Fixing over compression on a 2FE (Camshaft analysis?)

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RockDoc said:
It's been ages since I've worked with these ideas, but there's some discussion starting at post 144 here from when i built my first 2FE:


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improving flow for the 3FE’s top end

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Post 230 by FJ40Jim will be of note for you too.
Click to expand...

Holy smokes, I have some homework to do. When the weather clears up I'm going to tear into the engine again to get the most precises measurements I possibly can. Thankyou for sharing this info!
 
@RockDoc
So I wrote up a program to aide in my estimation of compression ratios and camshaft timing. I used your numbers as posted here for reference.
forum.ih8mud.com

improving flow for the 3FE’s top end

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I had a bit of code where it would tell you cylinder temp at compression to better predict detonation but its getting late and I have too many different units in this thing. Later on im planning to factor in the dynamic valve opening as in this formula we have now treats the valve as a 1 or 0 and doesn't specify the inlet size. Its a good baseline but not very precise. or so I think. Lots to do lots to do...

code is in PDF
 

Attachments

And I had wondered if throwing math at you was going to be a good idea, lol.

See the chart in post 118 of this thread to see more cam options (i have no idea how easy it is to get your hands on all of these options). The Schneider and Crow cams shown have an even later intake closure than the Delta cam (62° ABDC vs 59° for the Delta KC859). There's another at the end that has an even later closure, but I think that would be too "hot" to be a decent street cam. With the 262° Delta, my 2FE lopes at idle a bit but runs strong through the Rev range it sees in front of an auto transmission.

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Camshaft

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If you have access to a compression tester and a running stock 2F or 3FE (or better yet a 'warm' built one that runs on pump gas), a comparison of your average compression (178 psi?) and stock, with the same gage and conditions, might give you an idea of how much you need to drop.

IIRC, you mentioned earlier that you were suspicious that one of your injectors was bad. It might be worth swapping or testing / cleaning them and inspecting the wiring to make sure you aren't running with one or more cylinders getting a mixture that's out of whack. (Someone correct me if I'm wrong, but I believe a lean mixture will detonate more easily than stoiciometric or rich) Did you post spark plug pics? Someone with good old school experience might be able to pick up on lean cylinder(s) by appearance.
 
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RockDoc said:
And I had wondered if throwing math at you was going to be a good idea, lol.

See the chart in post 118 of this thread to see more cam options (i have no idea how easy it is to get your hands on all of these options). The Schneider and Crow cams shown have an even later intake closure than the Delta cam (62° ABDC vs 59° for the Delta KC859). There's another at the end that has an even later closure, but I think that would be too "hot" to be a decent street cam. With the 262° Delta, my 2FE lopes at idle a bit but runs strong through the Rev range it sees in front of an auto transmission.

forum.ih8mud.com

Camshaft

forum.ih8mud.com forum.ih8mud.com

If you have access to a compression tester and a running stock 2F or 3FE (or better yet a 'warm' built one that runs on pump gas), a comparison of your average compression (178 psi?) and stock, with the same gage and conditions, might give you an idea of how much you need to drop.

IIRC, you mentioned earlier that you were suspicious that one of your injectors was bad. It might be worth swapping or testing / cleaning them and inspecting the wiring to make sure you aren't running with one or more cylinders getting a mixture that's out of whack. (Someone correct me if I'm wrong, but I believe a lean mixture will detonate more easily than stoiciometric or rich) Did you post spark plug pics? Someone with good old school experience might be able to pick up on lean cylinder(s) by appearance.
Click to expand...
I had the injectors sent out and cleaned by a guy, they all returned within spec but the knocking didnt change, I have some spark plug pictures somewhere, they all looked okay-ish. its an intermediate knock only when the engine is at operating temp regardless of load. I put in some premium gas from a non kroger gas station and it helped but didnt eliminate the knock. The ignition timing is already set back 8* if i recall correctly.

Im going to chase the compression rabbit hole as my cylinders are 25% higher in compression than stock.
I need to do some reading on valve opening lift and exhaust valve timing and its effects on engine dynamics etc.

If im correct Ill actually have an assignment in school coming up were im required to 3D model an intake and exhaust valve then derive its equations of motion to accurately animate the valves opening and closing operating. Ill take that mumbo jumbo of information and attempt to model a 2f intake and exhaust valve system with valve open and closure data. but thats a FAT BIG IF, I wouldn't wait on it to anyone reading this.
 
RockDoc said:
And I had wondered if throwing math at you was going to be a good idea, lol.

See the chart in post 118 of this thread to see more cam options (i have no idea how easy it is to get your hands on all of these options). The Schneider and Crow cams shown have an even later intake closure than the Delta cam (62° ABDC vs 59° for the Delta KC859). There's another at the end that has an even later closure, but I think that would be too "hot" to be a decent street cam. With the 262° Delta, my 2FE lopes at idle a bit but runs strong through the Rev range it sees in front of an auto transmission.

forum.ih8mud.com

Camshaft

forum.ih8mud.com forum.ih8mud.com

If you have access to a compression tester and a running stock 2F or 3FE (or better yet a 'warm' built one that runs on pump gas), a comparison of your average compression (178 psi?) and stock, with the same gage and conditions, might give you an idea of how much you need to drop.

IIRC, you mentioned earlier that you were suspicious that one of your injectors was bad. It might be worth swapping or testing / cleaning them and inspecting the wiring to make sure you aren't running with one or more cylinders getting a mixture that's out of whack. (Someone correct me if I'm wrong, but I believe a lean mixture will detonate more easily than stoiciometric or rich) Did you post spark plug pics? Someone with good old school experience might be able to pick up on lean cylinder(s) by appearance.
Click to expand...
Yes, lean will detonate much more easily than a rich mixture, the extra fuel cools the combustion event (unless you're a diesel)
 
So using boyles law I was able to estimate my current squish volume to be ~78.31cc from the stock ~92.5cc which would mean that from the machine shop shaving my engine down I lost ~14.19cc in squish volume.

Plugging in my estimated squish volume into my calculator (Post #143) to be 78.31cc I get the following.
Static compression ratio = 10.02 : 1
Effective compression ratio = 8.61 : 1

as compared to stock being estimated at
Static compression ratio = 8.31 : 1
Effective compression ratio = 7.17 : 1

I hope im wrong... lol. I know there's error in my calculations as I didnt use the ideal gas law, or estimate any error but this still seems a tad high. I might have to scratch a bit more at the math and confirm my answer.
 
Ouch! I wonder how much you need to regain to run pump gas.

With ~70cm2 bore area, you'd need 2mm more deck/gasket to get back to stock squish by those numbers.

Thinking out loud... Swap on an uncut / minimally skimmed head?

Chamfer the lip around the chamber of your current head and grind/polish out the beaded casting surface in the chamber to gain a bit of volume?

I don't imagine you can do anything to a stock piston without compromising its integrity, plus you are digging deeper into the engine to mess with pistons.

A quick calculation I did last night suggests going from 53° to 59° ABDC intake closure reduces swept volume by 4%, 62° should reduce it by 6%.
 
The head and block on it now are running their final life, The machinist told me they could never be cut down again. Kinda pisses me of because I know the block had never been cut before.
I would like to just grab a new block if I can find one, without the head-gasket the pistons protrude above the deck, Im not sure if they should do that but it just looks wrong.

with a 62° Intake ABDC would put me at these values below.

2FE Current Estimates
Intake valve opening ABDC = 53.000
Static comp ratio of stock cam = 10.02 : 1
Effective comp ratio of stock cam = 8.61 : 1
Effective Swept volume for stock config = 595.857 cc

Intake valve opening ABDC = 62.000
Static comp ratio of new cam = 10.02 : 1
Effective comp ratio of new cam = 8.10 : 1
Effective Swept volume for new config = 555.984 cc

The routes Ive considered in order are
new cam?, new block, new head, custom ECU, different engine.
 
So im beginning to animate a rotating camshaft relative to the piston and valve position. Getting a lobe to rotate like this was a PITA, I plan to do the rest later.
 

Attachments

ChaserFJ60 said:
So im beginning to animate a rotating camshaft relative to the piston and valve position. Getting a lobe to rotate like this was a PITA, I plan to do the rest later.
Click to expand...


that JIS Jazz in your attachment seems pretty complicated Chase ?

i like it straight forward ... :D 🍻





8BoB.gif
 
ToyotaMatt said:
that JIS Jazz in your attachment seems pretty complicated Chase ?

i like it straight forward ... :D 🍻
Click to expand...
Haha basically what im trying to do except Im going for a scale model animation which is very different and for an important reason.

What I'm aiming for is different in the sense that the animations of the cam, push-rod, rocker arm, valve, piston, etc. will be entirely based on the same formulas used to calculate compression ratio, effective sweep, etc. The animation will be used as a visual check that the equations are correct and that no issues such as valve to piston collision etc. will occur by numerical and visual checks. There will also be side by side to scale animations comparing two different configurations and their positions relative to the other moving engine components with displayed engine data. Its somthing Ive wanted to do as a pet project and im using the cam position as means to justify the time spent in the code.
 
ChaserFJ60 said:
Haha basically what im trying to do except Im going for a scale model animation which is very different and for an important reason.

What I'm aiming for is different in the sense that the animations of the cam, push-rod, rocker arm, valve, piston, etc. will be entirely based on the same formulas used to calculate compression ratio, effective sweep, etc. The animation will be used as a visual check that the equations are correct and that no issues such as valve to piston collision etc. will occur by numerical and visual checks. There will also be side by side to scale animations comparing two different configurations and their positions relative to the other moving engine components with displayed engine data. Its somthing Ive wanted to do as a pet project and im using the cam position as means to justify the time spent in the code.
Click to expand...


SOR sells a optional 2F CAM

called a RV cam

higher lobe and lift
 
Feeling your frustration I imagined cutting a block extension plate and sleeving the cylinders. Could that work? (Not unlike a double head gasket really)
 
Trying to improve my cam lobe profile to be exact. Its 100% configurable, you can use a slider to change the dimensions and everything follows it to scale. its pretty neat. However, I cant find any data on the stock 2F's camshaft profile or any camshaft lobe for that matter. Anyone have any leads?
iu


My profile beginning to take shape, The opening and closing ramp will have adjustability to vary the valves sweep's open and closing speed / dynamics etc etc. Trying to plot the tangent points to the nose and base ramps now.

1675668539027.webp
 
RockDoc said:
Are you looking for something more than the data from this post?
Click to expand...
I was hunting for specifics like the nose lobe diameter and specific cad drawings like a manufacturing shop would use. I'm realizing quickly that I will need to derive these values based off given data
 
So step 1, creating a camshaft lobe profile is almost complete. in the program i wrote you can make any camshaft shape or size (as long as its symmetric) and it fills in the other details for you. I just need to now 'Digitally scan' the shape in some way to graph the lifter opening sequence. I dont know how to calculate the nose diameter yet so right now its just guessed. Ill do the rest later, All this thinking makes one hungry.
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@ChaserFJ60 n @RockDoc , i thought i had a reasonably good grasp of engine building but NOPE! this thread is making me realize i'm still in f#%kin' kindergarten :hillbilly:
i am finding it very interesting though. thanks for the edumacation guys
 
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