EFI on Four Banger Flathead Ford

[horsewidower]

I really enjoy seeing older engines adapted with EFI.  Thanks for sharing, I'll look forward to seeing updates.

Bob Holmes

[NathanStewart]

Actually our biggest concern is keeping the flywheel on the crank and not so much blowing it up.  The achilles heel of the stock crank is the flange and we've cut a few motors in half after the flange breaks and the crank free revs to 7000 rpm or so and all the rods let go and take out the block.  Yeah, we don't like it when that happens.

^^Well I hate to sound like a pessimist but I am a realist and can't hope for something that I know isn't going to happen.  Our biggest concerns wound up materializing for us yesterday when the flange broke off the back of the crank at the end of a WOT pull.  But not all was lost... absolutely not.  At a minimum we learned a LOT plus we were hitting our power target which was very affirming.  So here's how it went...

We did some initial tuning on Friday after work and by time we had called it wraps for the night we were already making half throttle power pulls and seeing good results.  Surprisingly, it didn't take quite as much time to get the injector phasing and advance stuff dialed in.  It's by no means dead-on perfect but I think it's a hundred times better than before so it seems like just having sequential fuel delivery made a huge difference by itself.  I'd say our proof of concept has been validated.   

On Saturday morning we started right back at it again bright and early and it wasn't long before we got into doing WOT pulls.  We had bought 10 gallons of the 101 octane unleaded gas that ERC has at the June El Mirage meet thinking it was more than we would need.  Well we wound up running out about mid day and had to get something to keep going.  Luckily I knew of a place near by that was a VP dealer so we picked up 5 gallons of their 100 octane "street blaze" gas.  Oh boy did changing the gas make a huge difference - for the worse.  It was running really sweet on the ERC gas and it sounded fat and blubbery on the VP but I made some changes to the fuel map to compensate and we carried on.

The goal was 150 crank hp.  Working backwards from our power goal, I figured on 10% drivetrain loss and the Mustang dyno we were tuning on reads absurdly low... like 15-20% low.  A known 400 hp car will come to our dyno and make 300 whp.  Anyways, so 150 hp would be 135 hp to the wheels minus 20% power on the heart breaker dyno puts us at 108 whp and we were making 110 whp very consistently.  We were like "wow, we're actually doing what we wanted to do... cool."  I was trying to get the AFRs dialed in a little better on the top end and then BANG, the flywheel broke loose.  All of a sudden there was lots of black smoke and sparks and a whole lot of noise and then it was quiet... very quiet.

After it was all said and done I went back through and counted all my data logs and there were 47 and I know I didn't log every single run so we had some 50+ runs on this motor before the crank let go.  Honestly, I'm glad it happened on the dyno and not on our first pass down the track or on record runs or something.  What usually happens in this instance is what I described in the quote above; the crank free revs to some absurd rpm and then the rods let go and we totally destroy the motor.  Well this time it revved to about 6000 rpm and then the limiters kicked in and kept it from going higher so all the rods are still inside the block and hopefully not hurt.

It looks like Speed Week is out for us this year.   I think after breaking who knows how may cranks we're finally done screwing around with stock crankshafts.  They are just too much of a liability to even mess with once you're making this kind of power.  We don't exactly know what our next step is but we want to get back at it soon.

Here are some vids from the dyno.  Sorry about them being so short; I had someone else working the camera.

VIDEO 1 Eeeehh this was a camera test.  Oops.
VIDEO 2 Running it up through the gears.  The o-scope is showing you a clue to our key tuning point.
VIDEO 3 WOT pull to 5000 rpm.  The smoke is water spritzing out of the cracks in the head and onto the headers.   
VIDEO 4 Another WOT pull to 5000 rpm; I was getting a shower standing over there.
VIDEO 5  Partial pull; I had figured the alternator wasn't working when my battery volts at idle was less than 12.  Well it was confirmed when the voltage dropped below 8 volts in the middle of this run and everything started to go lean.  Shut the motor off then tried to crank it over and all we got was a click.  Dead battery.  Swapped it out for another one and kept going.

So that's it.  Our mule was pretty short lived but it served its purpose and now its legs have fallen off and it can't go any more.  We should be able to drop this tune into our next motor and keep going.  Things should really start to get fun once we get the turbo back on.   

[Stan Back]

Dad looks plenty courageous standing in the flywheel plane, knowing the history of the rear main.

[NathanStewart]

He's part honey badger.

[dieselgeek]

Nice!!

reminds me of sorting out the Fireball 8 buick, happy with the tune and on the last pull - all hell breaks loose.  It happens.


I am anxious to hear how the turbo version comes along, keep us posted!

[johnneilson]

Nathan,

sorry to hear the crank let go, not bad for putting out about 3 times the design HP.

Did you have to do anything other than just use the injector trim functions to balance out AFR for 1-2, 3-4?

I assume the O-scope was the showing injector pulses for 1 and 2.

John

[NathanStewart]

It wasn't so much trims (as in a percentage trim +/- based on the base injector pulse width) as it was timing/phasing (when the injector actually opens) and advance (changing when the injector opens based on engine speed/air flow).  The scope is showing the injector pulse in relation to the cam sync pulse that's been setup to trigger at TDC exhaust which is right when the intake valve starts to open.  Basically I'm making sure that the fuel pulse is occuring while the intake valve is open.  When 2 & 3 start to trend lean while 1 & 4 are still good I know that my injection advance is off and needs to be adjusted.  If only one of them goes lean or rich I then trim that one cylinder up or down to match the others.

[dieselgeek]

Nathan, did you base your injection timing on "end of event" or "beginning of event" - and where did you place the injection overlap?  I.e., the intake valve is open approx 25% of the engine cycle, but the injectors are (presumably) open longer than that.  Did you put the excess squirt at the beginning while the valve was closed, or at the end after it closed?  I am guess the beginning but curious to hear since you are the first guy I know to put a 'scope on a siamesed intake engine.

And again, very, very nice work.  Your team probably has no idea how lucky they are to have you working the EFI.  That kind of homework is big bucks if you are buying it at street prices

[johnneilson]

Nathan,

I follow, and it makes sense.

I was thinking more along the starvation of 2 and 3 as loss of air comparitively to 1-4.

My thoughts were more to changing the cam timing to allow for more on 2-3 and narrow up 1-4.

Good work, keep us EFI nuts informed.

John

[NathanStewart]

The AEM EMS is fundamentally a "start of injection" injection system.  I had done the math based on the cam specs and found that at 6000 rpm (our absolute max possible engine speed) the intake valve was open 12ms which means I had to be able to deliver all of my fuel in 12ms valve open time divided by 20ms cycle time which is 60% duty.  Our target horse power level with the turbo is 300 hp so I have to be able to deliver 300hp worth of fuel but I'm limited to that 60% duty again.  This meant I had to use really big injectors (1600cc) to make a fairly low level of power.  I also did some rough calcs to come up with port velocity to try and figure out how long it'd take for the gas to leave the injector and reach the valve.  Calculated speed was an inch per ms and it's roughly 3 inches between the injector and the valve so I started with 3ms of advance (as measured on the o-scope) and went from there.

Then it was just a matter of getting the fuel pulse "right" enough to make the AFRs generally acceptable and then I played with the injector advance until the AFRs were more consistent across all cylinders.  So because I'm using a start of injection system it inherently takes a little bit longer to get everything setup correctly when I could just dial in an injector closing point with an end of injection system but that's what I have to work with and I was able to make it work so in the end it's all good.  The advance is only 2d based on rpm but it'd be nice to have a 3d map that's also based on load.  Everything will be spot on in high load/wot but a little off in lower load states which we think is okay.

I would best describe the final setup as a "middle of injection" injection system.  I had thought that it would want a fixed end of injection point which required a lot of advance with bigger pulse widths but the motor didn't seem to like this.  By the time we were done with it it was really the middle of the injection event that stayed pretty consistent.  We'll see if that still holds true once we go boosted.

[El Wayno]

Big injectors for that amount of power is right whew. Sounds like it idles ok. What kind of pulse width you running at idle? What kind of AFR's? Just wondering if you had trouble keeping it in check with those bigguns. Will you be able to hit your target HP boosted or will you need to add injectors to the setup? How was the fuel run? I didn't understand the two Reg's with one being dead headed, or are you running secondary injector set up with bigs and littles injectors?

[Tman]

Interesting stuff to read Nathan for someone that knows nothing about EFI

[Rex Schimmer]

Wayno,
I think Nathan is right that because they are tuning for WOT at 300 hp the big injector works. Doing a little, pie are square-three bags full, fuel flow for the 300 hp turbo set up needs to be around 180 lbs/hr, assuming a BSF of .6 lbs/hp-hr (a little rich but it makes it safe for a turbo). If you sized an injector for just these parameters you would need something in the 5-600 cc/min size but Nathan wants to inject all of the fuel during the inlet valve event so you need the big injector. Probably wouldn't run well on the street but it is looking right for the WOT application.

Nathan, what fuel pressure are you running? You state that you are running two regulators with one to regulate fuel pressure and the other as a dampener. I assume that you are thinking that there are pressure ripples from the fuel pump (?)Regulators make pretty poor dampeners and they certainly cannot respond at the frequency of the fuel pump output. You would be better off to run a piece of rubber hose in place of the "dampener" regulator and plug the end the added capacitance will be enough to reduce the pump ripple to almost nothing. To check what the pump ripple is you will need a high response pressure transducer probably 0 to 250 psi and a scope or laptop with soft ware to be able to read it . All of the Bosch style fuel pumps are a type of vane or gear pump so pressure ripple it at the number of vanes or gear teeth and as the pressure goes up the ripple drops because the internal leakage goes up and acts as a dampener.

Rex

[dieselgeek]

Wayno,
I think Nathan is right that because they are tuning for WOT at 300 hp the big injector works. Doing a little, pie are square-three bags full, fuel flow for the 300 hp turbo set up needs to be around 180 lbs/hr, assuming a BSF of .6 lbs/hp-hr (a little rich but it makes it safe for a turbo). If you sized an injector for just these parameters you would need something in the 5-600 cc/min size but Nathan wants to inject all of the fuel during the inlet valve event so you need the big injector. Probably wouldn't run well on the street but it is looking right for the WOT application.

Speaking from actual experience, if you have your dead time well mapped, it's not hard at all to get good street manners out of injectors sized in this method.

Nathan, what fuel pressure are you running? You state that you are running two regulators with one to regulate fuel pressure and the other as a dampener. I assume that you are thinking that there are pressure ripples from the fuel pump (?)Regulators make pretty poor dampeners and they certainly cannot respond at the frequency of the fuel pump output. You would be better off to run a piece of rubber hose in place of the "dampener" regulator and plug the end the added capacitance will be enough to reduce the pump ripple to almost nothing. To check what the pump ripple is you will need a high response pressure transducer probably 0 to 250 psi and a scope or laptop with soft ware to be able to read it . All of the Bosch style fuel pumps are a type of vane or gear pump so pressure ripple it at the number of vanes or gear teeth and as the pressure goes up the ripple drops because the internal leakage goes up and acts as a dampener.

Rex

Pretty sure he's damping pulses from the injection events, not the fuel pump.   

[Rex Schimmer]

Dieselgek,
I had not thought about that but it does make some sense, still when he turbos the engine he will have to pilot both the pressure control valve and also the "dampener" valve from the inlet plenum to keep the differential pressure constant across the injectors, and I can see the "dampener" valve not wanting to respond as fast as may be required. It will be fun to see what happens. Keep at it Nathan we are all waiting!!!!

Rex