Need help changing injector size in XFI

gibbstroy

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Jan 12, 2018
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Any help is certainly appreciated. Ive searched all the Googles for several days now. Most of what Ive read involves adjust VE tables, but it doesnt seem like thats right.

My combo is listed in my sig with the only a recent change from Racetronix 160's to Bosch 210's. I have already changed the injector size in Fuel Calculation Parameters. Im also in closed loop and using Flex mode and Fuel Energy Constant at .781 which has worked very well prior to the change. I've also adjusted Injector Opening Offset vs Battery Voltage to the point of it running smoother than ever under idle and normal loads (.60 at 13.6v and .58 at 14.4v) any lower at 14.4v and it starts to stumble.

What I need help with is at high boost at upper rpms. Fuel pressure has not been changed, it now idles at 40psi (was 43) climbs to about 60-70psi under boost (usually up to 80's) but the pressure falls on its nose about 3500-4000 rpm getting near 25psi boost before I have to get out of it (normally 35).

The injectors are obviously going too rich and maxing the pump, the afr's show very rich by 2 points or more. O2 correction is anywhere from +-4 to +-8. I havent logged anything yet, it seems obvious what the problem is. How can I control the injectors back down on the big end?
 
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NY Twin Turbo

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Do you think you need 210 lbs injectors? I figure the 160's could maybe take you down to 9.0 with E-85. Have you maxed these out yet?

If so, than maybe you need a bigger pump. I use an Aeromotive Pro with 160's.

Your WOT correction should be closer than + or- 8 percent. But even more interesting, if your pressure is dropping as your pulse widths increases, then maybe you shouldn't see any negative correction at all, just positive. Then also it would be unlikely for it to be rich by a full 2 points. It shouldn't be rich Unless there's too much range in both directions in your correction limits map and too much gain? Then it goes rich and over corrects in the opposite direction? These may be a few things to check out.

But your pressure should not be dropping even if your injectors are at 100 percent duty cycle. If they are, the problem is the voltage to the pump or the pump itself.

Seems like a lot of trouble for an upgrade you may not be ready for yet.
 

gibbstroy

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Jan 12, 2018
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Thanks for the reply! I haven't maxed 160's out, they were just failing so this was a fix more than an upgrade. I got a good deal on the bosch 210's and I have more in the 6466 turbo anyway, so I figured Id swing for the fences.

I havent figure out how to post a log so heres a screen shot. I noticed the TPS first and have already re-calibrated, but it was no improvement. You get a bett idea of what o2 correction is doing. The fuel pressure drops in a similar way to the climb in actual afr. Its starting to look like pump failure, but its sure a coincidence that it happens the same day as the injector change...

log snip.PNG
 

NY Twin Turbo

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You don't have fuel pressure logged, but I'll take your word on it dropping off.

I seem to be the only guy chiming in here. But before I continue, I just want to say I don't consider myself a tuning expert by any means. I just want to help and these are some of the ways I would probably go about doing it for myself.

That being said, I don't see any negative correction in that data log. And where the boost is the highest it was probably at +25 percent.

You have the time line at the only point in the log were the actual and target AF's are close. Your target AF is awfully rich at 9.63. But that doesn't matter here. Because everywhere else it wasn't able to achieve this and it was massively lean. Your going to burn her up.

I might be an extremist, but I think every TR owner should theoretically have enough fuel pump to feed there injectors at 100 percent duty cycle and up to 40 lbs of boost. Bad pump, or too small, or voltage problems, either way. If you can't be certain this can happen, it's time for an upgrade.

Just for kicks, you may consider looking at the regulator too. Run the pump with the engine off. Set base fuel pressure at 43 PSI. Apply 40 PSI of air pressure to the regulator. See if the fuel pressure goes to 83 PSI. It should have no problem with the injectors not spraying. You will also hear the pump pushing its ass off. Hey, you never know. You may expose pump problems as well.

Make sure you have fuel delivery first.

Later, go back and start over and enter your saved 160 LB tune (I hope you saved it when it was running right). Then change the injector constant number. Then change the injector opening offset vs voltage map to match your specific injectors. Just these two things are never going to be all that there is. You will still have to go through all your maps and tweek, and tweek, and tweek.
 

norbs

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Until you get the fuel setup STABLE i would not try to tune around it!
 

gibbstroy

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Jan 12, 2018
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Allen, TX, United States
You don't have fuel pressure logged, but I'll take your word on it dropping off.

I seem to be the only guy chiming in here. But before I continue, I just want to say I don't consider myself a tuning expert by any means. I just want to help and these are some of the ways I would probably go about doing it for myself.

That being said, I don't see any negative correction in that data log. And where the boost is the highest it was probably at +25 percent.

You have the time line at the only point in the log were the actual and target AF's are close. Your target AF is awfully rich at 9.63. But that doesn't matter here. Because everywhere else it wasn't able to achieve this and it was massively lean. Your going to burn her up.

I might be an extremist, but I think every TR owner should theoretically have enough fuel pump to feed there injectors at 100 percent duty cycle and up to 40 lbs of boost. Bad pump, or too small, or voltage problems, either way. If you can't be certain this can happen, it's time for an upgrade.

Just for kicks, you may consider looking at the regulator too. Run the pump with the engine off. Set base fuel pressure at 43 PSI. Apply 40 PSI of air pressure to the regulator. See if the fuel pressure goes to 83 PSI. It should have no problem with the injectors not spraying. You will also hear the pump pushing its ass off. Hey, you never know. You may expose pump problems as well.

Make sure you have fuel delivery first.

Later, go back and start over and enter your saved 160 LB tune (I hope you saved it when it was running right). Then change the injector constant number. Then change the injector opening offset vs voltage map to match your specific injectors. Just these two things are never going to be all that there is. You will still have to go through all your maps and tweek, and tweek, and tweek.
That’s a great idea! I’ll give that a try Monday.


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gibbstroy

Member
Jan 12, 2018
76
16
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52
Allen, TX, United States
You don't have fuel pressure logged, but I'll take your word on it dropping off.

I seem to be the only guy chiming in here. But before I continue, I just want to say I don't consider myself a tuning expert by any means. I just want to help and these are some of the ways I would probably go about doing it for myself.

That being said, I don't see any negative correction in that data log. And where the boost is the highest it was probably at +25 percent.

You have the time line at the only point in the log were the actual and target AF's are close. Your target AF is awfully rich at 9.63. But that doesn't matter here. Because everywhere else it wasn't able to achieve this and it was massively lean. Your going to burn her up.

I might be an extremist, but I think every TR owner should theoretically have enough fuel pump to feed there injectors at 100 percent duty cycle and up to 40 lbs of boost. Bad pump, or too small, or voltage problems, either way. If you can't be certain this can happen, it's time for an upgrade.

Just for kicks, you may consider looking at the regulator too. Run the pump with the engine off. Set base fuel pressure at 43 PSI. Apply 40 PSI of air pressure to the regulator. See if the fuel pressure goes to 83 PSI. It should have no problem with the injectors not spraying. You will also hear the pump pushing its ass off. Hey, you never know. You may expose pump problems as well.

Make sure you have fuel delivery first.

Later, go back and start over and enter your saved 160 LB tune (I hope you saved it when it was running right). Then change the injector constant number. Then change the injector opening offset vs voltage map to match your specific injectors. Just these two things are never going to be all that there is. You will still have to go through all your maps and tweek, and tweek, and tweek.
That’s a great idea! I’ll give that a try Monday.


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Well I tried it and the pressure jumped to 90’s, the pump sounded like it was working hard at that! I’m headed in the right direction. Filters next.


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norbs

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May 25, 2001
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Really you need to flow test with the return line into a bucket, at a maintained fuel pressure( psi 43 +plus your boost pressure) and measure the volume in one minute. Battery voltage must be similar to what you would expect under same conditions while racing. Pumps and regulators and filters have flow restrictions under high pressure. The fuel system sees high pressure externally but the injector will always flow at 43 lbs regardless, into the motorif your base pressue is 43 lbs
 

NY Twin Turbo

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Dec 10, 2014
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Well I tried it and the pressure jumped to 90’s, the pump sounded like it was working hard at that! I’m headed in the right direction. Filters next.


Sent from my iPhone using Tapatalk
Like I said earlier, this is just for kicks and to verify that the regulator is working. And if you applied 47 PSI of air pressure, then 90 psi would be fine. You also proved that the pump doesn't die-off at this increased load.

But like norbs is saying above, it's time to go further. This test doesn't show that it's flow is capable of supporting six 210lb injectors, spraying at 100 percent duty cycle, at 40lbs of boost.

And just for the record, I didn't want to come out and just say it, but I don't think it does.

The Aeromotive Eliminator is only rated for 1000 lbs per hour at 45 psi and at 13.5 volts. This is according to Summit's listing information. You would be about 260lbs short. As a matter of fact, it wasn't even big enough for your 160's.

Something to keep in mind. Just because you installed larger injectors, it doesn't mean your fuel demands have increased. Actually, they are exactly the same as before. And since you weren't using all your injector or pump before, you certainly aren't going to use all of it now. But you should still have a good matching set of parts. You can conduct the testing that norbs suggested. However, I wouldn't bother. Splitting hairs is not something you want to do with fuel systems.

In the end, If your 160lb injectors were more than sufficient before, I would have put on a new set to replace them, and I still would have upgraded the pump.

I am the number one victim of the over-kill disease. So, I know how it goes. But maybe you do the pump and put back on a set of 160's?
 

gibbstroy

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Jan 12, 2018
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Allen, TX, United States
Well like I said before, I wasnt maxing the 160's, they were failing. And going to 210's gave me room to go up in power. The eliminator actually shows to be capable of 1400hp injected and boosted. On e85 that drops to 980ish, and my 6466 is only rated to 900. If I upgrade the turbo, Ill still have duty cycle room. And I agree with you both on fuel systems, Im still likely to bump up the pump as well in the future.

Anyway, I found the problem. This was the 40M after pump filter after blowing air from the inside. Unbelievable that it got like this with such low miles (roughly 4000). The 100M prepump filter was dirty but not too bad.

Thanks to all for helping! Im a bit embarrassed for having missed the first thing I should have checked.
 

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NY Twin Turbo

All the good stuff.....Times 2.
Dec 10, 2014
2,478
842
113
47
Westchester NY
Well, that certainly can have something to do with your problems.:)

And don't be embarrassed about missing something simple. I chased a problem all summer once just because I never took a closer look at my plug wires. Besides sometimes I like to explore some issues with others just for fun. And I hope to learn a bit myself along the way.

But don't forget. You still have to tune these 210's. And it may not be all that easy.

Let us know how you do.
 
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