Kubs

Ok, let me see if I am understanding this correctly. The VATS metrics can be written out. In order to have the ECM think it is getting the fuel enable input, I have to take the R6 wire from the ECM and connect to ground (the purpose of the jumper at the starter relay?). After doing so the ECM will tell the injectors to fire and I can remove everything else. The pictures posted earlier of the two CCM connectors show nothing about controlling the fuel pump, but I will be wiring the fuel pump, and starter on their own circuits anyway with toggle switches and the proper fuses. Am I on the right track with my thinking? I shouldnt need any of the starter or fuel pump relays then if they are wired to switches.

Also, does what is the GD3 wire on the CCM? Does that stand for the D3 pin in the "Gray" connector? The pictures show it as not used.


Would it be Pass Key Return on this one?

mseven

yes, vats would be out. I think at r6 the lack of that ground interrupt would act as an open circuit in that location if the ccm is disconnected /removed. If I remember right in the thread/link posted by Rod, aside from using a regulator one of those guys used a momentary switch in that location...that would need to be double checked.
The ccm input to fuel enable (start only)input is shown in the 90 FSM as function of the ECM and then outputed at B7. The CCM's gd3 goes to the ecm at r6 then through the ECM to crank fuel input and fuel pump enable. It then outputs the ECM through B7 to the fuel pump relay (during start only, and tied in with ign. in the ecm).
I would think wiring everything separate with relays/switches will control start and fuel. Because I have never tried this before, part of my concerns would be the open circuits involved, and the effect that might have....I believe there may be some trial and error involved.

mseven

I don't see those in my fsm 8a, what page/s are the diagrams you posted? According to mine,it should be a natural conn. and a gray conn.

According to fsm it is supposed to be a dk blue wire/ckt 229...Gray D 3...I don't see that or ckt 229 in those connector diagrams. Have you physically inspected the connector to confirm?

Kubs

If I have to I can include the output signal from the ECM, through the relay, in my fuel pump circuit. The starter will be a momentary switch, the fuel pump will be an on/off toggle.

I have not looked at the connector, and I dont know what those pictures are from, they were posted earlier in this thread. I do not have a FSM so thats why Im a little lost here, and asking lots of questions. Would you be able to make copies of the fuel wiring diagrams for me?

mseven

yes and yes.... I'll make some scans of my 90 fsm here in a little bit....pm me your email it'll make it easier to ship files over to you.

Kubs

PM sent. Also, I will be able to check the connectors on the car this evening and report back.

mseven

email w/all attached scan/files sent

Sandpiper59

Just to make a point, there is additional instructions in the Datamaster software for "people that have removed the CCM for racing"..

Sometimes too many answers can cloud the issue, clearly it is not at all uncommon to remove it in a race only car.

tpi 421 vette

I would just leave the ccm on the car. What are you getting rid of a half ounce of weight? I think you will have more problems than it's worth getting rid of it, and really gaining nothing.

I still have the ccm on my car, and I am concerned about weight, and have taken alot of things out that aren't needed for drag racing. But I don't see much benefit deleting the ccm. Unless you want to start from scratch with a painless wiring harness.

ddahlgren

Why just go after market efi and rip all the wiring out other than what is really needed for starter brake lights etc.. With the money saved from paying people to burn chips to make it just start then later do a tune up you could just do it yourself. You also do not need and other software to log or anything else.
Dave

rodj

Even cheaper if you keep going ripping things out.
Leave the pink hot wire to the coil and put a carb on it

kimmer

This is really informative, can't wait to see your car when it's finished Kubs.

Kubs

Its not so much the weight as it is just trying to simplify the car. Im not using anything the ccm controls because its all gone and I don't want a bunch of exposed plugs just along for the ride.

I cannot go aftermarket efi in my class because I have no points left for it (NASA classing system).

I think I got it figured out. I will post pics of my diagrams in the next couple days. Ill keep you all posted.

Kubs

Using this FSM image, among others, from mseven, I figured out how to make this work (I think).

This is from the FSM:


Here is my wonderfully altered pic :


By running a wire directly from the toggle switch to the fuse box, I can make the fuel pump turn on when ever I want. No fuel enable, no oil pressure switch (I may add my own version of it later), no relays. It just runs when I turn it on.

Then I would need to make one of these guys I found in another thread here:
http://forums.corvetteforum.com/c4-t...or-bypass.html

Or I could buy one of these:
http://www.bakerelectronix.com/products_vats/

This allows the ECM to fire the injectors when needed. I will also have to add in a voltage regulator between this box and the ECM because this circuit outputs a square sin wave of 12v, and the ECM is expecting a 5v signal. The regulator will turn the 12v input into a 5v output. That box can go anywhere on the car as long as it is wired into the R6 ECM port.

Lastly, since I am using a momentary switch for the starter I dont have to worry about the start enable relay. I simply run power from the battery. to the switch, to the starter and the car will start.

Someone correct me if I am wrong but I dont think it has to be much more complicated than that.

ddahlgren

I think before I added another box that could fail I would spend the money to do the Vats disable in the ECM. Did not know about the points thing for your sactioning body. My experiece racing is in pretty much anything goes sort of racing where EFI is EFI and no one cares whose it is.. If you disable VATS in the ECM and bypass the start enable relay you should not need any other device to trick the ECM. Personally I would have the ECM run the fuel pump I think it does have a circuit for that so if the engine stalls due to an off road excusion and makes you disoriented or worse unconcious the risk of fire is cut way down. Just some random thoughts that I hope might be useful. I am with you when it comes to race cars my motto is simplify then add lightness..LOL
Dave And yes every pound removed below minimum weight is a pound you can add back in where it becomes useful rather than cargo.

Kubs

Well mseven says he can write out the VATS from the ECM but that wont allow the injectors to fire, I still need a fuel enable signal. Also I am going to try to use the oil pressure sender to power the fuel pump in my circuit once the engine has oil pressure.

mseven

Sounds good, it looks like you have a plan. It looks like that class business you guys are doing forces a completely different direction than I would take if just changing the car over to a more simplified system. Do you need to install a power cut off at the back of the car ?

Kubs

The thing is, each mod you do cost a certain amount of points. If you have too many points you get bumped to another class. One can use a different computer system if thy take points for it, but for me I felt my points were better spent on suspension engine and weight reduction. Doing the computer and wiring this way is more of a headache but it doesn't cost any points.

And I will need a cutoff switch in the near future so im going to put one in when I do the wiring changes.

ddahlgren

Hmm I had thought the VATS disable removed the requirement for the fuel enable signal but I guess must be wrong. I was thinking of doing that with my 91 to eliminate any possible Vats problem along with bypassing the stater enable relay. My test was going to have an ignition key cut that has no pellet for VATS. It might make a good first experiment for chip burning. My thought is anyone wanting to steal the car will it is pretty hard to come up with an anti theft system to counter a flatbed and chain the fastest way to grab and leave. If your choices are suspension or aftermarket ECM going with suspension a smart move I think. Every mph in a corner is one you do not have to add on corner exit. At the end of the day sports car racing is a large exercise in conservation of momentum. The best brakes are the ones you don't use very often..lol..

Kubs

Since I can't start my car with the engine out, im going to test everything with a light bulb as I go along. That key idea would be nice.