1970 GTO Version 2.0

[Rybar]

Andrew, I just stumbled on this awesome thread. Very informative. I just went through it today. My brother has an L92 in his Escalade and the the thing moves for its size. Keep us posted!

[andrewb70]

Wow Andrew - your getting close! Nice work by the way. This thread has been very informative. You seem very methodical with the steps of the installation. I tend to get ahead of myself too much. You've gotten a lot done in a short period of time without take shortcuts - it just goes to prove that if it's done right the first time you'll save time in the long-run.

Will we be seeing the Goat at RTH?

Thanks for the kind words. It really helps that I am ver, very familiar with my car. Having done most of the work on it myself, I know exactly what was done in the past. It also helps that I have done two LSx swaps into RX7s. While the cars are obviously different many of the issues that go with swapping the engine are very similar.

My goal is to have the car fully sorted out and ready for RTTH IV.

Andrew

[Code Red]

awesome

[Motown 454]

Hi Andrew nice build I like those Ls engines. If I didn't have my engine already I would be putting one in my car. Keep the updates comming very interesting.
Wayne

[andrewb70]

I spent all day in the garage today, but I am afraid that there wasn't really anything new to show you guys. I did a lot more of "connecting the dots." I found the wire under the dash that went back to the relay for my fuel pump. This was used by the Commander 950 to turn on the pump. The GMPP harness already had a relay for the fuel pump, but I really like taking power directly from the battery to run the fuel pump. So after consulting with a couple of folks I decided to just run two relays. The relay in the harness activates the relay in the back of the car. After hooking everything up it worked perfectly. When the ignition key is in the "Run" position the pump primes for about 5 seconds and then shuts off.

Since I got all of the coolant hoses hooked up, I went ahead and filled the system. I filled the radiator. Then I filled the block through the upper radiator hose. I fired it up and ran the engine for a while. The O2 sensors are not hooked up and as it warmed up, and went into closed loop, it started idling a little rough, but it did not die. So I let it idle and warm up a bit. The stock thermostat is probably around 205 and the ECU turns on the fans at 212. The lower radiator hose stayed relatively cool until the thermostat opened. Once that happened, I just topped off the radiator and hopefully that will do it. The fans kicked on at around 212 as they were supposed to. Nice thing about the GTO is that I already had a giant Be Cool radiator. I never had any issues with the 502 and I am sure it will cool this engine just fine. The RX7 had half the radiator, and almost no grill, and I didn't have any issues.

Now I need a little help from everyone. The GMPP harness instruction say that the tach signal is a low voltage 2 pulse square wave. It also said that some older tachs may require a pull up resistor in order to function properly. I hooked up the wire from the tack and sure enough it did not work. So, what the heck is a pull up resistor and how do I hook it up?

I am trying really hard to resist project "scope creep." So with some luck this thing will move under its own power next weekend. LS swap in less than 2 months, not bad, if I do say so myself.

Andrew

[wiedemab]

I'm not an Electrical engineer, but I did some Googling and found these links. The first one makes it seem pretty easy in theory.

http://www.seattlerobotics.org/encod...97/basics.html

http://en.wikipedia.org/wiki/Pull-up_resistor

I guess the purpose is to limit the current through the circuit. One site says that the most common sizes for logic circuits are 10K ohm or 47K ohm.

It looks like the resistor just goes in the tach signal line??????????

Good Luck - I'm looking forward to learning something here. If you don't figure anything by the first of the week - I'll be seeing a buddy of mine who is an EE on Monday, so I can ask him.

Keep up the good work!

[Bow Tie 67]

Andrew,

You may have already solved this issue but here goes anyway.

http://ls1tech.com/forums/showthread...sistor+up+pull

Matt

[andrewb70]

Matt,

Thank you! I searched over there but wasn't coming up with anything.

Andrew

[andrewb70]

Andrew,

You may have already solved this issue but here goes anyway.

http://ls1tech.com/forums/showthread...sistor+up+pull

Matt

So today I did as the thread above indicated. I installed a 1K Ohm resistor between a switched power source and the tach signal wire:



The tach worked, but the needle was kind of jumpy below 1000 RPM. Any electronics experts have a suggestion?

Andrew

[wiedemab]

I thought I read somewhere that if it was still jumpy at low RPM to go to a bigger resistor, but I wouldn't swear to it.

[parsonsj]

Me too. See if you can get a 10K resistor and give that a try.

jp

[Bow Tie 67]

So today I did as the thread above indicated. I installed a 1K Ohm resistor between a switched power source and the tach signal wire:

The tach worked, but the needle was kind of jumpy below 1000 RPM. Any electronics experts have a suggestion?

Andrew

Up the resistance somewhat, say 1200 ohms ( just a guess ), this will shave off some of the " pull up " amperage which is making it sensitive at low rpm. Basically this circuit is adding voltage ( making it a 12v signal ) to the " low voltage 2 pulse square wave " so the tach can use it.

Ohm's law I ( amps ) = V ( volts ) x R ( resistance )

We have a constant 12v source adjust ( R ) to adjust ( I )

10K maybe to large although resistors are cheap its your call, going up in resistance is a safe direction.

[andrewb70]

Thanks for the advice guys. You are being way more helpful than Autometer was just a few minutes ago. Basically they told me that they have been unsuccessful in making their tachometers work with the low voltage signal that comes off late model ECU output wires. Their suggestion was to purchase the 9117 box that taps directly into the coil harness and converts the signal (whatever that means) to a square wave that can be read by the tach. My initial reaction is that this is BS , to get me to buy an $80 dollar box that costs them 5 bucks (at most) to make. I am going back to Radio Shack for a collection of 99 cent resistors.

This brings up another point. Why couldn't the GM engineer who worked on the GMPP harness pick up the phone and dial up Autometer, VDO, and Stewart Warner? Between those 3 brands I bet you will cover 95% of the aftermarket gauge market. It would have been a 15 minute discussion to determine what these tachometers need in order to function properly. The information could have been easily outline in the harness instructions. Instead, they put this in the documentation of the harness:

"Note the signal is a low voltage square wave, some older style of tachometers may need a pull-up resistor in order to read the signal -- this detail is left to the user"

WTF?!?!?!

Andrew

[wiedemab]

I see a product in here. Lets buy a tach from all of the major gauge players and figure out what resistor works for each, make a little plug in resistor circuit and sell it!

Who's on board? Not sure the market is big enough and the price would be pretty low for such a product, but we'd be helping people

Later

[parsonsj]

I want to get my old Holley Commander and an MSD ignition box and see if the need for a pull-up resistor was what kept those two boxes from working together!

jp

[trapin]

Well I don't get it. There are many Gen III conversions out there and I have to think some have Autometer Gauges. What did they do to get it to work?

[wiedemab]

, to get me to buy an $80 dollar box that costs them 5 bucks (at most) to make.

They may have bought the $80 Box, I'm not sure. I'm far from being educated in LS swaps.

[Rubes]

Ohm's law I ( amps ) = V ( volts ) x R ( resistance )

I'm glad I'm flying on United next week...LOL

ohms law = voltage/current x resistance
so current =voltage DIVIDED BY resistance (not multiplied)

other than that your comments are correct.

[Bow Tie 67]

Oops, its a good thing the aircraft have redundant systems. *** sound of air-raid siren ***

[wiedemab]

Good catch Rubes. I didn't even pay any attention.