does this make scence at all??

[LX XLR8R]

lets see right now im running a accel 300+ ignition and i opened the plugs(2 heat up to .6 to see if they would just foul out)..they didnt..infact they look brand new with a touch of redish brown ontop so i was just ganna feed it more fuel..i feel that if its running lean that i could turn up the FP and get more power out of it..i know optimum burn ratio is 12.7:1..i guess ill get an EGT and go from their..am i heading in the right here..i know thier is alot of power in tuning(i.e. trophy stock) i just dont want to be another guy stuck in the 12's when i know i could be in the 11's

------------------
1987 black notch(ex 4 banger)
DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one..
AIM=onesillynotch

[Jeff Chambers]

IMHO, 0.060" is too much. As a matter of fact, if you're pushing up the compression you should be taking your gap downward as the compression will tend to quench the spark. The 24# are real marginal for your combination. I'd consider moving up to 30# injectors. You could get an EGT to help you tune. I just started running a dual channel EGT myself with probes on #1 and #6. My temps were up around 1363F while motoring through the traps at 6400. That was with about 43psi of fuel pressure. On one pass I went up to 45psi and the EGT dropped to 1348F so it looked like I had too much fuel. Every day and every track is different though so you'll have to move the FP around to suit the conditions. BTW stochiometric is about 14.7:1.

------------------
Jeff Chambers
Trophy Stock #3
11.86 Seconds / 113.8 MPH
Chambers Racing Team

[LX XLR8R]

just the man i hope would answer..im only running 9.7:1 compression..my combo might be doing ok now considering i could stay infront of a 110+trap turbo si the other night from a 3rd gear roll..what temp do you like to run urs at??what gap do u run ur plugs at? and what kind..hope you dont mind me asking you all these questions but IMO trophy stock guys know how to take a lil and tune the hell out of it..i dont really want #30 injectors only cuz i here people running 24# then chaning over to #30 and they ran better with the 24#..thanks again

------------------
1987 black notch(ex 4 banger)
DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one..
AIM=onesillynotch

[Jeff Chambers]

You ought to see if you can borrow a set of 30# and a MAF from someone to give it a try. Your heads, TB and LT headers breathe a ton more than what I'm allowed in T/S. More air needs more fuel. Just by the description of your plugs says that you might be running a little lean on fuel. I pegged 24# injectors out with regular GT-40 irons and an E cam. Every combination is different though so the name of the game is experimentation.

When checking plugs, the most important area is down inside the plug where the porcelein is in the body of the plug. You want to see some color down there right after a full pass. As you go through the traps, shut the car off an pull off onto the return area and immediately pull a plug. If you wait until you get back to the pits, you've ruined the read with rich & hot idle.

I only run my plugs (Autolite 103) down around 0.045-0.048 because of my compression. Any lower and I seem to loose some ET, anything higher than stock really hurts my ET. I'm also running a colder plug in the 103s because of the compression.

EGTs up around 1360F seem to be pretty common for the guys I run with. Its dependent on your combination, where you have the probe installed and a bunch of other factors so the main thing is to see where your car peaks in temperature and use it as a comparison from there as the conditions change.

------------------
Jeff Chambers
Trophy Stock #3
11.86 Seconds / 113.8 MPH
Chambers Racing Team

[LX XLR8R]

hmm..in ur website you say to run colder plugs for more performance and hotter for streetabilty and gas milage..can you explain this to me..i was thinking that hot would get more of a spark and burn off more fuel giving you more power???also at what PSI or HP do the injectors go static??and why would SKYMAN's car make 3something horse with really low fuel pressure and 24# injectors??thanks again

------------------
1987 black notch(ex 4 banger)
DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one..
AIM=onesillynotch

you're right about the optimum air/fuel for power is 12.7:1 (for best burn 14.7:1, and for fuel economy 17 or 18:1) and it sounds like you'll be able to achieve this. I personally would never mess around with heat ranges because you could easily melt a plug especially with that high voltage ignition, but if you strictly plan on racing it, then i'd swap it. i know that when you change ignition systems the actual power comes from increasing the gap, so you should be fine there, but you're getting into tricky territory with the heat ranges. Another thing to think about is that the larger gap you get the more you stress the coil, so it may fail eventually. Good luck, keep us posted!

------------------
'84 Mustang 5.0 T5, FMS aluminum radiator & 180* thermostat, 1 5/8 shortys/2.5" duals, '88 GT tail lights and wheels, Holley 4160 4 BBL, smog pump idler, more coming soon

A colder plug simply means that the plug wicks the heat away better from the tip of the plug back through the seat, leaving the tip colder. The colder tip resists preignition and electrode corrosion better. Its better for high rpm, high load conditions like in racing.

You'll never melt a plug from the cap discharge ignition systems, 84stanglx. The cap discharge systems have more energy because of the way they release the spark energy. The energy is a function of several things a few of which are electrode gap, discharge duration, and the dielectric constant of the medium in which you're creating the spark. Cap discharge simply creates more energy under the duration curve by ensuring that the primary voltage is at a full charge instantly. But I digress. When you've seen people melt plugs, its because of lean conditions (more times than not) in the cylinder, not because of their ignition system. The blower and nitrous crowd will tell you what a sin it is to run lean. The N/A crowd doesn't have to worry about this so much, mainly because we only draw in a limited amount of air to begin with. As far as plug gap goes, a stock motor with stock ignition system will tend to pick up a little power by gapping the plugs a little further. Since the plug is gapped out, the spark travels further from anode to electrode and hence presents more spark surface (energy) to the mixture which in turn creates more efficient burning. This is true to an extent, but when you start boosting compression ratios in N/A motors or similarly increasing mixture density like with superchargers, the dielectric constant of the mixture goes up. Essentially this means that it is harder to force the spark to jump from anode to electrode. This is why racers bring the plug gap down. Remember that the density of air is directly dependent on pressure (pv=nRT) and so is the dielectric constant. So a rise in cylinder pressure creates a denser cylinder charge with a higher dielectric constant. All things remaining equal it requires more energy to make the spark jump across the same plug gap in a 12:1 motor than it does an 8:1 motor. If the dielectric constant is too high for the ignition system, the spark may actually seek ground elsewhere than the electrode; somtimes to the side of the plug or down inside the plug. This will definitely cause a mis-fire in the cylinder. The ignition systems we play with in cars is really weak in comparison to other ignition systems. An automotive system has maybe .3 joules of energy per spark (~1amp for 150 microsecond from 12VDC power) where an aircraft igniter has upwards of 18 joules of energy (15 amp for 300 microseconds from 240V 400Hz power). You ought to see an aircraft igniter spark. It'll throw a 2" long spark, completely vaporizing the air around the tip of the igniter.

You may have to play around with some fuel programs to actually figure out where your injectors are reaching 100% duty cycle. Its partially dependent on the BSFC (base specific fuel consumption) you assume for your motor. With my 24# injectors, I figure I was hitting 100% duty cycle (going static) at about 4800rpm when I was making just under 300hp at the wheels. I pretty much proved this to myself when I swapped to 30# injectors & MAF between rounds and went back out to run three tenths quicker and almost 3MPH faster. There are some programs out on the internet that will let you play with injector loadings. Nothing's exact, so you've just got to use them to explore 'what if' scenarios.

Sorry this ran sooooo long.



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Jeff Chambers
T/S #3
11.86 Seconds/113.8 MPH
Chambers Racing Team

Hey Jeff. Actually thanks for that explanation, i'm always up to learning more. I just figured that if you mess with the heat range of the spark plug with a high voltage ignition (or even the stock one) and you gap the plugs farther for more spark travel, it increases the resistance and increases the operating heat of the plug very high. I also thought this would contribute to preignition and combustion chamber heat would go up enough to melt the plug. I had just "heard" that high voltage ignitions are more prone to melting plugs, but i've never personally experienced this myself, so what do i know. Just thought i'd let you know my train of thinking. If you have any other things you know, please share, the more i know, the faster my stang will go

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'84 Mustang 5.0 T5, FMS aluminum radiator & 180* thermostat, 1 5/8 shortys/2.5" duals, '88 GT tail lights and wheels, Holley 4160 4 BBL, smog pump idler, more coming soon

[93CobraR]

Theres no way he needs yo bump up his injectors to 30's. He deffanitly has plenty of flow untill he has nitrous or a blower. Hell, he could probably get by on 19's if he wanted too. I'm running 19's with heads and a cam and they run just right. Don't waste your money.

------------------
87 GT, 4 inch cowl hood,17x9 Cobra R's/255/45's,GT-40 heads,long tubes headers,h-pipe,Flows,BBK cold air, Mass air,70mm MAF, 1.7's, 1" spacer,underdrive pulleys,Pro 5.0, King Cobra, Adj. fuel Reg., Lakewood Lift Bars,50/50's,subframes, 4.10's.
Best time 12.96
Best MPH 103.42
Best 60' 1.695

Visit my site at:
http://www.geocities.com/cobrar93_2000/MyPage.html

Like I said CobraR, every combination is different. The name of the game is experimentation; its the only way to learn. For his combo 19# definitely is out of the question and the 24# are probably stretched. If it takes 55psi of fuel pressure to max out the EGT in his combination (just for argument's sake) then I'd say he'd need to step up to 30#. If he can do it at 44psi fuel then he's OK. That's why I suggested borrowing a set of 30# and the MAF if he can manage.

Just as a suggestion, you might want to try 24# yourself. I'd say your MPH is a little low for your combination. If you could try 24# you might be able to pick up a bit. For comparison, with my GT-40 irons, E-cam and shorty headers I ran 12.50's all day at 107+ weighing in at more than 3300#. You ET isn't really that far off, but the MPH is showing that you're down a little on top end HP. The 1" space might account for some of it too though but I think I'd try some larger injectors.

Just some 'been there, done that'.



------------------
Jeff Chambers
T/S #3
11.86 Seconds/113.8 MPH
Chambers Racing Team

jchambers:

What about my car? It seems to be real lean. How do you feel about air/fuel guages? I have one and I tuned my car using that guage and picked up one mph and some power. My psi was 52 at idle (air fuel guage was 1 bar into rich). I ran my timing at 16 degrees. My car is a full body weight GT (had half tank of gas, subwoofer w/box, sway bars still connected and still have stock suspension, see sig for time).

What do you think I should run? I weigh 210lbs. I don't mean to put you on the spot, but I know you have experience with a combo similar to mine. What do you think of the F-303 cam. I have my plugs gapped at the factory setting of 44 (is that right). I also have MSD.

Thanks,

Jason

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88GT stock shortblock, GT-40 iron heads, Edlebrock Performer intake, 24# inj, Pro-M 75mm Bullet MAM, 3.73, hurst short throw, F-303, electric fan, alum rad, FMS HD clutch, R134a ac conversion, 70mm TB , and some other stuff I probably forgot, 13.02@106 with a 1.87 60ft

[Jeff Chambers]

Stock gap was about .050-.054", at least on 90-93. You're MPH is closer to what I'd expect, but your ET is slow. Part of that is in the 60' and the weight of the car. You're probably weighing in at more than 3450# so you can go to the calculators and figure your HP. The Performer intake breaths real well, better than the FRPP intakes, especially above 6000. I don't see any exhaust mods though. In all truth, the F cam is too much lift for what you're doing. Everyone seems to be hell-bent on the off-the-shelf cams when the custom grinds are where its at. For these motors, lift isn't everything, especially for the GT-40 and GT-40P heads. You're better off settling for lesser lift (maybe .512 max) and working the duration, CL and split figures to keep the runner velocities up and the engine breathing evenly. You car appears to be a daily driver, but if you really want to see that ET drop I'd concentrate on trying to get some weight out of it. Next time you're at the track weigh the car in so you know where you're starting.

------------------
Jeff Chambers
Trophy Stock #3
11.86 Seconds / 113.8 MPH
Chambers Racing Team

[LX XLR8R]

thankx for all the info jeff..im going to try out 2 heat ranges colder than stock now..but about the gap..if i can run the gap at .6 without fouling then should i???i mean if i can get more spark without it blowing out(plugs look better than new)..when i talked to accel thay said i could open the plugs up .05-.1 bigger..i guess the only thing to do is to stop asking you cuz you dont have my car infront of you and do some T&T on mine..thanks for the help

------------------
1987 black notch(ex 4 banger)
DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one..
AIM=onesillynotch

I have 2.5" exhaust, flowmasters, h-pipe, 1 5/8" headers (equal length shortys). I chose the F cam because I got it cheap, I watched the break in and pulled it out and got it for $90 bucks. I also have an E cam that I got for like $60 from my cousin, similar deal I watched it break in and then pulled it out. So you think I should gap my plugs at .50-.54? I know that every car is different, and I know how to read plugs, so I guess it is trial and error at the track huh.

I put the F cam in because I liked the way it sounded and it was a little more aggresive because I planned on better heads in the future. I have Edlebrock Performer RPM (1.90 intake 1.60 exhaust) heads now and will put them on in the summer (June). My heads (the GT-40's) are matched to the intake and gasket matched. They have been opened up a little to clean them up. I also had the heads shaved .030".

Yeah my car is a daily driver, that is why it still has air. I felt the car was too nice to turn into a race car. I have a 4 cyl notch lined up for that.

Thanks for your help, I really appreciate it.

Jason

[93CobraR]

Originally posted by jchambers:
Just as a suggestion, you might want to try 24# yourself. I'd say your MPH is a little low for your combination. If you could try 24# you might be able to pick up a bit. For comparison, with my GT-40 irons, E-cam and shorty headers I ran 12.50's all day at 107+ weighing in at more than 3300#. You ET isn't really that far off, but the MPH is showing that you're down a little on top end HP. The 1" space might account for some of it too though but I think I'd try some larger injectors.

Just some 'been there, done that'.

I have more then enough fuel now. My pressure is only at 40, and my et drop with a increase in pressure. My car is damn fast for what I have done, it a full weighted car, with just Gt-40 heads, and stock cam, stock intake, stock bottom end with 128k on it. Try taking a car and doing that and running a 12 with it. That is a great mph for the mods. Once I put my cam and intake on it should be done in the low 12's. Just a thought to give you more info on my combo.


------------------
87 GT, 4 inch cowl hood,17x9 Cobra R's/255/45's,GT-40 heads,long tubes headers,h-pipe,Flows,BBK cold air, Mass air,70mm MAF, 1.7's, 1" spacer,underdrive pulleys,Pro 5.0, King Cobra, Adj. fuel Reg., Lakewood Lift Bars,50/50's,subframes, 4.10's.
Best time 12.96
Best MPH 103.42
Best 60' 1.695

Visit my site at:
http://www.geocities.com/cobrar93_2000/MyPage.html

[Moxie]

I love this thread. I love this board. It's nice to see guys like Jeff taking time to help others along. Mr. Chambers, have a cookie.

Somebody mentioned running plugs 2 ranges colder than stock. Personally, I recommend against it. I have found it is hard to get accurate plug readings with plugs that cold. I recommend staying with one range colder than stock. Like I said, this is based on personal preference. Of course, I sell and install nitrous systems, so most of my experience with plugs is on the bottle. If you guys have different experiences, sound off. I always like to learn new stuff.

As for injectors, here is the rule of thumb I learned from a guy at Siemens, an OE supplier of injectors.

lb/hr (fuel) = (Max. HP x BFSC) / (# of injectors)

Max. HP is a realistic estimate or a known value from dyno testing

BSFC is Brake Specific Fuel Consumption. Typically, BSFC for a normally aspirated or nitrous engine will be 0.45. For a turbocharged or supercharged application, use BSFC=0.55. Dyno testing can provide exact BSFC data. For a safety margin, you can use .5 for n/a engines, and .6 for supercharged/turbo combos.

# of injectors should be one per cylinder, if possible. For some applications, additional injectors are utilized.

Once a value (lb/hr) is obtained, use the closest injector size above that value.

Example: 302 c.i. Ford 8 cylinder, naturally aspirated, 350 horsepower:

lb/hr (fuel) = (350 x .45) / 8

lb/hr (fuel) = 19.6875

This engine has exceeded 19 lb/hr, so it's time to use 24 lb/hr injectors.

You can insert injector rates into the equation, and solve for max. HP level of a given injector:

19 lb/hr= (Max. HP x .45)/8

152= Max. HP x .45

337.78= Max. HP



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Moxie Racing

The Nitrous Oxide Information Site

[LX XLR8R]

i would asume that is crank HP correct???

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1987 black notch(ex 4 banger)
DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one..
AIM=onesillynotch

[Moxie]

correct.

------------------
Moxie Racing

The Nitrous Oxide Information Site

[Jeff Chambers]

Alright Moxie!

Actually, my motor would be about perfect with 27# injectors, both mathematically and out on the strip. My plugs will show good color at reasonable fuel pressure settings at the big end of the track, but cruising around in the pits or around town and its pig-rich. The 30# are just a tad too much but the 24# aren't enough. I can't say enough though that EVERY CAR IS DIFFERENT. For example, the guy that just won the Spring Break Shootout in Trophy Stock was running 11.50's at 118MPH on 24# injectors. He has to crank the fuel pressure up to 55psi to do it though. Could he run the same times on 30# injectors? You bet. It may take him a little while to figure out the tune, but he should be able to do it and at a more reasonable fuel pressure setting.

CobraR, your times are great for no more than you've done to the car. But I'll still hold that your ET and MPH don't match as well as they could. Now it could be due to traction (although that usually shows up as higher MPH), shifting, headwinds or any of another million factors, but it could also be due to fuel starvation. Look at your time slip and see what's happening after the 1/8th mile marker. If the car's falling off on the top end, I'd look at fuel or air...or both. Not trying to piss ya off, just trying to be helpful.

------------------
Jeff Chambers
Trophy Stock #3
11.86 Seconds / 113.8 MPH
Chambers Racing Team

[Jeff Chambers]

Also let me add a point to Moxie's calculations. You never want to push the injectors to 100% of their capability...it just not efficient. It'd be like using a 75ft-lb torque wrench to tighten your head bolts to 75ft-lbs; at full scale the accuracy and sensitivity just isn't there. If you run the calcs and it says you're at 18.2lb/hr, I'd still upgrade. The injectors vary, the BSFC is a guess to begin with, and there's a ton more variables that could push you over the edge. If the calcs are within 15% or 20% of peak, I'd upgrade.

------------------
Jeff Chambers
Trophy Stock #3
11.86 Seconds / 113.8 MPH
Chambers Racing Team