Tuning/MPH Help

KB526, blown alky, Promag 44, 1471HH 23% over, Bruno/Lenco 3 sp. We run Outlaw 10.5, 1/8th mile. We made five runs last weekend, and we kept leaning the air/fuel ratio a tenth at a time. We never seen our mph go up. It stayed from 146-148. We brought in an electric high speed that turned on 2 sec after launch, and was on the rest of the run, w/ a .060 jet. Our last run was our leanest, but egts never got above 1000 degrees, in fact I don't recall them going up much at all. MPH never changed. Is this showing we're not really increasing our horsepower yet? Or is our hi-speed jet too small to make a real difference?

Since I know someone will ask, I don't know for SURE if my hi-speed is working. It's a nitrous fuel solenoid, and it turns on and flows great w/ 100+lbs of air pressure. But besides all that, shouldn't our mph go up by leaning the whole system?

Josh

 

Data

Apparently you have a data recorder on the car? When you speak of leaning the air/fuel ratio a tenth at time how is it measured with your system? What do the spark plugs look like? What are the ETs doing while all this is going on? Also what was the weather doing while you were leaning the motor. If the density altitude is going up dramatically maybe your leaning the motor is just keeping it where it was? I measure air/fuel ratio by dividing fuel flow measured by the flow meter with the boost measured by the boost meter. Dave Germain

 

mph

Josh, I know your messing with the timing and running it soft. We saw 10 mph gains at KID with a 1 degree timing increase accross the map. We run rich,so it's bringing in the a/f at the same time. Around 1000 deg egt our plugs look new after a pass. That's too rich to go fast.

Mike

 

We do have a data logger. Spark plugs look new, maybe a little cad burned off the ground strap. I made a program that figures DA and density of the air, etc. It "estimates" the amount of air going in and it shows me how much fuel to put in the motor to get what air fuel ratio I want. My a/f ratio's probably aren't spot on, but they're more of a "tuning modifier" that can be adjusted. The DA was around 2900-3900' of air. Sometimes we would lean it just by keeping the same jet due to the DA going down at nigh. Our ET was anywhere from 4.94-5.15, but seemed to be relative to how it 60'. Best 60' was 1.15, but was usually in the 1.20's which is way off for our class.

 

Just a wild guess here, but I'd say you are way fat still. With that kind of 60' and MPH I would expect better 1/8ths than 5.1s

Just curious, whats your car weigh?

 

Mike B-We are running soft at the hit....9* total timing ramping to 25* over 2 seconds....ran a 4.95 w/ 1.15 60' like that. Next night ran 4.94 ramping from 9 to 27 over 1.5 seconds w/ only a 1.23 60'.

Mike C-We are running a 4.30 gear w/ a 1.80 first gear on a bruno/lenco 3 speed. I know a lot of guys run a 2 speed and taller rear gear. And that makes sense what you said because our boost is fairly low on the latter half of the run. If we run 8000rpm we'll get around 30lbls....but since we shift at 7500 (trying to be conservative for now) we're only getting 24-26lbs on the big end. We're only at 23% over, we thought about bring that up to maybe 28-30%.

I've always called it a high speed, but yeah i'm just talking about the port check. There's no spring or plug, just a pill. I thought blown cars like to get rich going down the track due to heat from the blower, thus richening the a/f ratio...so i put this ck valve in to lean it to a higher a/f ration to see what it'd do.

 

2900lbs and nose heavy. In fact, we've yet to get on the wheelie bar hard.

This was only a 5.42 pass due to leaving at only 3500. Figured out our 2 step problem...the rev limit wire came unplugged at the digital 7 box.
http://www.youtube.com/watch?v=7HdOJ9BVGoQ

 

All good comments, I agree with the rear end gear selection though, go as high as you can to keep the motor free and happy. Another thing that really makes a big difference is tire size. If you are running a 36 inch tall tire, it is too big, it won't allow the motor to free up in the mid range; you'll be amazed how much harder the car will pull with a 34.5 tire. Also, shift rpm is very important, raise that up if you can.

 

We're running a 33" tall tire.

I have a guy that runs our class that thinks my fuel vent is too small. I don't think it is due to all the research before making it. I believe we have a -16 feeding the pump, and a -08 vent w/ 3 returns going into the tank. Is this enough?

Josh

 

Josh....i think that should work for a vent, with the amount of fuel you are running through the motor.
Darren

 

Needs at least a one inch vent or if possible the same size vent as the fuel outlet.

 

How would you know your vent is too small? I would think w/ a mechancal fuel pump, it's going to take the fuel it wants anyways?

 

I read on here a good description of how to check it on an old post, some dude from Texas....... Fill it with water and turn it over and let it run out of the outlet with only gravity pulling, it should flow freely. Or has he put it so well,,,, the old Texas glug test...if it glug glugs the vent is too small.

 

i have a number 8 vent and it works fine 542 hemi 1471 littlefield 57 over i dont think a bigger vent is nessasary with you application and my heep runs 3.90s and .95 60s so an 8 vent will work fine

 

Man 57 over! thats gotta be close to the end, I thought my 45 over K8 14-71 was close to max its making 45 lbs what is your making at that speed!

 

I suspect your not gonna get there with a digital 7. Buy a MSD8plus or a 10 plus. This is why your not seeing any gains. What kind of plug gap do you run?

 

Several big name tuners have said 1900hp is the absolute limit for a digi 7, and that's on gas. - Great box though, many small tire guys are running it piggy-backed to a mag, thus the power of the mag and the control of the digi 7.

 

We're running .015" plug gap. We run the Promag 44 w/ our Digital 7. Never heard of there being a hp limit w/ the digital 7. From what i've read on here the 8973 Promag controller is the same software, both just have different features.

 

all i can go by is my boost gauge in good air it will make 48lbs 3000ft and above not as much