End of Injection Timing Open Discussion

[Stroked 388]

Does anyone know at what Degrees the intake valve opens on a stock 94 LT1. I can't find any type of cam card for a stock cam. The cam I have now opens at 15.5* BTDC. But the eoit tabe is still stock

[Terminal_Crazy]

Does anyone know at what Degrees the intake valve opens on a stock 94 LT1. I can't find any type of cam card for a stock cam. The cam I have now opens at 15.5* BTDC. But the eoit tabe is still stock

I couldn't find anything definitive when i looked. Some figures contradicted themselves a little.
This is what I found.



Lloyd Elliott @ 0.006 @.050 Lobe Lift Lift 1.5 Lift 1.6 Lobe Sep Intake CL IVO btdc IVC abdc EVO bbdc EVC atdc Overlap Adv
Hi lift emission ~275/281 223/231 .610 .594 112 109.5 28.5 66.5 77.5 28.5 56.5 3
Comp Cam Card Spec 275/285 223/231 .381 .371 112 108 3 39 51 0 (0.050 figures)

1 249-07-466-8 XFI 268 CAM LT1/LT4 93-96 268/276 218/224 .357/.354 .570 .565 113 109 25 63 75 21 46.0


92 vette 205/207 .451 .450 117

Stock LT1 1993-95 Vette & F bodies 202/207 .450 .460 .480 .491 116 22.5 (guess at 252/257 duration)
1996/97 F Bodies 205/207 .447 .459 .477 .490 117
LT4 203/210 .446 .449 .476 .479 115


(It probably needs to viewed in a non proportional font like in wordpad)

Mitch

[kevinodb1]

Hi There

This is the information I have on LT and some other GM Cams.

Part Number .050 Duration 1.5 rockers lift 1.6 rockers lift Lob sep angle Notes
GM 14093643 202/207 .404/.415 N/A 114.5 1987 350,305 Manual
GM 10088155 179/194 .350/.384 N/A 109 1987 305 Auto
GM 10066049 207/213 .415/.430 N/A 117 1988-89 350,305
GM 10111773 202/207 .413/.428 N/A 114.5 1990-92 350,305 Camaro
GM 12551705 202/207 .447/.459 .477/.490 117 1993-97 LT1 Corvette
GM 12551142 203/210 N/A .476/.479 115 1996 LT4 Grandsport Corvette
Crane 243931(Holden 92029026) 216/226 N/A 0.491/.491 112 1986 VK Blue Commodore(Group A)
Holden 92060781 214/214 N/A .486/,486 112 1988 VL and VN Group A(215KW)
Crane H268 883931 206/206 N/A .448/.448 112 1989-91 Holden VN SV5000
Crane H276 883941 214/214 N/A .464/.464 110 1989-91 Holden VN Group A
GM 24502586 218/228 .492/.492 .525/.525 112 LT4 Hotcam
GM 12370847 234/242 .539/.558 .575/.595 112 GM 847 cam for LT1 and LT4
GM 12370846(19210723 NEW #) 222/230 .509/.528 .543/.563 112 GM 846 cam for LT1 and LT4

Cheers
Kevin

[Stroked 388]

Thanks for the helpful information very useful

Gary

[Stroked 388]

Thanks Mitch that was some helpful information. By my calculations I need to set eoit at around 168 +/- a few thanks again


Gary

[JimCT_9C1]

Does anyone know at what Degrees the intake valve opens on a stock 94 LT1. I can't find any type of cam card for a stock cam. The cam I have now opens at 15.5* BTDC. But the eoit tabe is still stock

Been following along... this is from the impala forum:
B-Body LT1: INT - 191º .418" EXH - 196º .430" LSA - 111º P/N 10243779

Not sure about the factory installed intake centerline, but assuming its 111 straight up I get the following at 050, with roughly +/- 25 degrees for lash points:

IVO @050: 111-191/2 = 15.5 ATDC (-25=9.5 BTDC@lash)
IVC @050: 111+191/2-180 = 26.5 ABDC (+25=51.5 ABDC@lash)

EVO @050: 111+196/2-180 = 29.0 BBDC (+25=54.0 BBDC@lash)
EVC @050: 111-196/2 = 13.0 BTDC (+25=12.0 ATDC@lash)

Hope this helps -

Jim

[vilefly]

Sorry I was extremely late to the table, guys. Do you need a scope of injector on time vs tdc vs crank signal? I only have my stock B-body to play with. I might have time today to grab some scope shots. I also have a thermograph camera at my disposal, but not much use unless someone shows up in an F-body with headers.

[spfautsch]

As I mentioned in the PM - I don't think there's anything more to learn. I completely shifted my brain into neutral after getting hung up on the misinformation and completely overlooked the elephant in the room.

You sure have some cool toys available to you. The idea of using a FLIR to identify header temps / cylinder balance never crossed my mind but it seems there are some relatively affordable pieces available now that are made to attach to a smartphone.

[vilefly]

Actually, the best use for FLIR is in finding electrical faults. Go after the hot spots.

Had to gather all these unique tools because of the pressed-on cam lobes in both gm and fords that used to slip during an overheat scenario, leaving me with an unknown cam duration and timing mystery with the difficulty of proving it to the customer. They both later fixed the cheap, hollow cam issue, but I had the burden of proof for warranty validation. Ford misfire data was unavailable, also. The pressure sensor helped me find the faulty cylinder cam lobe. A cylinder pressure waveform vs MAP sensor readings would tell one what the cam and valves are doing.

Here is a link that teaches cylinder pressure waveform interpretation. It is very good.
http://autoditex.com/page/cylinder-p...nsor-64-1.html

There is a PDF download button on that page. The pressure transducer is far more useful than the FLIR. Get it first, I say.

Here is a waveform breakdown pictures with various scenarios. broken valvetrain items, vvt engagement, etc.
https://www.automotivetestsolutions....ts-page-1.html

if you are programming for a camshaft combo, this should help with the plotting and planning of injector on/off times, I hope.

[Terminal_Crazy]

NOTE:
========
Kur4o: Appolgies, I could have pm'd you but if you're like me, I don't seem to get notifications of mail.

I'd like to bring to everyone's attention that I've seen the freaky injection PW issue again.
I used to reflash with EEHack 4.70.
On several occasions I've flashed with Kur4o's version 4.92 (December) and earlier versions.
I reflashed recently and have seen the differing PW issue again. Reflashed with 4.7 and it's gone away.
The car ran fine so I think it's a logging or reporting issue rather than a PCM issue and the log shows the issue when viewed in either version.

On suspiscion of this issue I've rechecked my EOIT timing test and the issue is showing up on that log.

On the two attached images you can see the differences on the IPW

I feel this invalidates my test. Has anyone reproduced or seen this?

I've replaced the PCM and reflashed with EEHack 4.70 without issue.

Mitch

[Stroked 388]

I have had some time to mess with eiot in eehack. Before I was getting the big cam problems strong fuel smell showing lean when you can tell it wasn't ect. So adjusting my eoit down 5* at a time I noticed my AFR going more rich so i kept repeating the steps till I seen no change in the AFR. now it shows it is rich and removing fuel witch the wideband conferms that it is rich. I ended up at 146 on the eoit. Less fuel smell and better response. Now my ve table is not that great it's red all over in the cells in the analyzer. Very happy with the outcome so far just need more tuning