Injectors - Advice

[GOLDCYLON]

Originally Posted by Scrrem

No, I may have him take a look over the winter It's Mark's chip and the car has had this issue since I put the newly calibrated chip in. I really noticed it bad on the mountain run.
Rich

He has my 380 cal on file it might be worth a shot. It took a few swaps via the mail but I'm sure I am running the 90% solution

[secondchance]

Originally Posted by Scrrem

Yun,
Are you absolutely certain it's an injector? I have had a persistent stumble on the new motor under WOT and some times on high RPM deceleration with throttle closed. I believe it may be a chip issue. Did the symptom change a from the injector change?
Rich

Yes. Issue was rough idle at first. Picked up 8 FIC Bosch rebuilt injectors from Phil. These new ones were installed for primaries. Removed primaries with high ohms were used to replace 3 secondaries with relatively low ohms. Now, engine developed loss of power and vibration as secondaries come on line. So much for resistance testing for injectors...

Either way, I want to rule out injector issue 100% first. FIC had posted that they found out these Bosch rebuilds we're shorting out and decided to drop the line. Hopefully, once I pop in Accels car would be back to what I remember.

[XfireZ51]

Schance,

I assume u r not getting a code? Usually loss of power and engine shudder comes from secondaries not coming on. Are you mix and matching injectors or are the all one type?

[secondchance]

Originally Posted by XfireZ51

Schance,

I assume u r not getting a code? Usually loss of power and engine shudder comes from secondaries not coming on. Are you mix and matching injectors or are the all one type?

I'm not getting any code - not yet anyway. I have been running FIC Bosch rebuilt units since 2009. Recently idle was so rough dual mass flywheel was making a racket. So, I replaced 8 primaries with new Bosch rebuilt injectors and replaced possible border line secondaries with what I assumed to be better injectors removed from primaries (all Bosch) - wrong! Now, she shudders as secondaries come on line. BTW - I have secondary delete so, I believe, secondaries come online at 5% throttle (if I remember correct...).

[tpepmeie]

My $0.02... Many times "the chip" is blamed for issues which are actually mechanical in nature. Marc's basic calibrations are tried and tested over hundred's of cars, so I would be more inclined to suspect a mechanical root cause.

Your statement that you swapped the old primaries into the secondary position grabbed my attention. I'd suspect a potential problem there. Did you check the resistance of the now secondary injectors? Apologies if I missed that earlier. Does the symptom manifest cold as well as fully warmed up?

[tpepmeie]

As a more general follow-up to the title of this thread, I have become very fond of the Bosch / Ford Motorsport injectors. These are the newer EV6-style, longer and skinny. There are 24 lb/hr versions, as well as 30 lbs, 16 of which are more than enough for 800 hp.

Why do I like these? First, they are a direct fit. A more modern design than the Accels or Multecs. And most importantly the full injector characterization is available from Ford (voltage and pw offsets), although it has to be translated to GM's method.

The 24 lbs'ers are the "LU24A" variety. The 30's are BB302's. From what I have seen, they are linear at very low pulsewidths so even the 24's should be ok for a lightly modified engine. Ford's flow rating is at 39.15 psi, so the 24's flow like 27's at LT5 rail pressure.

Contact me offline if you want more info.

[secondchance]

Originally Posted by tpepmeie

My $0.02... Many times "the chip" is blamed for issues which are actually mechanical in nature. Marc's basic calibrations are tried and tested over hundred's of cars, so I would be more inclined to suspect a mechanical root cause.

Your statement that you swapped the old primaries into the secondary position grabbed my attention. I'd suspect a potential problem there. Did you check the resistance of the now secondary injectors? Apologies if I missed that earlier. Does the symptom manifest cold as well as fully warmed up?

Old injectors - I believe they were still warm (about 70-80 degrees) by the time plenum was removed - all registered 15.3 to 15.5 ohms. New ones - cold at about 55 to 60 degrees - all measured around 14.6 - 14.7 ohms. I assumed ohm difference was due to temperature. Engine vibration showed up almost as soon as I drove away from Jim's garage so symptom showed up when cold and stayed when fully warmed up. What do you think Todd? Seriously mis-matched injectors?

[XfireZ51]

Originally Posted by secondchance

I'm not getting any code - not yet anyway. I have been running FIC Bosch rebuilt units since 2009. Recently idle was so rough dual mass flywheel was making a racket. So, I replaced 8 primaries with new Bosch rebuilt injectors and replaced possible border line secondaries with what I assumed to be better injectors removed from primaries (all Bosch) - wrong! Now, she shudders as secondaries come on line. BTW - I have secondary delete so, I believe, secondaries come online at 5% throttle (if I remember correct...).

I'm sure that w Marc's chip the secondaries come on-line right off idle.

[Roadster]

Originally Posted by XfireZ51

I'm sure that w Marc's chip the secondaries come on-line right off idle.

The content below is from my conversation with Tim Holland back in 2014 after I purchased my ZR-1. I thought it would a good read here with the injector conversation.......
In case you would like to read the thread, here is the link....
http://www.zr1.net/forum/showthread.php?t=22910


Re: My recent phone conversion with Tim Holland GM/LOTUS Engineer for the LT5....

more info from the call......the following may have already been discussed over the years, and known by many, but I thought it would be interesting to mentioned what we talked about now, some 20 years later.

...The LT5 was on the dyno for at least 400 hours, GM's dyno testing was very aggressive at the time.
...The LT5 ran hotter than usual at the time. (I imagine he was comparing the LT5 to the other engines of that time period)
...When I asked him about the PROM chips available from the aftermarket, such as Marc's and others, especially with the fans coming on at lower speeds, he said that the oil needs to be @ 88 degrees centigrade,
(which is 190.4 degrees F) in order for the oil to boil out the condensation in the engine. He said you don't want to run these engines at like 150 F, as it would do more harm than good. Even with the fan temps from the aftermarket PROM chips, I think we are ok, JMO.
And he also mentioned if doing a lot of short trips, to make sure you get up to operating temp. There is also a thermostat in the oil line.
...a twin roller chain was added for the cams, as they seemed to have a problem with the earlier single roller chain. (hope I understood him correctly on this one).
....make sure you are warmed up at operating temp before doing any WOT's.


the remaining part of our conversation......

...engine is more fuel efficient on all 16 injectors open rather than just 8 injectors.
...talking about the "tube" going from the rear of the trans to the axle,(I imagine the "tube" he was referring to is the driveshaft. Mentioned that when accelerating that you should be smooth with power delivery, and not jerk the engine in gear, such as accelerating in 1st gear, letting off, than accelerating again in same gear (jerking). This puts undo stress on the bolts that connect the joint at the back of the trans, which can come loose from that motion (think I understood him on that) which can sag when applying torque and therefore result in the gear lever (shifter) moving upwards when accelerating. This is a machined part and needs to be exact. Apparently this was discovered during testing, thus resulting in using a smooth delivery rather than a jerking power delivery.
...secondary injectors opening is based on fast you are going and not a specific RPM.
...clutch reservoir contains the "black cup" as I refer to as.....which purpose is to prevent air and moisture from entering the system. That "black cup" should be collapsible to underneath the cap, mine isn't. But not to run without one.
...also spoke about changing out the anti-freeze fluid in the engine. I mentioned about the Dex-Cool may create complication on the gaskets, he said he was not aware of that, but also mentioned that he has been out of the "circle" for a number of years. When I said about filling the system and not getting any air pockets, he said that there are bleeder pipes on top of the plenum (he thought between #2 & 3 and #4 & 5 cylinders). The fill cap was placed on the highest point of the engine for a purpose. He also mentioned that when filling the system, that it will purge itself.

My thought is.....Of course alot more has been learned about the LT5 since the production years and different ways to maintain and prevent any possible complications that may arise.

That was about the content of our conversation from all of the above posts, interesting to say the least, especially for me, as I am still in the learning process of the LT5 and the ZR-1 overall.
Glad I could share with you.......thanks for looking...


ok some clarification on the subject......I had mentioned to Tim that it was recommended to bring the r's up to 7k in first and second gear to make sure that the secondaries would open and that the engine was running good. From what I remember and took notes on, he mentioned that the opening of the secondaries were based on the speed of the vehicle and not a specific RPM to where they open. The following is my thoughts....Obviously when you hit a certain RPM in an aggressive start, the vehicle is traveling at a certain rate of speed. I would imagine that traveling at a highway speed and a certain rpm range that is less than an aggressive acceleratioin and rpm range from a start would still open the secondaries as speed increases.
Again, I have nowhere near the knowledge that this forum has, and just thinking logically out loud. I intend to contact Tim in the near future, and will make sure to ask him to explain this once again. I was trying to get in as much as I could during our conversation and doing "shorthand"...lol
Wish I had the conversation taped........

[Paul Workman]

Originally Posted by XfireZ51

I'm sure that w Marc's chip the secondaries come on-line right off idle.

That is true, according to Marc, in the context of his SECONDARY DELETE calibration ONLY- if that is what is being discussed.

Op: For clarification, the secondaries are triggered ON based on rpm AND throttle position and operating temp - all three being considered.*

*Except for the secondary deleted calibration where the secondaries come on just off of idle. At that point the pulse width is split between two injectors, thus maintaining proper AF ratio.

An excellent source for information is contained in: "Corvette Fuel Injection and Electronic Engine Management" by Charles O. Probst, ISBN: 0-8376-0861-9 by BENTLY Publishing.

It contains excellent diagrams, schematics, charts and technical details in a well written and easy to understand style. It is an excellent read, especially for anyone that just bought a ZR-1, or for someone just needing to brush up on his knowledge and troubleshooting.