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Vizard: fuel hogging with siamesed ports

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twas_brillig

Jedi Knight
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I have David Vizard's book "Tuning the A-Series Engine" and recollect that he advises that the siamesed intake ports cause 60% (or some such) of the fuel charge to go to one cylinder and 40% to the other - but can't remember which cylinder got the most; what the percentages actually were; and can't find it by skimming the 520 pages.

Anyone remember reading this? what the numbers were? what chapter? There's no index in the back, unfortunately. I'm still dreaming of Megasquirt EFI and would like to know what Vizard says, and then to try to find out if it would be possible to use a single injector and have two different fuel volumes injected.

Thanks

Doug
 
Outside cylinders (1 and 4) run leaner on siamese port engines with 1-3-4-2 firing order. They also get less mixture.
I don't have the Vizard book any more, but 60% rings a bell with me.
 
Oh gesh, lets no go there.
 
Hey I just saw this and since I'm actually using a single throttle body injection system on my Midget, I thought I ought to chime in. The way my system works, it is no different than the guys who are running a single SU (like HS6). In fact, my throttle body system uses and HS6/HIF carb body to act as the throttle body and a MiniSpares 1 into 2 intake manifold. The injector sits where the old dashpot and needle used to be. So if you think about it, on the carb, engine vacuum pulls fuel up from the jet in the middle of the carb and mine sprays fuel down from the middle of the carb... The engine isn't going to see any difference. Now whether a single carb/injection point is optimal or ideal... I guess that's another question. But I can tell you my car is running fine and it's running strong.

You can see pics of it at https://www.cardomain.com/ride/762889/3

JACK
 
Jack - is yours megasquirt?
 
With any manifold and using a single carb, dual carbs or single/dual throttle bodies or even putting injectors in the intake runners near the head, would you not still have problems of charge inconsistency with the same siamesed port?
 
Jack - are you using the Patton adapter for your injector?
Tom - I'd have to read all of Vizard to really comment, but the charge inconsistency appears not to be a real problem regards engine life/power etc. etc. My curiosity is due to dreams of megasquirt EFI, which leads to wondering if it would be possible to use a single injector at the siamesed port, and be able to fine tune the EFI (using a colortune?) such that each cylinder would get a slightly different fuel volume - kind of splitting hairs, I guess.
Glad to see the comments & discussion.
Thanks,
DOug
 
Hi guys.
JPSmit: YES-I'm using megasquirt and
twasbrillig: YES-I'm using the Patton adapter.
bigjones: Haven't done MPG calcs yet but the engine has a big cam and wasn't built for MPG.

58Custom- In theory, if you had an MPI system, you could adjust each "squirt" to compensate for the charge inconsistency. That along with x-Tau compensation should get you pretty refined and dialed in terms of charge consistency-per-cylinder, HOWEVER, I personally considered that to be, as Doug said, splitting hairs. The point you make goes both ways; "(any setup)... would still have problems of charge inconsistency with the same siamesed port" and therefore conversely, it doesn't matter what setup you use, they'll all function equally as well as (or better than) the original.

There is a Mini MPI injection system for A-Series motors that uses all the same engine components as we do, but has one injector at each of the siamesed ports. I also thought of going this way (since it is a direct bolt on) by getting parts off of eBay.co.uk but I decided it was too much of a crap-shoot buying used EFI parts from England and the gains would be infinitesimally small.

JACK
 
Which version of MS did you build? I have a MegaJolt and a couple of SU's that have been heavily modified now and I wonder if I could go to EFI by just installing a single O2 sensor, building a MS box and adding two adapters to my SU's? Does the MS system still use the Ford EDIS box or is it a complete replacement? And will it accurately work controlling two TB's by monitoring a single O2 sensor?

If so then I am already more than 1/2 way there now!
 
I built a Megasquirt II v3 from a kit. They have a new hardware release out now (MS III daughterboard) that has some really awesome additional features like a high speed dual core processor, onboard SD card logging (for datalogging), and a built in USB adapter which makes using a newer laptop way easier. Right now I'm using a dinosaur laptop because it is the only laptop I have with the DB9 connection. Also, I just looked and they are actually sold out of MS III right now, but if you're serious, I would wait for the next shipment which they say will be soon.

A single O2 is fine since there is only a single exhaust manifold/pipe. I tried to place mine as close to the exhaust manifold collector as possible. Exhaust gasses continue to "burn" so to speak once they've left the combustion chamber which alters the oxygen level of the spent gas and therefore the reading, so the closer you can get, the better and more accurate.

I used the Ford EDIS-4 on my car and it works great but you can use a stock points-distributor for that matter if you want. MS can run virtually any ignition system you put on your car. Of course, running a system like EDIS-4 gives you more control to digitally time your ignition to .1 degree (One-TENTH of one degree!! I LOVE it!).

Finally, there should be no problem firing 2 injectors. You could even choose whether to fire them batch (same time) or sequential (one after the other). The only thing you WILL have to do is fab up or find a Throttle Position Sensor (TPS) if you don't already have one working with your MJolt.

I bought my TBI adapters but with a little fab skills, you could make them super easy. Heck, I could've made them with the right tools (mill, lathe, drill press, etc). So I say go for it! I'll be here to help as I can from my experience. :wink:

JACK
 
You can get away without running a TPS (throttle position sensor) if you run MS-extra code on your Megasquirt. MS-extra can be configured to use the sudden increase in manifold pressure that accompanies a throttle opening to inject acceleration enrichments. This is how I have my car configured.

If you are running HS2s, I do not believe Rick Patton has an adapter for your carbs. I believe the injectors he uses for his kits are too big to work with HS2s. I have an idea for a way to adapt a stock HS2 setup for fuel injection such that the car will still look stock from a cursory glance. There has not been much interest in this, so I have but it on the back burner for now.
 
Cool. I didn't know that about the TPS/MS-extra/MAP.

As far as HS2s are concerned, it seems like you could make an adapter similar to Patton's adapter as long as you weren't concerned about look. You could make a "chunkier" version that maybe wouldn't look as nice but would still function similarly. I mean, if that adapter overhangs the carb body a bit, who cares if form follows function? I don't know though, just thinking out loud.

JACK
 
I'm running MS v.3 for injection and spark control. I use an optical trigger in the original distributor, a Ford 1.9l throttle body w/TPS. A single 44lb. injector squirts behind the throttle body but just ahead of the turbocharger. A wideband O2 sensor after the turbo is the final piece of the puzzle. I drove Bugsy with this setup from CA to LotO and back without any retune for the Rockies crossings. I averaged about 28mpg with a high of 44mpg drafting a truck for an entire tankful.
All the talk of siamesed ports falls by the wayside for me when I read the plugs.
Total control of the timing curve, acceleration enrichment, warm up enrichment, A/F ratio control, cold starts, cruising economy and raw horsepower make me a Megasquirt devotee. With a turbo and today's pump gas, I had no choice, but it has been very rewarding.
For me, the wideband O2 sensor minding the A/F ratio under all conditions is the biggest thing.
Glen Byrns
 
I agree 100%. Glen said it way more gooder but then he's been using it way longer.

Glen- A quick question if you don't mind. What percentage of authority have you given the O2 sensor for fuel corrections? I was using the "Auto-tune" feature quite a bit to get set up but then I wasn't sure how much authority to give the O2. The Megamanual suggests something around 30% I think but I was just wondering what you settled on. I've been tuning by the "SOTP" method which I'm pretty sure you did also.

JACK
 
Some questions regards the new Megasquirt:
- if I install a header with three 02 sensors, would Megasquirt be able to monitor cylinders 1 and 4? would it be able to tell the difference between when 2 and 3 were firing?
- could I install one injector for each inlet port, and have Megasquirt vary the fuel charge depending if it was going into cylinder 1 or cylinder 2? or would I need to install 4 injectors to be able to get individual fuel pulses?

Any other wisdom also welcome!

Thanks,
Doug
 
The Megasquirt doesn't have provisions for more than one O2 input. You can wire in more than one O2 sensor, but you have to include a toggle switch to switch between them, one at a time.

As for sequential fuel injection, this is a quote from the MegaManual

MegaManual said:
Sequential injection requires:

-as many injectors as you have cylinder, with one dedicated to each cylinder (i.e., not a 4 injector TBI on a 4 cylinder).
-as many injector drivers as you have cylinders,
and also requires a camshaft position sensor (a crank sensor is not adequate for a 4-stroke cycle engine).
MegaSquirt has just two injector drivers (that can handle up to ten injectors each), and no provisions for a cam sensor signal, so it would be difficult to make it into a sequential injection system.

The benefits of sequential injection are that:

-you may get slightly better mileage and lower emissions at low engine speeds,
-you can tune each cylinder's fuel amount independently (if you know how).
The effect on maximum horsepower is general negligible.
Click to expand...

So as you can see, you could do it (in theory) but it would be quite difficult for very little gain, even assuming fuel hogging.

JACK
 
If it is the outside cylinders that are prone to running lean, you can use exhaust gas temperature sensors on the outer two exhaust runners to diagnose lean running. You could also us one a them point and shoot infra red thermometers.

If you get your injectors far enough away from the intake ports, and you use a 2 into 1 manifold or a manifold with a plenum or a large balance tube, the lean cylinder condition should be no more pronounced or problematic than it is on the carb set up you have now.
 
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