well it has bin 5 days what news if any do you have to share with us .

 

The Jacobs Accuvolt unit is now installed. The good news - it delivers a constant 14.1 volts to the car. Tied into the unit are the Haltech ECU and the two fuel pumps, the two components deemed most critical to the operations of the car under boost. Other devices will be added if they don't throw the overall AMPs over 100 (the max supported by the Jacobs unit). Possibly one or a combination of the Aquamist water injection system, the coils, and the injectors. The bad news - the Haltech unit still reads 12.8 volts under boost.

How can this be as the ECU's power is tied directly into the Jacobs unit and it has been tested and verified to supply 14.1 volts? I spoke with Steve on Friday and Gotham had just tested the voltage again. [Pardon if I am recalling this wrong, I'm no electrical guy and this is what I think Steve told me] They verified, when using the ground from the battery, the voltage coming across the Haltech power line is 14.1 volts. Yet, when using the Haltech ground, the voltage tests out at 12.8 volts, indicating the Haltech unit is not properly grounded.

So, either the unit is not properly installed or a problem exists somewhere on the ground the unit is tied into. Where I left the conversation on Friday is Gotham was going to go back to their wiring of the Haltech to ensure its correct and properly grounded. If this passes, they'll then need to find out why the ground they've tapped into (I believe the engine harness) is not correct.

Closer to a solution? Yes. Unfortunately not fixed though

 

sometimes do you wish you would have just hung it up and gone with the 911TT?

just kidding, you are an incredibly patient man, David

 

911TT? No. Aston Martin AMV8? Yes

Hopefully Gotham will trace the grounding issue quickly. What concerns me is they've already beefed up the grounds on the car. So it would be better if they find out the Haltech unit is installed incorrectly. If not, they'll have the fun task of tracing why the engine harness does not ground correctly. The harness was replaced with a new one when the car was at Pettit Racing. Maybe they did something wrong to install it?

 

The first test that they conducted effectively isolated the Haltech unit from battery because by utilizing the battery ground you created a short circuit before the device. The second test using the Haltech ground was the only of the two that actually tested the Haltech unit. Having zero experience with the internals of the unit I am going to have to guess, but it seems a pretty safe bet that the unit utilizes both buffer and transformers to protect components and to step down the voltage to a usable level. Most chips operate off around a .5v logic level give or take. Given the analog nature of automotive sensors it seems plausible that the ECU utilizes a combination of digital and analog signal processing. With that being said it seems unlikely that the 12.8, 14 or whetever input voltage is utilized for analog operations. This voltage is most likely stepped down immediately before being buffered and distributed. As as you probably know, testing a direct ground is different than testing voltage that is actually supplying transformed/buffered circuitry. From my experiences in avionics I would not expect to read the same on the two tests that you made, though like I said, I squat about Haltech ECUs. Before you guys go crazy trying to chase this problem I would verify that you in fact do have a problem by giving Haltech a ring and verifying the operational parameters of the box.

good luck man

 

Not knowing squat about this, Gotham did indeed call Haltech about this. They were the ones that first believed the unit was not properly grounded and that was the reason the Haltech was only producing 12.8 volts. At first Gotham did not believe this, but after testing, they know concur.

Hopefully this will all be resolved soon and the car will be finalized with an awesome Steve Kan tune.

 

I'm sure they'll figure it out.

 

Having some voltage problems myself....

 

What kind? Similar to what I'm experiencing? What ECU are you running?

 

hi david, are you using the stock rx7 transmission unmodified? and any traction control system?

 

nice user name

 

I like your also

 

Stock tranny with Pettit launch kit. Will look into a traction control kit once the car gets back home.

 

some folks on this forum are looking into racelogic unit for our 20b

just look for traction control 20b or something like that..

i think it's worth a read when you get a chance.

 

btw, here's the direct link.

https://www.rx7club.com/showthread.p...on+control+20b

 

My buddy Dean here in Jax has the racelogic unit on his 13b and it works great. This is one of those "next steps" for me after i get the car back.

 

Hello David

I think u should ask gotham to try and ground the cable to the chassi. Ive had problems with grounding the ECU to the engine harness for some reason.

Im only running ground to the chassi now. And i will get a +14v when i do that. I did see a voltage similar to yours when i had it grounded to the engine harness.

So have them try to put the ground to the chassi, and the problem might go away.

BDW what kind of alternator are u using now? I need a new one, since my volt has dropped to about 13.7-13.8v at full woot.

Oh and your setup is awsome, seen it when it was still in pieces at gotham.

Regards
JT

 

Thanks for the comments JT. The alternator is a 300 AMP GM unit. You'd need to contact Gotham as to the particulars on the unit.

It will be great to get the car back and drive it. Speaking of that, the voltage problem has been found and corrected. I'll let Steve post here with the actual way it was fixed, but as I understand it, Gotham ran thicker power wires to the Haltech and this corrected the issue. No more voltage drop!

Steve tuned the car last night at 10 PSI, and on the Mustang Dyno, it made 430ish WHP. I know the Mustang reads lower but I don't know what the conversion is to a "normal" dyno. They need to fix a starter/ignition issue and then will get back to finalize the tuning, maybe even by today. Steve is going to tune the car to the maximum boost he can before he sees ignition breakup. I'd be happy with 14 -16 lbs. though and he should be easily able to do this.

So, I've made the turn and am now headed for the home stretch. A few other odd and ends need to be finalized but I should be driving the FD very soon

 

David

I'm excited for you!!! Seems like forever since meeting you and seeing the car at Pettit!

Can't wait for the final numbers!

Doug

 

Thanks Doug. Did you know that was about 2 years ago? Time flies when you are spending money

 

so is a south carolina pickup gonna happen?

 

That's great to here David.

I hope the engine will ive up to your expectations.

JT

 

David... Can you post some pictures of your engine bay? I wanna see how tight the fit is with the single. Thanks

 

sorry david, couldnt resist!

gonzz, those are the only two i had of the engine, so maybe david has one from the other side so you can see the turbo better.

 

Where can I get one of those front covers? I mean the one with the gotham sticker. I'm not so much interested in the sticker as I am the piece. Looks like it may help with cooling, though not in David's case I guess.