High pressure pump spiking really high on lt4 after lpe injectors

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12-01-2021
lt1z350

High pressure pump spiking really high on lt4 after lpe injectors

So doing a car that was running great and swapped to some lpe injectors. Car didnt run no idle I mean it was crap on lpe tables that came with it. So reached out to Nostrum as lpe is useless and dustin an engineer/calibrator looked at a log and took the tune and changed up around 15 tables. Now we got somewhere car starts idles black smoke gone working good enough to go drive and log. So after adjusting and part throttle work I told him try a wot on it. Car goes a little lean .88 and 4800 rpm the pump pressure go from commanded 2900 to 3200 back to 2900 then 5400 it slams 4200 psi and locks the injectors up and huge lean spike as expected. So I send the log to dustin and trys to tell me its due to the 38 percent lobe on the cam and 32 percent axis I had on the pump. I see big tuners that leave that table stock. On this one I had forgot it had a 38 lobe and put the 32 percent axis as I told him some car specs.
Now I know that is not the issue as I said many dont even bother to touch it on cars with cams Ive seen tunes from howard and many other cars I have re tuned for people that (good) known tuners have done. So now scratching my head on what can cause such a spike on a pump that I was commanding 2900 and had 3200 in the max pressure tables. I have had conversations with Bob owner of FIC and he told me how many sets of injectors he has got back with the springs broken in them from people commanding 3400 plus psi to them. So I always in my tunes lower things trying to be proactive as there is no reason for them to over pressure.
This is the first time I have ever seen it this bad. Some cars I have seen it hit 3200 if injectors got near limits and recovered it can go over but always goes back to commanded.
Has anyone seen it so bad it makes the injectors lock up like this? I can post a log but it is like a dead fuel cut like dfco almost when off throttle big spike so I know they are no longer working though at 3.3 ms. Hoping someone has some idea of why this can happen.
Thanks
12-01-2021
sevinn

Quote:

Originally Posted by lt1z350

So doing a car that was running great and swapped to some lpe injectors. Car didnt run no idle I mean it was crap on lpe tables that came with it. So reached out to Nostrum as lpe is useless and dustin an engineer/calibrator looked at a log and took the tune and changed up around 15 tables. Now we got somewhere car starts idles black smoke gone working good enough to go drive and log. So after adjusting and part throttle work I told him try a wot on it. Car goes a little lean .88 and 4800 rpm the pump pressure go from commanded 2900 to 3200 back to 2900 then 5400 it slams 4200 psi and locks the injectors up and huge lean spike as expected. So I send the log to dustin and trys to tell me its due to the 38 percent lobe on the cam and 32 percent axis I had on the pump. I see big tuners that leave that table stock. On this one I had forgot it had a 38 lobe and put the 32 percent axis as I told him some car specs.
Now I know that is not the issue as I said many dont even bother to touch it on cars with cams Ive seen tunes from howard and many other cars I have re tuned for people that (good) known tuners have done. So now scratching my head on what can cause such a spike on a pump that I was commanding 2900 and had 3200 in the max pressure tables. I have had conversations with Bob owner of FIC and he told me how many sets of injectors he has got back with the springs broken in them from people commanding 3400 plus psi to them. So I always in my tunes lower things trying to be proactive as there is no reason for them to over pressure.
This is the first time I have ever seen it this bad. Some cars I have seen it hit 3200 if injectors got near limits and recovered it can go over but always goes back to commanded.
Has anyone seen it so bad it makes the injectors lock up like this? I can post a log but it is like a dead fuel cut like dfco almost when off throttle big spike so I know they are no longer working though at 3.3 ms. Hoping someone has some idea of why this can happen.
Thanks

Is this at a higher rpm? My personal car was doing this with an lt4 pump but it didn't lock up the injectors (guess it couldn't provide enough to do that). Mine was floating valves a bit and it started right around there.
12-09-2021
Joshinator99

2900 is the absolute max on those injectors isn’t it? They (LPE) recommended 2175. While you can obviously go higher, running the absolute max doesn’t sound like a great idea IMO. I’ve had no lockup issues in the 2175-2500 psi range.

Also, to your point, LPE is colossally useless and I cannot get Nostrum to answer a call or email. Did you have trouble with cold idle with the +52 injectors? Mine are fine once the car warms up, but even Ben Charles threw up his hands about these injectors when cold.
12-09-2021
lt1z350

I actually got nostrum to give a hand on it and they changed I shit you not 12 tables I beleive to make it start and idle well. Id be willing to share that with you maybe can help or if ben is over it I can take it on if you are not into doing it your self.
They told me 2900 was just fine on it and what was happening was it was dropping bank 2 on the narrow band going lean then of course the ecm trys to correct by throwing a ton of pump at it and right about 3900 they totaly shut off. I have seen some tuners a few years back running lt4 at 3550 no issues other then eventually blow the springs in them I am told. But they dont lock up. The FIC can lock up at 3800 psi as seen that when car goes too lean and shoots too much pump pressure at them.
We found that cylinder 8 was about 60 percent on a leak down test as it kept getting a little oil on that plug so Im guessing that weak cyinder is causing a problem on it. its been so random on how the car runs though sometimes starts right up fine not rough other times it runs just fine mostly cold had the issues but so much better on the new settings and when fresh plugs seems good so blaming some of this now on a bad hole so car is getting a lme 390 now. I am just temped to send them back to nostrum and get tested make sure no issues. You pay that kind of money on an injector and it should come with paperwork and settings that drop in and go just like any good port injector or the FIC 30s. I do know also that on all of these you must lower pump pressures to get the injector MS up higher none of them like it under 1.2 ms at idle or low throttle as say .8 when you leave pump pressure stock it spits and stumbles and wont even set a miss fire just runs like crap.
I see that 9.65 also and at that power id think the car would go faster. I ran 9.30 @150 stock ported blower on a shake down day with shifting issues. Dragy had me at a 5.20 60-130 while I have not been back to the track in similar conditions the car is now in the 4.60s 60-130 so I expect mine to run 8s now 155 plus stock ported blower still. That or your in a location with some bad da. I ran 9.57@147 at bristol which is uphill and at 1700 feet the et killer Im told by locals lol It was 83 degrees that da and didnt bother checking da I just knew it was really bad. Id think yours would have a lot more in it.
12-09-2021
Joshinator99

Quote:

Originally Posted by lt1z350

I actually got nostrum to give a hand on it and they changed I shit you not 12 tables I beleive to make it start and idle well. Id be willing to share that with you maybe can help or if ben is over it I can take it on if you are not into doing it your self.
They told me 2900 was just fine on it and what was happening was it was dropping bank 2 on the narrow band going lean then of course the ecm trys to correct by throwing a ton of pump at it and right about 3900 they totaly shut off. I have seen some tuners a few years back running lt4 at 3550 no issues other then eventually blow the springs in them I am told. But they dont lock up. The FIC can lock up at 3800 psi as seen that when car goes too lean and shoots too much pump pressure at them.
We found that cylinder 8 was about 60 percent on a leak down test as it kept getting a little oil on that plug so Im guessing that weak cyinder is causing a problem on it. its been so random on how the car runs though sometimes starts right up fine not rough other times it runs just fine mostly cold had the issues but so much better on the new settings and when fresh plugs seems good so blaming some of this now on a bad hole so car is getting a lme 390 now. I am just temped to send them back to nostrum and get tested make sure no issues. You pay that kind of money on an injector and it should come with paperwork and settings that drop in and go just like any good port injector or the FIC 30s. I do know also that on all of these you must lower pump pressures to get the injector MS up higher none of them like it under 1.2 ms at idle or low throttle as say .8 when you leave pump pressure stock it spits and stumbles and wont even set a miss fire just runs like crap.
I see that 9.65 also and at that power id think the car would go faster. I ran 9.30 @150 stock ported blower on a shake down day with shifting issues. Dragy had me at a 5.20 60-130 while I have not been back to the track in similar conditions the car is now in the 4.60s 60-130 so I expect mine to run 8s now 155 plus stock ported blower still. That or your in a location with some bad da. I ran 9.57@147 at bristol which is uphill and at 1700 feet the et killer Im told by locals lol It was 83 degrees that da and didnt bother checking da I just knew it was really bad. Id think yours would have a lot more in it.

Sent you a PM to discuss further. Thanks!