I think you will find that your alternator is crapping out when it gets hot. I have gone through several alternators. I was averaging about 2 per season! I finally got a 140amp, which is hogging lots of power and my problems went away.

But they will as they heat up and they reach their end of life span start to fade with voltage output.

Again as mentioned, your fuel pump is directly connected to the alternator for power with these "hot wire" kits. I bet you see it fading. That would be the easiest fix.

From there I would change the fuel filter, then go to the tank if necessary.

WHen I had your car I did not see any fuel line problems that I recall. But it will not hurt to check it all out anyways.

Let me know what you find.....

 

Have you called the support line on this one? Are there rev limits per gear in your program? Have you tried a complete re-write? Maybe you picked up a bug.

I'm going to say that it doesn't sound like a fuel problem especially if you saw now change in AFR at that point. Also within a reasonable amount of pressure falling you should be able to more than make up for it with more pw in that area.. SO if you go back, multiply 5500rpm + by 1.08 the car shoudl be richer and the problem would seem less worse.

Fuel delievery is dependant on PSI and PW. Within a reasonable drop you should be able to make up for one on the other. If you where dropping 5+ psi I would start to worry.

 

I would check the voltage at the fuel pump or very near it. If there is a connection problem at the relay near the fuel pump feed circuit the problem will show up there. If he has a alternator problem I would suspect he would have other charging circuit related issues such as dim head lamps and battery issues, which he isn't complaining about. I would also pull the pump out of the tank and check the strainer, if the strainer is clogged it can cause the pump to cavitate and loose pressure on high demand. Just as a pluged post filter will do as well. If the voltage is a nominal 13.5v at the pump and if the strainers are good, I would dump the pump. There is no reason for a pump to drop to 30 psi at WOT.

Jerkyboy what is the firmware version of your DFI box? You may want to have it updated and checked by the DFI people. I had one box that had issues such as you are experiencing. The difference was that it was a turbo Porsche application where it would die or rather shut off just as it hits 18 PSI of boost. It was sent back to DFI a couple times and in the end it was fixed. I am not sure if its related to what you have, but the way it shut down sounds like what is happening to you as well. This was a 3.2 or 3.6 firmware version and it was about 10 months ago. Also have you doubled checked the connections at the DFI box itself? A loose harness connector there will cause all sorts of issues, and double check all the grounds as well. Make sure that there is less than 2 ohms of resistance from that ground point to the negative battery terminal.

 

Tom,

I think they are only seeing a 1-3 psi drop at wide open..

 

That doesn't sound like a fuel system problem???

RACE ON!!!

 

It's quicker watching grass grow than getting someone on the tech line from Accel. There's no rev limit per gear and am not sure how the computer would know what gear it's in. If there was a bug in the computer, it would happen all the time yet this seems worse with heat. The other day, I drove the car all day in the heat. At one point, I could barely get any acceleration with it cutting off. It's almost like the old vapor lock with carb'd cars. This a.m., it's 50* and for the first few miles, it would rev through 6500. Once I was on the road for awhile, it came back!

 

Guys from what I gathered from his writeup is that the car seems to run fine when its "cold" or on the first run. After it heats up, then the cutting out seems to start...this would suggest that something is getting heat soaked and not working as it should.

Alternators are very subject to this sorta behavior. And with the walbro pump being wired basically directly to the alternator and its output heavily dependant on voltage from the alternator - its likely this is the root of the problem.

Being that "heat" seems to be the common demoninator, and his problems stem back to months ago with other fuel related problems I am leaning towards the voltage is getting worse with time.

If I recall correctly walbro indicates that their pumps volume decreases in the rehlm of 18% with a 1.5volt decrease! That is a TON. Now couple that with a pressure loss and you have a real fuel volume problem.....hence the reason he was having problems before with stuff that is already proven out.

Or perhaps the pump itself is just getting tired, but I would suspect its voltage that is causing this problem...I just don't think the "heat" factor would apply to the pump as much as it would the alternator.

We'll have to see what he turns up.

I also think if it were settings/version related the heat variable would not be a factor and it would do it all the time.

 

Wow, didn't see that sentence in the maze of reading all the post..

You definately have a fuel problem. How much does this car put down at the wheels? No lines kinked? Fresh fuel filter? Logged voltage?

Voltage is a good point because as voltage drops so does spark which could explain the brick wall feeling your having.

 

Mr. Attitude, did you not see me say this in the same very post you quoted?
I was under the impression that he was having a 2-3 psi drop.

 

Put down 465rwhp if that's what you are asking?? I will monitor the Alt. How accurate are our volt gauges? Filter is not fresh so I'll try that too. Cheap stuff first. I have noticed that the dash flickers a bit while the turn signals are on...alt issue? C'mon guys no fighting. It's all good. Save me from jumping off the bridge!

 

Alvin,

No need to start taking things personally here. We are all trying to help the guy out, and you obviously did not understand what was going on before offering advice to the fix. It happens and I think CFI was just trying to point this out to you.

The main thing is that he finds the fix...the more sound and to the point ideas we throw him the quicker he will get to the root of the problem.

 

Dave,

What I would do it run a seperate wire out to the alternator, through window if need be and hook it onto the nut for the hot wire kit. connect it to the positive wire for the volt meter. Then do another to any ground point of your liking.

Turn the meter onto DC volts and drive the car. I would try to do the same testing you did before:

1 when its cold and see if you can see what the voltage is,

2. I would let the car idle and heat soak the alternator real good and try it again.

I can tell you that you should see nothing less than 13.5 volts on either test or the alternator is not doing its job. Also the DFI if I recall correctly specifies that it should have no less than 13.1 volts to operate effectively.

So if the alternator is crapping out intermittantly then the DFI might be cutting out also(still doesn't explain the fuel pressure drop - that is defintely pump related), and it might not be always the pump.

Either way you need to have GOOD strong voltage. especially in these cars! And that is the easiest way to monitor the voltage - don't trust the dash- its another unknown. Chances are the volt meter will be quicker to respond if the voltage is flickering or cutting out.

 

Thanks guys I have my work cut out for me and I will report back!

 

I did. I figured if you were going to dismiss it, why shouldn't I? I don't know what math yields: 40 - 30 = 2-3???

Mr. Attitude, huh? All I said was, "That doesn't sound like a fuel system problem???" Jerkyboy mentioned that fuel pressure drop in only his 3rd post. I could have said something rude, like you not paying attention to the subject and jumping into the middle trying to play "big shot", without even reading the whole post. But NO! I restrained myself. I didn't do that. Mr. Attitude! Indeed!

RACE ON!!!

 

Jerkyboy,
My thoughts exactly when I clicked on the help button.
It made me get a massive headache just by reading it!
That is why I ask TJwong to send me a similar file from accel.

Maybe you should do the same, it can't hurt.

Paul

 

Guys the tau table is not the problem here...and its purpose is for fine tuning of "the pump shot".

The table is a representation of the dynamics that happen in a manifold. I have to say this also, its more-so geared in my opinion for TBI type injecton. Since they behave much like a carb when delivering fuel. In there delivery when airflow is not high (rpms low) the fuel will fall out of suspension and pool on the manifold. Now when you nail the go peddle the incoming air greatly increases in velocity and this pooled up fuel will be drawn into the cumbustion chamber.

So with this table you can do some fine tuning sorta speak to take into account these dynamics that are taking place.

The reason I say its not as important is that our injectors spray the fuel basically right onto the back of the valve which leaves VERY little fuel on the manifold walls, even at low RPMs.

This brings me to my next point which ties back in with the original topic. Dave you really should consider upping your fuel pressure even with the 42 pound injectors when you get the pressure problem straightened out. I say this cause you will get better fuel atomization which keeps this pooling from happening and allows the fuel to atomize better and mix more efficiently with the air charge. It might only be a few HP, but it will all add up. You pump when working right will handle it no problem. If you like you can look up my write-up that was posted from a DFI tech which agreed 100% and put it in writing that higher pressures and higher duty cycles are some of the key things to making efficient setups that make more than your usual power. I hate to say it, but you can't argue with the results that some are getting.

Let us know what you find. Good luck.

 

Any news on the problem? Or solution?

 

No, I've been super busy. I getting all the little parts tomorrow and maybe this weekend I can tackle it. I tried to call Accel 5 times today but couldn't get through to talk to them about it either.