Reason I'm asking is I've mentioned it before in a post somewhere about how I have my nitrous wired up, it's a on a RPM Activated Switch and I usually set it around 4800 to come on, I put my 2 Step at like 4300 so when I come off the brake it'll flash up and the nitrous will come on. Here is my question, how much tighter could I get them with out having to worry?

They can be off 2-300 rpm from what I've seen.

my msd 7600 pill actually started to break up somewhere between 7100 and 7200. so now i have 8000 in cause its bad for nitrous motors to hit rev limiters!!!so ive been told

I have a pack of 5 from MSD 7000-7200-7400-7600-7800. All of them start to limit 200rpm lower than the # says. I do not know if this is normal or not but all 5 do the same thing so maybe MSD plans this ???

Seems like I remember reading some where you can measure these with an ohmmeter and the value matches up with the RPM it clips at. Anyone tested them to see what they measure?

Funny you guys mention this..... I bought a 7al3 at the beginning of the year. After I hooked it all up I went throught all the rpm switches and put the test 3000 chip in it and went right to 3000 on all 4-5 rpms ports. When I went back and put all the correct chips in they all were about 200 rpms short. so i left all the chips in and went back through testing each with the 3000 chip again (but this time all the other chips I left in) and all rev, 2 step, 3 step, and rpm switch all would only go to 2800. Took all the chip back out and went through with the 3000 test chip again and all went to 3000. I called msd they gave some kind of excuse about the box needed to be adjusted????

You can test the resistance of all of the chips with a simple volt/ohm meter, just measure the resistance across the pins. You can google for all of the resistance values and the coresponding rpm, I think I used shiftnoid's website, after all they do sell a adjustable chip(for 45 bucks!). If the chips ohm out okay and you still have a problem, it is definately in the box. As far as whether or not msd has some sort of adjustment inside the box? Who knows. I had the same problem in y 7al and it seems like it is low about 200 rpm also, I used to just use a chip thats 200 rpm higher than I need, it seemed to work. Currently I have been playing aroung with a potentiometer(manually adjustable resistor) that I picked up from a local electronic surplus store, and I am using it in my own home made two step. Seems to work okay, you just have to unplug it and break out your meter to make any adjustments. Hell of alot cheaper than haveing to buy a bunch of chips, but I wouldn't have this problem if I got off my wallet and bought a digital 7 and a laptop.

mine is a 7AL3 also. I was sent back to them once already to fix other problems. They did not say anything about needing to adjust it then LOL

here the ohms for the msd chips

RPM Ohms RPM Ohms RPM Ohms
2000 1152 4500 3141 7000 5689
2100 1224 4600 3235 7100 5793
2200 1297 4700 3316 7200 5919
2300 1370 4800 3412 7300 6043
2400 1444 4900 3509 7400 6150
2500 1518 5000 3592 7500 6277
2600 1592 5100 3691 7600 6406
2700 1668 5200 3791 7700 6517
2800 1744 5300 3877 7800 6649
2900 1820 5400 3979 7900 6782
3000 1896 5500 4082 8000 6897
3100 1978 5600 4171 8100 7034
3200 2049 5700 4277 8200 7171
3300 2132 5800 4383 8300 7291
3400 2215 5900 4475 8400 7432
3500 2288 6000 4584 8500 7575
3600 2373 6100 4693 8600 7699
3700 2460 6200 4788 8700 7845
3800 2534 6300 4901 8800 7994
3900 2622 6400 5014 8900 8122
4000 2710 6500 5112 9000 8274
4100 2787 6600 5232 9100 8428
4200 2877 6700 5349 9200 8561
4300 2969 6800 5449 9300 8719
4400 3048 6900 5569 9400 8879


1º = 1000 ohms
2º = 2000 ohms
3º = 3000 ohms
4º = 4000 ohms
and so on

hope this helps everyone

Rob you mind if I post that info in the tech area for later reference?

no not at all john anytime i can help also if anything i have on my forum will help here feel free to use it or post it. your forum has been super helpfull to me with my project and many others so like i said what ever i can offer to help
thank you
rob

http://californiahorsepowerandperforman ... 7b4bbe7a64

Making an adjustable chip is easy. All you need is a potentiometer, some pin terminals and a few resistors. All can be had at Radio Shack. A 5K single turn pot works fine, use the chart to figure where you want your starting point and add a resistor of that value in series. For example, a 1K resistor in series with a 5K pot would go from just below 2000 RPM to around 7200 RPM. You can use a smaller value pot to gain sensitivity, but it will limit the range. I used to make them, mounted them in small project boxes and labeled them according to measured resistance, just be aware that the RPM's may not line up exactly and may require a little tweaking. I even made my own 2 steps, just add a double pole-double terminal relay and two potentiometers, one set for the high side range and one for the low side.

awesome idea

What are you comparing the chips to to check accuracy? I test every car that rolls out of my shop with an MSD tester...almost 100% of the time, the tach is wrong and the chips are dead on! I've seen tachs dead on at lower RPM's and get as much as 500 RPM off by 7500 and vise versa. Soooo....I will trust the chips long before the tach!

Very interesting reading.

I will have to copy those ohm readings as soon as I learn how to spell--

I would have never thought that they are all different. Mmmmm

Learn something new everyday.

And they said we're all cave man. HA!

Thanks guys..