End of Injection Timing Open Discussion

[kur4o]

I guess the y-body uses the same settings as f-body. I just checked some 94-95 y-body bins and they all have $60.

I don`t remember where I get that info, I am sure some y-body bins have $50 set. It could be from 96 lt4 y-body bin.

That could explain the difference in b-body, the iron heads get hotter and evaporate the fuel much quicker.

The formula is with the brackets

(720 - (<cell value> * 5.625)) so $60 = 180*

[Terminal_Crazy]

The LT4 bin I have has &60 at temp

I'm certain that the TDC referenced is the NEXT one, not the one that's just gone
If you look at my chart, &60 or 0x60 or #60 however you want to write hex values is
720 - (&60 * 5.625)
== 720 - 540
== 180 degrees on the std timing marks

Neither the 180 or 270 is anywhere near the EVC point but are before the intake opens.

IF you count back 180/270 from the rhs (time moves to the right) both points still have the intake valve open.
Turbulence would be greater there but I read the injectors can wash the bores down .

???


Mitch

[kur4o]

I know for sure that the graph was taken on stock b-body at normal operating temperature. The stock setting on all b-bodies is $50. So if you count backwards from 720* 5 low res pulses you go exactly where the graph is.

I was thinking to add a 2d table end of injection vs rpm target , but at max rpm you need to be below 50-60% Injector duty cycle to make it useful.
I am at almost 85-95%DC so it is almost full time open.
Anything above 70% inj dc, the injector starts spraying while the intake valve is still open, and that spray should be for next ignition event.


On the graph at exhaust cycle there is hugh pressure in the cylinder, exhaust gases are escaping and if there is intake open during the exhaust cycle, the pressure should be injected back in engine intake, that can explain the egr effect the overlapped cams have.

The point where pressure starts to drop at the exhaust cycle can be consider the entry point for fuel, air to enter the cylinder.

I can`t imagine how usefull be that graph on high lift , radical cam.

Here is the image again

[spfautsch]

While I've been (not so) patiently waiting to get my block back from the machinist I've little to contribute along the lines of actual test data, but I couldn't sleep this morning so came here to catch up. I noticed a bit of activity on the EOIT topic in this thread also.

A few days ago it struck me that the relationship the EOIT value in $EE has to the power stroke has already been confirmed. kur4o's post here nails it down. I was initially confused at how he was getting 270 degrees because I was working with some assumptions based on of the mis-information that Y body tunes used the same target as the B bodies. Once that was cleared up (Y body tunes are set to 0x60 at normal operating temps) I must have stopped thinking altogether - for some reason seeing the B body EOIT fall on a 90 degree interval caused me to incorrectly infer that it was irrelevant. But it's not.

I know for sure that the graph was taken on stock b-body at normal operating temperature. The stock setting on all b-bodies is $50. So if you count backwards from 720* 5 low res pulses you go exactly where the graph is.

I was thinking to add a 2d table end of injection vs rpm target , but at max rpm you need to be below 50-60% Injector duty cycle to make it useful.
I am at almost 85-95%DC so it is almost full time open.
Anything above 70% inj dc, the injector starts spraying while the intake valve is still open, and that spray should be for next ignition event.

This all makes perfect sense now. Sorry for being so dense!

Mitch I believe contrary to my earlier supposition, your table here is correct. The F and Y body / aluminum head tunes have the EOIT target at 180 or BDC of the power stroke, on a closed intake valve. As long as I'm not once again horribly mistaken the value you came up with through testing (0x63 if memory serves) was actually giving the fuel slightly more time to evaporate, not keeping it from being injested into your exhaust system. To move your low pulsewidth injection window so there can be no fuel in the port while the exhaust valve is open, assuming it closes at 388 degrees as in your chart you'd need some value less than 0x3b. Not to mention subtracting some margin for nominal idle pulsewidth, which would need to be converted to degrees at your target idle speed.

[Terminal_Crazy]

This all makes perfect sense now. Sorry for being so dense!

Mitch I believe contrary to my earlier supposition, your table here is correct. The F and Y body / aluminum head tunes have the EOIT target at 180 or BDC of the power stroke, on a closed intake valve. As long as I'm not once again horribly mistaken the value you came up with through testing (0x63 if memory serves) was actually giving the fuel slightly more time to evaporate, not keeping it from being injested into your exhaust system. To move your low pulsewidth injection window so there can be no fuel in the port while the exhaust valve is open, assuming it closes at 388 degrees as in your chart you'd need some value less than 0x3b. Not to mention subtracting some margin for nominal idle pulsewidth, which would need to be converted to degrees at your target idle speed.

I had hoped we'd have some people testing this & collecting data.
I'm not 100% sure mine is accurate. The LHS seemed to respond whilst the RHS went the other way.
I've just swapped out my O2's and seem to be getting slightly differing data than previously.
The rhs looked whiter than the left.
The VE table now looks a little healthier than before.
I've also rewired by wideband and am getting more stable results than before.

Car ran well but still rich untill i get the VE table to settle down.
Eoit is something i will retest when i'm happy the car is better.

Eoit:
Moving past the exhaust closing point didn't seem to improve anything but I wouldn't trust my data 100% here.
Yes adding the extra 15 degrees seemed to lower the BLM's slightly before the inlet opens.

Mitch

[spfautsch]

Bear in mind that when you change EOIT to inject directly into the cylinder you'll be throwing at the very least the lower MAP areas of your VE table out the window. Unevaporated fuel doesn't burn the same as raw.

[kevinodb1]

Hi Folks

Just to put some perspective of how long it may take for the Fuel to get from the end of the injector to the valve face, here are some calculations:

It is about 2.6 Millisecs at 2000 RPM and 0.8 Millisecs at 6500 RPM, it varies depending on revs, the airflows are from STD EA files that come with the software, I have averaged them.

This time needs to be taken into account in the overall timing for EOIT.

Who knows what speed the Injector is actually spraying at? But we can only assume its mixes with the air and assumes that velocity and that will have to do.

I now finished some other calculations that show the EOIT really is only relevant at low revs because the rest of the time it will never be right anyway, as per what the Lucas Racing reference I posted earlier says.

Still useful for the Low rev scenarios though.

I have updated the original table I had in this post to show transit time of the fuel from the Injector tip to Valve face in Milliseconds.

I have added a second table that shows that for the STD LT1 cam the Intake duration where flow is meaningful(@.050 onwards) is exceeded by the actual Pulsewidth from 2000 RPM on even for small throttle openings.

Cheers
Kevin

[Terminal_Crazy]

So which end does does the #60 540 end up on the chart on the std timing diagram?

Mitch

[kur4o]

So which end does does the #60 540 end up on the chart on the std timing diagram?

Mitch

$60 is at the end of power cycle on graph.

If you count After TDC it will be at 180* ATDC
If you count Before TDC it will be at 540* BTDC[720-180]

SO the math will be after TDC counts from 0 to 720.
Before TDC will be [720 - degrees after TDC]

0* is at the start of power cycle and 720* is at the end of compression cycle. That should be norm for timing chart.



What that bothers you may be that the EoiT target is inverted.

From left to right
0-720 degress = $80- $00 target value in table

[spfautsch]

That could explain the difference in b-body, the iron heads get hotter and evaporate the fuel much quicker.

If I had to guess I'd say just the opposite - the b body cams have less / no overlap. Whatever the case, that's the reason I'd love to see a scope capture on an f-body or y-body because I'm fairly certain 96 decimal / 0x60 puts the end of injection at the bottom of the intake stroke.

So which end does does the #60 540 end up on the chart on the std timing diagram?

I'm not sure if this was aimed at me, but I believe this is what your EoIT_List.txt should look like. I think you're focusing on semantics more than you should - the EOIT value is identifying where the spray stops on any given cylinder, and each cylinder fires once every 720 crankshaft degrees.

Edit: another way to look at it, 720 degrees from the perspective of eoit is the same as 0 degrees. It just depends on which way you want to visualize it - from a degree wheel perspective or the way the ecu keeps track of it.

[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