to make a pass you just got in line to stage. If you wanted you could make a pass and jump straight back in line. The only limiting factor was how many people showed up.

In reply to gearheadmb :

Fair enough, but how many passes / hour is typical?  4-26-137?   Yes I understand about it depends on how many show up. But I'm trying to get an idea of how productive test and tune is compared to dyno sessions. 
   What's been your experience?   I mean assuming I get in line spend 2-3 minutes getting set up, waiting for the start, 15 seconds accelerating, another 15 seconds coming to a stop and getting off the track ,   3-4 minutes getting back in line, waiting 5-10 minutes to get to the head of the line.  That seems like roughly 4-5 passes an hour? 

Well we know what we are doing (sorta?) so make passes about 1/hr at max as these are dedicated cars that we cool, charge and adjust between passes. We usually look at incrementals more than the rest of the slip. It would take me a bit to explain it all but you can figure a lot out with one hit to the 60 and let off and one clean 660.