Thank you for the feedback.

The thing is though, it only started to go lean between two back to back runs.

And seriously, these two pumps combined flow like a gallon of fuel in five seconds.

I can indeed lower my fuel pressure and retune but it doesnt explain going lean between runs.

For next steps i was thinking do a pull let it go lean and shut off motor, then look at plugs

 

What do your coolant/ait trims look like? Maybe its heating up and pulling fuel?

 

didn't DC increase?

 

As has been stated several times now, it's unlikely that your going lean is caused by pump-issues. But it's not impossible.
Picture this: The pumps can barely make the pressure at the required flow, but they can make it. Now the fuel in your tank, sitting in a hot shop near a hot exhaust heats up and as a result the viscosity goes down. And all the sudden, the pumps can't make the pressure anymore because of the lower viscosity.
There may be many other potential reasons for this behavior that I can't think of right now. Fact is, if you're running something on the edge of its' specs or in a way it was never intended to, small random fluctuations of seemingly unrelated factors can cause a system to go from "works just fine" to "POS" in no time flat.

The fuel supply problem scenario is unlikely- granted, but not impossible.

And checking plugs NEVER hurts.

 

/\ I was going to say the same thing except he confirmed that it does it on the street too, not just dyno.

 

Does it ALWAYS do it now? If not, it could still be fuel heating up from exhaust. Or a million other things.

 

Bosch 044 fuel pump specs:

Minimum Flow @ Outlet: 80 GPH

So he has 160 gallons per hour of fuel pump. That is 2.666 gallons per MINUTE. Unless I am misunderstanding something, they should be operating NOWHERE NEAR their limits.

Unless BOTH pumps are failing, it isn't the pumps. He has 2 still, right?

 

Unless you **** up the threads. Remember, this is Fae....

 

or mixing them up with injectors

 

Oh wait, his impact gun is regulated. Forgot.

 

Just found a flow chart for the 044 pump. Looks like it's hitting the limit right around 120psi. That's under lab conditions. So it actually really may be the pumps just running beyond their specs.

 

what size primary wire are you feeding both those pumps with?

 

-6AN but don't quote me on that. I have read through a lot of build threads in the last few days.

Edit: Just happened to read through it: https://www.miataturbo.net/build-thr...23/#post755708

-6 from one pump, stock hose from the other. Maybe it is time for wider hosing.

 

 

lol



Am I the only one laughing about Fae running such a high fuel pressure and short duty cycle instead of running a normal pressure and a proper duty cycle like everyone else? Why didn't you start with a 138lb base pressure since we're just picking odd numbers to set it to? Seriously, it doesn't matter if that was the pressure it was set to when it came out of the box, you are allowed to turn it down.

IF you have the base pressure set too high, the line pressure might not actually be able to rise at the 1 to 1 ratio being requested by the regulator and may skew the tuning of your VE table. It also may perform differently from day to day or moment to moment since the resulting pressure will be dictated by the temperature of the pumps, available voltage and amperage, fuel tank level, etc. instead of the regulator precisely controlling it.

The only time I see you needing to use a higher than standard base fuel pressure is if your injectors are too small and you are trying to compensate instead of buying larger injectors. Are your ID1k injectors too small?

 

I am not saying that will solve your problem. I am saying what you have in there is not ideal and it MIGHT solve your problem.

Let's be realistic here instead of looking at graphs and data.
- The graph shows the pump tanking it at 120psi AT PUMP IN LAB CONDITIONS. Now you are asking 115PSI at the regulator which is after all the injectors. So that means through some lines (which I am not sure are big enough, they might be) and also filters, through rails, and all other restrictions and then getting to the regulator. So exact same thing as on the air side, will happen on the liquid side. So a 115psi at regulator might mean the pumps are pushing higher. Possible 120-125psi. Now add heat to that and you are totally screwed.

You have to step back and first try and see what can be wrong here. It could be something super simple or something complicated. This one sounds like a logical step as it might solve your problem. I have run 400whp in a 323 with a single pump set at 45psi open pressure and 27PSI and that was a small turbo. Anyways one thing at a time. please check that, retune it and see how it is on the street. If it doesn't fix the problem, at least you know it's not that.

By the way how are your two pumps hooked up, series or parallel? I am guessing they are parallel.

 

They are flat an spiffy. Logs are in my dyno thread.
I will try lowering the fuel pressure tomorrow AM.

The pumps are hooked up in parrallel.

 

Alright, so you are doubling up the volume, but the pressure capacity stays same as a single one.

One more thing: I noticed one place you mentioned you guys added timing to a point just before knocking. Now this does not have anything to do with your problems. But generally the higher the advance does not equate to higher power. You reach a point where the increased pressure in the cylinder actually negatively effects the power. For example I have tuned cars that you could have 40deg of timing without knock at a specific point in the rpm, however the maximum power was made at 36deg of timing at that point. Just remember that next time you are on the dyno. Play around with the timing specially after where the max torque would be (which definitely should be under 6000rpm unlike when the car/dyno issues are fixed). Just a FYI. You are going after so much power, better squeeze every last bit out of there!

 

You're talking about MBT, if you go over MBT you just start hammering on the big end bearings and not making any more power. I really doubt that at 35 psi the miata engine can hit MBT before knock. Not even the best fast burn GM heads can do that and their MBT numbers are typically lower than ours and their knock resistance better.

 

No. Look at my logs. I was at a whopping 14* at 36psi. That was with meth. At high boost my timing map is quite retarded. Mayyybe with e85 i could run 24* at redline. Yes, that would be approaching MBT. On pump, that is about as good as i can get with a safety margin.

For public knowledge: how did i find the margin? By advancing on the street until it knocked.

This means: forged pistons are really quite a big win. Do not build motor without.