Hot weather tune up?

[dieselgeek]

Did TC say he's going to stop responding to my posts? $100 says he can't do it more than 30 days. Who's taking my bet?

TC, I know you think you're the man around here, but I'd challenge you to make a poll. Have the users decide which one of us goes away forever. DO IT.


Meanwhile, I look forward to your nonreply. haha.

[A/Fuel]

This actually is a different car with a totaly different combo than the other two cars I work on.
Adding fuel in the heat and watching it respond shows how far it was off to begin with. After the clutch locks up the engine will usually start to rpm at a pretty good rate, from about 4800 at less than 3 seconds to 6200, but you have to take air off the fuel regulator and let the fuel pressure lean it out. We were keeping air pressure on it longer letting it bleed off less and it kept going faster.
I 100% agree about once a fuel curve is found with nitro you leave it alone. I've worked for Tom Conway for years and he never changed it unless there was an issue and we needed a quick fix.
The engine one and engine two lines on the racepaks on all three cars are not a steady clean line, unless you use smoothing I've never seen them like DG describes. I'll take a look at the wiring again...I did notice something though, I don't know if I should be conserned but I was shooting the msd boxes with a heat gun while it was running and noticed that one box was 82 degrees while the other one was about 110. I went over and shot a couple more cars while they were running and they were all in the mid 80 range.
At the hit it would have around 62 degrees until the engine reached about 4800 in about .250 sec, then we drop it to around 57, then ramp back in 68 in about .800 sec. This is just to rev it up and get it down the track. I've talked to Randy, and this is pretty much what he does too, a little more sucessfully but similar.
We also raised the compression and added 50 grams to the clutch.

[TC]

added 50 grams to the clutch.

Do you do that by using thicker plates??

[dieselgeek]

This actually is a different car with a totaly different combo than the other two cars I work on.
Adding fuel in the heat and watching it respond shows how far it was off to begin with. After the clutch locks up the engine will usually start to rpm at a pretty good rate, from about 4800 at less than 3 seconds to 6200, but you have to take air off the fuel regulator and let the fuel pressure lean it out. We were keeping air pressure on it longer letting it bleed off less and it kept going faster.
I 100% agree about once a fuel curve is found with nitro you leave it alone. I've worked for Tom Conway for years and he never changed it unless there was an issue and we needed a quick fix.
The engine one and engine two lines on the racepaks on all three cars are not a steady clean line, unless you use smoothing I've never seen them like DG describes. I'll take a look at the wiring again...I did notice something though, I don't know if I should be conserned but I was shooting the msd boxes with a heat gun while it was running and noticed that one box was 82 degrees while the other one was about 110. I went over and shot a couple more cars while they were running and they were all in the mid 80 range.
At the hit it would have around 62 degrees until the engine reached about 4800 in about .250 sec, then we drop it to around 57, then ramp back in 68 in about .800 sec. This is just to rev it up and get it down the track. I've talked to Randy, and this is pretty much what he does too, a little more sucessfully but similar.
We also raised the compression and added 50 grams to the clutch.

Do you know what the mean best timing is for the engine? i.e. have you run it at one fixed advance all the way down the track ever, and observed mph to figure out what timing makes the best power? One of the things that drove me nuts on a few hemi gas engines I've tuned lately, is that I've set up the ability to do fancy timing movement/control like you are doing, but the engine (on the dyno) ends up wanting no more than a 2 degree spread from idle all the way to redline. I could see there being a larger window on nitro - but a spread of 10-12 degrees seems like a lot. The EMC early hemi wants XX, all the time, whether it's idling or WOT - any other number makes lower power and score. Just my $.02. What I'd really like is a crack at that crank trigger signal, in an effort to smooth out the ignition signal.

[CDMBill]

As before I know nothing about nitro. On the the gas motors I keep wondering about timing changes that reflect acceleration rates. I know the really sophisticated dynos can track and load an engine based on logged drag strip passes and delta accel within each gear.

When you add the effects of non-linear fueling I think that there may be a benefit from variances away mean best timing on a fixed rpm acceleration rate.

[TC]

As before I know nothing about nitro. On the the gas motors I keep wondering about timing changes that reflect acceleration rates. I know the really sophisticated dynos can track and lad an engine based on logged drag strip passes and delta accel within each gear.

When you add the effects of non-linear fueling I think there is room for an maybe need for variances from mean best timing on a fixed rpm acceleration rate.

I think A/Fuel said it a long time ago that you can pretty much take everything you know about tuning a gas engine and throw it out the window when it comes to running nitro........ I never really understood that until A/fuel showed me the things that he did...... Nitro carries it's own oxygen and AFR's for 100% nitro are in the 1.3:1 range..... It's more like trying to light a garden hose on fire than an air/fuel mixture........

[A/Fuel]

Do you know what the mean best timing is for the engine? i.e. have you run it at one fixed advance all the way down the track ever, and observed mph to figure out what timing makes the best power?

Depending on the cam, heads, and compression the best timing is somewhere around 68 degrees. I have ran them straight off of the mags. The only reason it would make it down the track was they were really weak engines.
We have a car now that has been 269.xx mph several times, number 1 or 2 usually where ever we go in top speed of the event. It has 68 as it crosses the line. It makes a lot of power, the problem is leaving the line with 68 degrees would cause it to instantly smoke the tires. Like we discussed before, you really wouldn't want to disturb the fuel curve and take fuel out, can't adjust the clutch as it goes down the track like a top fuel car, so we take power away with timing.
Then try to give it timing as it goes down the track as traction will allow.
We've had to take as much as 20 degrees out before....that's not ideal, usually we would add a thicker head gasket to reduce compression or take some fuel away before that. They really respond with timing, cool weather takes less, and hot weather takes more.....then you have to see what the track is like....
I really apprecieate your offer, and even if I have to pay for it myself I'll probably take you up on it. Working on three cars right now keeps me pretty busy. I'm leaving tomorrow to get ready to go to Ohio, then I'm flying to Tulsa to do a display then on to Sacramento, then Seattle.....Then Michigan, Brainard, Bowlingreen, and Indy....lol.

TC.....
We add weight to the clutch buy putting studs, nuts, bolts, and mallory washers on the fingers. studs are around 11 grams, nuts are about 3, mallory can be as much as 10. Depending where you put it it can cause the clutch to come in sooner or later.
The plates (floaters) are just like flywheels between the disks. (3 floaters and 4 disks) The thickness of the floaters is there to take up the space between the disks. We try to keep the thickness of the packs the same so we don't have to adjust the stands too much. It's quicker to change a pack out that way. Thicker packs will absorb heat more and the clutch wil be cooler and less agressive, thinner packs will be more agressive because they get hotter quicker.

[A/Fuel]

I just had one more comment about the jagged timing line on the racepak.
We will record the warm up on alcohol in the pits. It's very smooth then, the timing light confirms this also. I'm wondering though, how much the timing gears, mag drive and belt and the pounding of nitro come into play?
How big of a deal is it to have a msd box about 20 degrees hotter than the rest? That probably has nothing to do with the jagged line, but I'm going to probably swap it out anyway....I had them check it out at the msd trailer in Norwalk and they said it was fine and really couldn't offer an explaination.

[anotheridiot]

Its odd that adding power is helping you on a hot track. Adding nitro is a given, since nitro carries its own oxygen and helps control that hot moist air you have been running. Its just making more power on a hot track you would think would bust the tires loose more often. Maybe you are where you would be in bad tire shake on a normal track. What was the real life condition of the 150 degree track. I was thinking it would be greasy, but it seemed even stickier so it took more power because the tires were not gonna break loose.

[A/Fuel]

I wouldn't say that we are adding power in the heat, it's just that it takes more timing to make power in the heat.
At 60 degree weather we've smoked the tires with 48* timing....at 100 degree weather it could take 60* lead just to get it to move out of it's own way.
That track was really greasy at 151 degrees, wheel speed was pretty high at .500 sec.......it was hanging at around 2000 for a 1/4 of a sec. Very close to going up in smoke, the g-meter takes a dive there, so if I had to do it again I'd take a few (like 2 or maybe 3 degrees out there) and see if it hooked a little better. My luck, it probably would have shook then, lol.
It's close enough though, that adding a 1/2 lb of air to the tires or raising the wheelie bar a turn might make enough difference to leave the engine alone.