Installed my 1200cc injectors this weekend. They are bored out stock 850s. This was done by RC Engineering for $175 each.

I had asked around about what "lag time correction value" was needed , if needed, to be entered into the PFC. No one gave me an answer. This value has to do with delay time from when the injector receives the turn on pulse to when some(?) fuel flow fuel results. Being that mine are stock with the pintel and opening reshaped, the mechanical opening timing would be the same as stock. Where as going to a different brand, this value would change. Of course the flow charateristics would be changed due to the increased size of the opening. This results in a shorter pulse to the injector. Logically they should flow faster than before.

So I did not inter a lag correction value. The engine runs fine under full boost without any flat spots.

 

i was wondering if the extra fuel before the turbos give extra air could be the cause of some boost creep or spike. Does this make any sense? could it be possible?

 

i thought "lag time correction value" would delay a bit of fuel until you have more air to go with it.

 

At 8000 rpm, there is only .0025 seconds between adjacent apex seals passing thesame point of the engine. That means the absolute maximun time that is available to inject fuel into the chamber is also .0025 seconds. This means the timing of fuel injection has to be right on else the fuel will be injected out of phase with the actual air going into the chamber.

Carbs pre-mix the fuel with air upstream of the combustion chamber at a constant rate so timing is not a factor involved. Our system injects the fuel into two points. The primary injectors right in the intake ports. That is about 2" inches from the chamber. The secondaries are about 4" from there intake ports. For maximum fuel disperstion/evaporation, the injection timing has to be so that the injected fuel completely goes into the chamber with the
flowing air. Intake port timing and intake/exhaust ovelap affects this ideal time. The lag correction is to insure that this point is maintained.

 

Did you have to pull out some fuel? Have you noticed the O2 voltage drop when you initially hit throttle?

I installed some 1300cc secondaries some time ago, and had to pull out a good amount of fuel. Mostly with the PIM/RPM page, but also some through out the map.

Part throttle O2 voltage is reading .89-.95, and WOT is still reading .93-.97

 

My part throttle O2 voltages (closed loop) are same as they ever where. The engine actually seems to run better under boost. Before I was hitting 93% duty cycle at 12.5 psi boost. There is no noticeable indication of running richer. Throttle responce is great for all driving conditions. In fact I think it is better than it was. I'll be doing some tunning in a few weeks with a UEGO linear O2 sensor that we (Houston group) recently ordered.

 

Yea, I did install a Walbro at the same time, so there's a variable.

What I'm most concerned with though is the short lean condition when I first tip into the throttle. Do you notice anything like this?

TIA.
es

 

Tuning notes. One injector measured out at 1196cc and the other was 1203. The 1196 is .33% undersized. The 1203 is .25% oversized. Since the rear rotor tends to run hotter then the front and brake apex seals more often(rumers heard over the years from the list), I placed the 1203 in the rear. I set the PFC secondary injector size as 1199. Thus the front will run .25% lean and the rear will run .33% rich.

 

This doesn't seem right. The number should be .0075 seconds.

It sounds like you are assuming that the rotor rotates at the crankshaft RPM, which it doesn't.

It sounds like your math went like this:

8000 x3 (rotor spinning at 8000 rpm, 3 sides of the rotor pass the point during each rev)

8000x3= 24000

60/24000= .0025

But in actuality, the rotor is only spinning at 1/3 the the crankshaft speed, so at 8000 indicated rpm the rotor is only actually spinning at 2666.66 rpm

So it should be 2666.66 x 3 (rotor spinning at 2666.66 rpm, 3 sides of the rotor pass the point during each rev)

2666.66x3= 8000

60/8000= .0075

 

You are correct, I messed up the calculation!
The point I was trying to show, was that the available time for
injection at 8000 rpm is very small.

 

Chuck, could you contact me via email at herc_driver_00@yahoo.com I have a few questions about the injectors I'm about to put in (1200CC). I also use the Power FC and have a few technical questions about the install and changes within the PFC. Thanks, Travis

 

Hey Chuck,

I'm installing some stock 850 transformed by RC into 1200's. To make sure I'm understanding you right, your saying that I can just install them and not change a thing in the PFC since the injector is actually a 850 right. What should I see in the PFC reading? Should my injector duty drop or will I be running super rich? How will it work without retuning the fuel since the computer thinks its still running a 850 sized injector?

You advise will be a great help!!!

BTW - I bought these inj from ErnieT if you want to ask him about the flow rates (I saw your other post). They are probably all the same because they are modified with the exact same machinery and tolerances.

Thanks,
STEPHEN

 

Change the secondary injector size to 1200 and their pulse correction factor from 0.0 to +.04.
They are not noticeably richer, but I have not
tuned the maps since then. CAr runs great just doing that.

 

Awsome, thanks man

Later,
STEPHEN

 

Chuck,
How did you get that number? .04, just curious...

 

Ray programmed that value into a friends PFC that has 1200s.

 

Hey ! chuck can you tell me what will that value be for 1300cc injectors. I'm istalling some in my Fd , I also have the PFC.



Thanks

 

still waiting on a reply please.

 

Since I do not have 1300 and nobody with 1300 have posted, I had to write a friend about it. He has not answered me yet.

Patience Grasshopper!

 

Here are the settings XS engineering entered for my unit. I can't give you much else regarding performance as I don't have the injectors in yet (enlarged 850's). I have no idea why they changed the primary settings, anyone?

Fr-Pr 100.0% -0.12 ms
Fr-Sc +0.20 ms
Rr-Pr 100.0% -0.12 ms
Rr-Sc +0.20 ms
Q-Pr 550cc
Q-Sc 1300cc

Can't seem to get this formatted correctly but you know what I mean.

Alan

 

adax

is that with a single turbo?

 

I have sequential twins (upgraded to some minute degree by Pettit) and that was what it was supposed to be programmed for. Wait until you see the timing split!

Alan

 

I have 1300cc secondaries. Reminder me to get that info for you tomorrow.

 

Alan,

I tried your Fr-Pr -0.12 ms and Rr-Pr -0.12 ms and it caused my idle to be rougher and low end responce to be worse.

Change your sto 0.00ms as is normal and see what it does to your engine.

 

Chuck,

I'm still not completely installed (don't have 1300's in yet) but here's what 's going on currently: Cold started it after the initial install and let it idle for 20 minutes with no electric load, then for 20 with the AC on and lights on. Idle adjustment screw and bleed screw were set appropriately. This was with the XS injector settings. No load idle is very rough (but not the 800-1200 hunting thing, just rough). Timing is bouncing all over the place during this. Now, XS programmed the fans to turn on at 88 degrees and when the fans are on, it's as smooth as silk. Idle with load (AC and lights)is acceptable. I changed the injector settings to "stock" (0 everywhere) since I still have stock injectors and went for a drive. Idle is improved at no load but still rough. Additionally, I've got some stumble on low RPM throttle tip-in. The accelerator inrichment settings are pretty different from stock so I'll work on that tonight to see if I can cure that problem. I'm wondering if the primary injector changes they entered are supposed to compliment the accelerator settings and changing one now throws it all off? I'll eventually richen up idle cells but I need to get the 1300's in before I screw around with it too much more. They had the trailings firing before leadings by 14 degrees in some areas. Other negative split areas were similar to what you found in Spyfish's maps which speaks more to problems with the initial coding as a problem. Wish there was a way to know exactly what the timing is. Does 0 mean TDC?

Alan